John the only thing I would add as far as the costs go is you got to look at the long term picture. The average cost and maintenance over the next 5 years is probably $0. After that the cost of replacing a battery or 2 has to be figured into the equation but the motor is typically good for a few 100,000 hours. I could have told you (I think I did anyway) that on a larger boat the cost would have been higher on a multiple motor boat (pulley style) but I didn't even think about all the nuts and bolts you mentioned below. As for the controller, bite the bullet and get one to save you the grief. There I said it. :o)
Good Luck,
Steve in Solomons
Hi,
It is interesting to have followed through/along on an idea to set
things up at a significant lower cost. Maybe I have tried to reinvent
the wheel here.
My thinking was that smaller motors are cheaper than larger, even
allowing for multiples, and that I do not need 10 HP equivalent,
probably nearer 3 or 4 would be OK most of the time.
Also, I could then eliminate the controller, and just have switches,
simple on/off and reverse. A good saving there.
I had the idea to fabricate a steel frame 'box' that would be a chassis
to mount motors on. The labour involved would be free.
This would allow me to experiment with things like automotive DC
generators as motors, as well as new motors of around maybe 500 watts
each.
After digging deeper, and looking at the prices of Golf cart motors, as
an example, it works out that it is probably more expensive to go with
my multiple motor ideas!
I can save even more if I manage to find a used golf cart motor. But,
even with a new one, the expense difference is mainly in the timing of
the spending, in that I have to shell out a larger chunk of change
(money) for the larger motor, and all in a single shot.
The gains, however, are in the greater simplicity of construction of the
mounting system. If I can eliminate pulleys, as well, I also save the
machining costs of having them bored to suit, although lose some
versatility in ratio selection of motor to shaft speed.
There are 3 main single item costs to a regular system, from what I can
judge. The motor, the controller, and the batteries.
I might still be able to save on the controller somehow. I don't really
know what they actually do, to be honest, other than control speed, and
'soften' shock loads for road vehicle applications. But I can maybe do
that more manually by simply using switched lower voltage.
Thanks for the response to my shaft speed question Kevin, if I try
slower speeds and have heat issues, I will run a separate fan if needed.
And the batteries are a big variable, and represent an opportunity for
personal choice. If the need is for ten minutes running per trip, then
the $4000 type investment is probably not needed. Also, the small
battery pack allows opportunity for full non-grid, non-ICE generator
charging. And more batteries can always be a future improvement if range
is a problem.
But the motor choice overall would seem to be most economical if using a
single motor, especially if it is possible to eliminate the controller
somehow.
John
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