I want to fabricate a hydraulic thumb for my Case 580SK. I was planning on putting quick connects on the Extendahoe and using those for the hydraulic feed. I was talking this through with a friend and he said that the bucket pushing against the thumb (weaker cylinder) might cause some kind of hydraulic back-pressure and destroy my pump. He said I might need to install some kind of in-line pressure relief valve or diverter... While I understand the issue, I have no idea of what or if I need to do this, and any suggestions on cylinder sizing. If anyone can help me with this, I'd sure appreciate it. Cheers!
The valve section for the extendahoe should have two port plugs, you can purchase the circuit relief kits the same as used in the bucket section and just swap them in place of the plugs, may have to adjust them a bit to make both functions happy. I believe the new part number is G109449. http://partstore.casece.com/us/ASCOEQ-Branch15/parts-search.html#epc::mr100583ar1099633 http://partstore.casece.com/us/ASCOEQ-Branch15/parts-search.html#epc::mr100583ar1099138bi1411692
Hey lantraxo, Thank you very much for this. I've been toggling back and forth between the parts diagrams/links you sent, and have a few questions if I might. Which plugs do I replace? If you could refer to the numbers in the parts diagram, it would make it way easier for my little mind. Do I require two of the parts you mentioned or are there two in the kit, or is it linked somehow? Does the relief valve act as some kind of bypass and feed fluid back in... I'm still learning... Thanks a lot!
Sorry, the plugs are #16, the assembly number is the line above, #G33122. Same with the reliefs, the valve number and replacement kit number are shown above line 16 on that page. I don't know about the kit, I would think you need to order two, but you could call your CASE dealer and ask I suppose. It's not called out very clearly. The port reliefs open when pressure on that port connected to the cylinder rises above the setting, passes oil to the return passage in the valve stack and back to tank, There are some check valves in there that will most likely allow oil to fill the other end as the cylinder moves. It is possible to only put a relief in the port for the butt end of the cylinder, as typically force is always applied to push the thumb back into the cylinder, but there is always the risk of the thumb getting snagged on something or someone hanging a chain on it, pulling the cylinder rod out and creating high pressure on the rod end of the piston. If it was me I would install both reliefs. Cheers
Hey lantraxo, Once again thanks! This really helps and I appreciate it. Getting a thumb on the hoe will really be a help. Cheers, a
Ooops... I forgot... One more question please - what size cylinder (bore) would you suggest? The thumb is going to be about 36" long. Which should be just shy to reach the end of the bucket when in "grabbing" position... My BH is a Case 580 SK. Cheers, a
Don't really have any exact advice there, as a rough rule of thumb I would suggest about the same bore and rod size as the bucket cylinder, certainly not smaller. You kind of have to do a balancing act for length, figure out how far back you can mount it, then how much stroke you can get and still have a decent lever length which sort of decides where your rod end pin goes on the thumb itself. You want it so when the thumb cylinder is fully extended the thumb is as close to the bucket as you can get and still have the cylinder tube not hit the arm as the thumb comes around the end of the stick. I usually weld the rear mount on last so you can cheat it back and forth a bit, and if you need to you can pull the cylinder apart and put a spacer tube between the piston and rod gland to stop it from going too far. The spacer tube is actually a really good thing if you have room for it, it keeps the rod and piston from tilting and jamming in the bore when the cylinder is all the way out and you curl the bucket back against it.
I was looking at doing this on a super k also. correct me if I am wrong but the super k aux ports t off of the extendahoe lines. when you use the aux lines you pin the extendahoe dipper stick together. or at least that's how ours is set up. Lantraxco are you saying all the valves are the same and the only difference is the use of a adjustable releife valve or not? Just wondering cause I am thinking of adding another valve in the stack to use as an aux valve but want the adjustable relief for a thumb operation. When I reasarched it usa attachments has this thumb http://www.excavatorthumb.com/ht1035-hydraulic-excavator-thumb.php I dont think I could make one for this price when you add time to fab. Shipping included. This is the size they recomend for a 580 sk. At very least should give you some sizing to go by if you do decide to build yourself.
They're not all the same, I would suggest the bucket or arm valve section if you can find one, those two have the reliefs in them without any extra or odd valves. The extender/aux section is the same as those two except it comes with plugs in place of the port reliefs.
Thats kind of what it looked like to me when I researched it. Still wasent to sure. Of course I will have to make longer through bolts and rig up a lever or foot pedal. When we had all the covers off for other maintenance I looked at that and it didn't look like it would be to hard to fabricate another foot pedal for the opposite side as the extendahoe pedal. Also I think there is one steel line that will need to be extended. Other than that the hard part is going to be finding a used valve for a reasonable price.
Might find an old stock surplus section somewhere, never know.
You've got me wondering if your route is the better one... did you ever find a valve section for a good price?
Oh i can find them but they may as well be gold plated for what they want for them! called case dealer and the aux kit is no longer made for the super K. even if it was the valve as much as I don't like the price is still the cheaper way to go. I think the aux kit was made by a company in Wichita but darned if I can remember their name.
What kind of prices are you seeing? I have no idea what stuff costs for these things... Cheers.
Workshoprat, are you an operator? Just a heads up, an experienced operator that is familiar with running an extendahoe might have trouble moving the right pedal. They will obviously get used to it, but I wanted to mention it so you wouldn't be caught off guard.
Sorry I should have said opposite side OF the extenda hoe pedal. meaning put new pedal on the LH side to become the thumb pedal. Yes I am an operator. I know what you mean by getting a brain set. I learned on cat two stick loaders. had a fiat loader that the levers were all reverse from cat and it screwed with me something horrible. Just like my first hoe was a ford 4 stick. cant operate a case three stick to save my life. everything is all in the wrong position.
anywhere from $700 - $800 for a used valve. the aux kit is around $4K. the valve is by far the cheaper but not as cheap as id like LOL.