Vespa Bravo conversion--Newbie questions

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vespanewb
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Vespa Bravo conversion--Newbie questions

Hey, all--thanks for a great forum.

I just acquired an engine-less '78 Vespa Bravo and am brain-storming an electric conversion.

Knowing next to nothing about electric systems, I'll try not to bog down the forum with questions I can research myself, but I do have one that I think some of you could answer quite easily:

For those familiar with this moped, I'm considering converting it to a hard-tail so I can mount the motor behind the seat on the frame above the rear wheel. Those hub motors are cool, but I'm going cheap--this is a for fun learning project--and this way I can leave the rear brake intact. This also opens up room for large cheap batteries underneath my feet where the original engine was. I'm a carpenter/fabricator and can handle the structural stuff myself, but I'm going to have to do a lot of research when it comes to the control and drive system.

Anyway, this moped came with a gear reduction unit attached to the rear hub. It already has a pulley on it, and a round thingy (was that the clutch, or a flywheel or what?) that I think will go away leaving lots of room for pulley options. My question is whether I should use the gear reduction.

By my calculations, I would need to input 5500 rpm at this gear box to achieve 30 mph at the wheel, which is my goal. I have been told that with most of the popular motors, little to no reduction would be needed (?) but I am wondering if by using this 11:1 reduction I might open up some compelling motor options. For instance, by having this reduction, would I be able to go lower voltage? (I'd like to go cheap on the batteries!) Would I be able to use a cheaper motor, or would the reduction allow me to get greater acceleration with less wear and tear on my motor?

I have read that a safe estimate in moped conversion world is that 1000 watts will get you (barely) 30mph, so this is my rough plan so far.

So what's the verdict? Use the reduction, or not, and why, please. I truly appreciate any input.

vespanewb
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Last seen: 12 years 3 months ago
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Re: Vespa Bravo conversion--Newbie questions

Heh--so I have this question posted on 3 different forums and no answer, yet. I've been fumbling around the internet looking at motors, but I'm not really sure of the language I should use to narrow my search. For instance, what do you call a motor that is designed to run at variable speeds with a rheostat or whatever? I know next to nothing about electric motors, but I know that some motors are designed for a constant rpm, and running them lower will burn them out, right?

I'm getting the impression that having an 11:1 reduction on a 5500 (6000?) rpm motor would result in wheelies. This could actually be pretty cool. Maybe in the process of converting the rear-end to hard-tail I'll shift the rear wheel back a few inches so I can keep the front end on the ground. It does have Pirelli tires on it, so I got that going for me. ;)
A lot of the motors I'm looking at are categorized by h.p. rating, and I'm not sure how to translate that to wattage--I'm looking for about 1000 watts or maybe a bit more, I guess. 1 1/2 h.p.? maybe 2?

It's frustrating being a newb.

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