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[jamin_mathis]

Hay all new to the forum first post in fact well anyhow I've been meaning to do a ground up motorcycle build for a bit now and I figured why not an E-bike. I race a type of motorcycle racing that I think would be perfectly suited to E-bikes it's called Endurocross think of it as a cross between moto trials and supercross. in this the laps are fairly short in distance and the mains for my class (amateur) about 5 laps so we are not asking much in terms of range. The speeds top out at about 20-25 mph and thats only for very short burst. I think the e-bike would a good choice for this kind of racing for the following.

No clutch although this could down side as we use clutch ups to get the front wheel over things
No stalling!!!!!
Both breaks on the bars!
Low end torque a must!

My plain is to get a doner 125mx bike take the front end, swing arm and wheels and put those on a custom made frame I would build.

I have a mill, lathe, mig and accese to many other tool as well as some friends who have built bike frames before so I hope I got that covered but what I don't know anything about is the electrics so If there are some books, links or pitfalls I should be aware of please let me know about them.

My spec goals are sub 200 LBS
A 30 mph top speed
enough torque to loft the front wheel at 15 mph
A 2 mile top performance range

Let me know if these goals are realistic and if you have any advice component wise.

If you would like to check it out here are some links to a video of my friends riding the track I practice at.


and some photos





this one is of me


Thanks

[Bogan]

Interesting plan!

Not too sure about how well it will pop the front up, I'm assuming you want overkill on this, as long slow lift wheelie power wouldn't be too good for the sharp bumps. Although a good pull on the bars might overcome this it would get very tiring.

30mph is nice and slow, so slow you might have to run a reduction gear before the final drive chain.

Hope you have access to an AC Tig, a steel framed job would be a struggle to get under 200lbs.

My gut feeling is that its doable, and would be very fun to ride! Only having short burst at full torque will mean you can really push the limits of the motor/controller/batteries. But there's only one way to find out :p

[jamin_mathis]

Thanks for the reply Bogan you make a good point about the wheelies the more I think about it the more I think I will need a clutch maybe I could take the bottom end of a 2stroke motor and machine the crank case to accept the e motor where the crank would go and remove all the gears but the one that works best and lock it in that gear.... That would add at least 20 lbs but it would be the easiest way I can think of to add a clutch.

I could get my hands on a TIG but their are a a lot of challenges to building a frame out of aluminum and the frames often make contact with rocks and the ground it seems that the materiel that most of the big bike makers are using is chromoly.

Thanks again for the help.

[Bogan]

If you want a clutch, just get a dry clutch out of an NSR or Duc or something, and use that. Put a timing belt on the back and use it as a layshaft and primary gear reduction. Simple assembly with rubber seal bearings, and plastic covers. You'd want to make sure the electric motor rotor has a similar inertia to a crankshaft and flywheel though, if it isn't enough the clutch will be pointless.

Yeh I've built a subframe out of ali that had some cracking problems, due to unblanced design. Chromoly is probably a good compromise.

[jamin_mathis]

If I got a 125 2 stroke mx bike I'd already have the parts so no need to go out and buy more stuff also I'd have to fabricate a clutch actuator. I'm not afraid to rebuild a trans it wouldn't be my first time. As for the fly wheel I might be able to compensate for that with riding technique, you know slip the clutch rev it up to it's meager 3500 rpm and hope the WFOT will torque it up the rest of the way... I don't know I never rode an electric motorcycle before but if it doesn't work one could be added later.

I could also make a shaft that could run through where the crank was and mount the e-motor where the stator goes. I could add a flywheel weights to the shaft later on if their was insufficient inertia.

I also didn't think about the lack of an engines gyroscopic effect at slow speeds. Could make it harder picking through the rock gardens...

Thanks Bogan for giving me some things to think about.