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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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  #11  
Old 05-08-2011, 04:03 AM
gobigkahuna gobigkahuna is offline
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Default Re: DIY alternatives to the sprocket rag joint?

Quote:
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 don't have the bike at the moment (waiting for a replacement bike that should be here this week) but if I recall correctly, it's a big hub'ed coaster brake style and the flange was pretty small. With 48 spokes it looked pretty tight. When the new bike comes in I'll give it another look.

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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.
I'll check McMaster Carr, they carry everything.
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  #12  
Old 05-08-2011, 05:23 AM
gobigkahuna gobigkahuna is offline
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Default Re: DIY alternatives to the sprocket rag joint?

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Originally Posted by Mac View Post
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
I just checked at McMaster Carr and they carry shim material in .001 / .002 / .003" thickness, so that might be one solution. I'm waiting to hear back from Sportscarpat, but I'm hoping this might work.

Another solution, albeit a lot more work, is shown here: Rear Hub Sprocket Mount - MotoredBikes.com: Motorized Bicycle Forum (My appologies for the cross link to a different forum, but it's relevant to my question.)
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  #13  
Old 01-07-2017, 08:50 AM
docimastic docimastic is offline
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Default SOLVED: mount 9 hole sprocket rag joint on 48 spoke wheel

I KNOW this is an old thread, so please don't yell at me for adding to it. Maybe I should have made a new post?
Just built a Genesis GX7 ("29er" 48 spoke wheels) motorized bicycle using the rag joint with 9 hole sprocket. The trick is to use only 6 of the holes. Two bolts in adjacent holes, skip a hole, two more, skip a hole, and then two more. Lay the wheel flat and try a few different positions. It CAN be positioned so the bolts drop right through the spaces between the spokes with the sprocket perfectly centered.
One other thing... the "1/3 moon" plates will bend, unless a second set is added. I happened to have on hand both the "1/3" plates and the older style "1/2 moon" - 4 holes in one plate, 5 in the other - and used those in conjunction with the 3 hole plates. Not having tried it, but it seems that it should be fine if all the 3 hole type... if the second set is staggered in relation to the first.
Hope this helps someone!
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  #14  
Old 01-09-2017, 08:10 AM
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cannonball2 cannonball2 is offline
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Default Re: DIY alternatives to the sprocket rag joint?

The rag joint has improved a bit over the years, The early ones had thinner backing plates compared to the ones I'm getting now. Also the sprockets with the slotted holes seem to align better maybe having a bit of float to line up. They must have changed the sprockets center hole also. I haven't had to grind a center hole to fit a coaster in a long while. The instructions call for no plates against the sprocket now.

I find retightening the joint several times a few days after installing seats them really well. All in all I can now live with them on all but a bigger HP/hi torque build.

BTW if you are building a cross over RH drive the common CG sprocket will bolt directly to an 18t coaster and centers well on the sprockets boss.

Last edited by cannonball2; 01-09-2017 at 08:19 AM.
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  #15  
Old 01-10-2017, 10:15 AM
docimastic docimastic is offline
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Default Re: DIY alternatives to the sprocket rag joint?

Thanks for your thoughts, cannonball2. I am a newbie to motorized bicycles - although I am now doing my 6th kit installation, so I can't comment meaningfully on the apparent changes you talk of. I have only built one with a coaster brake; didn't have to grind open the sprocket center hole, but did have to trim the outer circumference of the dust cover, and bend the brake arm.

Getting the sprocket installed and concentric with little lateral run-out always takes me more time (at least it seems) than installing the rest of the kit! I DID order a sprocket with slotted holes and will see if that does in fact allow more or easier adjustment to getit concentric with the axle/ hub.

One problem I've run into is that the rubber pads often vary in thickness....on each pad (not one compared to the other - that is not an issue) even though it appears they run them through a machine that is supposed to grind them to make each uniform in thickness around its circumference.

My biggest question regarding installing the rag joint bolts and nuts is how tight is tight enough? How tight is too tight? Plus it seems that to reduce wobble, some have to be looser than I'd like, and some tighter than I'd like. Have never used a torque wrench....

Any thought on proper torque on the rag joint bolts?

Thanks......

David
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  #16  
Old 01-10-2017, 11:18 AM
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cannonball2 cannonball2 is offline
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Default Re: DIY alternatives to the sprocket rag joint?

I just swapped sprockets on my current build and went from a dished to a flat sprocket. I had added plates under the dished to align it. On the flat I had to remove them. This caused the inner rag to have to be pulled in closer as the sprocket bottomed on the wheel hub a bit early. I just kept tightening until it all pulled together and ran true(or very very close). I tighten until all bottoms no set torque. You just have to work with it to get it true, like spoking a wheel.

You have to be careful not to load the spokes excessively laterally(bending toward the sprocket) however I never leave any gap between the rags. Its the firm bottoming of the rags into the spokes that handles the drive loading. Too little and it will spin and remove spokes for you! I also would advise tightening a few times over a day or two after installation, and checking on regular intervals as maintenance.

Properly done the old rag joints not to bad.
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