May 14, 2009

BMX ? yep, another chapter in the " Small Bike, Big Fun " book.

At first, I simply needed a bike with 20" wheels and a strong front fork in order to test some motor conbinations.

1st motor to get bolted on the BMX was a Crystalyte 404.

Large hub hubs in small wheels often means radial spokes, this is frowned upon in the bicycle world and reasons vary from being hard on hub flanges ( tendency to crack the hub ) to not being strong enough to support the loads because the spokes don't cross. However, when using Hub Motors with very large diameter and strong flanges in double walled rims, radial works just fine ( even at rediculous power levels, more on that later )


Voila ! One Electric BMX !

The crystalyte 4 series motor range from 404 ( fast ) to 4013 ( slow ), in a 20" wheel and 36v the BMX was plenty fast. ( 30+ km/h ) and 48v it was too fast but a bit more fun.

Rode that around for a few weeks, then the desire for power resulted in the next modification.

Above is a Crystalyte X5304 in the back wheel, this is a front wheel motor that i installed in teh back, notice there is no chain !

That big battery pack is a 72v 12ah LiFePo4 pack made of prismatic cells, at 72v this BMX is a riot.. insanity really.. if you hit the throttle hard from a dead stop the front wheel comes up in a hurry. FUN but not very safe lol..

I decided to run at 48v shortly after as the 72v was too heavy for my backpack, and 70+km/h on this bmx was honestly too much. 48v was suitable for daily commuting to work.


Above, the X5 had to be used for another project, a Tri-Rider trike for " Nick " so the BMX was without a motor for a short while.

A few months ago ( November 2009 ) I installed an E-BikeKit.com motor on the back

Again at 48v, but this time with " PSI " cells 10ah

This combination was excellent ! lighter than the X5 and the PSI pack 10ah vs 12ah before, also less weight, fit the controller inside the frame and it became my prefered ride for a while, small enough to easily carry up stairs or into the elevator at work.

The E-bmx was sold not long ago, so no more BMX, however this bike was enough fun for me to definately want to build another one in 2010 !

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