Derailleurs...what do you look for in yours?
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the 24/7 messiah has a totaly bb concentric pivot, it pivots aorund the bb shell, that wouls work perfectly for belt.
http://www.bikeradar.com/gear/category/ ... siah-28932I like bikes and stuff0 -
It also pedals really bad, Josh.0
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oh yeah, but it shows that it is possible to have a zero chain growth full sus, some clever lincages could helpyeehaamcgee wrote:It also pedals really bad, Josh.I like bikes and stuff0 -
But a zero chain growth full suss WILL have bad pedalling characteristics, whether it's achieved by linkages, or pivoting round the BB shell.
In order for it to have zero chain growth/shrinkage, the EFFECTIVE pivot has to be at the BB shell, see. Keeping the rear wheel at the same distance from the BB shell requires it to orbit it.
Unless of course it's an URT design, which is a whole different kettle of crazy.0 -
hmmmm, well, i supose you are right. however, i feel that by linking in a "dog bone" that prevents movement of the swingarm when toque is applied to the chain, you could improve the pedalling caractaristics.yeehaamcgee wrote:But a zero chain growth full suss WILL have bad pedalling characteristics, whether it's achieved by linkages, or pivoting round the BB shell.
In order for it to have zero chain growth/shrinkage, the EFFECTIVE pivot has to be at the BB shell, see. Keeping the rear wheel at the same distance from the BB shell requires it to orbit it.
Unless of course it's an URT design, which is a whole different kettle of crazy.I like bikes and stuff0 -
a dog bone won't do anything. If the wheel stays a constant distance from the BB shell, then it will stay a constant distance from the BB shell. Nothing, no matter how complex is going to change that.
Whether it's a real or virtual pivot, the effect of having the swingarm axis inline with your BB is that every crank revolution tries to pull the wheel over the top of the pivot (since the chain/belt's line of tension is above the axis of roation).
It's not so much of a problem with motorcycles, because the high RPM of the engine and drive sprocket means the power is developed much more smoothly, and constantly.
It doesn;t matter how well you pedal, on flats, or SPDs, you will always have a low frequency ONE, TWO, action to your pedalling, which causes the bob issue.
Lifting the swingarm pivot above the chainline, and having a rearwards axle path counteracts the bobbing by making your pedal stroke pull the wheel down, towards the ground, and lifting the rear of the bike up. If done well, this will perfectly match the weight transfer onto the pedals, so the two movements (your weight bearing down on the bike & the rear wheel pushing against the ground, trying to lift the bike) will cancel out.0 -
I was thinking about this in similiar terms to the Idrive, just drop the I
Dependant Drive 
Float the BB on its own seperate linkage, with a long dogbone to the rear stay to drive it. Complicated obviously and could do interesting things to pedalling action... Let's see, mount the BB shell vertically to diminish the effect of pedalling (you'd have the BB move fore and aft to keep the "chain" equally distant, which would give a vertical component in its arc but not as drastic as the alternatives) it might ride like it was drunk, however Big landings would suddenly pull the BB backwards.
Ah, but you could make it even MORE complicated- forget about independantly mounting the BB, instead, have a secondary drive, with 2 belts, and have the interface of the belts on your Dependant Drive linkage. It'd be equidistent to both the BB and the rear axle at all times but frees you up to pivot the swingarm elsewhere. God knows what'd happen when you pedal Probably nothing, since the frame's going to weigh about 10 pounds. But hey, the belt will be light.
Or of course we could fit a belt roller or two... But i don't like that. Too easy
Uncompromising extremist0 -
your secondary drive thing would cause the exact same issue as pivoting around the BB shell. Wherever the pivot/drive belt is located, effectively becomes the new BB shell, and you're back at stage one.
Also, if the drive pulley moves relative to the BB shell, then you STILL have the belt-growth problem
See, complicated pointlessness!
However, if it was "made in britain" you'd probably get a load of trendwhore suckers buying it anyway, and proclaiming it to be the best thing since sliced bread. 0 -
Pedal kickback (chain growth) and anti squat are traded off in most sus designs. The less of one, the more of the other, and vice versa.0
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OK, hers the plan, have 2! yes 2! main pivots, one bb centric, one above the top ring. have a roller on the chain, so that when the chain is under torque it effectively locks out the main bb pivot, and due to the lack of chain growth on the belt, this would mean that only the top pivot was wroking, and, seen as it is restricted by the belt it doesnt move either, however is providesa rearwar axel path for the wheel when you take a big hit.
its hugely complecated, and im sure yee-whatsitsname will now pull it apart, but, hey.... I like bikes and stuff0 -
well, basically, it wouldn't work. It would just wobble about feebly, and drop the belt.
Come on, ideas that work are great, but now you're clutching at straws.0 -
yeehaamcgee wrote:your secondary drive thing would cause the exact same issue as pivoting around the BB shell. Wherever the pivot/drive belt is located, effectively becomes the new BB shell, and you're back at stage one.
Also, if the drive pulley moves relative to the BB shell, then you STILL have the belt-l:
I'm not sure that'd be the case, since the big problem with pivoting around the BB shell is that you can't do anything clever with the pivot position... Whereas with the Dependant Drive (TM) that's not an issue.
You don't have a belt growth issue becuse the 2 belts are effectievely "hinged" at the DD axle, so you can have the 2 belts at an unchanging length but the total distance covered by the 2 belts can vary, by varying the angle of intersection. I've seen some sort of mad DH bike with a vaguely similiar sort of secondary drive design in Dirt, though the execution and engineering was totally different of course.
Actually, I'm renaming it, it's the Trigonomatic Drive now No, wait, Trigonomical X Drive. X. Uncompromising extremist0 -
keep dreaming. Try planning it out in CAD (or meccano ) and you'll find it won't work.
Well, it's not so much that it won't work, it's that you're mis-interpreting the problem of BB-centred swingarm axis.0 -
Northwind
Do mean like this?
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I was looking for the one Cannondale made using a similar concept, and likewise, didn't actually do what it was supposed to.0
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It does look like you'd get some of the benefits of high single pivot with no pedal kickback though.0
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still get terrible squatting under power though.0
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Or get a hardtail...
My rear X-9 and front X-7 have now done 5500 miles and are still working as well as if they were new 0 -
The derailleur is an engineering masterpiece - it doesn't need replacing. Except by marketing muppets.0
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It's all about being different. Shimano invented the freewheel because fixies are an abomination, yet the hyper beardies (they are worse than the normal beardies that just ride singlepseed) still use them. In fact the next time I see a rider on a fixie cyclocross bike I will gun them down.0
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yeehaamcgee wrote:keep dreaming. Try planning it out in CAD (or meccano ) and you'll find it won't work
Course it will. Maybe I didn't explain it well. Easiest way to visualise it would be to picture a single pivot bike with a high swingarm, Orange 5 say. It wouldn't have to be a high arm/single pivor but it's easier to visualise and package since there's less going on in the suspension.
Throw a conrod out from the BB shell, which leads to the secondary drive Then, do the same from the rear axle, and have that meet at the secondary drive pivot. So, you have 3 sides of a triangle, 2 of which are fixed but the third can grow or shrink, as all 3 angles in the triangle can change.
(In theory you could put a freewheel on the secondary drive- moves the weight of the freewheel in towards the hub so would reduce the effect of the unpsring weight- and have the final drive constantly driven (like a motorbike) You could even chuck a gearbox in there, in theory, though the weight would be a problem. But, that's just a complication, easier to think about it with a conventional rear wheel, in that situation you'd have both of the secondary drive sprockets mounted to a single axle in constant mesh)
You can then have whatever rear axle path you want, and still have the BB being frame mounted, and you're not stuck with a fixed wheel-BB distance like you would be with a unified BB/swingarm pivot.
Not that this is neccesarily a good idea you understand, just an engineering game, but it's a way to get growth into a belt. Or singlespeed/rohloff for that matter.(you'd want to have the ability to grow the conrods, a threaded bar with a left handed thread at one end would do the job, like a motorbike gearshift linkage) Course, it'd also work exactly as well with a chain
Supersonic, I can't really see what's going on with that one, looks like the secondary chain drive is frame mounted rather than floating though? Maybe on the swingarm pivot? This method would only work if you seperate the secondary drive from both.Uncompromising extremist0 -
I can't see that working. maybe a diagram would help? :? 0
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I thought you might say that, so I spent the intervening time preparing a detailed technical diagram.
I've been unable to master any PC CAD program since Micrografx Designer And I can't find a BBC emulator to allow me to use Simcad. Uncompromising extremist0 -
Shaft drive with hub type gear box housed in the BB , reducing unsprung mass and removing alot of the maintenance, and acidental damage issues.
just a thought...0 -
Where's your diagram?
Is shaft drive really practical for pushbikes? It doesn't work well for motorbikes despite being able to make them as massive and heavy as you want, and not having to worry about drivetrain losses.Uncompromising extremist0 -
Love the diagram
I still can;t understand anything going on there though 0 -
But it's OBVIOUS! That bit goes up and down, the other bit sort of waggles about, and they're all connected together apart from where they're not... Obvious.Uncompromising extremist0
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I'll give you the benefit of the doubt, and give you a D-0 -
Offside
Uncompromising extremist0
