# Transmission on the conversion



## kek_63 (Apr 20, 2008)

The advantage would be that you could get away with a slightly smaller motor. But with a chain drive it is usually quite easy to get a 5:1 or 6:1 final drive.

The disadvantage is that the transmission adds weight and takes away battery space which is already at a premium on a bike. 

Unless you are building a 750lb+ cruiser with stock shaft or belt drive, I personally don't think you will realize any advantage with the tranny.

There are some bikes on the evalbum with existing tranny used. Check them out.

Later,
Keith


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## manic_monkey (Jun 24, 2008)

older bikes, and harleys often have what are called 'pre unit' engines. the gearbox and engines are seperate modules. you could get an old pre unit gearbox and do it that way. their normally pretty small and light if you look for small engined bikes, like old BSA and triumphs, etc. i wouldnt recomend using one designed for a harley though.


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## [email protected] (Jul 5, 2008)

All year models of Norton gearboxes are 4 speeds and weigh about 25 lbs. and are smaller than a harley tranny and about 1/2 the weight. I've been building British choppers for many years now and I can tell you the Norton box would be best but they are not cheap and rather hard to find not attached to their original bike. Triumphs and BSA's were "Pre-Unit" up to 1963 so finding and using a 45+ year old box might be out of the question. Another problem with running a gearbox/chain drive is the efficency loss through the driveline. I think ultimately the best setup would be a belt drive system like on current model Harleys directly attached to your drive motor with some sort of gear ratio although a OEM Harley system might be overkill. Harleys produce over 125HP and most EV cycles are not trying to set speed records. I think a good source for belt drive pulleys would be the Kart racing industry but the belt tooth pitch and size is different for Karts than Harleys so getting the right length belt might have to be sourced from Gates Rubber or Granger Supply.

Anyway I hope this helps you with the quest! later Travis


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## kasi124 (Jun 30, 2008)

Thanks for all your replies guys. Guess I will stick to the most preferred option of a direct chain drive. 

Thanks again


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## steven566 (Jul 11, 2008)

Hello everybody, I'm new to the site.

I have just started thinking about this in the last couple weeks after reading an electric bike article in Popular Mechanics. I thought of using a bike with an external gearbox (Harley) to keep the shifting aspect of a bike, which I find appealing. I also like the idea of a silent Harley.

I am now trying to find info on how to make one of these and just came across this site.

I'm a mechanical engineer and don't remember a whole lot about the electrical side of things, so I'm trying to refresh my memory on all of this stuff, so any help that you guys/gals could give would be excellent.

I hope to hear a lot more about your projects,

Steve
Gilbert, AZ


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## Little Rhody (Jun 17, 2008)

Steve, 
Welcome. Check your PM's..............

LR


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