# My Not so "Normal" IBIS Mountain tandem



## patineto (Oct 28, 2005)

First of all So Far I have never seeing a full suspension tandem that makes sense enough to get one of them, so until then I will ride Rigid.

Maybe some day I will make something like this with a Independent pedaling system (like the davinci, but Better) a G-boxx tranny right in the middle of the frame and some none telescopic forks.









This drawing are about 5 years old and like this one many of them are not completed (missing "Boom Tube" for example).









Since then I have learn a lot more about G-boxxes, suspension linkages and also made good contacts with geniuses like Karl Nicolai to maybe even use one of their more current set ups as oppose to just a modified planetary gear hub for a gear box.









Anyway here is somehow a Over view of my set up.

The second tandem of my life was this red IBIS that sadly prove to be a little to tall (21'x18') for MTB riding do to the long front forks that move the head tube and top tubes about 2' higher (I was not able to find a "none suspension correct fork" on a 20MM axle and really strong) with out getting one custom made,

So some of the pictures you are going to see are from the Red tandem, some from the Purple Ibis (20' x 17') that replace it.

The FUNN 20MM fork with custom welded Rim brake studs (in the back of the fork) so I can run Disc and V-brakes at the same time.









I never, ever have (in the last 25 years of riding) a brake system as dependable, powerful and well modulated as this brakes, they just stop you when ever you need to at any speed regardless of the gradient of the hill.

Yes, the hubs colors are different, so far I have four front wheel (3 with a 20MM axle, one with a normal axle, most of them build on atomlab trailpimp rims since they offer so much heat dissipation) and three rear ones, depending on the type of riding we are going to do, from "Road tyres" to Nasty as they come downhill rubber.









I also have conventional 9mm QR forks, but I just don't trust them much under extreme brake loads, plus this Surly's just bend and flex way to much under braking.









Usually I run conventional MTB handlebars.









But for the last few months I'm being test riding this beautiful hand made Titanium prototype piece .









They Fit my quadruple brake lever set up to perfection.









A less confussing view









The four lever mount on a more conventional setting, two for the rim brakes, two for the disc brakes.









I also have made a bunch of little Improvements like using a 112.5mm bottom bracket at the front to improve the Q-factor and ground and side clearance specially with the shimano 636 red pedals, By running the bash guard on the inside ring place and the chainring on the outside place but keeping the rear timing ring on the stock position (I can not run a narrower BB in the back do to the chain ring/chainstay clearances)









This E-13 bash rings are awesome to keep the timing chainrings from getting damage (I do need to decrease the diameter of the front one)

Maybe you can notice how close the lexan guard is to the frame (3mm at some places)









I also round the edges of the guard with my router to gain chainstay clearance, for the day I find a narrower bottom bracket that will fit the massive drive chains (I guess i did not have a 118 around to try it).









Ps: For the timing rings I run Onza stainless steel 36T chain rings on a 1/8" single speed chain and so far they have last a long time (rear chains are another story, they don't last more than a few thousand miles)

Here are some photos of lazzy trips, but we also have a few pretty hard core excursions on single tracks, I better not talk about..

Nice fun trips to the marin headlands are always welcome.









I really enjoy to trade the captain duty and appreciate the blowing of the hair and the company of my friends









My girlfriend is super capable and many times we do rides half and half in the captain seat (but In Step hills my big Badankadunk is to much for her)









More to come.


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## sparrow (Dec 30, 2003)

"So Far I have never seeing a full suspension tandem that makes sense enough to get one of them...."

Well, just check out a Ventana El Conquistador de Montanas some time! Super offroad worthy, the most rugged of singletrack. A real trail bike FS tandem. So many freeride/DH products (hubs, brakes, shocks, rims, tires) have come onto the scene that can do tandem duty. It really is a hey-day for off road tandems.

I've had the opportunity to ride DaVinci full suspension tandems in very rugged terrain, and the independent drive was a big problem for my Stoker and I. More pedal strikes, not fewer! The trickier the trail, the worse it has been. The Stoker just can't see obstacles coming up and make adjustments, and I can't call things out fast enough, no matter how insignificant I think it is. The traditional in-phase linked cranks allows the captain to control the Stoker's feet. That just works better for us by far.

On roads/rail trails and the like the independent drive is fine. I think you should test drive an independent drive tandem in singletrack sometime to form your own opinion. It does sound great on paper, but, oh, my Stoker's aching feet.

A decent hydraulic disc brake up front (Magura Gustav for example) renders a dual brake system unnecessary. Braking power has long since been "cured" in the tandem world. And normal 20mm thru axle forks available widely in the 100-160mm travel range seem made for tandems. Just fantastic. 

Rohloff hubs certainly are valid for tandem use. Gearbox bikes have a long way to come in the half bike world. But the Rohloff can clean up a drivetrain. It's gonna be tough to affordabley replace the regular derailer drive train any time soon. 

You sure been tinkering and thinkering on tandems a good while it would seem!


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## patineto (Oct 28, 2005)

sparrow said:


> "So Far I have never seeing a full suspension tandem that makes sense enough to get one of them...."
> 
> Well, just check out a Ventana El Conquistador de Montanas some time! Super offroad worthy, the most rugged of singletrack. A real trail bike FS tandem. So many freeride/DH products (hubs, brakes, shocks, rims, tires) have come onto the scene that can do tandem duty. It really is a hey-day for off road tandems.


To me something like this work on the Nicolai's will be a Proper rear end for a tandem and this is only focusing on single pivot point design, not even getting into VPP's like the *Legendary Canadian made BALFA's* do to the simplicity of chain tension with a concentric pivot/sprocket location and constant chain tension a simgle pivot provide.

To me a Proper rear end for a tandem is something of this caliber.









165mm rear end, Equal dish wheel with a more than 80mm in between flanges for really triangulated spokes for added rigidity, 14MM true axle (if not bigger), sliding drop outs to control wheel base, tyre size, etc, well you get the idea.









And a frame that can really take the torsional loads that get exponentially magnified on a frame as long as a tandem specially in real off road riding, not just "Seat tube" of a comun mountain bike (well maybe a little wider in diameter but that is all) with out much guzzeting and added "Real" reinforcements to overcome the incredible tandem flexing loads..









My own Nicolai M-pire, A marvelous piece of "All you can Eat" work.










> I've had the opportunity to ride DaVinci full suspension tandems in very rugged terrain, and the independent drive was a big problem for my Stoker and I. More pedal strikes, not fewer! The trickier the trail, the worse it has been. The Stoker just can't see obstacles coming up and make adjustments, and I can't call things out fast enough, no matter how insignificant I think it is. The traditional in-phase linked cranks allows the captain to control the Stoker's feet. That just works better for us by far.


Did you see my comment about *"But Better"*

Well one of the main issues as you mension is that freewheeling is great on the road (well sometimesis NOT if your cranks are much to close to the ground) so the system I have being developing (do to patent crap I can not show you) will have the option to work on "Lock down" or a freewheel (hopefully with a Lever activated at the bars), plus much less problems with ground clearance do to certain little tricks.


> On roads/rail trails and the like the independent drive is fine. I think you should test drive an independent drive tandem in singletrack sometime to form your own opinion. It does sound great on paper, but, oh, my Stoker's aching feet.


I have work on and off in the bike Industry for about 20 years from sellingm building fixing, to consulting and even designing parts and I have ridden at least 30 tandems, including a few Davinci's (love them for what they are) santana's, you name it and also many other euro brands like Nicolai's


> A decent hydraulic disc brake up front (Magura Gustav for example) renders a dual brake system unnecessary. Braking power has long since been "cured" in the tandem world.


i'm have being also racing, working and designing motorcycle parts for a few years (my main business as a designer) and I'm being around the fanciest Carbon, ceramic impregnated rotors, mono block calipers and anything else you can think off..

But, no matter what Disc brakes have a big shortcoming, they don't like to be "Drag" since the heat generated by the rubbing of the pads and the rotor can warp, glaze and also overheat the calipers and even the brake fluid (Reason why HOPE Brakes have that "Wave" finish to add surface area expose to the air to decrease heat build up).

Yes they stop like Mad but they will fade away if the over heat or suffer from different issues, if you just let them drag for to long as you know something that is necessary to scrub speed on a tandem.

Rim brakes on the other hand, can get to the point of overheating the rim to the point you can even blow a tube (Happen to me two times, serious explosions,= no Fun) reason why I use this massive rims do to the expose area air and the cooling down porpuses.

Plus disc brakes tend to Drag more than Rim brakes and the way I run my system i can engage and/or not the disc brakes so i suffer very little setback to do drag.

Yes they are way Overkill, but Back up systems are mandatory at least in my opinion


> And normal 20mm thru axle forks available widely in the 100-160mm travel range seem made for tandems. Just fantastic.


You are forgetting something really important and usually over view by most people, even designers

On a hardtail tandem the rotational pivot point for the fork is the axle of the rear wheel, for that very reason the fork need to be so sprung up to sustain the mass summatory of the two riders that is not exactly what you call Optimal or even efficient, Specially since the Captains body is about 3 feet forward from that rear hub Pivot point..

Yes funky forks like this can be run far more sprung and still have a proper suspension effect do to the geometry and the inherent ways they work, But so far they are to massive, Heavy and complex.

For example A bike from my frame Builder JP morgen from 1987.









A more current but equally strange fork at least in most eyes, but with the proper leverage and mechanical advantages to work on somethings as front heavy as a tandem.









Motocross Sidecars suffer from similar design criteria and most of them use a front suspension base on the same "Leading Link" principles .

Here are a few Examples.

Motocross Sidecar are really popular in Europe, but around here almost nobody know about them.









Do to the forward mass distribution and the clumsiness in terms of doing wheelies at command, this type of front ends is far more adequate since it reacts to the "Terrain ahead" as oppose to the "Terrain under" like a telescopic fork, plus they can run far more sprung but still active under load.









As you can see this poor things don't live a easy Life.









In fact is pretty hard.









Well tandems some how are constrain by some the same types of issues as this heavy, but not so cumbersome machines.









Maybe the most telling example, My friend Scott 160Horse power 125 pound of torque Paris dakar Racer sidecar, pretty much the nasties scariest thing you can think off. (I was invited to race it as a "Monkey" but I did not have the balls or the body to stand up for 8 hours a day with a average speed of around 100mph in the dirt.)









Then Again a full suspension Tandem is a different story since the whole frame moves "Up & Down" but you end up with this stupid 15inch high Bottom brackets, that compromise (lift up) the center of gravity and the center of mass a little to much for my taste.









Even this is just a Elongated "single" bike, nothing more.











> Rohloff hubs certainly are valid for tandem use. Gearbox bikes have a long way to come in the half bike world. But the Rohloff can clean up a drivetrain. It's gonna be tough to affordabley replace the regular derailer drive train any time soon.


They are actually not as far as you may think.

This was the version of the Nucleus gear box from Nicolai 6 years ago, using a modified Rohloff hub.









The tandem Version.









This is somehow decent, but for sure heavy









This is from last year, far more compact integrated and also cheaper.









Now this is How is done on a full downhill form, totally enclose at the drive train a master piece of design if you ask me.









Suntour is actually releasing a whole system of "Custom" build cartridge units that frame builders can get and build their own G-Boxx bikes, all this developed by Nicolai but with a more affordable "price point" focus.









And then I have a few & more current information that I can not disclose, since is not suppose to be out to the public until is being tested.



> You sure been tinkering and thinkering on tandems a good while it would seem!


I love to play with my bicycles as much as I like to ride them..

Just remenber..

I never say my ideas are "Dogmatic" or that everybody need to follow them I was just trying to present options and alternatives.

One thing is for sure the laws of Physics are the ones that will always prevail.


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## Speedub.Nate (Dec 31, 2003)

I'm sorry, I've got nothing to contribute to this conversation other than the puddle of drool on my desk that my jaw is currently resting in. Wow...


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## patineto (Oct 28, 2005)

Speedub.Nate said:


> I'm sorry, I've got nothing to contribute to this conversation other than the puddle of drool on my desk that my jaw is currently resting in. Wow...


Oh Nate I have read your Postings, you are a really smart fellow with a really open mind, so I will not be ashame at all if I was you..

So far I'm focusing way to much on some of my Moto work, but i will love to start the tandem project soon since is so much to test, play and hopefully improve.

for now check the *Suntour X-OFF V-BOXX * system.

Or even better the *G-boxx.org site* for some inspiration. Everything you need to blow your brain thinking about the possibilities is there, tons of Info, measurements, photos history, anything you want.


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## patineto (Oct 28, 2005)

Oh you guys are going to get a Kick out of this.









For years people keep telling me certain things can not be done and I just love to prove them Wrong.


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## patineto (Oct 28, 2005)

this is a really great write up on the evolution of the *"G-Boxx" (gearbox bikes)* with tons of links.

Enjoy,..

Specially you mister Nate since you are already a Planetary gear freak.


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## patineto (Oct 28, 2005)

on the same site i found a bunch of *Videos from Eurobike 2007* including Nicolai's, bergamont, and G-boxx bikes.

enjoy, they are all single bikes but at least you can gater ideas of the future for tandem use.


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## TandemNut (Mar 12, 2004)

Very interesting. Some questions for you:
What's the advantage of the G-Boxx over the Rohloff? 
What's the disadvantage?
What sort of disc brakes are you using on your tandem, and what size rotors?
What sort of circumstances were you riding the tandem in when you experienced the brake fade from the discs?

With bicycles, for the masses, it's all about weight. While I agree that a leading-link (or trailing-link) fork is more terrain-responsive, I don't see how it can be built at or near the same weight as a telescopic fork. Lawill built one several years ago, and it seemd to get good reviews from the magazine testers, but the forks eventually went away. Pace seems to have done something similar recently as well.

When we spec parts for tandems, we're borrowing from DH, FR, sometimes XC, but the parts have been designed to work at the minimal weight possible. 
Of course, as I get older, I appreciate this fact, since more weight equals more effort for a given return.
Your ideas are very interesting. Please keep posting them!


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## patineto (Oct 28, 2005)

BigNut said:


> Very interesting. Some questions for you:


Any time you want senor..



> What's the advantage of the G-Boxx over the Rohloff?


Most of The early G-Boxxes, (well at least the Nicolai's) were Rohloff Hubs "Incase" into a structure to hold them, using the disc brake side to mounts the "input" chainring coming from the cranks

Stuff like this was comun place.









Old Nucleon from 2004 i believe.









They Require tension adjustments for everything from the G-boxx to the cranks, to the swingarm.









This are far more current designs, with a Gearbox specifically made for the G-boxx porpuse.

Kind of difficult to see, but in the bottom part is a outline of the new type gearbox from Nicolai.









Cad drawing (Incomplete) from the Nicolai system.









Super Compact, seal, lower and much lighter.









Still puzzles me, (If they make their own gearbox and they can do whatever they want) why they insist to run the drive chain to the wheel on the left side, making the choice of brake calipers more complicated.

Proprietary, corporate, exclusive crap..!?!?.









Here are a few pictures of other G-Boxx bikes and systems, some for sure more sound than others.


















Yeap, heavy.









Inclose gearbox









Complex chainline with to much slack and friction plus single member swingarms usually end up being heavier and more flexible, in short Triangulation is key.



























the "Auto-matic" concept









I think I understand how it works, but still is to prone to get dirty and be affected by the elements.









Gt concept, very interesting.









You can always count with Dave and the Guys from E-13 to come out with something cool.


















I don't remember who made this "Derreileur on a box" (Hayes I think, "pete speed" maybe) but is kind of Lamme









The Input sprocket slides on the "Pedal shaft" changing gears just by pressing on the chain sideways.









Can you say Primitive, plus the gear rathios are somehow limited.









mounted it on a bike "Open"











> What's the disadvantage?


well as you can see above, many of the early attemps were kind of Clumssy, complex and also much to wide (wider than a 135mm hub)

On the good side with the G-boxx's, the super heavy Rohloff hub (build into a wheel) is not mounted at the end of the rear swingarm, making the suspension work a lot better (on hard tails is not such a big deal, the bike is just "Tail heavy")

Currentlly Nicolai and their somehow partner Suntour (the design was suppose to be sold to Truvative, but I don't know what happen) are making specific "tranny's" that are far more compact, simpler, narrower for better clearance and Q-factor and hopefully even more efficient and reliable and Much Cheaper.

Here are some pictures of what Sr Suntour is offering.









Notice how the pre-made frame connect to the G-boxx with Bolts (not welded) for easy of manufacturing and liberty of design.









The UK Nicolai site even has a *Bunch of Information on the new G-boxx's* they make,

*Click HERE for the "Animation" of the inner workings*


> What sort of disc brakes are you using on your tandem, and what size rotors?


Old school HOPE with four piston calipers and "Radial" master cylinders on a Inclose system (no air chamber just fluid) and 200mm rotors

Actually that is how I can make it work.

the brake lever are "Flip" (you can not do that with most conventional "expansion chamber types" except if the have a detachable reservoir like the new Oro's from Formula that can be flip 









The only think I need to activate them is twist that little silver knob, yes when you are moving.









This is how the brake lever work.

Rim brakes









Disc brakes









The two of them at ones.











> What sort of circumstances were you riding the tandem in when you experienced the brake fade from the discs?


So far Never on my tandem since I run mainly on the rim brakes.

But I have work, see and experience more than one disc "Cook" & "burn", over heat to the point of warping, glaze brake pads, and rotors, voil (becomes even more "hydrofilling", a.k.a. water and air contaminate the fluid and make it easier to compress and losee eficiency) brake fluid (even using Motorex 5.1 grade the best fluid available so far) mostlly on downhill and heavy loaded touring single bicycles & tandems and also motorcycles (remember that motos, use the compression of the engine for braking too) 
But even then a brake that is being drag by mistake (placing your feet on the rear brake, even a little) or on porpuse trying to slow down a heavy bike is going to fade if is not sufficient cooling to keep it happy.

Yes usually a larger rotor provide more material to dissipate the heat, but they also become heavier starting (making it worst) to affect the way the bike handle do to the gyroscopic forces, in that case rotors with aluminum "Floating" carriors are best since they are lighter (don't need to carry the heavy steel core) the aluminum is a excellent "Heat sink" and also they "float" making the rotor more capable to adapt to temperature changes and other factors like caliper alignment and twisting..

For example My KTM 950ADV does it all the time in the rear caliper, mostly to a design mistake of using a dual piston system with the pistons located only on one side (do to clearance with the spokes) and slider rods that get stuck and or dirty and contaminated.











> With bicycles, for the masses, it's all about weight.


Oh yeah that I understand that all to well, but many times is more "Perception" than reality..

For example my dear friend and frame builder Jp Morgen place 3th place at the napa world cup (on his age group) on a 34 pound bike when the rest of the racer were on 20pounders.

On this very frame, this days set up as a commuter.









How you may ask, well even if the suspension design is obsolete, he can still climp and put power to the ground in a more efficient way than the hardtail, and then because he is a freaking Animal too..

In any case I agree with you.

Is always a compromise of how much is the least you need, longetive, practicality ,cost, easy to repair and the famous "SPS" (Small Pinus Syndrome) and the more current "Bling"



> While I agree that a leading-link (or trailing-link) fork is more terrain-responsive, I don't see how it can be built at or near the same weight as a telescopic fork.
> Lawill built one several years ago, and it seemd to get good reviews from the magazine testers,


You are Right again, at least so far, here are a few examples of the early lawill's and other funky forks that never really got develop, I believe do to the lack of market response (no sales = no money = no farder development).

4130 Steel lawill made my Kosman's in san francisco for Mert himself in about 1991 (I used to have one, but broke in half because I (well many of my costumer try it too) keep climping things like sidewalks and obstacles with out even lifting the front wheel next to a "Rebound" from Monolith maybe the most complex, well made but useless fork ever.









Then (1994) control tech purchase the rights from Mert and everything was long gone, well they made two more version but they did not work that well, plus telescopic forks keep getting better and better..









Also The lawill's have a limitation on the amount of travel that can be achive out of them do to the geometry and the head angle changes (not much more than 4 inches)

One of them on my own bikes IBIS SS (I have two more of the Control tech and I will love to find one of the steel ones, but most of them broke near the headstock.









This IRD "antidive" work really well and were not affected by the brake usage, very big deal on a bike like a tandem.









yeah strange and heavy, but very tandem "proper"









I personally thing "Telelever" type have a lots of potencial (Bmw owns most of the patents, even if they "Borrow" them from a English designer), specially on heavy (tons of mass at the front end) bikes like tandems do to the rigidity, antidive features, simplisity of manufacture, tolerance to "Play" and worn out parts.

but they are not as reactive as more conventional type fork,, mainly do to the "Sprung mass" but mostlly do to the lack of development of the technology.









I know this looks strange, Fugly and super complex, but makes a lot of sense, well the basic concept that is if somebody made it into a less "Gothic" dual sided version.











> but the forks eventually went away. Pace seems to have done something similar recently as well.


well selling Telescopic fork is a no brainier, everybody knows them and can see how they work, since they just move up and down, you know the usual "Pushing down on the forks" test

Plus as we all know they develop a lot of friction on the seals and slider, something that on a motorcycle is less noticiable do to the weight and also the fact that you don't need to pedal it.

You can call me crazy if you like, but I think bicycle forks can be much better, specially if they depart from the conventional ways.


> When we spec parts for tandems, we're borrowing from DH, FR, sometimes XC, but the parts have been designed to work at the minimal weight possible.
> Of course, as I get older, I appreciate this fact, since more weight equals more effort for a given return.


Oh I get that big time and I totally agree,..

I just don't think the current market is willing to accept radical departures from the obvious and that is the main reason why "funky stuff" just does not sell, get developed, etc, plus make "Well made stuff" cost a lot of money to make do to the manufacturing standard and materials require and leave very little revenue for all the Money steps the market require.



> Your ideas are very interesting. Please keep posting them!


Thanks senor for taking the time to respond in such a way we can all learn from it..

Please bring you experience also, since I'm sure you have many.

Ps: I love the way you run your Shop, very honest, Very sound, muy profesional


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## patineto (Oct 28, 2005)

Since my last posting I'm being in contact with Karl Nicolai (the head of Nicolai Bicycles and the G-Boxx.org movement) and we have talk about the application for their new gear box concept for tandem use..

Everything is going well, I have the passwords for all the "Secret information" and CAD files, so hopefully soon I will have some basic drawings and "out of the box" proposals to share.

Think Belt Drives everywhere, 3' maybe 4' more inches of ground (rock, stump's ) clearance than a stock full suspension tandem with out being any higher of the ground.

Exiting times for sure.


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## sparrow (Dec 30, 2003)

How can you get better clearance than existing designs, seems the bb/crank is still the limiting factor? I suppose that an elevated boomtube and elevated syncro chain (or belt) can be of some help, but the boomtube is generally not the limiting factor in clearance for our offroad tandem use, in fact, it is a nice rail to grind on! Sketches soon!


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## patineto (Oct 28, 2005)

sparrow said:


> How can you get better clearance than existing designs, seems the bb/crank is still the limiting factor? I suppose that an elevated boomtube and elevated syncro chain (or belt) can be of some help, but the boomtube is generally not the limiting factor in clearance for our offroad tandem use, in fact, it is a nice rail to grind on! Sketches soon!


Well senor is kind of easy actually.

If the Timing Chain is not going from the front BB to the rear one, but goes into the gearbox that is located on a very different place, (much higher) you already gain all that distance wasted by the chain.

Plus since the gearbox can become a structural member the Boom tube maybe does not even need to be Horizontal to the ground anymore, but somehow slop down from the tranny box to the front B.B.

I guess I did not specified, the Front "ring" still somehow low, (I Very seldom hit the timing ring, but I always touch the chain) then again the belts (less diameter PUlley) can be run smaller with out much detriment in terms of torque transmission.

the problem at the moment is actually to convince the "Carbon belt" guys to make us some long belts and "Rings" (PUlleys compatible with Tandems and also 110bcd cranks, since so far they only make them in 94bcd), then again I'm working on that from a few fronts, even the personal since I have a dear friend that Lives in Golden colorado and he happen to be friends with one of the people that work at the company.


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## patineto (Oct 28, 2005)

Some pictures Of my JP Morgen Hydrolic suspension stem.









Yes I need to Cut the Steering on the fork, but since I used forks with many stems and even bikes I just don't want too.









JP is a really good friend of mine from San francisco, but even then my two JP stems I end up getting from E-bay since he only made a few in the early 90's (1992/1994 for this model, 1988/1990 a different less evolve model) and he does not have any anymore.









They are not the "Perfect suspension system" for sure.









But I still prefer this Stem than a fork that bounces up and down like a pogo stick, at least on the tandem or a "vintage" bike that was not design for a suspension fork.









Ready to ride.


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## TandemNut (Mar 12, 2004)

Patineto,
You have some great ideas for tandems. 
When was the last time you rode a current full-suspension tandem?
I ask because I suspect some of the issues you experience with your tandem
aren't as much of a problem with more current design. 
2" - 4" of additional bb height can make a huge difference in what obstacles you
can ride. 
If you're ever in the Southeast US, stop by and take some of our demos out for a 
spin; I think you'll be surprised at how much difference there is in the geometry.
Now, as for bb height and boom tube clearance, here's the best way to make a
significant change:
Move the rear wheel under the stoker. The stoker cranks would be centered on the rear hub. If you used an internal hub like a Rohloff, the 
stoker cranks would be tied directly into the rear hub. Captain's timing chain would
be tied to the stoker cranks, or the hub, or both. Swingarm location would be
somewhere near the middle of a current tandem frame's boom tube.
Given the drastically shortened wheelbase, I submit that this sort of design would 
gain far more maneuverabilty off-road than any other approach.
I'd sketch something out, but I dont' have one of those fancy sketchy programs.
I saw a similar setup in a picture of a cheap asian commuter tandem a few years ago.


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## patineto (Oct 28, 2005)

BigNut said:


> Patineto,
> You have some great ideas for tandems.


A professor of mine used to Say..

"common Sense is the least common of the senses"

I just try to exercise this "Muscle" as much as I can.



> When was the last time you rode a current full-suspension tandem?


A brand new top of the line Ventana two weeks ago.

You are right, they are far better than the old stuff, but I guess I'm just kind of "Particular"


> I ask because I suspect some of the issues you experience with your tandem
> aren't as much of a problem with more current design.


The way I see it Tandem evolution, is somehow parallel to computer Evolution, it gets better and better in quantum leaps.

So if I'm going to make one, I'm going to try to make it as cutting edge as possible, since no matter what suspension design , structures and materials keep evolving in such a incredible rate..


> 2" - 4" of additional bb height can make a huge difference in what obstacles you
> can ride.


After riding and racing big, tall and heavy motorcycles in the desert (my KTm 950Adventure for example) you become very aware of the importance of keeping the center of gravity as low as possible.

Plus motorcycle frames flex very little compare to bicycle frames, specially tandems, since on pedal bikes the weight is so critical and usually more material equal more mass.

Unless you go to a structure like this









well a little to Extreme, JP Morgen will be my frame Builder, he is Incredible if not a little to crazy brilliant sometimes.









Trellis structures are extremely rigid and actually not that much heavier than big wide tubes, plus you can still keep them narrow and the pivot point supported on two sides.










> If you're ever in the Southeast US, stop by and take some of our demos out for a
> spin;


Thanks for the offer senor, I have so much respect for you guys, I really like the way you do business, Because is easy to see you don't work for the money as much as you work for the passion..



> I think you'll be surprised at how much difference there is in the geometry.
> Now,


That part I'm still trying to figure out, wheel base compactness, vs toptube room is something difficult to achieve, plus I need to figure out the kind of fork I'm going to Build before I can select the head angle.



> as for bb height and boom tube clearance, here's the best way to make a
> significant change:


I have a somehow different approach to BB Height, well not just Height but Ground and specially "lean angle clearance"

The basis of the theory is to diminish the Q-factor as much as possible, but for that you need to run really narrow BB, tight chainlines, low Q factor cranks and somehow narrower pedals, Old school Road bike or MTB cranks with square taper if necessary running on 68mm shells and sub110mm bottom brackets as oppose to "Exo" this and that wide cranks.

Keeping that i mind I don't think the Nicolai G-boxx is going to work since they are so freaking wide to accommodate all the gears inside (well not as much on the future versions, but they are 2 maybe even 4 years away at the moment)

The Nicolai wonderbox, well not the newer one that is a little narrower.









The suntour version.









So I'm being exploring the "Derreiluer on a Box" concept since they can be made far narrower. 









Using a "Cartridge" like this that becomes part fo the frame, plus you can place if "Horizontally" on the tandem and safe even more space









On this Topic *Alex BCD is the man* the simplicity and logical approach to his work is stellar.









Then again call me weird but I like really long cranks on tandems (180mm front, 175mm rear if possible) do to the torque they provide for steep climbs since standing at ones is kind of complicated


> Move the rear wheel under the stoker. The stoker cranks would be centered on the rear hub.


Oh yeah I totally agree, I elaborate a little down on this post.



> If you used an internal hub like a Rohloff, the
> stoker cranks would be tied directly into the rear hub.


Sadly I think the gaps on a G-boxx are a little to spread out for tandem usage, yes they provide a 680 degrees of spread, but the jumps in between gears are few and far between.

So I may run a "front Gear box" as a reduction gear and then a Rohloff hub in the back, Yeah pretty much like a heavy truck is run with a multitude of very progressive gear rathios to optimize power delivery and drive train stress.



> Captain's timing chain would
> be tied to the stoker cranks, or the hub, or both.


Well I think I figure out a much better way than the davinci system (I still need to make some prototypes but the concept is sound) so I'm going to try to run a "independent pedaling system" with a lock out feature, but don't worry it will be very narrow and high to avoid any ground contact.



> Swingarm location would be
> somewhere near the middle of a current tandem frame's boom tube.
> Given the drastically shortened wheelbase, I submit that this sort of design would
> gain far more maneuverabilty off-road than any other approach.


Oh yeah

So far I'm in love with the Lahar's aproach to rear suspension (actually the whole bike, this guy is smart, very smart.)









The wheel start her travel as close as possible to the Bottom bracket and moving upwards and away but also keeping the wheel base somehow constant, then you can have a very progressive rocker arm system to keep the travel under control, maybe even a "Low rider" version for normal usage and then a "tall setting" for Rock gardens and nasty trails.









The way Lahar's arrange the Speedhub is Brilliant.









Chain running on the conventional side and everything, again we have a lot of brilliant comrades among us.









Alex BCD takes a similar approach, high swingarm pivots (well his 2x4 is even crazier).











> I'd sketch something out, but I dont' have one of those fancy sketchy programs.
> I saw a similar setup in a picture of a cheap asian commuter tandem a few years ago.


Hey maybe I can teach you how to draw using pens and paper.


----------



## DrewM (Jan 8, 2007)

I had a few thoughts but after re-reading the thread a couple of times you guys are WAY out there so I went back to day dreaming and came up with a couple thoughts:

Re. Putting the stoker right over the rear wheel. ("Move the rear wheel under the stoker. The stoker cranks would be centered on the rear hub. If you used an internal hub like a Rohloff, the
stoker cranks would be tied directly into the rear hub.")

Why not mount your gear box centrally in the frame between the stoker and captain (for as low and balanced center of gravity as possible) and use a threaded crank/freewheel like a lot of mod trials bikes use? http://www.trials-uk.co.uk/product.aspx?productid=1375#. You could use a custom 24mm rear hub/thru axle design and actually use the cranks (with a 24mm spindle) as the axle (I like designs that may sound complex but actually eliminate parts). By move the freewheel onto the stokers crank and having a seperate freewheel for the captain their efforts would essentially be unhinged?

The only thing that would be weird is you would have to have 1 chain coming from the stockers cranks/freewheel to the gear box and another chain going from a fixed cog on the rear hub to the gear box (essentially you would run one fixed chain from the gear box to the rear hub and the stocker and captain would each have a freewheeling chain?

Hopefully that is relatively clear... it works in my mind but I can't draw.

Re. un-coupling the riders. I have often wondered if an easier fix re. un-coupling two riders would actually be to use a system like rotor cranks: http://www.rotorusa.com/s1-rs4xrd2.shtml. Instead of relying on the cranks to remove the deadspot in the pedal stroke it would allow the captain and stoker SOME ability to pedal naturally (movement in the crankarm compensating for an imperfect pedal stroke) without much added complexity.

...

I like your handlebar

...

Why not move one set of brakes to the stokers position? Presumably when you are in a riding situation that requires both sets of brakes to slow the bike you can communicate with the stoker to also engage their brakes?

Just a thought.

...

I ran into a fellow about 7-8 years ago with a disc brake equipped tandem that was really neat. He was running a custom double crown (a Hannebrink I think?) that had disc mounts on both sides of the fork and a custom hub with rotor mounts on each side

He was using Hayes champagnes with a line splitter so one lever could activate both calipers.

You could easily get someone to weld an additional IS mount onto your FUNN fork and probably due away with the need to V-brakes at all, which would also remove any issues with heat affecting the tube/tire.

-D


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## DrewM (Jan 8, 2007)

Re. Close enough gear ratios:

Pete-speed (bought by Hayes but they never did anything with it) is really simple and pretty light and if you made a lightweight carbon or plastic fairing for it it would be relatively impervious to the elements.

When I first saw it:

https://patineto.smugmug.com/photos/37951881-L.jpg

I wondered if there wasn't a way to put multiple (2? 3?) cogs the axle currently containing 1 so that you could significantly increase the available gear ratios.


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## sparrow (Dec 30, 2003)

It seems to me ages ago Dirt Rag had a review of a tandem that had the stoker out behind the rear wheel. It was ages ago, before suspension and disc brakes. It looked alot like one of the gaining vogue "transport" bikes with the long wheelbase and built into the frame dec/rack set ups.

But it had a short wheelbase (in tandem terms) could clear lots of obstacles thanks to the shorter boomtube/shorter wheelbase, and had the bonus of the stoker's ability to really pull back and assist wheelies/unweighting the front wheel for step ups/ledges, etc.


----------



## patineto (Oct 28, 2005)

This first few drawings are base on the G-boxx 2 prinsiple.

Here is the overall shape of the G-boxx made by Nicolai and the require mounting points.









Okay here are some Super dupper mega cheesy Ideograms showing a few lay out alternatives, nothing serius so far but they help visualize how everything fits..

ps: A really good trick. is to find a picture of a frame (or whatever you are drawing) that somehow fits you needs, print a bunch of "Water down" copies (I when to far on a few of them) so you can see what you are drawing on top of it.

The front and rear cranks feed power into the Input shaft of the gearbox (forward upper axle near the rear wheel) then the gear box output shaft is mounted concentrically to the swingarm pivot ("sprocket" circle above the rear bottom bracket), well the swingarm is mounted to the gearbox output shaft structure (is design that way) so no chain tensioner is require plus is not chain growth or any of that stuff that can affect suspension performance.









Similar but in this case the Gearbox is mounted more Horizontal (does not need to be that angle up unless the shock or something need to share the same space









Similar but this time the tranny is set up really low (Tilt downwards) and will diminish ground clearance for the timing chain.









This next two feature a "Derreileur in the Box" 9speed gearbox, since is mounted almost horizontally and farder apart than a "Box" for a single bike, maybe you don't need the front sliding main gear.

As you can see the rocker arm, shock etc will be house near the rear bottom bracket in a heavily triangulated trellis structure, the Bottom brackets can be very narrow for "Lean angle clearance"

Actually is not really a reason why the front timing chain can not be run right at the very center of the frame (not on the side like you typical tandem) you just need a "Split Bottom bracket" and two external supports on ether side of the BB to hold the cranks stiff.

In a ideal world a High performance Belt of really narrow diameter (but really wide like on a Volumetric Compressor belt on a dragster or even a harley moto) and you will have a "timing chain" that is almost as tall as the Eccentric Bottom bracket Adjuster. giving you tons of ground clearance yes then you can run a little lower Bottom bracket (since you have the clearance) making the bike far more stable and less nervous under heavy load, plus you "baby makers' will be at less risk with out making the frame any less rigid.









The problem with all this systems so far (if run as single speed in the back) is that they may provide sufficient gear range, but the gaps are so massive and so far apart will be almost impossible to use on a tandem application were smooth shitting transmissions are paramount.









This one will have a Whole "27 speed Drivetrain" (even 30speeds why not) with a triple chainring and a 9 speed in the back Just all mounted inside the frame members to diminish the chance of damage but not much else.

yes I know the rear part of the frame need more space in between the members for better structural triangulation.









I'm working on more detail drawings and I will show them when they start to make more sense.

Sorry for the Horrible drawings, I promise they will get better and better as the design progress.


----------



## patineto (Oct 28, 2005)

DrewM said:


> I had a few thoughts but after re-reading the thread a couple of times you guys are WAY out there so I went back to day dreaming and came up with a couple thoughts:


Drew many times being far away from a problem is the best way to solve it,,

so don't be shy and shimme in any time..


> Re. Putting the stoker right over the rear wheel. ("*Move the rear wheel under the stoker*. The stoker cranks would be centered on the rear hub. If you used an internal hub like a Rohloff, the
> stoker cranks would be tied directly into the rear hub.")


Oh man I did get that from BigNut comment, You see you already help bunch.

that is such a awesome concept.

Man BigNut you are Missing a Nut that is freaking crazy cool (i think I have seeing that yellow bike you mention somewhere

I do have a few concern about it.

The Seat of the passenger will need to be really high, well as far as the wheel will travel plus a space for the attachment bracket for the seat.

Then again if the seat was place Just Back enough of were the wheel travel, you can place it much lower since is not at the ":Crest" of the wheel ..

Maybe the center of mas will be mess up and the captain will fel like is carring a Big ^ss Cow

Also the if you attach the rear pedals to the rear axle your feet will move with the rear wheel, No bueno for sure at least in a full suspension bike..

Then again you can build a "Split" mount for the back cranks and run a pair of chains (belts whatever) to a "Syncronizer axle", yeah heavy complicated and also very wide bad in terms of ergonomics (pedaling like you are on a horse) and lean angle clearance.

Man I can even Type, I just want to drop the laptop and get to draw a few schematics about that brilliant concept


----------



## patineto (Oct 28, 2005)

DrewM said:


> Why not mount your gear box centrally in the frame between the stoker and captain (for as low and balanced center of gravity as possible) and use a threaded crank/freewheel like a lot of mod trials bikes use?


Shhhhhhhh, don't tell my secret to everybody.

Yes my Plan is to have the freewheel ratchet at the cranks, that way you save the the space occupied by the stupid freewheels on the Davinci tandems in the middle of the frame (that look like crap , scratch and grease up your legs and require to still run the cranks on the left (much less choices)

I already have a pair of White industries freewheels with multi-ratchet contacts, really to weld up to a chainring carrier, but I'm waiting since I'm in love with belts.

As far as i know is a few problems with Trials cranks, first they are crazy expensive, most of them are really wide (to give better contact Grip I guess , like a bash plate) the Q factor is also horrible for that very same reason, plus most of them are made like the old Caramba cranks, you know CNC but not really cold forged or anything structurally sound.

But the main issue is that they only come on 170mm length for the normal ones and then 160mm for the "Mod" (Modified style) Bikes


> *Try-All CNC ISIS Cranks*
> . You could use a custom 24mm rear hub/thru axle design and actually use the cranks (with a 24mm spindle) as the axle (I like designs that may sound complex but actually eliminate parts)


You see Drew you are bringing a whole new spectrum of possibilities to this project, I can not thank you enough.

First this is the first time I see this cranks in 175mm plus the ones on the link are not as expensive as usual (well they are 90english pounds)

About the axle, maybe I need to take a trip to the BMX store and see how the new stuff works, I'm just not that familiar..

Your inside on the topic is super helpful



> . By move the freewheel onto the stokers crank and having a seperate freewheel for the captain their efforts would essentially be unhinged?


"Independent pedaling" is a great option for the road, or easy trails but it will Kill you on tight trails since the stocker has no idea were they are going, so it need to be able to "Lock/unlock" Optimally with a "lever actuator" from the handlebar.


> The only thing that would be weird is you would have to have 1 chain coming from the stockers cranks/freewheel to the gear box and another chain going from a fixed cog on the rear hub to the gear box (essentially you would run one fixed chain from the gear box to the rear hub and the stocker and captain would each have a freewheeling chain?


that part I think I have better figure out, or maybe i just not understand you that well.

I promise to re-read it a few times until I'm sure i understand.


> Hopefully that is relatively clear... it works in my mind but I can't draw.


Well maybe i teach you how to draw just to thank you for your participation, I did that for years at my university I can even teach a monkey, hell i teach a few for sure.



> Re. un-coupling the riders. I have often wondered if an easier fix re. un-coupling two riders would actually be to use a system like rotor cranks:
> *Rotor RS4X Road Double Steel*
> Instead of relying on the cranks to remove the deadspot in the pedal stroke it would allow the captain and stoker SOME ability to pedal naturally (movement in the crankarm compensating for an imperfect pedal stroke) without much added complexity.


Not exactly cheap at $693.00 shipped per Two, But you got me thinking again..



> I like your handlebar


I'm still getting use to them, they are super light, stiff and really pretty but the ergos of a mountain bike bar work pretty well for Mountainbiking....


> Why not move one set of brakes to the stokers position? Presumably when you are in a riding situation that requires both sets of brakes to slow the bike you can communicate with the stoker to also engage their brakes?
> 
> Just a thought.


No way in hell..

If the stocker had brakes (many times i ride on the back seat) you will not go anywhere because they will keep trying to slow the bike down all the time..

Tandems are very "Monarchic" in fact is almost like a Military dictatorial state, again I don't mind being the slave.


> ...
> 
> I ran into a fellow about 7-8 years ago with a disc brake equipped tandem that was really neat. He was running a custom double crown (a *Hannebrink* I think?) that had disc mounts on both sides of the fork and a custom hub with rotor mounts on each side.


key word *Hannebrink* but yes BigNut sell some awesome forks they modified for tandem assuage.

One of the current rotors is more than sufficient to *stop you*, the problem is to "Slow you down"


> He was using Hayes champagnes with a line splitter so one lever could activate both calipers.
> 
> 
> > I have seeing the splitters before , the problem with them is that the master cylinder needs to have twice the capacity to move double the amount of fluid for them to work correctly (simple Pascal laws of hydrolics) and most people overlook that issue.
> ...


If i can only chose one, I take the rim brakes over the Disc brakes at least for the tandem with the Atomlab rims. (i have 19 bikes at the moment, all the current ones [9 of them] running on HOPE Disc brakes)

We just came back from a somehow step tandem ride in the rain Marin headlands and is just amazing how fast this brakes will bring you to a stop, it almost generate G-forces and everything they Rule..

Thanks again for your dedication, you have help this post so much with your concerns and ideas..

I really like this type of topics when you are discussing "Theoretical" and almost Philosophical arguments as oppose to the usual "How much Bling I can get for my bike"

Now were is Nate when we need him..!?!?!


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## patineto (Oct 28, 2005)

DrewM said:


> Re. Close enough gear ratios:
> 
> Pete-speed (bought by Hayes but they never did anything with it) is really simple and pretty light and if you made a lightweight carbon or plastic fairing for it it would be relatively impervious to the elements.


Yeah that Kind of sucks..

Do you know were I can find one..

I have never see on for sale, well i don't go to Interbike anymore but I don't think is available.


> When I first saw it:
> 
> 
> 
> ...


I don't think on this specific system but if you make your own maybe is possible , The distance in between the axles needs to be much longer so the chain has room to "Flex and bend"


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## patineto (Oct 28, 2005)

sparrow said:


> It seems to me ages ago Dirt Rag had a review of a tandem that had the stoker out behind the rear wheel. It was ages ago, before suspension and disc brakes. It looked alot like one of the gaining vogue "transport" bikes with the long wheelbase and built into the frame dec/rack set ups.
> 
> But it had a short wheelbase (in tandem terms) could clear lots of obstacles thanks to the shorter boomtube/shorter wheelbase, and had the bonus of the stoker's ability to really pull back and assist wheelies/unweighting the front wheel for step ups/ledges, etc.


thanks senor I need to search for that article, oviuslly if anybody has it or know were it is I will be really happy.

I can just Imagine this "Tandem Unicycle" with the weight of the two riders working as a Teeter-Totter to chance the balance of the whole machine.

I get to work on the drawings, the minute my head stop spinning with some many ideas.

Thanks again for all your comments and ideas senor Sparrow.


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## TandemNut (Mar 12, 2004)

After several years of maintaining a fleet of demo tandems, I'm a firm believer that the simplest solution is the best solution, especially for drivetrain wear parts. While the more complicated systems offer benefits, we find it them more succeptible to chain suck, and more work to maintain. The best option is the fewest chains, and the fewest moving parts.
I look for solutions from what's readily available, for the most part, because development and testing of new designs is expensive. Thus, I look for ways to adapt currently available parts for tandem use (hey, that's the tandem mtb way by necessity). However, it's very cool to see folks thinking beyond the current constraints and looking for completely different approaches to a problem.

The derailleur in a box system could be combined with something like Schlumpf's cranks http://www.schlumpf.ch/sd_engl.htm, which would offer the dual-range setup. Combining this with either the DIAB or Rohloff drastically broadens the gear range.

I have an ATC fork with dual disc mounts. I aslo have a right-side mechanical disc brake from Winzip. I used a cable splitter from QBP to a single lever. The WInzips have great heat dissipation abilities, but not great stopping power in their current form (too much lever pull). The result was that the dual WInzip brake setup, while very cool, didn't actually feel much stronger than a single Magura Gustav, or even an Avid BB7. I suspect it would have fantastic capabilities for long descents, but it wasn't practical in everyday use. The weight penalty wasn't offset by performance gains.
However, the right-side disc bracket is available for ATC forks by custom order. I also have a source for dual-disc hubs in 20mm axle version.


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## TandemNut (Mar 12, 2004)

Middleburn offers crank arms in 165mm - 180mm that are adaptable to trials use, and with a lifetime warranty.

The Whyte front fork was a version of BMW's Paralever suspension. I think that sort of system would offer some promise, as it certainly works on BMW's. Is Whyte still around?


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## sparrow (Dec 30, 2003)

I've "googled" all over for it, and can't find anything on that "short wheelbase tandem". I know it was photographed in an ATB magazine in the past decade! It was a hardtail, and that'd could be a good way to start off to work out drive train design. It would need a series of skinny tubes, ala. "spaceframe" to park the rear wheel in front of the stoker. It really could be a revolutionary system. The Stoker would not necessarily need to be cantilevered waaaaay behind the rear wheel, but some shortening of the wheelbase could work fantastic for an offroad tandem.

http://www.konaworld.com/08_ute_w.htm

is one of the new trend in utility bikes, and you can get a vision of how that short wheelbase tandem looked.


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## sparrow (Dec 30, 2003)

More short wheelbase shots, just to get an idea. Maybe a gearbox mounted mid-frame:

https://www.wooljersey.com/gallery/v/maasland/1979_Bob_Jackson_SWB_Tandem/Rideau_Lakes_1984.jpg.html

https://www.wooljersey.com/gallery/v/maasland/1979_Bob_Jackson_SWB_Tandem/Reassembly_1985.jpg.html

https://myweb.tiscali.co.uk/trykit/...heelbase Tandem_files/Claud Butler Tandem.jpg

https://cycletrack.blogspot.com/2007/05/tandem.html

https://www.singletrackworld.com/ar...43&PHPSESSID=f07f7a1f88f0b9f94ee1cf545c4da238

Well, sorry for the linkage, but something like BigNutt suggested. Run the stoker behind, or directly over the rear wheel. Put the gearbox, derailer system, or Rohloff type transmission mid-frame, some sorta 4-5" travel rear suspension. Hmmm, radically shorter wheelbase does seem to have potential to improve offroad tandem riding.

That said, our current 5" travel Ventana El Conquistador de Montanas is a pretty fine handling bike. The new platform valved suspension available for front and rear are fantastic. New FR/DH application brakes (ie Gustav hydros), 20mm thru axle front wheels and the oversize telescopic forks with very adustable damping for compression at different stages of the stroke are a powerful new set of tools to use for offroad tandem riding.

No need to wait for linkage forks to be designed and produced for offroad tandem use, no need to wait on gearbox drives and further tweaks to rear suspension design for the "ideal" FS off road tandem.


----------



## patineto (Oct 28, 2005)

sparrow said:


> I've "googled" all over for it, and can't find anything on that "short wheelbase tandem". I know it was photographed in an ATB magazine in the past decade! It was a hardtail, and that'd could be a good way to start off to work out drive train design. It would need a series of skinny tubes, ala. "spaceframe" to park the rear wheel in front of the stoker. It really could be a revolutionary system. The Stoker would not necessarily need to be cantilevered waaaaay behind the rear wheel, but some shortening of the wheelbase could work fantastic for an offroad tandem.


If the tandem was a hardtail will be somehow easy to acomplish.

a massive 14mm true axle, extended to the point the cranks can be mounted in a very rigid fashion to the ends of it and then a way to transmit the force of the two separate cranks into a "junction box"

Will be simple but not as fun to figure out as a full bouncy bouncy monster of the dirt.


> http://www.konaworld.com/08_ute_w.htm
> 
> is one of the new trend in utility bikes, and you can get a vision of how that short wheelbase tandem looked.


Oh yeah my friends Nate and paul run the distribution for the Extracycle and I have the chance to ride a few of them before even fully loaded.

Actually that was my fear, they do feel very unstable when you have somebody heavy in the back of the wheel (well reason why you seat on top of them wheel, not in the back of it like on a normal bike.


----------



## patineto (Oct 28, 2005)

I present you the *NutCracker* version One.









I made the drawing on the same template, so is easy to see how much of a difference in the wheel base can be achieve..

As you can see (I hope) I draw the wheel on the resting position and then on a fully compress (maybe to much travel, about 7 inches or so) to find the limits and requirements to figure out were the stocker seat need to be located and also how short the wheel base can be made..

The arch shape in front of the rear seat, represents the protection device that will be require to protect the "baby factory" from the spinning tire.

Hopefully I will make a few more drawings today and refine the lines, proportions, interfaces and possible interactions, but I do think the potential is there, even if is a lot of work to make it hapeen.


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## patineto (Oct 28, 2005)

BigNut said:


> Middleburn offers crank arms in 165mm - 180mm that are adaptable to trials use, and with a lifetime warranty.


Nice to know.

Are the available in the US with out much trouble..!?!?



> The Whyte front fork was a version of BMW's Paralever suspension. I think that sort of system would offer some promise, as it certainly works on BMW's. Is Whyte still around?


Well the Whyte version as you can see has a "Linkage" that moves the wheel path backwards when the fork compresses, No idea why but is interesting.









This is much closer to a Telelever system.









The BMW R12GS basic chassis with telescopic forks (none linkaged legs)









As you can see on other pictures I have at least half a million miles of experience riding of Televelers and I fully understand the advantages in terms of performance but also longevity and durability of the pivot points. etc 
but also experience the shortcoming in terms of suspension travel.

tell me about it.









(Ps: actually BMW STole the design from a English man, I just don't remember his name)

So far i did not want to confuse the drawings any farder but yes a Anti dive suspension will be optimal for a tandem.


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## patineto (Oct 28, 2005)

sparrow said:


> More short wheelbase shots, just to get an idea. Maybe a gearbox mounted mid-frame:
















































Thanks for the extra photos, they are fun,.


> Well, sorry for the linkage, but something like BigNutt suggested. Run the stoker behind, or directly over the rear wheel. Put the gearbox, derailer system, or Rohloff type transmission mid-frame, some sorta 4-5" travel rear suspension. Hmmm, radically shorter wheelbase does seem to have potential to improve offroad tandem riding.


Nothing to be sorry about.

the more complicated the Puzzle the more fun that it is to solve


> That said, our current 5" travel Ventana El Conquistador de Montanas is a pretty fine handling bike. The new platform valved suspension available for front and rear are fantastic. New FR/DH application brakes (ie Gustav hydros), 20mm thru axle front wheels and the oversize telescopic forks with very adustable damping for compression at different stages of the stroke are a powerful new set of tools to use for offroad tandem riding.
> 
> No need to wait for linkage forks to be designed and produced for offroad tandem use, no need to wait on gearbox drives and further tweaks to rear suspension design for the "ideal" FS off road tandem.


If that way the way thinks work we will be riding on Stone wheels, or even worst just dragging things around.

yes current tandems are pretty good as well as a computers were great (as good as they can be at the time) ten years ago but today they are a joke,

hopefully we can figure out a new concept that provides that much Improvement too, that make the current bikes obsolete.

Personally I do think is a lot of room to improve on tandems on topics rigidity, pivot longevity, suspension response, wheel base and path of travel, center of gravity, Complexity and compromises of the drive train, lower price, etc

The way I see it is way to many "Tandem Nazy's" (on the "Bike forum") around trying to keep the status quo intact but i think is about time to break the mold.

At least i will like to try.


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## patineto (Oct 28, 2005)

BigNut said:


> After several years of
> maintaining a fleet of demo tandems, I'm a firm believer that the simplest solution is the best solution, especially for drivetrain wear parts. While the more complicated systems offer benefits, we find it them more succeptible to chain suck, and more work to maintain. The best option is the fewest chains, and the fewest moving parts.


Well senor, your Motives and mine are very different.

I like the challenge, I like to play, I like to make my head hurt, but yes If I was to make a bunch of them for dally use by not exactly expert riders the design criterias will be totally different.

I'm a admirator of simple things, but sometimes to get there you need to take the "Long way around"


> I look for solutions from what's readily available, for the most part, because development and testing of new designs is expensive. Thus, I look for ways to adapt currently available parts for tandem use (hey, that's the tandem mtb way by necessity). However, it's very cool to see folks thinking beyond the current constraints and looking for completely different approaches to a problem.


Oh Dude Improvise and adapt are my middle names, but also I don't like to be constrain by what is available and even more "Except it'

So something you just need to make new things so you can reach your dreams.


> The derailleur in a box system could be combined with something like Schlumpf's cranks *Schlumpf Crank* which would offer the dual-range setup. Combining this with either the DIAB or Rohloff drastically broadens the gear range.


Yeah I was thinking of the two speed cranks too.

You just need to figure out a way to mount it at the "Junction box" were the timing chain gather.



> I have an ATC fork with dual disc mounts. I aslo have a right-side mechanical disc brake from Winzip. I used a cable splitter from QBP to a single lever. The WInzips have great heat dissipation abilities, but not great stopping power in their current form (too much lever pull). The result was that the dual WInzip brake setup, while very cool, didn't actually feel much stronger than a single Magura Gustav, or even an Avid BB7. I suspect it would have fantastic capabilities for long descents, but it wasn't practical in everyday use. The weight penalty wasn't offset by performance gains.
> However, the right-side disc bracket is available for ATC forks by custom order.


Lever travel, psiton rathios, etc all this issue can be solve is just matter of calculating, gestimating or just trial and error until things work out..

I do like the ATZ forks, very rigid and pretty long lasting too.


> I also have a source for dual-disc hubs in 20mm axle version.


that is great to know.


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## patineto (Oct 28, 2005)

Another "NutCrusher"

A lot tighter & Compact this time.









I'm liking this concept a lot, time to make some isometric views I guess.


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## sparrow (Dec 30, 2003)

Something like that just may work. Now to fabricate a hardtail first, to see if the "short wheel base" is indeed an improvement. It *ought* to be pretty straight forward to develop a hardtail with the short wheelbase concept. I think it'd be a good idea to get real time riding on a SWB off road tandem before moving ahead with the complexities of full suspension. Equal weight riders may find it to be a bad deal!? If a heavy stoker unweights the front end too much, that could spell trouble.

A separate drivetrain idea (for this SWB or other tandems) would be to have the rear hub fully fixed. A fixed cog. The drive chain to the rear wheel would/could have a perfect chainline to the fixed cog to the mid-frame gearbox/Rohloff style transmission (what ever that should end up being). The rear braking duties could even be handled with a disc brake at the mid-frame gearbox system that applies braking force to the rear wheel through the drivechain. I've seen that on some older dirt motorbikes, a small disc brake at the drive cog right outta the gearbox (ATK? and others) This may be purely silly over-thinking, but it could work. Of course, the simplest solution usually is best, but hey, this is just arm chair engineering going on here.

But a derailer-less rear end hub, through axle, wide hub flanges would be easily executed by making use of a mid frame transmission of some sort.


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## patineto (Oct 28, 2005)

Okay this ones are not a radical, The stoker still seat forward from the rear wheel.

the wheelbase is being reduce as much as possible.

The Low swingarm pivot give the wheel a "Radial path"









The High swingarm (very high in fact) generate a arch outwards (backwards) so the wheelbase can be made shorter with out the rear wheel and seat colliding at the end of the travel.









I made the rear Swingarm in such a way (Curved) the "Pedal" mounts can be "Inside" of the path of travel and closer to the center line of the bike to make the Q-factor narrower and hopefully also achieving a nice tight chainline.

Much more work to do before starts to makes sense and developed that K.I.S.S.(keep It Simple Stupid) that is so Important,But is getting there.


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## TandemNut (Mar 12, 2004)

The basic constraints to tandem design remain:
Top tube length will have to be within current parameters, since that's so wired to rider comfort. 
The distance from the seat rails to the bb will also have to be within current averages, due to the physiology of bike riding.
However, a VERY slack seat tube for the stoker, and possibly even a semi-recumbent position would allow the stoker to be positioned more over the rear wheel.
It seems to me that you can't cantilever the stoker BEHIND the rear axle, as that will screw with the handling too much, especially for equal-weight teams. 
Second, the stoker crank needs an axis to rotate around. It can either be a bb in front of the rear wheel (limited by the diameter of the wheel to a minimum distance), or over the rear hub, with the hub itself acting as the stoker BB. This could probably be done relatively easily with a Rohloff, with a change of axle ends and installation of a freewheel for the captain's cranks.
Yes, a hardtail would work best for that. Problem is that a hardtail of this type will transfer much more shock to the stoker, being directly over the rear wheel.
So, I'm thinking 24" rear wheel, for starters, to increase the space to work a seat mast assembly over the rear tire. 
Of course, you could also hinge the frame in front of the rear wheel, and the stoker moves et al with the rear wheel/swingarm (Howzat for thinking outside the box?).


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## TandemNut (Mar 12, 2004)

http://cycletrack.blogspot.com/2007/05/tandem.html
This is the same sort of thing I was remembering. Thanks for finding that!

If the stoker is semi-recumbent, then the stoker bb can be just behind the captain's bb, say with a 15" boom tube. The cranks would have to be in phase to accomplish this, and I don't know how the ergos of the stoker's legs would work that close behind the captain. The track tandems in the pictures seem to take this approach.

This puts the stoker's cranks centered around a bb independent of the rear hub, and lets the rear end move with a suspension.

A horizontal boom would hold the stoker seatpost similar to some later beam-type tandems. Again, doesn't solve the stoker cranks being tied to the rear wheel for suspension movement.

I bet it's be a lot harder to make a tandem spin while climbing with this sort of setup!

Middleburn stuff is easily available through their US distributor, some ragtag outfit called MTBTandems.com.


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## patineto (Oct 28, 2005)

BigNut said:


> http://cycletrack.blogspot.com/2007/05/tandem.html
> This is the same sort of thing I was remembering. Thanks for finding that!


Well at least will fit on my motorcycle really easy...


> If the stoker is semi-recumbent, then the stoker bb can be just behind the captain's bb, say with a 15" boom tube. The cranks would have to be in phase to accomplish this, and I don't know how the ergos of the stoker's legs would work that close behind the captain. The track tandems in the pictures seem to take this approach.


Don Mister BigNut remember this is a Full on "all you can eat" Mountain bike project and a semirecumbent possition for the stocker will be detrimental in terms of the avlity to stand up, hell the two bodys will end up pretty much paralel and really close to each other, No Bueno for sure.

Plus the transsition from seating the standig and viceversa will be really cumbersome, don't you think...!?!?

Plus the Jolts, Oh man the Jolts on the poor stocker Butt.


> This puts the stoker's cranks centered around a bb independent of the rear hub, and lets the rear end move with a suspension.


yes it does, but the mass of the stocker does not get transmitted to the rear axle as efficiently , pretty much the reason why Tandem have so much traction.


> A horizontal boom would hold the stoker seatpost similar to some later beam-type tandems. Again, doesn't solve the stoker cranks being tied to the rear wheel for suspension movement.


Yeap I was thinking of softride beams but then again they move up and down and they will end up colliding with the wheel..

I show you a few other ideas about the attachment for the passanger seat when i draw them.


> I bet it's be a lot harder to make a tandem spin while climbing with this sort of setup!


Really you think....:madman:

Why..!?!?



> Middleburn stuff is easily available through their US distributor, some ragtag outfit called MTBTandems.com.


Double Sucker Puncher Batman, You do have all the Corners cover don't you.

I do have a Question, how do you get around all the MTBR rules about advertising and the need to post anything for sale on the classifieds...!?!?

In the Vintage forum (the only other I frequent) if you post something remotely for sale or even something that you want , Eric will come and erace it right away..

Are you paying them a "Fat fee" or what..!?


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## patineto (Oct 28, 2005)

BigNut said:


> The basic constraints to tandem design remain:


Please please keep Bringing all the important parameters you can think off.


> Top tube length will have to be within current parameters, since that's so wired to rider comfort.


Sure, Ergonomics and body placement are paramount,(notice in all the drawings the cockpits have not being alter at all.)


> The distance from the seat rails to the bb will also have to be within current averages, due to the physiology of bike riding.


On that I have a deggre .

"Ergonomics" and a few years of experience too.


> However, a VERY slack seat tube for the stoker, and possibly even a semi-recumbent position would allow the stoker to be positioned more over the rear wheel.


Yes ad No, I'm sure i brings advantages, but for riding in the dirt I don't think it will work out at the ed..

then again convince e if i'm wrong.



> It seems to me that you can't cantilever the stoker BEHIND the rear axle, as that will screw with the handling too much, especially for equal-weight teams.


I agree, is a nice concept to explore (just for the sake of the Puzzle) But I think will make the bike far to unstable.


> Second, the stoker crank needs an axis to rotate around. It can either be a bb in front of the rear wheel (limited by the diameter of the wheel to a minimum distance), or over the rear hub, with the hub itself acting as the stoker BB. This could probably be done relatively easily with a Rohloff, with a change of axle ends and installation of a freewheel for the captain's cranks.


Not necesarilly, you can have a pair of "Timing chains" going into a common axle (A-fix sprockets) and then from there you can have another chain going to the gear box, Yeah I know is a pain in the butt and also really complex, but gives you so much freedom to place the cranks were ever you want i think is justifiable


> Yes, a hardtail would work best for that. Problem is that a hardtail of this type will transfer much more shock to the stoker, being directly over the rear wheel.


Sure Jolt heaven...

Not even a softride beam or a suspension seat post will help.


> So, I'm thinking 24" rear wheel, for starters, to increase the space to work a seat mast assembly over the rear tire.


No, No actually I was hoping i can go the other way around and be ale to run 29er's specially with a 165mm rear axle and 120mm in between flanges i'm sure you can build a really strong wheel.


> Of course, you could also hinge the frame in front of the rear wheel, and the stoker moves et al with the rear wheel/swingarm (Howzat for thinking outside the box?).


Actually I' being working on some of this ideas for some time, but I'm still failing in figuring out a way to transmit the power from the captain into the rear wheel.

Half shaft, U-joings, Collector boxes, Hydrolics, bound belts that can sway side to side, nothing really makes sense , specially for something as light as a bike.

But yes will be great to have a tandem that can steer from the center like a old caterpillar earth moving machine or even a red fire truck.

Then again you can also make it "rear wheel steering" with Inner radius reference (the two wheel turning on the same axis) or Opposite radius steering (the rear wheel well turn the same amount and direction as the front one) so you can go sideways like a Dirttrack machine with out even trying that hard.

have you ever see something like that..!?!?


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## patineto (Oct 28, 2005)

Today we when for a little Dirt ride on the Single track trails at the golden gate park in san francisco on the Ibis with the JP Morgen stem install (again) but this time my girlfriend lauren was the Captain the whole way..

It was raining, It was wet, muddy and with a few branches lay down after the few storm, but we manage to have a great time..









She is such a tropper.









On of the many "little" trees.









Mister mega Chubby.









Umm Yummy..


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## patineto (Oct 28, 2005)

Just for reference here are some pictures of the Old style JP morgen stem.









Just a Spring no real damper or anything but still work pretty well.


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## TandemNut (Mar 12, 2004)

We hardly ever stand on the tandem. We unweight the saddle for some obstacles, but folks my size (6'3", 250lbs) don't tend to stand up when pedaling too much.I don't recall seeing other teams stand on their off-road tandems very often either. So I'm not sure the stoker being able to stand easily is that big a detriment.
The top tube lenght on track tandems is shorter because races tend to be shorter than rides, for the most part. Plus, they're not riding for comfort, but for speed and aerodynamics. A casual mountain or road ride on a tandem with that short a top tube would get uncomfortable pretty quickly.
Parelever/Telelever; it doesn't take much to confuse me. 
The BMW front end reduces brake dive, but what are the other advantages? Does such a suspension design have more durability than a standard telescoping fork?


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## patineto (Oct 28, 2005)

BigNut said:


> We hardly ever stand on the tandem. We unweight the saddle for some obstacles,


I guess is my fault, I call "Standing" the act of taking your butt from the seat, it can be half a inch it can be fully extended.

Actually the other day, I was trying to teach lauren how to "bunny Hoop" the tandem, well not exactlly a bunny hoop, but a syncronize way to lift the two wheels at ones, Just it takes a lot of time to learn, but is a great skil to have.

Also I guess we do ride differently but I still like to stand from time to time and encourage my stocker to do it too, better blood flow, painless bumps, you name it.



> but folks my size (6'3", 250lbs) don't tend to stand up when pedaling too


Don't tell me now is a rule about leaving your seat uncover for more than two seconds.
Yes very seldom I stand to power the tandem (reason why I like the long cranks) but again i think is a good skill to have.

Actually I think people learn to not stand up, because tandems feel like a wet spagetti when you are off the saddle.



> much.I don't recall seeing other teams stand on their off-road tandems very often either.


 Call me old School if you like but you legs are one of the best suspension system that is...

Letting the bike suspension do all the work of isolating your from jolts, jumps and obstacles is what make this machines so soft.

Also after riding my Big motorbikes for years in the dirt I have learn to never land from a jump when I'm seating, hell you ride on the pegs prety much the whole time since that way your body mass is transmited to the foot pegs that are for lower in terms of center of gravity than the seat, plus you get far more control.



> So I'm not sure the stoker being able to stand easily is that big a detriment.


MIster BigNut you are sopose to be the Expert here, so please tell me I'm missing something, but a Mountain bike tandem has a whole realm of requirements that have little to do with road riding and much less riding on the track.



> The top tube lenght on track tandems is shorter because races tend to be shorter than rides, for the most part. Plus, they're not riding for comfort, but for speed and aerodynamics. A casual mountain or road ride on a tandem with that short a top tube would get uncomfortable pretty quickly.


Short term high power output exercises like a 5K on a wodden velodrome and long term "Low performance" riding in the dirt are totally different things, with a complete of compromises and criterias .

Ps: Many times living in Colombia a serve as a "Pace" vehicle using tandems, even on the track since at one time of a my life I was a pretty good sprinter, not like this days. and even then we manage to "Mini-stand" (specially the stocker) TO increase the frontal area and the aerodynamic affect call Kann that extend a "Envelope of calm air" behind the ridies tail..

ps: Using a windtunnel I manage to Landluge at about a 100Kph in the 80' so I'm well aware of the subsonic air drag and presure point caracteristics.

Then again Airflow and Mountain tandems have very little to do, compare to the Biomecanical requirements.


> Parelever/Telelever; it doesn't take much to confuse me.


"Paralever" = *Paralel* + *Lever* arms.

Actually they are not exactly parallel as much as they are a parallelogram but lets try not to confuse here, this terms is usually applied to rear suspension, in fact is a "Brand name" and a necesity for BMW Shaft driver bikes, since "Monolevers" transmit a lot of the torque produce by the shaft drive (twisting forces) into the moto when you accelerate.

Telelever, is again a BMW "trade mark word" to empty the A-arm type suspension device they use on their R11XX since 1993.











> The BMW front end reduces brake dive,


Big time, in fact that is the main reason to implement it.



> but what are the other advantages? Does such a suspension design have more durability than a standard telescoping fork?


Here is a drawing I made about nine years ago, when I start to dream about making my own motorcycle frames (sadlly still a dream since is much Much cheaper to buy complete whole bikes (and they are not cheap for sure), than make custom frames.










Features a crazy idea of a Hybrid front suspension design using a half Telelever half upside down fork, to optain the rigidity and easy to ride of the telelever but also get the require amount of travel necesary for serius dirt bike riding.

Ps: The geometry of the Telelever has a limited amount of travel available, to get more travel sadly you need to make the menbers bigger and you can only go so far.

In terms of fabrication, materials, long term durability just Imagine a bicycle headtube that is 2 feet long and how little effect a losse headset will have (the headset rocks only a certain amount) compare to a headtube that is 2INCHES Long, that very same amount of movement at the headset will feel far wrost.

Plus the engine blocks are use as stress members and pivot mounts since they need to be machined anyway and then the "Subframes" can be made in somehow simpler manners with out much worry for tolerances if you compare to a conventional "head tube frame"

Nothing to do with Televelers, just for fun.

A Part of one of my projects.









Adjustable Head angle frame with a Ram-air intake port just because I can.

Integrating the headlight, airbox and a few other things.


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## TandemNut (Mar 12, 2004)

Thank you for the comment, however, I don't consider myself an expert. I have the advantage of building these bikes on a regular basis over the past several years, and doing so gives me the opportunity to get real-world feedback from customers and folks like the members here. I try to listen to that feedback and make adjustments or changes where possible.

All of our perspectives are formed by our own experiences. I'm not now and never was a pro or semi-pro rider. Ask anyone who knows me; I'm built like a linebacker, not a bike rider. As a large rider, I don't tend to stand much, even on a single. My CG is already too high for technical maneuvers, and standing just makes it worse. 

We hardly ever stand while riding the tandem off-road, except to provide some relief to sore bums now and then. The suspension does a great job of soaking up bumps, so we don't unweight the saddles as often as you may have to riding a fully rigid bike (and that fork transfers some major shock).

I don't have much experience with semi-recumbents, etc (yet), but with my back problems, I am pretty sure I will have to investigate such things sooner or later to keep riding. In the meantime, it would sure seem to be a relaxing ride to have the stoker laid back some and by necessity, relaxing. You could even rig up something similar to the sling-type seats that some recumbents use, to help take the edge off the bumps in the back. 
Other than that, I don't see another way to get the rear wheel more under the stoker and still have a workable option for suspension. 
(except a crank through the rear axle, a 24" wheel and a 3" rear trials tire...)

When you contrast the positions of road racing motorcycles vs motocross bikes, the road racing guys are much more forward-leaning than their off-road counterparts. So there's some basis for the thought of a more reclined position working off-road. And in the spirit of open-minded discussion, I throw it out there as one possible solution to the ergonomics that force minimum top tube lengths and bb positions on traditional tandems.


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## patineto (Oct 28, 2005)

BigNut said:


> Thank you for the comment, however, I don't consider myself an expert. I have the advantage of building these bikes on a regular basis over the past several years, and doing so gives me the opportunity to get real-world feedback from customers and folks like the members here. I try to listen to that feedback and make adjustments or changes where possible.


Oh dude your bikes are sick...

Everyone I ever see is very well plan and executed.


> All of our perspectives are formed by our own experiences. I'm not now and never was a pro or semi-pro rider. Ask anyone who knows me; I'm built like a linebacker, not a bike rider. As a large rider, I don't tend to stand much, even on a single. My CG is already too high for technical maneuvers, and standing just makes it worse.


I was a "Pro" level rider many years ago (about 16 years ago), well competing to become part of my national team, but I hear you, I'm clumsy Chubby and for sure "Big boned" even then, but I still love to see how far I can push it.


> We hardly ever stand while riding the tandem off-road, except to provide some relief to sore bums now and then. The suspension does a great job of soaking up bumps, so we don't unweight the saddles as often as you may have to riding a fully rigid bike (and that fork transfers some major shock).


I learn to ride on rigid bikes, so to me is second nature to become the shock absortion system.



> I don't have much experience with semi-recumbents, etc (yet), but with my back problems, I am pretty sure I will have to investigate such things sooner or later to keep riding. In the meantime, it would sure seem to be a relaxing ride to have the stoker laid back some and by necessity, relaxing. You could even rig up something similar to the sling-type seats that some recumbents use, to help take the edge off the bumps in the back.


I much rather figure out 'cures" than just "Palliatives" a proper solution will hopefully circumvent the need for Gizmos.



> Other than that, I don't see another way to get the rear wheel more under the stoker and still have a workable option for suspension.
> 
> (except a crank through the rear axle, a 24" wheel and a 3" rear trials tire...)


well just because the soluttion is not available evident or even obvius, is no reason to settle for something mediocre or with way to many compromises..

hey maybe it can not be done, but at least i like to try.


> When you contrast the positions of road racing motorcycles vs motocross bikes, the road racing guys are much more forward-leaning than their off-road counterparts.


Road => lack of front end weight = flip or at least lack of control for the front wheel.

Plus air flow control and minimal frontal area are paramount..

Just Imagine a "Supplina" A.K.A. Harley cruiser position motocross bike, oh boy I will love to see that.



> So there's some basis for the thought of a more reclined position working off-road.


Static and Dynamic ergonomics are very different things, even if they stem from the same branch...

I'm more of a advocate of letting the human body do the shock absorption duties than not letting the bike do all the work, actually somewhere In between is optimal



> And in the spirit of open-minded discussion, I throw it out there as one possible solution to the ergonomics that force minimum top tube lengths and bb positions on traditional tandems.


Oh I get that and i really like the way you see things too..

Keeps me on my toes and make me aware of other variables that I did not see before.


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## patineto (Oct 28, 2005)

Here is a somehow more evolve concept of the Version with the stocker pedals in the "Middle" of the rear wheel.









The basic frames make sense, now I need to finish drawing all drive train belts, sprockets, gear boxes, but so far is no inteferance that i can tell.

More to come soon.


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## sparrow (Dec 30, 2003)

Yowza, that's a bit of evolution there. BUT, how's about figuring out a way to fabricate a hardtail Short Wheel Base tandem to do a little riding and development to see if indeed a SWB is gonna work, or work better? It would seem the components would be available to cobble together an offroad tandem utilizing a SWB in a hardtail. Hmmm, then throw suspension in the mix if things seem to work.

I do like the basic premise, to shorten the boomtube radically to increase the bike's clearance without increasing bb height and overall center of gravity. I'm intrigued enough to get a framebuilder acquaintence of mine working on this!


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## patineto (Oct 28, 2005)

sparrow said:


> Yowza, that's a bit of evolution there. BUT, how's about figuring out a way to fabricate a hardtail Short Wheel Base tandem to do a little riding and development to see if indeed a SWB is gonna work, or work better? It would seem the components would be available to cobble together an offroad tandem utilizing a SWB in a hardtail. Hmmm, then throw suspension in the mix if things seem to work.


I tend to design the other way, I try integrate and accomplish as much as possible and make it work in a "worst case scenario" Then anything simpler why work with out a problem.

you are totally right, I need to make a basic platform to test the concepts, maybe even ask Berny Mikkelsen now that he is better to help me out with one of his crazy (Visonary, revolutionary, amazing) "Adjustable" frames so we can vary the wheel base , head angle etc and see what happen


> I do like the basic premise, to shorten the boomtube radically to increase the bike's clearance without increasing bb height and overall center of gravity.


Well from the start if the captain timing ring is replace for a smaller diameter unit and then move to the very center of the frame, you are already gaining at least 2' maybe even more inches when you are leaning the bike over, plus you can have a total "Substandard" Q factor since you don't have the wheel chainstays or even chainrings to stop you, so you can pretty much make it as narrow as the BioMechanical requirement dictate, hell 95mm in between pedals will be much, much better than 150mm on a stock bike in terms of obstacle aviodance.

Then the "BooM" tube can just connect to the gear box Up High (4 to 5 inches higher than normal) giving you a sh^tLoad of ground clearance when you are passing over a rock, tree trunk or a Little baby..

I'm really liking this, I don't know if you guys can tell, but the stocker cranks will be set "Inwards" (well like if they were mounted on a 150mm BB spindle) right next to the spokes as much as possible and also the "Timing chain's" coming from the back cranks.


> I'm intrigued enough to get a framebuilder acquaintence of mine working on this!


Well we are in this togheter, do whatever you can with the ideas, after all they need to be used if not they will sadlly dye inside some desk droor.

You see just a few ideas and already the current way of making tandems start to look kind of Outdated, and we did not even start to build anything so far..

Ps; I have projects for my own business (I can not show do to Patent crap) that I have work for years and they keep getting better and better, in fact for one of them I have about 5 inches stack of drawings (like the one above) that is about 1000 pages and many, many 0.5mm pens...


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## patineto (Oct 28, 2005)

Here is a Better drawing of the same concept, Actually i discover i made at least one drawing mistake with the location of the "Lower BB" is sopose to be about 2 inches higher, reason why the whole thing looks kind of "Funny".

In this case I left the space empty for the "Gearbox", "dérailleur in a Box" or whatever drive train I'm going to end up using in the middle of the frame, but the rest of the Pulleys and belts are in place.










Please If you see something that scape me or just a stupid mistake let me know, this are very preliminary drawings just checking concept, so is no big deal if they don't work out.


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## TandemNut (Mar 12, 2004)

It looks as if you have the stoker's cranks using a "half" bottom bracket on each side. The first thing I think of when seeing this is what happens when someone my size starts torquinng on those crank arms. Without a decent bb shell width to traigulate the junction of the tubes and bottom bracket, how will you keep that bb area from flexing? (within reasonable parameters, meaning not using unobtanium spacecraft tubing or alien alloys).


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## patineto (Oct 28, 2005)

BigNut said:


> It looks as if you have the stoker's cranks using a "half" bottom bracket on each side. The first thing I think of when seeing this is what happens when someone my size starts torquinng on those crank arms. Without a decent bb shell width to traigulate the junction of the tubes and bottom bracket, how will you keep that bb area from flexing? (within reasonable parameters, meaning not using unobtanium spacecraft tubing or alien alloys).


Yeah is for sure a issue to resolve or at least deal with, then again I have *Buckminster Fuller and his Triangles* on my side..

This whole project is going to be full of little issues to resolve, if I let each one of them stop me or even worst make me compromise or deviate the whole Ergonomic and bike-dynamic templates (Like placing the stocker pedals on a bouncing axle) just because I don't know how to solve a simple problem I will never get anywhere (Very commun problem in the design process), besides I Think already know how to fix it pretty good (I hope at least) with out any fancy parts, (in fact all recycled) I just did not want to draw every detail to avoid extra complexity not necessary at the moment.


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## TandemNut (Mar 12, 2004)

That yoke at the end of the seat tubes that holds the bb's brings some interesting ideas into play. The center drive timing belt reminded me of something;
If you could eliminate the horizontal boom tube, you could run a belt with teeth on both sides. Then you could "catarpiller" over logs and stuff...


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## patineto (Oct 28, 2005)

BigNut said:


> That yoke at the end of the seat tubes that holds the bb's brings some interesting ideas into play.


Yesterday I made a request for feedback on a "Suspension and Shock" forum and somebody suggest to use this
*Suspension calculation program* I totally forgot about it, I guess I'm not much into computers but the program is very helpful , you can even get a "Tutorial version" for free to try and it helps a lot to understand loads, benefits drawbacks, etc of each system.

About this tandem..

For example The center line location of the timing belt is one of the many issues that will make the "Tandem Nazi's" spin on their heads with their "Dye in the Wool" Attitudes, just because their "It can not be Done" ways

Tandems, well some parts of them are totally obsolete and you know what they say, the "Chain is as strong as the weakest link" and only because of the years of traddicion that never really eveolve, besides Is not like you can run stock "Right side" cranks on a tandem anyway, so what is the big deal of making a special bottom bracket or other necessary parts if they bike can be made much better.


> The center drive timing belt reminded me of something;
> If you could eliminate the horizontal boom tube, you could run a belt with teeth on both sides. Then you could "catarpiller" over logs and stuff...


Even better, attach your Favorite old worn out tire to the belt and go for a ride, Maybe like this.









*No...!!!!!!!*

In all seriousness as long as the two "Timing pulleys" are the same size (and they don't even need to be as long as the rathios are the same) you can run as small of a belt as the requirements require, aka 36t chainrings or bigger are the norm because nobody ever developed a proper system that is much smaller using a different approach ,

On a side note running the "Timing chain" at the very center will circunvent every issue of Frame deflexion do to the asymmetrical loads that a left side chain compromise, as easy as that.


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## TandemNut (Mar 12, 2004)

The tires on the frame must be a fashion statement, because they sure do look like they'd be painful in an unscheduled get-off...

The center timing belt/chain might also allow the use of two BMX style freewheels, which could help provide some independent pedaling options. Not that such is as important off-road, but mass appeal helps sell tandems.

We can run timing rings as small as 20T if necessary. We don't because with 32T rings, there's just enough chain deflection to split the load between the chain and the boom tube when high-centering on a log. 

We could run 30T or even 29T rings very easily as well (the 29T would be Middleburn's DUO inner ring/spider. 

So what's the disadvantage of a shaft drive? How much less efficient is it?

BTW, screw the tandem nazis. Many of them still think disc brakes are not strong enough for tandems. How can you reason with such logic?


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## DrewM (Jan 8, 2007)

patineto said:


> Here is a somehow more evolve concept of the Version with the stocker pedals in the "Middle" of the rear wheel.
> 
> 
> 
> ...


I may not be seeing something; however, if your stokers seat mast is attached to the main frame and their crankset is acting as a through axle for the hub then the distance from their saddle to the crankarms is constantly changing.

I have owned a few "sweet spot" bikes and ridden a bunch and as long as suspension travel is under three inches the sensation of the cranks coming up-and-forward is easy to get over. Sitting on my old Rocky Mountain Speed though (5" of Sweet Spot URT travel) I could never get over the sensation of the pedal-saddle distance constantly changing.

I'm racking my brain but I can't think of a good solution since using the crank axle as a thru axle is a really good idea.


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## DrewM (Jan 8, 2007)

BigNut said:


> It looks as if you have the stoker's cranks using a "half" bottom bracket on each side. The first thing I think of when seeing this is what happens when someone my size starts torquinng on those crank arms. Without a decent bb shell width to traigulate the junction of the tubes and bottom bracket, how will you keep that bb area from flexing? (within reasonable parameters, meaning not using unobtanium spacecraft tubing or alien alloys).


Beat me to it. I see the drawing differently now too.

Your saddle-crank distance is constant but your stoker ends up sitting quite high.


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## patineto (Oct 28, 2005)

BigNut said:


> The tires on the frame must be a fashion statement, because they sure do look like they'd be painful in an unscheduled get-off...


Big Nut did you ever see my signature...!?!?
*"Only him that attempt the absurd is able to achieve the Impossible"*

Yes The tire Idea it Does NOT work, actually i work great as a chainstay protector, No noise, No rock nothing but it holds chain lube like crazy.

The down tube protector after eing in whistler and other downhill places made sense at the time do to the way the bikes are treated.

The top one just plain sucks

But since then I'm being going this way * A Useful clever way to protect your Chainstays*

Simpler, more elegant, lighter and for sure more efficient.



























Actually I did make a tire protector attempt for a boom tube on my tandem but is much to clumsy so I ditch it.











> The center timing belt/chain might also allow the use of two BMX style freewheels, which could help provide some independent pedaling options. Not that such is as important off-road, but mass appeal helps sell tandems.


Well that is being the Idea all along..

you see how something that nobody ever talk about before, becomes "Vox Poluli" the minute that somebody comes up with a Idea that is "Comun Sense"

Hey maybe someday tandems with "Side drive chains" will be as obsolete as Biopace chainrings, that will be fun even if I'm sure somebody will claim that they Invented first, Like gary Fisher has done pretty much his whole life.


> We can run timing rings as small as 20T if necessary. We don't because with 32T rings, there's just enough chain deflection to split the load between the chain and the boom tube when high-centering on a log.
> .


A wide Industrial type belt, even a harley type belt is wide and for sure with sufficient tension strength to be run with out "Derreilements", yes if the diameter of the pulleys is to small the belt teeth will start to delaminate, but I'm sure it can be made far smaller than a current conventional timing chain.

Also remember side loads are present far more on a chain that is "OFF Center".

the Boom tube flexes to one side (the chain compressses the left drive side, but even if the same chain was at the very center of the frame the pedaling forces will be "Self cancel" since everything is on axis.


> We could run 30T or even 29T rings very easily as well (the 29T would be Middleburn's DUO inner ring/spider. .


You see being bound by what is available is already obsolete, we need a Proper Cure for the issue, not just a "Paleative" (little chessy fix)
.


> So what's the disadvantage of a shaft drive? How much less efficient is it?.


As long as I know IBIS was working on a shaft drive tandem before they close, but sincerely I think they are far to heavy even if you can make them out of Composites like in some race cars.

besides it will cost as much as a whole tandem to make a shaft made out of aerospace Composites (not just cheap chinese carbon fiber)
.[/QUOTE]
BTW, screw the tandem nazis. Many of them still think disc brakes are not strong enough for tandems. How can you reason with such logic?[/QUOTE]

Yeah "dye in the Wool" thinking can be great to keep the Status quo going, but also can get to smell kind of funny some times if you hold on to it to hard...

I never try to be dogmatic about my ways, I Try to present logical arguments ( being a Science Geek, a science Geek that can not type for Sh^t since I'm super dyslexic)) and factual data, but I'm always open and Hopefull to change my mind if a better argument comes my way....

Hey we can do a Brake test side by side any time you want..

On the contrary I'm the one that hopes you don't get mad with me, when some frame Manufacture copy this "center drive belt" Concept and you end up putting Pink "heavy discounts tags" on your tandem inventory because side drive chains are a thing of the pass.


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## patineto (Oct 28, 2005)

DrewM said:


> Beat me to it. I see the drawing differently now too.
> 
> Your saddle-crank distance is constant but your stoker ends up sitting quite high.


Well Drew that is kind of the problem with this short wheel base (Rear pedals inside the rear wheel space) / full suspension concept..

The "Seat Drop" is for sure limited by the path of travel of the wheel (The old "Two things can not occupied the same space at the same time" works here too), so the wheelbase need to be alter (made longer maybe) or a more "Rear ward" wheel path need to be achieve so the seat can be drop farder down (and the butt of the stocker protected, just in case he or she falls on a "moving tyre" NO Bueno for sure.

Again we are far from Finish on this project, but I also learn long time ago that If you start to worry about the bread crumbs falling from the plate, you never end up eating dinner in the first place..


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## patineto (Oct 28, 2005)

This is getting Better and better after posting this a question about * Really high Pivot points..!?!?* on the Suspension forum.

There I found this forum call *"Linkage"*
from bikechecker.com that offers a wonderful computer program (you can even get a free version if you like to trying) and is going to make my life a lot easier (when I figure out how to use it propertlly)

I keep you guys posted on the evolution, so far I'm being playing with the program a lot trying to get better at it.


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## TandemNut (Mar 12, 2004)

I am enjoying the thought process and evolution of ideas here. I couldn't "get mad" for someone thinking beyond the constraints in place in the bicycle marketplace.
However, as a tandem manufacturer of sorts, I've learned a couple of things pretty quickly:
1. manufacturers are not willing to make small runs of any part unless the parts end up being VERY expensive. Therefore, while the yoked seattube bb ideal makes a great deal of sense to me from a practical standpoint, I know how difficult (expensive) it will be to have the necessary components made. We have some of the same problem with things as simple as tandem cranksets; sure, if I buy 500 sets at a time, I can get them at a decent price (still probably twice what companies like Cannondale pay for them). But for a company our size, ordering in such quantities isn't practical. 
2. While lots of folks are open-minded about technological improvements in bicycle design, many are not, as evidenced by the reactions you get from the traditional tandem community. To me as a manufacturer/dealer, that's a huge issue, as sales are always difficult with something that is new and radically different. 
Absolutely not wanting to limit the thought process here, but instead stress why I examine things from the position that it's important to adapt existing components/systems whereever possible.
Keep the great ideas coming!

On the boom tube protector, Seattle Jack actually used a half-pipe piece of very slick PVC, which allowed the tandem to slide over logs much easier. Makes mucho sense to me.


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## patineto (Oct 28, 2005)

BigNut said:


> I am enjoying the thought process and evolution of ideas here. I couldn't "get mad" for someone thinking beyond the constraints in place in the bicycle marketplace.


When I was at school many years ago.

I teach a Industrial design class in "Lateral thinking" (We did not even have a name for it then) kind of base on brainstorming, playing with word and concepts and joking around and we came up with stuff as clever as a "Camelback" (4 year before the "real" one came on the market) but the designer never made any thing out of it (The student that develops the idea, owns the intellectual rights) among a few other really cool things.



> However, as a tandem manufacturer of sorts, I've learned a couple of things pretty quickly:


You see that is the whole beauty of it, I only need to make one and is going to be for me and I don't care if is a "Little Funky", and if it needs to be fix from time to time at home or on the road.

take my Bicycle rack for my motorcycle for example, I took me three hours to make it almost 10 years ago out of recycle bike parts and still work perfectly after all this trashing, but If i was to make one for sale (I can not do to liability issues) will take me forever To "do it Just Right" and will also cost a ton of money.

Yes I know making On off is super expensive, but I grow up adapting things to work for my own porpuses and I also have access to a pretty decent shop and even better a bunch of very smart playful geeks that like to make cool stuff.



> 1. manufacturers are not willing to make small runs of any part unless the parts end up being VERY expensive. Therefore, while the yoked seattube bb ideal makes a great deal of sense to me from a practical standpoint, I know how difficult (expensive) it will be to have the necessary components made. We have some of the same problem with things as simple as tandem cranksets; sure, if I buy 500 sets at a time, I can get them at a decent price (still probably twice what companies like Cannondale pay for them). But for a company our size, ordering in such quantities isn't practical.


Oh Senor I hear you loud and clear...

For my own company I have so many projects I never got to make do to that very fact I can only afford to make small runs and also that I refuse to go overseas and get a product that is "Somehow" that I order (Yes I know about quality-A products and everything) Very sad but not much I can do at the moment.

Again this is just a proof of concept and I don't care if I never make more than one , actually that is the whole point of it. just to show how much better things can be if you step away from the box a little (So far except for the "Stubby" centered belt drivetrain system (for added clearance and lower bottom brackets) and the Ratchets at the cranks for the "independent drive", is nothing that clever but will see what happen the more the process evolve.

After all I'm sure you know the old bicycle joke really well..

*"How to you end up with a Million dollars on the bicycle industry..!?!?

Well You start with Two million"*


> 2. While lots of folks are open-minded about technological improvements in bicycle design, many are not, as evidenced by the reactions you get from the traditional tandem community. To me as a manufacturer/dealer, that's a huge issue, as sales are always difficult with something that is new and radically different.
> Absolutely not wanting to limit the thought process here, but instead stress why I examine things from the position that it's important to adapt existing components/systems whereever possible.
> Keep the great ideas coming!


Well if that was the case the poor Taiwanese bike geek that developed the A-head system must dye in hell.

innovation is all about change and also challenge, if the idea is good enough (The pure concept, no just the "Design") it will prevail, then again that is the Ultimate designer dream but also nightmare since most of the time some lawyer will clean you out do to some mistake you make when filling the patent (then you need the mega super expensive lawyer on your side too, No fun, Not cheap)...

Same Reason why I prefer Independent "strange" Films even if they don't give a rat ass about what you think of them, than extremely marketed reserch 2 hour popcorn megaplex videos that end up being a "Formula" repeated time after time like a cheap song.

Just look at PIxar, before and after Disney, So, so very Sad..


> On the boom tube protector, Seattle Jack actually used a half-pipe piece of very slick PVC, which allowed the tandem to slide over logs much easier. Makes mucho sense to me.


My First attempt many years for a Boom tube slider and protector was base on a old snow skinny ski, the problem was to find one in colombia since we don't really have snow down there (Yeah I know every joke, not the real type of snow at least)

I just made a pair of brackets to hold it at the same height as the chain using a old "Trials bash guard" for the front (very strong, supported and triangulated) and a machined bracket for the back.

Sadly it was much to heavy and even worst way to slippery, so the bottom of the bike will come from under you in unpredictable ways (like a ski when going sideways)

Today I just thing the best thing, still is not to have anything to slide on if possible., but I'm also not willing to ride on 15inch high bottom brackets to achieve it.


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## D.F.L. (Jan 3, 2004)

I made this about 10 years ago.

I thought about split cranks, but there are too many structural problems to overcome with a split crank spindle. I don't think it can be stiff enough at a reasonable weight.

Anyway, it didn't work on singletrack at walking pace, so I gave up on it. Last I heard, it's sitting on a grocery shelf in Omaha, surrounding some Dr. Pepper.


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## sparrow (Dec 30, 2003)

Hey, now that looks familiar! Ever been in a magazine? Could've sworn I saw a photo of that in Dirt Rag ages ago. Why did it not work!?


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## bcd (Jan 27, 2004)

D.F.L. said:


> I made this about 10 years ago.
> 
> I thought about split cranks, but there are too many structural problems to overcome with a split crank spindle. I don't think it can be stiff enough at a reasonable weight.
> 
> Anyway, it didn't work on singletrack at walking pace, so I gave up on it. Last I heard, it's sitting on a grocery shelf in Omaha, surrounding some Dr. Pepper.


WOW, now thats amazing. what a fun ride i bet that was.


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## patineto (Oct 28, 2005)

D.F.L. said:


> I made this about 10 years ago.


what were you looking to achive..

Same compact, agile package..!?!?

Any more pictures of the build process, build bike, those awesome renderings, whatever you don't mind sharing, I will love to understand the pro's and cons and also your motives and frustrations.

thanks for sharing..



> I thought about split cranks, but there are too many structural problems to overcome with a split crank spindle. I don't think it can be stiff enough at a reasonable weight.


I totally agree, they will be a pain to build and for sure not a rigid and heavier, but then again they let you achieve something you can not do any other way..

That is Unless you were using one of this "Center less Hubs" motorcycle wheels..


> Anyway, it didn't work on singletrack at walking pace, so I gave up on it.


Can you explain us more about the super long top tube length and the "middle tower" why not a even shorter wheel base with a shorter top tube..!?

Did you ever try it with just the two front riders..!?

what kind of issues did you encounter..?
did it get better with speed, ..!?

or just was different but also scary.

Looks to me like the learning curv will be pretty step, but who cares I like the challenge.


> Last I heard, it's sitting on a grocery shelf in Omaha, surrounding some Dr. Pepper.


Wow somebody know how to Draw too.

Industrial designer..?
Illustrator by trade, what..!?

You are good.with the pen, but even better with the brain.

Please I want to know it all.

You think I can I buy it from the store owner...!?!?

I can just get the frame if the part are gone or wasted..

Even if does not work as a bike, your work is very interesting and will be a honor to preserve it and also fun for carrying around my little blind friends from time to time..

In any case I can not thank you enough, this is super helpful, even if the thing did not work at least we have a base to measure from..

Please, please tell us more, much more..


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## patineto (Oct 28, 2005)

bcd said:


> WOW, now thats amazing. what a fun ride i bet that was.


Oh Alex My Hero, please give us all the feedback you feel like sharing..

Congratulations again on your fantastic work, on and off the bike.

Your big fan .

Ricardo


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## sparrow (Dec 30, 2003)

D.F.L. that rig looks crazy indeed. I'd think you could go a bit further to shortening the wheelbase, lowering the bbs. Get the stoker back up to the captain as on a normal tandem, but keep the rear wheel ahead of the stoker... well, that'd allow for a shorter wheelbase by far, making lower bbs and center of gravity and yet reduce dragging the boom tube over rocks and ledges. Seems like a starting point, may as well take another stab at it, eh? What an "outside the box" set up you have there.

Seems that it would be essential to have a lighter stoker by a fair bit than the captain. Equal weight and you'd have trouble getting the front end too light, eh?


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## D.F.L. (Jan 3, 2004)

Dammit. I'm pooped and I was headed for bed...

That was my singletrack tandem. It was meant to go everywhere a 'normal' MTB tandem couldn't go. Originally, I was hoping that 2 strong riders could wheelie it.

Turns out that in order to preserve some weight on the front end, the wheelbase would have to be increased(notice how short it is in the sketches). i don't recall all the numbers, but I think that with riders 160/100lb, the weight balance ended up being 20/80 front/rear. Even so, it wasn't even close to wheelying.

Even with a light rider on the back, the pendulum effect was unbearable. The chassis was very stiff, so flex wasn't a problem. Unfortunately, the large steering movements that we make at low speeds would cause the stoker to wag around, and when the captain would sense those motions, the natural instinct to correct would actually make things worse.

We did take it out on a casual group road ride through the city streets and it worked fine for that. Any tandem works fine for that!

The whole thing was made out of Easton tubing, that. fortunately, was donated. Most of the parts were donated, as it was part of a school project. It did make it into Dirt Rag once.

It's a tandem, not triple. If you look you'll see that the stoker is set back from the captain. The wheels were 24s. The stem a custom 160mm. The bike used a DaVinci jackshaft (run with fixed cogs)with 4 sprockets up front.

I didn't really have any use for it and it didn't work, so I cut it up with a hacksaw. I still have a few scraps if anybody wants an (almost) piece of history; )

Building it was a disaster. It was the 3rd frame I ever built, first aluminum. I didn't know what I was doing at all. I had to make my own dropouts (see pic) and 22mm disk mount. Luckily, I had a patient framebuilder to help guide me.

This was one of the last projects I did before graduating from college. Yes, Industrial Design. And I've barely used those skills since. (Hell, I barely used them on this project!)

I'll be starting another tandem soon: Steel 29er, rigid, S&S coupling, kid-compatible, with Rohloff. We were discussing SWB, but it's probably too much difficulty for this one.

I like your project! I think it'll be great fun.

Let me know what I left out and I'll try to explain.

'night!


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## patineto (Oct 28, 2005)

D.F.L. said:


> Dammit. I'm pooped and I was headed for bed...


Well if you did not respond back I will not sleep, so we are even somehow..

thanks again for taking your time for respond in such a nice way.


> That was my singletrack tandem. It was meant to go everywhere a 'normal' MTB tandem couldn't go.


Yes exact same focus, if I can not make it far better (or at least interesting) thatn any current bike why bother..

So how long was the wheel base..!?!?

I bet on step hills the bike will be almost uncontrolable with the center of mass move to the back.


> Originally, I was hoping that 2 strong riders could wheelie it.


No way In hell.


> Turns out that in order to preserve some weight on the front end, the wheelbase would have to be increased(notice how short it is in the sketches). i don't recall all the numbers, but I think that with riders 160/100lb, the weight balance ended up being 20/80 front/rear. Even so, it wasn't even close to wheelying.


If if the wheel base was about the same as a convencional tandem why botter..!?!?

Traccion..!?!?
Broken hubs and cassete galore I guess.

Wheelie like a mad man.? well I'm sure you saw that coming and the bike will never be a dual seat unicycle no matter how hard you try, since after all is not about power but Balance.


> Even with a light rider on the back, the pendulum effect was unbearable.


Yeah like carrying a five gallon can at the tip of a ten feet pole..



> The chassis was very stiff, so flex wasn't a problem. Unfortunately, the large steering movements that we make at low speeds would cause the stoker to wag around, and when the captain would sense those motions, the natural instinct to correct would actually make things worse.


yeah I got to see that drawback even when I was drawing it.

my bike rack on the motorcycle somehow suffers from the same syndrome then again the moto is almost 600 pounds when the bikes are at the most a 100pounds, but I can see how you can get in trouble fast, specially if your stocker is a scarycat..


> We did take it out on a casual group road ride through the city streets and it worked fine for that. Any tandem works fine for that!


I like the way you think, please tell that to the road tandem geeks worry about 2mm short top tube.


> The whole thing was made out of Easton tubing, that. fortunately, was donated. Most of the parts were donated, as it was part of a school project. It did make it into Dirt Rag once.


Well you got to play with somebody elses stuff, that is already pretty good.


> It's a tandem, not triple. If you look you'll see that the stoker is set back from the captain. The wheels were 24s. The stem a custom 160mm. The bike used a DaVinci jackshaft (run with fixed cogs)with 4 sprockets up front.


Yeah sorry I got confuse.

I just count bars and "Cranks" welll Bottom brackets, but also wonder why the seat were so close togheter, Yes I'm going blind..

24" I don't like but it give me great inside in how much the proportions of the wheels will affect the fit of the bike, specially if is a full suspension running on 26'


> I didn't really have any use for it and it didn't work, so I cut it up with a hacksaw. I still have a few scraps if anybody wants an (almost) piece of history; )


Oh man...

My friend JP Morgen the frame builder does the same all the time, I never cut anything, i just un-bolt it and make it into something else.

Another sad consequence of this practice, I use to discard Klein fat forks (I left about 20 of them at my shop in colombia) this days go for about $800 a piece, just the forks.


> Building it was a disaster. It was the 3rd frame I ever built, first aluminum. I didn't know what I was doing at all. I had to make my own dropouts (see pic) and 22mm disk mount. Luckily, I had a patient framebuilder to help guide me.


Easton for a 3er frame, dude you are crazy.

I'm surprise the whole thing did not fall apart the day you present the project


> This was one of the last projects I did before graduating from college. Yes, Industrial Design. And I've barely used those skills since. (Hell, I barely used them on this project!)


well you learn how to think in a "Critical way", that needs to count for something


> I'll be starting another tandem soon: Steel 29er, rigid, S&S coupling, kid-compatible, with Rohloff. We were discussing SWB, but it's probably too much difficulty for this one.


So you do make Bicycles as a business..!?!?

or is there a sourse for S&S couplers in the open market..

I used to have two Rohloff that I sold for lack of money after a accident, one on the tandem and I think it made perfect sense, actually I cheat a little and a use a dual front chainring for added gearing choices with a "set" rear dérailleur (as a tensioner only) i works great and it did not add much of anything.

Actually i will like to have the choice of running the 29er wheel at least for the front, but that will complicated things even more at the moment.


> I like your project! I think it'll be great fun.


Thanks you input is very important on the subject


> Let me know what I left out and I'll try to explain.
> 
> 'night!


Good Night to you Death F^Ck>ng Last


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## TandemNut (Mar 12, 2004)

That's very cool! Maybe that's the picture I saw in DR, but I seem to recall the bike being yellow.
Anyway, I'm not an engineer (nor do I play one on TV), but it would seem to my layman's mind that if the weight of the stoker is behind the rear axle, the handling will be adversely afffected. So the stoker would need to be either directly over, or just in front of the virtual rear axle location. Then steering reactions wouldn't be cantilevered over the rear axle.
Just my .02.


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## D.F.L. (Jan 3, 2004)

patineto said:


> ... if I can not make it far better (or at least interesting) thatn any current bike why bother..


I totally agree. It's not always possible to revolutionize a bicycle's function, but there is always an area, even if it is just a small detail, that can be improved.



patineto said:


> So how long was the wheel base..!?!?


I can't find the original drawing, but I think it was around 60" (1524mm)



patineto said:


> I bet on step hills the bike will be almost uncontrolable with the center of mass move to the back. No way In hell.


Never got to find out, but it had bigger issues.



patineto said:


> 24" I don't like but it give me great inside in how much the proportions of the wheels will affect the fit of the bike, specially if is a full suspension running on 26'
> Oh man...


I chose 24s to make the 'packaging' of the desing easier. making a slot large enough for a big wheel in the center of a chassis is never good for structure. I also designed it with the shortest possible front center to help put more weight on the front wheel, explaining the super long stem.



patineto said:


> Another sad consequence of this practice, I use to discard Klein fat forks (I left about 20 of them at my shop in colombia) this days go for about $800 a piece, just the forks...


Funny. I built my 1st MTB around a Prestige rigid fork, headset, and Klein one-piece bar/stem combo I found in a bike shop bargain bin! Bent the bar in half in my first fall.



patineto said:


> So you do make Bicycles as a business..!?!?
> 
> or is there a sourse for S&S couplers in the open market..


Yes, I'm a framebuilder. (I hope that people understand that this tandem was OVER 10 years ago. I like interesting projects, but wouldn't build one like this again). I find my design education to be useful when problem-solving, but I don't utilize all of that training, and there is a lot of structural theory that I.D. didn't provide me.

To buy S&S couplings, you need proof of liability insurance. I believe they will sell 1 set to builders for evaluation, provided those couplers are used by the builder only.



patineto said:


> I used to have two Rohloff that I sold for lack of money after a accident, one on the tandem and I think it made perfect sense, actually I cheat a little and a use a dual front chainring for added gearing choices with a "set" rear dérailleur (as a tensioner only) i works great and it did not add much of anything.


I like the idea of a chassis-mounted transmission for tandems, but using the Rohloff is difficult because it is not designed to be chassis-mounted. It's too bad they don't have a version that can be bolted at the outer shell. One input side and one output side would be great, with a stationary outer shell...

as if my next tandem project isn't already going to be enough trouble; )


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## D.F.L. (Jan 3, 2004)

Another set of pics...


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## patineto (Oct 28, 2005)

D.F.L. said:


> I totally agree. It's not always possible to revolutionize a bicycle's function, but there is always an area, even if it is just a small detail, that can be improved.


Fix it for you
"It's not always possible to revolutionize Nothing" but you don't try you will never know what can happen.

You don't even know if a idea that you share today, will inspire somebody else to seach for something and actually find it..

I think this era of the Internet is amazing, and we need to make sure the information get disseminated as wide as possible so everybody has acess to it.

Reason why I don't care showing idea that may generate a profit or a feasible product on of this days,



> I can't find the original drawing, but I think it was around 60" (1524mm)


Man that is pretty long..

What was the reasoning...wheelie bike!?!?



> Never got to find out, but it had bigger issues.


Like what...!?!?
she was so unstable you did not even get to go to the Hills...!?!/


> I chose 24s to make the 'packaging' of the desing easier. making a slot large enough for a big wheel in the center of a chassis is never good for structure. I also designed it with the shortest possible front center to help put more weight on the front wheel, explaining the super long stem.


Oh I hear you....

is just kind of scary to see how massive the frame needs to be with a 24" wheel when my plan is to use a 26" (and even a 29") plus a rear suspension system..

I guess I need to get the ruler out and measure things more carefully.


> Funny. I built my 1st MTB around a Prestige rigid fork, headset, and Klein one-piece bar/stem combo I found in a bike shop bargain bin! Bent the bar in half in my first fall.


The Klein bars are a beautiful piece of art, but they are not exactly the safest thing around.


> Yes, I'm a framebuilder. (I hope that people understand that this tandem was OVER 10 years ago. I like interesting projects, but wouldn't build one like this again).


On the contrary the fact you are willing to step away from the norm, makes you far more desirable.

i guess is time to goggle your frames and see what you make.



> I find my design education to be useful when problem-solving, but I don't utilize all of that training, and there is a lot of structural theory that I.D. didn't provide me.


I dressage with you on this..
the Industrial design concept (At least the way i experience and live) you become a "Blender" Yes you don't really know much about anything, at least on a deep level, but you learn how to connect the dots and to me that is the most important feature.

ps: I refuse to make pretty lamps, tables and chairs, everything I make is Porpuse build in a almost "Military fashion" (life or death reliable but also minimal)


> To buy S&S couplings, you need proof of liability insurance. I believe they will sell 1 set to builders for evaluation, provided those couplers are used by the builder only.


Great, I did not even know what.
but I alwasys one a set, since they are a brilliant design


> I like the idea of a chassis-mounted transmission for tandems, but using the Rohloff is difficult because it is not designed to be chassis-mounted. It's too bad they don't have a version that can be bolted at the outer shell. One input side and one output side would be great, with a stationary outer shell...


Oh dude *take a look at this pictures I have collect.* yes the Hubs are far from perfect since they are build to be on a rear wheel (at least 135MM apart) but some people like the Lahar designer overcome it in a very graceful manner too.

PLus soon all this G-boxx's will become commun place, well at least I hope.

I have a few link , i just need to look for them,



> as if my next tandem project isn't already going to be enough trouble; )


 Well senor you have a inquisitive mind
I'm sure you wil find a way.


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## itsdoable (Jan 6, 2004)

D.F.L. said:


>


Hum.. that could be a design for a 3-person tandem (tripdem?) with a tandem wheelbase, and a reasonable weight distribution...


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## patineto (Oct 28, 2005)

itsdoable said:


> Hum.. that could be a design for a 3-person tandem (tripdem?) with a tandem wheelbase, and a reasonable weight distribution...


That was my first impression too..

Just make the top tubes a few inches longer (specially the middle one) and make your kid seat at the very back were his body mass is less critical (plus two adults will be forward from the rear axle, making the bike far more stable), plus you can run the seat far lower, or move the cranks far higher since they don't really need to be anywhere in particular as long as they are in the outside of the wheel circumference....

Again I don't think the kids view will be great in front of somebody Badankadunk, but hey at least three people will be riding.


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## D.F.L. (Jan 3, 2004)

patineto said:


> ...Man that is pretty long..
> 
> ...makes you far more desirable....


Tell that to the ladies...

PLEASE!


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## patineto (Oct 28, 2005)

Here are some new outline drawings, sorry I'm being kind of bussy with "Real work" to spend time geeking out with this.

Front end attempt to a Telelever front end, with some nice anti dive features, something I find very useful on a tandem.









Ps: the two circles you see on the back wheel, represent the wheel in contact with the ground and then the wheel at full travel.

This three drawings differ from the early version because I'm not using the "Steeper Shaft" for the stocker cranks and I'm just running them directly to the G-boxx (or whatever system I end up using) trying to simplified the amount of structures pivots bottom brackets, chain and just crap.









I'm trying to make as much space for the cranks and the structure to support them in a very rigid fashion, but for that I need triangulation as opose to big thick tubes, so far not much lucky.









This is a interesting concept, not exactlly a Lawill rear end but somehow similar..

The idea is to have two Parallel arms to keep the chain in constant tension, this well provide a pretty rigid structure able to run a really wide Hub (165mm is my goal) but with out much interface with the stocker cranks since the arms can be run closer to the wheel,, well you will see this better when I make more proper drawings.









More to come when I have some more time.


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## patineto (Oct 28, 2005)

Some new pictures near the new house.


















Detail of the dual brakes, Yes the V-brakes are mounted in the back of the forks not the front.


















One thing is for sure, Tandem's make for the best dog strollers.


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## patineto (Oct 28, 2005)

Well I'm not using the Stocker Stem, let put it to good use....

So my IBIS Tandem has lower eyelets but none at the top to mount a rack..









Yes I know you can just use the seat collar Quick release to mount the blackburn stainless arms but then you end up with super long and flexible struts.









Well this way everything is super rigid and nothing moves at all.









Please Don't pay attention to the stainless brackets, I'm making better ones soon.









In this case I use the original IBIS stocker stem (I have a Adjustable "Boom stem" now) with a small shim (from 27.2mm to 28.6mm) since I have a suspension seat post that is 27.2mm, but i was running the stock seatpost I just need the stem.

I take better pictures soon.


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## [email protected] (Dec 2, 2006)

DrewM said:


> I had a few thoughts but after re-reading the thread a couple of times you guys are WAY out there so I went back to day dreaming and came up with a couple thoughts:
> 
> Re. Putting the stoker right over the rear wheel. ("Move the rear wheel under the stoker. The stoker cranks would be centered on the rear hub. If you used an internal hub like a Rohloff, the
> stoker cranks would be tied directly into the rear hub.")
> -D


See pic! Pardon the language.

http://www.taobao.com/view_image.ph...Dg0M2NhYTcyZmM2ZjgyZDgyZDhkODg4MTE=&version=2


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## D.F.L. (Jan 3, 2004)

A few challenges here.

I already have a sketch of a tandem with a hub-centric crank and if I get time, ever, I'll start on it. Lots of technical challenges and cost.


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## killerisation (Nov 26, 2008)

BB thru rear hub? Check this out... https://www.mtbtr.com/uploads/932Z18.JPG


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## reamer41 (Mar 26, 2007)

killerisation said:


> BB thru rear hub? Check this out... https://www.mtbtr.com/uploads/932Z18.JPG


Finally! A tandem we could wheelie!


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## ebnelson (Oct 30, 2006)

Better get the stoker a suspension seat post for that ride though, ouch!


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