Simple hydraulic question (I think)

[Baby Grand]

Doesn't a backhoe's hydraulic circuit allow multiple (4) valves to be actuated at the same time?
If so, then maybe look at a backhoe hydraulic diagram to get started.

 

[J_J]

He said he wants the flow to be equal to both circuits.

You can use two valves on a BH, but might be difficult to have equal flow.

 

[Baby Grand]

He said he wants the flow to be equal to both circuits.

You can use two valves on a BH, but might be difficult to have equal flow.

Good point, JJ.
Larry - I'm not really proficient with hydraulics, so bear with me.
You want the flow to be equal to 2 cylinders - sometimes, or always?
Are you trying to keep the blade level all the time, or do you also want to be able to pitch it up on one side and then lift it up vertically & evenly?

 

[Leejohn]

Zebrafive:

I am building a grader blade to go between the two axles. Two lift cylinders (one on each side), one cylinder to rotate the blade and one to side-shift the blade. The two lift cylinders are the ones that must be able to move up or down all the time, i.e. at the same time. It would be nice if the rotating and side-shift cylinders were could also move all the time but isn't absolutely necessary.
Larry

Make you a juction block for the 2 cyls that you want to move at the same time. Mount it on the blade in the center so that all line are the same in pairs. At the hyd block put a needle valve adjuster or restrictor for each cyl for the press and return line then one control valve well work. It well take some time messing with to get it adjusted just right. Only restrict enough to even them out. You can make a block and if real handy you could even put the restricter right in the block. The block would be like a double T.

 

[bigdeano]

Would it be cheaper to use a rotating shaft with a link on each end to move the 2 ends of the blade equally? That's how a 3 pt hitch moves the 2 lower links equally. You could replace one link with a cylinder so you can tilt the blade. Then you don't need 2 cylinders to move equally.

 

[RobertBrown]

I'm glad your here.
Your are, without a doubt, one of the best members we have.
I have learned a great deal from you.
Thanks JJ

 

[joshuabardwell]

Would it be cheaper to use a rotating shaft with a link on each end to move the 2 ends of the blade equally? That's how a 3 pt hitch moves the 2 lower links equally. You could replace one link with a cylinder so you can tilt the blade. Then you don't need 2 cylinders to move equally.

I was thinking something like that as well. In tractors, there are two ways of accomplishing this, and neither one depends on equal flow rate through the cylinders. The first is, as you describe, where the two arms are linked, and a single cylinder moves them. The other is, as the FEL works, where there are two cylinders with a synchronization mechanism between them. It seems like this is a problem that has been solved already, and adapting one of the existing solutions would be best. But I can see that it could increase the complexity of the fabrication substantially, so maybe the "equal flow" solution is best.

 

[JerryG]

Larry check out the way a belly blade is set up by Grouser. You might be money, time and design ahead by buying from them or maybe just getting some ideals from them.
Welcome to TBN.
Grouser Products

 

[TSL]

JerryG:
Thanks much for the link. This is exactly what I am trying to do. I hadn't heard of this company before so this helps.
Larry

 

[TSL]

Boy was I mistaken when I assumed that this would be a simple question! I really appreciate all of the input. So far, JJ's suggestion about the divider valve seems like the best way to go. I had another thought last night: A closed center circuit powered by a 12 volt DC pump which would run only when one of the electric valves has been activated. Pretty sure it would work but not sure how long it would hold up or if the cylinder action would be fast enough. I imagine that this would be similar to a hydraulic RV leveling system or the system on my pickup snow plow. Any thoughts?