FMS V7.5 P-51 BBD: The 540 Power Plant! - RC Groups
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Feb 09, 2013, 02:44 PM
"Auntie Samantha"
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FMS V7.5 P-51 BBD: The 540 Power Plant!

The Big Beautiful Doll's Power Plant!

This is my run-up test and installation of the FMS/G&C 4250-540kv motor.

G&C 4250 540kv Test (4 min 11 sec)

As you could see in the vid, the G&C 4250-540kv produced 929W at 63A off of a 4S 5000 30C lipo. I also ran a test (no vid) using a 5S 4000 30C lipo and got 1220W at 72A, so with a 5S this 540 will eat up the oem 65A ESC in short time depending on flying style. I will probably move up to a 85A + ESC if I choose to run a 5S lipo.

Prior to re-installing the motor back in the plane, I took the time to do a little detailing in the engine compartment. Once again FMS has done a great job in making sure there is adequate ventilation thru the engine compartment, so there's very little, if anything to do! I just repainted it with MM Green Zinc Chromate , and that was it! Besides the nice wide open lower chin scoop, FMS has made the two side ventilation screens now functional. They are ducted into the engine compartment and help add to the ventilation.

I am also pleased with the new engine mount configuration as it appears the circular plastic mount is well secured in the foam. That and the motor X mount, the whole assembly appears to be rock solid. There were a couple of changes I did make thou.
1. There were 4mm nuts used as spacers on the 3mm philips head mounting screws. I felt this created to much spacing between the spinner and the cowl for my liking so I used a couple of flat washers instead.
2. I don't like using philips head screws in this app. so I replaced the 3mm philips with #4 x 3/4" hex head screws.

Note: The four 4mm spacer nuts were equal in thickness so I assume the mount itself has the offset thrust angles already built in. That said, I did notice a very slight difference in the spacing between the spinner and the cowl, so when I installed the 2 washers I just put them on the 2 screws on the port side of the X mount. That made the spacing perfect!

*TIP* Before mounting the motor, check to make sure you have the 3 motor leads orientated to the correct leads on the ESC. I had to switch two (yellow to black) so I could achieve the correct prop rotation.

Once I got the motor secured in the engine compartment I mounted my perfectly balanced 4-blade prop assembly "FMS V7.5 P-51 BBD: Dyno Tuning the Prop!", installed the cone, and I was good to go!
Last edited by Sandancer; Apr 14, 2013 at 05:34 PM.
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