Fred Murphy Diesel Electric power????

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electric tug
Posts: 64
Joined: Thu Feb 11, 2010 4:15 am

Fred Murphy Diesel Electric power????

Post by electric tug »

Hi this is my first post- i just bought the fred murphy plans and i want to investigate inexpensive diesel electric propulsion

later ill build a large houseboat/barge to be pushed by the Fred Murphy.

so here is what i wondered- I was thinking of using two high torque 10 hp golf cart motors making it a twin screw. using an fnr swith and a controller and throttle for both. or maybe even two seperate controllers. then use a small 5000 watt diesel genset and either an alternator and a motor to run the alt to charge my system, or a simple 100 amp battery charger for quick charges w/ 120 v off my genset? using lead acid batteries.. making it effectively a diesel electric...would that be enough power(2x10hp golf cart motors?) using larger dia props and geared for torque? i know it wont be fast but im looking for torque not speed.

i have another interesting option: fro 200.00 on e-bay i can buy a used 25 hp 220 v dc electric motor- shunt wound and 1150 rpm cont. duty.

this is very robust, and is an industrial motor.
it weighs in at 650 lbs!
would this develop more torque than a golf cart motor of the same hp?

my only problem is...i know i could use 24 batteries in series for power, but what would i use to control speed and fnr?
any ideas?? i sure would love to use this electric motor, as my guess it has massive torque for a large diameter prop and towing power etc.. same idea for battery charging. run a series of two truck alternators off a small 120 volt 1 hp motor at 3750 rpms plugged into The 5000 watt genset. It should be enough then to charge my batts fast. and perhaps run the engine too using some kind of an inverter when the batts are charging?
or if there was a way to convert the ac 240 volt ac to 240 v dc then i can run the boat on the 10 hp 5kw genset?.

i sure would like to hear any ideas by anyone who knows how to set up a large industrial dc motor???

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Mr Hot Rod
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Location: Chelsea, Quebec, Canada

Re: Fred Murphy Diesel Electric power????

Post by Mr Hot Rod »

my only problem is...i know i could use 24 batteries in series for power, but what would i use to control speed and fnr?
Can't answer most of your questions, but we may be able to suggest a solution to the F/N/R question.

EV conversions use an adapter to mate the electric motor to the vehicle's manual transmission.
You might consider fabricating or altering an existing adapter to a marine transmission. This would give you F/N/R and reduction gearing (e.g. 2:1 or more).
  • - A Velvet Drive bellhousing would bolt up to the marine trans
    - An adapter plate would mount the motor to the bellhousing
    - A coupler would mate the motor's output shaft to the transmission's input shaft
With the hydraulic transmission's reduction gear, you could use a much smaller motor which would reduce your motor weight and power requirements. The reduced shaft speed means that you could swing a large diameter propeller.

I'm sure others will chime in soon ... Enjoy your project and don't forget to post plenty of photos along the way !

Paul Kane Chelsea, PQ

Building the Glen-L Hot Rod :

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Location: Coastal Georgia

Re: Fred Murphy Diesel Electric power????

Post by kens »

New technology is marine hybrids going on sailboat engines. Small sailboat diesels that are electric hybrids. The flywheel is basically replaced with a armature taking the place of the flywheel as we know it. The bellhousing holds the windings. There is a clutch between the engine and this new style flywheel, so, you can run the engine as a regular engine, or, run with generator online and recharge all systems, or, disengage the clutch and run it as a electric drive.
These engines are already in production and for sale.
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

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Location: Cassville, Missouri (SW MO)

Re: Fred Murphy Diesel Electric power????

Post by aero_dan »

I know a bit about the land based EV solutions, check out a Curtis Controller. They are set up for about any running voltage you could ask for. Also, the sailboat drive is a good idea, albeit a bit more expensive in the beginning. As for the Golf cart motors, they can handle up to 144VDC, I have found. And folks like those at D&D will help you with the matching. Also, you must remember that the higher voltage you put to a DC motor, the more torque it will produce. (lamen call it more horses, but it really isn't) Also, the amperage goes down by the inverse of the voltage up, for the same output. Example: If you double the voltage of a golfcart motor from 36VDC to 72VDC, have an acceptable controller, the amperage would drop from 450 amps, to 225 amps, (for the same torque.) Thus, if your 72VDC controller is a 450 amp model, if you apply full throttle, you have just doubled your output, (mostly). There are some other factors there too, but that is a good example. My best advise?, ... Contact Vic Dejohn

Better, faster, cheaper. Only ever found 2 of the 3! (But still lookin.)
So many boats, little time.

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