September 28, 2013

Finishing up the Giant Scooter

Getting the scooter to a nearly-finished state from its previous condition took a few nights of solid work.  Most of the work was done in the days leading up to the New York Maker Faire.

Last update, the scooter was basically a rolling frame.  To interface the old adjustable steering column with the motorcycle fork crown, I had to make a clamping shim to adapt the tube diameters.

To get the scooter moving on its own power, the only things to do were build a deck and battery compartment, and wire together all the electronics.

The top and bottom of the deck and battery compartment were bandsawed out of 1/8" aluminum plate.

Waterjets are for sissies
The sides of the compartment were bent from 3" wide strips of thick black acrylic.  Using acrylic turned out to be a mistake, as later one of the panels cracked.  Bends were made by clamping an aluminum plate on each side of the bend line, and heating the bend area with a heatgun.

The battery compartment fits beneath the deck and extends to the same depth as the gearbox.  Unloaded the scooter has over a foot of clearance.  The acrylic was edge tapped and fixed into place with stainless screws countersunk into the aluminum deck and underplate.

Wiring the battery pack was a bit of a mess for a few reasons.  First, I didn't leave all that much space in the battery compartment for wires.  Also, this battery pack is a funny creature: while the scooter is running, it's a 16S2P pack, for ~60V, 10Ah.  However, I don't have a 16S charger.  For charging, the pack is split into four 4S modules, which can be charged in parallel.  I needed some sort of external connector for switching the pack between charge configuration and drive configuration.

The HobbyKing hardcase LiPo bricks were fastened down with 3D-printed clamps:

This mess of wires occurred.  Without some 10 gauge Turnigy Noodle Wire this would have not been possible:

The series/parallel switching comes from these four XT90 connectors.  The boat power switch was pulled off a box of servo drives found at a lab cleanout.

Some wiring detail.  Note the gratuitous use of zip ties.

Wiring was finished at roughly 2 in the morning the day of Maker Faire, so I didn't have a chance to attach the brake caliper.  Fortunately, despite the lack of brakes, nobody was run over.

When I got back, I attached the brake caliper.  All it took was milling a funnily shaped bracket thing that screwed into the swingarm:

I still need to pocket the swingarm, because there's just too much solid metal there:

And here's the (mostly) finished scooter:  If you look closely at the fork, you'll notice that there's now a shock absorber on the outside of the fork.  I had two of the shock absorbers I originally used, so to make the fork a bit stiffer I just added the second in parallel to the first.  It's not the most elegant solution, but it vastly improves the rideability.

For reference, here's the original scooter.  Pretty neat how much of a difference one year can make.

Riding this thing is wonderful.  There was a big grassy field with a hill along one edge that I got to do some off-roading on.  The suspension smooths out the terrain extremely well.  Also, the torque is absurd.  I have the Kelly controller limited to 100 amps (out of 200 max) to avoid toasting the magmotors, and use a moderate amount of smoothing on the throttle.  This makes the vehicle a little tamer at low speeds, but if you open the throttle past ~30% it can easily pull a wheelie or throw you off.  The magmotors also seem much happier than the CIMs were.  They barely get warm in situations where the CIM's got too hot to touch.

So, that's a wrap.  My next project, which is mentally in the works, is not vehicle related for a change.  But don't worry, it has shiny motors.