Adding a valve, how important is GPM matching pump output.

[J_J]

I think I would use this valve to control a grapple.

12 VDC 13.2 GPM SAE 8 DOUBLE SELECTOR VALVE

http://www.surpluscenter.com/_MoreSpecs/i9-7852.pdf

 

[EMB5530]

Yea, I may go that route if I cannot find a reasonably priced unit as I first said.

J_J I wondered does anyone make a selector valve that can have both circuts activated at the same time? Say you wanted to curl the bucket up and simultaneously close the grapple. Or is this unrealistic on such a circut because the flow would always follow path of least resistance(such as just close grapple while bucket stayed the same as there is less force needed to drop grapple than tilt bucket.)

Also, can the selector handle a hydraulic motor as I have other items I may want to put up front.

Thanks again.

Eric

 

[J_J]

You can do that with a port multiplier. One into two, etc

It is 4 QD's or 6 QD'son a hyd block that is controlled by a switching valve.

You can even make your own setup using tee's .

Selector valves can handle hyd motors, but you need a double relief valve across the motor, as the motor if under a large centrifugal force and fluid is shut off, the motor becomes a pump and the fluid needs somewhere to go. .

 

[petegoud]

Would something like this work? Kubota L3200 L3800 Tractor Front Rear Auxillary Remote Hydraulic Hydraulics Kit | eBay

 

[TomSeller]

Selector valves can handle hyd motors, but you need a double relief valve across the motor, as the motor if under a large centrifugal force and fluid is shut off, the motor becomes a pump and the fluid needs somewhere to go. .

Is the double check valve in case you run the motor both directions?

 

[MtnViewRanch]

Yea, I may go that route if I cannot find a reasonably priced unit as I first said.

J_J I wondered does anyone make a selector valve that can have both circuts activated at the same time? Say you wanted to curl the bucket up and simultaneously close the grapple. Or is this unrealistic on such a circut because the flow would always follow path of least resistance(such as just close grapple while bucket stayed the same as there is less force needed to drop grapple than tilt bucket.)

Also, can the selector handle a hydraulic motor as I have other items I may want to put up front.

Thanks again.

Eric

Eric, then you want a true 3rd function if you think that you want to do those 2 functions at the same time. As far as using the electric valves for a hydraulic motor, no problem, you just need to be sure to get maintained switches for the valves instead of the normal momentary switch.

 

[xtn]

Is the double check valve in case you run the motor both directions?

I think it's because if you have something big and heavy spinning on the motor, it wants to coast down smoothly. If you suddenly shut off the fluid flow by closing a valve, then WHAM! you're shock loading everything severely. You either need a double check valve configured in such a way as to let the fluid keep moving around through the motor even after you've closed the control valve, or you need a control valve designed for motors which will have a "coast down" feature by connecting the supply and return ports connected when not active. With such a valve, when you cut off the flow, you've made two loops: One loop letting the fluid from the pump go back to the tank, and another downstream loop letting all the trapped fluid between the valve and the motor keep going around. So the motor can coast down to a stop gently.

I may have some details wrong in the above, but I think that's the idea. Any of you experts please confirm or correct?

xtn

 

[J_J]

xtn,

If you are using a tandem valve to control the motor, and you move the lever to neutral, you have shut off flow to the motor, so the relief does what you said, just lets the fluid recirculate. The motor becomes a pump until there s no energy left.

The pump flow does go to tank, but it passes through the valve not the reliefs.

An open center valve will let the motor coast.

If the motor is a one way motor, you can use a single relief valve.

 

[xtn]

J_J thanks for the clarifications, but I'm still confused.

Any open center valve will let the motor coast? In order for flow to continue out of the motor and on down the return line, doesn't flow have to be available to move in from the supply line? I mean wouldn't it be sucking against the closed supply side? What's different about motor spools? I thought you needed something like this to allow freewheeling a hydraulic motor: http://www.northerntool.com/shop/tools/product_200311695_200311695

I thought any other valve - open center or closed center - would "trap" the oil downstream therefor restricting implement motion. I figured that since my tractor's hst acts like brakes when the pedals are released that it must not be a motor spool type valve. If it was, my tractor would freewheel, right?

If any open center valve will permit fluid flow on the implement side when closed, what keeps a loader bucket in the air? I mean this freewheeling capacity is essentially a "float" position, right? Except that it's with the valve in the neutral/closed position instead of detented past full open. Right?

xtn

 

[J_J]

TANDEM CENTER VALVES
Tandem center valves when in a neutral position by passes the flow of hydraulic oil to the return line. This is used to hold the cylinder/piston in position with no load on the pumps. When this system is the pump is running constantly to keep a ready supply of hydraulic oil, but as long as the cylinder/piston is not in operation the pump is working under no pressure or load. This system keeps wear and tear on the pump down to a minimum.

OPEN CENTER VALVES /motor spool valves
Open center valves are the same as the tandem center, except that in the neutral position all lines are connected back to the reservoir. The primary use of this system is to prevent "shock" loading when the valve is placed in neutral. This takes pressure off the motor. This system is used in situations where the operating device needs to be moved by hand.

CLOSED CENTER VALVES
This type of valve is used in a hydraulic system where the valve blocks the flow of oil from the pump into an accumulator. The accumulator (see below) is used to store the oil under pressure. This valve takes the pressure off the pump and in neutral locks the cylinder in place with no load on the pump.