June 2017-July 2018
I got tired of biking to school.
First I made a 3D printed ebike bike conversion which I made as cheap and easy to get working as possible. However once I got a taste of the effortless ebike experience — there was no turning back.
June 2017-May 2018
The goal of this project was to get me to school fast and for as cheap as possible thus, everything was rigged together and not very permanent. In order to keep the costs down and make the fabrication easy, I designed all custom parts to 3D printable. Check out the video I made for a nice build/showcase montage.
The powertrain consists of mounting clamps around the seat tube which are then locked in place with an outer sleeve. The whole assembly was then bolted into the water bottle holder inserts that come standard with most bike frames.
The conversion uses a 24v 350w brushed DC pancake motor overvolted at 36v. A 36v, 8.8ah lithium ion battery can take this bike approximately 12 miles on a single charge with a top speed of 25mph which only occurs in good riding conditions.
Many profiles and iterations were created before arriving at the present day model. Lots of waste plastic....good thing I also made a filament recycler (*wink...go check it out!)
Overall the system was more robust than I anticipated but it is fairly inefficient because of the archaic brushed motor I used. The motor was undersized and under geared for this application despite the 90 tooth #25 sprocket threaded onto the rear wheel hub which was the largest I could find.
November 2017-July 2018
Seeing the limitations of my 3D printed ebike I wanted this second bike to be more robust and higher performance. Hub motors were ideal for their high torque, low KV, flat packaging, and most importantly — availability. However, it was very hard to find any road bike rims with a hub motor already laced at a reasonable price — thus the hub mid-drive idea was born.
I machined the mid drive mount from an aluminum plate and large aluminum U-channel. The most complex part for this build was the custom hub which I turned and single point threaded to adapt the free wheel to the hub motor. The whole mount was then bolted into the water bottle holder screws you find standard on most bikes.
A second chainring and a crank arm free wheel was added to allow the pedals to idle while the whole chain system ran.
Using NESE no solder battery cases and a bunch of used 18650 cells, I made two 13s 4p battery packs housed inside waterproof plastic cases.
It was a challenge finding cells with similar capacities and internal resistances. Oftentimes, a single series group would have a lower voltage because of a single dead cell. With mediocre, used cells at ~70% of their original capacity, both packs together still gave me around 25 miles of range.
The hub motor mid drive ebike is an absolute work horse and has well over 1000 miles on it from countless rides to and from school or around town. It is safe to say my objectives of creating a more powerful, robust last mile transportation system had been achieved but it was very heavy and bulky. This made way for my next, much smaller project (*wink check out my micro ebike!)
