Chuck Coiner of Hansen, ID asks:
Why not use an appropiately sized raw water pump on the Lugger?
Jim Leishman responds:
Onboard the Nordhavn 40 we are running two alternators at the front of the engine along with a hydraulic pump off the accessory PTO on the side of the engine. The cooling loop in the Naiads is only 1/2 inch and very little water flow is needed. To belt drive a pump dedicated to the Naiads only could be done using a second set of pulleys off the front of the engine however the tooled up belt guard supplied by Alaska Diesel and electric would no longer fit and a custom belt guard would have to be made up. A belt driven pump is not a bad idea except the cost is quite high.
The method we have begun using is to divert some of the Naiad hydraulic pressure through a flow control valve and using this as a power source for a small hydraulic motor attached to an impeller pump. The hydraulic part of the system should be totally reliable so the only service the system will require would be changing the impeller regularly. We have been running the generator aboard NORDHAVN for almost 3,000 hours and have not change it's impeller for the first time yet - illustrating the life span and reliability of the rubber impellers.
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