Drive motors Naval Paddle Tug Diligent

[boater]

Any suggestions please.

My drive motors are escap geared motors. I bought them at a surplus sale at Bletchley Park about 10 years ago, very cheap ,about £2, and super efficient.
They drive a pair of "Glasgow" paddles and propel the tug at a nice speed  -  but the normal  ESC will not control them, its first touch on the control stick and we are at full speed.The total current consumption for both motors is 0.10amps on 8.4v flat out  and I am using two speed controllers for good turning.

I have been told I need a voltage controller and currently I have adapted 2 old Bobs boards by cutting the original tracks and fitting radio type resistors and this seems to work but it is very untidy with the moving wires under the deck.

Is it possible to make a neat ESC that will do the job.

[rpbidgood]

Hi,
    As a refugee from model car racing, I had a similar problem with my first Paddler - I used an expensive, high spec. car controller and ended up with two speeds :- on or off. I solved the problem by fitting a Microviper esc. from Mtroniks, which is designed for smaller model boats. The cost is about £20.
   I am currently building a smallish quarter wheeler, again with a small current draw, and have bought two esc's from Action Electronics which seem to do the job nicely. Drop them a line, they are a small, family business and very helpful. The prolific model boat designer, Glynn Guest has been extolling the virtues of Astec products for excellent slow speed control.

   What electronic speed controller were you using? What is your radio gear? Most modern esc's allow you to 'set them up' so that you get full control even with a basic radio transmitter ie. so that you only get full speed at full stick movement. Sophisticated transmitters have an EPA system (end point adjustment) which allows the user to limit the movement of a servo, or in this case the speed controller.

  Are you a member of a club? There is usually a wealth of knowledge and experience on tap there.

I am not an expert in this field, esc's work by 'chopping' the current to the motor - imagine the ramparts of a castle, the bits sticking up represent current being supplied to the motor, the lower bits are when the current is switched off - bear in mind that this is happening thousands of times a second. At low speed settings the current is only switched on for a relatively short time when compared to the off duration. (During my car racing days an esc. started playing up, it was working perfectly, except it was switching every few seconds - the result being the car would move forward for a few seconds, pause for a few moments and then move off again.) In an ideal world, a speed controller rated at say 50A should be able to control a motor drawing as little as (in your case) 0.1 A!, but apparently they can't.

Last thought, when I first came across this problem, I began to wonder if fitting a resistance in series with the motor might give me better control - in your case you might try sticking a 20 ohm resistor in the the positive feed to the motor,and if this doesn't work try 30,40, 50 ohms. This might not work, but it would do no harm - at 0.1 A a 20 ohm resistance would give 0.2W of heat. Why didn't I try this, well I was having a little trouble with the gearbox on the paddler and a lot of trouble with the alignment of the motor/pitman arms driving the wheel, I wanted an easy solution to the motor problem.

Hope this helps,

Keith.