Child's bike, front wheel drive, built from scraps

[N8!]

Motor is from a razor scooter, the battery is temporary till I put a better basket, "throttle" consists of pressing the positive wire to the handlebars to complete the circuit, if it gets hot the duty cycle has been reached and the rider will let go. Drive sprockets are 11:80, I could make it re-gen by taping a stick to the tall sprocket but that complicates the design

I took the rear wheel from a similar bike and the tall sprocket from the scooter and used a lathe to turned both to pressfit into the bore of the 80 tooth with spot welds to hold it together and it came within 1.5mm of square/flat/correct. A small amount of hammer time persuaded it to be even better. I notched the fork and welded in some material from another bicycle to pass the small chain through, structurally is not great but the rider is light and will outgrow this frame in 2 years.

The nice thing about the simplicity is when one wire came off the battery a pair of 1st graders were able to diagnose and repair the problem, they accidentally learned a little bit about electric motors in the process.

simple, dangerous, fun.

 

[slaphappygamer]

So rad! No controller. Not sure if this can be any more simple. I see the positive lead, is the negative ran to the frame?

It is GREAT that the kids were able to resolve the issue on the bike. Some of those kids will never forget that moment. Maybe one of them will have their own build thread here in 15 years.

 

[N8!]

I see the positive lead, is the negative ran to the frame?

the negative goes directly from battery to motor, positive is attached to the frame. I've found that the negative gets hot faster, since there's no fuse the rider's thumb acts as a heat activated switch.

My 1st ebike was this style with a lawnmower starter and heavy lead battery in a beach cruiser basket in the 1990s.

as for the controller-less design, my grandfather built my mother an electric cart with the same simplicity in the 1950s with a 6v Dodge generator as motor/brake, all or nothing throttle.

 

[Chalo]

Running the motor current through headset ball bearings seems very hokey, but at this power level I suppose it works well enough. Any arcing will deteriorate the electrical path, but also wreck the headset. If I wanted to do this kind of thing, I'd consider soldering a jumper wire between fork and frame, or between handlebar and frame.

The wire getting hot is almost certainly from contact resistance at the handlebar.

 

[Papa]

I'd strongly encourage an enclosed chain guard..... for those inquisitive little fingers.

 

[N8!]

wreck the headset.

this has a single use disposable headset... almost as bad as the pedals, maybe worse.... . walmart demands cost reduction.

This would be a terrible idea on a long life bike.... however this is a walmart huffy, it will likely be eaten by sea-air corrosion in 2 years.