We are designing a new Fixed Wing plane, all composite again, but this time with no landing gear, using a single peg bungy launch, with a parachute recovery. As w are fitting this Gimbal to this plane, we want the nose clear of motors and props. I wish to use a tail boom mounted co-axial prop, but do not approve of the possible options around - noisy and short lived gears, or Gimler belt and toothed gears, etc.All a bit complex, and awkward to locate and then house in the fuselage.
The very Nice Gimbal - Day and Thermal IR Night cameras, 640x480 Pixels. Fully Gyro Stablised. Serial port to drive and control.
So, I decided to modify a few Brushless motors and make then truly co-axial, with integrated folding prop mount, really beefy bearings, and a nice through hole for tail servo leads and lighting.
I used two HACKER Motors, A40 series, 50amp constant, one of 410kv to spind a 17x15 prop, and one of 610kv to spin a 16x8 prop, and an AXI 4120 series, also 50 amp, of 465kv for a 17x13 prop. Flight test will show which of these is best for our application.
How did I do it? Well, pictures are the best, but essentially I cut of the outrunner bell ends, machine out the inner Aluminium ball race holder, and ream out the hole to 10mm. Then I make a new bell housing, with double beefy bearings at one end, and a folding prop holder. All bonded together with locktite.
The end results with regard to weights -
The weights are done using a standard motor, fitted with prop holder, fuselage mounting, etc, and then compared to the final weight of a modified motor.
Motor Standard weight Modified weight
AXI-4120-20 465kv 345g 342g
Hacker A40-12S-V2-610kv 240g 243g
Hacker A40-12S-V2-410kv 317g 310g
As seen, there is no penalty in weight for this mod, even with a 110mm long 10mm diameter stainless steel tube through the motor centers...Through this tube is passed all the wiring for fuse to tail connections. The tube is then fitted to a holder on the fuselage, and the tubular tail boom ( actually an ALIGN 'copter tail boom - 20mm diameter) fits on the other end of the motor shaft, with a small aluminium bushing ( 4grams...)