Brushed motor turn count and speed

[RGM]

I have a Capra with the stock 35 turn 540 motor. I do not compete, just having fun. I want to slow the speed down by getting a new brushed motor with a higher turn count. Is the relationship between turns and speed linear? If I had a 40 turn and switched to a 20 turn, does the speed double? Likewise. if i went with a 80 turn, would my speed be cut in half?


I want to reduce my overall top speed to around 60% of the current top end. I am looking at something around 55 turns. Just want to make sure I get the correct motor. Any advice would be appreciated.

[HumboldtEF]

I think its more useful to think of this in terms of KV ratings which most brushed motors dont use. The reason being a 3 slot motor thats 35T vs a 5 slot motor thats 16T are the same speed where as KV is KV.

I would recommend checking out the chart that Holmes Hobbies put together: https://holmeshobbies.com/motor-recommendations

Personally I prefer a 5 slot brushed motor as they have a smoother startup at low speeds, 20T (5 slot) is what I would pick for brushed. I went with a 1800 KV revolver motor for my Capra, it has amazing low speed control. Skip to 1:30 https://www.youtube.com/watch?v=uoIIN1r82Gs
BTW Revolvers/outrunners are loud screachy motors unless you use the Holmes Hobbies ESC to silence it.


Going from a (3 slot) 27t to 55t on a 3S battery would be roughly 12400 RPM to 27280 RPM.
If you want to be 60% slower that would be 600 KV which isnt an off the shelf option, 1000KV is the slowest you're likely to find.
You can find a KV calculator here: https://www.rcdronegood.com/brushless-motor-kv-to-rpm/


You can also change the gearing, the pinion and spur gear is the best place to start though you can throw in underdrive portal gears too but thats not common it would be a last resort. BTW you want a smaller pinion gear to go slower but a larger spur gear to go slower. To use a larger spur gear you would likely need to leave off the spur gear cover on the transmission.

[ferp420]

the pinion gear would be a good place to start drop 2 teeth and see were your at

[RGM]

Originally Posted by HumboldtEF

I think its more useful to think of this in terms of KV ratings which most brushed motors dont use. The reason being a 3 slot motor thats 35T vs a 5 slot motor thats 16T are the same speed where as KV is KV.

I would recommend checking out the chart that Holmes Hobbies put together: https://holmeshobbies.com/motor-recommendations

Personally I prefer a 5 slot brushed motor as they have a smoother startup at low speeds, 20T (5 slot) is what I would pick for brushed. I went with a 1800 KV revolver motor for my Capra, it has amazing low speed control. Skip to 1:30 https://www.youtube.com/watch?v=uoIIN1r82Gs
BTW Revolvers/outrunners are loud screachy motors unless you use the Holmes Hobbies ESC to silence it.


Going from a (3 slot) 27t to 55t on a 3S battery would be roughly 12400 RPM to 27280 RPM.
If you want to be 60% slower that would be 600 KV which isnt an off the shelf option, 1000KV is the slowest you're likely to find.
You can find a KV calculator here: https://www.rcdronegood.com/brushless-motor-kv-to-rpm/


You can also change the gearing, the pinion and spur gear is the best place to start though you can throw in underdrive portal gears too but thats not common it would be a last resort. BTW you want a smaller pinion gear to go slower but a larger spur gear to go slower. To use a larger spur gear you would likely need to leave off the spur gear cover on the transmission.

Thanks for the detailed response. I was assuming this would be more complicated than I thought. You have got me going in the right direction.

[King Dork]

If using the stock Capra gearbox changing the spur isn’t an option. Some people have been able to fit a 10 tooth pinion maybe with some Dremel work (?). I’ve only been able to fit a 11 tooth but did change from a 2200kv motor to a 1800kv motor and it’s definitely better for both trailing (2200 was faster than I wanted), and crawling.