…or more wheels…
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Thats true, but my whole project is planned around those large tires.
2 hubs per wheel— 12 motors total
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Thank you very much, it seems I need to have a look at rewinding the motors. Both gear boxes and hotter motors are not an option.
Regarding the low RPM control, I am using the hall sensors (they get recognised and work apparently fine) but for some reason starting is only possible above a certain ERPM.
Re-winding, you’ll get the same heat for the same torque
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The Maximum RPM in VESC Tool doesn’t do what you think it does. It does not prevent the motor from spinning faster. (only prevents power/brake while spinning faster)
Try setting Maximum Duty Cycle instead.
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So rewinding can not achieve what a gear box does as in reducing speed and increasing torque at the same power and power losses?
Rewinding for more torque per amp will increase the resistance such that the heat per Newton meter stays the same.
Rewinding at the same copper fill won’t change the KM motor constant, which is the torque per the square root of the resistance heating.
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If you add more turns, the controller will run cooler for the same torque but the motor heating will stay the same.
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Thank you, more reading to be done. And in all probability I need to find a larger motor with more room for copper…
Probably best bet would be a mechanical reduction with gears or belts or chains.
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I am afraid so… I wanted to avoid building gearboxes as it messes with my suspension arms
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You could find a way to mount a motor similar to this beside the wheels for more torque:
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Could get controllers that put out more amps
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If u can get to the magnet wires of the motor (sometimes on cheaper motors the three motor leads are the same magnet wire) you could find the starts and ends of each strand and reterminate them to wye and drop the kv and amount amps needed for torque, assuming they’re terminated delta now which is very likely.
Choice 1 is easiest
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Yes you may be able to briefly exceed the motor’s advertised current limit.
Another option is buy a few of these:
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Hoverboard motors would be ideal for this. They are made for low speed high torque.
Depending on how heavy your vehicel is going to be 6 of the small hubs might be totaly fine. Even one of them is enough for low speed cruising for a human so 6 will likely be fine for something light even if the gearing is bad.
12A seems kind of low for a maximum rating I guess they should be fine with a short 20-30A burst to get them going.
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The motors are actually terminated in wye, I took one apart to check this.
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Thank you very much for the suggestion, I think you are right, so far I was concentrating on finding hub motors much smaller than the inner diameter of my tires. I did some measuring, I could get away with a hub motor with an outer diameter of max 83 mm, this will still be small enough to have a few millimetres to spare for a 3D printed rim which fits my tires. Hover board motors are unfortunately of such a large diameter that they will probably not fit. I used all my paint skills to make a drawing to illustrate:
This is a side view of my current 3D printed rims with the two measurements indicating the max size of a possible hub motor. The red lines are the rubber of the tires.
I could fit a hub motor reaching trough on both sides (green rectangle) which must not be larger than 83 mm in diameter or I could fit a hub motor completely inside of the tire which must be quite narrow (not more than 44 mm) and be less than 150 mm I outer diameter. Marked with the pink rectangle.
I think I will try to find something within those limits, 5" scooter hub motors look quite promising, though it is not so easy to find drawings or measurements on the various vendor pages.
The rover will be not very heavy say 15 - 20 kg as a maximum. Its just for cruising and crawling about a bit and maybe using as a snow plough or pulling sledges in winter. So I completely agree, 6 motors with let’s say 3-5 Nm torque each should work nicely.
Using VESC and hall sensors should give me slowest speed control for crawling, at least this was my impression.
