Mëtal Scooter construction update #2

This will be a relatively short update on the most recent Mëtal Scooter progress. The biggest news is that the chain drive has finally begun spinning under motor power(!):

First though, I'll go over some other small stuff that has happened. After completing the epoxy etching from the last update, I painted some metallic hobby modeling paint in the groves to make the logo more apparent. Once this dried, I brushed on a final coat of epoxy to fill the remainder of the etching and give a shiny finish. It turns out that the etching wasn't cut quite as consistently as I thought; specifically the "a" letter is too deep (due to a non-level mounting on the CNC). I tried to fill it with extra epoxy to increase the strength in this section:

Next up was attaching the Razor scooter front end to the deck. The stock Razor uses a simple four hole mounting scheme to connect to the chassis. Those bolts screw in to an additional threaded steel plate on the inside of the scooter to sandwich the aluminum deck and spread the load over a greater surface area. I used the same inside plate with my deck after grinding off some pieces that didn't fit. Instead of going directly through the deck, I put in two custom 1/4" aluminum spacer plates to raise the handlebars a little and get the wheel axle at the right height. Unfortunately, a couple bend tests quickly proved that this mounting job wasn't nearly robust enough. The unidirectional carbon, while strong, flexed too much between the aluminum risers supporting it. To try and remedy this, I cut and installed four additional risers near the front to stiffen things up. If this doesn't work well enough, the back up plan is to mill out a much larger aluminum spacer plate that can double as a secondary mount into the risers.

No, I'm not about to miter saw it in half...I ran out of table space 

Meanwhile, the spacer plates for the motor mount were also being milled out (along with a throttle piece to connect to the servo tester potentiometer):

After the arrival of the new sprockets and chain, I ultimately only needed three to get the correct spacing. The sprocket installation required a little more grinding and metal cutting than I anticipated due to some poor planning, but it ultimately worked out okay. While waiting for some more hardware to mount the back wheel and motor, I also decided to get the wiring out of the way. It's a very simple setup for this scooter, just a wiring harness between the ESC, lipo, and motor with a toggle switch, charging socket, and a BEC wired in. The connectors are some cheap Deans knockoffs from HobbyKing. The toggle switch really wasn't rated for these kind of voltages or current draw. The first one stopped working after the second time, keeping the circuit closed even when turned off. I suspect the internal pieces might have gotten welded together. I've since put in an even cheaper second one, which works, but creates a sketchy spark noise every time I switch it on.

Cutting out the switch holes in the aluminum channel was another ShapeOko job. This was a truly questionable setup for a piece of this size. It took two scrap pieces of aluminum channel, duct tape, wood screws, and a cast iron drill press clamp to hold everything down long enough to cut the holes out. Luckily, the cuts went fine.

When the electronics were finished, I finally got the chance to install the chain and test out the motor. Without a chain breaking tool, I used a table grinder and a screwdriver to get the length I wanted. It took a little while to get the alignment right once it was connected, but it eventually came out pretty well:

The "motor mount slide channel" tensioning technique seems to work fine. After letting it run for 5 minutes, it became clear which parts needed thread locker or additional reinforcement. I dealt with those parts, and so far everything seems to be holding. Both the motor and wheel sprocket were welded on for simplicity (after the pain of trying to mount the old sprockets). I imagine welding to the wheel's bearing probably doesn't do anything good to its rolling friction, but then neither does the bolt and "washer spaced" axle it is on. This is an area that might be redone later.

Lastly, I began milling out the front wheel fork (the original Razor one not fitting 8" wheels). I haven't completely thought through how it will attach at the top, but it will probably involve a couple machine screws. I only finished one of the two because I ran out of cutting fluid spare air-tool lubricant. Once that piece gets cut out, only the throttle mount and a few small details need to get figured out before the scooter can get tested! Hopefully that will happen by the end of this week: