question about motor control valve

[marcuswayne]

Couldn't you just use a valve like what's on a front end loader that raises and lowers the arms?

On my loader, the more I push it the faster it raises. The more I pull it, the faster it lowers. If I let off of it, it stays where it's at.

I think that is going to be my next thing to try. The valve that I am using came off a riding lawn mower ( small valve ). The valve is open or closed. If I use a lager valve that might work, giving me more control over the flow. Thank you

 

[MTGreen]

Did you use an oversized valve in terms of flow? My limited understanding is that if the valve is oversized it will be harder to make fine adjustments.

I also asked on TBN one time if there was a difference in feathering/fine adjustment ability with cheap/chi-com valves and quality high dollar valves and never got a really satisfactory answer. I suspect that there is a difference

 

[oldnslo]

MTgreen is correct that over size valve makes fine movements far more difficult. Typically but not always more expensive valves will have better metering characteristics for fine control and some will have built in compensator to make the valve spool pressure compensated for even more consistent flow control with varying inlet and work port pressure.

Marcus,
any idea what flow rate you are trying to control to that feed cylinder? I suspect probably less than 1 GPM for cutting. Am I close?

 

[marcuswayne]

Did you use an oversized valve in terms of flow? My limited understanding is that if the valve is oversized it will be harder to make fine adjustments.

I also asked on TBN one time if there was a difference in feathering/fine adjustment ability with cheap/chi-com valves and quality high dollar valves and never got a really satisfactory answer. I suspect that there is a difference

The valve that I used is a small valve used on like a 20hp riding lawn mower.

 

[marcuswayne]

MTgreen is correct that over size valve makes fine movements far more difficult. Typically but not always more expensive valves will have better metering characteristics for fine control and some will have built in compensator to make the valve spool pressure compensated for even more consistent flow control with varying inlet and work port pressure.

Marcus,
any idea what flow rate you are trying to control to that feed cylinder? I suspect probably less than 1 GPM for cutting. Am I close?

Not sure of the flow rate, it also is hooked to other valves to run like the log hold down and the hydraulic motor to move the logs forward. So Im sure the feed rate is much higher.

 

[rScotty]

instead of trying to deal with the hydraulic flow rate directly, maybe it would be easier to put speed control onto whatever is driving your hydraulic pump. That has the advantage of keeping the pressure more constant when changing the flow rate.

 

[marcuswayne]

instead of trying to deal with the hydraulic flow rate directly, maybe it would be easier to put speed control onto whatever is driving your hydraulic pump. That has the advantage of keeping the pressure more constant when changing the flow rate.

The problem with that is there are times when I would like to cut faster, like when I am cutting soft wood. When cutting hard wood I need to give the cutter bar more time to cut.
The way thing are right now is it works great until I cut into something really hard and need to give the chain more time to cut.

 

[LouNY]

So it sounds like all you need to do is adjust the rate of the cylinder that is moving your cutterbar.
Something like this would allow you to regulate the cylinder slower in one direction while retaining full speed in the other. This valve allows flow to be restricted one way but allows full flow back the other way.

 

[marcuswayne]

So it sounds like all you need to do is adjust the rate of the cylinder that is moving your cutterbar.
Something like this would allow you to regulate the cylinder slower in one direction while retaining full speed in the other. This valve allows flow to be restricted one way but allows full flow back the other way.
View attachment 858290

I think that you are right. it will labor the hydraulic pump but I can adjust the pressure relief valve. Thanks

 

[oldnslo]

Not sure of the flow rate, it also is hooked to other valves to run like the log hold down and the hydraulic motor to move the logs forward. So Im sure the feed rate is much higher.

Marcus
Are you manually operating the controls for saw feed or is it electrically operated? I was assuming electric but now not sure.

If manual then a good metering valve sized properly could help.

To determine required flow you can measure the cylinder movement in inches per second and with known cylinder size calculate the required flow rate.

Formula is: flow = cylinder velocity times cylinder area