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Tech => Home Brew => Topic started by: thepauly on June 07, 2015, 12:33:08 AM

Title: Two wheel drive
Post by: thepauly on June 07, 2015, 12:33:08 AM

Hi everyone. I've wondered if anyone has thought about a two-wheel drive ev, using hub motors. From my completely noob perspective, it seems like a decent idea. You would get regenerative braking from the front, where most of the braking power comes from, you could use two small motors, instead of one, which would reduce the unsprung weight in the back. It seems like packaging would be easier.

OTOH, would it need two controllers? Is a single hub motor all that heavy (compared to a drum brake, which my bike has)? Is regenerative braking even worth the complexity?

I'm considering an ev conversion for a 1971 yamaha, so I'm spitballing here. If it's stupid idea, I won't take offense. I just haven't seen any and I know I'm not the first to think of it.

Title: Re: Two wheel drive
Post by: firepower on June 07, 2015, 06:32:30 AM

http://www.customevperformance.com/p/8777383/catavolt-s6-electric-motorcycle.html (http://www.customevperformance.com/p/8777383/catavolt-s6-electric-motorcycle.html)

This bike uses 20kW or 40kW hub motors. size seems ok. Hubs free up more room for batteries and have higher instant torque i read.


Only issue maybe fitting two front disk to the hub, but one may be enough with regen.

Title: Re: Two wheel drive
Post by: ctrlburn on June 07, 2015, 06:41:07 AM

It is a good idea - just been done.

I like this one a "utility moped" has an optional front hub motor.
http://www.gizmag.com/hero-motocorp-turbo-diesel-hybrid-electric-2wd-motorcycle/30768/ (http://www.gizmag.com/hero-motocorp-turbo-diesel-hybrid-electric-2wd-motorcycle/30768/)


The military always get one better.
http://foxtrotalpha.jalopnik.com/u-s-commandos-to-get-this-stealthly-hybrid-all-wheel-d-1568589260 (http://foxtrotalpha.jalopnik.com/u-s-commandos-to-get-this-stealthly-hybrid-all-wheel-d-1568589260)

Title: Re: Two wheel drive
Post by: thepauly on June 07, 2015, 08:31:21 AM

Thanks for the replies. I had seen the DARPA bike before, but I'm thinking it's driven by the Christini system, which is definitely beyond scope and budget for me.

I should have been more clear with my original post. Has anyone built a conversion with two hub motors?

The brake issue is valid, but the bike has drum brakes now, so I don't imagine a single disk brake would be a step down.

Title: Re: Two wheel drive
Post by: Doug S on June 07, 2015, 08:02:30 PM

You wouldn't be decreasing unsprung weight in the rear, you'd be increasing it quite a bit both front and rear. Wheel weight is by definition unsprung; the motor on our bikes is chassis-mounted and therefore sprung. At the very least it would make for a bumpy ride and probably beat the hell out of the motors.

Title: Re: Two wheel drive
Post by: thepauly on June 08, 2015, 12:45:34 AM

When I mentioned reducing unsprung weight, I was referring to the idea of using two smaller motors, front and rear, vs using one big hub motor in the rear alone, to get the same power (rear 5kw and front 5 kw, versus a single 10kw in the rear [numbers used for reference only, this is not a design specification]). Obviously, adding hub motors to the wheels increases unsprung weight.