Belt drive bikes

[Kennah]

This is a way cool concept. Belt driven bicycles.

http://en.wikipedia.org/wiki/Belt-driven_bicycle

Actually are a couple of companies making them now. They aren't entry level bikes, but they aren't completely ridiculous prices either. Norco Ceres is $1375. Trek Soho Deluxe is $1260. Trek District is $1150.

http://en.wikipedia.org/wiki/Belt-driven_bicycle#Manufacturers

Couple of articles in the news about new belt drive bikes, like the $3600 Spot Rocker SS.

http://road.cc/content/news/38652-first-ride-milk-bikes-bullet
http://singletrack.competitor.com/2011/06/29er/tested-spot-rocker-ss_17228
http://www.wired.com/gadgetlab/2011/06/practical-looking-concept-electric-bike-actually-exists/

[happyslug]

1. Two BIG problems with the use of belts

First is belts are NOT adjustable, i.e. must be made for a set distance between the front peddles and the rear drive (With a stationary machines an adjustment of the machine can permit the use of just one belt, but the adjustment is on the machine NOT the belt and most bikes can NOT do that type of adjustment).

You may NOT be even able to go to a different tire size, for that would increase the distance between those two points and make the belt to tight (or if you go to a smaller tire to lose. i.e. a Biker could NOT go from a 26x1.5 tire to a 25x 2.0 tire on most bikes for the change in tire size would also change the distance between the peddles and the read drive, I suspect such a change would still be possible but you will have restrictions much more then with chains, for with chains, the chain can be adjusted by adding or removing links from the chain).

Furthermore, the belt would be for a set frame, one chain could NOT be used for a set of frames, for example a 18 inch frame would have one belt, the 20 inch frame, do to its different length between the Peddles and the Drive, would have a non-interchangeable belt, the same with a 22, 24 and 26 inch frame. Metric sizes would be as different and NOT unchangeable (Through you may see some interchangeability between very close metric sizes). Thus instead of one Chain for all the frames a bike maker sells, the bike seller will have to have at least a dozen belts for each bike frame SIZE.

With Chains, one Chain can fit any bike with the same chain size (i.e. 5 speed, 6 speed, 7 speed, 8 speed, 9 speed and 10 Speed rear hubs). Thus a 18 inch bike frame can use the same chain as a 24 inch bike frame, the difference can be made up by removing or adding chain links. Thus if you are making bikes, you only need one chain if you stay with all nine speed bikes, no matter how many different size frames of that bike model you make or carry.

The Second problem is that chains can be disconnected but belts can NOT be. In the days of High Tension Steel bikes (Most bikes prior to the 1980s) would NOT have been much of a problem, but with the increase use of stiffer materials for bike frames this is a concern. The Stiffer the material, the less energy is lost to the frame itself and more the the drive train, Chrome Moly, Aluminum, Titanium, Magnesium and Carbon Fiber frames are all STIFFER then High Tension Steel and thus much easier to peddle, something like 70% of peddle activity can be absorbed by a High Tension Steel Frame.

With Chains, you can "break" the chain in two and keep the bike frame intact. With Belts you can NOT "Break" the belt, you must have a way to open the frame so the belt can be attached. Any break will make the bike less stiff and thus hard to peddle. Most of this loss of Stiffness will not be observed by most people, but it will exist and when operating with similar bikes except for the belt drive and the break in the frame, the cyclists will notice the difference, even if it is minor (And racers will notice it big time, and thus will NOT put it on their Racing Bikes).

The other problems with the Belts are minor, most people do not bike in heavy snow (And a
"Chain Guard" would prevent most the problems reported with belt driven bikes and snow. A third major problem is most chains, within a set chain size, 5 speed, 6 speed, 7 speed, 8 speed, 9 speed and 10 speed) can be interchanged between most makers of those chain size group. You can NOT put a 10 speed chain on a 9 Speed system, but you can put various makers 9 speed chain on whatever 9 speed bike you have (Some limitations exists, but are minor compared to the huge variation of possible Belt drive systems).

Belt drive like the shaft driven bicycle discussed in this forum in 2008, good concept but the lack of flexibility compared to chains, keep Chains #1 on bicycles.

The Thread on Shaft Driven Bicycles:
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=324x1870

[Kennah]

2. Belts aren't a panacea, at least not yet

I'm not following you on why a belt drive would not permit one to change the tire size. The belt is dependent upon the crank to axle distance, among other things, and that doesn't change when one changes tire sizes.

It's my understanding that there is a tensioner on belt drive bikes, although I don't know whether a tension could say allow for enough adjustment that one belt could be used across a range of frame sizes.

It's true that chain has fewer variants. Either 3/32" (for multi-speeds) or 1/8" (for single-speeds and fixies). There's also narrower .090" chain, although 10 or more sprockets at the rear boggles the mind. However, I know from perusing Sheldon Brown's website, and Harris Cyclery, chains still aren't quite that simple. SRAM and different diameter rivets. That all said, I agree if belts were the norm it would impact the supply chain, pardon the pun, because a greater selection would need to be on hand at bike shops--unless bicyclists started carrying a spare belt which would seem to defeat the benefits of the belt.

Unless radically different bike frames appeared, yeah, a split frame is necessary for a belt drive system. From what I've seen of belt drives, most of the bikes are either urban or commuter bikes with a fair number of mountain bikes. A few folders and tandems. Also a few road, touring, and cyclocross bikes.

I'm not a frame builder, don't pretend to be, and I don't pretend to understand all the pros and cons. But a lot of people who appear to have no financial angle, or stock in Tompkins (Gates parent company), are saying good things about belt drives and I'm finding a lot of people having good experience with them.

Belts on cruiser motorcycles are common while chains are still seen on plenty of racer style motorcycles and probably every imaginable venue of motorcycle racing. However, most motorcyclists won't and don't ever use the full potential of their racers. Similarly most bicyclists don't use the potential of their bikes, which explains why so many big box store bikes continue to be sold, and landfilled.

Bicycling appears to be very much on the rise, but I suspect there are far more utilitarian bicyclists than racers. I could easily see belt drive becoming the norm on utilitarian bikes, but I'm sure the chain will never die so long as there are racers and big box store bikes. Low quality, semi adjustable, caliper brakes on big box store bikes will ensure the rim brake never dies.

[frylock]

3. i would think that the sliding drop outs and/or an eccentric bb would allow for different gearing..

i change the rear cog on my 29er quite a bit depending on where i'm riding, and adjusting the chain is fairly simple with the sliding drops.

[Kolesar]

4. Belt drive is clean, but in some gears there are great energy losses

I get the impression that it is 6% less efficient than a derailleur. I would pass.

However, if the hub is designed for direct drive in the gear you use most, then the "efficiency problem" is less.

http://hubstripping.wordpress.com/internal-gear-hub-review/

Steve P
August 24, 2008 at 1:28 am
...

Some other things to consider: some of the hubs are very heavy (the i-motion 9 is particularly notable) and there are hidden advantages in others that may suit different riding styles: for instance the SA 8 Speed has direct drive on 1st gear – so if you’re planning on a lot of hills, this may suit you best. However, for most people, the Shimano nexus-8 hub has direct drive on 5th gear, which if you choose your sprockets carefully should mean that you get no power loss from gearing in normal riding on the flat.

Also it would be interesting to list claimed efficiencies – the SA 5-speed has a terrible reputation for power loss in 1st gear.