# What's the smallest 3-blade propeller for this motor? [closed]

I've got a 15470 brushless 35kw motor from China
How do I find the smallest 3-blade propeller I can use for this motor?

Here are it's specs,

Max Power: 35KW
Max Amp: 400A
Max RPM: 8500
Max Volt: 120v
Torque: 75Nm
Resistance: .94

I've looked into eCalc but it's for determining power / thrust, etc and not finding prop size.
Any help would be appreciated!

• "Because 120 * 35 our maximum RPM would be 4,200" - Come again? You can't get the maximum RPM by multiplying the voltage by the power. Commented May 9, 2019 at 20:35
• Since you're looking for "smallest prop", how much thrust do you need out of it and how much torque can your motor supply at 4200 rpm? Commented May 9, 2019 at 21:36
• @DanPichelman I've added more detail to the question, the manufacturer recommends a 36-40 inch 2-blade propeller, so I was wondering how to calculate an equivalent 3-blade propeller (or do I just take off an inch as is the "rule of thumb"?) Commented May 9, 2019 at 23:06
• Seems like the pitch of the propeller would matter quite a bit here as well.
– Ralph J
Commented May 10, 2019 at 5:42
• I seriously doubt that thing is rated for life safety. You would need to use it in a jurisdiction that has lax safety regs. Commented May 11, 2019 at 14:50