Quick welding question

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
I have run into somethings that don't want to take to welding. So before I ruin a rear sprocket on a wheel can anyone tell me if a standard chain ring will accept a welding bead. I want to tray welding one to a coaster bike sprocket.

why you ask? I think that if I had a larger rear sprocket I could increase the efficiency of an electric friction drive, why would i think that you ask.

Because when the bike bleeds off speed on a hill it has to get very slow for my current pedal ratio to catch up. In other words it free wheels until the pedestrians can pass me. I think if I could pedal assist sooner and even longer if I want, it will help. I know I could just get a mountain bike to put the drive on, and I would for anyone else, but for me I want to keep the 20" wheel on the rear.
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
237
63
up north now
I can offer that I welded the crank to the front sprocket (chain ring) on my Next bike and it hasn't broken since....grind off the chrome as best as you can first.
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
im going to give it a try when it warms up just a bit. I think worst I can do is ruin another wheel. A 20" wheel is easy to find kids bikes all over the place.

Since the jungle scout bike actually was a twenty inch kids bike with a front fork change out, I might also go shoes route as well.
 

2door

Moderator
Staff member
Sep 15, 2008
16,336
150
63
Littleton, Colorado
Deac,
Your biggest problem is controlling the heat. Don't try to run a bead all the way around the sprocket/hub area. Spot weld it giving a few seconds between the beads for cooling. This will help prevent warpage of the sprocket and hub. I'd start with a spot then move 180 degrees to the opposite side then 90 degress then another 90 degrees and so forth until you have evenly spaced spot welds incompassing the sprocket/hub.
That's how I'd do it anyway...
Tom
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
Thanks 2door but I already warped it. Live and learn. It actually would have worked I think but now I'm just going to pick up a cheap mountain bike to use once i have the drive built and tested.

But like most of my mistakes I learn something and I hope some of the others who read this do as well. If you weld one of these you need to use lots of clamps to keep it flat. And like the man said small welds