When I first started planning out the electric bike project I don't think I really knew what I was getting into. Who though I'd need to worry about the amount of torque is going to be applied to the frame? For those who are interested in the project I'm going to go over some of what I've learned. We're still in the planning stage, but getting closer to reality every day.

The whole idea behind this project is build a bike that can go 30KPH (18MPH)and has a range of 20 to 40 miles. Most electric bikes of this calibre cost upwards of $2000, but if you already have a bike this should be possible for 600 - 800.

In order to keep costs down I've decided to go with a front wheel hub motor as they cost about half of what a rear wheel motor does. This introduces some interesting problems though. In the picture at the left you can see two red arrows on the fork. Those arrows represent the forces on the frame of the bike.

You'll need to think of the motor that is something that pushes against the fork of the bike. When you turn the motor on to go forward a relatively small force is exerted at the very bottom of the forks. Since the forks are basically a lever with the fulcrum at the top of the forks that little force at the bottom translates into a bigger force near the top (big red arrow). The opposite is also true if we try and use re-generative braking... there's going to be a huge force applied near the top of the frame.

The solution is to control the acceleration and deceleration of the bike. You won't be able to blast off because your front wheel will take off without you. A slow steady acceleration will reduce the amount of force the bike frame absorbs. The same is true for re-generative braking. We won't try to re-capture all of the energy. Instead we'll capture as much as we can without putting too much stress on the frame.

I also need to stress that you can't use a bike that has front shocks. The bike needs to be pretty beefy. This won't be quite so smooth of a ride, but of course there's a solution for that.

Some smart guy thought it would be a good idea to put a suspension shock in the seat post. I've personally used one for the past 8 years or so and will be using it in the electric bike. They're only about $30 so it won't break the bank; however, it's going to make your ride a lot smoother.

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