I love that sicker. Especially if they’re fiber-based and not plastic. (In other words, paper — so you can soak them with epoxy to apply them permanently)(with a piece of white paper under them)
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Cool! Be warned, I did the exact same thing with a mismatched set of keyways, and my franken-key sheared in half after a couple weeks. It’s better to use an unmodified key in the small size, and shim the gap in the larger keyway with a piece of small strip or rod stock + use retaining compound.
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This is one of the things I’m worried about, was pretty tempted to use retaining compound but didn’t cause I’d like to experiment with different motors/pulleys. Guess I’ll find out 
I’d like to switch to an 80kv motor, and I think I’ll find some way to get a 4mm keyway cut in the motor shaft for that.
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As someone who’s machined keyways in motor shafts… and in pulleys…
…I have to advise against the former. It’s better & easier to machine a 3mm keyway in the pulley instead.
You need an arbor press and a 3mm keyway broach.
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It’s now finished, well finished to the point where endless tweaking can begin. Few pics before it starts to look trashed.
And the first ride (once I got it rideable).
Wanted to get started on VESC v6 for this, even though it’s still in beta. Beta package didn’t include MacOS build, and the Windows build in there didn’t support Bluetooth so ended up compiling the VESC Tool from source. My build seemed to only include the old firmware so ended up compiling the firmware too. Annoying, but it actually wasn’t as bad as expected. After that I just followed the process over here.
I’ve spent a while now messing with the various params of the VESC balance package, and it’s still pretty “meh” to be honest. Just too soft, and real-time data doesn’t show the amps getting anywhere close to the max I’ve set. May jump over to pev.dev to try and enlist some specialist support.
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One of the best things about this forum is that it’s up and open on the web, even Google’able. It’s not really the home of DIY OneWheel stuff, but I’ll keep this thread going because it’s better out in the open than buried in some Facebook group chat somewhere. That said there have been several Facebook/Discord/Telegram groups that have been really helpful, in fact, this post is just a summary of several comments I’ve made everywhere.
So a big part of this build was finding out if this kind of drive system is really feasible for this application, and I have some thoughts. The build itself seems mechanically sound, and I love the aesthetics, but the performance is woeful (my Pint is far better). This seemed off given the specs ‘in theory’ are far better; bigger battery, more powerful motor, better ESC.
My initial thoughts were that I just didn’t have the parameters in the balance package (the thing that makes the VESC do OneWheel stuff) tuned well. I tried many well-established working tunes, and variations of them; none of them seemed to work. Logging via the mobile VESC tool showed I was pushing over 80 motor amps on flat grass with the board really struggling.
So maybe it was the motor tune. Reran the motor detection in as many different ways as possible, always coming up with close-ish numbers. Almost have silent HFI going but it struggles with motor tracking under load, but that’s not going to fix the issue anyway. Ran a very unscientific experiment with the belt drive vs the Pint. It’s pretty simple, let both run at the max speed and try to stop the wheel spinning through whatever means. In the case of the Pint I could actually slow down and probably stop the wheel. Zero chance with the belt drive, wheel speed didn’t deviate at all no matter what I threw at it. Was kind of scary actually. However, repeat at low speeds and you get the opposite results. The belt drive definitely has the power, just not where it’s needed.
Motor KV selection and gearing was chosen to give a reasonable top speed, but I believe the actual KV of the motor is a bit higher than the advertised 50kv. Following calcs based on 14 motor poles, VESC reported voltage of 49, ERPM of 18862, and a duty cycle of 95%.
pole pairs * rpm = erpm
rpm = erpm / pole pairs
= 18862 / 7
= 2695
speed = 2695/60 * (22/49) * 0.280 * pi
= 17.74 m/s
= 63.9 km/h = 39mph
rpm @ 100% duty cycle = 2695 / 0.95 = 2837
kv = 2837 / 49
= 58
I’ve ordered a 12t pulley that will half the top speed and increase the low-speed torque. The real issue is that at these low RPMs the motor seems to be operating very inefficiently. I’m fairly pessimistic that even doubling the reduction will get it out of this inefficient range of rpm/torque. It’s worth a shot for a pulley change!
Probably not surprising that when you research the motor characteristic for low-speed torque you find out it looks a lot like what is used in OneWheel hubs. Lots of motor slots, big diameter, lots of copper windings. I still think electric motors are always better off with a reduction, but I definitely no longer think drive reductions can be used to change the torque characteristics like I needed and expected here.
If the pulley doesn’t work out this project could go several ways;
- Leave it as is and move on
- Just buy a SuperFlux/CannonCore/OneWheel hub, and add a split 6s pack up front to make 18s overall. Would need new VESC and BMS.
- Design/build my own brushless motor with more favorable characteristics.
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Extremely interesting thoughts and findings! I would just throw it out there that I have not seen a single attempt at a EUC design with a gear reduction, given they have the room for a massive hub motor its not surprising.
Almost like the drag in the drivetrain at low speed robs you of the power so badly needed at those speeds. If you set brake amps to 0 how much shorter is the free spin with the belt drive vs hub motor?
Given your results with a moderate amount of power I am not sure how good of an idea it is to throw even more power at the issue. Scaling to two motors would not be super difficult with the design I would go with, so I might resort to trying it. 200 battery amps would be quite insane to see put into such a small vehicle.
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With two motors you’re halving the torque required by each, it’s obviously a good thing, but will it be enough considering you’ll probably get stuck with motors that just aren’t optimal for low-speed torque. The inefficiency has two problems that go with it; the obvious one is that the board doesn’t move, not so obvious that all that “lost” power ends up as heat.
Have you had any thoughts on motor selection for your build? I’ve not found any options that are a good fit packaging-wise. Would be interesting to fit a 150mm+ drone motor in somewhere, something like this. Would be another expensive experiment though.
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In my dream world a 6384 motor is fine. So be it if you want to go faster than 10mph that you need two 6374 motors. Probably not gonna work out tbh.
Wow that is a big fat motor you linked. Im sure sure how durable they make those things. Lotta weight spinning around.
I thought you meant like this size
My serious answer to what motor I would use after I tested with a 6384 is probably something oversized I guess larger than 80100.
This is the kind of dumb idea I usually save for my own threads but you could take two floatwheel hubs and put them where the batteries normally are, chain drives to hub in middle. Problem solved.
That dual motor board (almost 3 wheel like) would actually be more suited for a tank track drive system. Again definitely something silly.
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Discovered the other day that I have roll to start enabled. Not sure how I feel about this, kind of dangerous, kind of neat. I just need to learn how to balance on it while off for the 10 seconds or so it takes to boot up 
The 12t motor pulley arrived (down from 22t), this gives a new max speed of 34km/h (21mph). Whatever tune parameters I was using on the old gearing were just garbage so I scraped them all and went back to a default set of parameters I grabbed from pev.dev. Unlike last time, these worked really quite well. It rides differently to the Pint, not worse, just different. More tweaking required.
The whole rear end of the board needs to be disassembled to change out the motor pulley. That’s a lot of screws.
The smaller pulley saves about 250g (0.6lbs), which is great, the board now weighs 12.9kg (28.4lbs). The downside is it just kind of sits angled nose down yet not touching the ground, not very “OneWheel”
Low speed performance on longish grass still isn’t great. I see the highest battery/motor current in this situation along with some cogging (not as bad as with old gearing). I’ve got some AS5047 encoders on order to see if this helps with the low speed stuff. Not sure how I feel about the slower top speed, I’ll hardly be pushing that any time soon, but may still investigate field weakening. I’ve also got a 15t pulley to try out.
I’m a little concerned about losing a bunch of teeth on the motor pulley, and this leading to belt slippage. Considering introducing an idler pulley that would run the belt like shown below. Definitely better tooth engagement, but to implement it I’d probably screw a 10mm shoulder bolt (m8 thread) into the rail. It’d be cantilevered and may introduce a bit of flex into the system.
Smaller pulley worked out better than I expected, and before testing I was seriously looking around at other motor options. Some good options from Neumotor, but I think I like this one from Revolt more (bigger, cheaper). Trying to fit it under the board could be problematic. Image below shows the 80mm layout vs the 107mm diameter of this motor.
Of course really what it needs right now is for me to get padded up and take it out for a decent ride.
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Encoder finally showed up 
. Those cheap AS5047p encoders from AliExpress don’t come with the special magnets. Fortunately, there’s one online store in all of Australia that seemed to stock diametrically magnetized magnets, so I didn’t need to wait another month to ship some from China. I’m not against Digi-Key etc, it’s just the shipping was going to cost more than the part!
Followed this awesome FreeSK8 guide for wiring up the encoder, and it all worked out great. Was worried about using 5v as it supposedly results in more noise, but I see at most 0.1 degrees of noise in the signal, and that seems good to me.
All wired up in its 3D printed housing.
And then installed on the board. Testing out an encoder was always part of the plan, so this space was kind of reserved for it. Housing bolts up to the standard 44mm bolt pattern 63mm motors use.
I used one of surfdado’s tests to see if the encoder helps at all. I’m sure there are better tests, but all you need is a few planks of wood so 
. Much less subjective than taking it for a ride to see if it “feels better”.
Anyway here’s a bunch of before and after footage wrapped up in a nice short YouTube clip.
tl;dr - It helped a LOT!
Neither the Pint or this board (pre-encoder) were able to clear the 25mm step. That said, the Pint did have much better low-speed torque which had me thinking. My current theory is that the OneWheel hubs have 30 magnets whereas I have 14, this means the hall sensors will be switched twice as often allowing the OneWheel much better motor tracking.
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All that oomph on 12S! wicked!!!
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Got padded out and took it out for a ride today. Did not get dropped on my face, so overall I’ll call it a win.
Rode for a total of 6km (3.7mi), a mix of mostly concrete paths but with a bit of dirt/grass. Tried to really push it on a few of the little hills around, well push it as much as I was comfortable with. Below includes the data from the short ride in the above clip. That grass section is a reasonably steep little hill.
Nothing really seemed off, well that’s until I stopped to feel the motor (there’s no temp sensor), it was hot enough not to be able to touch for long 
. Stopped to let it cool before doing more hill repeats. It was a hot day today (35°C / 95°F), but I expect this could still be an issue on cooler days. Rails were quite warm too which is good/bad; good that the heat is being transferred to them (they’re effectively a 2.5kg heatsink), bad that it still didn’t keep temps in check.
I suspect that despite all the documented ratings, the 80100 motor in 50kv form, really isn’t good for the kind of amps I’m feeding it.
Pushed it on the way home up to the duty cycle tiltback (80%) while watching the VESC RT data just to check if the board would actually tilt back. It did. This worked out to be a little over 26km/h (16mph), which is faster than I’ve gone on my Pint. Consumption wise it averaged 15wh/km, not sure how that compares. Probably had less than 10psi in the tire.
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You can try this fan, but idk if you rev high enough to get good use out of it
That’s a nice fan! But as you said, I don’t think the motor is going to be spinning fast enough for it to generate enough airflow to make a difference. Was thinking about something like a powered CPU cooling fan, but I’m not sure that would make much of a difference either.
Kind of feels like treating the symptom and not the cause.
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I feel ya. I don’t have great thermals on my 80100 motor either, this model line was really made for airplanes to give them ram air cooling
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Glamour shot for 2022 BotY - thanks @BenjaminF . I’ll opt to put this in the innovation category. It’s not an esk8, so probably fits best, and I probably do 50/50 when it comes to street vs offroad anyway.
It’s a bit dirtier/banged up now, and I like it, looked way too clean in some of those other ‘just finished’ photos.
Thanks for the nomination BTW @Flyboy
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I know you’re still fine tuning it, but how does it feel now compared to the pint?
The best answer I can really give is “different”, but that’s a cop-out. I honestly don’t have enough OneWheel experience; in ride time or board variety, to be a great judge here. I’d like to get others’ feedback at some stage but need to be confident in the board first. The local (Melbourne, Aus) OneWheel group seems fairly active, although I’m not sure how down the VESC rabbit hole any of them have gone.
I really need to figure out some good back-to-back performance tests; something less subjective than ‘feels good’. If it’s beating the Pint it’s at least in the same ballpark as other OneWheels. I’d love something like a OneWheel dyno.
I ride the Pint with 18psi in the tire, always thought that’s just the way OneWheels ride. This thing I keep at about 12psi or so, I’m pretty sure the tire has a slow leak and settles around this pressure. Its tire is 0.5 in bigger in outside diameter, and 1in smaller on the inside diameter (5in hub); that adds up to a fair bit more sidewall. There’s none of that getting bounced side-to-side like on the Pint, and a lot of the bumps (say up to an inch) you really notice on the Pint just seem to not be there. But then maybe an XR with low pressure and its wider tire would be the same
It’s quicker than the Pint; both in top speed (not by much) and acceleration. I’ve not tried field weakening yet so that could potentially bump up the top speed. Not hitting any battery limits (30a is about the max I’ve seen from a 12s3p p42a), and the VESC doesn’t seem to be overheating. I did some stationary hill starts on a concrete path and really stomped on the front, this it handled well. Repeating the same on a similarly sloped grass hill gives moments where it feels like you need to be careful/backoff. The Pint kind of always feels like that on grass.
Interestingly there’s no feel of belt slop. Rocking back and forth in the spot feels very much like the Pint. Hasn’t skipped a tooth yet either. Not that it would skip a single tooth; it’s more likely any skip would kick the PID loop into overdrive and shred the belt entirely.
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I don’t know if you’re aware of the float wheel (mass produced VESC board currently being developed/manufactured) , but they recently teased the idea of a belt driven version.
There’s a Reddit thread here about it, with a few opinions on the topic, some will be more helpful than others. Something I didn’t know is that the original onewheels were belt driven
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