Grapple hydraulic issue

[Bingo8]

Newbie here. I just had new hydraulic hoses put on my stout grapple bucket. The bucket also had a kink in the grapple that I had straightened. Here is the issue, once I recieved it back and went to use it for first time, the grapple will barely open. I step on foot control (Case 70XT) and only one side of grapple will open at a time and at a snails pace. Once left side is open then right side starts to come up..again very slow. Same thing happens when closing. Worked fine before new lines put on and they unhooked lines to cylinder to straighten it. Now I did not run any fluid through new line before hooking it up so Im wondering if it could have air in it? I just dont know much about it. Any ideas to get me going would be appreciated. Thanks

 

[SkidRoe]

Could be air, but that should have cleared after the first few cycles. Sounds more like a restriction to me. Maybe check your new hoses to make sure there are no blockages in them.
Also, it is some what normal for one grapple to open before the other, as long as they mover freely. Since there is no flow divider between the two cylinders, the fluid will always flow the path of least resistance. One arm will have less friction than the other, so it will go to that one first.
Hope this helps - SR

 

[Bingo8]

Could be air, but that should have cleared after the first few cycles. Sounds more like a restriction to me. Maybe check your new hoses to make sure there are no blockages in them.
Also, it is some what normal for one grapple to open before the other, as long as they mover freely. Since there is no flow divider between the two cylinders, the fluid will always flow the path of least resistance. One arm will have less friction than the other, so it will go to that one first.
Hope this helps - SR

The guy who built the new line used 1/4" hose. I think the old hose was 3/8". Will that make a difference in how fast it opens?

 

[SkidRoe]

The guy who built the new line used 1/4" hose. I think the old hose was 3/8". Will that make a difference in how fast it opens?

It certainly could. While the hose may be 1/4" ID, the end fittings have much smaller ID's than that.
If both hose end fittings had a 0.060" wall interior barb, which they well could, you would be reducing the flow area by a factor of 4.
In order to get laminar flow through a system, pressure lines should be sized to keep the flow speed below 15 ft/s.
If your machine produces 16 GPM, with 3/8 hose, you would get a flow speed of 8.7 ft/s, which is okay. Reduce to 1/4" hose and your flow speed goes up to 34.9 ft/s. This flow will be very turbulent and restrictive.
Also keep in mind that the flow is bidirectional, and return lines should be sized to keep the flow speed to less than 8 ft/s, to avoid cavitation.
Based on this, I would say that 3/8" hose is the minimum size that should be used, especially when you consider the area differential of the cylinder and the fact that a retracting cylinder generates a higher return flow than on extension.
FYI - The grapple on our Bobcat 773 runs 1/2" hose.
Hope this helps - SR

 

[SkidRoe]

The guy who built the new line used 1/4" hose. I think the old hose was 3/8". Will that make a difference in how fast it opens?

Hi Bingo8,
I just googled the aux flow rate on your machine - it is 21 gpm. That makes things even worse.
Cheers - SR