Valve Selection for 3rd SCV to Operate Grapple

[biffydog]

Hello,

I would like to add a 3rd SCV to a John Deere 2520 compact utility to operate a grapple. I don't want to go with the diverter valve but with a solenoid valve so that I have three separate circuits. I'm concerned about the speed at which the grapple will close and open due to the solenoid valve's characteristic of being completely open or closed.

I have researched the following options to slow the cylinder down.
1) add a restrictor in-line with the cylinder
2) choose a solenoid valve that has a soft-shift feature that adds damping to the spool during actuation
3) add PWM control to the solenoid
4) add flow control downstream of valve

The problem is I have no experience with any of these options.

The restrictor option is probably the least costly but I'm guessing this can cause heating of the fluid since some fluid will be forced through the relief valve.

The soft-shift option is about $75 extra cost and is somewhat adjustable in that some manufacturers offer different orifices to change the speed of the spool. I'm not sure if these are field serviceable or not. My other concern is that one manufacturer claims that all ports are "open" during the transition. I don't think that will be an issue because I plan to also use a pilot operated check valve as a load check on the circuit to prevent cylinder drift during valve transitions.

The PWM option to ramp the current to the coils is appealing because it is adjustable. However, I've read here that the PWMing the current to a valve that isn't designed for this doesn't work all that well.

The flow control option is worthwhile but not very space efficient unless I can find a flow control valve that fits into a D03 block.

I've learned a ton on this forum and want to thank you for providing further insight on this issue.

 

[J_J]

Most valves have load checks.

The 3rd function valve is connected in series, usually after the loader valve.

Keep in mind, if you use full lever on the loader, the 3rd function will not have any fluid.

Also any restrictor will may cause fluid to flow over the loader relief valve.

Some people also get away with 1/4 in grapple hose to reduce speed.
J.J.

 

[Leejohn]

When they say soft-shift, I'm almost sure that is how the spool is cut and that part is not adjustable. I use 1/4" hose on my grabber and it is a good speed. You don't need more then 1/4" if it isn't going run a motor or something that well be needing all the hyds your tractor has.

 

[kennyd]

Can you elaborate more on why your so opposed to a diverter? For a smaller machine like your 2520 it's a great option since real estate is limited and access to the power beyond circuit is limited.

 

[biffydog]

Can you elaborate more on why your so opposed to a diverter? For a smaller machine like your 2520 it's a great option since real estate is limited and access to the power beyond circuit is limited.

A couple of reasons. I don't want to install the diverter on the loader because I would also like to use the third hydraulic outlet to raise and lower the mid-mount mower deck. As it is today, I need to disconnect the hoses for the curl function on the loader and hook up the independent lift cylinder to those quick couplers that service the loader. I realize I could install the diverter on the tractor as well (I agree that the real-estate is sparse) but I figure if I'm going to go through that much bother to locate it on the tractor, I might as well plumb the solenoid valve instead. I also fear that I will not be able to "master" the coordination needed to return the joystick to center prior to depressing the switch for the diverter, and returning the joy stick to center prior to releasing the switch. I read somewhere that it isn't a good practice to switch the diverter under load/flow. With the dedicated third SCV, I wouldn't have to worry about that.

Rick at Everything Attachments has a video of a small tractor with a grapple and I believe he uses a solenoid valve for a dedicated third SCV. It seems to work quite well. In a video where he talks about the package that he sells that includes the solenoid valve he mentions that he is not a fan of diverter valves but doesn't elaborate why. He prefers a full function 3rd SCV.

 

[biffydog]

When they say soft-shift, I'm almost sure that is how the spool is cut and that part is not adjustable. I use 1/4" hose on my grabber and it is a good speed. You don't need more then 1/4" if it isn't going run a motor or something that well be needing all the hyds your tractor has.

Thanks for your reply. I agree that the spool is not something that I can adjust. J_J also mentioned using 1/4" lines to plumb the unit, at least from the valve to the load. 1/4" lines are easier to package and work with anyway.

 

[MtnViewRanch]

A couple of reasons. I don't want to install the diverter on the loader because I would also like to use the third hydraulic outlet to raise and lower the mid-mount mower deck. As it is today, I need to disconnect the hoses for the curl function on the loader and hook up the independent lift cylinder to those quick couplers that service the loader. I realize I could install the diverter on the tractor as well (I agree that the real-estate is sparse) but I figure if I'm going to go through that much bother to locate it on the tractor, I might as well plumb the solenoid valve instead. I also fear that I will not be able to "master" the coordination needed to return the joystick to center prior to depressing the switch for the diverter, and returning the joy stick to center prior to releasing the switch. I read somewhere that it isn't a good practice to switch the diverter under load/flow. With the dedicated third SCV, I wouldn't have to worry about that.

Rick at Everything Attachments has a video of a small tractor with a grapple and I believe he uses a solenoid valve for a dedicated third SCV. It seems to work quite well. In a video where he talks about the package that he sells that includes the solenoid valve he mentions that he is not a fan of diverter valves but doesn't elaborate why. He prefers a full function 3rd SCV.

Now I am just the opposite, I do not care for the solenoid operated valves, and I will elaborate.

The only positive thing that I see is that you can truly operate 3 functions at once. So what? Most of the tractors with 12gpm and less can't operate 3 functions at once effectively anyway.

You can not feather a solenoid valve, it is either open or closed. So your operation of that valve has to be either some sort of flow control which can be bothersome at times or the constant on-off on-off of the control switch. Yeah, that's what I want to do, constantly flick the switch. The solenoid on a diverter is not any different than on a true 3rd function valve, I don't see why it would be bad on a diverter and ok on the solenoid valve? I think that this was something started by someone trying to make the diverters look less attractive.

You have full control with a diverter, think about it, do you feather your loader controls, or just have them fully open anytime that you do a hydraulic function? Why would it be any different with any other hydraulic cylinder on your tractor?

You are thinking that the control of the diverter is much harder than it is. In reality it is very easy, for some unknown reason some people seem to think that it is time consuming. The switching back and forth is as fast as you can move your finger, there is zero hesitation.

I know that the majority of people that have 3rd functions want true 3rd functions. I can't figure out why other than bragging rights. :confused3: To actually get all 3 functions to work, the lift and curl have to be feathered just right so that some fluid continues to flow to the solenoid valve. Otherwise the valve will not work.

Most of these tractors have smaller GPM pumps, to operate multiple functions is very slow in my opinion, actually frustrating to me. I don't know maybe it is just me, it seems like most everyone is happy with their true 3rd function systems.

Anyway, you can mount a diverter on the tractor, it does not have to be on the loader. Have you ever thought about simply adding manual valves. Probably can be done for not much more than either of the electric alternatives. Here is a complete system that I have done many times with 2-5 valves, but if you only wanted one, that can be done also.

I'll probably get chastised for some of the things that I have said, but it is just how I feel about it for various reasons.

Just my :2cents:

 

[biffydog]

Hi Brian, Thanks for taking the time to share your thoughts on this subject. That is why I posted this question...to learn from others who have experience with these issues.
Installing a diverter would certainly be easier than a full solenoid valve and would still have the benefits of being able to feather the load. It would be cheaper too since the valves typically use only one solenoid and there is no need to add a load check since the upstream directional control valve already has them. The only thing lacking with the diverter would be full independent control of the third circuit...but as you mention, that independent control isn't really there if the other valves upstream are not being feathered too while being actuated. Thanks again for you thoughts. I may have to reconsider my decision to go with the fully independent 3rd SCV.

 

[kennyd]

Excellent description Brian, as you know I am in you camp 100%.

Biffy, there are MANY threads on this issue if you search...The diverter is the simplest way to operate a grapple, and you can still add a manual SCV on the rear for other uses-lots of threads on that also and many specifically related to you 2520.

Myself, Brain, and Artillian all sell something that would fit your needs quite well.