Hello, first post here but I've been following along for a while. Very helpful forum!
I recently installed a hydraulic thumb on our 2000 Cat 302.5 (4AZ01260) and have been reluctant to use it yet because I think we need to incorporate some form of relief into the system to avoid having the bucket overpower the thumb and damage the thumb equipment. I've read through various threads on similar topics, but a lot of them seem unresolved and I want to try and get some additional input.
Here are the options I'm looking at:
1. Purchase two Cat p/n's 140-5605, VALVE AS, which I believe are overload/relief valves, per our parts manual. I read through Cat Special Instruction GEBI0248-02 ( http://64.22.192.186/CWT/groups/public/documents/special_instructions/cwt009971~2.pdf ) and as part of the installation procedure for mounting hydraulic thumbs on Cat mini's, it says to install relief cartridges with the p/n's above. This machine already has (5) of these same cartridges used in the main valve block, but did not come with any for the aux. hydraulic circuit unfortunately. Even worse, to buy these cartridges new, it looks like they're nearly 700$ a piece from the local Cat dealership. This is a little steeper than I was hoping since our machine is just used for home/farm purposes, so I'm interested in other options as well (including finding those parts used).
2. Purchase one generic relief valve ( https://www.surpluscenter.com/Hydra...0-3000-PSI-Relief-Valve-RV-H4-9-6135-50-H.axd ) and plumb this into the hydraulic line that acts to close the thumb against the bucket, with the relief plumbed into a hose/line that returns back to the hydraulic tank. With this valve only costing $50, this is clearly a lot more affordable, so I'm very interested in determining whether or not this configuration achieve the results I'm looking for. I haven't determined exactly where I would place this valve or how I'd manage the plumbing, but I've seen other threads on here that determined it was likely doable. I think it would certainly cost less than the 1400$ required for the two relief cartridges above.
The only thing I'm trying to do is protect the thumb cylinder so when you curl the bucket in against it, the thumb would retract by the pressure of the bucket rather than bending the thumb cylinder or causing other damage. I find it unlikely that damage would occur in the other direction, so I don't think I need relief on both sides of the thumb. With that being said, I have only a basic understanding of hydraulic systems but am very mechanical. This is something I'm more than capable of doing myself, with the right input from knowledgeable individuals to make sure I don't get myself into trouble.
Please let me know if you have any recommendations or experience doing this same thing. I would greatly appreciate other perspectives on this. Thank you!
I recently installed a hydraulic thumb on our 2000 Cat 302.5 (4AZ01260) and have been reluctant to use it yet because I think we need to incorporate some form of relief into the system to avoid having the bucket overpower the thumb and damage the thumb equipment. I've read through various threads on similar topics, but a lot of them seem unresolved and I want to try and get some additional input.
Here are the options I'm looking at:
1. Purchase two Cat p/n's 140-5605, VALVE AS, which I believe are overload/relief valves, per our parts manual. I read through Cat Special Instruction GEBI0248-02 ( http://64.22.192.186/CWT/groups/public/documents/special_instructions/cwt009971~2.pdf ) and as part of the installation procedure for mounting hydraulic thumbs on Cat mini's, it says to install relief cartridges with the p/n's above. This machine already has (5) of these same cartridges used in the main valve block, but did not come with any for the aux. hydraulic circuit unfortunately. Even worse, to buy these cartridges new, it looks like they're nearly 700$ a piece from the local Cat dealership. This is a little steeper than I was hoping since our machine is just used for home/farm purposes, so I'm interested in other options as well (including finding those parts used).
2. Purchase one generic relief valve ( https://www.surpluscenter.com/Hydra...0-3000-PSI-Relief-Valve-RV-H4-9-6135-50-H.axd ) and plumb this into the hydraulic line that acts to close the thumb against the bucket, with the relief plumbed into a hose/line that returns back to the hydraulic tank. With this valve only costing $50, this is clearly a lot more affordable, so I'm very interested in determining whether or not this configuration achieve the results I'm looking for. I haven't determined exactly where I would place this valve or how I'd manage the plumbing, but I've seen other threads on here that determined it was likely doable. I think it would certainly cost less than the 1400$ required for the two relief cartridges above.
The only thing I'm trying to do is protect the thumb cylinder so when you curl the bucket in against it, the thumb would retract by the pressure of the bucket rather than bending the thumb cylinder or causing other damage. I find it unlikely that damage would occur in the other direction, so I don't think I need relief on both sides of the thumb. With that being said, I have only a basic understanding of hydraulic systems but am very mechanical. This is something I'm more than capable of doing myself, with the right input from knowledgeable individuals to make sure I don't get myself into trouble.
Please let me know if you have any recommendations or experience doing this same thing. I would greatly appreciate other perspectives on this. Thank you!
