I tried to use the longer shaft the machine shop made but the fit in the rear bearing was too loose and caused excessive vibration. The original motor shaft was reinstalled and testing continued.
The motor used is the RIMFIRE 65cc.
Battery is a 12s 1p (2-6 cell packs in series) GensAce 5300mah 45c.
ESC is a Castle 160HVF.
Gross weight is 28.5 pounds.
Prop is a Ramoser VarioProp 22.6 set at 14 inch pitch and 16 inch pitch.
The propeller is rated for 4800 rpm so the full power run at 14 in. pitch would cause excessive rpm when the prop unloads in the air.
Take off at 1/2 power and 4000 rpm would be adequate with a pitch speed at this rpm producing about 55mph. This plane will not exceed 45-50 mph with the gear extended so this is adequate take off and landing performance. Use of an on board camera and a GPS speed indicator recorded lift off at 24mph using 15 degrees of flap and up elevator trim (25%) mixed with flap causing an automatic lift off (not necessary to rotate), when flying speed is reached. Gear up top speed would be about 70 mph without allowing for prop unloading. Peak amps were 119.3, peak watts were 4510. rpm 4861.
The next test run with the prop pitch set at 16 inches dropped the peak rpm to 4200 leaving room to unload in the air. Pitch speed is the same 70mph but amps dropped to 87.8 and watts to 3525. The lower load at a higher pitch setting is an indication of prop airfoil stall at static full throttle. This happens with 2 blade props that have a pitch higher than 8 inches.
In the case of un-stalled in-flight full throttle prop loads you can expect dramatic increases in current and thrust at medium flight speed that tapers off as the P 51 accelerates and reaches top speed. My ESC records acceleration current at over 130amps at 70-80mph that decreases to 70-80amps at 115mph. My personal experience is that the Top Flite GS P 51 needs to have a never exceed (VNE) of 120mph or less. A glassed or reinforced airframe is capable of higher speeds but I will leave that level of performance to pilots who have the resources ($) to push speed limits.
Now that I have a set of performance parameters I am confidant that this electric power package will be reliable at the flying field as it is less load than the best previous prop used, the APC 26-15Electric which had a max current load of 165amps. It has taken me a full year and 70 flights to get to this point.
