We just picked up a JD 50D. It has a hydraulic disconnect and it came with a rock grapple and a digging bucket/thumb. They plumbed the thumb and the grapple jaws off the same circuit so they're both running about 2500psi. Just a guess, I haven't put a gauge on it. The grapple works right but the thumb slams shut. A flow restricter would slow it but that's still too much pressure on a little thumb. How can I put some type of relief valve for the thumb and how would you plumb it. Thanks
I think that pressure is fine, you just need to reduce the volume. I have no idea how its setup but it sounds like a flow control valve would cure your problem. I'd put it in the line that closes the thumb and mount it on the boom out of the way somewhere. But thats just a guess. lol, hope that helps. Anyone with more knowledge is welcome to correct me!
some couplers will accept a screw in restrictor. basically a threaded brass washer with a small hole in it. :drinkup
Normally you would use a "pressure reducing" valve to limit pressure on a branch circuit, if there is a chance of load induced pressure use a reducing/relieving valve. If you try to control speed of the actuator by "metering out" be careful not to intensify pressure on the rod-end, you don't want to trade one problem for another. Check out Sun Hydraulics, they will have what you need, Merry Christmas, Tom
When using a screw in or inline restrictor, it should be pointed into an elbow type fitting, not into a hose. Over time they damage the hose they are pointed at. Pretty much an oil laser beam blasting on the hose.
Is the rock grapple and digging bucket/thumb mounted to the machine at the same time? What controls the aux circuit, buttons on a joystick or a foot pedal? Is the thumb excessively fast in just one direction, or both? Did you check the air in the tracks? (sorry, just had to throw that in there)
Did you check the air in the tracks? (sorry, just had to throw that in there) [/QUOTE] LMAO!!! I have not heard that in years!! My first shop forman told a new guy to go check the air in the tracks on the excavator that was getting ready to go out that afternoon& gave him the tire gauge, i was laying under a truck in the shop changing the oil & just thought i didnt hear him right. probably 10 min later the owner came into the shop raising 9 kinds " WHO TOLD THIS DUMB MOTHER #***^** TO GO CHECK THE AIR IN THE TRACKS" I thought i was going to die tryin not to laugh. that was the last time that was ever used in that shop. Now muffler bearings is a differant story lol
I 'll have to get back to you Willie. I only saw it for a few minutes on Friday. The rest I got from talking to the previous owner and one of our operators.
LoL, you're a lot of help.
I've done this a million times. I put a manually adjustable flow control on the hose that I plumb into the head end of the cylinder and a urethane stop plate on the stick. I think the flow control is a "sun", I could look into it further if needed.
Doh! Too funny, I went to post on another thread and found this one. This summer the operator called me saying the thumb was barely moving. Drove out racking my brain the whole way. Got there and sho nuff, thumb hardly moved. Then I noticed the ball valves used to bypass the thumb cylinder. (Don't ask me why I didn't notice them before) One of the levers was turned a bit, I think he hit it on some branches. Turned the lever and thumb was back to lighting speed. Called the operator and let him know what happened and told him how to use the 'new' flow control......
Been there done that Rob, but on rental machines. That's why now days the first thing I do is remove those handles because they are notorious for getting hung up on a branch and either tearing up the valve or restricting/cutting off flow, either way it's a service call. I get rid of those things. :drinkup
Willie the only reason is cause you cant charge for fixin it!! LOL :drinkup
Well, it's not so much not being able to charge them, it's more that I've got plenty to do already, I don't need a useless "handle" creating more work for me. I can turn that valve on/off as needed with a fit em all, don't need no stinking handle! :drinkup
You could always turn the pressure down at the pressure releif at the auxillary circuit. We have machines with thumbs that also run hammers.
I am assuming the auxiliary circuit is pilot controlled and you have a switch running it. It the past I've used a pressure control valve on the pilot circuit running that function. I used to get them from Hydraulic Industries down in Auburn. I would build a bracket mount for the valve block and install it somewhere behind the cab and run the pilot lines through it. The only extra plumbing was a return to tank for the relief cartridges.