This is a general how-to on building your own electric bike from off the shelf parts. I use this as my 'daily driver' once the snow if off the roads here in the North East US. I have a 16 mile commute and that can take up to 45 minutes in my car on an average day or an hour on a bad day. I clock in a consistent 30 minute commute with this machine (20mph motor power max + my pedaling it up to 30mph). As you can see in the video below, I can roll past stationary traffic.
I also cycle but that takes about 50 minutes each way. With eTrike that is roughly 3.5 hours a week of commute reduced.
In the past I've built standard 2-wheel ebikes but found them both high maintenance for the amount of mileage I do and somewhat unstable due to the high center of gravity.
The Trike setup spreads the extra weight out across three wheels and is uber stable. The major downside is visability but I think that's more a matter of perception. I clock in around 1500-2000 miles a year commuting on this thing and have had 0 issues.
First I'll step through the build from trike kit to adding the motor & battery
Step 1: Base Frame
Trikes can be expensive but I went with the UK designed KMX brand which is both cheaper but also stronger. As with making a standard ebike you want a steel frame for durability. This is what makes converting a KMX frame ideal for this application.
I also swaped out the tires for the largest schwable's that would fit on the rims. I find them an nice balance between durability and grip.
The first step is to lay out all the cabling and base components, and adjust any cable lengths before zip-tying things down. Road conditions may vary in your part of the wood. Here in Massachusetts this bike takes a beating. And on that point..
Check your local laws regarding speed. I think most states require you go no faster that 20mph on an electric bike.
Obviously the faster you go the harder those bumps hit you. My trike has a max top speed of 45mph (which I tested offroad)
Step 2: Adding the Powertrain
I replaced the rear wheel with a 1 kW pancake motor powered by a 20Ah battery based on my commute distance. There are many vendors online, I don't have a particular preference, it's cheaper to buy direct from China but takes longer to ship. You pay an overhead to more local reseller but have better support if you have an issue.
A great forum for the electric bike world is http://endless-sphere.com/forums/
I won't mention the specific Chinese vendor as I did have issues with the vendor getting caught shipping Lithium batteries out of China without the proper paperwork (A common problem it seems). I will say though that everything is made in China and the vendors over there tend to be much better at customer support than they get credit for.
You will want to take everything apart and seal components with a silicone sealant if it tends to rain where you live.
In is instructable captures a refit from the first instance of this trike. After a year of hard riding I've modified the layout to be even more durable. I moved the battery from the rack to behind the drivers seat. I also encapsulated all electrical connections in a watertight compartment.
Step 3: The Cockpit
It's critical to get the cockpit setup just right or you're going to have a bad time. Some tips
You are going to need a bigger crank; I currently have a 60tooth set on the front which covers most of my range nicely.
Leather gloves; with your hands so close to the front tires you will graze skin quite easily
Rearview; you cannot have enough mirrors. Especially useful when you need to move over to let traffic past.
Flag; because you're so low to the ground you need to make drivers more aware. I have about 2000 lumen of light pumping out the back in various forms and recently added blue reflective tape - drivers are tuned to spot blue thanks to police cars.
(note the two images with the trailer are from last year with the battery on the rack)