# 650b full suspension



## adarn (Aug 11, 2009)

*650b full suspension (Not 650b full suspension)*

Hah! You thought I'd already made one. Sorry.

Now that I have your attention though, who's done it? Or put in some research into it?
I'm looking for a real challenge of a summer project (yeah, I'm starting to plan it already), and I've really been wanting a FS bike for a while. 650b seems like the way to go. I would hope in the 4-6" of travel range.

Could a Ventana rear end be used? How do I get one of those? gut another bike? go from scratch? How the hell does that FS thing work anyway?

Any thoughts would be super appreciated. Thanks!


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## TrailMaker (Sep 16, 2007)

An ambitious project;

As far as the rear triangle is concerned, I'd be very surprised if you couldn't simply call Ventana and order one. I'd be further surprised if you couldn't get at least a few small morsels of advice there as well. As I've heard, the owner is pretty legendary for being a right-there-and-ready kind of guy.


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## shirk (Mar 24, 2004)

Pretty sure Ventana does not sell direct to amateur builders. Need to prove insurance. Walt might chime in as I think I got that from something he has posted.

Go single pivot and fab everything yourself.


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## Walt (Jan 23, 2004)

Ventana only sells to insured "professional" builders. That said, you can score broken/used/old Ventana frames all over the place and pull off the rear end.

I've written about how to build with these rear ends pretty extensively on the blog if you do some searching around. They offer a lot of flexibility in an off-the-shelf product, so you get a lot given that you don't have to fab much up yourself. That said, you can do it all yourself (especially single pivot bikes) in a variety of ways and that may be more fun if you're building for yourself and don't mind some experimenting.

-Walt



shirk said:


> Pretty sure Ventana does not sell direct to amateur builders. Need to prove insurance. Walt might chime in as I think I got that from something he has posted.
> 
> Go single pivot and fab everything yourself.


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## Syltmunk (Jan 20, 2008)

Build your own rear triangle in steel, that's the fun part of the project, just finished a 29er fs all steel and it works well, you can do it, keep us posted.


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## adarn (Aug 11, 2009)

Walt, I've seen your blog posts and they're definitely a good resource.

I'll definitely be doing a lot of research on the front end here. 

Syltmunk, got any pics?

Adam


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## Walt (Jan 23, 2004)

*Worthless!*

...without pictures, that is! Share the wealth, man!

-Walt



Syltmunk said:


> Build your own rear triangle in steel, that's the fun part of the project, just finished a 29er fs all steel and it works well, you can do it, keep us posted.


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## Syltmunk (Jan 20, 2008)

adarn said:


> Walt, I've seen your blog posts and they're definitely a good resource.
> 
> I'll definitely be doing a lot of research on the front end here.
> 
> ...


Here are some pics of my all steel 29er, have about 200 miles since finished, no issues so far works great.


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## adarn (Aug 11, 2009)

OK, so I'm finally starting to dive into this project, and I have a lot to learn...
To be honest, I know almost nothing about suspension, so I'm hoping to maybe get some tips from you guys.

Here is what I am thinking at this point:

I drew up this sketch in sketchup mostly to get the idea across of what I'm thinking and hopefully get some feedback








So for gemoetry I'm thinking:
STA: 70
HTA 69
ST C-T: 450mm
ETT: 635mm
CS: 420mm
HT: 120mm
BB drop: -10mm unsagged

I was thinking of 6" of travel, but I'm still on the fence about having that much.

I was planning on using a 1" headset for the pivot, 7/8" x .035 straight gauge for the bent section of the rear triangle and 5/8" x .035 for the straight support.

I think that my main concerns with doing the rear triangle this way are 1. actually bending the tubes, and 2. having to attach the shock to the rear triangle at the bend, would that be an issue?

I plan on using mostly TT bmx tubes on the front triangle. 34.5mm ST so I can run a 31.6 dropper post and a 44mm HT. I will probably drill a hole right through the DT for the pivot, and possibly sleeve it too, or something else to reinforce it.

The next thing I need to figure out, and really need help with is pivot placement. Any tips on that? (sorry, I know what kind of question that is).

Oh, also, the whole thing is gonna be fillet brazed, which I find kind of funny, but it's what I've got!

Anyhow, I'm excited to get working on this and even more excited to ride it!

Thanks,
Adam


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## Sick Sticks (Jan 18, 2008)

*Suspension design*

Adam,
I've done a fair bit of scouting around on this very subject and these are the two best resources I've found. The Linkage bike suspension design software is unbelievably good particularly for the price. They have a demo model so you can get an idea of what you are getting before you buy.
Linkage Bike Simulation Software - News

If you combine that with reading all of the Joe's Corner blogs on the Santa Cruz site (many times) you may begin to understand what all of the graphs mean and what you are shooting for in your design. I think this is a cool thing that Santa Cruz did because most companies aren't that forthcoming. There was a blurb like this on the Yeti site once but they pulled it down. Start with this one:
Santa Cruz Bicycles COMPANY

The guy that is the head designer for Banshee Bikes has his masters thesis posted on-line. He used the Linkage software to design their latest downhill bike...and got a masters degree for it. I don't remember the link for that but I bet you could find it.

It also helps to have one of the world's most experienced bike suspension designers living in your town, Doug Bradburry, that you can corner and force to divulge all of his worldly knowledge.


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## adarn (Aug 11, 2009)

Thanks Sick Sticks,

I just read all of those articles on the Santa Cruz site and it's certainly some good info, it'll take some time to soak in.

I'll have to look around for that thesis too, that could be neat.

Thanks!


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## shirk (Mar 24, 2004)

adarn said:


> OK, so I'm finally starting to dive into this project, and I have a lot to learn...
> To be honest, I know almost nothing about suspension, so I'm hoping to maybe get some tips from you guys.


Copy a Santa Cruz Heckler.

Dig into Walt's blog, he has some info deep in there about his single pivot and what he would do different and what he learned.


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## shirk (Mar 24, 2004)

JMc003 Photo Album - Pinkbike

There is a massively long Pinkbike thread that sometimes has some useful into. You have to weed out the drawings of never to be built huck machines with 76 inches of travel and made with steel girders but some good pops in like above.


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## Fix the Spade (Aug 4, 2008)

shirk said:


> You have to weed out the drawings of never to be built huck machines with 76 inches of travel and made with steel girders but some good pops in like above.


That's the best use of a Prophet swing arm I've seen in ages.


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## adarn (Aug 11, 2009)

Sweet! Thanks for the info guys!


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## cschaafsma (Nov 17, 2012)

Adam,

Your drawing looks a lot like a design I've been kicking around for awhile now. Crazy. I think we've both been looking at the Heckler a bunch. One thing I like about the heckler design is the simplicity and it would be easy to get the clearances around the rear wheel with shortish chainstays.

An interesting example of a steel full sussy is the Cotic Rocket. the Product of COTIC cycles : droplink ROCKET You might also be interested in Cy's take on their droplink design What is the "droplink" suspension platform? From the bike geek corner of COTIC cycles and why they went with steel Why use steel to make a full-suspension bike?

With the single pivot designs brake jack can be an issue depending on how you roll. I've noticed this as a rider but it was never horrible to me and I felt the design worked better in other areas compared to a typical 4-bar design or SC's VPP. Granted my background is in moto before bikes where brake jack is huge. I have not ridden a split pivot or Trek's ABP (another split pivot design), both look very smart to me. This old thread has some good nuggets on brake jack that initially helped me understand more what was happening. "Brake jack" - an explanation.

I've also seen some people do some crazy kinematics analysis using solidworks if that's something you have access to.

Hope that helps! I think there needs to be more full sussys in steel!


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## TrailMaker (Sep 16, 2007)

FWIW;

I've owned a Heckler since 2005. I don't ride it anymore since the Niner and now the Fatbikes, but it was and is a great bike. I put a lot of rough wet miles on that thing, and it still gets the job done just fine. It's hard for me to think back now and realize I used to ride such a "small" bike as that (even though it's an XL), given the modern bikes that actually fit me, but it is a great machine. Still has the original bearings in the swing arm even. Bought a set of Enduros but never needed them!

Not one single complaint about the performance of the bike, other than not really fitting the size of it. It is a great platform to use for a model. They are not legendary for nothing!


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## TigWorld (Feb 8, 2010)

Those single pivot bikes really only have one thing going for them - ease of construction. To get them to ride acceptably both up and down, you will need a highly tunable shock or the ability to revavle your own shock. You have some slight shock rate tuning options based on where you mount the fixed end of the shock relative to the arc or the moving end, but this affords only a very minor change in end or beginning rate. Design around either a cane creek double barrel (fairly adjustable, but potentially not adjustable enough) or perhaps an RS Monarch where you have the full service manuals, valving options and air can choices to dial the suspension in.

A single pivot also puts all of the stress on the one pivot. The downtube needs to be massive to counteract the forces. This is achievable in alu with oversized and non-round section tubing, but in steel can you get suitable tubing that won't make the bike too heavy? Any flex in that pivot will result in rapid wear of the shock bushings and compromised performance of the shock. Any angular irregularities in shock activation will result in lots of stiction.

I'm just wondering if a single pivot design is a good choice for a steel front triangle?


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## Walt (Jan 23, 2004)

*Yes*

Having built lots of steel FS bikes, I can say that it works just fine for both front and rear triangles.

Single pivots ride great with basically any modern shock (I have been on professional podiums on them in the recent past) and they are light, stiff, have great reliability and require very little maintenance. They are killer when done well and that's why they are still used and probably always will be.

Moreover, the OP is doing a first suspension bike so even if you disagree with al of that its still the best option just for ease of design/construction.

Walt



TigWorld said:


> Those single pivot bikes really only have one thing going for them - ease of construction. To get them to ride acceptably both up and down, you will need a highly tunable shock or the ability to revavle your own shock. You have some slight shock rate tuning options based on where you mount the fixed end of the shock relative to the arc or the moving end, but this affords only a very minor change in end or beginning rate. Design around either a cane creek double barrel (fairly adjustable, but potentially not adjustable enough) or perhaps an RS Monarch where you have the full service manuals, valving options and air can choices to dial the suspension in.
> 
> A single pivot also puts all of the stress on the one pivot. The downtube needs to be massive to counteract the forces. This is achievable in alu with oversized and non-round section tubing, but in steel can you get suitable tubing that won't make the bike too heavy? Any flex in that pivot will result in rapid wear of the shock bushings and compromised performance of the shock. Any angular irregularities in shock activation will result in lots of stiction.
> 
> I'm just wondering if a single pivot design is a good choice for a steel front triangle?


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## adarn (Aug 11, 2009)

Hey thanks guys, In response to all of that...

Yep, I'm pretty much going to copy the heckler straight up with a few adjustments to fit me better.

As Walt said, this is my first time building a FS bike, and it's really an experiment. I'd love to have a fun bike to ride, and I'm confident that I will, but I'm sure it will have some things that I can learn from.

I'm using steel because it's all I have the tools for and because its cheap and easy to work with. 

As far as brake jack, pedal bob and those things, I would definitely be interested in learning how to minimize those things (the SantaCruz articles had some good info on that), but I understand that I'm building a single pivot bike and it won't ride like a hardtail.

I'm working on some more final drawings now and my tubes are on the way. This is going to be sort of a side project, but I think I should be getting into it soon here.


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## shirk (Mar 24, 2004)

Don't worry about brake jack, or get lost in the fact that there is no linkage mumbo jumbo. 

I currently ride a single pivot and it shreds.

A good fork and tires will mean more on the trail then as long as the shock tune is't way off, the good thing is it's easy to get the shock info for a Heckler.


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## cschaafsma (Nov 17, 2012)

Sounds awesome Adam! When I get a design flushed out of my single pivot I'll be sure to post it up here for fun. Just checked out your site... are you in Boulder? We should ride sometime.


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## adarn (Aug 11, 2009)

Nice, I'll look forward to seeing it. I am in Boulder for the summer... always happy to ride.

As for the bike, I went ahead and bought that linkage simulation software and I've been having some fun messing around with it. What I've found though is I'm going to have to figure something out to get my seat tube to clear the tire. I don't have access to a tube bender, so I guess my best option is to just stick the ST onto the DT like this program conveniently lets me do.

I've also settled for a measly 140mm of travel. I was going to go for 150, but without bending the ST it seems like that would be a major pain. Also I don't need 150.

With it set up this way I only get 21mm of chain growth, which doesn't seem terrible, the leverage ratio gets up to 2.76, which I understand to be not terrible.

Anyway, I'm going to spend some time thinking this through more, but I'd kind of like to try building something soon and just seeing how it goes. Tubes are in the mail, so I suppose that's going to happen soon.









-Adam


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## shirk (Mar 24, 2004)

What is the deal with the 68 degree sta?


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## adarn (Aug 11, 2009)

shirk said:


> What is the deal with the 68 degree sta?


That was to compensate for moving the ST so far up the DT, effectively it should be 70.


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## shirk (Mar 24, 2004)

70 is going to be pretty crappy, once sagged it's going to feel like you are way over the rear wheel.

Go 73-74.

Another great single pivot bike to copy geo from. I have the previous version of this, it's a touch steeping in the HA at 67 and I think the sta is 72.7. 
Xprezo - Fabrication 100% canadienne


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## Eric Malcolm (Dec 18, 2011)

Hi Adam

Are you aware that you can use a Down-tube for the Seat stem from Nova Cycles that is 34.9mm, 15 degree bend. At your length of seat tube, you would have 0.6mm wall, so it needs a sleeve. Seat stem: using a dropper post @ 31.6mm, you will need a 1mm walled sleeve. 

NOV-CODT-B35-969

This will allow you to attach to the BB shell and clear the tyre.

Eric


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## adarn (Aug 11, 2009)

shirk said:


> 70 is going to be pretty crappy, once sagged it's going to feel like you are way over the rear wheel.
> 
> Go 73-74.
> 
> ...


Oh dang! that's why I need you guys. Yeah, I generally like a slack STA due to my ridiculously long femurs, but you're right about the sag, I think I'll steepen that up a tad.



Eric Malcolm said:


> Hi Adam
> 
> Are you aware that you can use a Down-tube for the Seat stem from Nova Cycles that is 34.9mm, 15 degree bend. At your length of seat tube, you would have 0.6mm wall, so it needs a sleeve. Seat stem: using a dropper post @ 31.6mm, you will need a 1mm walled sleeve.
> 
> ...


Eric,

That's a great tip! Thanks.
Although, what would I rather have... a sleeved seat tube, or a floating bottom bracket?


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## Eric Malcolm (Dec 18, 2011)

Adam
To clarify the sleeve, the 34.9 Tube needs an outer sleeve, used with a 1mm walled inner sleeve. The ideal seat stem size is 33.6mm.

If it was my build, I would prefer a solid BB to a 'noodly' one. And I would be radical and do a steel inner sleeve machined with a shoulder to suit the seat stem and silver it in.

Eric


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## adarn (Aug 11, 2009)

Yep, I hear ya Eric,
I think I'm going to go that way. I just got a lathe, so I suppose it will be a fun job for that.

While I'm posting here, I've looked all around for tech drawings of FOX forks and can't seem to find any. I just need that AC length for the 150mm Talus 34. Can't seem to find it...


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## shirk (Mar 24, 2004)

Should be about 540mm at 150mm of travel.

The 160mm is 550mm.

My old 150mm Talus 36 is listed at 545mm.


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## Ciclistagonzo (Dec 10, 2001)

Are you planning on using a Front Derailleur? If so, check your clearance to the swingarm and think about how you plan on attaching it.


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## adarn (Aug 11, 2009)

Nope. Not a big fan of those, I'm gonna stick a Chain guide mount on there and run one of those, I don't think I'll need that much clearance for one.


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## adarn (Aug 11, 2009)

Sweet, Thanks Shirk!


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## afwalker (Apr 26, 2012)

I can roll a tube for you, I just have the harbor freight but with the swag offroad dies. Has to be non-heat treated, so a TT versus, or a nova like the ex butted 28.6 EXTERNAL BUTT SEAT TUBE 1.2/0.6/0.9 x 580 :: EXTERNAL BUTT SEAT TUBES :: ROUND TUBES :: MAIN TUBES :: TUBES STEEL :: Nova Cycles Supply Inc.
cheers
andy walker


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## shirk (Mar 24, 2004)

Orange has a pretty good drawing of their frames on the website. I have not checked if it's to proper scale, but I assume it is.

The Five is known to me a great riding bike. Some small tweaks to account for 650b and it's another great frame to model you bike after.

I am working on modeling a bike after the Alpine 160.

1 3/4 0.049 straight gauge for the downtube
TT 34.9 seattube
TT 44mm headtube

Undecided on a .9/.6/.9 versus 34.9 toptube or 1 3/4 0.035 straight gauge

Also still trying to figure out what gauge and diameter to use for the rear triangle.

For the main pivot I plan to use a 31.8 headtube then use a 25.4 steer tube as the pivot axle. This way I can use two upper cups from a 1" headset as bearings. I learned this from digging in Walts blog.

Just need to continue my braze practice and get a couple hardtails under my belt before going from concept/planning to reality.


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## Walt (Jan 23, 2004)

Exactly. These days asking about where the front derailleur will mount on a mountain bike is like asking where the canti hanger will go. I have literally not sold a single mountain bike with a front derailleur in something like 10 months. 

-Walt


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## adarn (Aug 11, 2009)

Andy,

That's super generous of you, thanks so much! I may have actually figured a way to go with a straight ST, which I will touch on later, but I may also take you up on that.

And Shirk,
Very cool. I'm planning on the two headset tops as well, I'm using a butted top tube and not really worried about it. 

My rear triangle is going to be 7/8" x .035" straight gauge for the upper part and 5/8" x .035 for the support, which kind of seems overbuilt to me, but I suppose we'll see.


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## afwalker (Apr 26, 2012)

I have the 1 1/8 and 1 1/4" swag dies, may have to add the 1.375" anyway Here's 20mm on the ex butted nova ST.
cheers
andy walker


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## adarn (Aug 11, 2009)

*Well... Here's a change...*

I've changed my mind. I just finished building a frame for a buddy with 650b wheels, my first experience with them. At first I didn't have a wheel to stick in the frame, so I was using a 26er to check things out, but it seemed a little big. I measured it, and it was 27".

I guess I new this already, but just hadn't really thought about it.

So I've decided to build this thing as a 26er. It's going to make actually building it up soooooooooooooo much cheaper because I can buy stuff off of friends and I'm honestly starting to think that this 650b thing is pretty dumb (Start argument: take it to another thread if you want).

This will also allow me to not bend any tubes, and if I build something super shitty, I'll have spent less money which is really great.

Anyhow, I'm hoping to get the front triangle mitered tomorrow and then I'll start working on the pivot and maybe the rear triangle. Updates to come... some time.


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## TrailMaker (Sep 16, 2007)

Well...

Just because the rims don't measure what they are called - they rarely do by the way - you can't argue with the physical merits of the "27/29" inchers. You simply make your choices. Going with a more economically feasible build makes perfect sense from that standpoint, if that is an important consideration. Can't argue that, although the only thing really different is the wheels & tires. Probably, just getting started and figuring out full suspension in the easiest fashion makes the most sense. Save the fancy stuff for when you've got it all doped.

Watching......


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## Walt (Jan 23, 2004)

Given the price (free, if you have as many bike dork friends as me) of 26" parts these days, and given that I happen to know the OP is a starving college student (who builds crazy awesome stuff and whose talent I am jealous of) I'd say 26" makes perfect sense.

Honestly having ridden 26 vs 650 head to head I can't say I can tell much of a difference anyway.

-Walt


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## xy9ine (Feb 2, 2005)

shirk said:


> I am working on modeling a bike after the Alpine 160.
> 
> 1 3/4 0.049 straight gauge for the downtube
> TT 34.9 seattube
> ...


dude. you building bikes? tres awesome!


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## afwalker (Apr 26, 2012)

xy9ine, Thanks for pointing out so my brain could read the 2nd time, The 1" steerer tube with headsets for bearings. Aha, that's a great idea Walt used. Hmmm...
cheers
andy walker


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## shirk (Mar 24, 2004)

xy9ine said:


> dude. you building bikes? tres awesome!


Currently teaching myself how to braze.

Couple hardtails first them some sort of straight gauge fs beast (beast in over built weight, not some DH huck monster).


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## adarn (Aug 11, 2009)

Wow, thanks for making my day Walt! Dang that's a nice thing to say haha.

But yeah, I do happen to be in that starving college student position (or at least I will be after this bike) And I think I have enough biker friends to do it for realllly cheap in 26. So that's good.

And I'm glad to hear a more trusted opinion on my observation of the 650 thing.

Adam


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## adarn (Aug 11, 2009)

*Front triangle*

Alright, well I finally have some progress to report, or at least I hope.
I brazed up a front triangle, but I think I'm stuck here for a little bit. Here is where I'm at:


















Looking pretty good I suppose. My worry is here though. I was thinking of eventually using a King headset for my pivot, so I bought a couple super cheap ones with about the same stack height to start off with. After sticking them in the pivot with the tubes that I'm planning on using to clamp on the rear end, things are looking pretty wide - 4.5" or 115mm wide.










I don't have my cranks in hand yet, so I'm not sure if I'm screwed, but what do you think? I measured some other cranks and I think I should be OK (doesn't mean I won't hit my heels on stuff) but it just doesn't feel right.


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## Eric Malcolm (Dec 18, 2011)

Re: chainline vs pivot.

I measured my E-Thirteen triple and I would suggest that it is representative of cranksets in general, and at 115mm width, it looks like you could only use the outer chain ring only. That would not make for a tidy 1 x anything arrangement.

Now that is all in place (welded), I presume that the pivot is press-fit 30mm for the head cups? You could in that case make an internal spacer and use sealed cartridge bearings 6903 series, 17 x 30 x 7mm - pressed in. Machine up for yourself a 17mm hollow pivot shaft and you will have the clearance needed.

Something to consider.......not as good a bearing design, headset bearings would be better, but your options are limited.

The build looks really good with plenty of bracing/surface area keeping the BB and pivot rigid.

Eric


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## adarn (Aug 11, 2009)

Thanks Eric,

Yeah I was thinking just pressing in bearings would be my other option. I think I'm going to go ahead and find a crappy, representative crank set at the bike co-op and check it out, I think I could be OK. 

In the mean time I'm going to go ahead and order my stuff. I picked up a fork and wheels today. Gettin' serious money wise about now, so I hope this works.


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## shirk (Mar 24, 2004)

Curious why you moved the pivot point vs the original drawing or bikes like Heckler/Orange. 

Can you go narrower on your collars that are going to clamp to the pivot shaft? Perhaps squish the ends of your swing arm tubes to gain clearance.


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## adarn (Aug 11, 2009)

Shirk, the pivot is in exactly the same location as the heckler and that is why I moved it there. I borrowed some 83mm DH cranks from a buddy, I'm gonna go check those out in a minute here after a recuperate from a long day of riding (and crashing - yeesh).


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## shirk (Mar 24, 2004)

Must just be optics, I thought it looked like you moved is back towards the seat tube.


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## adarn (Aug 11, 2009)

Hmmm, nope.

Well so the cranks clear no problem, chainring clearance on the other hand... that's a no go by a good .30". Bummer. I think I'm going to go for internal bearings. I'm sure there's something that's 33.9mm OD with a reasonable axle. i've got some tube I can turn down a tad and braze into the pivot tube. I might still use star nuts on the end of my axle to keep things in, maybe i'll turn some giant end caps to keep things clean in there, or heck, even use washers. ****.


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## Eric Malcolm (Dec 18, 2011)

Adarn

What O/D is the pivot shell that you've brazed in there? If you could get it reamed out to 37mm, you have the choice of 20 or 25mm axle using 6904 (20mm) or 6805 (25mm) series bearings. If you can manage only 35mm bore, you are locked into a 17mm axle. It would be a special bearing to have an O/D of 34mm.....

Eric


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## adarn (Aug 11, 2009)

yeah, I could only really use a 5/8" axle with the 33.9mm bore i have, it's a HT for 1 1/8" steerer. I actually think I might be able to get the current set up to work. I'm going to go ahead and try, worst case I'll resort to the internal bearings, but I may as well go ahead where I'm going now.

I was checking out Walt's single pivot project digging back through his blog. I might end up going with .75" x 1.5" square tube like he did for the uprights of the swing arm. I think I can make my axle sleeve/clamp things the thickness of the inside of that tube (.654"). then I'll miter the square tube so that the edge of the clamps are exposed and the end caps can rest in there. It looks like this should clear the chain ring with not much room to spare.

Boy am I learning a lot on this project! Probably won't make more progress until this weekend, but I'll update when I do. In the meantime, any and all advice is welcome...


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## TrailMaker (Sep 16, 2007)

Hey;

It doesn't take much detail to make my head hurt, but my advice would be to sit back and stare at it for a while. Look some more at other production and custom builds for ideas. There are likely a zillion ways to accomplish what you want, but the slickest of them usually do not occur on the first thought, for most people. You've got some ideas from others, and that which is in your own head already. Let that all perk for a bit. In some cases, inspiration comes very quickly after you find that you were wrong the first time (like my Kroozer DO-to-CS mitering style, which came like a flash, within minutes of discovering initial failure).

Most of the time, at least for me, it takes time for that brightest light to come on, and it generally starts as a soft glow before it becomes that blinding light of ultimate clarity!

-------------------------------------------------

Never really gave it much thought, but my first impulse is to do something with the parts and characteristics of an ex-bearing crank setup!


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## toby_g (Jul 29, 2008)

mmm, looks pretty tight in there.

not really put much thought into this, but i did think this when i first saw the head-on image:

I recon you could face a few mm off each end of the pivot tube, probably 3-4mm each side, depending on how the cups interfere with the suport post. File the brass down a little to match. I also had a look at one of my spare headsets, and depending on the make up of yours, you could probably shed those plastic dust caps, and replace them with a thin washer. just as long as you have the tapered split ring (that one that interfaces between the bearings and the steerer), you should have good contact, and no play. getting the right washer to fit might be tricky, but I am sure you could find something in the spares box, or fabricate something. That will gain you a few more precious mms.

if the above still doesn't give the clearance required, you can still go down the bearing/17mm axle route later.


Hindsight is a wonderful thing, and it might have been wise to go for a 41mm ID tube, and a pair of Integrated headsets (or 44mm and some ZS44 headsets)


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## shirk (Mar 24, 2004)

Access to a lathe? Spin up new dust caps that are shallower.

Are the lower cups a lower stack height?


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## adarn (Aug 11, 2009)

TrailMaker-

Great advice. I was pretty frenzied when I posted last and I've given it some more thought. I also had a chance to look at a lot of FS bikes to day to try and source some inspiration. But yes, I do think giving it time is key...

And Toby,
I already have the pivot tube faced into my fillets, so no more there. the dust caps are taking up a good 3mm more than they need too, but it looks like with this low quality headset, taking them off would be a lot more trouble. As you said if this doesn't work I can always go to internal bearings. I think I'll pursue my smaller clamps, welded inside of the vertical swingarm and see where that puts me.

Thanks all!
Adam


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## TrailMaker (Sep 16, 2007)

Inspiration is a funny thing....

I still marvel at my DO mitering scheme for the Kroozer. Yes... I am marveling at myself. I don't really think it is always a bad thing to be impressed with what you do. That's where enjoyment comes from. Let's be honest. As has been said by more people than just me, that layout is brilliant, simple, elegant. No false modesty here, for it came upon me in a total flash, as if from some other realm. I fiddled and puzzled and agonized over the original layout, endlessly, and reached that point of despair you get to when the reality that is staring you in the face lets your concept down flat. In a relative instant thereafter, the solution I came up with just landed in my brain so much by surprise that it doesn't even feel like it came from me... somehow. That's why I am able to describe it as if it were a third person experience. Just like that, and shazzam!

All this by way of saying you never know when inspiration will strike, and just how inspired it will be. Hopefully for you, the one you now seek will not show itself in the process of frame #21!


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## Walt (Jan 23, 2004)

Hey Adam -

FWIW, I actually used a BB shell and Euro BMX BB (for a 22mm spindle) on mine back in the day. The Euro BB's are nice and low profile so total width isn't an issue and you can just machine down a crank axle (BMX cranks are usually 3-piece). Super easy. I also used a bit different pivot location, though. 1" (or 1 1/8) headsets will work great too but not where you've got your pivot. 

Honestly I would go ride, think about it for a few weeks, and maybe start over. There are probably ways to salvage it but you're just going to end up wanting to redo it anyway, so why not save yourself a lot of bashing your head against a wall and start fresh?

-Walt


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## Crispy01 (May 4, 2011)

Hey Adam, 

Would forgoing the dust cover and using sealed bearings give you enough room?
From what I see you should save about 5mm of space.


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## adarn (Aug 11, 2009)

Hey Walt,

That hurts to hear a lot. I really didn't think this through enough (like I said, learning a lot on this one). 
The sad reality of building a bikes is that the frame is pretty much the cheapest part when you build it for yourself. I think I'm going to try it out and see how it goes. I suppose worst case I could weld some stays onto the back of this and make a DJer and then I'll have all the components for FS#2.

I am sure there will be a lot of head bashing, but that's really how I learn best and I think it can help make the second one better.

And crispy, It's going to take some modification, but tat is part of my plan now.


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## dr.welby (Jan 6, 2004)

That's an 1 1/8" headtube for the pivot housing? That should be a 33.95mm ID, which is pretty close to the inside dimension of a bottom bracket shell anyway (33.6-33.9 mm). So you could tap it and run Euro bmx cups, or maybe even turn the threads off the cups and press fit them in.


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## adarn (Aug 11, 2009)

*Good news everyone*

I got a chainring, lost the giant dust caps and shrunk my clamps.
This looks good enough for me.









Added bonus: the pivot acts as a chain guide, haha.


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## Walt (Jan 23, 2004)

So you're going to run an outboard ring only? You could easily do an offset rear end to get a nice chainline (and end up with a dishless rear wheel, bonus!)

Let us know how it rides!

-Walt


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## Eric Malcolm (Dec 18, 2011)

Following on from the head tube / BB diameter part of this adventure.

I re-call some time ago coming across an advert by a builder who converted older 26" geared frames over to eccentric BB single speeds by clamping the frame on a milling machine and holesaw cutting the old shell out and brazing in the larger diameter Eccentric. Very neat and tidy. This could be done here.

A thought.. Do you file your mitres or machine cut? A BB cut would take care of the problem, then fit a larger shell.

Eric


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## adarn (Aug 11, 2009)

That's the plan Walt. This frame is just full of Bonuses!

I'll be sure to keep you all updated.

And Eric, that just sounds harder than starting over, which I plan to do anyway. This front triangle is destined to become my DJer, I'll rebuild this thing in the winter.


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## Feldybikes (Feb 17, 2004)

Walt, you used a 19mm BMX Euro bottom bracket, not 22. Probably would work with the 22, but I guess the bearings would be smaller.

Also, I think it was mentioned to use 2 headset top caps at some point. This would be nice from a symmetry perspective, but I think you might have trouble ever getting it apart since the split rings would be wedging in opposite directions.


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## adarn (Aug 11, 2009)

Alright, well I'll just put this hear for now.









I've only taken it around the neighborhood and a couple of the "cyclocross" trails near my house, but so far, the suspension actually feels really good. Very minimal pedal bob, a bit of brake jack, but I can stand up and push pretty well and it feels great pumping and going off curbs and stuff. I just wish I had gone with a slacker seat tube (it's 72, maybe 70 would have been better, saddle is maxed out) and maybe a little longer, although I'm running a 50mm stem, so that may explain some of that. heaps standover is good.

The chain line sucks mega hard though - like reallllllly bad, and it probably doesn't help that the drive train is a bunch of mismatched parts from the bike co-op that I got for $20. I think I can loose a spacer on the drive side, but boy is it hard to keep that chain on. I wipped up a real ghetto chainguide and we'll see how it performs. I can only use 3 of my 9 gears now (partially because I'm using a 6 spd shifter)

I'm going to ride it at work tomorrow. Hopefully it doesn't explode while I'm out coaching! I'll post more when I see how she does.

Adam


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## adarn (Aug 11, 2009)

Sick.
This bike is the most fun bike I've ever ridden.
It has me wondering why I've been riding rigid SS for so long. I love how it climbs and I love how it descends even more. Geometry is pretty dialed. I'm thinking about a setback seatpost for it though. Shoulda gone more slack. but yeah, time to buy real parts because I am liking this thing a lot.


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## TrailMaker (Sep 16, 2007)

Well...

What more can you ask for?

:thumbsup:


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## shirk (Mar 24, 2004)

Bump.

How is the bike holding up after more riding?


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## adarn (Aug 11, 2009)

Hey, 

Thanks for asking, Shirk.

Well Pretty good. It's a blast to ride. I love descending on it. Yeah, this thing is awesome to descend on. I'm happy with the ride. although I would have slaked my ST a degree or two more and raised the bottom bracket a cm if I did it again.

I had an incident last week though. I had broken my chain the previous ride and had to take a link out. The next ride I shifted down to climb and sent the derailleur into my spokes and bent it pretty good. ouch. Not discouraged, I figured I'd hike up a ways and go down chainless while waiting for my friends. I didn't realize that it had gone back into my spokes on the hike up and I ended up hopping on an breaking the derailleur and bending my hanger pretty good.

So It's been like that for a while now. It's fixable but I just haven't had time yet with school starting up.

But as far as "framebuilding issues" I'd say this bike is working pretty darn well.

I'm not sure I'm good at describing what's going on with it, but if you have any questions I'd be happy to answer them.


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## TLKD (Mar 29, 2010)

Curious to ask about flex of the rear end. With the seatstay tubes overhanging (non triangulated) a couple of inches. How does this feel ? What tubes are they, 7/8" x .049" ?

I don't know if I'm re-opening a debate here but I guess this debate was more around a chainstay bridge than a seatstay bridge... I'm asking anyways : did you not put a seatstay bridge because it wouldv'e come in contact with the seat tube when suspension is compressed or you just didn't do so because you didn't need one ? I understand the chainstay bridge to be useless because the tubes are usually heavier duty, but I have a hard time looking at seatstays without bridge.

Keep up the good work. Let us know.


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## adarn (Aug 11, 2009)

The "seat stays" are 7/8" x .035

I *think that I can feel some flex in the rear triangle, but to me it feels good. I will probably add a bridge at some point but I think it will be in front of the seat tube and not behind.

When I'm climbing with the shock locked out I feel a little bit of flex, but nothing unreasonable, in fact it's much stiffer than I expected. I'm sure there's a decent amount of flex when I'm crushing on it, but I don't really care about that on the descent.


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## shirk (Mar 24, 2004)

Hey Adam any way you can fix the broken image link? 

I am planning out my build and wanted to have a look at yours again for reference.

Now that you've got more time on the bike anything you would change or do different?


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## adarn (Aug 11, 2009)

Hey Shirk,
Sorry about that. I updated my blog/site and accidentally deleted everything. Maybe let me know what you would like pictures of and I can take some new ones?

The things I would do differently are REALLY think about the drive train, i.e. chainline and chainring clearance. I had issues with that where I placed my pivot.

I would try to make the pivot as narrow as possible to make the chainline better and more chainline clearance. I would also try to make the pivot as wide as possible to make the rear end stiffer (see what I did there?)

That's about it really. It's a heck of a fun bike! and not nearly as hard as it looks. Good luck!


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