Derailleurs...what do you look for in yours?

joshtp

yeehaamcgee wrote:

What's all the fuss about belt dives? What problems do you guys think that is going to solve?

As for Joshtp's

totaly smooth shifts, with no noticable trasition stage

That, has more to do with cassette design. The chain will always have to travel about half a revolution of the cassette to fully change gear. No redesign of rear mech could eliminate that.

no, but a gearbox design like i came up with would, the gear would be changed as the cable was pulled, not as the chain reacted to the mech moving which in itself was operated by a cable.
also, sometimes, occasionaly, when yuor gears are working perfectly, and you time a shift judt perfectly, you get that "instant, no noticable trasition" feeling.

Anonymous

My gears don't "sometimes, occasionally" work perfectly. They just work, perfectly.

I think that that instant shift feeling comes when your rear cassette is spinning really quickly.

Anyway, I didn;t realise you were talking about a gearbox ystem, I thought you were mentioning things you'd like a rear mech to do better.

Jenks66

To be easy to setup and need little maintainance

joshtp

yeehaamcgee wrote:

My gears don't "sometimes, occasionally" work perfectly. They just work, perfectly.

I think that that instant shift feeling comes when your rear cassette is spinning really quickly.

Anyway, I didn;t realise you were talking about a gearbox ystem, I thought you were mentioning things you'd like a rear mech to do better.

My gears too work, perfectly. but sometimes you get that totaly instant feeling, maybe it is when the cassete is spining really fast. the first half of my first post was talking about my gearbox idea, the second part of how perfect gears should be.

tom_goggin

The course I'm doing is called Computer Aided Product Design at Bournemouth Uni, it sits somewhere between Product Design and Design Engineering courses. We've effectively got until the end of the school year to complete the project, but in reality, we need a pretty good concept by Christmas time.

I appreciate your concerns about the amount of progress I could make in comparison to the Shimano's of this world with their experience and money, but the project isnt designed to be completely revolutionary, its about looking problems in a different way, we're designers after all, not inventors!

The feedback you guys have given me is really useful. I know its really easy to overlook simple things in products like ergonomic shifters and the tactile feedback you get when shifting, but these are the areas I'll have to concentrate on when designing the final solution. Keep the suggestions coming!

supersonic

Feedback is interesting as manmy love the smoother change of the Shimano, others the positive shift of SRAM.

Or the vaguenes of Shimano, the clunkiness of SRAM ;-)

An adjuster to change feel?!

NatoED

how about the variable belt drive as stated earlier. DAF used it in a car . it has two cones and a belt drive . as you speed up centrifugal force changes the distances the cane are apart and you get larger gearing for higher speed . it works awesome i'll try to get a link to show you guys.

NatoED

and here it is at work
http://www.youtube.com/watch?v=R8AzqtomwD0

this would be great as you'd do away with shifters completely . no more cables , no more miss shifts . no moving parts as such .

llamafarmer

I did Product Design and Manufacture, so pretty similar. Are you just planning to design a rear mech, or a whole system?

As for the original question I just want to not notice my gears. When they're working well, they shift smoothly, quietly and precisely. If you could eliminate chainslap that would be great. I actually think chains are a good thing because if they break they're pretty easily fixed, carrying a spare belt around wouldn't be as easy as a couple of chain links. In my opinion, low maintenance systems along the lines of hub gears and Hammerschmidt are the future.

NatoED

but belts are far more reliable than chains and can be made out of tough materials (such as kevlar) to resist wear for longer

Anonymous

NatoED wrote:

how about the variable belt drive as stated earlier. DAF used it in a car . it has two cones and a belt drive . as you speed up centrifugal force changes the distances the cane are apart and you get larger gearing for higher speed . it works awesome i'll try to get a link to show you guys.

Not sure it would apply to mountain bikes so well. We sometimes need to spin a gear, and we sometimes need to pick a high gear, and lunge. A system like the DAF one would make it impossible to choose what to do, i reckon.

NatoED

not really think of it more like a single speed for all speeds. the lunge would be similar to stamping of the throttle of the car . it would instinctively adjust itself to what you need it to do .

Anonymous

machinery doesn't have instincts.

Northwind

NatoED wrote:

but belts are far more reliable than chains and can be made out of tough materials (such as kevlar) to resist wear for longer

But can't be shortened or repaired. "Do you have a belt for a 2012 Orange 5 Pro with this exact gearing in stock? No? Oh. Guess I'll just go home and order one and not ride my bike for a week". vs "Do you have a chain? What size? Doesn't matter". "Oh, my chain's broken out on the trails, I'll fix it with a soft link" vs "My belt's extremely unlikely to fail, but I either need to carry a complete spare, or just walk home if it ever does".

I think this might be one of the big problems belts face for cycling... That, and the industry's demented inability to standardise, you know fine well SRAM will have a half inch belt while Shimano will have an 11mm one, and they'll both have different tooth spacings...

Sure, chains and derailleurs are stoneaged, but they're also very effective. And it's not just that they're incredibly well developed, the 21-speed setup on my commuter is about as basic as it comes- some parts of it are older than some of the people posting in this thread, most likely- but it's still reliable and effective. It's just a very practical way of operating a geared bike. Alfine and Rohloff and Hammerschmidt and g-boxes and suchlike are all interesting but there's not one of them that's a mech killer IMO.

The Spiderman

NatoED wrote:

but belts are far more reliable than chains and can be made out of tough materials (such as kevlar) to resist wear for longer

Less chainring and casette wear issues too.

Anonymous

A toothed belt would undoubtedly wear down pretty damned fast in the muck and gloop we ride in.
I'm also concerned about what happens when the drive teeth become clogged, which I'd imagine would happen very quickly indeed.

NatoED

belts are used reliably on quads and snow bikes . Both of which get very mucky (snow bikes get used also in non snow conditions in places like green land.
As to different lengths then never heard of slotted horizontal drop outs? I can't see belt drives being converted for current bikes . They would have to be designed from the ground up for belt drive . I can't see a problem with full sus with belt drive aas you could use a BB pivot like the cove G spot with a rocker actuated single pivot design.

Northwind

Slotted dropouts change the geometry of the bike, as do EBBs (and never heard of them? I did mention both ) but they're not a simple answer, and still only account for a small amount of variation. BB pivot full sussers are generally more awkward to make, and it cuts down on the options for suspension design- frinstance try to get a backward path travel design onto a BB pivot...

Quads and snow bikes don't use fully exposed belts, I believe, though the only quad I've worked on had a chain drive.

NatoED

snow bikes do . In fact snow bikes use a scaled down version of the DAF system for the full race snow bikes. Heck i know it would take alot of work to achieve but i think it should be looked into . OK so it wouldn't work for every sort of bike but for XC i think it would be great.

I think it would take years to get to a ridable state . As it is chains are the best for the moment.

Anonymous

I've never seen a belt drive quad.

NatoED

i've seen 1 from Husgivahna (?) when I was in college doing machine fitting . was designed for use in Norway and Sweden . It was used for forestry work )they found that chains would become clogged and snap with brash wood where as a belt wouldn't

Northwind

Ah, now... I just found a more detailed pic of one of an mtb belt drive, and the sprocket is open at the base of each V...


Have to admit I didn't know they were made like that- there goes the mud issue, mostly.

NatoED

nice find .

Anonymous

Northwind wrote:

Ah, now... I just found a more detailed pic of one of an mtb belt drive, and the sprocket is open at the base of each V...


Have to admit I didn't know they were made like that- there goes the mud issue, mostly.

that's very interesting, but I'm still concerned that the teeth in the belt will fill up with crud.
And I still don't really see an advantage.

Northwind

yeehaamcgee wrote:

And I still don't really see an advantage.

Yeah, that's the rub isn't it. Don't have to grease them, not likely to snap them, but is that worth it? Don't know about anyone else but I'm not on tenterhooks waiting to be freed from the misery of chains.

Anonymous

I don't see that they're any less likely of snapping than a chain.
You're going to have to clean the belt, which i guess would be a similar task to lubing a chain.
You need a gearbox system to drive the rear wheel, and on suspension frames, you need either an idler to take up the slack of the suspension action, OR, you have the driving pulley inline with the swingarm's pivot, which causes major bob issues.

To me, it seems like a solution, that's looking for a problem to solve, whilst simultaneously sticking it's fingers in it's ears about the complications it, itself, brings to the table.

supersonic

How do you fit a new one?

Northwind

yeehaamcgee wrote:

I don't see that they're any less likely of snapping than a chain.

They should be, the load bearing ability of a well made modern belt is huge, and there's no moving parts/soft links etc. Course, being mountain biking it's quite possible that in order to save 10 grams off the belts we'd end up with ridiculously narrow or low profile belts that aren't fit for purpose...

Anonymous

But the breaking strain of a chain is already (normally) far in excess of the power we put through it.

Northwind

And yet it moves, er, breaks. Not that I've ever broken one as I have legs like wet noodles, but it's not uncommon. Then again, quite often neglect related I reckon.