ok so Dan I gave your Electric over hydraulic idea more thought and it could be a really good way to tip toe into going electric on this boat.? I like the small steps. I have been the 6month haulout guy before. I have been the 5yr refit guy. Once the sawzalls come out and the tent goes up the boat doesn't see the light of day for many moons. ;)
?
I also posted this over in DIY electric car as a read a few hydraulic conversion threads there with folks using skid steers and tractors to go electric.
?
Here is how i see it working:
?
Aux propulsion setup. Catamaran, 56ft long 26,000lbs, 2.5'draft
It is already hydraulic.?
It has one 85hp engine, coupled to two hydraulic pumps(valved for FWD and REV), hosed to 2 gearmotors, bolted to saildrive propeller units.
?
I would like to start small, as in just enough power and $$ to get the boat on and off of a dock in a clean smokeless fashion. I can run the diesel and its pumps when offshore for now.
?
The current setup uses Parker/Denison gear motors bolted to the saildrive propeller units. (photo below) They move 28mL per revolution.(1.7cubic inches)?
?
I thought that the simplest way to add an electric motor would be to do so at the engine, but alas the engine is directly coupled to the hydraulic pumps. I would need to decouple and put that on a clutch. Or remove the engine completely. If i remove the engine completely i need a big electric motor to run Two hydraulic pumps, so then i would rather just put smaller electric motors right at the final drives anyways. This is the end goal in a year or so. Just electric motors at the final drives. But for the short term i would like to get comfortable with electric drives, larger battery banks, larger solar etc before going purely electric.?
- So i bailed on that and decided to try to add small electric motors closer to the final hydraulic motors.?
?
- The props get the boat moving well at 600-1000rpms, and there is a bit of reduction in the saildrives. So I figured that I would need to get these existing gearmotors to spin at about 800-1200rpms to get the boat to move. So thats around 10gpm max i would need from an auxiliary pump to do it. (At 1000rpm the existing gearmotors are spinning 28,000mL thats 7.3Gallons.)?
?
So i have repaired excavator hydraulics and saw mill hydraulics, but am not very familiar with the tech as a whole.
- Can i just add a hydraulic pump Tee'd into the system as planned? If i add a tee, I will add a check valve, and then i need to decide where to pickup fluid from. Can I pull fluid through the whole system (cooler, old pumps, etc) via what is normally the fluid output line?-By teeing in upstream of the new checkvalve? (please see terrible sketch #1 alas i see no way to run this in REVERSE)
- Otherwise I can isolate the new system with solenoids (ref: terrible sketch #2)
?
So if that above does work, then I just need a motor to spin it. I currently use 2000rpm on the diesel to run the whole kit at crusing speed. Thats 40kW, so 20kW per hull. I don't need to match that, Half of that or less is good for these auxillary units. So 10kW per hull.?
?
So i found the ME0708 and all of its siblings. 48VDC & that seems to be ideal especially if i plan to go all electric in the future.?
?
Now, lastly the power band for the ME0708, it likes to run at higher speeds, 2000-4000rpms. So I chose a bi-directional hydraulic gearpump that moves 1/3 the fluid as the current Parker/Denison gearmotors. That way my new pump spins 3x as fast. So the ME0708 can spin 2000-4000rpms.
?
So I found an Honor Hydraulics gearpump, it moves 0.52 cubic inches per revolution (8.4mL plenty small) ?
Honor 2MM1U08. ?
?
Also added a high pressure accumulator. There is no cooling as i hope to only use it for 10-20minutes at a time.
PARKER Diaphragm Accumulator: 10 cu in Fluid Volume, 10 cu in, 11 gpm Max. Flow
Item 6NZK0 Mfr. Model AD016B25T9A1
?
So thats my tenative plan:
ME0708?
Sevcon 4q reversable controller?
Honor 8.4cc pump
tee's, solenoid valves, hoses.
lovejoy coupler.
?
?
?
