Motor Id

[Garry Hallam]

Hopeing somebody here can identify this motor that I bought in error.

I have looked on google but cannot find out what size wheel it is designed for.

36v 250w
BFY1803B10015-1

Looks like about 153mm dropout

 

[saneagle]

It's a band brake motor, like those fitted to the Cyclamatic Power Plus and a load of similar bikes. The only thing that affects the wheel size is the speed, so stick the axle in a vice or frame and power it up to see how fast it spins. If it's too slow for whichever wheel size you want, you can run it at 48v. To get the speed, stick a magnet on it and use a cycle computer or use any controller with an LCD.

If you're lucky, it's 180 rpm, which gives you the most options.

 

[Garry Hallam]

Thanks for the info. I will do as you say and check the speed. It was advertised for 20" folder.

What speed would a 20" folder have?

 

[saneagle]

Thanks for the info. I will do as you say and check the speed. It was advertised for 20" folder.

What speed would a 20" folder have?

A motor for a 20" wheel should have a maximum rpm of about 328 rpm to get good power and efficiency at 15 mph. If it's too slow - say 260 rpm, you can run it at 48v to increase the speed by 30%. If it's a 180 rpm version or 201 rpm, it'll be too slow. It has 180 written on it, which is a bit worrying, though it might be just a coincidence.

Band brake motors are wider than disc or rim brake ones, so make sure that you try the motor in the frame with its brake before building the wheel.

 

[Garry Hallam]

I wondered if I should strip it down and modify it on my lathe to fit 135mm dropout

 

[saneagle]

I wondered if I should strip it down and modify it on my lathe to fit 135mm dropout

The band brake frames have the left side offset a bit to deal with the extra width. If you just leave off the bandbrake it might be narrow enough. frames for 20" wheels are stiffer that ones for larger wheels, so springing the drop-outs apart to fit a wider motor isn't as easy, but it depends on the design of the bike.

You could do something to reduce the width, but make sure that you don't end up with too much offset from the centre of the frame. Most rear hub-motors have about 6 or 7mm, which has to be compensated for by dishing the wheel when you build it. Any more offset than that results in too much difference in the spoke tension from side to side.