I wanna start documenting this build, cause it’s gonna take a while and it’s more fun to post updates.
So I kinda got obsessed with vesc onewheels last year.
After doing some research my strategy is basically “cheap out on everything except the motor”.
Once again a lot of my choices are driven by shipping logistics, or rather lack of proper logistics for proper parts.
Originally I was thinking about Superflux motor, but at 10.5kg it’s too heavy, and Fungineers didn’t have shipping to Serbia at that time. And then I found a cheaper used XR motor (7.5kg) together with fresh Thunder tire and cold blocks installed, all with ebay international shipping from US.
I have 2 UBOXes 100v100A that I was planning to use for Kicker 2 build, but I ended up using FSESC 6.7 on it.
Cells are Tenpower 50XG.
Something my metric mind cannot comprehend - inner screws on XR motor are M8, while outer are 5/16-18TPI
I ALMOST tried forcing M8 screw and almost ruined the threads
The bastards! Your wheel is gonna crash into Mars at this rate.
Cool concept, I’m looking forward to how it turns out. I would humbly recommend that you also don’t cheap out on the ESC, that’s an easy way to get burned.
Since it’s gonna have a swappable battery it needs an antispark somewhere in the system.
And from what I heard, most antispark connectors like xt90S are not rated for repeated high voltage plugging.
There are AS150 antispark bullet connectors, that are self contained:
Nice. I like it. This is very similar to my board designs. I have some posts you can check out. Your choice for rails is solid. I don’t see that failing. The weak point will be where they are bolted to the center rail. I think 3 holes is solid but you might consider larger diameter hardware to avoid deformation of the holes.
Something you might consider that I have been working into my boards: Adjustable rail angle and adjustable tire space.
Thanks! Yea, I’ve seen your trail board build, huge inspiration.
I also had a suspension idea, but then I decided to dial it back a notch, it’s already too complicated for me.
I like your suspension idea. I found that from the forces exerted and the repetition, elastomers can get obliterated. I would consider a very hard, durable rubber like SBR. I like this idea because a little bit of flexation goes a long way to making the board feel smoother.
For the bolt size I would do some simplified calcs in excel. If your rails fail this is where it will happen. Bolt Bearing I would use 3 or 4 times your body weight for the design force. Maybe that is overdesign since you have multiple bolts.
I think the bearing spacers is a good idea. I opted to use binding barrels/barrel bolts to do something similar. Good stuff.
For making those big cutouts in the side of the tube, a better strategy would be to rough it in with an oscillating saw and clean it up with a Dremel, and the best option would be to use a hand router with printed templates. Those will take some doing to make precisely without CNC milling.
Impact weight
W = 70kg x 4times x G = 2744 N
Moment per joint
M = 2744N * 250mm / 4 = 171500 N*mm
Distance from center of rotation to screw
r = 17.3mm
Force per hole (6 holes per joint)
F = M / (6 * r) = 1652 N
Bearing area
A = 5 * 2 = 10mm2
Bearing stress
S = F / A = 165.2 MPa
You’re right on the money.
By rought calculations with m5 holes at ~30mm triangle at 4 times body weight it’s 165MPa of pressure.
6063 T5 yield is 145 MPa
I can increase spacing to ~35mm - 141MPa
Increase diameter to M6 - 137MPa
Or both - 117MPa
I found that cutting aluminum with an angle grinder and cut off wheel the trick was to not use too much pressure which would gum up the wheel and it would stop cutting.
I did mistakenly buy cut off wheels for bricks and tiles and such, and these shred and lose diameter pretty quickly on metal, but with aluminum it seemed to help a little, perhaps as the gummed up bits would fling off.
I guess it also depends on the grade of aluminum, and I have no Idea what grade I was cutting,
