Trying to understand power steering hydraulics

[chimpboy]

Have a look at superwinch's website; they have some heavy models with max flow rates of 75 L/min or more.

Your power steering pump under likely winching conditions is probably putting out 11-15 L/min. But why guess? You can measure it by taking the low pressure hose off and sticking it in a bucket, then seeing how much fluid it spews out at 1000rpm (engine speed, pump is probably going faster) in, say, 5 seconds. Have two buckets, one for while you're timing and one to move the hose over to when 5 seconds is up. Yes it'll be messy but it's primary research

Most makes of fourby will be using generic power steering pumps. This means that they are built to cope with higher revs than a 4WD usually puts out, which in turn means that you could get a little more from your pump by using a smaller pulley. However I think you would be looking at something beefier than a car power steering pump to get the most out of a superwinch type, which is why I don't think there's a lot of point trying to combine two pumps; you might as well get a second pump from a truck or whatever and use that exclusively.

Also, you will find that power steering pumps with electric clutches are available, although they sure aren't cheap. I bet you could find a way to swap an a/c pully onto a pas pump though.

I am definitely not saying any of this is a good idea though, just putting a bee or two in your head to buzz around.

[me3@neuralfibre.com]

Toyota build the PS pump into the block on their diesels. Gear drive, can't vary the ratio easily (possibly at all).

I considered the electric clutches, but if loss of power due to recircualting fluid under high flow but no pressure is 3/10 of f-all - there is not much point. That's why I started way back with the dicsussion on how the fluid actually flows, cause I didn't know the PS box was (nearly) free flow when not turning.

Paul

[chimpboy]

Be sure to video your experiments!

[zagan]

Hate to be a spoil sport, but isn't hydrics for the pressure not the speed?

Like for pushing a ram, The one at my work, does about 20PSI once it hits the steel it jumps up to 1000psi on the dial.

The oil would be incompressable so it can push at a piston ie the ram.

Steam is the same at high PSI as well (compressed water basicly), why do you think it was used in steam engines for about 180 years straight, it's even still used now in some countries.

I would be pretty careful about what speed the fuild is going at because once it hits something the PSi will shoot straight up and if your hose can't handle the PSI pop it will go along with anything else with it.

I know that a new power steering hose for my 4wd is only $130 and that's only for 20 inches of hose, so you will probably be wanting to work out exactly what PSI your going to expect first then fuss about flow rates.

And I know nothing about about this stuff, well at least enogh to know you don't want to be doing anything stupid,

you'll want a big bloody sump for the oil all the machines at my work run 20litre sumps for a little 5 inch ram.

[hammey]

Firstly paul, what type of hyd winch are you talking about?
OX TJM or a whole new set up.....

I havn't actually seen one of these winches work but i kinda know hyds.

Im assuming your looking for line speed so lets not worry about pressure as this will only occur once you start winching.

It dosnt matter how much displacement your pump has, the amount of oil delivered to the motor is governed by the flow rate of the DCV. In plant applications you can get DCV's with variable flow rates,ie, there is a screw which can be turned to vary the stroke of the spool accordingly...
Less/More-- Faster/Slower

Im not sure how these DCV's are set up but it might pay to get the manufacturers specs as i suspect they would be set up for a single pump only. or only marginally higher to accomodate different size pumps.

cheers smitty

[me3@neuralfibre.com]

Winch would either be Milemarker (ox) or chinese knock off.
It's not competition speed, it's useable speed.
Milemarker is designed for 16l/min flow rate. Toyota I *think* flows 8l/min at some unknown RPM. That gives a (theoretical) line speed of 1m/min. 1200PSI gives a 10,000lb pull.
I don't feel like spending 1.5 hrs winching 100m.
BUT, I do want a winch that will pull forever, not burn out solenoids, not overheat and not melt synthetic rope.
The motor in the milmarker is a danfoss and supposed to be able to flow up to 60+ l/min. The DCV (I assume is Directional Control Valve) is limited to 17L/Min. This is all moot if the pump only delivers 8.

Now, as the PS Box is in series with the system, it has it's own DCV. That is likely to be the bottleneck if I start shoving more fluid through the system. BUT, that's only supposition, informed fact from a knowledgeable party would be useful.

Paul

[hammey]

With that last sentence you just answered your own question, its not supposition its fact.

At a given pressure your entire systems flow will be restricted by its smallest orifice.

Now lets assume your PS box can handle the combined flows of the pumps, you now have a couple of other problems to over come.

Firstly when running more than one pump you will need to run one way check valves out of each pump. eg. what if one lets go or you lose a belt etc.etc. wouldnt want to turn the second pump into a motor

Secondly, your now going to have two reservoirs that need filling evenly yet indpendently from a single source. hmmmmmm.
Pumps dont like being run dry..................

It can be done but i would hazard "not cheaply" or as easy as any one would first like to hope.

just my unknowledgeable 2c worth

smitty