How do you calculate volts = rpms?

[britscoot]

For example i have 2 motors i'm comparing to run on 5s.
Castle 1515 1y 2200kv and a Castle 1518 1y 1800kv.
The 1518 is longer and has more cogging.
Which one is going to perform better (speed) in a 30" hydro?

sorry for all the questions.

cheers

[Brushless55]

The 2200kv motor on 5s is 40,700rpm!
and the 1800kv motor on 5s is 33,300rpm, that's much better imo

the 1515 is more of a 4s motor

2200kv x 18.5volts = 40,700rpm

[ERCM]

kv x volts will give you rpm. 5s is 18.5 volts x 1800 kv = 33300 rpm

[ERCM]

He said it better lol.

[britscoot]

I have run the 2200kv motor on 5s and it comes in warm except the lipo gets too hot for my liking.
It's very fast.
Will i be able to achieve the same speeds with the 1800 motor with different props?
What is the advantage of running the 1800 motor?

[britscoot]

what i meant to say is that i'm using a H6 prop on the 2200,so could i use an H7 with the 1800.
If that makes sense....lol

[Brushless55]

I have run the 2200kv motor on 5s and it comes in warm except the lipo gets too hot for my liking.
It's very fast.
Will i be able to achieve the same speeds with the 1800 motor with different props?
What is the advantage of running the 1800 motor?

The bigger motor has more torque so it will swing the bigger prop easier and possibly keep the packs from getting so hot
I say give it a try and see how it performes for you
and you may want to try 6s just for kicks on that motor
Is this in the FE30?

[britscoot]

When you say bigger motor,do you mean the 1800 will swing bigger props?
And yes this is the FE30.Doing mid to upper 60's on the 2200/5s.
So the 1800 on 6s will be crazy fast?

[teach]

That's still 40k rpm.

[Brushless55]

When you say bigger motor,do you mean the 1800 will swing bigger props?
And yes this is the FE30.Doing mid to upper 60's on the 2200/5s.
So the 1800 on 6s will be crazy fast?

That's sweet getting your FE30 to those speeds!
yep you should be able to swing the bigger prop on 5s with no issues, and running 6s for a SAW type run