road bike with belt drive and internal geared hub

[bobc]

I recently built myself a bike & thought I'd share some gumf about it. I'm a fan of the internal geared hubs so I used a shimano alfine 11 speed. And to be different I thought I'd make it with a gates belt drive.
I made my own pulleys for the belt from laser cut lamination stacks. This actually held costs down a bit (the laminations cost me £40 in total) though the belt itself was very expensive (£76).
Here's a picture of the bike when it was nearly done.

I've put 150 miles on it in the last 2 weeks and the bike is better than I could have hoped. The IGH with versa drop 'sti' shifter works well and the belt drive delivers a magic carpet ride. The bike is SILENT in a way that's new to me (all you hear is the front tyre on the road) on other bikes I can always hear the chain/deraillieur. And it feels more efficient than my previous alfine 8 IGH bike (i.e. I pull a higher gear everywhere & average a higher speed).
If anyone wants to do something similar, all the design information is on endless sphere -
http://endless-sphere.com/forums/viewto ... &start=165
Using a laminate stack for the pulleys means you can get the belt line perfect with very little effort.

[Brucey]

very interesting....

any more details of frame used, seatstay break, chainring, belt tension etc?

Some of the latest bicycle belts have a central groove and use ridged pulleys to locate the belt. Is this what you did?

Also I'm interested to know what the quality of the fit of the sprocket pieces was onto the hub; it is possible that this fit will deteriorate over time in use with a belt drive.

cheers

[bobc]

Hi Bruce
frame was £80 ebay fixie frame + £60 carbon forks (from cannondale).
Seatstay break was put in by me with a hacksaw & I tigged an ally piece to one side with c/sunk M8 for bolting together.
Belt tension is controlled by my own laser cut stainless non-turn washers cum tensioner thingies.
I used the older gates belt (no central groove) as it's more suited to the stacked laminated pulley idea (an original idea by schlumpf)
The hub sprocket is all stainless and the quality from the laser cutters is just excellent - so the fit is pretty much perfect on the hub & seems excellent on the belt. Gates' original alfine drive sprocket was ally and known to chew off the drive "nobbles"; I expect no such problems with the stainless.
The chainring was made the same way by me, but I used aluminium (I still used stainlesss for the flange).
After 150 miles the belt still looks new (still shiny on its teeth).
Apart from the frame welding, no specialist equipment was used at any stage - it all just fit together as planned. The sprocket laminations were made at the laser cutting place on the industrial estate where I work, I tok them the designs in dxf format on a memory stick & 4 days later picked up the finished parts for £40. The link above includes the dxf files and a belt length XL spreadsheet + later in the thread design details on tooth shape assuming anyone else would want a different tooth count to me.
Regarding the belt line: there are a couple of mm potential side to side adjusment possibilities at the hub (before clashing with the hub or the frame). At the other end the chainring is VERY close to the chainstay but it does (just) fit perfect on a frame I just bought off ebay.

[Brucey]

well I think you have made a nice job of that! Doubtless others would choose differently for things such as gearing, wheel build etc, but the belt drive looks really good.

Which method do you use for setting the belt tension?

cheers

[TonyR]

Nice conversion. I was interested in getting a bike like that and looked at Milk Bikes but it was clearly a part time kitchen operation so I passed and got a Genesis Day-One instead. The only bad news I have for you is it is also magic carpet silent apart from the tyre noise using just a conventional chain drive.

[bobc]

belt tension - too much & you damage the hub, too little & you run the risk of belt skipping: I'm afraid I just set it so it feels right to me, there is about 1cm flex in the middle of the belt & it's not really "pinging" tight. Others have reportedpossible belt skipping under load & thats why the right side tensioner on the photo at the top has the long part hanging down - it's so I can put a "snubber wheel" on there if necessary to ensure proper tooth penetration. So far it looks as though this will never be necessary (I'm running bigger than standard cogs anyway to reduce stress on the belt components).
Obviously you can't use a belt with a derailleur so it's fixie or IGH - so it was interesting to do the IGH build. The alfine 11 has been perfect so far (I read reports of problems with early models, "springiness" in 1st/2nd and skipping under load in 6th and 11th) but I must say mine has been spot on. There is a lot of b****t around about the efficiencies of various transmission options - I believe that this bike is probably 3 to 5% less efficient than a derailleur bike that's in perfect nick. But my efficiency will stay the same for years with no maintenance or lubrication, and will not get me filthy whenever I touch it. SHould suit me pretty well! The alfine 11 hub has > 400% gearing spread with even 13.9% steps - again this suits me pretty good: I've geared it so development goes from just over 2.5m to 10.5m in top.
I guess you're alluding to the 1 cross lacing on the wheel - that's the fruit of years of hard won experience ;^) 3cross on a big hub like this leads to spoke breakage at the stress raiser at the end of the thread - I broke spokes for a couple of years working that out (I'm a heavy guy & the roads round here, as everywhere, are not in good nick). A further advantage is that you can use the much cheaper spokes sets sold for 26" MTB wheels by chainreaction. SHimano say use 3 cross but what do they know.... ;^) 1 cross on a big hub give the same "torque angle" between spoke & rim as 3 cross on a small diameter hub.
Tony - yeah fair enough - my last bike had vertical dropouts so I had to put a chain tensioner on it & I could always hear that, like I can always hear a derailleur, but anything "alternatively tensioned" should be pretty quiet! The alfine hub does not have conventional freewheels so it is silent (until you back pedal....)

[Brucey]

that is all really interesting.... that means you have a 131" top gear which is more than large enough, a lot of people would have geared a bit lower than that. I hear what you say about the spoke x-ings. I think some people try and tread a happy medium by going 2x.

One way of setting the belt tension is to use a spring balance or a dead weight to deflect the belt and then measure the deflection.

Do keep us posted on how it all works out as time goes on.

cheers

[meic]

Very impressive.

If fitted to a frame that could take mudguards and geared down to 25-100".
Then fitted with dynamo lights and you have an ultimate commuting bike that lacks those faults that we normally put up with on cycles. It could compare to a car for maintenance free utility, I hope.

[graymee]

As an engineer I'm impressed. I'm unlikely to build anything similar myself but am jealous of the facilities you have access to. The laser cutter you mentioned, is this something you have in your workplace? The satisfaction of building something like that must be great.

[simonineaston]

Prap's just as well you can't see me as you would be alarmed at the colour I've turned, looking at your pix, but to give you a clue, it rhymes with 'spleen'
I have a Pashley TSR frame-set lined up for just this gear train - the one with the split rear triangle, natch...

[TonyR]

Prap's just as well you can't see me as you would be alarmed at the colour I've turned, looking at your pix, but to give you a clue, it rhymes with 'spleen' .

Would that be tangerine or aquamarine?

[bobc]

Graymee, the only "special skill" needed for the build was the tig welding on the frame. I honestly think anyone could do the rest - the laser cutting place is an ordinary commercial enterprise who I've used quite a bit for making sprockets for other jobs, but I'm just a guy off the street to them. I had to be able to create a dxf drawing, but most of the mechanical CAD packages on a PC can do that.
Making your own pulleys compared with buying a set off gates:
pro - you can have any no. of teeth/ratio you want
+ the lamination stack system allows convenient adjustment of the belt line (vitally important to get right)
+ cost
con - not guaranteed (though mine's been OK for 150 miles.... and looks good to carry on...)
Actually the 1 & 2 pros above are key to a successful application - you can only get certain belt sizes (mine is a 122 tooth) and a 24 tooth pulley for the alfine over the counter.
Simon - I hope yours works as well as this one, you can probably tell I'm extremely satisfied with how it turned out - it's not usual for a project like this to deliver everything it promises, especially when there's quite a bit of untried and/or unusual componentry. But I can say now without hesitation "try making one like this.... it works!"

[Brucey]

just out interest what frame material, filler rod etc did you use?

cheers

[Ribblehead]

Nice looking project. Congratulations on getting it all designed and put together.

Can anyone explain why the tooth shape on the sprocket isn't a simple 'U' shape like the belt teeth?

Edit: One other thing. Seeing as you made the whole thing yourself, why not just buy a suitable automotive cam-belt (which is probably nearer £20 than £76) and design the sprockets to suit the tooth design on the cam-belt?

[Brucey]

Can anyone explain why the tooth shape on the sprocket isn't a simple 'U' shape like the belt teeth?

Edit: One other thing. Seeing as you made the whole thing yourself, why not just buy a suitable automotive cam-belt (which is probably nearer £20 than £76) and design the sprockets to suit the tooth design on the cam-belt?

shoot me down in flames... but I think the tooth shape is to help clear dirt etc from the teeth. Some chainrings for MTBs are made the same way.

I have wondered about cambelts too.... but they are generally a bit wider... maybe they can be cut down the middle..? (two for the price of one... ) BTW both main tooth profile shapes (sort of square and sort of round) are used on various cars.

cheers