Re: [PSUBS-MAILIST] ETEK motor (speed controller for this?)

[Deeperdowndude@aol.com]

Dan, 

Thanks for the advice and for the link.  Here's another controller link I got from the company that sells the motors.

http://www.evparts.com/shopping/product_details.php?id=271&product_id=3317

Yes I am thinking of using it in a surface boat.  Some of your comments lead me to think about it from the standpoint of a sub, though.  Could I ask you a couple more questions about that?

You said 34 horsepower was a lot for a sub and that 3600 rpm would be fast for the prop.  About that, wouldn't more horsepower simply mean the ability to go faster?  I understand the visibility-collision problem underwater, but other than that is there some reason why a fast psub isn't a good idea?

About the prop RPM: I've also read that fast props are good for boats and subs do better with slow props.  Is it because the sub prop would cavitate at the higher RPM?  And if so, couldn't that problem be avoided with a gear reduction drive or by simply running at a slower power setting and RPM?

But where you started me wondering was what you said about the batteries, though.  Unless I'm wrong, if I need 72 volts and 400 amps, and if I'm using 12-volt batteries wired together, that means I'd need at least six batteries rated for at least 66.6 amp-hours each?  So then, does your "starter" comparison mean it's only going to run a very short time: in this case less than one hour?  Am I right so far?

Paul  





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