Flew my red nose P-51, NF 129 this evening after installing a 9x6 in place of the stock 8x6 prop that came with the plane. While the plane sounded like it was pulling more power in the blocks on the ground, it really didn't appear to get any more speed in the air than it did with the old 8x6 prop. (See prop picks)
The larger 9x6 GWS prop sure was noisy. It had the hollow muffler sound like a revved up little 4 cylinder car would have. Very odd sound. Flew nice though, almost the same as the old prop. It did get moving on its take-off role more quickly.
Did a 7 minute flight on my 1350 Mah 30A 3S Lipo, then i installed the 20A 1800 Mah 3S Lipo and flew for about 8 minutes.
Here is where I apparently made that rookie mistake. Put the plane back in the blocks to run it with the voltage buzzer installed (beeps when below 3.5 volts) to see what the battery flying time might be on the 1800Mah battery before cuttoff. I ran it in the blocks for almost an additional 6+ minutes going from 1/3 power to 2/3 power with occasional 100% power for 15 seconds at a time or so. Right at the 6 Minute mark I did another near full power advance, when suddenly----'POP'. Prop spools down and the smoke comes out of the nose between cowl and spinner.
motor is a 4100 KVA Inrunner geared down to 4.6 to 1 on the gearbox. It has an 8A continuous rating and a 13A burst. Been flying with it for 15 to 20 flights now. Only difference is the new prop. I have two theories and maybe you all can explain what happened:
1 I ran it too long in the blocks at power without the cooling airflow it may otherwise get during flight.....probably a No No.
OR
2 The larger diameter prop may not be generating enough air flow near the hub pulling air into the nose of the nacelle cooling the motor.