E-bike with electric transmission

[m7priest]

I guess you could say it's not strictly an electric bike... ^^;

I was just wondering if anyone had tried building one with an electric transmission?

Or, where might one find a suitable generator & motor? Since most small gas gens either do 120vAC or 12vDC.... Not a lot of amps there...

Thanks

[amberwolf]

What is your definition of an "electric transmission"? One that is shifted electrically? Or one that uses an elecromagnetic coupling and slip between the fields to create the power-transfer ratio?

[m7priest]

Uhm. Like...when you have an electric motor driven by a generator of some kind. Like the big diesel rail engines use. I just thought a small one might be a fun project...

[Philistine]

This question is asked with surprising regularity, eg:

http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=29978

Along with questions about perpetual motion (I am not being rude or sarcastic, I am serious, that is a surprisingly often raised topic).

The almost uniform answer is that you would be better off using the ice engine to directly power the bike rather than a generator. Apart from the physics of the whole thing, one of the main advantages of an electric bike is that a) it makes almost no noise, b) uses no fossil fuels (directly) and c) is stealthy. If you are going to ruin a) b) and c) with an ICE engine, why not just build an ICE bike (which if you are not getting the benefits of a) b) or c) are a superior form of power to electric.

[StudEbiker]

Well, you do get to keep the torque of the electric motor while increasing your range, but other than that, yeah, it's not such a great idea. Better to get a bigger battery and carry a charger.

[m7priest]

Oh, I know it's not very useful on this scale...but the advatages of an e-bike aren't really my goal. I just thought it might be a fun project to engineer...

[StudEbiker]

I agree that it is a cool concept. Here is a link that I think had one of the best ideas along those lines that I have seen. Unfortunately the image monster has eaten all the pics, but there is a link to his build on MB.com which still has the pictures.

viewtopic.php?f=6&t=6429

[Drunkskunk]

it could be done. Gas motor > generator > wheel motor. The efficancy loss is horrendous, so no one does it.

Trains do it because they need an infanatly variable transmission ratio between the engine and roadwheels. a mechanicle transmission to handle a trai's torque load would be extreamly complicated and prone to failure were electric coupling is much more simple and robust even with the efficancy losses.

[gogo]

In the above train reference the heavy weight of a big diesel motor and huge electric motors is highly desirable for traction on steel wheels. Weight on rubber tires is not as desirable.

[m7priest]

That's a very interesting thread. But the guy there noted that he didn't seem to be generating much power..which I think is the main problem... Even a 50cc ICE at WOT will only put out maybe 8 amps...?

Anyway, there's actually more to diesel trains than that...and I know it doesn't scale down/apply well...
I just thought it would be a fun project, not some revolution in ebikes or anything... ^^;