Hydraulic proportional control valves...

Hi,
If this is not the proper group, where should I post such a topic?
I have a smail tractor mounted hydraulic crane where the control valve
assembly is a bit worn. Instead of just spending a lot of money in getting a suitable 'manual' control valve assy I consider checking a bit around to see if I can find a surplus electric proportional hydraulic control valve assy for at least 4 double-acting cylinders and replace my old control valves with this electric version. (I don't want wireless remote control, only wire)...
Are there different types of electric proportional valves for doible- acting cylinders or would almost any model do? (Given that flow and pressure are supported).
However despite that I work a lot with electronics I don't know how the solenoids normally are interfaced with the control pots. Do they use an electronic module between the joysticks and the solenoids which varies the current between the solenoids according to the position of the joystick, or is this circuitry normally included in the joystick assy? Thanks for some comments on this.
Does anyone here have suggestions on where to obtain such surplus equipment?
Other relevant comments and suggestions are highly appreciated :-)
regards Tor
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On 6/3/2010 6:05 AM, bushtor wrote:

Tor,
You want to undertake what will turn out to be a research project with a good amount of trial and error before you get it right. If you have the time for such a project, fine. I would suggest looking at the service and operating manuals for a unit you know, and talking to the mechanics at a tractor dealership. You can bake a better decision when you know more about the scope of your proposed project.
Jerry
--
Engineering is the art of making what you want from things you can get.

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Hi Tor
Proportional hydraulic directional control valves come in two basic designs, those where the spool has a linear measuring transducer fitted to allow close loop control of the spool position. This gives a more accurate control of the cylinder speeds, with better repeatability. The second type do not have any feedback system, but rely the force generated by the solenoid depressing a spring at the opposite end of the spool, until a balance position is reached to give a spool position the will give the control of flow. Both types of valve are available in both single and two stage configuration. A two stage valve is one where the valve has a small pilot control valve which then controls the position of a main spool to control the flow to the cylinder. See http://hydraulics.eaton.com/products/valves_proportional_directional_controls.htm Both types of valve require an amplifier to control the current supplied to the solenoid coils fitted to the valve, these can be simple current controllers or fully closed loop controls, again see the Vickers site for more information.
As suggested by Jerry talk to your local dealers before you commit yourself.
--
BillB

Leeds Lad in exile
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