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  1. #1
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    180mm VPP carbon design

    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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    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?

  3. #3
    The White Jeff W
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    Re: 180mm VPP carbon design

    Similar to the Canfield Bros Jedi

    http://canfieldbrothers.com/frames/formula-1-jedi
    No moss...

  4. #4
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    Quote Originally Posted by derby View Post
    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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    Quote Originally Posted by jeffw-13 View Post
    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.

  6. #6
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    Ah, a man after my own heart.
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    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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    Quote Originally Posted by Walt View Post
    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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    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.

  10. #10
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    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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  11. #11
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    180mm VPP carbon design

    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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    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. I am aiming at stuffing a 1x10 in a box instead but that's a whole other thing.
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    Quote Originally Posted by bluechair84 View Post
    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

  14. #14
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    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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    Quote Originally Posted by Walt View Post
    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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    Quote Originally Posted by dr.welby View Post
    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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    Quote Originally Posted by Drew Diller View Post
    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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    Quote Originally Posted by David C View Post
    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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    Quote Originally Posted by David C View Post
    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.

  20. #20
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    180mm VPP carbon design

    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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    Quote Originally Posted by bluechair84 View Post
    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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    Quote Originally Posted by dr.welby View Post
    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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    Quote Originally Posted by David C View Post
    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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    Quote Originally Posted by dr.welby View Post
    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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    Quote Originally Posted by dr.welby View Post
    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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    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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    Quote Originally Posted by bluechair84 View Post
    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.

    <img src="http://members.rennlist.com/tweedt/puhndiad.jpg" />
    <img src="http://www.procompusa.com/images/landing/tech//tec_underdynamics_03.gif" />

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    Quote Originally Posted by compositepro View Post
    The RTS LTS and Idrive were all designed by one guy
    Are you talking about Brian B. ?

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    Quote Originally Posted by dr.welby View Post
    Are you talking about Brian B. ?
    do you mean Jim B

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    Quote Originally Posted by compositepro View Post
    do you mean Jim B
    Nope, must be a different guy, I knew a Brian who worked on the LTS.

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    Quote Originally Posted by dr.welby View Post
    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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    Quote Originally Posted by compositepro View Post
    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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    Quote Originally Posted by bluechair84 View Post
    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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    Quote Originally Posted by dr.welby View Post
    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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    Quote Originally Posted by compositepro View Post
    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
    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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    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!
    Last edited by bluechair84; 07-31-2013 at 07:11 AM. Reason: Update to rocker

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    Quote Originally Posted by bluechair84 View Post
    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 <em>pivot point</em>. That's the thrust antisquat I was talking about.

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

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

    180mm VPP carbon design-l5.jpg

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

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    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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    Quote Originally Posted by Drew Diller View Post
    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. I am aiming at stuffing a 1x10 in a box instead but that's a whole other thing.
    That sounds a lot like this one

    Carbon Fibre Mountain Bike « ASP Ltd

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    Quote Originally Posted by cheesy View Post
    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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    A simple jig, welding in steel first of all.

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    Quote Originally Posted by jeffw-13 View Post
    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.

    180mm VPP carbon design-canfieldbrothersjedimrpg3guide.jpg

    http://canfieldbrothers.com/wp-conte...MRPG3Guide.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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    Quote Originally Posted by NWS View Post
    I think this rearward-traveling 180mm AM idea has a lot of promise.
    Thanks, I'[m stoked to hear this
    Quote Originally Posted by NWS View Post
    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.

    Quote Originally Posted by NWS View Post
    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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    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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    Quote Originally Posted by NWS View Post
    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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    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!
    180mm VPP carbon design-_sam6015.jpg180mm VPP carbon design-_sam6016.jpg180mm VPP carbon design-_sam6017.jpg180mm VPP carbon design-_sam6018.jpg180mm VPP carbon design-_sam6019.jpg
    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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    The rocker links cadded up. Prototype will just run 3D printed links.
    180mm VPP carbon design-rocker-links.jpg

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

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