New bike build, hub gears & brakes, belt drive

For discussions about bikes and equipment.
bobc
Posts: 495
Joined: 5 Apr 2012, 11:59am

New bike build, hub gears & brakes, belt drive

Postby bobc » 3 Jan 2014, 6:44pm

Aiming for a zero maintenance commuter: so hub gears, brakes & dynamo and belt drive.
I got an 80s raliegh frame (ebay £20) and today I ordered the toothed belt. Its 14mm HTD industrial belt, a 1288mm x 40mm wide cut into 4 x 10mm widths, that comes out at ~£16 apeice
I've been given a suitable crank/spider, below is "chainring" design. I've gone for an "osymmetric" style ovaloid, somewhat less extremely oval than my last try...
Image
With a SA 8speed, 40/25 crank & wheel teeth, I should be cruising in 6th/7th.
I'll bung pictures on here as I go along & dxfs for the laser cut parts if anyone wants to copy...
The parts above will be made when I get the belt (for confirmation of dimensions)
I'll keep the brookos saddle off my old bike....... ;^)

Brucey
Posts: 36851
Joined: 4 Jan 2012, 6:25pm

Re: New bike build, hub gears & brakes, belt drive

Postby Brucey » 3 Jan 2014, 7:21pm

good luck with the build!

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

cycle tramp
Posts: 609
Joined: 5 Aug 2009, 7:22pm

Re: New bike build, hub gears & brakes, belt drive

Postby cycle tramp » 3 Jan 2014, 9:17pm

Looking forward to seeing those photos ~ i was much impressed by your last build... if there was any justice in the world, folks like you and Brucey would be paid to design bikes :)

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Vaya
Posts: 171
Joined: 14 Sep 2012, 3:46pm
Location: Midlothian

Re: New bike build, hub gears & brakes, belt drive

Postby Vaya » 3 Jan 2014, 10:33pm

Will be following with interest, good luck.

bobc
Posts: 495
Joined: 5 Apr 2012, 11:59am

Re: New bike build, hub gears & brakes, belt drive

Postby bobc » 6 Jan 2014, 10:39am

Chequebook out last night; bought 90mmbrake dyno hub from sjs (£60 from memory), 70mmbrake & 8speed hub from "oldtimerbike" (or something like that - £148.95), some aero/disc rims from evans cycles for £20 each and a versa 8spd sti shifter from planetx for £99. (my mate Rich already tried this combo with complete success, I helped him measure the pull & error c.f. requirement is around 0.2mm at each end of travel) Also the versa brake levers work nicely with the drum brakes).
Getting a back wheel off is a bit of a palaver (if I get a flat) but hopefully I will avoid that by using 28mm tyres - worked out that way on my last bike :)

Brucey
Posts: 36851
Joined: 4 Jan 2012, 6:25pm

Re: New bike build, hub gears & brakes, belt drive

Postby Brucey » 6 Jan 2014, 10:53am

interesting about the Versa shifters, that; if they have copied the shimano shift sequence perfectly then there will be one longer pull in there on the 4-5 shift for the alfine/nexus hub. By contrast the SA hubs with rotary shifting tend to have uniformly spaced cable pulls IIRC.

If that is the case you might be OK in the high hears and low gears but ~0.5mm out in gears 4 and 5. Hopefully this is not going to reduce the tolerance to cable setting unduly.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

bobc
Posts: 495
Joined: 5 Apr 2012, 11:59am

Re: New bike build, hub gears & brakes, belt drive

Postby bobc » 6 Jan 2014, 11:12am

I'll get Rich to dig out the notes we took when we measured his versa - thanks for the heads up Bruce - I must say I didn't mentallly note any "pull" anomolies when we were doing the measurements.
I've also got the same data for a shimano twistgrip somewhere, I'll see if I can find it tonight (I once tried to make sora sti shifters work on a nexus8 using a stepped pulley adapter - that did not work well.....)

OK here are the measurements I took 5 years ago (shimano twistgrip)...
6.65mm 1-2
4.88mm 2-3
5.4mm 3-4
5.85mm 4-5
5.05mm 5-6
5.3mm 6-7
5.6mm 7-8
Did this on my own so not too reliable (not enough arms/hands to hold everything) but 4-5 does look a bit big.

bobc
Posts: 495
Joined: 5 Apr 2012, 11:59am

Re: New bike build, hub gears & brakes, belt drive

Postby bobc » 7 Jan 2014, 9:42am

as promised, these graphs show the versa "pull" on the way up and down, a shimano shifter (2 actually, my old measurements are on there too) and the sturmey archer shifter.
Image

Brucey
Posts: 36851
Joined: 4 Jan 2012, 6:25pm

Re: New bike build, hub gears & brakes, belt drive

Postby Brucey » 7 Jan 2014, 9:56am

good work fella!

I like the second plot; for an overview, it tells you much, and tells you quickly.

Obviously a long 1-2 shift pull shouldn't worry you because once the cable is slack, it is slack and that is it.

I think you can see the long pull on the 4-5 shift with the Versa and the Nexus shifter. I would hope that it won't be a problem to you; I've not looked at the shift mechanism in an SA8 hub but in a SA7 hub each gear position had a small plateau to allow for slight misadjustment. [Mind you maybe they could afford to; that hub had about the most cable pull per shift that I've seen].

The shimano hubs have very little tolerance to bad adjustment; [it feels as if it will work OK on the workstand, but the hub will fail under load] plus the 1-2 shift may need to be a bit longer, so I wouldn't recommend using an SA shifter on a shimano hub, but the other way around looks to have promise; you should be no more than about 0.6mm out in any one gear and maybe the SA hub will cope with that.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

bobc
Posts: 495
Joined: 5 Apr 2012, 11:59am

Re: New bike build, hub gears & brakes, belt drive

Postby bobc » 10 Jan 2014, 8:02pm

OK- stuff been arriving during the week. Front dyno hub (with 90mm drum) is here (it's a bit of a monster) along with rims, versa shifter & a trelock ls882 light. Rich (who is using versa shifters on his sturmey 8 speed without any problems - still - about 100 miles now...) he's borrowed the trelock to see what it's like, having just broken his headlight. Having got the rims I was able to measure the ERD & order spokes, I guess they'll arrive at the weekend, then I'll start building wheels. The belt place have not got back to me, I'm starting to think I'll have to buy a fat belt & cut it down myself. Quite a few friends are interested in the transmission system, including Rich at work and my brother, so the wide belt won't go to waste! Anyway here is a drawing of the toothed belt pulleys, but I can't make them until I've checked belt tooth dimensions
Image
The IGH/drum brake for the back wheel will probably arrive end of next week, have to get the front wheel off the jig by then! I thought for a minute or two about fancy spoke lacing patterns, but I've got torques in both so I'm going conventional :)

alexnharvey
Posts: 912
Joined: 10 Jan 2014, 8:39am

Re: New bike build, hub gears & brakes, belt drive

Postby alexnharvey » 10 Jan 2014, 9:13pm

Is the second hole in each valley to allow dirt to clear?

bobc
Posts: 495
Joined: 5 Apr 2012, 11:59am

Re: New bike build, hub gears & brakes, belt drive

Postby bobc » 10 Jan 2014, 9:24pm

yep :)

Brucey
Posts: 36851
Joined: 4 Jan 2012, 6:25pm

Re: New bike build, hub gears & brakes, belt drive

Postby Brucey » 10 Jan 2014, 10:45pm

have you got a good belt-slicing method worked out? I guess there isn't much fabric to cut in that direction, but it looks like the kind of job that might make you sweat a bit. Maybe practicing on an old car cambelt is a good plan...?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

bobc
Posts: 495
Joined: 5 Apr 2012, 11:59am

Re: New bike build, hub gears & brakes, belt drive

Postby bobc » 10 Jan 2014, 11:04pm

Plan (which I sincerely hope won't be acted out) is to put the hub sprocket in the lathe & run it very slowly with a stanley knife in the toolpost......
what could possibly go wrong . . . .

Brucey
Posts: 36851
Joined: 4 Jan 2012, 6:25pm

Re: New bike build, hub gears & brakes, belt drive

Postby Brucey » 10 Jan 2014, 11:54pm

Oh dear Lord.... what indeed...?

One potential snagette is that Stanley knife blades usually have a three-angle grind on the edge; you can see this under a magnifying glass. This means that they usually don't cut perfectly straight.

I was wondering about one of those reciprocating cutters, and a jig of some kind, maybe the lathe like you say?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~