RC Submarine 5.0 – magnetic coupling and propellers (4/10)

Next, we need to select the motors and propellers, and build a powertrain between them. Layout The plan is to have two propellers side-by-side at the rear. Differential thrust will be used for turning. The propellers should be as far apart as possible to make the submarine turn faster, but they shouldn’t extend beyond the hull diameter to prevent the blades from hitting rocks or weeds. Below is a sketch. Motors For the motors, I’ll choose the good old Lego Power Functions M-motor 8883. The reason for selecting this motor is the small size and low power consumption. Especially power is critical here because there will be only one Lego battery box (max 1 A) to power all the motors and a computer. The M-motor draws 0.06 A with no load and 0.60 A when stalled. Magnetic coupling For the magnetic coupling, I’ll choose the smaller ring built around the Lego 24-tooth gear 3648. This should minimize the strain on the motors, but it also limits how much torque we can transfer. The polarity of…