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File: IMAG0358.jpg (1MB, 2688x1520px) Image search: [iqdb] [SauceNao] [Google]
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I want to add a weed whacker engine to my bike, saw the above photo and wondered what the diy community thought of attaching a pulley directly to the spokes in a similar fashion to how that sprocket is attached. Please ignore my double post, my fingers are too fat for this phone
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>>907347
I didn't think you could OP without text, are you a wizard?

Meanwhile, why belts? Unless you're planning to put the engine on a pivot so it can be tensioned onto and off the pulley to disengage drive, chain drive using the snippers centrifugal clutch should be good enough.
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>>907347
You can do that. Just be aware of the torque of your engine or it'll rip the spokes out of their place or bend them at least.

The way it's attached in your picture is usually done with weak engines, that are more like helper in wind, uphill or work as slow sustainer when you're already at speed. If your engine can skid the bicycle from standstill, under your whole weight, the drive-train should be quite robust.
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>>907350
What? Those are from chinese motor kits. They'll drive the wheel from a stop. The only problem is that it bends the spokes. I have one now that I'm building, and had one in the past. I had to have a custom thicker wheel built after it broke the spokes.
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>>907349
That was exactly the plan, I want to keep the pedals as they are, and figured the pivot would allow to add tension without the need for a clutch. Plus I figure I won't have to be as precise with a pulley, where a chain would just fall off if the chain isn't damn near straight. >>907350
I haven't tested the engine yet, I'm in the process of getting it running, I figured a little 30cc engine would be enough to help me but wasn't sure it would ruin The spokes or not
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>>907376
Belts do have more left to right play, and would be safer, but I'm not convinced it wouldn't just spin on the pulley, if it doesn't have teeth.

Anyhow, as someone who is building a motorized bike ATM, I would really recommend finding a way to drive the wheel from the axle. It's just so much better that way. It may still twist the spokes, so I'd find a solid wheel or heavy spoke wheel. Personally, I'd like to buy those plastic adult tricycle wheels and do a custom shaft setup, with plenty of extra for a gear or pulley, and just do away with the pedals. But it sounds like you want only an assist.
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File: dtvshredder_003h23.jpg (146KB, 736x669px) Image search: [iqdb] [SauceNao] [Google]
dtvshredder_003h23.jpg
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>>907347
>attaching a pulley directly to the spokes in a similar fashion to how that sprocket is attached.
the part that OP's pic shows (the rubber thing that bolts into the spokes) is called a "rag joint"

the China kits that use these rag joints have problems with spokes breaking because they place a lot of stress near the head-end of the spoke. You can't SEE the spokes are broken, the rear wheel just suddenly doesn't feel "solid" anymore. The spokes break where they aren't visible.

other types of motorized bikes do use a pulley attached to the spokes, but it is usually a larger-diameter, so it attaches somewhere near the center of the spokes. That way the stress is better distributed and broken spokes is much less of a problem. These large pullies are usually called "sheaves".

the classic way (like, 50 years ago) that you would build a motorized bicycle is you would cut the sheave off of a front-loading clothes dryer drum and use that bolted to the spokes of the rear wheel.

the vintage Whizzer motorized bicycles used a sheave that screwed to the spokes.
the current Golden Eagle kits use a HDPE sheave that just snaps on to the spokes.

I have (what remains) of a Golden Eagle kit; the plastic sheave works just fine once you get it centered well.
I don't have the whole motorized bike anymore, for space reasons I got rid of it. I only kept the key parts (engine, sheave, wheels) in case I wanted to build another one again.
In the past, Golden Eagle would not sell their sheaves separately. You had to buy a full kit to get one. I dunno if that's still true. With a good sized 3D printer you could make your own now.
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How about using a disc brake hub? You could relatively easily make a mount for the drive sprocket instead of the disc.
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omg why the fuck would you mount it to the spokes
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>>907538
omg why the fuck wouldnt* you mount it to the spokes (ftfy)

>>907386
I really want to turn my bike into a tiny motorcycle, but I like the idea of it still having pedals. I'm toying around with the idea of adding the pulley onto the front sprocket though
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>>907467
Way more helpful than I ever expected 4chan to be. I'm going to see what I can find around that I could turn into a sheave if I can't figure anything else out
Thread posts: 12
Thread images: 2


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