Can an electric power steering pump drive a hydraulic ram

I have a pair of hydraulic lifting devices attached to a common mains electricity driven power pack. I want to make them individually portable with their own hydraulic power packs. Cylinder and ram dimensions are similar to the common import 3 - 5 - 8 ton devices sold as replacements for engine lifts and the like. Looking for a maximum force of around 2 tons but not normally expecting to need more than 1 ton.

Electrically driven power steering pumps off various cars seem to be readily available at acceptable prices, £50 - £100, from breakers. Look ideal for the purpose being compact and driven off 12V so could, should I ever need to, be used in the field where mains electricity isn't available. Question is whether they have sufficient output pressure and whether the control valving can be re-arranged or bypassed for pump up - bleed down control instead of continuous circuit. I guess I'd need around 1,500 psi delivery for my rams.

Alternatives appear to be the import air over hydraulic power packs or tipper trailer power packs both of which come in rather more expensive. I know that air over hydraulic versions of the engine crane replacement rams can be found for around £100 but I don't want to replace my good, industrial standard, rams with cheap imports.

Clive.

They may produce enough pressure, but I suspect they will only be a pump as there would have been a valve block in the rack to control flow and pressure.

This thread might be a starting point for you musings:

http://www.practicalmachinist.com/vb/general/ot-power-steering-pump-question-148528/

Likely referencing mechanically driven pumps, but maybe of some use.

I reckon a portable leccy generator might be a better alternative to messing around with power steering pumps and 12V batteries?

not done it yet

Saw that PM thread when it was new and the idea stuck around. Mostly about GM Saginaw pumps which are a rather different animal and specifically designed to be easily adjustable for output pressure by changing shims. Which doesn't alter the principle.

Got no intention of operating in the field away from power but if I get the capability for no extra cost will not complain. Mains driven power packs seem to be over-size for this sort of single ram device. The one that came with them can handle up to six at a time. My generator is one of the old uber quiet Honda EX5500 units, 5 KVA output and very neighbour friendly. Although on wheels it does rather stretch the portably concept unless you have a decent size trailer.

vintagengineer

Pump alone will do as I can probably strip the valves off what I already have.

Clive.

Hi, have you looked at the 12V electric hydraulic pumps used on Transit tipper trucks they usually have a reservoir, and a pressure release valve to let the fluid back into the reservoir.

Chris

Agree tipper system would be best as almost certain to work straight out of the box. But finding one at an economic price is a different matter. Used tipper and tail lift pump & reservoir sets seem to be around £120 - £150 in very grubby condition. At that price might just as well go a bit further and get new "UK stocked" pump, reservoir and pendant unit for around £ 180 - £ 220 off E-Bay. OK its Chinee but sold to the pro / industrial market so probably reliable for the couple of hundred times I expect to operate these things.

Clive.

Or brand new Bosch system.... **LINK**

Electrohydraulic power steering (EHPS) pumps are operated as constant flow devices and there is usually a torsion bar based valve in the pinion element (column) that creates a back pressure when sufficient torque is applied. This pressure acts on the ram which is basically the steering rack with piston seals. This forms a closed loop system, so is pretty much self-contained.

Typical no load current is probably something like 10-20A and the max current (when jammed against a kerb) may be over 100A, depending on the vehicle etc. The main control problem here may be the valving, as suggested. The ones I was involved with were brushless (ie controlled over CAN, LIN etc), so it may be difficult to even get them to run.

Another common source of electric hydraulic pumps would be fork lifts and electric pallet trucks. These are available 24V versions (possibly 12V??) and they are designed for just this kind of application. F expensive if you bought new, mind, so perhaps ebay would be helpful. Variety of manufacturers including Bosch.

Murray

David

Thanks for the link. Looks hardly worth going Chinee from "Who They" supplier.

Muzzer

Brushless motor being directly controlled by an ECU and logic bus was my second major worry after actual rated pressure. Given that the pumps normally run all the time I'd hoped there was a simple active on level in the logic, simple switch or relay seems to much to hope for, to just let it run bypassing all the clever stuff. I'm sure the modern systems have all sorts of logic and sensors integrated into the steering to give speed and turn sensitive steering weight / feel control along with energy use minimisation strategies to help improve fuel consumption. Not something to get involved with on a job like this. Maybe the older types, Citroen Saxo et al are simpler. Introduced in mid '90's I think which seems early for really clever stuff.

Beginning to look as if simply ponying up £200 odd a piece for new components made for the job is going to be the best strategy.

Clive.

Check the pressure required to achieve the rated load on your engine hoist. You can estimated the load on the cylinder using the rated load and the length of the boom and the length of the lever arm on the ram. For a rough estimate I am neglecting the inclination of the cylinder. The diameter of the jack cylinder is a bit larger than the diameter of the ram. If memory serves, it is about 1/8 inch larger. Using the diameter of the cylinder and the applied load you can estimate the required pressure. I suspect you will find a power steering pump will not achieve anywhere near the pressure needed to lift the rated load.

There are a few on The Bay around the £200 mark. I'm sure they would be suitably rated - but is your wallet?

Murray

Or try a Citroen hydraulic pump, belt driven, seen for +/- £75, produces over 2200psi.

Did a bit more digging. Found references to 1,000 or 1,200 psi output for Nissan electric systems which might be enough in practice. According to the TRW service manual ordinary engine driven systems go from 90 bar to 180 bar depending on pressure release valve setting.

Also found how to connect guide for Vauxhall Astra, TRW made, pump telling how to bypass the control side. Looks like the Vauxhall Astra unit draws around 50 Amp at full power although there is an 80 Amp fuse in the vehicle system. Vauxhall unit can be found for around £30 delivered which is sufficiently wallet friendly for experimentation.

Fair bit more to figure out before I can start playing but looks like we may have a result. Even if it comes out a bit underpowered at least I can be confident that getting a new Bosch tipper system won't be money wasted.

Clive

Pi R squared x psi / 2240 gives you the lift in tons.