Belt drive instead of chain..why? why not?

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Brucey
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Re: Belt drive instead of chain..why? why not?

Postby Brucey » 21 Jun 2020, 12:16am

in the article above I think they use manufacturer's data for transmission efficiency. This isn't representative of all belts (they vary) and furthermore I think it is almost certain to be at constant torque. I don't think I have seen any manufacturer's data for a pulsy torque load; constant torque measurements are much easier to make and flatter stretchy/flexy transmissions like belt drives, so that is why they are used.

It is said that belts are not used in racing because they are allied with (relatively) heavy and inefficient gearboxes. If that were the only reason and it really was the case that at higher power outputs 'a belt is lighter and more efficient' as is claimed, it is absolutely certain that belts would be used for track racing. I think the fact that they are not is evidence enough of the specious and misleading nature of the arguments that proponents of belt drives will present.

cheers
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Mike_Ayling
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Re: Belt drive instead of chain..why? why not?

Postby Mike_Ayling » 21 Jun 2020, 4:29am

Brucey wrote:in the article above I think they use manufacturer's data for transmission efficiency. This isn't representative of all belts (they vary) and furthermore I think it is almost certain to be at constant torque. I don't think I have seen any manufacturer's data for a pulsy torque load; constant torque measurements are much easier to make and flatter stretchy/flexy transmissions like belt drives, so that is why they are used.

It is said that belts are not used in racing because they are allied with (relatively) heavy and inefficient gearboxes. If that were the only reason and it really was the case that at higher power outputs 'a belt is lighter and more efficient' as is claimed, it is absolutely certain that belts would be used for track racing. I think the fact that they are not is evidence enough of the specious and misleading nature of the arguments that proponents of belt drives will present.

cheers

My LBS owner told me once when I was getting a sprocket for my fixie that many track riders change their gear ratio frequently, no so easy with belt drive.

Mike

Mike_Ayling
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Re: Belt drive instead of chain..why? why not?

Postby Mike_Ayling » 21 Jun 2020, 4:47am

I recently read a journal on CycleBlaze. A Canadian couple purchased Tout Terrain tourers from the American head agent. They noticed that the wife's belt and sprocket were showing abnormal wear and did not receive any useful advice from the place that they got the bikes.
On tour in Europe the belt broke but was easily replaced by the owners. I think that they obtained a new sprocket on line from Gates Europe and called in at the next Rohloff accredited bike shop to install the sprocket. Several bike shops later it turned out that the sprocket removal tool was a Gates product and not a Rohloff one. Eventually the sprocket was installed and they continued on their way. They later called in at Tout Terrain head office mainly to see the place and they were told that the wear and belt breakage was due to an incorrect belt line. TT provided excellent after sales service correcting the belt line ang gave both bikes a free service each having done about 9,000 kms. They have now converted to the splined sprocket carrier which still requires a special Gates tool to assist in the removal. He still believes that the belt drive is the greatest!

Mike

Brucey
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Re: Belt drive instead of chain..why? why not?

Postby Brucey » 21 Jun 2020, 9:58am

Mike_Ayling wrote:My LBS owner told me once when I was getting a sprocket for my fixie that many track riders change their gear ratio frequently, no so easy with belt drive.


and they are correct in that this would deter an average Joe from using belt drive at the track. Nonetheless if there were the slightest thing to be gained by using a belt drive you would soon see belt drive parts allowing a wider choice of gear ratios being used in Olympic track events, regardless of the cost (and the fact that the parts would not only have to be made at all, but also have to be made commercially available ).

I have been lucky enough to attend a talk given by the technical director of British Cycling in which he explained that a significant factor in the team GB Rio medals haul was the fact that they were able to increase the transmission efficiency from ~0.980 to ~0.985. In some events this allowed athletes of the same power etc as their opponents to beat them. They achieved this 0.005 increase in efficiency by using careful choice of chain etc and slightly larger chain and sprocket sizes to yield any given gear ratio. This resulted in lower chordal losses.

This effect ain't rocket science and was well known. However it has largely been ignored at best and dismissed as 'unimportant' by most cyclists, in good part I suspect because it flies in the face of the (IMHO largely idiotic) trends in road transmissions. Road riders are, it seems, easily seduced by the facile 'lighter weight!' and 'wide range!' claims of the manufacturers whenever they manage to lose a chainring or fit a smaller sprocket at the back. [Right now all your transmission parts are being rendered obsolete by a new generation of designs whose sole raison d'etre is that they better allow a 10T sprocket to be fitted; Moulton owners should be pleased; everyone else should be annoyed that something so moronic is occurring.]

Who cares if you actually go more slowly? Well, er, racers, that's who. They will be paid to ride whatever the manufacturers want them to provided a) it is allowed and b) it doesn't actually disadvantage them vs their opponents. So disc brakes, yes, (but not if you want to win the TdeF...) but not 1x transmissions with idiotic 10T sprockets. They are reserved for 'the gullible', uh, I mean 'general public'.

If you are charitable you can say you have different priorities and that is why you use a given transmission type; that argument applies to IGHs etc. Ironically IGHs already use the cheapest, most efficient/reliable/flexible (in terms of gear ratio choice) chain and sprocket parts, requiring the least maintenance. Yet this is exactly where folk are merrily trying to encourage you to use a belt drive instead. I have no doubt that the parts ought to continue to improve; just as well because I would characterise the ones I have seen as 'mostly not very good' to date.

If I wanted to spare myself some maintenance time and accept a speed penalty, it is very simple; just don't pump your tyres up so often.

cheers
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mercalia
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Re: Belt drive instead of chain..why? why not?

Postby mercalia » 21 Jun 2020, 10:28am

do cycle belts have a metal core? I think those for motor cycles do.

zeluzel
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Re: Belt drive instead of chain..why? why not?

Postby zeluzel » 21 Jun 2020, 10:45am

NickJP wrote:One heavy-duty user's viewpoint:
https://www.cyclingabout.com/belt-drive-best-bicycle-drivetrain/

It's the same guy who did the video I posted ;).

mercalia wrote:do cycle belts have a metal core? I think those for motor cycles do.

Nope, it's carbon fiber they're reinforced with.

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Cunobelin
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Re: Belt drive instead of chain..why? why not?

Postby Cunobelin » 21 Jun 2020, 11:04am

I have a couple of the early Strida's

THey required careful acceleration as too much pressure would cause the belt to slip ion the teeth

Brucey
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Re: Belt drive instead of chain..why? why not?

Postby Brucey » 21 Jun 2020, 11:06am

zeluzel wrote:Nope, it's carbon fiber they're reinforced with.


well, some are (eg gates carbon drive) but most are not. They can be reinforced with carbon, glass or Kevlar fibres. Or a mixture.

cheers
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zeluzel
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Re: Belt drive instead of chain..why? why not?

Postby zeluzel » 21 Jun 2020, 12:00pm

Cunobelin wrote:I have a couple of the early Strida's

THey required careful acceleration as too much pressure would cause the belt to slip ion the teeth

Didn't they use Continental belts? Perhaps they need to be tightened hard, just as previous Gates CDC design.

Brucey wrote:
zeluzel wrote:Nope, it's carbon fiber they're reinforced with.


well, some are (eg gates carbon drive) but most are not. They can be reinforced with carbon, glass or Kevlar fibres. Or a mixture.

cheers

Well, K was thinking about Gates, as it seems that they're the only company that can be treated seriously to date :).

After watching that guy's video and seeing how loosely he puts on his belt, I'm convinced. If it had to actually be tightened I'd dismiss it right away, as it'd add hell lot of friction to whole transmission.

I rode a belt drive only once and shortly, but didn't feel any sponginess (and it was on Alfine, which you claim to add more of that feeling). But I can imagine there's more flexibility to rubber/carbon than steel, so they probably are less efficient. That said, if that guy stands by it, I'd say I'll take that as a cost. He convinced me that, if set up correctly, they do offer the most maintenance free design, which is exactly what they advertise.

Brucey
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Re: Belt drive instead of chain..why? why not?

Postby Brucey » 21 Jun 2020, 12:34pm

zeluzel wrote: so they probably are less efficient....


definitely, not probably.

That said, if that guy stands by it, I'd say I'll take that as a cost. He convinced me that, if set up correctly, they do offer the most maintenance free design, which is exactly what they advertise.


there is a risk/vs consequence thing going on here; in high mileage applications (where belt use might have some attraction) there is always a chance that the transmission will fail in some way. I've never myself had a chain break completely on the road, but I have had one crack a sideplate and I have seen it happen to other people. This risk is usually mitigated by carrying a spare QL and some tools. Chains can be bought everywhere, so all a repair has to do is last for a relatively short time, even if it is imperfect. With a belt drive, even if the risk is lower (which I'm not sure it is, a stone that tries to go between the belt and pulley will wreck it instantly, and belt drive pulleys are basically troublesome for various reasons) how do you mitigate the risk? Carry a spare belt, pulley and tools to fit it? I think this would be wisest, given that belts and pulleys are not widely available; where I live (which has lots of bikes and bike shops) the typical outcome of a bike needing belt drive repair is that the parts are not readily available (if at all) and the bike can be off the road for days or weeks whilst the parts travel from where they are (often in another country) to where you are. And that is if you can get them at all. FWIW even carrying a belt is not straightforward; belts don't like to be creased in certain ways, so some kind of hard container or separate pocket seems like a good idea; I think creasing is quite likely if a belt is in a bag and that bag is in a pannier along with a load of other stuff.

Belt drives ought to have the same (or more) advantages for motorcycles. But uptake has been slow. IIRC actual measurements of motorcycle transmission efficiency using a belt drive show a remarkably low efficiency, far lower than the manufacturers predict (on the basis of constant torque measurements). I think the difference is because (like your legs) a motorcycle engine produces very pulsy torque, and a belt is inherently lossy when used in this way.

To mitigate the risk of belt breakage on a touring motorcycle, you can carry a spare belt with a stapled joiner that can be installed by the roadside. However it isn't a perfect repair; it is at best a 'get-you-home'. No similar thing exists for bicycle belts.

Chains are far from perfect, but they are inherently efficient (which usually trumps most other considerations when human power is used) and there are ways and means of learning to live with their shortcomings. I think neither thing is as true for belt drives.

cheers
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zeluzel
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Re: Belt drive instead of chain..why? why not?

Postby zeluzel » 21 Jun 2020, 4:34pm

Well, I guess one has to just try it for him/herself. I guess it's the same thing as with IGHs - some love it, some hate it. You definitely make a good point here, but, in contrary to what you try to prove, I still see good reasons to give it a try one day.

Cheers ;).

Cyril Haearn
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Re: Belt drive instead of chain..why? why not?

Postby Cyril Haearn » 21 Jun 2020, 5:03pm

Doubtless there are inventions that are or could be better than what went before, but are not adopted widely, maybe through failure to achieve 'critical mass' and to reduce costs

The Wankel motor, for example
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John Holiday
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Re: Belt drive instead of chain..why? why not?

Postby John Holiday » 21 Jun 2020, 5:48pm

Have used a belt drive Moulton TR2,which have found to be excellent winter bike. Easily transported as seperable.
My ideal tourer would probably be Rholoff with belt drive.

zeluzel
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Re: Belt drive instead of chain..why? why not?

Postby zeluzel » 21 Jun 2020, 9:50pm


Cyril Haearn
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Re: Belt drive instead of chain..why? why not?

Postby Cyril Haearn » 21 Jun 2020, 9:58pm

Belts are generally used to drive alternators and water pumps in cars
Why are they suitable instead of chains?
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