Author Topic: Belt drives?  (Read 3027 times)

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Offline sanuk

Belt drives?
« on: November 18, 2011, 08:25:48 am »
This may have been discussed before, but I've recently seen a video of some guy cycling through India showing how these things are supposedly almost indestructable.  He deliberately cut his almost in half for the promotional video just to show how tough it is and continued cycling with it.  Guess he had a spare.  You have to have hub gearing too - which I'm contemplating, and lower weight and maintenance are advantages.  However, if they're so good how come they're not more popular? Any thoughts or experience ?

Offline bogiesan

Re: Belt drives?
« Reply #1 on: November 18, 2011, 08:51:02 am »
Belt drives have been around as long as the safety bicycle has been around but chains have always been the favorite drive coupler for many reasons including economics and efficiency. Recent advances in internal gearing and materials to build belts have changed that equation. But you're also seeing a trend among many bike mfrs in simply being different and appealing to a niche.

The topic is easily researched on the Net and there will be interesting developments over the next few years.

I've demo'd the fixies and cruisers at the shops here in Boise. The drive is smooth and silent, shifting on the hubs is fun (takes me back to my first 3-speed from Pennys, 1965). The whole package looks good for touring if it might be a bit heavy and, if you want a wide range of inches, much more expensive than conventional derailers.

Thanks for opening the topic, I'll be watching to see what comes up.

I play go. I use Macintosh. Of course I ride a recumbent

Offline waynemyer

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Re: Belt drives?
« Reply #2 on: November 18, 2011, 12:11:17 pm »
You have to have hub gearing too - which I'm contemplating, and lower weight and maintenance are advantages.  However, if they're so good how come they're not more popular? Any thoughts or experience ?
  • Requires a special frame design (split in the rear to accommodate the belt).
  • A hub transmission of equivalent gear range will weigh much more than a similar derailleur and cassette combination.
  • The hub transmission costs a lot more.
  • Replacement parts are not as ubiquitous as for chain and derailleur drivetrains.
  • Belt drives place a lot of load on the bearings for the rear wheel and bottom bracket. Bearing life is markedly reduced and wear is asymmetric, side to side.
  • In order to get the gear range of a chain and derailleur, e.g. a triple with a 11-34 cassette, a front planetary transmission would be required, e.g. Schlumpf, Hammerschmidt, Patterson. Large expense, high weight, and, with the exception of the Patterson, requires a special frame or special facing of the bottom bracket shell.

That said, I think IGH/belt drivetrains are great. The durability of the drivetrains is legendary. They are perfectly suited to commuter bicycles (the mainstay of IGH/belt bikes) and the durability is well-suited to mountain biking (where IGH bikes are catching on, the last time I was paying attention).

All engineering is mitigating compromises. The modern chain/derailleur drivetrain is the pinnacle of a century of engineering balance between all of the compromises. What we have is plenty good enough and cheap enough that gyrating to upgrade for the sake of upgrade is chasing diminishing returns or attempting to put a square peg in a round hole.  I am sure that, once IGH/belt drivetrains have a couple decades of similar engineering prowess, the popularity will be closer to what you expect.
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Offline whittierider

Re: Belt drives?
« Reply #3 on: November 18, 2011, 01:33:18 pm »

See this recent topic.  The belt itself is not the problem.  It's everything else that goes with it.

Offline sanuk

Re: Belt drives?
« Reply #4 on: November 19, 2011, 04:13:52 am »
Thanks for the feedback.  I'm far from sold on the belt concept and appreciate the info. It was mainly curiosity. Was wondering how they fitted on the bike! However, integrated hub gears make a lot of sense. Deraileurs may be at their pinacle but personally I find them a pain for touring in terms of maintenance, vulnerability to the elements and whatever might get in their way. Roloff have a good reputation although they are costly and heavier and make taking out the wheel more complex. Can't have it all.

Offline whittierider

Re: Belt drives?
« Reply #5 on: November 19, 2011, 05:49:57 am »
Both derailleur and internally geared hub have a shift cable that has to be kept in adjustment (only when it's new and is still stretching, or, as some would argue, only has that effect); but otherwise I have not done anything to my rear derailleur in its 27,000 miles other than clean it when I want it to look purdy.  It works perfectly, but I don't take it off-road and get it gunked up with mud.  I use the Performance ball-bearing derailleur pulleys.

Offline indyfabz

Re: Belt drives?
« Reply #6 on: November 19, 2011, 11:26:25 am »
http://co-motion.com/index.php/singles/americano_rohloff

There is a Gates belt drive option with a low gear equivalent to a 22x34.

I seem to recall an article on the belt drive version in a relatively recent edition of "Adventure Cyclist."

Offline waynemyer

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Re: Belt drives?
« Reply #7 on: November 19, 2011, 11:48:14 am »
Deraileurs may be at their pinacle but personally I find them a pain for touring in terms of maintenance, vulnerability to the elements and whatever might get in their way. Roloff have a good reputation although they are costly and heavier and make taking out the wheel more complex. Can't have it all.
Definitely can't have it all; again, it's a matter of mitigating all of the compromises.

I don't know what you're thinking about with regards to maintenance and vulnerability with derailleurs. Yes, the drivetrain is all hanging out there like a nadsack waiting for a kick, but it's a pretty hardened sack. Anecdotally, my Deore LX derailleur has about 60,000 miles. I have replaced the pulleys a handful of times. I'm still using the original cage bolts, but they are about completely cammed-out now. I clean this thing maybe once a year or so. I live in wet Portland OR, but used to live in salty, sandy, snowy Vermont. My front derailleur is a trashy C101 (it came stock) and it's just a science experiment in equipment abuse.

Bear in mind that an IGH does require maintenance, specifically oil changes. And in the case of some hubs, it is a proprietary oil. I think you're on the right track: the recent round-the-world record was set using a Rohloff/Gates drivetrain. The guy is an experienced tourer and he claimed that he would not have been able to pull off the record using a standard drivetrain. As it was, he still went through two (three?) belts. Then again, if I recall correctly he was sponsored by Gates and Rohloff, so take that as you will.

Both derailleur and internally geared hub have a shift cable that has to be kept in adjustment (only when it's new and is still stretching, or, as some would argue, only has that effect)

With Rohloff hubs, the indexing is internal to the hub, so cable bed-in is much less of an issue, if at all.
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Offline DaveB

Re: Belt drives?
« Reply #8 on: November 20, 2011, 09:30:11 am »
At this point the biggest inhibitor to the wider use of belt drive is that it can't be retrofitted to existing frames.  You have to be able to "split" the driveside chainstay or seatstay to get the belt routed properly as the belt can't be separated and rejoined like a chain so a purpose-built frame is required.

All of the other "negatives" such as limited gearing range, etc. are minor for most uses except loaded touring and that's not a big part of the market.  For casual or utilitarian riders the cleanliness and low maintenance of a belt drive are very attractive. 

Waynemyer's note that belt drives put higher loads on the hub and bottom bracket bearings and that these loads are asymetric puzzles me.  Is it because the belt pulleys are wider and the loads are cantilevered further outboard?  I've never seen this as a problem before. 

Offline waynemyer

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Re: Belt drives?
« Reply #9 on: November 20, 2011, 01:25:25 pm »
Waynemyer's note that belt drives put higher loads on the hub and bottom bracket bearings and that these loads are asymetric puzzles me.  Is it because the belt pulleys are wider and the loads are cantilevered further outboard?  I've never seen this as a problem before. 
The belts have to maintained under high tension. The constant tension causes drive-side bearings to wear faster, just like it does in motorcycles (I used to own a belt-drive motor pickle). Strict attentiveness to chainline reduces bearing wear, but the increased loading is still there.

Because of the high tensions required for Gates' current design and the ratcheting (slippage) issues, they have redesigned their system a few times, including the upcoming CenterTrack belt. They also increased the cog/ring sizes to help reduce the amount of tension required to prevent ratcheting. The increased ring size means on some frames that the ring and cog have to be even further outboard, providing a longer moment arm by which the belt can stress the bearings. Even with Gates' changes, reports of early bearing failure with even heavy-duty bottom brackets are still floating around, although anecdotal*. If the system was anything near ideal, Gates would not keep changing its design and specs so much. These are not cosmetic or model-year changes we're talking about, but deep, serious design shifts, including the necessary changes to the bicycle frame, e.g. chainstays need to be beefed up to handing the longitudinal loading from the belt.


*Outboard bearing bottom brackets already wear more quickly than an internal cartridge BB.**
**If there weren't so many issues, Gates wouldn't keep making so many changes.
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Offline whittierider

Re: Belt drives?
« Reply #10 on: November 20, 2011, 03:52:24 pm »
Quote
*Outboard bearing bottom brackets already wear more quickly than an internal cartridge BB.**
Uh, where did you get that?  Outboard-bearing BBs last far longer, for two reasons.  One is that there's room for more and bigger ball bearings.  The other is that there's less force on them since they're father apart.  The wider stance on them results in less leverage up & down with pedaling, and less forward & back with chain tension.  In fact, with a triple, the right-side bearing is almost in the plane of the middle ring.  I'm on my outboard-bearing BB, and it has 27,000 miles on it and it feels and acts brand new, totally smooth and with no slop.  I've never had any inboard-bearing BB last anywhere near that long.

Edit: That's with a lot of out-of-the-saddle climbing and other hard riding.  Our younger son had the Isis type sealed inboard-bearing BB for awhile, and even though he only weighed 120 pounds at the time, he was wearing one out every 3,000 miles.  The owner of our LBS was using Ultegra and Dura-Ace Octalink ones and he said they weren't lasting him any more than a few thousand miles each, either.
« Last Edit: November 20, 2011, 11:04:53 pm by whittierider »

Offline DaveB

Re: Belt drives?
« Reply #11 on: November 20, 2011, 04:50:17 pm »
  I'm on my outboard-bearing BB, and it has 27,000 miles on it and it feels and acts brand new, totally smooth and with no slop.  I've never had any inboard-bearing BB last anywhere near that long.
I have.  My current Shimano BB-6500 Octalink triple bottom bracket has 32,000 miles on it and it's still going strong with no signs of any play or other problems.  In the past I've put about 30,000 miles each on a couple of Shimano BB-UN7X square taper cartridge bottom brackets and replace them only because I was "upgrading" to something else, not due to failure.

Offline waynemyer

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Re: Belt drives?
« Reply #12 on: November 21, 2011, 10:29:11 am »
Quote
*Outboard bearing bottom brackets already wear more quickly than an internal cartridge BB.**
Uh, where did you get that?  Outboard-bearing BBs last far longer, for two reasons.  One is that there's room for more and bigger ball bearings.  The other is that there's less force on them since they're father apart.  The wider stance on them results in less leverage up & down with pedaling, and less forward & back with chain tension.  In fact, with a triple, the right-side bearing is almost in the plane of the middle ring.  I'm on my outboard-bearing BB, and it has 27,000 miles on it and it feels and acts brand new, totally smooth and with no slop.  I've never had any inboard-bearing BB last anywhere near that long.
Oh, I know about the physics of outboard BB, but the reality of their longevity is a different matter. I'll start with the bikes that come through my shop with outboard bottom brackets. I frequently get bikes less than a year old needing new bearings (three in past month alone). I see this as a potential combination of two factors: shoddy facing or a complete lack thereof, or bearings hanging out in the Portland elements with about 9 months of dousing. While the need for more diligent facing is not explicitly a fault of the outboard BB, it becomes a problem with the system since the outboard BB requires installation attention that it is not usually getting.

I have gotten a couple years out of my outboard BB before needing replacement, but haven't yet replaced the square taper on my do-everything bike in the same period with about triple the miles. I attribute this difference to nearly constant road spray on the bottom bracket. The square taper is Shimano UN-54; do a search, the longevity of these things is legendary. And when it comes time to replace, it will only cost about $25.

I still prefer outboard BBs when possible, if only for their ease of installation and replacement. But I am firmly unconvinced it is a durable technology. Amongst people who wrench regularly, the stories of sub-5000 mile bearing replacement are legion.
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Offline mootoxybb

Re: Belt drives?
« Reply #13 on: December 12, 2011, 09:15:12 pm »
Hello everyone, I have a Co-motion Americano belt drive rohloff and just love the whole system.  Runs super quiet, never need to mess with a chain (big plus), especially after 92 miles and over 6000' on a loaded touring bike.  :P  The system is amazing and combined with a rohloff well you just pedaled into bicycle heaven.  Yes it's a bit heavy than traditional but not by as much as you would think.  I always carry an extra belt when touring, tire changes are easier than traditional because Co-Motion really thought out the whole thing with vertical dropouts and a external gear mech. on the rohloff and an ECC BB.  I am so sold that I'm selling my Moots 29er and having Kent Eriksen build me a belt drive rohloff ti 29er frame.  For anyone out there wondering about wear and tear on bearings, yes the belt tension is critical (buy the tool).  Being an ex- Air force fighter mechanic, no system is perfect but anyone looking at rohloff with a belt drive is getting close.  Like anything else some folks hate em and some likes em, you know where I stand or sit I should say.
If it has 2 wheels and your legs are going up and down, life is good...Oh if you're worried about outboard BB go with a Chris King and don't look back (regular maint. is required).  ;)