Which Hub Motor?

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Geoff B
Posts: 4
Joined: Fri Jan 16, 2009 1:37 pm

Which Hub Motor?

Postby Geoff B » Wed Mar 04, 2009 10:44 am

Hi, I'm reposting this cos it seems to have disappeared while the site was down. Wasn't sure where to put it as there isn't a section for motors.

I'm designing a low-drag electric trike with a hub motor in each rear wheel. I'm looking for a cruising speed of about 75 km/h.

I used a performance curve off www.ebike.ca (thanks guys!) for a Crystalyte 5303 at 72V and have marked three scenarios for my proposed vehicle, IE: Max speed on level, a 1:20 hill and a 1:10 hill. These are based on (I hope) realistic calculations. Remember the vehicle has 2 motors. The motor characteristics seem to match my requirements well.

I am surprised by the amount of torque shown on the graph at low rpm - The maximum figure (zero rpm) is about 3.5 times the manufacturer's maximum quoted torque. Is this real or is it just Canadian optimism?! How long will the motor sustain this torque? I will need at least 36Nm per motor for climbing steep hills, so I need more than the rated torque for maybe 30 seconds to a minute.


I've been looking at Golden hub motors from China. The HBS-48 is similar in performance to the Crystalyte 5304, but lighter. It seems to be the motor FalconEV is selling ('Green Hornet'). Golden also seem to do an equivalent of the 5303 as they mention 900 rpm (presumably at 72V).

Does anyone have experience of these motors and/or importing them from China? I'd really like to use the motor built into a cast aluminium wheel but they only make these in 12" and 14" sizes (they say 16" and 18", in line with bicycle practice), but it's very difficult to get narrow tyres in these sizes in The West. Will I get away with 36 12swg spokes for MSVA??

I'm hoping a 2Kwh battery pack will give me a range of at least 50km - is this realistic?

I'd be really grateful for any advice!
Last edited by Geoff B on Wed Mar 04, 2009 11:57 pm, edited 1 time in total.

Geoff B
Posts: 4
Joined: Fri Jan 16, 2009 1:37 pm

Postby Geoff B » Wed Mar 04, 2009 3:20 pm

I've just read that 72V systems are quite dangerous and need special safety precautions. Is this something that the MSVA test will assess?

My other option would be to use a non-hub motor driving through a 90 degree reduction (8:1?) gearbox (so the motor sits longitudinal) on each wheel. A motor like this may be suitable:
http://www.robotmarketplace.com/product ... 8-150.html

Sorry - lots of questions!

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