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12v Hydraulic pump ?? ever tried this??

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12v Hydraulic pump ?? ever tried this??

Old 01-15-2002, 11:46 PM
  #11  
mjuwalters
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I belive WPM has 12volt steering pump that will soon be ready for market. Give them a call.
 
Old 01-16-2002, 07:37 AM
  #12  
jr
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I agree with you on the flows and the pressures but the external tie bar between the outdrives would effectively take care of that. If there is addional flow the additional steering effort would be transfered to the other outdrive externally.

The valve kit that mercruiser has, what does it include. I was pricing a second cylinder and pump and it starts getting pricey, of course. Does the valve kit include a second pump, and the valve, or valve alone. The valve kit is a better way to go.
 
Old 01-16-2002, 11:38 AM
  #13  
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jr-
Adding another steering unit WILL be very pricey, let alone finding room for it on the inner transom.
Mercs kit includes the priority valve, hoses, and fittings for either Saginaw or Brazil, depending on what you have.
Mindi at Doller Offshore or Marc at BAM can help you with a pump- I'm sure they have plenty both new and used, as well as give you a good price on the kit. The hoses for the second pump can be made for you locally.
I think you can get the whole thing done for around $1K, maybe a little more.
Good Luck!
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Old 01-16-2002, 02:55 PM
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Has anyone considered the use of an electric pump feeding a hydraulic accumulator as they do on jet air craft. This is done to supply a large volume of oil upon demand without oversizing the oil pump or causing a continuous parasitic load on the engine, and is especially usefull during peak demands on the engine, such as full speed maneuvers.

I plan to do this someday.

The hydraulic accumulators should be readily available from aircraft surplus dealers.
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Old 01-16-2002, 06:18 PM
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interesting concept there, but how much flow & pressure can be maintained for continuous operation??
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Old 01-19-2002, 12:37 AM
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formula 93; Is this question for me? I will try to give an answer anyway?

You ask how much flow and pressure for continuous operation. The problem is that you never operate it under continuous conditions or it would be pointless to do it this way, and you would just stick with the belt driven hydraulic pump.

As with the airplane, the accumulator is sized to operate, for example, the landing gear, the rudder and the flaps for maybe 3 or 4 full cycle operations. Then pause for maybe 20 to 60 seconds to be recharged by the electric hydraulic pump.

The same is true for a boat. You need enough hydraulic capicity to turn the steering wheel rapidly from lock to lock maybe three times. Then the pump recharges the accumulator. The pump only runs when the accumulator is depleted, hence it is not lugging on the engine all the time as does the belt driven power steering pump.

So as an intial guess, I would measure the volume of the steering ram, (stroke times area) and multiply times the number of lock to lock motions times 2 as each cylinder pushes and pulls through one complete steering cycle.

Then you take that calculated volume and find an accumulator of that rated volume.
Fortunately, accumulators can be piped in parallel to increase the total volume.

Accumulators are precharged with high pressure nitrogen on the other side of a diaphram or may have a spring loaded piston. The precharged ones are just like the bladder type of water storage tanks used for well water house systems, but they are designed for much higher pressures. The bladder keeps the precharge gas from dissolving in the hydraulic oil and causing frothing.

The electric driven hydraulic pump also is pressure and flow volume rated. For example, 20 cubic inches per minute @ 500 psi. You need a pump with enough pressure to recharge and run your system and enough capacity to recharge it every two minutes? These are just rough numbers. but if you have similar pumps, they also can be connected in parallel to meet the demand.

I would just guess that the belt driven power steering pump runs at about 500 psi and takes about 1 horsepower at design load.

Some people make log splitters using a starter motor connected to a power steering pump and cycle it all day in the cold weather. A car starter motor is rated at maybe 2 horsepower nominal and 5 horsepower peak. Don't hold me to these number as they are simply educated guesses.

So going back to the boat example, the advantage to this approach is one less V-belt to break, less gadgets mounted to the engine block, and less engine drag when you really need the power. Also, less engine lugging and killing the motor when maneuvering around the dock .

Call me anytime if you want to chat on this. 512 657 1104 cell.
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