Building an Electric Bike, Advice Needed

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Last seen: 12 years 3 months ago
Joined: Sunday, February 11, 2007 - 15:22
Points: 6
Building an Electric Bike, Advice Needed


I am determined to build an electric bike for this summer and am looking for some designs. Not only do I want this bike to be electric powered but I'd also like it to serve as a fully functional bike. What I mean by this is that I'd like pure pedaling, pure motor, motor+pedaling, and pure coasting. Without going to high tech, the best way I came up with doing this would be too have an internally geared hub with two bmx freewheeling sprockets on it. I will be using an aluminum mountain bike frame and plan on doing frame mods to accommodate the batteries. My friend has a mig welder and can do all the welding for me. I plan on stretching the bike and am wondering whether I should stretch the rear or front triangle. I was also wondering where to mount the motor. Above the rear wheel is avoids hitting it with your legs but looks pretty ugly imo. I may just get a right angle transfer case. ebikes.jpg

I haven't been into ev's lately but 2 years ago I years ago I modded my bladez scooter. A fabricated a motor mount for an eGo motor and planned to run it at 36v. Well on her first test run **** blew up. I've heard alot about eGo motors being duds and I think mine was just that. Sucked a ton of current with a very little load and blew my 36v 80a/120a controller. That's when I gave up on ev's

Well since then I decided to put on the oem bladez motor too see what it could do. I hooked up a 24v 24ah to 48v 12ah system with 2 relays. I wanted to see whether this motor goes or blows and sure enough it goes just fine. about 25mph with awesome acceleration.

So I will be using this bladez motor (900 watts @ 48v) for my bike unless anyone here knows how to fix an eGo motor (1500watts).

Anybody have any pictures designs that may help me out? The austinev album seems to be down. Even though this will be stretched I still think I can make it look clean. I have a lot of sheet aluminum to cover up all of the ugly stuff.
Also will the original voltage forum ever be back?


chas_stevenson's picture
Last seen: 11 years 6 months ago
Joined: Wednesday, December 6, 2006 - 17:14
Points: 1309
Re: Building an Electric Bike, Advice Needed

I like your idea of stretching the bike to fit the batteries and of course give you some room for the motor but I think you could stack the batteries so you would not have to stretch it so far. Something like this:

Also to make the bike so you can ride it in all modes you could place a freewheel on the motor and use the Vision, Independent Peddeling System used on tandems. This would allow the motor to freewheel when you just pedal, the pedals to freewheel when you just use the motor, and you could use both together.

Good riding,
Chas S.

Last seen: 12 years 3 months ago
Joined: Sunday, February 11, 2007 - 15:22
Points: 6
Re: Building an Electric Bike, Advice Needed

There's definably alot of designs to play with to accommodate the batteries and motor. I will be using a 48v system and would like to keep the center weight of gravity as low as possible.ebikes1.jpg

A sprocket on the motor would be ideal but those are very hard to come across. I would have to have one customly made for the shaft of my motor and If i were to upgrade motors it would be obsolete. Another good system would be to use a disk brake hub, and mount the motor driven sprocket on that side. However I don't know if anybody even manufactures opposite drive freewheels. Internal hubs are very clean looking and would work a lot better then a derailer system with a powerful motor. BMX freewheels are available in all bike shops but unfortunately they don't come in sizes bigger than 24teeth, so some kind of reduction is needed for the motor. I thought about a jackshaft but then was lucky to find a nice internal reduction clutch assembly off my friends seized pocket bike. I'm not limited to this design I just think it's reliable, low cost, clean looking ,gearable, efficient and safe.

lol, the designs are endless


Fechter's picture
Last seen: 14 years 2 months ago
Joined: Friday, November 17, 2006 - 07:01
Points: 199
Re: Building an Electric Bike, Advice Needed

Some kind of jack shaft might be the least expensive way to go. You need quite a bit of reduction between the motor and the wheel, and if you want to pedal it at the same time, it's nice to use the same rear sprocket. I've heard of bicycle hubs that are threaded on both sides, so it might be possible to put two freewheels on a hub and use it for the jackshaft.

reikiman's picture
Last seen: 4 months 22 hours ago
Joined: Sunday, November 19, 2006 - 17:52
Points: 8447
Re: Building an Electric Bike, Advice Needed

Staton Inc carries some wheels and hubs that have threading on both sides of the wheel, plus they carry freewheeling sprockets. This means you could mount a regular deurailer cassette on one side of the rear wheel, and connect a motor to a sprocket on the other side of the rear wheel.

As for battery location .. I find it's best for the batteries to be low and centralized. I think either location you suggested is good. My mind just flashed on an idea, so long as you're modifying the frame, to make a box that crosses between both the front and rear triangle.

Another thing you might consider is the XtraCycle frame extension. It's a bolt on thingy that adds a bunch of cargo capacity and an interesting side effect is opening up a lot of room just behind the seat where the rear wheel used to be.

- David Heron,

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