My last build was a Trampa. It turned out fine, a few things could be better, but nothing too annoying that I could be bothered to change. It was finished. I rode it for a while, but after some time it started collecting dust and a few years later it was sold. Building something like a one wheel from the ground up, which takes forever to put together and is followed by endless software tweaking made perfect sense.
Why the belt? Hub motors seem like a weird thing to be biased against, but I donāt like them. On the plus side, they are quiet, mechanically simple, and more robust/reliable/lower maintenance. I can see why a company with an aversion to customers performing maintenance on their devices would adopt hub motors. BUT, with some reduction (belt, gear or chain), you potentially win in power output, lower heat generation, better cooling, lighter weight, flexibility in gearing/speed, and part selection/availability.
Belted one wheels arenāt a new idea; in fact, one wheels before OneWheel came along were all belt or chain driven. Kyleās (FutureMotion guy) early OneWheel prototypes were chain-driven too. They all seemed to work ok; hereās a list of the few I know of.
Some of these are pretty funny, and some way off the OneWheel experience people expect. Technology has improved quite a bit since then, many of these used old brushed DC motors, some with lead-acid batteries. None used a VESC, which has seen quite a lot of development targeting self-balancing applications lately. The thinking is these improvements warrant revisiting the idea of a belted one wheel.
Iāll do several follow-up posts on the details so far; by the time I get through the backlog of those, it may be ridable. Itās not too far off now.
I certainly made parts of this build harder than it needed to be. The easy solution for wheel and tire would have been to grab a 6in rim, and any one of the popular aftermarket OneWheel tires. The hard way was to use the standard 5in GoKart tire for around here (Australia); cheaper tires, more sidewall to flex giving a smoother ride and better carvability. OneWheel GT owners seem to be going to huge lengths to run a 6in tire in place of the OE 6.5in tire, so more tire == better tire?
First wheel/tire I purchased was the one on the right. 130mm rim width, with an 11 x 5.0 - 5 tire (11in outer diameter, 5.0in width, 5in hub diameter). I didnāt own the Pint at the time but knew what tire size they took, hence going for something with a similar size. Later on (mid-way through one of the Worldās longest COVID lockdowns) I bought the Pint and quickly realised that the tire/wheel I was designing around was quite a bit slimmer. This was in spite of the tire labeling indicating my tire was half an inch wider than the Pint tire. After riding the Pint I was quite certain I needed a wider tire and then ended up with the one in the middle (11 x 6.5 - 5 on a 180mm wide rim).
Would have preferred a slick tire, but around here you get slicks in 4in wide tires used as front Kart tires or 7.1in for the rear. Wet rear tires, which is what you see here, are the only ones that have a comparable width to OneWheel tires. Hoosier has a few slick options Iād like to try, but shipping costs from the US were pretty extreme.
Annoying buying wheels/tires I didnāt really need, but on the other hand, itāll be very easy to change wheels so Iām looking forward to trying out both. May even try stretching the 5in wide tire over the 180mm wide hub.
Iāve got two of these sitting around from another incomplete project. It shares the same outer diameter so will technically fit, but has a very different hub setup so would require a bit of work to get it mounted.
Looking forward to seeing how this develops. The GT uses a 6.5" tire for no other reason than FFM want to be dicks. The tire size is not normal and at this stage thereās only one manufacturer of dubious quality producing tires in this size - there are 3rd party vendors planning on making specific GT sized tires. Everyone with a GT seems to hate the tire whether itās slick or treaded, thatās why people are trying to use a 6" rim or mod the GT rim.
Thereās numerous parts of the GT which are purely to fuck the consumers. I donāt think they thought the 3rd party vendors would go and get a specific tire designed but thatās already in the works, I imagine theyāll start being released in the next few months.
FFMās ridiculous business practices are so opposite any potential green benefits OWās may have and the way the GT has been designed - to brick itself if you disconnect the BMS just means more landfill once you have a battery issue
Future Motion almost certainly have tires containing DRM chips on their whiteboard right now. Change the tire? Brick the vehicle! Send it to us! We fix! *
*only $3499.95 for tire change. Guaranteed turnaround in 565 days. Battery DRM times out after 550 days, might want to get that changed while itās here in the shop. Fuck your right to repair and fuck you, pay us now. Or you could buy a new one, they are in stock right now!
You thought Apple was morally bankrupt? Hold our beersā¦
I donāt believe it will be economically viable to have my OneWheel Pint fixed by FutureMotion if it breaks. Shipping + repair costs would likely be up around replacement value. It was going to cost 70USD to ship a single tire from the US to Australia, so I hate to think how much an entire round trip for a whole OneWheel would be. Justified the purchase by knowing I could rip out all its electronics and replace it with a VESC, which is an extreme way to go about ārepairā.
Itās more FutureMotions patents and related actions that annoy me. Thereās prior art for the one wheel itself, footpad sensors, and one wheel fenders, yet they sought out the patents regardless. I donāt double many could be invalidated, if you had the cash. Then there are the patents around suspension for one wheels which without a OneWheel product in existence seem more about stifling innovation than protecting IP. Then thereās the lawsuit around intercepting BMS-ESC comms, getting competitors thrown out of electronics expos, and so much more.
Iād really like to see more diversity in one wheels, like what we have with esk8. Just imagine if Toyota was the only car manufacturer.
Just on the tire thing. I know you already have tires, but craft and ride in the past have sent me XR tires for about $20-30US (canāt remember exactly cost) to NSW. They currently have a promotion (which may have ended in the past few days) offering free worldwide shipping and they have that a few times a year. I think shipping costs may have gone up since USPS stopped shipping to Australia and theyāve had to use UPS and FedEx
In my last build, I made the enclosure before the battery, and then predictably the battery didnāt fit without some workarounds. Was keen to avoid that this time around so had the battery made up before building the chassis which needs to contain the battery on a one wheel. Specs wise I wanted to go above what youād find in a OneWheel and settled on a Molicel p42a 12s3p pack, of course then the GT was announced with a 18s2p pack. Same number of cells, different layout .
Getting the pack built has been the easiest part of all this. Sent the following pic to @glyphiks .
It then sat in a box for six months, but at least I knew how big it was and could start designing the rest of the board around it. Got lucky and found a FlexiBMS Lite in Australia of all places, and finished up the pack.
The pack was already built when I decided that I needed a wider wheel. This meant the board had to be wider and the battery pack width would have never been a problem. In fact, I think a 12s4p would probably fit, just not sure where the BMS would go. Iām really not sure a one wheel would ever need a 12s4p, but damn Iām curious now
Usually Iād agree, but the board is very close to balanced right now. As in even with it turned off you could probably get it to balance. Really trying to avoid sticking more weight in the front where the battery is
Donāt think itās too much of a big deal if the front is heavier, youād just have to push the rear down with your foot. More thatās itās not ānormalā for them to sit that way.
Itās kind of important that the belt doesnāt skip in one wheel applications. Iāve skipped a HTD 5m belt before during heavy braking (and that was with two belts), so thought an upgrade to HTD 8m was in order.
Interestingly the specs for a 5m belt seem fine based on this chart (src). Assume motor makes 4kw, with an extremeāish load factor of two (4kw motor power * 2 load factor = 8kw design power), this still puts us just within the HTD5m band at 2500rpm. Just.
Gearing is a real problem with higher pitch belts/pulleys. The 22t HTD8m motor pulley looks roughly similar in size to the old 56t HTD5m wheel pulleys I ran on my esk8. Even for a kart wheel HTD8m pulleys above 60t get impractical (theyād hit the ground when turning sharp). Found a very nice looking pulley from Jones Racing Products in 49t that was originally intended for a quarter midget race car. Idea with this pulley was that it came in a variety of sizes which would allow be to change ratios in the future, however over the last few years I see theyāve discontinued these pulleys. There are other options, but nothing with the same off-the-shelf bolt pattern that will mount straight up.
Motor pulleys are much easier to come by, in this case Iām using a rather industrial taper lock pulley. I donāt think these are an option for HTD5m pulleys or smaller bores, but they do have one neat benefit. The bushing locks into the shaft when the two grub screws are tightened. To remove the pulley you take them both out and screw one in to the third hole that just pops the pulley off.
So with a large wheel diameter (approx 280mm), and not really being able to get much gear reduction I needed a low kv motor to keep the top speed in a reasonable range. Still wanted an excess of power though, so settled on an APS 80100 50kv, this should absorb as much power as the battery can throw at it. If we plug all these numbers into the esk8news calculator this works out to be a loaded top speed of 46km/h, and thatās just fine for now.
Iād like to have a smaller motor as I felt packaging an 80mm motor somewhere in a one wheel lead to compromises, more on that later. Just not sure if theyāll have the performance I want. Itād also be great to find a better/more available solution for the wheel pulley.
There are obviously other ways to do this. Chains would be off the shelf from kart stuff, give more reduction, and are quite a bit slimmer, but I ruled them out because I just find them too dirty. Gears would work, but with a bunch of extra complexity and need for precision. So belt it was.
Held together with some 3D printed parts, zip ties and tape. Just wanted to see it do its thing.
Itāll balance when turned off, but you obviously canāt 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 itās top speed. What EUCs do well is make that top speed so high that itās unlikely to be reached.
My gearing setup will give a top speed of 46km/h. If this works out ok Iād like to bump it up, just so Iāll never get near itās top speed.
VESC apparently does field weakening now, could be an option to bump up top speed.
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.
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