Kirsti -<br>I considered purchasing a lynch motor
a couple of years ago for a smaller solar electric
boat, but the price was a bit too high for the high
school project which was limited to 24 volts. Their
specifications are very good, noting 87 - 93% max efficiency at
voltages between 12 and 48. Their web site and literature
has great charts and much info on electric boat
conversions. <br><br>I'm on my third electric boat project and
all three have been inboards with cog belt drive and
series-wound dc motors. The first used a surplus Thermo King
refrigeration motor with an industrial (not marine!) Leeson PWM
motor controller. The last two have used Advanced DC
motors with Curtis PWM speed controllers and Albright
system and reversing contactors (relays). The Advanced
motors were chosen for budget reasons. The Curtis
controllers are rugged units, sealed in a watertight aluminum
heatsink case. They're used in a lot of electric vehicle
conversions. System on/off is usually controlled via a 12v
coil contactor and a 12v coil reversing contactor.
Albright is a typical manufacturer, and they make
"marinized" models. These relays are not cheap - expect to
pay $75-150 for the main contactor and $150 - 225 for
the reversing unit, depending on system amperage. You
have to use them because the Curtis controller isn't
designed as a full h-bridge (reversing)
controller.<br><br>With all this said, the ~$1200 Lynch motor claims much
higher peak efficiency than an Advanced DC motor in the
36-48 volt range (92% vs 85%)and the Lynch's efficiency
curve is very flat through most of it's RPM range. The
Lynch motor weighs about 28# vs the 50-60# of most
series wound motors w/ similar specs. I'd explore using
a $QD brand speed controller - They are British w/
US reps, and their top model controllers have
solid-state revers built into their design. They also have a
number of standard safety features like
acceleration/deceleration ramping linked to reverse. If you throw the motor
into reverse at full speed, you won't fry the
controller. Instead the motor will decel rapidly, reverse
kicks in, then accel starts. 4QD has worked with Lynch
in Europe on boat and go-kart projects. They also
have this nifty weather resistant control box with an
umbilical you can carry in your hand for on-off, speed pot,
reverse, etc.<br><br>Good luck on your
project...<br><br>Chris Krumm<br>krumly@...
