splitter control valve...

[jinman]

Your log splitter valve is about 3 times the volume from your tractor. Do you notice any difference as to lever movement, say from your tractor. Do you have feather control from the git go?

I think that is what [ mrcaptainbob ] wants to know. My view, is that you will not have the fine control as with a matched up valve/pump. It should work if the pressure and port requirements are met.

Sorry for any confusion.

You know, I just don't think that I pay that close of attention. I bump the valve lever until the ram seats the log firmly up to the wedge, and then I push the lever all the way to the stop while the log is splitting. If I need to stop, I immediately center the valve. What I have noticed is an amazing difference in the speed of the splitter's ram if I run the tractor at 1200-1500 rpm instead of 2000 or higher. 2000 rpm seems to be an optimum and acceptable speed for the tractor.

 

[J_J]

What I was try to determine, was, since you have an over-sized valve, do you have to push the lever half way before the cylinder starts to move. That is interesting about the rpm thingy. You should be pumping more GPM the more rpm you have. What I computed is this. Using a reference pump displacement of 1.2 cu in, at 2000 rpm, pump volume is 10 GPM, and at 1500 rpm, the pump volume should be 8 GPM. If you get a chance, check out that lever position for me. Thanks

 

[Diamondpilot]

Not that its the same tractor as others but on my 3 point splitter I find 1300rpm or so is the best speed to split at. Any higher rpm does not seem to yield more power and just makes more noise.

Chris

 

[Redneck in training]

I order to have control the control element has to have the largest pressure drop of all parts of the loop. If the valve is oversized it is the pump that is the bottleneck for great part of the valve stoke. The valve will start having effect only after it is, just guessing, way past the half stroke. In other words fine control with oversized valve will be difficult. Since the application of OP is a splitter I think it would matter very little. How much of precise control a splitter needs?

 

[SkunkWerX]

Here is a practical view of what I think JJ is conveying.

I have a 5hp splitter, 4" cylinder, and a standard Prince 25 GPM log splitter detent valve. Oh, the missing element, an 11gpm pump.

So my control valve is more than double rated on total GPMs available.

I've used this same splitter for maybe 20 years? That's anywhere from 2 to 4 cords per year, for 20 years. Let's just say I am quite familiar with this set-up.

Here is how it works: When I crack the control valve to start the cylinder extension, as soon as the spool is far enough to allow flow, the cylinder moves at what appears to be it's full speed of motion. Maybe it's 80% or 90% of it's speed? But there is little to no speed control. It's like it's ON or OFF.

I have had numerous cases where I wanted to feather or move the cylinder slowly, "inch it" if you will. With the motor at operating RPMs this is nearly impossible. I can move it incrementally with a very fast quick flip of the control lever, in short bursts, to try to approximate where I want the cylinder to extend to. I CANNOT slightly open it [feather] and have it move at, let's say 25% of it's normal speed for example, it doesn't happen.

The ONLY way I can change the speed at which the cylinder moves, is by drastically reducing engine RPMs, which simply slows down ALL cylinder motion. Interestingly enough, even by cutting the pump flow this drastically, there is still NO feather control. It's like it's ON or OFF, just slower.

This would be indicative of what JJ is saying, that is, a much larger rated Control Valve, with it's larger orifices and ports, is going to "OPEN UP" to the smaller flow much more quickly.

No theories, no drawings, no diagrams. Just a practical real world offering of what happens.

Again,

As soon as I crack the valve, I have made an opening large enough to allow a large % of the flow to go to the work port , hence, the characteristic it exhibits is like being either Full ON or OFF in terms of the flow.

Hypothetical: if I replaced my pump with a 16gpm pump, I would suspect I would gain a a measured amount in the way of "control" or ability to "feather". If I upped it again, to a 22GPM pump, I would gain even more control and ability to slow the movement of the cylinder based on the control I have over the total flow.

Perhaps if my control handle on my existing set up where 3 feet long, I would be able to actuate the valve so slightly as to control the speed??

But, that's not allowed, because I started this post as a "practical" exercise.

 

[AKKAMAAN]

Here is a practical view of what I think JJ is conveying.

I have a 5hp splitter, 4" cylinder, and a standard Prince 25 GPM log splitter detent valve. Oh, the missing element, an 11gpm pump.

So my control valve is more than double rated on total GPMs available.

I've used this same splitter for maybe 20 years? That's anywhere from 2 to 4 cords per year, for 20 years. Let's just say I am quite familiar with this set-up.

Here is how it works: When I crack the control valve to start the cylinder extension, as soon as the spool is far enough to allow flow, the cylinder moves at what appears to be it's full speed of motion. Maybe it's 80% or 90% of it's speed? But there is little to no speed control. It's like it's ON or OFF.

I have had numerous cases where I wanted to feather or move the cylinder slowly, "inch it" if you will. With the motor at operating RPMs this is nearly impossible. I can move it incrementally with a very fast quick flip of the control lever, in short bursts, to try to approximate where I want the cylinder to extend to. I CANNOT slightly open it [feather] and have it move at, let's say 25% of it's normal speed for example, it doesn't happen.

The ONLY way I can change the speed at which the cylinder moves, is by drastically reducing engine RPMs, which simply slows down ALL cylinder motion. Interestingly enough, even by cutting the pump flow this drastically, there is still NO feather control. It's like it's ON or OFF, just slower.

This would be indicative of what JJ is saying, that is, a much larger rated Control Valve, with it's larger orifices and ports, is going to "OPEN UP" to the smaller flow much more quickly.

No theories, no drawings, no diagrams. Just a practical real world offering of what happens.

Again,

As soon as I crack the valve, I have made an opening large enough to allow a large % of the flow to go to the work port , hence, the characteristic it exhibits is like being either Full ON or OFF in terms of the flow.

Hypothetical: if I replaced my pump with a 16gpm pump, I would suspect I would gain a a measured amount in the way of "control" or ability to "feather". If I upped it again, to a 22GPM pump, I would gain even more control and ability to slow the movement of the cylinder based on the control I have over the total flow.

Perhaps if my control handle on my existing set up where 3 feet long, I would be able to actuate the valve so slightly as to control the speed??

But, that's not allowed, because I started this post as a "practical" exercise.

I think this valve have a spool that closes the center EARLY, already after a short movement of the spool, and that forces the full flow to the cylinder even if port is not fully open. If we think about log splitter operation, cylinders are usually so slow so feathering is rarely necessary. Feathering allways creates flow and power losses into HEAT, so I would say a good logsplitter valve should be more on-off than not. My picture shows how a Prince valve closes center before half spools stroke......

This is one of the parameters (how spool lands over lap center and work port) valve designers are playing with to make a spool valve act a certain way, with out changing the size of the whole valve....

Edit:
Feathering or fine metering ability imrpoves a lot from those metering notches you can see on the picture. Also to mention that fine metering depends on load pressure at work port.

 

[shansen]

I agree with you 100% AKKAMAAN. I'm also certain you have a large number of students you have taught over the years that have done very well in the Fluid Power industry.

 

[AKKAMAAN]

I agree with you 100% AKKAMAAN. I'm also certain you have a large number of students you have taught over the years that have done very well in the Fluid Power industry.

Thank You shansen!!

 

[greasemonkeyok]

Why do the call it a "spool"?

Generally a spool is a storage device of some sort, like a spool of thread.

P.S. This discussion is very informative.

 

[kennyd]

Why do the call it a "spool"?

Generally a spool is a storage device of some sort, like a spool of thread.

P.S. This discussion is very informative.

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