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Thread: OT: Power steering pump question
12-29-2007, 06:39 PM #1
OT: Power steering pump question
I've been toying with the idea of building a small bench size shop press with a power steering pump. Does anyone know how much pressure your average ps pump produces?
12-29-2007, 09:05 PM #2
I think a PS pump runs about 500-700 PSI. That's less than what most presses would be designed for; I'd think that more like 2000 PSI would be desireable. The other problem with a PS pump might be the size of the reservoir. Older pumps had the reservoir combined with the pump, newer ones are often remote from the pump, but still limited in capacity. Remember, as you stroke the cylinder outwards, it'll require more oil than when retracted. Again, depending on your particular cylinder.
12-29-2007, 09:15 PM #3
I built a oil filter crush using a power steering pump. External pressure relief is 2500psi. I have broken 3 rams so far with it.
12-29-2007, 09:50 PM #4
Thanks for the guick replies guys. Guess I'll just have to get a pump and try it.
I like your avatar. I'm mainly into antique Oliver's, but I have some IH stuff too.
12-29-2007, 09:57 PM #5
I am not being nasty. I can only answer this question in the same way as if you would ask,'how high is up?'. Power steering pump pressures range from 300psi, all the way up to 2200 psi. Some are self regulating, while others will virtually blow apart without some kind of external relief valve.
The best way to discover the maximum pressure on any pump is to simply put a gauge in the high side port. Most automotive pumps have a spring set pressure bypass that is not adjustable. Simply turning over the pump, with fluid in the resivoir, will show that unit's max pressure.
Industrial power steering pumps are another animal. The pump on most older machines has no pressure relief. There is also no reservoir. I am using an Eaton gear power steering pump off of a 500 Clark machine, for pumping duty. It will deliver unlimited pressure, until the half horse electric motor stalls. I formerly had a one horse motor on this unit. After someone 'borrowed' it, my pump came back with a toasted motor. The first time they dead ended the hose, the #13 key sheared off the pump. The second time this happened, the key held and the motor fried.
12-29-2007, 09:59 PM #6
no idea on pressure but I would look at European cars for the pumps. Volvo I know used a pump with a remote resivor tank. Simple to add a bigger resivoir and add hose to move the resivior around, out of the way.
12-29-2007, 10:05 PM #7
I thin kthis refers to a ZF steering pump on a Audi?
On 960, maximum power steering pump pressure is 1320-1420 psi
(93.0-99.9 kg/cm ). Pump volume at 500 RPM is 5.3 qts. (5L)
12-30-2007, 01:14 AM #8
Well this is topical. Not to hijack, but on the SB forum I posted a similar question about using a GM PS pump to run the hydraulic feeds on a SB milling machine. GM power steering for SB mill Q's
In my case, the pressure is way to high & so is the volume. The GM pumps can be somewhat adjusted by removing shims from the regulator (or adding them to increase pressure). Apparently factory set up tends to be around 950 -1,000 psi. My question is how much is each shim worth, in PSI terms. There were only 2 in, and I removed them both.
Are there any sort of off the shelf external regulators with flow control that could just be plumbed into the high side of the pump, overflow routed back to the reservoir? Anyone know how slow is practical to run the GM pump? I'm belted down to about 600rpm and it stalls the 1/2 hp motor almost instantly.
Oliverdude, these things seem more favorable to your application. From what I've been discovering, aftermarket pumps are often over 2,000psi and flow rates from 2 - 3 gpm. I think you are on the right track....if you pick the right pump and maybe someone here can spec the right one for each of us!
12-30-2007, 02:20 AM #9
car convertable tops used to use a dc pump unit. they only use hard plastic lines for pressure so they must be low pressure. I think the motor reverses to change flow direction to raise/lower the top.
here is one from a Jag, no relation etc.
12-30-2007, 02:44 AM #10
They are proud of that little baby,but very cool pump.
You might try these guys...http://www.hydraulicinnovations.com/index.htm they can probably put you onto what is required to bring the pressure into your power range. If not at the website than on their listed forum in their questions section.
You need to find a manual that would give specific pressure requirements for that SB mill.You might be looking for to little pressure to be able to move parts around.It might require the pressure you have,but less volume. I really don't know just thinking out loud.
12-30-2007, 03:21 AM #11
Quote: "You need to find a manual that would give specific pressure requirements for that SB mill."
KDC, according to the manual Robert L. linked to, 300 psi is the SB factory figure.
It appears I had the pressure adjustment procedure backwards for the GM pumps. Apparently shims are to be *added* to reduce pressure. This should make it a lot easier, as there would appear to now be no (positive value) lower limit. Hopefully with a little cut & try, perhaps 300psi will be workable for this pump afterall. The shims are just thin aluminum washers, so easy to make.
12-30-2007, 05:12 AM #12
I've always thought power steering pumps would be good elsewhere.
I've been wanting to stick one on my cherry picker, and build an external control valve system. The existing valve is such a POS for letting it down. I thought it would be cool to put a nice high quality valve on the outlet, and setup a spool valve system for it. Another project for another day. I allready extended the rear legs out, and put bigger wheels on it so it's more stable and rolls easier. It was a scary contraption, and the rear wheels didn't exactly survive the B&S mill!
Does anybody know the displacement of a standard GM saginaw power steering pump??? I've got a couple laying around, but I dunno how to set them up. That really depends on the displacement.
12-30-2007, 01:07 PM #13
A standard gm saginaw power steering pump is set from the factory to put out 1000-1200psi depending on the car it came from. It can be altered by changing shims in the relief piston on the high pressure line on the back of the pump. From what I know each shim is worth about 100psi.
Ford systems use less pressure than the GM saginaw pumps.
All of this is from guys that use them as hydro ram assist steering on pirate 4x4. I have adjusted mine on my jeep to put out less pressure as it was in an older lightweight Jeep and the steering was way to easy.
12-30-2007, 01:43 PM #14
Used a GM Saginaw from late '60s heavy Chevy, to power the hydraulic assisted sector gear steering assembly that I used to raise the Gannon on a small homebuilt tractor.
Had to modify the hydraulic valving for hand selected up and down. I turned the box 90° for vertical swing of steering arm. Valve mod was easy.
Worked great but hydraulic fluid rapidly overheated with constant Gannon adjustment. I inserted a small radiator and fan into the system as an intercooler and solved the over heat problem. Ran the hydraulic fluid through steel brake lines clamped to the frame, from the front mounted pump to the rear mount Gannon. Bigger might have been better but the brake lines work well.
As GM intended, pump resevoir is plenty for steering gear.
12-30-2007, 05:22 PM #15
well I'm up to .150 length of SS spacer (~= 6 - 7 shims, they vary a little between .020" - .025") and slowed the pump down to a little under 600rpm (guestimating based on pulley size). The 1/2Hp motor now will pull it for extended periods without overloading. I need to drop a few more psi, or go buy some more pulleys to lower the revs a few more, but getting in the ball park. It appears the rack gear key may be sheared, maybe why the system was taken out of service by previous user*, so need to address that before finalizing the pressure vs vol approach.
*I'm hoping that's (sheared key) -All- it is......
12-31-2007, 03:03 AM #16
Oliverdude, from what I have figured out over the past couple days working with the Saginaw pump, they put out probably close to 2 GPM depending on rpm. I am running mine at slightly under 600rpm, and probably have it down under 400PSI. At that rate, my 1/2HP motor seems ok with it. At that rpm, it will also not always "engage" or "prime" if I have had it apart to make an adjustment to the pressure control. I have to put on a bigger motor pulley (about 750 pump rpm, maybe) at which point it will run briefly, the pump will engage, and stall the motor. Then I can change back to the smaller pulley and everything chugs along working fine, including stop and start again without further "priming".
What I'm getting at, is if a cheap 1000psi pump works for your application, the volume is pretty good, but you might need "a few" HP to run it. Since you're looking for pressure, there is not a way to reduce the flow to reduce HP requirement, unless by an external flow control and return line. As mentioned, there are aftermarket gear pump, PS steering pumps rated for slightly over 2kPSI. The vendors might be able to tell how much HP one absorbs. OTOH this Chevy pump cost $15 out of the local Pick-a-part junkyard so cheap to experiment with.
BTW, everything works fine for the mill, now. Need to find a pressure gage to feel secure about using the stops, though.
12-31-2007, 11:00 AM #17
Thanks for the info. I have a 3 HP 3-phase motor I think I will run the pump with, I also have a smaller one of unknown horsepower that I will try. I'm also thinking about building some neat implements for my garden tractors and using one to dump trailers, run a loader, etc. Guess I'll have to hit the junkyards in the near future.
12-31-2007, 02:13 PM #18
Your power steering pump is not designed to run that slow. If I remember right th GM pump is a vane pump and you don't have enough RPMs to throw the vanes out.
12-31-2007, 03:29 PM #19
The GM pump is pressed into the reservoir isn't it ?? If that is the case it might not be too hard to build a bigger reservoir for it.
12-31-2007, 03:37 PM #20
how about a cheap pressure washer.
all the best.markj