Cmanns, I think you should get a rear hub motor wheel, so the bike doesn't do funny stuff on loose surfaces or torque steer like you said. I'm sure you could drive the disc brake mount on a pie motor from a gas motor and it would work fine, and actually relieve some stress on your frame, dropouts especially. Front wheel drive is only cool if you've gotta drive to work in the snow, on bikes I can imagine it being borderline dangerous.
I'm not sure if I want to do it yet, fortunately its something I can add later if I remember to reserve space for batteries. If I hybrid the bike I'll use lead batteries because it would be experimental and I'm afraid of damaging a Li pack. With both drivetrains going together, the 7hp total would make up for the 20 or so pounds of extra crap on the bike. I kinda like a little weight if I'm not pedaling, because it helps the tires smoosh into the pavement better so I can lean.
The thing is, a this bike would make a superb pure electric, or pure two stroke, I'm not sure if it's worthwhile because I could probably get away with a noped if I ride carefully. On the other hand, it would create a shadow of a doubt about whether the moped is legal, and that's enough to avoid a ticket which could be quite big for riding a dirt bike in town without motorcycle reg.
My ankles are kinda messed up right now from sprains so while they heal I'd prefer to have to pedal a heavy MB if it craps. I'm not sure whether the electric motor would be powerful enough to go up a hill on its own, but I would think so if it has 3.5hp max, at low revs it must at least make 500w which is enough to move well without pedal power. Supposedly the moter I want to use runs cool already, and I'd be water cooling it as well with an electric circulation pump to a little radiator, so maybe it will be okay. The motor is supposed to simulate a supercharged v8 in a 1/8-1/5 scale speed boat or buggie, so I would imagine it has a decent amount of torque.
It's hard for me to justify allocating the money to it when I need to start a small business. I have a feeling it would be awesome too, so I wouldn't want to sell it. I need to sell my pure electric dirt bike and I'm having trouble doing it, because I keep modding until I fall in love. The hybrid or electric idea would be an attempt to make a better replacement for my modified Razor dirt bike so I don't miss it so much. There are a lot of trails that I have been able to get away with riding just because of the silent electric, and I don't really want to lose that.
I wish the swing arm hole was about 5mm larger because then I could fit a 7 hp electric motor in there. It's hard to ell whether a pure electric on this bike would be reliable or if I'd overload the motor that will fit in the bottom bracket hole. I guess I could mini jackshaft it somehow to a geared hub transmission.
The real problem is that the possibilities are really endless. It's hard to tell what components you're going to overload, and this bike is all new parts that aren't cheap. I'm pretty sure I want to use the cag on this bike, since I have a different motor planned for my next build. I was thinking about just using the motor for the other bike and going electric, but the charging time is a killer, so the only real solution is to charge while riding.
Of course charging while riding induces drag, but you can adjust how much drag there is by the load on the circuit, or the charging rate. The key to making a hybrid with onboard charging work right is power management, which gets complex. I think I can do it with analog circuits and a couple component boards. I don't really care if it doesn't charge up while riding, rather I expect it to just discharge slower as the starter/generator makes up somewhat for lost power. It would be like riding your pocket bike with the headlights on in terms of motor drag. When accelerating, the output of the small electric plus the cag would overpower the drag in the dynamo so that it would be a small fraction of the overall power.
Pocket bike guys take off the electric starters to get more revs and faster acceleration. While I can't really lighten the motor more since the rotating parts are copper wire and magnets, what's left is balancing. The reduction in redline from these must come from imbalance, so I'm sure some fiddling around with some vee blocks cold balance the motor with a drill or some solder. Not too worried about slower spool up of the motor, because the electric assist would shove the little reed 2stroke into its powerband faster, so it should in theory pull like a train.
The power management electronics would be another story completely, I have an idea of what might work but there is no guarantees with electric stuff, especially when you can't get a spec sheet or the intended purpose is different. I found a brushless regen controller for e-bikes, but the spec sheet they provided upon request looked like it was written by a six year old. None of it was useful info for designing a system. It's kinda frustrating because you have to make so many educated guesses with the components for stuff like this, and just hooking it up wrong can fry everything.
I guess the path this bike takes will depend on my want for a challenge when I get through some school stuff this month. I think about this too much and it distracts from important things, although alternative transportation is a career goal for me in engineering, so maybe its money and time well spent.
