zagibond

Dr Kiwi or anyone, please help!
I am running an Axi 2212/34 with Kokam 3cell 1500mAh batteries.
I am only developing 17.5 ounces of thrust with APC 1260 props.
On initial WOT I see about 19.5 but it quickly settles down to 17.5. on a fully charged battery.
I never see more than 9.5 Amps of current draw.
I am running a Castle Creations Phoenix 25.

PortCityFlyer

My Feedback: (1)

I ran that combination with my amp meter and was pulling 11.8 amps. Airplane did not perform as well as it does with APc 11 x 4.7.

zagibond

I am at 6000 feet elevation. Wonder if that is the problem.

zagibond

I think I may have answered my own question.
I used a motor calc and it should be able to theoretically produce 26 ounces at almost 20 AMPS with a 1260.
an 1146 should get around 20 at 11Amps
I would guess that my speed control has the max Amps set at 10??
I am ordering a USB programmer today and we will see!!!

Matt Kirsch

My Feedback: (21)

It's the altitude that's the problem. Speed controllers don't "limit Amps." They can't. Amps are determined by the characteristics of the motor, the voltage from the battery, and the propeller load. The ESC will either handle it, or it will burn out.

The thrust measurements you're trying to live up to were taken at "normal" elevations. At 6000 feet, the air is much thinner, and the propeller can't get the same kind of "bite." Therefore, less thrust, and lower Amps. You can mitigate this by using a larger-than-recommended propeller, but to find the right one, you have to experiment a bit. Increase diameter and/or pitch, that's for sure.

zagibond

Thanks Matt,

You are right. I replaced the APC with a good old orange GWS 1260. I pulled 20.5 ounces at 11.2 Amps and the Voltage had dropped to 9.8 on my Kokam 1500 3cell.

I was a bit surprised because I always thought that the APC were better props.

I am looking for thrust, not speed so I might look for a 13 with a lower pitch.

I should really just try to lighten my plane!!

rmh

You might find that you are caught in a strange loop-
Thrust - for hovering will be about the same -- if the amp draw is about the same .
I ran this little test on my thrust meter -- which is a Whatt meter reading power and a OZ scale showing prop thrust.
At our altitude , 4500 ft - the pitch requirements are much greater than the flatlanders .

We have thin air - but then, who want's fat air?

zagibond

I wish I could hover at 12.5 ounces, try 15!!!
I wonder whether diameter or pitch overcomes thin air.
Doesn't really matter because I don't think they make a 12 inch with more than a 60 pitch.

Nice setup. I have a similar one but not as tidy.
Is 9.8 V an acceptable Voltage at 11 AMPS from a fully charged 3 cell Lipo? (1500 mAh Kokams)
Where do you set your LVC. The instructions with the Phoenix recommend 6, but that seems dangerously low.
I usually stop flying due to performance drop when I have used just over 1000mA (according to my Triton)
I have my LVC set at 9, so I must be pretty close to that level under full throttle.