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Old 07-24-2014, 09:36 AM   #1
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Default Which is faster, 900kv motor on 8s or 700kv motor on 10s?

40mm can motors for a 1/8 buggy for speed runs only!

Which is faster, 900kv motor on 8s or 700kv motor on 10s?

Honest opinion's

Both motor's are the same size but one is 900kv 80A 37V used on 8s and the other is a 700kv 80A 50V used on 10s lipo. Don't worry about esc...she's 12s capable!

What will be your opinion's?

My opinion is that the 700kv on 10s with taller gearing will be more faster?
Wrong right? No idea?

Thanks!

I know it's irrelevant but someone uses 12s with 75T pinions on his rides!
So this is not an astronomical question for rc cars build for speed...hey, for years helis/planes & boats are using plus 8s lipos territory :P
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Old 07-24-2014, 11:45 AM   #2
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900kv on 10s.
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Old 07-24-2014, 02:20 PM   #3
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The math!

8s peak voltage - 33.6V
10s peak voltage - 42.0V

while 900kv w/ 10s would be the fastest, the motor isnt rated for that (but when has that stopped us before?

RPMS-

900 * 33.6 (8s) = 30240 rpms (peak)
700 * 42 (10s) = 29400 rpms (peak)
900 * 42 (10s) = 37800 rpms (peak)(because why not? We are here)

The 900kv will be slightly faster on 8s than the 700 on 10s but with the additional weight of a 10s

An alternative would be a 9s setup and the 900kv motor as you would be right at the max voltage of 37 (37.8). This would give you a few more rpms and a higher voltage setup for better efficiency.
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Old 07-24-2014, 04:31 PM   #4
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Hum... that keept me thinking...

The 700kv motor on 10s will be slower then the 900kv motor on 8s?

Well at least in theory, but in real world where weight of everything counts torque wins and can fit a higher pinion to compensate the 700kv to 900kv?

Right? Wrong.. ideas!?

One thing is sure... i am not going to reach just one speed pass... i want to empty the lipo pack doing speed runs safe with no heat issues!

Quote:
Originally Posted by mkiiina View Post
The math!

8s peak voltage - 33.6V
10s peak voltage - 42.0V

while 900kv w/ 10s would be the fastest, the motor isnt rated for that (but when has that stopped us before?

RPMS-

900 * 33.6 (8s) = 30240 rpms (peak)
700 * 42 (10s) = 29400 rpms (peak)
900 * 42 (10s) = 37800 rpms (peak)(because why not? We are here)

The 900kv will be slightly faster on 8s than the 700 on 10s but with the additional weight of a 10s

An alternative would be a 9s setup and the 900kv motor as you would be right at the max voltage of 37 (37.8). This would give you a few more rpms and a higher voltage setup for better efficiency.
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