Build it Now!
I wrote a short writeup for anyone willing to make or build upon this design. You can visit the project page by clicking HERE.
Circa 2008. At age 13 my adolescent mind desired a motorized bicycle. With absolutely no budget, I began brainstorming ways to cannibalize my seldom-used Razor E300 electric scooter with its rusty bearings and dry SLA batteries… This is the short story about how my DIY e-bike came to be.
After some trial and error with some early ideas, and just as I was about to push the project aside for the upcoming school year, I came up with an Idea that uses two very simple U-bolts and structurally nothing else.
Budding the mounting flange of the 24vdc motor to the front fork of my Trek 4300 (and later the 4-Series) I took some measurements and persuaded my father to buy me two 1.5 inch U-bolts for a few dollars from the local hardware store.
Some minor filing was needed on one of the bolts to get it to fit where I wanted it, but once I got the motor mounted to the front fork of the bike, and had the suspension locked (properly with dedicated switch), I had to find a way to deliver its output to the front wheel. For this, I found that a basic skateboard wheel (sans bearings) epoxied to the motor’s original sprocket and nut would work just fine. I later replaced this with a proper motor arbor after I found the epoxy beginning to wear out. I also found that some all-weather grip-tape applied to this drive wheel gave it much more needed traction in wet weather.
The SLA batteries and motor controller were stored in a canvas tool bag atop a pre-existing carrier rack. On larger bikes, like my later Trek 4-Series, this “tool bag” can be strapped to a modified (simply bent open) cup holder in the center of the frame. The scooter’s throttle handle follows a standard diameter and easily clamps on between the shifter and right handle grip of the bike.
This was the setup I drove for a couple years before I out-grew my bike. No worries though, I found that this system is easily transferable to most other Trek Bycicles (and possibly other brands as well) after I got my Trek 4-Series. It only takes four nuts, a small tie-down strap, and one zip-tie for anyone to remove or transfer this system to another bike.
On a full charge, with two 12v 10Ah SLA batteries (a bit larger then the scooter’s original 7Ah set), this motorized bike will pull you along at 20mph (32.2Kph) for 10 miles (16.1Km) seldom-assisted (I.e. only helping it when accelerating from stops). It certainly adds loads of fun to an otherwise normal bike ride.
To this day I have not found a better diy electric bicycle conversion with all the benefits of this one. It doesn’t damage or alter the bike itself in any way, it’s easily removed or transferred to other bikes, and it costs virtually nothing compared to the commercial kits and hub motors.