Speed vs. Range. Practical test results

General Discussion
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I’m going to be re-doing these tests once I get the new board up and running, because I’m interested how the pneumatics and the new FOC motor controller affect the numbers. I would believe that the FOC ESC is more efficient, but I don’t know how much yet, I want to get field test data first. The pneumatics should decrease efficiency a little bit, because they will most likely have more rolling resistance, but that is also dependent on the tire pressure…

Will have to see once I get the board up & running.

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Yeh, definately do this! We need more data like this - done in a decent and systematic (almost scientific :smiley: ) way…

I had a real problems and pity designing mountainboard build since at that time not that many users had emtbs and information was very limited…

I think only after a while I found out about average consumtion of 20wh/km for mountainboard pneumatic wheels and there is still not a clear reference at what speed such consumtion is achieved.

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Thanks for sharing, @SimosMCmuffin. These numbers are really interesting. Is your board powered by a single motor which drives both back wheels?

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[Album] The current iteration of my electric longboard - Album on Imgur
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On my skikes at high pressure (6 bars) I needed around double the energy per km than with kegels.

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Hmm… Maybe to test the rolling resistance between PU and pneumatics: Just roll off of a small ramp and just see how far you can roll. Of course remove belts to remove parasitic friction from the drivetrain.

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IF we find a constant value this way, we could tell people how to make their ramps to test rolling friction lol :smiley:

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No, I think the second axle is just for support and he does not use it…

Maybe @SimosMCmuffin can answer on this one - why your board has 2 axles and how did you exactly made it longer?

I dont see that u would use adapter which came with the motor…to somehow extend it…

I assume maybe u changed the whole axle to make it happen? Or is it just a bigger motor which came this way (dual axle) ? Looks like turnigy aerodrive motor to me, so im not sure they even sell dual axle versions :slight_smile:

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It’s just a longer single axle that I changed to from the shorter original one. The 3D-printed motor mount wasn’t stiff or sturdy enough to leave the motor just hanging off one side, so I decided to add a support bracket for it on the other side.

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hah pretty clever how u managed to do that with 2 axles and ‘get away’ with 3d printed mount! :smiley:

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I mean there is just a 1 single long axle that goes through the motor. No two axles.

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yeh sorry for the bad wording… I would say one long axle, which can mount 2 pulleys for example.

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Then you run into the differential problem with the differing wheel speeds when turning. I did test his in the very beginning, mounting 2 pulleys on a single axle and both of them to the wheels, but it wouldn’t had worked out for very long due to the aforementioned differential problem.

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yeh I know, some sort of freewheel design is needed for this.

I think ive seen CarvOn have demonstrating something similar. Not even sure how they made it work.

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Hi Simon :wave

Could you please elaborate on this? Specifically about the wheel scrub you had with the locked rear. Under power, did it fight back and the rear made the front push when you turned sharp, or what?

The world wants to know.

Oh, and that’s a really nice build! And nice work on the range testing, my head hurts now…too much maths for me.

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I never went as far as to test it under power, because it did not feel nice even under dummy setup with an un-powered motor axle connected to both wheels. Regardless of speed, either one of the wheels will skip and skitter when turning and the worse it becomes the tighter the turn. It will also send a lot of reverse torque back to the motor, stressing the axle.

So unfortunately I can only speculate what it would have been like to test under power, but I did not feel like it would have been worth it according to my personal testing.

This video can give you some idea of the pros and cons associated with a locked diff

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Again. A car has 4x tighter turning radius than a longboard. The equivalent car would have a 100ft turn radius

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Fair enough.

All I can say that I did not personally find the idea to be worthwhile to keep testing further based on my short unpowered tests. I will absolutely admit that due to the shortness of my testing and not running it under power, it might have given me the wrong impression of how it would have turned out.

So if someones wants to go for… Go for it and share the results, both the good and the bad.

And also, in my setup the limiting performance factor is not the lack of grip with the tires, but rather the lack of motor torque, so this wouldn’t really help my setup perform better.

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Knipsel
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Here you go I hope I could help. Ask if you want to know something.

BTW: you shouldn’t think that if you have 10000watts at your disposal that you will go fast. You should consider KV of the motor. And other things. But this will give you a good estimate how much power you need to go a certain speed. Like if you need 1000watts going 45 km/h you need a double setup. Because at these speeds the rolling resistance will become relevant. And you’ll have losses.