I took advantage of this holiday season to build my first board, and incredibly the time from first parts procurement to a finished board was just under 3 months.
This post is a summary of the entire build process because Discourse sucks for drafting, I have a far more detailed but boring build log that I maintained during the build process in a blog. If you’re interested in that, feel free to check it out here.
Base: MBS Comp 95 “Birds” Complete
ESC: Spintend uBox with Uni1 Remote
Motors: 2x Flipsky 6374 190kv Battle-hardened
Batteries: 2x Tattu 6S 14Ah LiPos (Thanks @AK1!)
Mounts: Boardnamics Matrix II Mounts
Battery Enclosure: Apache 1800
ESC Enclosure: Zulkit Junction Box
Drive: Homemade #25 chain drive, 10T/62T
All in all, total cost for this build including taxes and shipping was just under $1200. That brings it in direct competition with many prebuilt AT boards like the Wowgo AT2, and even under some such as the Backfire Ranger X3 and Evolve.
Thanks to logistical delays, the board itself didn’t ship and deliver until Christmas Eve, and the batteries were stuck in a USPS distribution center for well over a month. I couldn’t do any building without the actual board, and I couldn’t test the electronics either without a battery, so the build really started around Christmas.
After getting the board, the first thing I did was start on the chain drive. I had designed and 3D printed a jig to match the bolt pattern of an MBS hub, but I wanted an actual hub to compare it against just in case it was off slightly. It looked fine though, so I drilled out the hole pattern on the wheel sprocket. However, it turned out that the center hole was ever so slightly too small, so I had to ream that out with a step drill bit, which was a bit of a pain. Once that was done however, I attached the sprocket onto the hub with 65mm bolts, with 2 10mm spacers in between.
Then came the motor mounts, which were fairly straightforward to install. It was kind of confusing to figure out the correct orientation however, as most sides were generally right, but one face was much flatter than the actual hangar profile. As such, when tightened, only 3 or 4 sides of the clamp actually contact the hangar instead of full contact. Seems pretty strong though, and I was worried that if I tried to round it the mount pattern wouldn’t align, so I didn’t try fixing that face. There is a tiny bit of bite from the clamps when I lean all the way, and I haven’t really figured out a good solution for that yet aside from chopping the corners off the deck. I’ll need to think about it more.
The enclosures were tricky to position, but once that got locked down, it was pretty easy to make. Because I didn’t want to shorten any of the ESC or motor wires, and I didn’t want any connections outside of the enclosure, I elected to place the ESC backwards in the enclosure, and use the length to take up wire slack. The ESC is also slightly off center to make room for the power switch, and so the power could reach the exit way off on the side. I also fiddled with the battery box orientation, before settling on the long side matching the board because the sides of the box were flat, while the front and back had ribs, which would make exiting a connector difficult. The XT90 holes were cut with a dremel, and I glued on 3D printed panel mounts using waterproof silicone adhesive. The motor umbilicals came through holes in the back of the ESC enclosure cut with the step bit, and are sealed using cable glands. As a side note, I accidentally drilled them slightly too close here, so you can’t tighten both at the same time. I call it an antivibration feature, although in the future they should be at least 2mm further apart. The enclosures and board then got some industrial outdoor Velcro to keep them together, and it’s surprisingly strong.
Final things included soldering a bridge cable between the battery and ESC enclosures, and cutting the chain for the drives. The soldering went shockingly well, as I did not anticipate my cheap 25W (or 40W, models look identical so not sure) Weller with a conical tip getting close enough to heat through 10 AWG. Yet it managed to fully tin the ends, and the connectors as well. Unfortunately I went too hard with the solder, and accidentally overflowed out the connector a little so the little end cap doesn’t go back on. I ended up snipping as much of it off, and then taping over the gap. As for the chain, it took me 3 hours and two ruined punches to get three of the pins out without a chain tool just so I can get 2 lengths of 18". Get a chain tool, you’ll thank me later.
VESC programming was a little challenging, as you’ve probably seen a few of my questions on the noob thread. I had (and still have) no idea what I’m doing, and it took a few tries and reflashes before it was set up properly. I have it currently set to 65/-65 for motor, and 80/-20 for battery, so we’ll see how that goes. I’ll tune it as I keep on riding and experimenting.