The Drive Train
The name of the game is to make these props turn at the right speed!
This is the 4 x 550 motor configuration, two motors were speed controlled and the other was controlled via a 30A headlight relay by an 'overdrive' controller.
The original experimental gearbox
The newer gearbox had the same propshaft plate and a new bigger driveplate based on the second design but with the original motors replaced by 2 Mabuchi 550's and then two more 550 motors were fitted directly above the outer drive shafts. The gear ratio has gone back to the original Kyosho 36 and 24 tooth gears (1.5:1 ratio). I had to increase the battery to 12V 7AH to get reasonable operational life of around 10 minutes at full throttle.
Most impressive performance, the boat is now "running on the step" with only the aft 1/3 in the water
Gearbox number 1 had 32 Pitch 24 tooth gears on the motors and 36 tooth gears on the propshafts, with both motors in series across a 7.2Volt Nicad 1700mA battery and speed controller it gave reasonable performance, but we want awesome performance. Increasing the Battery to 12 Volt 3AH Lead Acid (6 Volts per motor) gave a lot more grunt but was turned off when smoke came from the motors, maybe not a fair test as the boat was held back in the pool and therefore the load on the props was very high. Also there were problems lining up the motors and meshing the gears so a design change was needed here. One interesting point that was not originally considered is the resonance of the Hull and the sound from the motors and three propshafts - sounds a bit like the real thing - bonus!
Gearbox II and three has the motor mounting holes perpendicular to the line between the propshafts and elongated in the same direction so that the motors can be adjusted for mesh. The motor gears were changed at one stage to 15 Tooth 32 Pitch gears giving a gear ratio of 2.4 to1 This seemed to give good battery life and very good performance but not there yet!
The second gears, these have been dumped in favour of the original 24 tooth gears fitted to the 550 motors..
The original motor spec.
I've had these motors a while!
Now that we have the triple speed controller and smaller scale sized propellers I am planning on a direct drive trial with each motor driving their own propshaft via some sort of universal joint. this means shortening the propshafts and mounting the motors directly on bulkhead 10. I am thinking three Graupner Speed600's!