Aux Hydraulics Jerky on Grapple Attachment

[Jim Miller]

I'm new to Bobcats and I need some help. I have a S160 with 70hrs and just bought a Armstrong Ag rock bucket grapple with single 2x4 cylinder. I got it connected with no problems - but it seems the grapple cylinder is really jerky. I can move the switch about half-way from center and nothing happens then the cylinder will jerk open or close abruptly. If I really take my time and move the switch super slow, I can get it to not jerk open - but I'm talking about moving that toggle switch very - very slowly. (up and down is the same). When I'm trying to clean up brush, I don't think I'll have time to gently and slowly push that switch. Is there an adjustment on the amount of hydro pressure for the aux. function?? Is there a flow restrictor that would help to not make the cyl open or close so fast??

 

[SSdoxie]

Jim, The S160 has front Auxiliary flow capable of 19 GPM @ high (max) throttle. A 2" cylinder is going to move very fast with that high of flow. No idea what RPM you are running at, but idling down brings the flow speed down but idling to low affects the proportional affect of the thumb switch. Thumb switch controls a metering valve to allow pilot pressure to shift the control valve spool and too low of RPM could reduce the pilot pressure so the switch has to be moved much farther before enough oil/pressure can start shifting the control valve spool. What I am saying is that cylinder is too small, for the rated flow of the machine, to work decent without adding some type of flow restriction to the grapple.
First try reducing the hose size down to 1/4" and if that doesn't meet your needs add some type of inline restrictor.

 

[Jim Miller]

SSdoxie - Thanks for your reply. I am running the S160 at idle and didn't even think about increasing RPMs - thought that would just make things worse. The dealer that sold me the new grapple is coming out this Thursday afternoon with a set of flow restrictors to see if that will make things slow down. I'll let you know what happens.

 

[Jim Miller]

The Armstrong Ag dealer came out with a set of flow restrictors with a 1/16" hole. I didn't realize that there were already 1/8" restrictors in the lines because I didn't know what to look for. When he changed the restrictors out - WOW - mage all the difference in the world! The grapple arm moves smoothly in both directions. Even though I haven't had a chance to use the attachment yet - I have enjoyed playing with it!

Problem solved!!

 

[Xfaxman]

The Armstrong Ag dealer came out with a set of flow restrictors with a 1/16" hole. I didn't realize that there were already 1/8" restrictors in the lines because I didn't know what to look for. When he changed the restrictors out - WOW - made all the difference in the world! The grapple arm moves smoothly in both directions. Even though I haven't had a chance to use the attachment yet - I have enjoyed playing with it!

Problem solved!!

Is it just a flat washer with a 1/16" hole, that drops in where the hose screws into the coupler?

We need some pictures of the grapple in use, here: Grappling fun - A Picture Thread.... - Page 7

 

[Industrial Toys]

I had the same issue with my grapple. It was controlled electrically with a toggle switch atop the joy stick. Way too jerky. I took some fittings apart on the grapple itself, (not the machine Aux, hydraulic circuit) and put in a flat steel disk, into which I had drilled a small hole. Think I had to experiment with different hole sizes to get it right, but it's been perfect ever since.

 

[Jim Miller]

Before the Armstrong Ag dealer came out, someone told me how to fix the problem (even though I don't think this is legal). Take two dimes and drill a 1/16" hole in the center of each. Remove any shavings or burrs and then insert a dime in each quick disconnect fitting. See if that has fixed the problem, depending on how fast the grapple is moving - you may need to make the hole larger or smaller. Either way - it won't cost very much. Again, it may not be legal to deface US currency.