Gear Drive Questions

[Propjockey]

How do you figure prop size when using a gear drive?

Is there a general formula to use? (X motor + Y reduction = Z prop)

 

[forresterace]

PJ

Not that I've ever been aware of (formula for prop size). I've always found it to be a matter of experience and testing. Basically it pays to get a "ballpark" recommendation from someone to start from and then testrun using runtime and motor heat as your indicator.

 

[Propjockey]

As always...Thanks, Doug!

Soooo...any recommendations?

I have an Epic 13 turn on 6 cells and a trick V937/3. What gear ratio should go between 'em for starters?

 

[forresterace]

PJ

I doubt that the prop will work. I would suggest starting somewhere around 1.8/1 and maybe giving an X642 or X445 a try. That's a good choice of motor wind. That will also work for killer speed on 8 cells, 2/1 ratio and the X642 for openers.

 

[RBidwell]

I agree with Doug. That prop is a SAW prop and will burn up that motor for sure.

 

[sjslhill]

I agree with Doug. That prop is a SAW prop and will burn up that motor for sure.

Hum, not sure I agree with.....I use to run a 2137 on 4 cells, 1.950 ratio, 10 turn D4.

 

[Propjockey]

More test results......

With a gear ratio of 1.85 to 1, I was able to spin up a Props-4-U Octura 1938.

A bit more speed than direct drive and a smaller prop, but the big difference was run time...almost double!

Now all I need is a new hull, RCHydros Penguin, and more cells!