Backhoe swing cylinder plumbing

BIG1RED9

Member
Hello everyone,

I decided to replace the swing cylinders on my Davis 185. I am using 2 double acting cylinders.

Below are 2 drawings. #1 is what Prince Hydraulics is suggesting. That from the ports on the valve I run 1 hose to the right lower cylinder port and the other hose to the left lower cylinder port. Then run a hose from the right upper cylinder port to the left upper cylinder port. Basically acting as single action cylinders. My concern is that the upper section of the cylinders will be running dry and create issues. Of course I could load some fluid in that circuit.

#2 is what I had originally planned to do. I would use a tee at each lower cylinder port. That one end of the tee would go to the top of the opposite cylinder. Concern or issue is that the upper section of the cylinder will hold less fluid than the lower.

In the case of #2, would the fluid balance out the speed and distance and or is it irrelevant as they are forced to be in sync mechanically? Any other issues?

Thank you,
Don
mvphoto49220.png


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The lower photo is the way I believe you will find most are plumbed. (I know Cat 426's, Case 580's, MF54B's are for some.) Piston end of one cylinder is tied to the rod end of the opposite cylinder. That directly provides hydraulic oil pressure to both cylinders during swing (more power for the swing). The pump will supply oil as needed and the two cylinders will work together even though the rod and piston ends have different displacements.

The upper drawing would only provide direct hydraulic oil pressure to the piston end of one cylinder during a swing, no oil to the rod ends, (as you were concerned with), and would be a weaker swing.
 
Hello, I would have to go with the bottom
drawing. If your cylinders were single
acting the top drawing would work. With
the top drawing all you are doing is
shuttling non-pressured oil back and
forth. Yes the cylinders will move at
slightly different speeds but because you
have them linked they will balance to
give a powered push and pull by both
cylinders in each direction.
DavidP, South Wales
 
Reading between the lines here, I'm GUESSING you are replacing single-acting hydraulic cylinders with double acting hydraulic cylinders.

If that is true, connecting as in the top diagram makes sense, otherwise swing speed will be much lower than now.

Is that what you are doing?
 
Thank you all, I really appreciate the feedback. More clear when discussing it with someone. I have concluded that it would work either way. The top picture would be quicker and have less power. The bottom more power and slower.

Without opening the cylinder to see if the 2 lower ports are drawing and supplying fluid 100% identically. I am guessing that they are. More solid than an external tee. This setup seems to mimic the lower diagram.

Regards,
Don
 
(quoted from post at 20:17:52 02/12/20)
The Original cylinders are double acting and have 3 ports, which is why it wasn't clear to me.

Possibly that had a cushioning circuit tied into the cylinders, some swing systems did.
 

It does have a cushion valve. The cushion valve has 4 ports with 2 routing to the spool valve and 2 routing (1 ea) to one of the lower cylinder ports. The other lower ports cross over to the opposite upper cylinder ports.
 

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