Author Topic: Gates belt drive (Read 3866 times)

chillmoister · « **on:** 11 July, 2019, 01:34:53 pm »

Dear Parishioners

I'm pondering whether to move to a gates belt drive system when I move my Rohloff hub into a new Shand Tam frame. I'm keen to receive some real world feedback for those that have used, still use or have discarded the system. Thanks!

Brucey · « **Reply #1 on:** 11 July, 2019, 02:43:18 pm »

it is a fair bit less efficient than a chain drive; for example on motorcycles (which also have a 'pulsey torque') measured losses of 25% in belt drives are not unusual. The belt drive manufacturers hide this information, providing as they do specious test data which is acquired under constant torque conditions.

There are some advantages to belt drive but IMHO these need to be compelling in a highly unusual way before using a belt drive is 'better'. Sticking the chain inside a chaincase has a lot going for it; you could do that if you wanted.

cheers

Paul H · « **Reply #2 on:** 11 July, 2019, 03:19:25 pm »

Unless it’s changed in the last 18 months, you don’t have the choice, Rohloff were not offering conversion parts when I enquired. I did consider selling my hub and buying new but the expense outweighed my curiosity
EDIT scrub that, the conversion parts are now listed on the Rohloff website

bludger · « **Reply #3 on:** 11 July, 2019, 03:22:22 pm »

The Belgian dude who organised my 400 has a belt drive rohloff on a very pretty ti audax bike. He had issues with one belt working with the hub but since got a replacement and rates the bike very highly.

This guy is an experienced randonneur who has done the lap of France brevet and a bunch of other crazy stuff so I'd trust his judgement.

Gattopardo · « **Reply #4 on:** 11 July, 2019, 04:15:14 pm »

Quote from: Brucey on 11 July, 2019, 02:43:18 pm

it is a fair bit less efficient than a chain drive; for example on motorcycles (which also have a 'pulsey torque') measured losses of 25% in belt drives are not unusual. The belt drive manufacturers hide this information, providing as they do specious test data which is acquired under constant torque conditions.

There are some advantages to belt drive but IMHO these need to be compelling in a highly unusual way before using a belt drive is 'better'. Sticking the chain inside a chaincase has a lot going for it; you could do that if you wanted.

cheers

As you mentioned motorcycles, I'm just wondering what the difference are the transmissional losses are compared to the different kinds of chain (o ring, x ring etc) and how that changes through the wearcycle of the chain compared to a belts wearcycle. Especially as the belt has a tensioner.

Brucey · « **Reply #5 on:** 11 July, 2019, 04:47:22 pm »

Quote from: Gattopardo on 11 July, 2019, 04:15:14 pm

As you mentioned motorcycles, I'm just wondering what the difference are the transmissional losses are compared to the different kinds of chain (o ring, x ring etc) and how that changes through the wearcycle of the chain compared to a belts wearcycle. Especially as the belt has a tensioner.

From memory; there is a small amount of parasitic drag with any 'sealed' chain. I think for this reason motorcycle racers often still use unsealed chains. There are also small differences between seal designs, and bigger differences with lubrication (of rollers and seals). Chains lose efficiency with wear but a chain would practically have to be falling off or rusted solid before these losses might compare with those in a belt final drive.

Probably someone has done some testing which is relevant to this; I'd expect to find something on the interweb without too much difficulty.

Re bicycle belt drives; they can be sometimes be run with less preload if a 'snubber' is use but in many cases the drive isn't reliable unless the preload is roughly equivalent to the peak service load. They measure as reasonably efficient when they are seeing close to their rated load and the load is constant. However this is a very poor match for typical conditions on a bicycle drive, so as I mentioned above manufacturer's test data tends to be 'highly optimistic' in this regard.

Note that part of the reason for the low efficiency is that the belt drive can be stretchy when you are pedalling hard; some folk find this 'pedalling in mush' sensation so off-putting they won't ride a belt for that reason.

On a more trivial note, that does not apply to (original ) Rohloff belt drive conversions - but might apply to those which use the current splined driver- I have seen numerous belt drives clap out on IGHs which use the standard three-lug drive sprocket fitting. What appears to happen is that the preload on the belt causes the sprocket to 'orbit' on its mountings in a way that doesn't happen with a chain drive. The effect is so strong that the sprocket can just wear away and then lose drive. Aluminium centred sprockets are terrible for this but I have also seen it happen with steel-centred sprockets. Its not yet clear to me if the Rohloff belt drive sprockets that fit to the splined driver are susceptible to the same wear or not.

cheers

yoav · « **Reply #6 on:** 12 July, 2019, 12:07:43 pm »

I bought my Shand Stoater Rohloff with Gates belt drive 4 years ago. It’s been no trouble whatsoever in that time and any losses in efficiency have been more than made up in hassle free riding. Just returned from a another 600 mile trouble free tour on it.

rafletcher · « **Reply #7 on:** 12 July, 2019, 12:24:57 pm »

Quote from: Brucey on 11 July, 2019, 04:47:22 pm

Note that part of the reason for the low efficiency is that the belt drive can be stretchy when you are pedalling hard; some folk find this 'pedalling in mush' sensation so off-putting they won't ride a belt for that reason.

I wouldn't have expected a Gates belt with Kevlar cords to be significantly elastic. And enough of the teeth would be engaged such that deformation of individual teeth would be insignificant.

bludger · « **Reply #8 on:** 12 July, 2019, 01:59:53 pm »

For an extra layer of 'look at how much dough I have', they're selling a gates drive titanium MTB with a pinion gearbox and a gates drive in cloud 9 cycles right now.

quixoticgeek · « **Reply #9 on:** 12 July, 2019, 02:03:29 pm »

Quote from: bludger on 12 July, 2019, 01:59:53 pm

For an extra layer of 'look at how much dough I have', they're selling a gates drive titanium MTB with a pinion gearbox and a gates drive in cloud 9 cycles right now.

Nah, the "Look how much money I have" version, combines the 18 speed pinion gear box, the gates belt drive, *and* a rohloff hub! :p

J

bludger · « **Reply #10 on:** 12 July, 2019, 03:52:39 pm »

Now we're cooking with gas!

Kim · « **Reply #11 on:** 12 July, 2019, 04:40:12 pm »

A couple of years ago I test-rode a sensible city e-bike fitted with such (Bosch mid-drive motor driving a Nexus hub, or similar, I lose track). Obviously no real concerns about efficiency there - the idea was low maintenance. Alas the manufacturer had made the classic mistake of choosing a gear ratio appropriate for an equivalent non-electric bike, possibly as a result of parts availability.

Similarly, I've seen it used to good effect on folding bikes, where the advantages of an oil-free drivetrain are obvious.

Dtcman · « **Reply #12 on:** 12 July, 2019, 05:10:58 pm »

I rode a 1000 audax in Belgium a couple of years ago and there were a few riding Gates belt drive on a Rohloff. I was very impressed and would still like it.

However, when I specked up a new bike: titanium frame with discs, Gates belt drive on a Rohloff working off STI leavers with the conversion gearbox, it came out at around 5000 euros and I decided otherwise! I would still go for it if I had the money.

Brucey · « **Reply #13 on:** 12 July, 2019, 05:30:26 pm »

Quote from: rafletcher on 12 July, 2019, 12:24:57 pm

I wouldn't have expected a Gates belt with Kevlar cords to be significantly elastic. And enough of the teeth would be engaged such that deformation of individual teeth would be insignificant.

belts do vary in stiffness; are not the gates ones carbon-reinforced for better stiffness than Kevlar reinforced ones?

Has anyone used the current rohloff parts (i.e. on the splined driver)? Are there any signs of wear on the splines between the sprocket and driver?

One of the features of belt drive that has only been tangentially mentioned is that of gearing; there are only a few belt lengths, front wheel and sprocket sizes; more or less you need to choose your gear ratio when the frame is built; there is somewhat limited scope for changes afterwards.

Belt drives can be very reliable if they are set up right. Unfortunately you also can't completely exclude the possibility that the belt will break e.g. through a stone being thrown up into it. This possibility is addressed in motorcycle belt drives by carrying a repair kit; dunno if it is any good or if it is more a safety blanket for the mind, but the resultant join is not full strength; more a 'get you home' rather than a 'carry on regardless'. Chains are not especially reliable but they are easily repaired by the roadside and are very easily replaced; you can buy a new chain in any town more or less.

I'd liken some of the benefits of belt drives to those of puncture proof tyres; with a good setup there is less faffing about, but the price you pay is that you are probably a bit slower, everywhere.

cheers

bludger · « **Reply #14 on:** 12 July, 2019, 06:03:59 pm »

The thing that mostly put me off belt drives was when a load of Continental's just snapped on people (see recall info at bottom https://www.canyon.com/en-gb/customer-service/recall-safety-advice-page.html ). IDK how common this is among other BDs.

Gattopardo · « **Reply #15 on:** 12 July, 2019, 07:01:10 pm »

Quote from: rafletcher on 12 July, 2019, 12:24:57 pm

Quote from: Brucey on 11 July, 2019, 04:47:22 pm

Note that part of the reason for the low efficiency is that the belt drive can be stretchy when you are pedalling hard; some folk find this 'pedalling in mush' sensation so off-putting they won't ride a belt for that reason.

I wouldn't have expected a Gates belt with Kevlar cords to be significantly elastic. And enough of the teeth would be engaged such that deformation of individual teeth would be insignificant.

Was going to mention reinforced toothed belts, Also non stretchy v belts in a wondering sort of way.

Gattopardo · « **Reply #16 on:** 12 July, 2019, 07:06:57 pm »

Quote from: Brucey on 12 July, 2019, 05:30:26 pm

Quote from: rafletcher on 12 July, 2019, 12:24:57 pm

I wouldn't have expected a Gates belt with Kevlar cords to be significantly elastic. And enough of the teeth would be engaged such that deformation of individual teeth would be insignificant.

belts do vary in stiffness; are not the gates ones carbon-reinforced for better stiffness than Kevlar reinforced ones?

Has anyone used the current rohloff parts (i.e. on the splined driver)? Are there any signs of wear on the splines between the sprocket and driver?

One of the features of belt drive that has only been tangentially mentioned is that of gearing; there are only a few belt lengths, front wheel and sprocket sizes; more or less you need to choose your gear ratio when the frame is built; there is somewhat limited scope for changes afterwards.

Belt drives can be very reliable if they are set up right. Unfortunately you also can't completely exclude the possibility that the belt will break e.g. through a stone being thrown up into it. This possibility is addressed in motorcycle belt drives by carrying a repair kit; dunno if it is any good or if it is more a safety blanket for the mind, but the resultant join is not full strength; more a 'get you home' rather than a 'carry on regardless'. Chains are not especially reliable but they are easily repaired by the roadside and are very easily replaced; you can buy a new chain in any town more or less.

I'd liken some of the benefits of belt drives to those of puncture proof tyres; with a good setup there is less faffing about, but the price you pay is that you are probably a bit slower, everywhere.

cheers

There is a belt repair kit?

The belts I've seen damaged have usually been shredded, wonder how the repair kit would work. Benn trying to think of belt drives and can think of the BMW funduro aprilla moto thing and harleys (v twin) there are some that have wide belt drive from the engine to the gearbox and the from the gearbox to the rear wheel.

Kim · « **Reply #17 on:** 12 July, 2019, 07:22:24 pm »

Presumably a belt on a bicycle fails a bit more gracefully than the fanbelt on a car, for example, as the speed is much lower and drive is removed at the first *slip* *clunk* "OWMENADS!"

Brucey · « **Reply #18 on:** 12 July, 2019, 07:41:57 pm »

this is what the well-prepared HD rider may carry. IIRC there are (wire?) clips that join the ends of the belt together. In this case I think the motivation is to avoid having to fit an endless belt, which is more of a workshop than roadside job on such a motorbike. IIRC there may be another kit which uses two splices so that you can replace a short length of belt but maybe I'm misremembering things.

I guess if you really wanted to you could carry a spare belt on a bicycle, it wouldn't weigh much. However toothed belts are rather fussy about how they are stored; tight bends are not tolerated well and can damage belts that are stored badly.

cheers

LittleWheelsandBig · « **Reply #19 on:** 12 July, 2019, 08:47:58 pm »

I've ridden quite a bit with a fellow who spliced a Strida toothed chainring, sprocket and belt onto a Moulton New Series many years ago. He used to carry a spare belt with him as the belt had a tendency to break if he pedalled too hard. When the Gates belt became available, he swapped the Moulton to that system and hasn't broken a belt since. Apparently a snubber keeps everything working nicely. No offroading, mind you.

mzjo · « **Reply #20 on:** 14 July, 2019, 11:26:58 pm »

A few years ago there was the guy who set a round the world record with a Rolhof hub and a Gates belt drive. The bike was dutch, I think the make was Santos, who did a lot with bely drives. I was curious enough to download the Gates doc? The one thing that was apparent was that belt alignment and tension were critical for correct lifespan. The round the world guy had one premature belt failure which was due to a bad line-up after a wheel removal for a puncture. Apart from that he had no problems. I will have lost all the links long ago otherwise I would post them.

yoav · « **Reply #21 on:** 15 July, 2019, 07:07:16 am »

That guy was Mark Beaumont, I think. It certainly a lot easier and probably more reliable if the bike is built for the Rohloff/Gates setup rather than retro fitted. The Shand’s frame has special dropouts and an eccentric bottom bracket that makes fitting and tensioning the belt a doddle and the belt hasn’t lost any tension (or ‘stretched’) to any noticeable degree in 4 years. Gates do a phone app that ‘listens’ to the belt when you pluck it (like a guitar string) and tells you if the belt tension is correct.

Paul H · « **Reply #22 on:** 15 July, 2019, 02:53:07 pm »

Quote from: yoav on 15 July, 2019, 07:07:16 am

That guy was Mark Beaumont, I think.

It was James Bowthorpe, who beat Beaumont's record but was never ratified as Vin Cox beat it again shortly afterwards (On a bike with an 8 speed Alfine hub which shows that it's not all about the bike!) Mark Beaumont was using a Rohloff, though it was a Koga (Who he still has sponsorship from) and it predated the belt versions.

Brucey · « **Reply #23 on:** 15 July, 2019, 03:14:28 pm »

Vin Cox's bike;

https://www.bikeradar.com/road/interview-round-the-world-cycle-record-holder-vin-cox/

said to be a Genesis Croix de Fer; not sure how the chain slack was accommodated.

[edit; is that a single pulley CT-S510 tensioner I can just see....? I think that would be the correct one for that frame...?]

cheers

yoav · « **Reply #24 on:** 16 July, 2019, 01:27:55 pm »

I stand corrected, thanks.