Holy, forgot how massive this thing is!
How big are your wheels?
@tomiboi is using 11" 60v hub motors for his 3sk8 project. supose to be good up to 45mph!
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Better question is, does front wheel power/braking torque affect the steering mechanism? For example if braking while turning, can the braking force push the steering further over and possibly induce speed wobbles?
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The speedboard seems to shrink in peoples’ minds. I think that’s why I get a lot of “that is way overpriced” comments. When you see it in person, or at least in reference to a known board, there’s an “aha” moment, when you realize how much you get for your money.
The tires are 10.3" diameter x 3" wide, on 4" hubs. Massive contact patch of DOT-approved rubber. It really is a hybrid of a motorcycle and a skateboard.
I’ve seen hubs like those, I should make a prototype with them. They are 6 kg (13.2 lbs) each though. Two of those weigh more than my entire speedboard prototype (26 lbs). Plus, they’re only rated for 1600 watts. It may be possible to run them higher, but I doubt they’ll match the 7000 watt output of my single 80100 motor.
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There is no rake in the steering mechanism, so acceleration & braking force should be isolated, but I haven’t tested it out yet. I’ll look into the geometry more. Interestingly, if there is some impact on steering, it could be used to fine-tune turning radius at a fixed lean angle mid-turn. The geometry could be tuned so that braking tightens the turning radius and acceleration opens it up. So many variables to play with!
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They just released that motor with a 3000w rating 
https://www.aliexpress.com/item/4000278016177.html?spm=a2g0s.9042311.0.0.60954c4dgZuYCr
I kind of dig the gold rims. Also there are several tire options.
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I think the power rating of most brushless hobby motors are “technically true but very exaggerated”. Similar to hobby lipo discharge rating exaggerations.
Because how does a “tiny” 80100 motor output more power than a 13lb 11" hub motor?
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Power is a function of torque x rpm. The 13 lb hub motor has a rim diameter of 6.5" and a rotor diameter of ~4". With a claimed top speed of 65 kmh (40 mph) at 60V the motor is spinning at 1231 rpm, so it is ~20 kV. To make a motor with 20 kV you need ~7x more turns of wire as you would for a motor with 130 kV. This means the wire has to be 1/7 as thick, allowing significantly less continuous current, and therefore a lower power output.
While a 80100 motor seems “tiny” compared to a 13 lb hub motor, the rotor diameter is not much smaller at 3.15". It has the advantage of using much thicker copper wire, allowing a 148A continuous current, and spinning to 7800 rpm at the same 60V. This rpm is then geared down 4.375:1 to produce the same 40 mph top speed.
While you can certainly push more current into a hub motor to temporarily increase the power, the issue is removing heat from the hub. This is the main limitation with hub motors. The waste heat has to travel through the magnets and out through the rim, and through the side walls to escape.
For the 80100 motor, by spinning at 7800 rpm there is a ton of air moving around and through the motor, dissipating waste heat more effectively compared to the hub motor at 1231 rpm.
This is ignoring the weight penalty. I’ll have to add up the numbers for a direct comparison, because I have the drivetrain to account for, but the running gear definitely weights significantly less than 13 lbs.
Will I make a hub motor-powered speedboard? Of course. There is clearly a market. Just don’t expect it to have the same performance as a geared down drivetrain. It’ll still be plenty fun though.
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Wait, what are the benefits of a hub motor speedboard? Just 2 wheel drive? Can’t imagine it to be that much cheaper…
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It’s for people who want a zero-maintenance board. I don’t think it will be much cheaper, if at all. Some people hate chains & belts, and I can understand why. I just like max power.
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Just want to say you have clearly thought about hub motors 100x more than I have. I think all the points you raise are very good, I totally agree a single large belt drive has so many advantages over hub motors even if requiring slightly more maintenance.
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oh wow, this actually makes so much sense. Thanks for the insight
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Yeah the physics of electric motors is simple, but the thermodynamics are very complex. The hub motor option is super obvious at first, but in practice there are a ton of tradeoffs.
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Or… Belt drive rear and hub drive front for ultimate performance.
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Honestly if the motor is large enough on the rear I don’t think the front needs to be driven at all, but having a hub motor on the front exclusively for braking could make a massive difference. Something small and light, which’ll stay cool most of the time to be ready to absorb a bunch of energy when stopping.
P.S. - The new website is up, speedboard.com, reserve a board for a $500 refundable deposit to lock in $1999 + shipping price until Jan 31. Price jumps to $2099 Feb 1, and will continue to jump up $100 until it hits the final retail price of $2499.
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Yeah, I think because people are used to the 6" wheel size and doesn’t realize its actually 10". It looked similar to this in my mind: (I just shrunk it to match the wheel sizes)
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Braking is really what I was thinking of. Maybe even some servo driven disc brake system, without the weight of a motor. Like a self-adjusting, servo driven hydraulic system on PWM control.
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Yeah I want to test that out on the race boards. It will probably be easier to just make a hub motor than try and make a usable electronic braking system, it took car manufacturers a few iterations to get that to work. But for hauling down from 80+ mph a disk brake is really the only way to go.
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Agreed. Hub motor version would be better for offroad too with traction control. Disc probably better for street racing
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I’ve been sketching this out myself. Ppm driver.
A servo to actuator that depresses a piston, attached to a house,. That drives a mountain bike caliper
I’m receiving serial number #1 so and David knows I want boss standoffs door front brake if possible.
Will I follow through? Idk. Is it necessary? IDK. I only got 15mph in the 30 seconds of riding the speedboard
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