Hey Thanks, its great to hear comments because they cause one to rethink a bit.
I've listed some "approximate" efficiencies:
Gasoline Motor - 20%
Diesel Motor - 50%
Transmission - 75%
Electric Motor - 90%
Hydraulic pump - 85%
Hydraulic motor - 85%
Battery - 95%
Alternator/Generator - 85%
Solar Panel - 15%
Propeller - 65%
24.4% - Diesel driving a Transmission driving a Prop = 50% x 75% x 65%
24.8% - Diesel driving an Generator driving an Electric Motor driving a Prop = 50% x 85% x 90% x 65%
23.5% - Diesel driving a Hydraulic Pump driving a Hydraulic motor driving a Prop = 50% x 85% x 85% x 65%
Adding some numbers up I don't see a lot of difference in efficiency.
In my case, I'm on a mooring ball and do not have access to shore power; and I do some cruising, so very much want dependability. Hydraulic power eliminates the need of a transmission an instead uses a spool valve. Batteries kind of suck, and two friends have had trouble with their electric motor controllers. So I'm going to stick with hydraulics for the main drive. The components, pump, motor, hoses, spool valve, pressure relief valve, 2 gal reservoir, and sidearm heat exchanger add up to about $1650(new).
Over the years I've had engine problems: starter, water in the fuel, sheared flex coupling, plugged fuel line & loose battery cable to name a few. As I'm sure most of the members of this group have had similar problems. So as a backup I'll add the small electric motor with pump to provide some maneuverability around the docks and backup should the diesel not start. I have some heavy equipment, all hydraulically driven and have a small 12v Hydraulic Pack that I use for my dump trailer and to power my hydraulic press. I ran across a 500 watt(max) 12v log splitter that I may use in the boat, it has a two speed hydraulic motor which gives a little more flexibility. The electric has on/off with forward & reverse solenoid switches. I see no need for any speed control since max speed will only be about 2 kts. The solar panels can just about handle the small electric, and in a pinch can directly drive the motor without controller or batteries.
Thanks for the input, Ken
--- In electricboats@yahoogroups.com, "reesekc" <kcr@...> wrote:
>
> I have a Hughes 35.5 Sloop of which I just removed the Atomic Four motor with a V-Drive. I am planning to replace the motor with a hybrid hydraulic drive system. A hydraulic motor will be used to drive the propeller shaft; and to power this motor, I'm planning on installing a 3 HP electric motor with pump; as well as an 18 HP diesel also with a hydraulic pump. The plan is to connect the motors in parallel with check valves to prevent back flow, so the motors may be used independently or together.
>
> The electric motor will be supported with solar panels and a small battery bank. The diesel motor will drive a larger pump and of course have an alternator for general electricity and recharging the batteries.
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> I believe the hydraulic pump/motor system is simple and reliable, and I also like the idea of hybrid power system which greatly reduces the battery bank size. I've done a search through past posts, but I could not find much on "hydraulic motor driving a propeller". If anyone could steer me to a previous thread, or if anyone has some comments on the plan, I would appreciate input.
>
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