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Hubs, Gearboxes, Sprockets and Chains Can't find 'em, grind em - hubs and transmissions, problems and modifications to make you run smooth and trouble free

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  #1  
Old 05-06-2011, 08:16 PM
gobigkahuna gobigkahuna is offline
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Default DIY alternatives to the sprocket rag joint?

I'm looking to convert a bike with 48 spoke wheels so the standard 9 bolt rag joint won't work. the hubs are coaster brake styled, but I plan on disabling the coaster brake and using caliper brakes instead. Any DIY solutions that mechanically connect the sprocket to the hub without buy an expensive adapter or new hub?
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Old 05-06-2011, 09:04 PM
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Default Re: DIY alternatives to the sprocket rag joint?

Check with Sportscarpet, he makes adapter with a 3.75 centerline, I have the same bike as you, I made a template out of paper, 3 point on that same circle, 120 deg apart, the hub on the Oynx is 1.519",within .004 of a CB110 hub, with my initial measurements and template, looks like his will work. I didn't order it yet($$) but a 50tooth sprocket will make up for the extra rollout of the 29" tire,{same as a 44with a 2 stroke} (if you have the 5:1 hoot gearbox),If you have a different gearbox, like a 3:1,let me know, I'll let you know the right sprocket size to keep the motor in the right RPM range. Mine has the 5:1gearbox and a 10to 44T final and its too tall, over 50 on a long downhill, bout 22 on level ground
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  #3  
Old 05-07-2011, 04:22 AM
gobigkahuna gobigkahuna is offline
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Default Re: DIY alternatives to the sprocket rag joint?

@Mac - Do you have a link to Sportscarpet handy? I googled it and couldn't find it.

Edit: Never mind, found it here: http://motorbicycling.com/f23/sprock...pat-26938.html The only price I've found was $80 for the CB110 with a 40t sprocket. I wonder what it would cost for our hub + a 56t sprocket (I'm more interested in hill climbing power than speed).

So you're sure the 120degree mount spacing will clear the spokes? What about chain clearance? I've read that can be an issue with these. I plan on removing the coaster brake on mine and adding front and rear calipers.

The other direction I was thinking about was a diy jackshaft. I haven't seen too many attempts at it, but am only just starting my homework on the topic.

Last edited by gobigkahuna; 05-07-2011 at 05:39 AM.
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Old 05-08-2011, 12:02 AM
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DuctTapedGoat DuctTapedGoat is offline
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Default Re: DIY alternatives to the sprocket rag joint?

Pirate cycles sells the clamshell adapters. HybriPed might work too. Myself, I've been on disc hubs, mounting the sprocket to the rotor mount, and I love it.
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Old 05-08-2011, 02:54 AM
gobigkahuna gobigkahuna is offline
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Default Re: DIY alternatives to the sprocket rag joint?

The min inside diameter for the Sportscarpat / Pirate cycles adapter is 1.522" while the hub diameter is 1.519", that's a 0.003" difference which isn't much but enough to keep it from working I'm guessing. I suppose a shim could be used, but it would have to be -real- thin, eh? I've sent an email to Sportcarpat but haven't received a reply yet. Failing that my alternatives look like they will be to either force the rag joint to work or get / build a jackshaft.
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Old 05-08-2011, 03:02 AM
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Default Re: DIY alternatives to the sprocket rag joint?

Well, you can always recut a larger circular hole in the center of the sprocket.
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Old 05-08-2011, 03:34 AM
gobigkahuna gobigkahuna is offline
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Default Re: DIY alternatives to the sprocket rag joint?

Quote:
Originally Posted by DuctTapedGoat View Post
Well, you can always recut a larger circular hole in the center of the sprocket.
Not sure how that would help. The sprocket adapter mounts to the body of the hub. My hub is 0.003" smaller than the sprocket adapter is designed for, so the adapter would likely slip. How would enlarging the center hole of the sprocket help?

I did look at the HybriPed site and I'm pretty sure that won't work, the holes for the mount looks like it's specifically designed for a 36 spoke wheel. It did give me an idea though, if I can locate a 50-56 tooth sprocket without the 9 bolt hole pattern, then I can drill my own holes. I'd have to make my own backing plate (do-able) and rubber rag backing (not sure if that's do-able) though. The other thing I noticed about the HybriPed is that it uses a lot more bolts to secure the joint. Looks considerably more secure than the standard 9 bolt pattern.
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Old 05-08-2011, 03:42 AM
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Default Re: DIY alternatives to the sprocket rag joint?

Oh, sorry. I was thinking you couldn't fit the hole over the flange.

For true DIY you could drill through the flange and sprocket, tap it and bolt your sprocket to the hub.

Though - you really don't need the plates from the rag joint. You could easily drill out a different hole pattern and make your own custom rag to fit, using washers to replace the plates.
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  #9  
Old 05-08-2011, 03:46 AM
gobigkahuna gobigkahuna is offline
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Default Re: DIY alternatives to the sprocket rag joint?

Quote:
For true DIY you could drill through the flange and sprocket, tap it and bolt your sprocket to the hub.
Yeah, I saw a build where he did that. I like that idea, but I don't think the hub has enough room for me to do that. I'll have to check it though.

Quote:
Though - you really don't need the plates from the rag joint. You could easily drill out a different hole pattern and make your own custom rag to fit, using washers to replace the plates.
Do you happen to know what the rag material is and where I can get some? I've not seen one in "real-life" but I'm guessing it's some sort of reinforced rubber (like sidewalls material on a auto tire)?
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  #10  
Old 05-08-2011, 03:56 AM
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Default Re: DIY alternatives to the sprocket rag joint?

Gotta be sure you don't hit the bearings of course, it's tough to say without seeing. If it's an oversized flange with a small hub, you might be able to.

I was talking with a friend a while back about using old conveyor belt material. Tire material I think would work if you could get a good large solid piece of it.
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