# '78 Vespa Bravo conversion: Use old gear reduction unit?



## Vespa Newbie (Mar 6, 2010)

Hi y'all. I'm considering an electric conversion for a engine-less Vespa Bravo I just acquired. 
I'm in the very initial brainstorming stage, so I haven't chosen a motor but this is just for fun and I want to go cheap. (So no hub motor--that way I can use the old brakes)
Anyway, the original drive line included a gear reduction at the rear hub which I believe is 13:1. This appears to still function. I am wondering whether I should/could utilize this. 
I am thinking that I may convert it to a hard-tail, which would allow me to mount the motor above the rear wheel behind the seat, and leave room for batteries under the frame down low where the original engine was.
So I'm just wondering what others may have done. I know I can achieve just about any motor-to-drive wheel ratio with pulleys, but I don't want to end up with a big ugly pulley on the drive wheel if I can instead use this sexy little gear box that I already have.
Any input is greatly appreciated!!


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## Vespa Newbie (Mar 6, 2010)

Alright, so I did some calculations and found that if I use the stock reduction unit, I would need 5500 rpm input to this gearbox to achieve 30 mph.

I had someone tell me that with the motor I'll probably be using, I won't need much if any reduction, but I still wonder if using this gearbox would open up some desirable options in terms of engines/voltage/battery choices.

Any input? Thanks


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## sunworksco (Sep 8, 2008)

You should see speeds higher than that.


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## Vespa Newbie (Mar 6, 2010)

Sunworksco: You say I should see higher speeds--I assume you mean higher miles per hour than 30, and not higher rpms on the motors I'm sourcing...but I wonder what you base this on? I haven't decided on a wattage, yet.

I've read that 1000 watts on a moped can loosely translate to 30mph, which seems to be a common goal, so this is my preliminary plan, but am definitely looking for input from those with experience. 

I say I'm keeping it relatively cheap, and that probably means lead acid batteries. I'm seeing motors around $100, but would spend $200, maybe, if it meant much better performance. Controllers and other miscellanea don't seem outrageously expensive.

I'd like a range of 20 miles, I guess, more would be better or a little less if I run out of room for batteries.

I want to use enough reduction or a powerful enough motor that I have good acceleration and hill climbing ability. I weigh 140 lbs. which helps. 

So, with that said, do you still think I'll end up faster than 30?


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