Gates Carbon Drive Conversion on 3 Speed IGH
 

The Gates Carbon Drive is undeniably less "messy" than a chain on a folding bike, however it is also my understanding that it reduces the gear ratio differences on a bike and that this would be most noticeable on a bike with only a few gears. There are relatively few folding bikes that come standard with the Gates Carbon Drive system, but conversion kits are available. I have seen comments made in prior threads about the reduction of pedaling efficiency of a bike with this system due to its effects on gear ratios.

Has anyone successfully done such a conversion on a 3 speed IGH bike such as a Dahon Curve D3? I'd imagine that the 16" wheel size of this specific bike might even make things worse. I can see where this could be a very cool conversion to do, making disassembly and folding much less messy, but on the other hand if it takes a bike that is already somewhat challenged on the gear ratio side to begin with, making it something almost unusable anywhere that is not totally flat, then there would be no point in using this system on that sort of bike.

You need to have a bike that it will work on. Bike Friday had to design a completely new back for their bike to use it. You can't for example have a bike with seat atays and chain stays. That will limit your frame choices some. The belts are one piece and can't be cut/broken like a chain can. It looks like it should work on the Dahon you mentioned and if you have the same chain ring to rear sprocket ratio it will not change anything. Good luck with it. Roger

IIRC,there was a Mu Uno posted awhile back that had been converted to a belt drive. Curve shouldn't be a problem. The issue with gearing is there are only so many belts and pulleys made,and you can't customize the belt length like you can a chain. The Ixi bikes have belt drives,Nexus 4's and 16" wheels;I checked their site but couldn't find any info on the gear range.

I suppose the rear fork , rather than rear triangle makes it possible..
BB shell and rear hub have to form a single unit, [ not up on D'Hons]

and the belt tensioned with much more pull than a chain uses.

any bike that has a hinge behind the BB won't work, well.

Already a unified rear portion
the Bike Friday Tikit jumped on the belt thing as soon as they came out.
they just added a stay split to get the belt through..
their customers wanted the more than 3 speed hubs , though..
not much more, considering the outlay..

the new Silk redesigned and put the BB on the front of a rear fork assembly..

A 3 spd hub with off-the-shelf Gates Carbon Drive bits wouldn't work well on a Curve with 16" 305 wheels .. really the only logical sprocket and cog set available through Gates for a 3 spline hub is 60/24 (and that's assuming you could get the proper length belt) .. and that gives a 2.5 to 1 ratio.. plug that into a gear calculator and you'll see it will be seriously under-geared.. like 11 mph in top gear at a cadence of 80 rpm .. I wouldn't spend much time dreaming of that conversion..

Put a Schlumpf Speed drive crank on the front, and Get it with one of His Belt cogwheels , and that
as posted above 60t will act like a 96t in its overdrive range.

its like putting a Porsche engine in a VW bus......
http://www.youtube.com/watch?v=SsaBYyjhHuo

:-)

If I could ride a bike like that guy drives the VW bus . . . . . . . .

Im about as aerodynamic as the front of a VW transporter.. with the same old motor.. :50:

The gear ratio differences of a three-speed IGH are in the gears inside the hub and unaffected by the transfer mechanism from the crank to the cog. If the hub gives ratios of 3/4, 1:1 and 4/3 with a chain, it will give 3/4, 1:1 and 4/3 ratios with a belt.

Isn't it partly due to the fact that the rear sprocket has to be above a certain size (belt wrapping round it) thus restricting the use of small cogs ?

PS my TSR2 has belt drive with a 25T rear and 67T Main (it does not look like a 67T though ?) which gives me 51 - 70" on the S2C. I find the gearing a little low for riding on the flat/down hill once I exceed 16-17 mph. Whilst changing the gearing on a conventional drive is as simple as changing the rear sprocket/main ring, on the belt drive things get more complicated.

Jerry

True, tcs, but [my Brompton] putting a 54t crankset and a 13t on the AW3,
puts the range those 3 gears operate in , up significantly..

when I kick down my Mountain drive to a 21t equivalent, and the % remain the same
but the range is lower.

No offense,but these really aren't a good idea for most of the folks you suggest them to. The Curve is like a $600-700 bike,that Schlumf drive is $600+,that's doubling the cost of the bike. And I'm sorry,but those things don't seem to be all that great to me. First,you get a HUGE jump in the two gear ranges,not always a good thing. Second,the shifting means you have to take a foot off the pedal. Not always a good idea,and a pain if you're running toe clips or clipless pedals.

To the OP:if you really want to do the conversion,I'd say measure a Curve and then contact Ixi to see how close they are in size. If they're comparable,Ixi's pop up on eBay from time to time for cheap,you could just buy one and swap the parts to the Curve. If it doesn't work,put the parts back,sell the Ixi,and you prolly won't be out much. If it does work,put the Curve parts on the Ixi and sell it,a recoup most of your cost.

The Ixi doesn't use Gates Carbon Drive components (14mm pitch ) that the OP was asking about .. it uses Cdrive components (8mm pitch) .. Gates moved away from 8mm pitch belts/cogs/sprockets for bicycle application some time ago favoring the more robust 14mm standard ... the Ixi 8mm pitch 80/26/1200 works out to a little under 15" axle to crank (center to center) .. so if the Curve has that chainstay measurement (of a little less than 15") and Ixi is willing to sell a kit, or a primo Ixi comes up for sale, it could be an alternative to a Gates Carbon Drive system... you can't buy Cdrive components over the counter (choosing to sell OEM only).. another bike that runs Cdrive components is the Moulton TSR-2 .. I'm running mine daily with a SRAM P5 5 speed IGH installed without issues ..

In Practice, no ... the foot stays on the pedal, I just tap the protruding center button with my heel.

In fact if I added the EZ shift plate that is held on by the pedal I dont even have to aim that accurately.
A lever, it covers the whole outside face of the crank arm..

Only takes a half second to do the double shift on the MD between 3rd and 4th..

Yea the Swiss dont work as cheap as the Chinese have to, and since every exploiter and despot in the world
has a numbered Swiss Bank account ,the CHF are not devalued. So the exchange rate is unfavorable with the Dollar .

cant help that, .. As you were, hermanos,,

The Curve D3 was probably not a great subject to propose such a conversion on. At the moment, out of my too large stable of folding bikes, I do think that this one is the one I'm going to take to France for a my upcoming 3 week trip. It rides surprisingly well, and as Thor pointed out in another thread, it disassembles pretty quickly and easily for packing in an airline legal suitcase. The Big Apple tires make the ride pretty comfortable. In my state of mediocre physical conditioning at the moment, I'm still able to ride it up to the top of a moderate hill without dismounting. I probably won't be riding it 30 miles in a day, but 20 miles seems quite doable, and 30 if I don't mind spending a lot of time in the saddle, so to speak.

Nothwithstanding any of this, a Gates Carbon Drive conversion on this bike seems probably to be not worth the effort . . . . plus the chain comes off completely when the rear wheel is taken off, so it can be put in a plastic bag, minimizing the mess and reducing the rationale for such a conversion in the first place.

Hi,

http://www.thinkbiologic.com/product...ve-chain-cover

http://www.thinkbiologic.com/sites/d..._FreeDrive.jpg

Might be an option, it will keep your chain (and you) cleaner.

http://www.bikeforums.net/archive/in.../t-691110.html

rgds, sreten.