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Brian Whatcott

On Tue, 19 Jun 2007 07:21:42 -0700, wrote:

Folks,

1. Where is the actual drive motor residing?...

2. I am looking for a used DC Motor controller. I intend to buy a
small trolling motor with small (9-11 lbs torque). Can you advise,
what specifications should the control have (Amps). Will a 15 AMP
controller do?

3. I am sure controllers for marine applications are much more robust
and built to last. Can you please suggest a good source to buy a used
controller.

Thanks so much.

Ash

1) The motor sits in the lower unit.

2) Torque is a unit of force times its tangential distance from a
pivot.
Instead, let's see what current 11 lb of force would take.
Power is easily worked from force times speed, but interestingly,
troll motor makers specify thrust (force) of a fixed troll motor.
We will suppose this moves water at 3 mph.

11 lb = 11/2.2 X 9.8 newtons = 49N (in SI units)
3mph = 3 X 0.45 meters/second = 1.3 m/s
So force X distance = power:
And 49 X 1.3 watts = 64 watts (at 100% efficiency)
That would be 6 amps thereabouts at 12 volts.
Troll motors are often full on, or through a big dropper resistor
or off About 1 ohm at 20 watts rating for example for about half
speed.

Brian Whatcott Altus OK