Randy, Mark Stafford stepping up to the plate. There are many variables involved, and I volunteer to phone and/or email discuss details. You are welcome to "pick my brain". I have nothing to sell, and ask no money. I am just a green boat advocate/enthusiast
In direct response to your belt vs direct drive question: electric motors have a strong torque curve over their design RPM range. The limiting factor is cooling under full power. Belt drives (or other reduction gear drives) allow the electric motor to turn much faster than the propeller shaft, so the built in fan in the electric motor provides more cooling air at higher power settings (more propeller thrust). Belt drives thus allow big diameter, big pitch propellers to be powered by much faster spinning electric motors.
The alternative of small diameter and pitch propellers works, but is much less efficient from a power consumption vs motive result perspective. Efficiency rules the roost with electric boats, since stored or onboard produced electricity is precious.
Another alternative of big propeller & direct drive slow turning electric motor with an auxiliary powered cooling fan should be nearly as efficient as a built in fan, but it is one more piece of equipment that must work, one more potential failure point. Of course, the belt drive itself is "one more potential failure point" that would be eliminated by direct drive with an auxiliary cooling fan. I am a little surprised that I've not found examples of people trying auxiliary cooling fans instead of the more mechanically complicated reduction drives.
Besides, it's fun to spell auxiliary.
Maybe an auxiliary cooling fan with variable-speed that automatically adjusted it's cooling air flow according to the build-up of heat in the traction motor? That could be potentially more efficient than a "dumb" internal cooling fan built into the traction motor. A so described variable-speed auxiliary cooling fan would automatically compensate for ambient air temperature and humidity changes (the principle variables in flowing air's ability to remove heat).
Sorry for the tangent.
Ask more questions?
Mark Stafford
Oakland, CA
415-935-5090 green advocacy line
510-638-3234 hm
925-586-0839 cell
--- In electricboats@
>
> I have a westerbeake 1 lung 9hp diesel that is woefully underpowered. This winter the JB Weld that was dealing a cracked block in the water jacket sprung a leak. It is now time to take a serius look at an inexpensive EV system.
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> I looked at the Thuderstruck page and it seems to be the cheapest and fairly simple to install.
>
> We pretty much do day sailing with some weekends in the plans.
>
> It also looks a\like a direct drive system rather than a belt system.
>
> Can anyone enlighten me on the pros and cons?
>
> Thanks
> Randy
>
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