I made an Indefatigable hull from Ralph Coles' mold this week and am wondering what people use for propulsion in the similar Invincible Class BCs, which are only 2" shorter and a couple of pounds lighter. The Indefatigable won't be much heavier than my 3.5 unit armoured cruiser HMS Minotaur that uses a pair of Mabuchi 360 motors and has the same maximum speed (26s/100'), but I'm thinking of trying a Battlers Connection 2 shaft output gearbox with a single Mabuchi 500 motor. The output shafts are 1 9/16" apart so should work in Indefatigable with props up to 30 mm (~1.2") diameter. I use Rivabo and Raboesch metric props so can vary the prop size and blade number (from 3-5) to fine tune speed. I'm a little concerned that the Mabuchi 500 might be too powerful even with 2.5/1 reduction gears. Has any one had experience with that dual output drive in an Invincible, and what drive system is most often used?
Bob, I think you should make that gear system and 500 motor work. I am planning on that configuration for a future VDT project. I will be very interested in your doing all the hard work form me.
My I-Boat runs 1.25" four blade Prop Shop Kort props. With 550 Johnson motors mounted to Traxxas gear boxes. I think it's at speed with 14 tooth pinion gears, maybe 15s, and the white gears on the shafts are 28(?) tooth. It has drag disk at 1 or 1.25". Excellent start/stop and turning.
Thanks Bob, Looks like I'll have to order a BC dual output shaft unit and see if a single 500 or 550 provides enough power to get Indefatigable up to speed. I doubt if it'll provide enough power to drive Ralph Coles' Seydlitz which is 1/3 heavier in displacement and a faster model. He molded the Seydlitz hull with the shaft locations included and the inner shafts are exactly the right distance apart to use the BC gear drive. However, the shafts are too close to use a pair of 500s and gearboxes side by side. If necessary they can be staggered using a long universal joint to bypass the aft motor.
Invincible should work fine with a single 550, I ran my Invincible with a single 550 geared to two shafts for a couple of years. Was a Titan Marine @ 12 volts, geared down about 2 to 1, driving 1.2" props, I quit using that boat in 2011. Nowadays I would recommend about 1.4" diameter props geared the same way (1 motor/2 shafts) and a beefy outrunner brushless with about the same dimentions as a 550 and about 1200-1400 kV.
I built HMS Courageous with a single Force 545 'low drain' 6V motor running a 2.5/1 MFA belt drive to two shafts via a Dumas gear set and with 35mm (~ 1.4") 3-bladed props. It exceeded 24 sec/100' until drag props were installed. I've found an unused Force 545 so with BC 2.5/1 reduction gears and 30mm 4-bladed or 5-bladed props Indefatigable should be able to reach 26 sec/100' speed. It's surprising that although the Courageous model was nearly 17" than Indefatigable their displacements are about the same.
