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Belts set to replace Bike Chains? Answered

Apparently belt driven bikes were produced a few years ago by specialist bike companies but they are now about to hit the mainstream.

These belts have an advantage over chains because they are tougher, last longer, aren't dirty or greasy, their quieter and they weigh a lot less.

the only drawback is the price, Trek has unveiled, the District and the Soho, will run you $930 and $990, respectively. but then again all new tech is expensive :D

Via Gizmodo


While a good idea, I still doubt belts will get anywhere major in the bicycle world... A broken chain is easily fixed, a belt must be replaced. A chain is installed in two pieces, whereas with a belt the frame must be able to seperate to allow the belt into the frame, unless you use downhill bike style chainstays (which are heavy, not road bike friendly). This is either expensive or creates a weak point in the frame, or possibly both. Really, even the lack of lubrication isn't a big deal, with a belt drive you're pretty much limited to internal gearing and singlespeeds, and an unlubricated bike chain on a singlespeed will still last a long long time (assuming the chainline is straight) and be highly (likely over 90%) efficient. Cool idea, no doubt, but I honestly don't see the benefits (mainly lack of lubrication) outweighing the cost of changing an industry, re-engineering the bicycle frame (or using current tools like S&S; couplings– which are expensive)...

You've got a good point on the chain lasting a long time. I can't remember ever having to replace a chain, except the one that snapped. However, consider these points:  *  Quiet operation; I would much rather hear the environment, either wildlife or traffic, then the racket my bike makes currently (probably due to the above mentioned lack of care of the chain, granted).  *  Internally shifted is the way to go; Far more reliable then standard shifting bikes, but at an initially higher cost. I have never had to replace an internally geared hub, but derailers come and go.  Point of weakness in the frame; Yes, perhaps it will be weaker, but how much, and will it matter that much to a commuter? As for the chain being installed in two pieces, well, I've only had to replace the one chain, ever, and I don't know anyone who carries a spare, but at that weight and size, I'd consider throwing one in my bag with my flat kit.

Just saw how long ago the original comment was posted, ignore mine if you wish, of course.

I must agree that belts are probably not such a good idea on bicycles. Belts have made some headway on low powered cruiser type motorcycles but that is a different world than bicycling. A drive shaft and gear system might be nice in certain situations but I think I'll stick with chains. I will say that nylon sprockets worked out well in motorcycling and plastic sprockets might be a nice feature for bicycles as well. They are quiter and somewhat self lubricating.


7 years ago

I would think the sun would wear it out. I also tend to stand on the top of my stroke.... I'd kill it!

why would a stupid piece of rubber be that much money and a couple of sprockets?

Well, its a "new" technology, there are fine tolerances... tires are expensive too, and all they are is round...

not to be a fact nazi, but your statement seems to imply that tires are made entirely of rubber. In fact, the rubber on a tire serves mainly to protect the structurally crucial fabric and bead, and to provide traction. Its structural role is insignificant. This applies to all pneumatic tires(If you knew this just take it as a lesson for other less bike-oriented people)

I did seem to imply that. And you are right. I've learned quite a bit in the last few years. :D

I know but who cares if they make a high quality tire that takes just a little longer to make than a low quality tire that takes just a little less the should have relatively the same price just a little more for the better one. I just don't under stand it's like after you make one tire you can make a machine that makes thousands of them an hour even if you put 20 years in to it.

But how do you switch gears? I wouldn't pay over $900 for no gears.

internal gear hubs (which =awesome), single speed, or fixie (next hipster trend? Deep v's and belt drive?)

There's a good chance that the pulley on the tire's axel could be a variable pulley that spins outwards the faster that it's spun, making the sides of the pulley push against the belt tighter, and hence you can go faster.

If that sounded like giberish, look at this.

Or internal hub gears, like old 3 speed bicycles. (They make them in up to 14 speeds.) I can't tell from the photo.

yeah, these are very popular in japan. most 'shopping bike" have them. I had a couple and they worked. I don't know why I never pulled one apart to see why. only three speed. but choi cool for hooning around throught the entertainment district at night. BMW had an uber cool central shaft bike back in the 1930's. I think it looks really "clean". chains and gears are aesthetically messy.

a belt is cheaper to manufacture than a chain

I think drive shaft's a better idea...


9 years ago

I checked out one of these at Interbike last week. They had a single speed set up to ride and one with an 8 speed internal hub. The 8 speed shifted like a dream. Sooooo smooth. These things require no lubrication, shed dirt and mud well, and just are mighty cool. It will be a while before i put one on my bike but i look forward to them coming down in price and up in popularity.

With the reduced weight, I wonder how long it will be until they start appearing in pro races.

I'm not sure they could handle those sorts of speeds, the teeth look to me as though they would slip and I think the diagonal flexibility could mean they would come off the gears easier.

I think in the 50's they used belts to drive the wheel of motorcycles but they found it was hard to change gear to go up hill so they had to engineer a complex transfer mechanism which slowed them down. I think.

"Harley Davidson went back to belt-drive several years ago. THey are definitely smoother and quieter. A lot of early motorcycles used belts (some of them even used the natural "slip" as a primitive clutch). I'm surprised bicycles haven't gone this direction earlier." -Skunkbait

It is distinctly possible that the sort of thing being put on bicycles would slip or otherwise fail. The belt in the photo looks decidedly unimpressive. Belt drives are a proven technology on today's motorcycles, as both primary and final drives. as Skunkbait pointed out.


9 years ago

I bet it could be done more cheaply than that by an enterprising hacker. The belt is presumably the difficult part because it has to stand up to pretty high tension, but I'm sure there are strong enough belts commercially available. The sprockets are probably nothing overly special, for weight reduction they are probably some kind of unobtainium alloy because at this point in the product's lifecycle it will do better by being expensive but uber-high-performance than cheap but average. The Reprap guys seem to know their belts fairly well...

Drive pulleys from various engines could probably be cobbled in to a workable system, maybe even timing belts reinforced, there's an 'ible making an insane electric scooter, the belts in it looked to stand up to the test pretty well, they might be good candidates maybe at 7mm or a bit larger, deep tooth of course.

My thought exactly, drive belts from a engine... or maybe even the beltdrive off of a motorbike.

I'd say cam belts or even AC belts might be enough, in comparison to an engine there's not much load on them, the nice thing is you could put together a good set of ratios...

Good point about the loads. Of course, if you have parts laying around, they automatically nominate themselves for the job. But I don't, so maybe I need to visit NAPA.

I saw down there someone has trouble with slipping, I'd say a tensioner is in order, either an idler that tensions or a simple mechanism similar to that on aa single speed. If I had the junk about I would already, I might try and find a way to use the old belt drives on the compressors, that way I could have a giant wheel in there as well, which seems silly but I could balance with no forward motion (They're a very powerful gyroscope...)

I am a big fan of the gyroscope concept. A large part of my (very literal) downfall with pedal bikes is that I tend to not get them up to speed before I need to put my foot down to avoid falling.

The other idea around this is that you could have a drag bike, ever been on one of the exercise bikes that uses a massive weighted wheel to resist motion, if you spin them up to full speed you can stand on one pedal and the momentum is enough to only pedal one side, if you resist the bugger you get bucked in to the air... I think a bicycle with a big heavy flywheel and clutch could be quite a lot of fun, you could drag race them, plus they'd look insane, monstrous wheels spinning while someone's sitting on top of it perfectly balanced. The only minor issue is that steering dynamics would be very different, the bike would naturally resist leaning in to turns.

I was at the seattle science center and i got a weighted wheel up to 173 mph.... for about 45 seconds... crazy amount of energy there... the chain started jumping teeth so i quit :P Looked like 10 lbs of rubber in about a 3/4 inch thick disk...

Cool! Do you remember roughly how the drive mechanism worked?

You know I think we could bodge one from old bicycle bits, I'd say use the car tyre idea from the crush all that stand before you bike as a drive tyre. Simply have a set of dérailleurs with an exceptionally tall set of gears, wind it up and see how it goes, for the wheel you could make a self balancing wheel by filling a car tyre with water and pressurizing the last bit with compressed air. Alternatively you could use any number of heavy wheels, I'm not sure if you'd get maximum inertia by using the heaviest wheel possible or by going for a larger diameter but lighter wheel, but big inertia is the key. The only problems after that are getting a usable clutch and drive system since the immediate torque and energy applied would be huge, if say you pedalled for a few minutes getting to speed applying for sake of argument a kilowatt or energy constantly then it would all be released in as little as a tenth or a second through the clutch and drive...

As for the clutch, I'm considering using an actual friction clutch, if I can bear to pull one off of one of my machines. That would be pretty sure to grip like a python, and keeps the price low! If the concept was proven, then things could be expanded. Failing that, perhaps a set of interlocking gears? I sense a lot of potential in the concept--shall we continue brainstorming in an unpublished collaboration, so we don't clutter up this thread with comments too much?

Sure PM me a little link... It seems like an interesting idea, I do imagine there are some other things to think about like weight transfer issues but that's for later...

I'm down with the collab idea. It's been a while since I worked on stuff of this type but did work on a goped mod with an engine swap and replacement clutch so am not completely clueless.

I'm also intrigued by the flywheel idea- did either of you see this? It's a physical regenerative braking system for a bicycle that stores energy in stretched elastic, and I don't see why the same principle couldn't be used with a flywheel.

that's interesting could be a possible project considering I have a ten foot bungee cord here, along with much stronger ones for a crazy slide followed by shooting off effect... I think I may have figured out where to get a flywheel...

I wonder if the steering would then become more like a motorcycle, where you push on the left grip to go left. I'm not really sure what auses that effect, but I assume its the gyroscopic force of the wheels. Perhaps I ought to get out the welder and try and build one of those clutch-based drag bikes. I've got enough spare bits.

I'm pretty sure that actually the gyroscopic effect on wheels isn't a major part of bike dynamics- IIRC there was an experiment done on a bike with a set of contra-rotating wheels to nullify the gyroscopic effect that was still totally rideable. It's the tiny corrections you make to the steering to keep the wheels underneath you coupled with the self-centering steering geometry (trail, etc) that makes bikes possible.

The reason for the counter-intuitive steering effect you mentioned is that pushing the left grip turns the wheel to the right, which makes the wheels move to the right underneath you, which results in you leaning to the left, and on a bike leaning = turning. Actually it's the same on a bicycle when you make sharp turns travelling fast- you'll notice yourself make a slight flick against the direction you want to turn to set up a lean before you turn into the corner.

Neato! I never did manage to figure out precisely why things behave that way. I'm just glad it works.

930-990 is actually low end in the biking community. Its definitely not cheap, but its not very expensive either. As for not being able to switch gears, I ride a dirt jumping bike and personally, i hate gears, and would pay MORE to not have them. My friend's downhill bike is single speed, why? simple, his derailleur blew up going down whistler when he landed off a jump. Lots of road bikers ride with 1 gear too, simply because there is less to brake (same reason as dirt jumpers)

If you notice, the belt and the bike frame are like two interlocking rings. That bike has a special removable rear dropout to make this happen. It doesn't seem easy to retrofit to an existing bike, so a cheap solution isn't likely in that direction.

Perhaps a segmented chain would help, such as http://www.leevalley.com/wood/page.aspx?c=1&p=30051&cat=1,240,41067

Belt drives, like shaft drives and auto-shift bikes, have been around for years. They've never been very popular and most bike shops won't touch 'em - partly because they're usually built by smaller companies that never last long (means you can never get replacement parts). I work in bike shop and we recently started offering belt drive bikes with 3 speed hubs for about $400. At this point it is possible to convert a normal chain drive to a belt drive for under $200 (using actual bike-specific parts). All that being said, belt drives may be a bit cleaner, quieter and lighter...BUT... the belt does skip teeth if you over torque it (it doesn't take much). There also aren't many options available for changing gear ratios (especially if you're running a single speed). Anyway... that's my 2 and 1/2 cents. oh yeah, about the bikes our shop sells...they skip so bad that the manufacturer is sending us chains and cogs to replace their belt system.

aren't belts bendy so wouldn't it snap easily