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PaulWay
31 July 2013, 1825
Hi all,

Rather than hijacking Chris's thread, I thought I'd start my own on this idea:

I've been thinking for a while about a motor more optimised for fitting into a motorbike: a long, thin motor with many, many axial coils. This packs a lot of motor into something that can sit longitudinally along the bike, as low down as practical. Then use a gearbox to gear down onto a shaft located right on, or as close as practical to, the pivot point of the rear suspension. Transfer the drive to the wheel by either a shaft drive or chain or belt drive. Smaller motors spin fast, so the gearing down also translates motor speed into shaft torque.

The main downsides I can see are cooling, requiring a higher switching speed, and making sure all the coils are aligned correctly so they don't fight eachother.

Thoughts?

Have fun,

Paul

jonescg
02 August 2013, 0333
The Colossus is about as small a diameter as you would want to go. I'd say axial flux motors need to be about 200 mm diameter to put out respectable torque. Don't know of any much smaller than this.

If a fully bespoke frame was in order, then you could build it around any motor you choose. But if you were sticking with the design criteria of a litre sports bike then a very compact motor is needed.

I think Axial flux, 250 mm diameter, and about 200 mm long would be spot on.

Mike Edwards
03 August 2013, 0316
Yasa 400 is your answer. If it doesn't fit in your frame then you have your priorities wrong.

A bespoke frame with the Yasa motor is more than you will ever need from a motor.

ARC EV Racing
03 August 2013, 0654
Yasa 400 is your answer. If it doesn't fit in your frame then you have your priorities wrong.

A bespoke frame with the Yasa motor is more than you will ever need from a motor.

Yep, just like the Kingston boys did with their bike. That's a nice build with some clever motor placement.

Sent from my AZ210A using Tapatalk 2

jonescg
03 August 2013, 1950
How did the Kingston guys go in the TT-Zero? We never heard anything from them for a while eh?

Nuts & Volts
03 August 2013, 2036
How did the Kingston guys go in the TT-Zero? We never heard anything from them for a while eh?

Don't want to side track the thread too much...they did well right behind our team :D I never got a chance to asked them about how their machine was doing (not sure I would have gotten much information either way). But it sounded like they may have been experiencing issues with either too little battery energy or close to the power limits of the cells (only thing I know is their large format from Korea -my guess is Kokam). Could have been other issues just didn't hear anything about them.

PaulWay
04 August 2013, 1810
Yasa 400 is your answer. If it doesn't fit in your frame then you have your priorities wrong.

A bespoke frame with the Yasa motor is more than you will ever need from a motor.

Funnily enough that's exactly what I'd planned for a race bike. It's just that pesky problem of getting a team together, getting sponsorship and getting it built that's holding us back :)

OTOH, I would argue that the Yasa 400, while it's a great motor, is not everyone's answer. It's not going to work for people that want a hub motor - for example, me. It's overkill for someone that wants simple, round town performance. It may simply not fit into smaller frames. For modest budgets it may be too expensive. There may be people who don't want or can't find the space for the water cooling requirements of a larger motor. The voltage and controller requirements of a Yasa may be too costly or too difficult for some people to work with.

And who knows, some people may want more power than a Yasa can deliver :D

Now, buying a electric motor that's more powerful than you absolutely need is actually OK - the extra weight of a Yasa 400 compared to a Colossus, and the loss of efficiency, is marginal. It really comes down to the space requirements and the battery setup.

So I do think there's a market for a small-diameter, longitudinally mounted motor in motorbikes. It'll just depend on whether an actual motor company thinks there's a market there too :)

Have fun,

Paul