Advice for a first timer

[David Summers]

I've got a specialised globe city commuter that I'd like to add a motor to. It has a nexus rear hub and a dynamo front hub. I live in a mildly hilly town, one or two short steep bits on a 6 mile each way commute. It looks to me like a front-hub motor kit might be a simple and practical way into electric biking, sacrificing the dynamo? Something like the Bafang SWX gets good reviews but will it be able to climb the hills as I'm not svelte and 6'2" (about 105kg)? I've read about it not liking running slowly, but I fear I'm in danger of reading too much on the internet! And as an aside, are these kits reasonably straightforward to fit?

Thanks for advice/help

 

[Deleted member 4366]

There's lots of different versions of those motors. The key characteristic is it's speed. You get them from 180 rpm up to about 300 rpm. If you get a 180 rpm one or even a 201 rpm one and run it at 48v, it'll climb very well. The 180 rpm one climbs pretty well at 36v, but then you only get 15 mph. At 48v, it'll do 19 mph.

All electric motors can burn out if you slow them down whilst feeding maximum power. It's not a problem to go slow if you use a lower power level. If you give the motor plenty of power, it doesn't need to go slow. it's a bit counter-intuitive, but you can make a motor safer (from burning) by giving it more power.

 

[David Summers]

I'm happy/keen to stay road legal - I'll be using it entirely on-road and I cannot afford to have any problem with my driving licence, which appears to be at least a theoretical risk if you exceed the legal limits.

So, does that mean a 250W, 36V 180rpm motor is the one? And can anyone vouch for a kit that would provide all this (for a first go I'd prefer it all to be compatible, and with some backup if my build attempt hits the buffers!). Donor bike is a Specialised Globe City with a nexus hub.

 

[Benjahmin]

Front hub is certainly the easiest to do and was my first conversion. I live in hilly west wales and have an Ezee, similar in size and torque to the BPM woosh offer. It has never been a problem on long climbs. I cimb mostly in setting 2/5 and go down the gears even, occaisionally, getting out of the saddle. That said I do try to keep at 8mph or above because the slower a motor goes, the less efficient it is, so the more heat it generates. This is why D8 said that applying a higher power setting can help protect a motor from burning, because you go faster.

So, does that mean a 250W, 36V 180rpm motor is the one?

Yeh sounds good, but I think I'd put it on a 48v battery, it'll give you more torque for the hills. So long as the controller is 48v capable a 36v motor will be fine.