Electric Mountainboard Build Part 6: Final Touches and VESC Configuration

The board is almost ready to go, and there's only a few things left before turning it on for the first time!

For the previous part, click here!

Chains

Getting the chains sized was a frustrating and messy process, so no pictures were taken. In short, I had a ten foot section of #25 chain, and each drive needed exactly 18" of it, or 72 links. The difficult part was knocking out the pins so I can split it, as I did not have a chain tool. It ended up taking several hours to remove three pins using a mix of hammers, punches, and hex bits. After a while, it eventually worked, and I installed master links so it would be much easier to remove in the future. After verifying the sprockets were in line, the chain went on, and the motor was moved so the chain was under tension, and tightened all the screws. Once the proper tension was found, I removed one screw at a time, and applied Loctite so it doesn't vibrate out.

Chains on, it was eventually tensioned a little more before being Loctited on

Bridge Cable

I was worried that this step would be very difficult due to the relatively weak power of the soldering iron, but it ended up being ok. I first threaded some thin 16AWG wire I had lying around through the bindings to get an estimate for the wire path, and also measured out how long the wire needed to be. That ended up being around 14" long. Then, I cut the 10AWG wire to size, and tinned the ends. With that, I tinned the connectors and soldered them onto the wires. The connectors were clamped with a drill press vise not only to hold it in place, but to provide an enormous heat sink to help keep it from melting. Unfortunately, I made a mistake and put way too much solder onto one of the connectors which leaked out, and couldn't fit the cap back on. After sanding and cutting away as much as I could unsuccessfully, I just decided to stick it on as tight as possible and tape it together. There wasn't much sticking out so it should be relatively safe. After the connectors were soldered on, it was threaded through the binding to keep it protected and out of the way.

Another whoops

Final Touches

I decided to add some 3D printed bearing spacers for the wheels. They're not strictly required, but I feel better with them in. I found the files on Thingiverse, and printed them out of PLA+. I didn't need to do any post processing on them, and it slid right in.

Spacers, not much to them

The extra long bolts were nagging me, so I decided to cut them. I used an electrical crimper/cutter that happened to be metric to trim the bolts by 7mm. This was better than using a dremel or hacksaw because it didn't heat up the bolt, and retained the threads fairly well. With the shorter bolts, I could now move the motor mounts outwards again, to 25mm from the edge. This will also help a tiny bit against the deck bite, as I don't need to cut off as much as originally planned.

Bolt cutting

The final step is tensioning the chain, and putting blue loctite on the grub screws. One came loose and fell out when I was testing the system, and I had to put a spare one in as I couldn't find it. Once that's done, the board is functionally complete!

Finished board!

VESC Programming

This is where a different kind of challenge shows up. It's probably easiest to break it up into three distinct parts: firmware flashing, motor setup, and input setup. It becomes fairly straightforward once you get the hang of it, but it took a little bit of trial and error, and a lot of reflashing to get it right.

Firmware

Flashing the firmware was the most painless part of this whole process. I utilized the custom 100A firmware provided by Spintend for my ESC. I plugged the USB cable into ESC A, and used the VESC tool to flash the custom firmware onto both ESCs. 

Motors

Motors were a little trickier, but still worked reasonably well. I ran the motor detection wizard, which worked fine. The motor detection produced numbers that matched expected values, and were well matched with each other. After the wizard, I adjusted the motor and battery amps. For motor amps, I dropped the max amps and max regen amps from 75A to 65A, and changed the battery regen to -20A. I can raise them in the future as I get more comfortable with it.

Input

Input was the challenging one. The first time I tried running the wizard, it wouldn't detect the remote at all. As it turns out, the bundled Uni1 remote operates using UART by default, while the tool was looking for PPM. After setting the remote to PPM and disabling UART, the wizard was able to recognize the input. After setting limits for the scroll wheel, slightly decreasing dead zone,  and slightly increasing negative ramp time, the board was set up!

Bluetooth

I wanted to put a quick addendum on getting Bluetooth set up on the uBox. Bluetooth allows the ESC to connect to the VESC tool mobile app, which lets me change settings on the fly without having to unscrew my enclosure and plug the USB cable in. Since the remote uses UART by default and you can't have both sides using UART at once, the remote UART has to be turned off. Only then does the remote let you turn on Bluetooth to a side. Once that's turned on, scanning with the VESC app should automatically pair it, and from then on you can do almost everything you can do on the desktop version. However, it seems like remote telemetry relies on the UART connection, so you can either get telemetry on the app or remote, but not both at the same time.

Next Steps

Now that the board is fully built and programmed, it is time for bench testing and real world riding! The final part will detail the results of the testing, and any changes that need to be made from that testing.

For the next part, click here!