Thursday, April 21, 2011

Re: [Electric Boats] FW: how to determine maximum speed/ torque

 

Roland,

You need to measure the amp draw of the motor to know if your prop is the right size for your shaft speed or, said another way, if your shaft speed is right for your prop.  There is no way to verify you have the best pulley ratio without an ammeter.

The motor is rated for 1100 watts.  Assuming you don't want to change the prop you need to pick a gear reduction (pulley ratio) to cause the motor to pull 45 amps at 24 volts (thats 1100 watts)

Your boat will go about 5 mph with 1100 watts power.  It would take 1700 watts to go 6 mph.

The boat manufacturer set up the original motor and pulley ratio to give the best prop rpm.  Knowing the original motor rpm and pulley ratio, you can figure out the ratio that gives the same prop shaft rpm with your new 1100 rpm motor.

Your wire size looks very small for 45 amps.  You could be losing some power in the resistance of the wires.

By the way, a long skinny boat like a canoe will perform much better at low speeds than a short wide boat.  A big prop like 12" dia is more efficient than a small one like you are using.

If you are trying to improve the performance of the boat over how it came from the factory you will not have much success.  The hull is designed to perform at high speed with a light powerful gasoline engine. 

Good luck,

Denny Wolfe
www.wolfEboats.com




On 4/21/2011 4:02 AM, Roland Kruijer wrote:

 

Hello fellow members,
 
I send this Email, but didn't get any reaction. Is there's someone out there that can help me with this? I've read all the messages about people who only have commercial ideas about the electric boating. Not so for me, Í am just figuring out if I am on the right path...
 
Thanks,
 
R


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