Hello, new to the form. I have a cat 305cr i installed a thumb a few months ago, I had it operating at 3000psi and it was damaging the thumb. To turn it down I had to add a relief valve instead of the "shutoff" valve. The thumb valve had 2 shutoff valves in it. so if they were not seated in and operating at 3000 psi the thumb would fall on its own weight. I bought 1 relief valve form cat $700... now it stays where i want it but it pushed out of the way to easy, i have to hold the pedal down for it to hold anything. I would like it to stay where i position it and push out of the way if i curl the bucket to hard, is this possible? The one on the right is a "shutoff", this is the thumb valve. The left one is a relief valve, this is what i added to the system on the down side of the thumb. My cat dealer is useless, i am going to be buying a new macing next year and probably wont go with them just because of there terrible service at my local dealer.
It sounds like the relief pressure needs to be adjusted. Technically you're not supposed to adjust the pressure without gauges because you can risk damaging something if you set it too high. With a gauge on the circuit, loosen the lock nut then tighten the hex screw a 1/4 turn at a time until you get the desired resistance on the thumb.
I see you live in CT, as do I. HO Penn is ok, but go with FW Equipment which is Case, Kubota or go with WI Clark, Deere
I have gauges and that's how I set it. The operating pressure and relief pressure are different. If I set the operating pressure so the thumb operates at a reasonable speed without beating itself the relief pressure is to low. So I guess I have to operate the thumb carefully so it relieves where I want it to. The smaller equipment guy at ho penn. Is a down right piece of garbage. I'll never buy any more equipment from them because of his support. I'm looking at Takeuchi.
You need a flow restrictor. I had the same problem with the thumb I put on my 1.5 ton. It would slam open and shut. I went to my hydraulics guy and explained the problem. He gave me what looks like a set screw with a 1/16" hole down the middle. I tapped it into one of the fittings on the push side of the hydraulic ram circuit and the problem is resolved. Go to a hydraulics shop, not the dealer for this one.
This sounds like a good idea, i will measure up some lines and go to the hydraulic shop. where did you install the restrictor? at the thumb or closer to the valve? Thanks for the help, i will keep yall posted
I installed it in the 90 degree elbow that's fitted to the push side of the cylinder. Tap some threads into the fitting, screw in the restrictor, and put everything back the way it was. The restrictor LOOKS like this: http://ecx.images-amazon.com/images/I/41TOYascJKL._SL500_AA300_.jpg with the exception that there's a pin hole down the center of it that allows the oil to pass through. It shouldn't be an expensive fix.
thanks, i have seen them before, i will pick one up tomorrow, then just set my golden relief valve to a good pressure so i can still hold stuff with the thumb. I wish i could get my hands on a service manual so i could understand the system, then this would have been so much easier. Cat wants $800 for a manual..
You don't need to buy the whole service manual. Cat sells individual sections. Buy the hydraulic portions.
Matt, I work in the Marketing Department of H.O. Penn. We strive to provide excellent customer service and am sorry to hear you have had an unpleasant experience with our dealership. If you would please call me at 845-437-4176 I would like to see what we can do to correct the situation.
I will look into getting some sections of the manual then. It is still ridiculous... Every other piece of equipment I have the dealer just gave me the manuals or at least access to them. No local supplies have the restricter valves you screw in, i got a adjustable one but it is to big to install. I will order some online and let you know how it works. I really need to get another pressure relief from CAT but at $700 its tough, This is the first time I have seen a machine without the valves when it rolled out the the factory.
are the John Deer 50ZTS the same machine? I am wondering if i could try to get the valve from john deer.
Did you ask your product support man about the reliefs? We bought a new 446 Cat backhoe and Cat had totally forgot the swing reliefs. If you swung full speed at full extend and let go of the lever, the swing line under the cab would explode. They replaced it 3 times before they figured out the issue. We've had 5 Cat mini's and every one had the reliefs installed from the factory.
Hi Matt, I know this thread is old but I am hoping you are still using this forum. I have a Cat 304CR on which I just added a thumb. My Cat has the shut off vlaves and the relief valves that you show in the picture on both sides of the valve (inside and outside). I had the same problem you did. At "stock" pressure, the thumb wanted to beat itself to death. So, with a gauge, we turned the presuure down on the right had valve (shut off valve) from the "stock" 3700 PSI to 1750 PSI (thumb has a maximum pressure of 1800 PSI) since we were not aware that the left valve was a relief valve for the thumb curcuit. Thumb works a lot better now. Although, as you mentioned, the thumb falls open under its own weight now. Did you get your issue solved? Should I have left the right hand valve where it was and adjusted the left hand valve to 1750 PSI? Did you try the "restrictor"? Thanks for any advise you may be able to offer. Don