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Brushless inrunners?

@Daniel92104 brought it to my attention by mentioning the castle 2028 motors (I have one, and before doing any eboard research, my plan like daniel’s was to use one of castle’s motors), which are inrunners made for large scale rc cars. They really are beast motors, retailing at 200ish USD, but at 800kv for the lowest one, they just aren’t practical…

so does anyone know why there aren’t any brushless inrunners around the 150-300kv range?

I mean, it seems like the advantages would be great: more robust against debree because of a hard, stationary can…Possibility of an added fan or heatsink (like on the caste motors). splash proof design because (besides bearings…) it would be sealed (again, like castle motors which are claimed to be “waterproof” as long as you like replacing bearings).

here is a pic I found of a castle motor against a soda can:

That’s the motor used on the world’s fastest electric skateboard. 55mph I think he used 8s lipo’s.

an inrunner would totally be a more appropriate motor for a skateboard.

BUT (this is my theory only)

with an outrunner the heavy mass of the magnets is on the outer most part of the motor and as they are rotating they create a flywheel like effect which would produce more torque than that of a similar sized inrunner spinning only the armature.

does that make sense?


The bolt circle on that motor is the same as the inter most on the enertion motor and would interfere with the pully.

He had to kick up to 15mph before he could give the motor any juice and he burned up ESCs like crazy. Not sure he has set a record yet…Also not sure why he didn’t just use a 290kv 63mm outrunner @ 8s, with 105mm wheels, geared 17/32…Oh wait! that was one of my builds and it was faster than that.

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Yes it’s difference between top end power or low end torque.

don’t forget: power and torque aren’t mutually exclusive.
power is just calculated from torque and will increase with RPM. power just increase more than torque with RPM.
but you still have top end torque and bottom end power.

in fact… here’s a little diddly for you:
If you have an 208kv motor and a 6S battery, power and torque will be exactly the same.

Typically inrunners are used for higher rpm / lower torque applications so for the purpose of an e-board you’d probably need a high gearing ratio.
I’m not familiar with inrunners but I doubt you’ll find low kv values.

totally see what you’re saying @lowGuido and @psychotiller

thanks everyone for the info!

with two stage gearing reduction it could work!