wesley335

Hello,

I am building an autonomous GPS guided catamaran (approx 3 ft in length). I am new to RC boats and I need some help with determining what drive system components I need.

The motor and drive system will mount inside the hull and exit through the stern (traditional rc boat setup).

I currently have (2) 4000 RPM Brushed motors for the left and right hulls. The motors have a 4mm shaft.

I am looking for left and right propellers (~50mm) to drive the boat. Along with the propellers, can someone suggest the components I need. Does anyone make a kit with all the items I need? (Basically suggest all the items I will need for the drive system besides the motors).

Any help will be greatly appreciated.

Thanks!

mfr02

A lot depends on the performance required (speed and run time), then there is the shape of the hulls etc.
A rule of thumb for direct drive is that usually works is that the prop diameter should not exceed the motor can diameter, and the prop should not have more blades than the motor has poles. There are plenty of prop suppliers around, these guys http://www.prop-shop.co.uk/ have a solid reputation. You will need a shaft for each motor (you know what length you need since its your boat). The shaft usually comes with an outer sleeve which carries bearings. Then a coupler to join the shaft to the motor. These are usually in three parts, a bushing at each end to match the prop shaft and motor shaft respectively, and a universal joint. Going a bit up market, you get two universals and a center coupler. This takes mor room but makes for easier alignment.
Commonly, the prop lives under the stern, preferably in an area of clean water flow. I have seen a few attempts where the water effectively had to make a couple of sharp turns before it got to the prop - never satisfactory.
Then you need to control the motors, probably an ESC for each. You need to know the voltage that the battery will supply, and the current that your motors will draw under load. How you hook them up to your GPS is up to you, but you will probably need something like an Arduino to read from the GPS and generate RC standard control pulses for the benefit of the ESCs.