I planned on motorising it... somehow, someday. I began work on that early this year. An M.E. I correspond with told me about some scooter motors that had bike chain sprockets already. So, I tracked one down and bought it.
I had to do some "imagineering" (What to do? What to do?) and decided to fabricate a platform to mount the motor over the back tyre. I snapped a 10-24 tap and busted a drill bit in the process, owing to the hardness the struts' particular grade of aluminum - nothing that a liberal slathering of JB-Weld couldn't overcome.
I decided to use an Arduino microcontroller for a motor controller. It decodes some switches on a handheld to ramp up/down PWM levels.
First, I bench-tested the motor, to get a feel for that.
I'm going to use a MIC4427 between the PWM and those Gates. For better V_GS, and its lower r_ds[on], I'll also rig in a 6V AAA-pack, too. Then I'll give that "accelerate from a dead-stop unaided" test another shot.
>>> The STP40NF10L FETs worked out much better: I can take-off unaided and without anything burning up! <<<
I couldn't find any good info on debouncing in software, so I made this debouncing circuit for the handheld. It makes use one of the ATmega/Arduino Hardware Interrupt pins. (There's a 4x4 matrix library around, but I didn't want to dicker with that.)
$500. The ideal would be to the batteries stacked in a box located in the area under the crossbar. I went about on the streets for around 4 miles in addition to a bit of leisurely, free-style roaming in an empty parking lot this morning. I should probably fit a voltmeter on there to see how that goes - or do that with the Arduino and an LCD (BATT V = __ RPM = __) Somehow, the chain loosened up again or something, because all that slack came back. I couldn't sneak in any more washers though, even a "non-fender" flat washer was too tight. So, I shimmed up the front end of the deck (the back end hinges). The struts don't look like they're bending, so maybe the chain is stretching. We will see.
Update 29JUN2012 I'm re-working the battery tray idea by abandoning the pan idea. Last Saturday, at BigLots!, I found some plastic baskets. They look like small milk delivery cartons. I've been trying to decide whether to mount them in back, one on each side, or going with just one bungee'd to the fork which would be less work.
Update 06JUL2012 I tried out the plastic basket. I didn't want it to be tilted, even though SLA's are OK with that (I'm told), so I got a length of pipe cut and situated that between the box and the fork. With that it's nearly parallel to the ground. As you can see in the pictures, I bungeed everything into control. [How many? Seven!]
Not the sturdiest build in the world, but an improvement on the cake pan.
Maybe I should get on with that bigger sprocket - "gear up, mate" - and see if that helps or harms.
Update 23 MAY 2015
I now have a new pair of handlebars, high-rise. Got hold of some angle bracket for battery mounts. I've wanted to have them at the front of the frame, but I may go with having them at the back, either side of the rear tire.
It hit me that I never "posted the code" - check for it over in "Where's the Code?" - echopper_PBs_04