Trex 600 pinion question

[anthony7820]

My current setup is a Neu 1912H/1Y with a Jive 80HV on 10s.

Currently I am running a Trex 600 helical main gear with a 13t pinion and getting about 2200 in the beginning of the flight. Throughout the flight the rpm drops and it seems like the tail gets stuck in some hard maneuvers.

I was wanting to go to a 14t pinion but I cannot seem to find any 6 mm helical pinions, it would give me about 2420rpm in the beginning of the flight, and I'm assuming the tail would have more power also.

I found a 15t 6mm helical pinion, it would give me 2585rpm in the beginning of the flight, but I'm wondering if this will be to many amps for the motor esc and helicopter.

I am also running a BLS 9256 tail servo.

Any help would be great, Thanks!

[Andy01]

If I have got the right motor kV at 825kV and the right main gear teeth at 188T, I don't think you will be getting 2200rpm for very long;

825 x 37 x 0.9 x 13T / 188T = 1900rpm at 100% throttle.

Even with a fresh lipo at 4.0V (and it does not stay above 4.0V per cell very long - like seconds);

825 x 40 x 0.9 x 13T / 188T = 2053rpm

At a full 4.2V per cell it would be 2156rpm.

The only way you will get more than this is by having better than 90% efficiency on the motor. I think your headspeed calcs may be a little optimistic . Better to work on what you would get at the end of a flight rather than the first few seconds.

If you were planning to govern, which would avoid the speed drop during the flight), you could only govern around 1900rpm with this setup.

With a 15T, you could govern to around 2200rpm, which would be ideal. Your ESC should be able to govern very nicely - use it

I think your servo may be a S9256, not a BLS 9256. The BLS are the newer brushless servos and the 251 or 254 have slightly more torque than your 9256, but it should still be up to it on a 600.

Colin

[anthony7820]

Thanks, and the servo is a BLS 9256.

I'll go with the 15t pinion and govern at 2200rpm

[Andy01]

Originally Posted by anthony7820

Thanks, and the servo is a BLS 9256.

Sorry about that - I could not find a BLS servo with a 4 digit number on the Futaba site;

http://www.futaba-rc.com/servos/brushless.html

But I did find a s9256, but digital, not brushless (second from the bottom);

http://www.futaba-rc.com/servos/digital.html

I must have missed it somewhere. Sorry, I am assuming it is a Futaba servo, which may also be incorrect.

Colin