Building off road ebike help needed

ray74

Pedelecer
Sep 2, 2013
118
16
Could someone tell me if these are any good and what's the difference between geared and gearless?
Electric Bicycle E-Bike Conversion Kit 48V 1000W Brushless Motor Rear Wheel Rack | eBay

I'm looking to built an off road e bike and would ideally like to get about 30mph with good power, I've got a cyclotricity kit fitted on my trek mountain bike that I use for my commute to work every day but now I want to have some fun off roading. Any help would be a massive help, also any recommendations would be appreciated too but I don't want to spend loads of money, I was thinking of spending about £600 on the kit with the battery.
 
D

Deleted member 4366

Guest
Gearless motors tend to be larger diameter and heavier for the same torque, and generally they're not so efficient at low speed. If you had a commute that involved travelling at a constant 30mph all the way, the gearless motor would be better, but if you have lots of stops and starts, hills, etc, a geared motor would be better. Gearless motors tend to be quieter.

Off-roading usually involves a lot of bumping of the back wheel, which is not good for the gears in a geared motor. Trails are OK, but rocky paths and jumps wouldn't be good for one. For good off-road controlability, you want light weight. 30mph requires a 40 amps, which normally means a heavy battery. You can do it with lipos if you don't want to go too far, but again, you need to be careful that your installation is very robust against bumping.

For 30mph off-road, you're going to need a serious down-hill bike with triple clamp forks and top of the range rear suspension. Think about more than £1000 for that. This sort of thing:
http://www.ebay.co.uk/itm/Commencal-DH-supreme-Downhill-Mountain-Bike-Medium-/290982759360?pt=UK_Bikes_GL&hash=item43bfec8bc0
 
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ray74

Pedelecer
Sep 2, 2013
118
16
Thanks for the reply, yeah I was going to get my last bike on the cycle to work but I could wait that long for all the approval to go through so my next project will be on the bike to work scheme and I know i will have to pay about £1000 for that.
I won't be actually using it for that kind of biking though, it will be more like cross country with a few bumps and jumps on the way. My main concern was finding out why kind of motor and battery I will need.

So I now know I will need about 40 amps and a 48v battery, and probably an absolute minimum of 10ah but 15ah preferred.

What kind of torque figures should I be looking for on the motor?
 
D

Deleted member 4366

Guest
Sorry, I wasn't thinking straight. 30 amps at 48v or 40 amps at 36v.

On any surface other than smooth tarmac, your suspension will be working very hard at 30 mph. A hard-tail would be good fun for a couple of hundred meters, but then you'd want to get off. Don't even think about a Tesco or Halfords bike with pogo-stick rear suspension. It'll probably chuck you off at the first bend.
 
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