# How to go from rpm to hp or W.

1. Oct 7, 2011

### boyongo

Im trying to get the Hp or W for the O.S 61FX RC airplane motor that has a propeller size 13x6 that give 10400rpm. The reason for this is to know the max speed that it can obtain discarding the weight and everything.

2. Oct 7, 2011

### rcgldr

The propeller has a 6 inch "pitch". At 10,400 rpm that translates into 86.67 feet / second or 59.1 mph in a no load situation. Actual max speed of the rc model will be much less.

3. Oct 7, 2011

### Staff: Mentor

Can't you look it up on OS's website? Calculating will be inexact...

4. Oct 7, 2011

### boyongo

Just to be sure @ rcgldr we are talking about forward speed (velocity that the airplane is going to be traveling without any load and discarding the weight of the plane)?

5. Oct 7, 2011

### rcgldr

It would be better to say that if the plane were in a steep or vertical dive (and could achieve 59 mph speed with no power in a dive), that would be the speed where the prop would not experience a forward or backward load (only a torque load).