Held together with some 3D printed parts, zip ties and tape. Just wanted to see it do its thing.
It’ll balance when turned off, but you obviously can’t push it around like that. Played round with the PID settings, quite interesting seeing the effect they have.
What happens with this when it reaches motor capacity? With the normal OW it just shuts off and nosedives, what would happen with this one when it reaches its limits?
I think nosedives are inevitable when any one wheeled vehicle reaches its limit. Even an EUC will if you hit it’s top speed. What EUCs do well is make that top speed so high that it’s unlikely to be reached.
My gearing setup will give a top speed of 46km/h. If this works out ok I’d like to bump it up, just so I’ll never get near it’s top speed.
VESC apparently does field weakening now, could be an option to bump up top speed.
I know onewheels usually use high voltage Batts 12-16s, to get some decent torque on the hub motors.
Could you get away with using a 10 or 12s battery in this scenario ? As gearing could help out with torque.
I’m sure they have their reasons, but OneWheels and the hubs used by floatwheel/etc have low kv motors. There’s 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, you’re 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; it’s 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, it’s 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 that’s what I should have done.
Next step was to bend the two 45 degree angles. Ideally, I’d 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 don’t care too much about; it’ll be that scratched up the first time this end hits the road that these bubbles won’t 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 didn’t happen at all 
. I believe the plastics contact with the aluminum meant that it didn’t heat up enough (I’d 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 I’m 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 didn’t 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 didn’t 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 ok’ish 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 they’ll all be covered up.
In hindsight, I wouldn’t go for a welded frame again. Cost, makes it harder to work on, can’t 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 there’s nothing else I need for the build, only time. Just spent the last few days getting up to date on what’s 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 I’d include some louvers in the design. I’ve always liked them as a feature on race cars, and here they’ve 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 wouldn’t 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 where’s 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 there’s about 1.5kg of filament here.
Molds were sanded lightly, I’m not real concerned about seeing layer lines in the final part as it’ll likely be covered up. I’d probably recommend doing a layer of primer and sanding it down for a better finish, just make sure this doesn’t 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 it’d 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, it’s 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. It’s 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 Maguire’s 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 I’ll even use it again.
Speaking of footpads, finally got around to wiring up the sensors. Four FSRs wired into two parallel groups. I’ve not heard great things about this solution, but I guess I’ll 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, it’s 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
It’s 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, I’ve seen the GT ghosting videos 
Interesting thing about this build is that I’m fairly sure it’ll 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 you’d probably get a nasty surprise.
