Sunday, July 7, 2013

Re: [Electric Boats] Re: Questions for a small electric motor.

 

On 08/07/13 08:05, dudevato wrote:
> I'd think anytime you mess with a gear box there will be 'loss' via friction, but I have to admit one gear in a car would not be the way to go.

Only 'cause the starting torque of a ICE engine is terrible. Electric
motors have full torque at start. A fixed reduction gear is often used
simply to match the final drive speed with the best speed for the motor.

On the big railways, the gear ratio is usually determined by the
target design speed - they work out the maximum RPM of the motor, the
RPM of the wheels at the target speed and then calculate the gear ratio.
(Final torque might be a consideration for a heavy hauler, but maximum
speed seems to be the primary input)

>
> And I can say without being embarrassed I know nothing about amps/ohm/volts but I'd sure think the makers of these 12 volt trolling motors would have done quite a bit of research before putting something into production, as far as endurance of the motor, 'efficient use of battery power, bearings, etc. But if you want to go faster then anyone else will know what to do.

> I've read On Line there is an after market prop available for the popular makes/sizes of trolling motors that they advertise as giving more power & longer battery life. Again I'd think the original manufactures already have things well dialed in - a side note: there are postings on some of the fishing sites saying these Power Props or whatever they are called make the motor work harder and draw More electricity.
>

Trolling motors are not designed to go fast, they are more or less
designed to hold you still against the current or move you in a slow
pattern. If you want to use one as your 'main' motor, the design
assumptions they used no longer apply.

>
> One thing I did learn from the first canoe is 4 of these panels will burn out one 12 volt motor. With the help of a $6 Harbor Freight volt meter I found each panel will put out about 4 volts when hooked up to the motor (bright sunshine) So 4 was giving the motor like 16 volts.
Solar panels are current devices, not voltage. You really need some sort
of voltage regulator between them and your motor, or you WILL over volt
the motor in certain conditions. Simple battery solar charge regulators
might do it.

Solar inverters usually have fancy 'Maximum Power Point tracking'
circuits that work out the optimum current/voltage to apply to the array
to get the maximum power output.

--
Matthew Geier,
Systems Administrator, Australian Centre for Field Robotics
+61 2 9351 8149

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