Iām sure they have their reasons, but OneWheels and the hubs used by floatwheel/etc have low kv motors. Thereās not really a range of kv motors you can choose from like with esk8. You need to go high voltage for speed, not so much torque.
Anyway, youāre right. Having a reduction step gives a lot more flexibility in pretty much everything; battery voltage, motor kv, wheel diameter. You just need to run the numbers through an esk8 calculator to make sure you get the desired speed.
The bottom part of the battery enclosure was this rather large 3D print. This was only ever a temporary solution, just had no confidence it would survive long at all.
Plan is to use a clear sheet of polycarbonate; itās strong, I can put lights/oled screen behind it, and I grew up when those clear case Game Boys were cool (or any electronic device for that matter).
Drilling polycarbonate is pretty easy, itās acrylic you need to watch out for. Both look very similar but have very different material properties. You can actually cold work polycarbonate and maybe thatās what I should have done.
Next step was to bend the two 45 degree angles. Ideally, Iād use a sheet metal bender or a nichrome wire plastic bender but have neither. I do have a heat gun though. Used some bits of wood to limit how much of the plastic would heat up.
Waved the heat gun up and down that gap till the plastic was soft enough to bend. The first problem was some bubbling on the surface. This I donāt care too much about; itāll be that scratched up the first time this end hits the road that these bubbles wonāt be noticeable.
Now for some irony. The idea behind bending it on the frame itself was to get the bend to match up with the frame perfectly, but as you can see that didnāt happen at all 
. I believe the plastics contact with the aluminum meant that it didnāt heat up enough (Iād basically given it a huge heatsink), and as a result the only bit that got hot enough to bend was away from the corner I wanted it to bend around.
Not sure Iām ok with this. Next attempt I might try to insulate with a strip of masonite between the frame and plastic.
Anyway, still had to bolt it together to see what it looked like.
Spent way too long figuring out how I was going to accurately cut up the aluminum for the rails. Do I buy a drop saw, milling machine, hand router, etc. The thing is I didnāt really want to buy any of those tools, so chopped it up with a hacksaw (helped by some 3D printed miter boxes) and got the lengths down to a good tolerance/square with a crappy little disk sander.
It worked really well in the end; both rails were within 0.1mm of each other.
What didnāt go so well was drilling holes where I wanted them to go, but this did improve over time. Tried center punching first, and that was okāish but not great. Then moved on to what I believed was the correct approach of using a center drill first then the actual drill bit. This worked better, but I often found the small tip would snap within the part you were drilling. You then get stuck with a bit of HSS drill bit stuck down the hole you want to drill. I destroyed so many bits.
The center drill (left) is to be used for use on lathes, what I should have been using is a spotting drill bit (right) which is also sometimes referred to as a center drill bit 
. Picked up a few cheap countersink and counterbore bits from aliexpress, the power button counterbore was 20mm in diameter which my small drill press handled surprisingly well.
Tapping threads is now my least favorite thing in this build. There are about 40 m4 threads that needed to be done. The little 3D printed part did help keep the tap perpendicular, still sucks.
I did leave some of the tapping till after the frame was welded, but only because I was so over it. Marked up the different parts and dropped it off at a local fab shop that specialised in car intercoolers/catch cans/etc.
Same day service is not what I was expecting, but sure enough I got a call back that same day saying the job was done.
Welds look good, pity theyāll all be covered up.
In hindsight, I wouldnāt go for a welded frame again. Cost, makes it harder to work on, canāt change the width of the board (for wider/slimmer wheels).
Closer to a test ride?
This build inspired anyone else to make serious plans?
No 
. Life stuff just kind of gets in the way sometimes. I have started working on this again, and thereās nothing else I need for the build, only time. Just spent the last few days getting up to date on whatās changed VESC balancing app and it seems like a good time to get this build actually finished.
Designed and printed a little cover for the motor/VESC a while back.
Obviously not going for waterproof, even splashproof, so figured Iād include some louvers in the design. Iāve always liked them as a feature on race cars, and here theyāve even functional as this is covering up both the motor and ESC.
Also made a forged carbon fiber footpad (next update post) which turned out nicely. This is actually what got me bogged down with the build, the 3d printed molds took some 6 days of solid printing (big and high % infill) and while the carbon part survived the mold did not. Went through all the effort of making one, but just lost all motivation to repeat the whole process.
The process can be a drag sometimes definitely, but keep going dude! Would be super cool to see
Be careful with polycarbonate it has a tendency to stress crack/craze when exposed to some solvents or to UV then you are left with a lot of microcracks along the bend ^^ (already saw it on some things like ticket machine covers and such)
Threadlocker will also absolutely destroy it.
This is good to know. Chances of me getting threadlocker on this were high, and I likely wouldnāt have cared too much.
I watched that Easy Composites video on making forged carbon parts a while back and have meant to try it. Looked pretty idiot-proof, unlike some other carbon fiber processes. I could have just used a bit of wood for the footpads here, but whereās the fun in that.
Started out designing/printing the molds. These are too big for my printer so they had to be printed in sections; male mold was glued together, female was held together by two threaded rods. Idea being that this would make it easier to get the part out. Printed at 60% infill, so thereās about 1.5kg of filament here.
Molds were sanded lightly, Iām not real concerned about seeing layer lines in the final part as itāll likely be covered up. Iād probably recommend doing a layer of primer and sanding it down for a better finish, just make sure this doesnāt mess up your tolerance between the male and female sides.
Those holes in the female side are ejection points I can hopefully use to get the part out without destroying the mold.
I go for 3 coats of PVA mold release, followed by a few coats of a spray on wax mold release (J-Wax).
The part is mostly flat, but does vary in thickness from 5-15mm. Given this, I thought itād be ok to mix it up a little and use a mix of the chopped carbon and woven fibers.
Followed the calculations in the Easy Composites video to work out the amount of carbon vs resin and it all worked out ok. Just enough resin to make sure everything was wet down enough. No photos of packing the mold as gloves were just covered in a mess of resin and chopped carbon. I will say that spacing the woven carbon at regular intervals throughout the chopped carbon did make things a lot easier, itās a lot easier to wet down than the chopped stuff and kind of held it in place.
Once the mold was packed it was time to clamp. Used two sheets of masonite to help spread the clamping force, would have preferred some metal plates but just too hard find/cut to size.
Be prepared for a lot of resin to drain out!
Popped the male mold off two days later, and this came off rather easily.
But totally destroyed the female side.
Washed it, cut/sanded off the mold flash, drilled the holes (the countersink was in mold, but not the through hole), and we have a completed part.
Pics from above are a mix of the first and second footpad, second footpad is currently curing so hopefully all goes ok as it did for the first. Itās a bit of effort but seems like a great way to make some stiff/light/decent-looking parts.
The forged carbon looks like it came out really well. Shame about the mould not serviving, maybe more release agent. You could try Maguireās mould wax on the 3d print, build up layers and let each harden up. Some times warming the mould up with a hair dryer can help it to seperate.
Good luck on the build.
FWIW I did manage to demold the other footpad without destroying the mold, not that Iāll even use it again.
Speaking of footpads, finally got around to wiring up the sensors. Four FSRs wired into two parallel groups. Iāve not heard great things about this solution, but I guess Iāll find out. Must have done something to one of them the first time around as I found one of the parallel groups to be always closed
I think everyone knows carbon fiber is conductive. I was curious though so stuck a multimeter to each end of my footpad, and sure enough, it really was quite conductive. Not a big deal, just means most surfaces the battery will come in contact with are conductive, itās enough to cause a little concern.
Lined the aluminium and carbon surfaces with Tesa tape, and then another layer of 3mm thick neoprene.
Then the battery was stuck down to the polycarbonate base with double sided tape.
And then the enclosure gets sealed up for hopefully the last time.
Battery still charges, footpad sensors still work, and nothing rattles/moves
Itās critical that the foot sensors work properly or you can have your wheel run away on you (without a rider) and crash.
Really nice work with the FlexiBMS!
what is the display? and that other gray box?
also what charge port?
Last thing is you missed a little opportunity to rewrap the cells with clear shrink and use clear shrink on the whole pack so you could see the cells when fuly put together. Ignoring fishpaper and foam its a great idea 
Yeah, Iāve seen the GT ghosting videos 
Interesting thing about this build is that Iām fairly sure itāll end up naturally balanced. As in it sits level even when powered off, powered on & armed it just kind of sits there too. Not something I want to rely on, maybe just a bit of redundancy. On the other hand, it it was powered on & armed and you tried to step on one of the ends, well youād probably get a nasty surprise.
my split pack board has that equal weight distribution property. It is annoying trying to mount the board while its facing downhill because it wants to stay nose down and basically starting in a downhill nosedive position is not ideal.
Good for some stuff I am sure, not amazing overall.
The whole FlexiBMS story is a bit sad really. Even now you could probably rework the firmware to use the latest VESC BMS spec CAN comms and itāll be a great little BMS. Kind of hard to justify this effort given they arenāt being produced. Thanks again @SimosMCmuffin
The other grey box is basically one of Mitchās balance buddies (Arduino + CAN module) but hacked to talk to a FlexiBMS instead of a VESC. OLED is connected to this. FlexiBMS powers on the Arduino when the charge plug is connected. Itās a lot of stuff just to show cell voltages, but as I didnāt want to connect it up via CAN to the VESC, itās the only way I could see this info without opening the board up and connecting via USB. More details here.
I donāt even know how to refer to it . On aliexpress, where it came from, itād called a ā0B FGG EGG 2-pin aviation metal connectorā. Rated for 10A.
Close to being done.
Grip tape, a little more cable management, and a bunch of VESCāing are about it.
Remounted the VESC mounting plate, and the VESC. Thermal paste because I really wanted to capitalize on the frame being a 2kg aluminum heat sink.
Following that the motor mounts and motor go on. This was mostly straightforward except for the motor shaft having a 3mm keyway, while the pulley has a 4mm keyway, so ended up making this. Itās not a great solution TBH.
Printed out two boxes to mount/shield electronics. One in the middle is the Bluetooth module; it still seems to connect ok despite being sandwiched between an aluminum plate and the carbon footpad. Box on the right just includes the two step-down resistors needed for the footpad FSRs with some JST connectors.
If I had a mill I would have cut a channel into the rails to run the battery/footpad wires to the rear, but I donāt. Instead, the cables run along the top of the rail which left them a little exposed. This printed guard should hopefully shield them from accidental bumps.
That thing is looking MEAN!
Maybe you could make rail decals that have something like a shark with the teeth being where the belt is.
That custom key conversion is the cherry on this DIY cake hahahaā¦ or is it literally everything else in this masterpiece.
