# 180mm VPP carbon design



## bluechair84 (Sep 30, 2008)

Well, I've been asking questions, it's about time I shared what I'm up to:









The design brief is to have a rearward axle path to improve bump performance whilst resolving the issues associated with chain growth. For a long time, the design was actually based around a gearhub located in the frame, but I couldn't figure out a cost effective way of driving the wheel without copying what Zerode have done before.
Most suss designs appear to have terrible squat characteristics, on paper at least. This design creates anti-squat in the first 75mm, after that the suss isn't restricted by chain growth. I'm looking forward to seeing if this design performs as intended!
Finally, the jackshaft (concentric pivot location of the two chains) can be adjusted downwards which increases anti-squat - along with an adjustable fork, this should make it more 'trail' orientated.

So - opinions, impression, ideas? All constructive feedback greatly appreciated


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## derby (Jan 12, 2004)

I like the idea of adjustable jackshaft. I think the future of internal frame mounted gearboxes will be this type design, whether monopivot or multi-link.

Maybe you were referring to greater than 100% anti-squat in the first 75mm of travel. Positive anti-squat occurs any time the chainline intersects the swing line forward of the front wheel and above the ground (or below the ground behind the rear wheel). 

Braking has no chain effect (except for motorcycle engine braking effects when there is no freewheeling hub, slipper clutch, or engine braking TC). Freewheeling rear braking has suspension compressing effects when the anti-dive percent is positive, any time the swing line intersects the ground line forward of the front wheel (or below ground behind the rear wheel). The compressing effects more noticeably reduces rear braking traction and modulation power before skidding when approaching or over 100% anti-dive rate. The tradeoff for higher traction low anti-dive rate is increased suspension extension adding to the fork's brake dive inducing increased forward weight shift effects. And lower anti-dive braking greater traction geometry correlates with lower anti-squat rates and less efficient pedaling .

The DW-Link and the now many close non-infringing similar designs have very digressive anti-squat/anti-dive rate during compression travel, and well blend the pedaling efficiency near sag, with deeper travel pedaling or braking bump traction compliance. But these DWL type designs, having a path that becomes forward in deeper travel would probably not facilitate a jackshaft drive without a chain tensioner.

The fully rearward path such as yours, is probably best for DH park coasting and higher gear pedaling moments. And the brake stiffening effects of your high anti-dive rate is OK for DH park tighter turns which is frequently done by skidding the rear wheel. For trail riding it is very rude to skid turn, damaging the trail making pot holes, only beginners do this. Advanced trail riders never skid except for recovering from a rare big mistake.

JMO's : )

Nice design. Can it be produced?


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## jeffw-13 (Apr 30, 2008)

Similar to the Canfield Bros Jedi

http://canfieldbrothers.com/frames/formula-1-jedi


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## bluechair84 (Sep 30, 2008)

derby said:


> Maybe you were referring to greater than 100% anti-squat in the first 75mm of travel. Advanced trail riders never skid except for recovering from a rare big mistake.
> Nice design. Can it be produced?


Yes, greater than 100% during the first 75mm of travel, which really is an abitrary number going on the assumption that impacts which take you beyond 75mm of travel probably aren't going to be pedalled through  Lowering the jackshaft effectively increases the amount of travel that experiences anti-squat making it more pedal efficient. But because of the shape of the anti-squat curve, setting it to say, 120mm, doesn't dramatically increase the amount of AS, only the duration it is present for.
And yes, I'm working hard to produce it. I'm constructing a technical drawing now to take to an old friend who should be able to CAD up the linkages. I also have a tenuous link to someone who works making carbon fibre handgliders, so I'm going to try and borrow their autoclave. I'm a teacher currently in Summer hols so I've loads of spare time right now... and I'm keen to try and get it done before September!
Dive and brake-jack isn't something I've learnt about yet so I haven't explored that within this design (what you wrote made more sense the second time I read it  ). I should look into it more in future development.


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## bluechair84 (Sep 30, 2008)

jeffw-13 said:


> Similar to the Canfield Bros Jedi
> 
> Formula 1 Jedi Mountain Bike by Canfield Brothers


Yeah, the wheel curve and the anti-squat characteristics are pretty similar (though I didn't look to this frame for inspiration - I hope I'm not treading on any patents here!!) This will be made to be much lighter than the Jedi, and for a lighter application too.


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## Drew Diller (Jan 4, 2010)

Ah, a man after my own heart.


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## Walt (Jan 23, 2004)

Unless you are planning to sell the bike commercially, you can infringe on all the patents you want. 

Excited to see the construction shots - carbon is neat!

-Walt


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## compositepro (Jun 21, 2007)

Walt said:


> Unless you are planning to sell the bike commercially, you can infringe on all the patents you want.
> 
> Excited to see the construction shots - carbon is neat!
> 
> -Walt


Or you manufacture special high tech $5k seatposts ,say 1.5" diameter that only fit your frame, because it only fits your frame then you would essentially have to supply the frame free of charge meaning commercially you hadn't actually made and commercial interest on the frame and maybe the company with the patent could only sue for their loss of $0

You would be the most awesome seatpost in the world


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## bluechair84 (Sep 30, 2008)

I had a naughty idea regarding this. My original designs used an Alinfe 11 gearbox in the frame. The only way I could make it work would be to copy what Zerode did, but I assume they have a patent on it. It crossed my mind that I could sell the frame, then provide the modified hub 'free'. But, I'm just not that guy  It's now sans gearbox which is a shame really. If this frame works, and people were interested in having versions made for them, I wonder if I could license the Zerode hub? This final design is really the next best thing to what I really wanted to make.


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## Walt (Jan 23, 2004)

Build it and ride it (preferably, build several and ride them so you know where/how the first one sucks/breaks/works badly) before you worry about selling anything...

In fact, my advice to you right now is to *stop* posting and go make something, even if it's just some throwaway test joints. I think in your case the design work is going to be the easy part - making an actual bike from the drawings will be the challenge.

-Walt


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## David C (May 25, 2011)

This is complete Chinese to me (top bad I can't read Chinese yet), but I'm impressed by how much work and maths goes into a suspension linkage design. If this kind of brainwork was in my range, I'd be stoked to work on these projects instead of just being the one wrenching them.

The only time I've seen a jackshaft design on the trail here is my friend's Balfa NouveauRiche DH rig, setup with a Marz' Monster T, custom valved rear air shock, 3-4" wide rims and pneumatic (compressed air) shifters and derailleurs. All matte black, its like the Batmobile of DH bikes 

So what makes the jackshaft design superior to more "simple" designs to justify the extra work and engineering required ? In English please ?


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## Drew Diller (Jan 4, 2010)

bluechair84 my idea with using an Alfine as a jackshaft/gearbox is to use a left-side output with a custom machined adapter that would run a chain off the CenterLock output.

Hub CenterLock -> Shimano CenterLock 6 bolt rotor adapter -> machined part with receiver to 6 bolt adapter, would have a bearing in it that actually _rests on the damn locknut_

If I have my math right it could be built to exactly match up with the disc rotor position on a 150mm rear hub. Connect the front Rube Goldberg stuff to a VeloSolo disc cog in back.

But, then you'd have the trouble of putting a rear brake on the normally drive side of a bike.

I've thought about this concept a TON and am still going to execute on it, but in the mean time I've been quietly doing as Walt suggested, making joints.

EDIT I've also been making carbon fiber parts, derrr hurr hurr.

EDIT TWO: Also, keep in mind that if you took my approach, you'd have a constantly running second chain, so your coasting efficiency would be ass. On top of the general efficiency being ass. [SUB]I am aiming at stuffing a 1x10 in a box instead but that's a whole other thing.[/SUB]


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## compositepro (Jun 21, 2007)

bluechair84 said:


> I had a naughty idea regarding this. My original designs used an Alinfe 11 gearbox in the frame. The only way I could make it work would be to copy what Zerode did, but I assume they have a patent on it. It crossed my mind that I could sell the frame, then provide the modified hub 'free'. But, I'm just not that guy  It's now sans gearbox which is a shame really. If this frame works, and people were interested in having versions made for them, I wonder if I could license the Zerode hub? This final design is really the next best thing to what I really wanted to make.


Theres plenty of folks stuck a hub in a frame and called it a gearbox a little california company i worked at did it 1995 in fact lahar in new zealand also did it ,nicolai did it BCD did it even pinion has prior art on it with hydraulic plates


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## dr.welby (Jan 6, 2004)

Do you really need the upper back pivot right by the tire? Seems to make it wide, and gives you a great way to apply mud to your pivot bearings.


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## bluechair84 (Sep 30, 2008)

Walt said:


> Build it and ride it (preferably, build several and ride them so you know where/how the first one sucks/breaks/works badly) before you worry about selling anything...


Aye Aye captain


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## bluechair84 (Sep 30, 2008)

dr.welby said:


> Do you really need the upper back pivot right by the tire? Seems to make it wide, and gives you a great way to apply mud to your pivot bearings.


Well, all designs have their pros and cons. The pivot locations give some desirable curves that might be difficult to achieve with moving the pivot locations. But, this is a proto, and that's a fair criticism - something I could look at in future iterations.


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## bluechair84 (Sep 30, 2008)

Drew Diller said:


> bluechair84 my idea with using an Alfine as a jackshaft/gearbox is to use a left-side output with a custom machined adapter that would run a chain off the CenterLock output.


Aye, I responded to your PM with that very idea. It's definately worth looking into, but there's issues with hub choice as, like you say, the disc then runs off the wrong side. Profile do an LSD conversion for their singlespeed which would mean you only need one custom ring on the gearhub, and a standard sprocket on the rear hub. Then you have the disc mounts too. FYI, I couldn't find a single fixie hub with disc tabs to avoid running two freehubs... so you might end up having too any custom or rare components to make such a design good for production. I still think the Zerode way is brilliant. 
Other things worth noting are that standard shimano cranks will barely clear the 135mm hub as the Q Factor is 150mm. The 83mm BB shell Saints and Zee aren't much wider at 153mm IIRC... I looked into fat bike cranksets to clear the hub, but you'd never get the chain line right without running a wide rear hub. Sram however, seem to do cranks with a 171mm Q factor... that's what Goldilocks would go for


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## bluechair84 (Sep 30, 2008)

David C said:


> So what makes the jackshaft design superior to more "simple" designs to justify the extra work and engineering required ? In English please ?


I'll write you a thingy up later, now - it's movie time...


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## bluechair84 (Sep 30, 2008)

David C said:


> So what makes the jackshaft design superior to more "simple" designs to justify the extra work and engineering required ? In English please ?


Ok, historically, bike designers didn't really look to the chain as a way of improving pedalling performance which led to the development of platform damping in shocks (I think Fifth Ellemnt introduced it into the MTB world). But more recently, designers have come to realise they can use the chain as a way of controlling the suspension. The two key terms are squat and anti-squat.
Imagine a typical single pivot frame with the pivot around the middle chainring:








The pivot is between the small and big ring. Have a think about how changing gear alters where the chain is in relation to the pivot point. Now, imagine the rear axle is naturally at around 9oclock position to the BB. With the bike in the big ring (pivot point just below), imagine pushing the wheel around to the 12oclock position. The top run of chain would become slack because the ring is closer to the axle than the pivot is. Imagine doing the same but in the little ring this time. At 12oclock, the top run of chain would be tight because the top of the granny ring is further away from the axle than the pivot point - in fact, if the chain was fixed to wheel and frame, you wouldn't be able to move the wheel up at all!
If when the back wheel lifts, the chain goes slack, this is called squat, because if you were pedalling hard, the chain would effectively pull the wheel up. 'Squat' describes what happens to the bike; pedal hard, rear suss compresses, bike squats. If when the back wheel lifts, the chain is tense and needs to find extra length from the bottom run, this is called anti-squat. When pedalling hard, the chain will tug the rear wheel back down to full extension. Think about the name again; anti-squat (or, 'stand up') describes what is happening to the suspension.
OK so far? Now squat and anti-squat are _both _desirable. Anti-squat (extension of the suspension) is great for pedalling hard, but bad for bumps because chain growth has to come from accelerating the rear wheel or spinning the cranks backwards, or the suss just won't move. Squat is terrible for pedalling because pressing hard on the cranks actually pulls the rear wheel into the suspension, but because there is no chain growth (actually, it's a negative value), the rear suspension isn't restricted in it's movement so can consume bumps freely.
OK, so in simplest terms, anti-squat is better for climbing, squat is better for descending, but that assumes when climbing you don't need to absorb bumps, and when descending you won't be pedalling. Any company which tells you their suspension is both pedal neutral and bump compliant (Ellsworth are especially neglectful here) are lying to you. Pedal efficiency and bump compliance are opposites of a polar scale - a design cannot be both (Ken Sasaki wrote extensively disproving companies claims).
So, Jackshafts then. As you possibly wondered now, the pivot point can't be very far from the chain because of the importance of the relationship between them. If they are too far apart, terribly high anti/squat can occur (it's a little more complicated as it's the chain'line' which is important). Because the pivot is relatively low on the frame, bound to be close to the chain (many designs have the pivot below the the BB), the wheel effectively is coming forwards as it goes through its travel. This is pretty terrible for bump compliance. High pivot points allow the rear wheel to move backwards as they come up, so they go around impacts, not trying to headbut their way through impacts. Just look to the current GT Fury (which has a high pivot) which is proving a huge success on the WC. But high pivot points (as we saw with the small ring on the Orange 5) will create lots of anti-squat. GT get around this with a BB which moves backwards to offset chain growth. The jackshaft allows you to run a high pivot point around a much higher chainline; so you can have a good axle path, _and _good squat characteristics normally associated with low pivot bikes.

Three things to note - unless the frame is a 'singlepivot' a the one pictured, frames have 'virtual pivot points', which means somewhere that is not mechanically fixed. Santa Cruz may call their signature system VPP, but all non single pivots are VPP. Theirs is just a brand name.
Secondly, this VPP nearly always moves around, so the pivot might be in one location early in the travel, but somewhere entirely different at the end of the travel. This can be very good because it allows you to vary where you want your squat and your antisquat in the travel.
Finally, the relationship is actually between the VPP and a line projected from the chain. Because this projected line moves as the suspension moves, you are balancing two moving points in design to counteract one-another, or work together to create your desired squat characteristics. My design took five different suspension 'philosophies', and a dozen iterations of each before I finally got what I wanted. How important is squat compared to platform damping? Well, Spesh have just announced a collaboration with Ohlins to have a shock with no platform damping at all, meaning the only thing controlling squat will be the chain...

And this is just squat, as mentioned earlier, braking can also effect suspension and traction. I've not spent any time evaluating that for this design. I'm just going to see how this performs first. There's also shock lineage, geometry and wear-tear factors at the bearings to try to resolve. There will always be a compromise - the important thing to learn is that no bike can be all things to all terrains, it is the job of marketing departments to convince you otherwise.

Anyone else - feel free to improve or amend the above, I'm no engineer, but I have tried to keep things simple.


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## David C (May 25, 2011)

Thanks for the write up, I get the idea now. So is the i-drive from GT one of the best pedaling platform out there too ?


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## dr.welby (Jan 6, 2004)

bluechair84 said:


> Ok, historically, bike designers didn't really look to the chain as a way of improving pedalling performance which led to the development of platform damping in shocks (I think Fifth Ellemnt introduced it into the MTB world). But more recently, designers have come to realise they can use the chain as a way of controlling the suspension. The two key terms are squat and anti-squat.


A good intro, but you're missing a few things.

Historically designers were aware of the chain's role in suspension performance long before platform shocks, though there didn't seem to be a full technical understanding. Many early designs had high pivots on the seat tube that were late abandoned. For example, GT moving from the RTS to the LTS (pretty successful). There was also Trek moving from the 9800 or whatever that thing was called to the URT Y-bikes, which were an attempt to eliminate the chain pull from the equation without understanding everything else that was going on (and therefore sucking, also to be dustbinned). You even had some early jackshaft attempts like Cannondale's crazy team DH bike (which also was one of the first short link VPP bikes).

Squat is the tendency for a vehicle to compress the rear suspension when accelerating, because the center of gravity is higher than where the force accelerating the vehicle is being applied. This causes the vehicle to loop out / wheelie which transfers weight to the rear wheel, compressing the suspension. Strategies to counteract this tendency are 'anti-squat', anything which adds to this would be 'pro-squat'.

High pivots do allow the rear wheel to move backwards which seems like a good thing, but if the wheel is moving backwards relative to the rider it's slowing down, and then you need to speed it back up. Some of that energy should come from the energy stored in the spring, but if you look at motocross bikes, where you have more leeway in positioning the engine output than you do in locating cranks, the pivots are still pretty low.

A high pivot does have some advantages in what's called 'thrust antisquat'. Let say you had a chainless bicycle that is driven by a Wile E. Coyote setup of small rockets mounted tangentially to the wheel (this lets us accelerate the bike without any interaction with anything else). Let's say the pivot point was really high. You could see how the rear wheel would want to tuck in under the rider and lift the bike, which is antisquat. That's way more than you want, but if you move the pivot down you'll eventually hit a point where the lift matches the squat exactly. What's great about this is that both forces are proportional to your acceleration, so they are always balanced. This is why the high pivot jackshafts are sort of the 'holy grail', at least on paper. On a regular geared bike, especially with a front derailleur, you chain moves around and any antisquat you get from chain tension is going to vary. On a jackshaft bike, you can get your antisquat purely from thrust antisquat, and then position your chain so it has no influence, taking it out of the equation. Though it's a decent argument that having your antisquat vary by gear is a good thing, especially on a cross country bike.


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## bluechair84 (Sep 30, 2008)

dr.welby said:


> A good intro, but you're missing a few things.


Thanks for adding to that  the historical stuff regarding the old LTSs are before my cycling time


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## bluechair84 (Sep 30, 2008)

David C said:


> Thanks for the write up, I get the idea now. So is the i-drive from GT one of the best pedaling platform out there too ?


Maybe... maybe not. The high pivot should give it considerable anti-squat, but their AOS (?) design which is the successor to the i-Drive allows the BB to move backwards, thus mitigating some of the chain growth associated with a high pivot. There are certainly bikes out there with, what I would regard as having too much anti-squat which would make them pedal (at least over smooth ground) really well. You could say of the Fury; _they've created an interesting approach to a compromise between anti and pro squat._ Which is what you want to be able to say of most bikes... It's what I've attempted with mine, an interesting compromise. A bike can never been excellent at the same point in it's suspension at both pedalling and bump-munching.
In my experience, the Freedrive used by Mongoose which is related to i-Drive was terrible because it was so good at pedalling. Point it downhill and it felt like I was sliding down on my ass! The current design doens't seem to be doing too badly for the Athertons though! I must have terrible taste in bikes...


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## bluechair84 (Sep 30, 2008)

dr.welby said:


> Squat is the tendency for a vehicle to compress the rear suspension when accelerating, because the center of gravity is higher than where the force accelerating the vehicle is being applied.


This would make more sense to me if the CoG was lower than the accelerating force


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## Drew Diller (Jan 4, 2010)

dr.welby said:


> A high pivot does have some advantages in what's called 'thrust antisquat'. Let say you had a chainless bicycle that is driven by a Wile E. Coyote setup of small rockets mounted tangentially to the wheel (this lets us accelerate the bike without any interaction with anything else).


Hah, that was a fun mental image. Good analogy.


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## compositepro (Jun 21, 2007)

The RTS LTS and Idrive were all designed by one guy 

When we made the original prototype of the GT IT1 the rear hub was a hope big un front hub run on the back the output drive from the front nexus hub ran on a splined 4 arm spider similar to centrelock, either way the rear hub was fixed and driven from the non drive side the disk was on the drive side


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## dr.welby (Jan 6, 2004)

bluechair84 said:


> This would make more sense to me if the CoG was lower than the accelerating force


I'm not following you, but here's two illustrations of what's going on, though these are braking, so everything is in the opposite direction.


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## dr.welby (Jan 6, 2004)

compositepro said:


> The RTS LTS and Idrive were all designed by one guy


Are you talking about Brian B. ?


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## compositepro (Jun 21, 2007)

dr.welby said:


> Are you talking about Brian B. ?


do you mean Jim B


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## dr.welby (Jan 6, 2004)

compositepro said:


> do you mean Jim B


Nope, must be a different guy, I knew a Brian who worked on the LTS.


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## compositepro (Jun 21, 2007)

dr.welby said:


> Nope, must be a different guy, I knew a Brian who worked on the LTS.


Jim Busby designed the lot from what I remember ,Maybe before my time as I was of the STS Thermoplastic and Lobo always wondered where these folks went


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## bluechair84 (Sep 30, 2008)

compositepro said:


> The RTS LTS and Idrive were all designed by one guy
> 
> When we made the original prototype of the GT IT1 the rear hub was a hope big un front hub run on the back the output drive from the front nexus hub ran on a splined 4 arm spider similar to centrelock, either way the rear hub was fixed and driven from the non drive side the disk was on the drive side


Any idea what the O.L.D. was? Must have been tough to resolve the chainline issue?


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## compositepro (Jun 21, 2007)

bluechair84 said:


> Any idea what the O.L.D. was? Must have been tough to resolve the chainline issue?


it was just a front hope hub run on the back

Patent US6079726 - Direct drive bicycle - Google Patents section shows is how it was done nexus hub had the spoke hole flanges machined off

Patent US6155585 - Direct drive bicycle - Google Patents

chainline iirc was just straight lined to the hub with a spacer to push the cog off the hub


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## bluechair84 (Sep 30, 2008)

dr.welby said:


> Squat is the tendency for a vehicle to compress the rear suspension when accelerating, because the center of gravity is higher than where the force accelerating the vehicle is being applied. This causes the vehicle to loop out / wheelie which transfers weight to the rear wheel, compressing the suspension. Strategies to counteract this tendency are 'anti-squat', anything which adds to this would be 'pro-squat'.


Hmm, I'm thinking of moments - an accelerating force will create a moment about the CoG. If the CoG is higher than the force, the force will try to come beneath, and extend suspension. But thinking about what you've said, when accelerating, the rear suss squats. I'm not got my physics brain on at the moment! But you are right, I'm not thinking about it in the right way...


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## bluechair84 (Sep 30, 2008)

compositepro said:


> it was just a front hope hub run on the back
> 
> Patent US6079726 - Direct drive bicycle - Google Patents section shows is how it was done nexus hub had the spoke hole flanges machined off
> 
> ...


I've had a scan through the patents, and it looks like they've patented the very concept of 'frame mounted gear box'... not just a design which uses a gear hub and drives the wheel from the disc tabs. Does this mean that every Zerode, Pinion, Lahar Nicolai and what not are paying royalities to GT? Thanks for the info by the way, very informative.


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## bluechair84 (Sep 30, 2008)

Got the links CADed up last night to be sent away for printing in nylon. And there will now unfortunately be a short break in the project as I move house this weekend, and I'm pretty sure my girl is going to have me painting and drilling holes and doing the garden and naffy crap like that  But, I will be modelling the frame to make the moulds for the CF in my spare time. Oh, and I have to build myself a workshop in the new garage before then too. Gonna be a busy few weeks!


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## dr.welby (Jan 6, 2004)

bluechair84 said:


> Hmm, I'm thinking of moments - an accelerating force will create a moment about the CoG. If the CoG is higher than the force, the force will try to come beneath, and extend suspension.


Yeah, that's basically it, but take the suspension out of your mental model first. The force at the ground makes a moment around the CG. So stop there and start over. Let's say you have some moment around the CG, how does that moment manifest at the wheels. At the rear wheel the moment is pushing down, which will load the rear wheel. Now that we've established that, add back in some suspension. Increasing the load on the suspension will make it squat. Now yes, that load may be counteracted by some amount of antisquat. But all vehicles that are accelerated (or braked) through the tires will have load transfer from one wheel to the other.

When you talk about the force coming beneath and extending the suspension, I think what you're seeing is the force on the ground creating a moment around the pivot point. That's the thrust antisquat I was talking about.


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## bluechair84 (Sep 30, 2008)

Got it. It makes no sense at all for the force to extend the suss!


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## xy9ine (Feb 2, 2005)

fyi, here's the rohlof out of my lahar - just a simple chainring carrier bolted to the spoke flange. simple & effective:









neat project you've got going; looking forward to watching the process.


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## bluechair84 (Sep 30, 2008)

Great share, thanks. I didn't know this was how Lahar did it - I thought Zerode had the idea and I didn't progress down the gearhub route as I thought there would be design infringement issues


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## cheesy (Apr 15, 2009)

Drew Diller said:


> bluechair84 my idea with using an Alfine as a jackshaft/gearbox is to use a left-side output with a custom machined adapter that would run a chain off the CenterLock output.
> 
> Hub CenterLock -> Shimano CenterLock 6 bolt rotor adapter -> machined part with receiver to 6 bolt adapter, would have a bearing in it that actually _rests on the damn locknut_
> 
> ...


That sounds a lot like this one

Carbon Fibre Mountain Bike « ASP Ltd


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## bluechair84 (Sep 30, 2008)

cheesy said:


> That sounds a lot like this one
> 
> Carbon Fibre Mountain Bike « ASP Ltd


Very interesting frame.

Links arrived yesterday:










Garage is huge!! Full of boxes at the moment. But, there's a bit of space for me to start working up some mandrels.


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## bluechair84 (Sep 30, 2008)

A simple jig, welding in steel first of all.


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## NWS (Jun 30, 2010)

jeffw-13 said:


> Similar to the Canfield Bros Jedi
> 
> Formula 1 Jedi Mountain Bike by Canfield Brothers


That's what I was thinking as well. I have a Jedi and I really like the way it rides, and I think the rearward travel is a big part of the reason. It climbs well enough that I've stopped riding my AM bike. It's a little heavy though, so I think this rearward-traveling 180mm AM idea has a _lot _of promise. 

The Jedi only uses the upper pulley for the top of the chain line though, which helps keep things simple. For the bottom of the chain, there's another pulley behind/below the crank, as part of the bash guard. Between the two of them, chain growth is very small (not quite zero, but small). That gives you the same advantages as the jackshaft, but only one chain, and no need to bind two sprockets together on the jackshaft. It's a simpler way to solve the same problem, and I really think you should look into it.









https://canfieldbrothers.com/wp-content/uploads/2013/02/CanfieldBrothersJediMRPG3Guide.jpg

This design appears to have about half the rearward travel of the Jedi, so you might be able to get away with just the lower pulley without running into trouble with chain growth. It would be interesting to ride it that way and with an upper pulley in 2-3 positions, to see how much different it makes to have the chain tension providing anti-squat. The Jedi's lower pulley / guard setup is adjustable via slotted holes in the bash guard - if you do the same thing with yours then you could switch positions on the upper pulley pretty easily. Whereas with a purely jackshaft-based approach you'd need different lengths of one or both chains to accommodate different shaft positions.

Canfield uses a tweaked version of MRP's chainguide but I think you could get away with the regular version if you just remove the 'input' part of the guide. It seems redundant with the upper pulley anyway.


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## bluechair84 (Sep 30, 2008)

NWS said:


> I think this rearward-traveling 180mm AM idea has a _lot _of promise.


Thanks, I'[m stoked to hear this 


NWS said:


> That gives you the same advantages as the jackshaft, but only one chain, and no need to bind two sprockets together on the jackshaft. It's a simpler way to solve the same problem, and I really think you should look into it.


I'll be able to test both ways once the first mule is built, but you're right; brazing two sprockets together will add a layer of complexity I'd rather avoid.



NWS said:


> The Jedi's lower pulley / guard setup is adjustable via slotted holes in the bash guard - if you do the same thing with yours then you could switch positions on the upper pulley pretty easily. Whereas with a purely jackshaft-based approach you'd need different lengths of one or both chains to accommodate different shaft positions.


I think a proper tensioner will be needed as you'd never get the perfect chain length to fit between the cranks and the pulley. This could have enough tollerance to account for different positions. Or you could have a few split links in your sack to adjust. But I was thinking about this last night and realised it doesn't need different positions on the frame... just different diameter sprockets. Another layer of complexity removed


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## NWS (Jun 30, 2010)

Different sprockets instead of different frame positions? I'm not sure how that would work... unless you meant, "doesn't need different chain lengths," because that sounds like a great solution.


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## bluechair84 (Sep 30, 2008)

NWS said:


> Different sprockets instead of different frame positions? I'm not sure how that would work... unless you meant, "doesn't need different chain lengths," because that sounds like a great solution.


Well, if i built a single point on the frame for the jackshaft, different sized sprockets would alter the chainline in exactly the same way i described earlier with the single pivot / triple chainset set up. It doesn't solve the chain length issue, but either way it will need a tensioner.


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## bluechair84 (Sep 30, 2008)

It's been a few years since I started this project! Since then I've changed jobs, moved house, gotten engaged... and this project has been a little on the back burner. It's given me a lot of time to refine the design and build up a proper 2D cad so I can manage the dimensions and numbers precisely though so I have been beavering away.
The design has changed considerably over the years and I think I've gone through at least half a dozen different suspension configurations and probably half a dozen iterations of each of those! But I'm happy with the suspension and squat curves now.
Recent developments: I've started the blank. It's a gorgeous day here in the UK for curing a polyurethane coat!































I've got some beautiful curves on the frame; the dorsal fin and headtube web. You make out the barebones of the jig that I'm using to dry the frame too.
The process from here: Get a glassy finish on the blank, mount with the hardware mandrels to the jig and cast a two part mould in fibreglass. 
Expect the next update in 2018


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## bluechair84 (Sep 30, 2008)

The rocker links cadded up. Prototype will just run 3D printed links.


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## Collins (Feb 23, 2013)

Congrats on living a good life -- and keep at the frame!


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## bluechair84 (Sep 30, 2008)

Cheers fella


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## bluechair84 (Sep 30, 2008)

Slowest project build on mtbr? 
The jig is mostly finished and just needs one more mandrel attached to it (the BB tube). The next big step is to properly align all the mandrels with one-another. To do this I'll use a laser level projecting against the garage door and then adjust the mandrels until the dots match the correct distances from one-another. I figure that at 10 feet from the projection, the alignment will be to a pretty high tolerance (certainly higher than the tolerance on my Socom which needs a real man handling to bolt the rear triangle into place...).
Then the big one - casting mould A of the clamshell! But before both of these I need to do a real big garage tidy. So many tools are knocking around right now that have been regularly in my hands in this process that I don't think anything is where it belongs!


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## Drew Diller (Jan 4, 2010)

bluechair84 said:


> Slowest project build on mtbr?


Feel zero shame for this.

Zero.


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## bluechair84 (Sep 30, 2008)

This is going to speed things up a bit! I've gone and picked myself up a small lathe as I'm fed up of trying to find people willing to do the many small jobs I need to progress. It's another thing to learn but, hey ho it's what I'm enjoying...
I'll be using her to lathe a 35mm diameter main pivot axle, a BB tube mandrel, some jig components and some bearing sleeves. But, she's a bit antique so I'll be spending some time making sure that she runs straight and true before I can put her to real use.


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## bluechair84 (Sep 30, 2008)

Slowly slowly catchy monkey. Bought a better lathe - a proper thread cutting lathe. Just working on an axle which will carry the sprockets that direct the high chain line back to the wheel. This axle will also act as the main pivot so will carry four sets of 47mm bearings  Beast.









In the time it's taken me to get from that last post to the current post, I've designed up a 'mkII' which in reality is many many dozens of designs littering my hard drive. Given that progress in improving the first 'settled upon' design was made faster than actually building, I've gone ahead and begun the most recent design, abandoning the last. Every iteration of design feels like it's a significant improvement over the last as I'm getting better at balancing the suspension forces (in theory at least).


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## bluechair84 (Sep 30, 2008)

A wee update on progress;
I've been spending some time developing 3D models of the frame whilst waiting for some parts for the lathe which are a week overdue. The chainstays need a little more design work but essentially, I'm quite pleased with the progress made on the CAD side of this project.









I'm also going to try something a little different in constructing a mould for the main frame. I've built up a 3D sketch from 2D layers and will use a laser cutter to produce around 27 slices of 3.6mm ply which will be glued together. This will give me perfect symmetry which I was struggling with using the blue crafting foam, and also some accurate mounting locations for the mandrels which will mean I no longer need a jig. I can get the slices cut for less than £200 which is significantly cheaper than getting a 3D print of the same proportions, but will just need a little finishing at the curves because of the 'low resolution' of each slice.









Timescale; well, I'm signed off sick after a pretty horrendous crash a few weeks back. But I hope to have the final mould for the frame in the next month. If everything goes to plan, I want to have the monocoque moulds made for the mainframe before Christmas. If things progress quicker than planned, I could also have the chain stays and seat stays as well.


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## bluechair84 (Sep 30, 2008)

I've had a lot of 3D success this week and have fully modelled the rear end. The front end is much harder to model because of the altering profile of the tubes, and it isn't needed for the project to progress as between the 2D frame slices and 3D stays I am able to produce a mould. By December, I hope to have the blanc and over Christmas take a mould from this.


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## MannaDesigns (Mar 5, 2013)

Cool progress, excited to see where it goes! 

Can i ask what kind of sizing has gone into the lug geometry for your stays? Looking at the 3rd picture down (intermediate link?) The gut check looks a bit like some pretty thin areas. Also curious if plan to radius out the details for your layup? The sharp corners may prove to be tricky....


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## bluechair84 (Sep 30, 2008)

Keen eyes on both fronts - the connections points on the seatstays are quite thin and I might have to change them to clevis style joints. I'll be keeping an eye on that design front. And yes, I haven't chamfered the edges but it's the narrow bits that have stopped me from doing so thus far. The chamfers eat into too much of the thinner areas so I've left them out until I've settled on any final implementations.


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## bluechair84 (Sep 30, 2008)

I've mostly finished the CADing of the full frame now. The assembly allows me to operate the suspension though it was originally designed in Linkage. I've got some hardware to design and a bit of alignment to check but essentially, I'm about ready to start with 3D printing and 2D laser cutting to build my physical models.

















Now it's CADed up... I'm thinking the back end looks seriously oversized!


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## bluechair84 (Sep 30, 2008)

A few more months of work have gone by and my CAD design has progressed to this state:









With a little more fiddling of the faces I can perform FEA analysis on the whole bike frame. Also, now that the frame is essentially hollow, I can begin to run jigsaw parts of the frame out of the 3D printer and assembly a plastic 1:1 model. From this, the model will be moulded into a two piece 'clamshell' mould. The mould will ten form the basis of fabricating the real deal.


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## eddygara (Feb 14, 2017)

bluechair84 said:


> A few more months of work have gone by and my CAD design has progressed to this state:
> 
> View attachment 1113656
> 
> ...


How do you plan too deal with the issue of alignment of the pieces for the mold? I am actually doing the exact same process as you, (been at it for a year now). The one problem i found by 3d printing a positive model was that i would never be able to have everything line up accurately. when making a negative out the positive mold, ( i haven't really tried this, its just a theory).

Theoretically without a jig in place of the positive mold that was 3d printed piece by piece, when creating a mold out of those pieces you can get movement as well as twist in the parts, while they are being casted. Resulting in a miss aligned frame. Unless you have a 3d printer big enough to print the frame in one whole piece.

I tried to fix this by making a 6ft tall 3d printer to print the bike is fewer pieces. but im still worried about the parts shifting when creating the finale negative mold.

This is the design 








This is the printed model








this is how big each section is on its self.
















This is one of the 2 6ft tall printers i built. 








sorry too hijack i just really wanted to share and get you incite on this since we are kind doing the same thing.


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## bluechair84 (Sep 30, 2008)

Ace, that printer is exactly the kind of thing I need. I’ve heard of people building their own, but I don’t know anything about that. How did you go about designing and building that?
As for combining sections of your frame, think along the lines of a jigsaw puzzle. The half-section view I posted is not my printing file but an FEA file. It’s cut down into many more pieces than that. There are three ways that I can think of to do it. Firstly, Autodesk Inventor allows you to slice up a model and it automates ‘pins and sockets’ on the adjoining faces. Secondly, you can design in a female socket on both faces and print a square dowel to locate them together. Finally, you can reduce the diameter of one tube to make a sleeve which protrudes inside the second part. I’m using something similar to the latter technique. Obviously, if your printed tubes are hollow and not mesh filled / solid, you’ll run into issues with the ‘adjoining’ surfaces falling down into the tube so design them carefully. 
Another thing to think about is the line thickness. If the extruder is following a line that defines the perimeter of the body, and it’s laying down a .2mm thick print, you’ll have .1mm either side of the line. So, 0.1mm of interference between the two surfaces and 0.05mm to shave off for a proper fit. If you make pins and sockets, this will be very difficult to make fit. And this problem rears its head at press fit surfaces too where you’ll need a reamer to get your surfaces accurate… but then you’re aerosolising carbon dust so you’ll need extractors or a damping fluid to cut down (dangerous) dust particles… or you could just not use the printer to define your press fit surfaces


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## eddygara (Feb 14, 2017)

thanks for the input. I have the part down for joining the sections together. If you look at the pictures of the frame you can faintly see plugs that act as junction points too other 3d printed sections. 

The issue im running into is getting those sections too line up perfectly. And then staying in place when casting them in resin. Under all the pressure from the resin, i would assume there could be some sort of deformation in the 3d printed model no? I think i could cast the front in better then i could the rear end for sure, and thats where im stuck. what out making some sort of internal ridged jig too hold the 3d printed model in place i dont see how i can do about doing this.

All of my press fit surfaces will be formed from machined plugs i made on my lathe. Everything is machined and polished too insure the best tolerances in press fitting i can achieve on my own. I went with pulgs too insure i had a way too mold that feature into the negative mold of the frames. 

As for the 3d printer, i bought my 1st kit about a year ago, i learned the mechanical, and electronics of that product for a whole year. Many hours and long nights and tinkering i was able to come up with a reliable and working printer that is pretty much hands free now. I can go hours on hours about 3d printers and how they work, (i invested a lot of time and money into that project, if you can tell ).


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## bluechair84 (Sep 30, 2008)

Oh, I think I see... Let me go this straight; are you printing your mould as an 'interior' mould and wrapping it in resin and fibre? So entombing the mould forever inside the frame? Or are you casting from the printed mould to make to make a new 'exterior' mould (a clamshell for instance of the print), and the fibres laid up inside of this?


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## eddygara (Feb 14, 2017)

The 2nd one i believe. 

I am printing a positive models of the frame design. After which i sand and finish the surface of the printed model. this is the 1st step. 

Once it is prepped and smooth, then i would cast that 3d printed frame model and make a split negative mold (like a clam shell) 

This negative mold would then be used to lay up the carbon. Bladders will feed into the frame too help insure consistent molding and even pressure though out the frame.

In not way will there be a 3d printed core. The 3d printed model is only used to make the negative mold, and thats it.


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## bluechair84 (Sep 30, 2008)

I see; you and I are following the same approach. The 3D model is essentially disposable after the external mould is made. I haven't made my two piece negative mould yet but have a partner whose living is made in this very process. Neither of us are expecting 'pressure from the resin' to warp the moulding process. One half will be laid up and allowed to cure, then the other half laid up against the first with a release agent between them. Once both sides are cured, the two halves separated and the printed model popped out. Are you vac-bagging your two halves against the printed model?


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## bluechair84 (Sep 30, 2008)

Have you seen the article where Scott reveal how they produce their carbon frames using a foam core?


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## PeopleForScience (May 15, 2012)

eddygara said:


> How do you plan too deal with the issue of alignment of the pieces for the mold? I am actually doing the exact same process as you, (been at it for a year now). The one problem i found by 3d printing a positive model was that i would never be able to have everything line up accurately. when making a negative out the positive mold, ( i haven't really tried this, its just a theory).
> 
> Theoretically without a jig in place of the positive mold that was 3d printed piece by piece, when creating a mold out of those pieces you can get movement as well as twist in the parts, while they are being casted. Resulting in a miss aligned frame. Unless you have a 3d printer big enough to print the frame in one whole piece.
> 
> ...


Is that second carriage holding your extruder? I really like that setup, I have problems with my DIY delta in the bowden tube friction. Is it suspended rigidly or is it just floating around up there?


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## eddygara (Feb 14, 2017)

PeopleForScience said:


> Is that second carriage holding your extruder? I really like that setup, I have problems with my DIY delta in the bowden tube friction. Is it suspended rigidly or is it just floating around up there?


Sorry for the long wait in reply, but yes it is a second carriage suspended holding the exstruder. Its called a flying extruder, this one is my design, but its pretty generic.

I was having the same issue with friction from the a long bowden tube. This eliminates the issue by making a tube only a couple inches long so a drastic decrease in friction. I can send you the files if you want to use them. As you can tell having a 4ft bowden tube didn't make printing easier at all.


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## eddygara (Feb 14, 2017)

bluechair84 said:


> I see; you and I are following the same approach. The 3D model is essentially disposable after the external mould is made. I haven't made my two piece negative mould yet but have a partner whose living is made in this very process. Neither of us are expecting 'pressure from the resin' to warp the moulding process. One half will be laid up and allowed to cure, then the other half laid up against the first with a release agent between them. Once both sides are cured, the two halves separated and the printed model popped out. Are you vac-bagging your two halves against the printed model?


I'm hoping too actually have a full resin casted mold of the entire front triangle. In a 2 piece mold. The plan is then too reinforce the outside of it, that I can help clamp down the mold even more, and apply more pressure too the mold. It would be molded using silicon bladders, and then a pump would inflate the inner bladder. Hopefully the added outer reinformant will hold. And ill have my finished piece.

This is all a threory though and hasn't been tested yet. Fingers crossed.

Do you mind sending me the vid of Scots foam core method? This was another route I was looking into. Cnc routers are easy for me too source so making a form co are would be a piece of cake.


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## PeopleForScience (May 15, 2012)

eddygara said:


> Sorry for the long wait in reply, but yes it is a second carriage suspended holding the exstruder. Its called a flying extruder, this one is my design, but its pretty generic.
> 
> I was having the same issue with friction from the a long bowden tube. This eliminates the issue by making a tube only a couple inches long so a drastic decrease in friction. I can send you the files if you want to use them. As you can tell having a 4ft bowden tube didn't make printing easier at all.


I'm all good on the models, I just modified my design to have an anchor point for the second carriage. I havent gotten it all printed just yet but I should be finished soon!


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## bluechair84 (Sep 30, 2008)

A little update:








I've had this made for a little while now. The picture shows it at an earlier stage where I'd just gaffa tapped the parts together to check alignment (roughly). The parts were glued together and it all looks pretty good. However I've gone back to the CAD and I'm printing the whole frame again for a number of reasons;
Having the model in hand I can see that there are too many sharp corners where getting the carbon to fit properly inside the mould will be awkward. I've removed these from version 1.2.03.
I was playing around with the idea of putting the bearings into collets that I would spin off of the lathe but, it's more work and hardware. What I will have to do is spend more time on the carbon frame reaming the bearing locations instead.
The model has been printed off in PLA and, as I've printed in a 'normal' resolution (instead of 'fine'), has left over a grain that I was going to sand out. However the stuff is like flippin' concrete and I'm giving myself tennis elbow trying to get the glassy finish I'd like before casting. So I'm printing the next model in ABS which dissolves in acetone, the idea being that I'll be able to 'wipe' the model smooth with dipped cotton pads.
Finally, I'd taken a short cut and not designed in any 'jigsaw' connections between each printed part of the frame and used the outer wall to feel the alignment as they were glued together. I'm going to add in dowels to the connecting faces of each printed part to align them properly.

I've also changed my short term plan, which was originally to print a model with no open shells, ie the BB or headtube. This makes it easier to cast as there are no open areas to fill in. I'm going to print a like-for-like model now to which I could attach all of the components. Importantly, I'll add all the suspension bearings, axles and shock to check the system moves smoothly without binding the shock bushes.

Since my last update, I've taken delivery of a little girl - updates will continue in their usual sporadic and haphazard fashion


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## eddygara (Feb 14, 2017)

Did you end up building a big printer? If not which model did you end up going with?


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## incubus (Jan 20, 2004)

Nice work. 
But more importantly, congrats on the new baby girl! I have two of my own (and a boy), and they're awesome. 


Sent from my iPhone using Tapatalk


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## bluechair84 (Sep 30, 2008)

This is a better picture. The parts did split around the downtube/headtube junction which you can probably make out but it's just a case of needing more glue. Another bonus to moving the print to ABS from PLA - I can use acetone to permanently melt the parts together.

Eddygara - I didn't build a printer. That's just one too many projects at the moment! I'm also writing an educational app (not my specialist area), building a sub floor in the loft and moving the access hatch (not my specialist area) and trying to raise a 4 month old (definitely not my specialist area!!). I'd have loved to give it a try but it would only push back the project build date... it's a 'throw money at it' kinda solution.
I ended up with a Prusa copy called an Omega i3 which has around a 200mm/\3 print area. Not a lot considering the thing I'm building! I'm pretty happy with it overall. Cost around £400 including upgrades to glass bed.
Incubus - cheers  They're pretty cool things to have around. Can't wait to be able to take her out on her first bike rides. I'm thinking, when she can hold her head up (not long now, she's virtually there), sling her in a backpack and take her out riding! Any advice from when you took yours out first time?


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## incubus (Jan 20, 2004)

bluechair84 said:


> Incubus - cheers  They're pretty cool things to have around. Can't wait to be able to take her out on her first bike rides. I'm thinking, when she can hold her head up (not long now, she's virtually there), sling her in a backpack and take her out riding! Any advice from when you took yours out first time?


I didn't take ours out until 12-15months old. But I wouldn't use my experience as a barometer. I had an overprotective wife to appease. 
I do recall seeing an article about biking with toddlers. Needless to say, the comments were full of advise and criticisms. But so long as you're careful, I don't see any harm in doing as you're planning.

Sent from my iPhone using Tapatalk


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## thefuzzbl (Jul 5, 2006)

Instead of dowels just print steps into one side and a pocket into the other side. That way you can just slide the tubes together. I work for a company that prints quite a few frames for bike companies and that is how we have always done it. The joint usually ends up being stronger than the tube.


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## bluechair84 (Sep 30, 2008)

I'd planned on dowels and holes because I can print the dowel 'star shaped' so that it deforms equally in the circular hole, compensating for the line thickness of the print. Ie, I might design a stepped shell that wouldn't interface because the print puts down plastic outside of the print path. I've not yet had experience of designing to compensate for line thickness. Thinking about it, the filament will lay half its thickness beyond the print boundary, so I'd need to leave room for interference that is the same thickness as the printed line (half a thickness for both the male and female part interference). It would be good experience for me to do some tests and experiment with design compensation...


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## thefuzzbl (Jul 5, 2006)

Slicing software compensates for filament thickness and doesn't "draw outside the lines". If you are getting prints that are not dimentially accurate then you should check your calibration.


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## bluechair84 (Sep 30, 2008)

This is why I love forums. You sir deserve a beer for that


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## bluechair84 (Sep 30, 2008)

I little update,
I'm printing a new version of the main triangle in ABS recently. It's been more difficult to get these parts right over the previous material, PLA, because of the higher temperature it needs. The first layer has been peeling off of the glass bed, layers have been splitting part way through the build... I've been gradually increasing the temperatures of both bed and hot end and finally was able to get out a full triangle. I've not started smoothing out the printed texture using acetone yet, but that's a job coming up. 
Unfortunately, part of the electronics of the printer burnt out so that's taken me a little while to repair as well (it seems the bed was drawing enough current to burn out the connecting socket - which has now been exchange for a better junction to connect the bed with the machine).


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## Drew Diller (Jan 4, 2010)

It's been a while since I last used a 3D printer, but at the time I did print with ABS, and I found that having a slightly warm enclosure helped out with the sudden shrink / potato chip / peeling effects.

Sorry about the electronics failure, that's not fun.


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## bluechair84 (Sep 30, 2008)

Drew Diller said:


> It's been a while since I last used a 3D printer, but at the time I did print with ABS, and I found that having a slightly warm enclosure helped out with the sudden shrink / potato chip / peeling effects.
> 
> Sorry about the electronics failure, that's not fun.


I've been thinking that same thing after I read that increasing the bed temp helps resolve separation as the heat rises through the part. What has stopped me from doing this is a clogged extruder which occurred because the fan that cools the upper body of the extruder (to stop the filament melting too early) became disconnected. It took a single print for the blockage to occur. I'm thinking that if I don't keep a cool air flow to the print head, if it's drawing in ever-warming air from a closed case, the extruder will block. So I'm torn at the moment; I've a number of prints with layer separation, including one that peeled from the bed at the corners - but being ABS I can get a real smooth finish. PLA has been a much more reliable printing medium, which is seemingly indestructible and gave me vibration white-finger trying to sand down the surface.
I'm going to run a test print at some lower print speed, the thinking being that the extruder will convect some heat into the upper-most layer as it passes over slower; the two layers then able to adhere better. There's always a but though... and this time it's cost. Some of the larger chunks can take anything upto 16hrs to print. Reducing the print speed to 50% is going to mean I've got a hot end at 240deg, and a bed at 80deg for 30+ hours... x 12 chunks... for just the main triangle... I'll need a second job! The 10-12hr prints can be done overnight at the cheaper electric rate. 
If I'm going to make this work I've got a lot of hurdles to figure out. The good news is I'm getting much quicker on the CAD files with associativity. I'm moving toward parametric modelling for the next version of the CAD file.


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## bluechair84 (Sep 30, 2008)

So, a summary of what I've been up to. I've built three printed prototypes, redesigned in Linkage and Inventor from scratch with a much more satisfactory frame, and been beaten to the idea by Commencal whose new Supreme DH is pretty identical to my own. Multiple pivot locations and a rocker driven shock were always going to make my own garage build quite difficult, so I've used the opportunity to make a much more humble project - a single pivot swingarm (no rocker) built around an open mould design, not a closed mould. The 3D print will be a consumed part in the final product and any reiterations can be layed-up right off of the print without constructing moulds. Here's the CAD work for the current stage:
















I've had support from Cane Creek in the past (who are brilliant), but they mount their trunion on the shaft end of their shocks meaning you have two wide mounting points (the eye is at the end of the air can so, the widest part of the shock). RS put their trunion on the air can, leaving you the narrower shaft and eyelet to squeeze into narrower frame compartments. I'm hoping to get some support from RS to work out how best to orientate the shock and build the frame around it. That, and working out the DRD detail is the final thing and then I'm getting back into printing!


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## dr.welby (Jan 6, 2004)

Are you planning a gearbox or idler in there? That pivot location is really high.


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## bluechair84 (Sep 30, 2008)

dr.welby said:


> Are you planning a gearbox or idler in there? That pivot location is really high.


Covered at length in the thread.


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## dr.welby (Jan 6, 2004)

bluechair84 said:


> Covered at length in the thread.


OK, I wasn't sure when you said "a much more humble project" that you were throwing all that out. I didn't see anything else in the model (yet).


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## bluechair84 (Sep 30, 2008)

Ah I see, I've dropped the multi linkage aspect but am retaining the high pivot point. It turns out that I can get a virtually identical axle path and perfectly suitable leverage ratios with the linkages. It might not be as stiff, but I'm hoping to build in a 35mm axle and 47mm bearings for the main pivot. The brace is in front of the seatmast but is quite broad. I'm much happier with a single pivot design now.


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## bluechair84 (Sep 30, 2008)

So I'm still playing with the design stage of this. I didn't really like the high single pivot. It really looked like the swingarm would suffer greatly from flex so I wanted to keep some form of triangulation back there. 
I've developed this design which has some really nice squat and leverage ratio values. The problem with this design is that it requires a pull shock (the shaft under tension not compression).
























I've got some work to do on the hardware side of this frame. You might notice that the BB and head tube look thin, but there is essentially no thickness to the tube walling.
As far as the back end is concerned, I'm looking to use as off-the-shelf parts, so I'm thinking of pinching all the ABP hardware


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## bluechair84 (Sep 30, 2008)

I've got the mould nearly designed up, though it will need some more alignment tabs. It will be printed fairly 'light weight' and beefed up with epoxy and fibreglass to resist being pressurised. There is also a little access door to help build carbon around the tighter corners and through a tunnel.

Another pic of the design with some additional work done on the hardwear:









Next jobs are to get back onto the printer and experiment with a few orientation prints - ie, will the mould print best vertically, layering up the tube surfaces, or horizontally, printing along the tubes.


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