There is one geometric detail that I think will require an RV on the thumb extend line. There is an intermediate link between the bucket cylinder and the bucket that helps to extend the buckets range of motion. This also helps to maintain a pretty consistent radius of pivot for the bucket cylinder. On the thumb, I don't need that degree of motion so I'll have the cylinder tied directly to the thumb. Because of this, when the thumb is fully extended, the effective pivot radius on the thumb will be reduced to just a couple inches. In this configuration, the bucket cylinder will have a tremendous mechanical advantage over the thumb cylinder, so without a relief in the thumb extend line it would lead to some tremendous pressures to the thumb cylinder. I hope that makes sense.
So the thumb will necessarily be quite weak when it's fully extended. When the thumb is at a right angle to the dipper, then the bucket and thumb will be fairly well matched and the thumb will be at its greatest strength.
I dug through some of the earlier posts and went to the link for the cylinder that I bought. I tried to get the thumb cylinder to be matched with the bucket cylinder. I have to figure out what the cylinder bore is. I also called JD to get the bore on the bucket cyl.
Welded Hydraulic Cylinder Tang 3500 PSI.
Applications: Welded Double Acting Hydraulic Cylinder.
Tube: High tensile honed cold drawn tube.
Rod: High tensile ground & polished hard chrome plated rod.
Gland: Precision threaded gland with wear rings for long life.
Piston: High tensile steel for heavy duty applications.
Base ends: Welded steel tang mounts.
Piston seals: Top quality five component compact seals for excellent performance.
Rod seals: Standard U-cup polyurethane rod seal with inner O-ring, POM-C wear rings and polyurethane wiper.
Warranty: 2 year limited warranty.
Pressure: 3500 PSI
Here's an earlier comment that I posted: "I dropped by the local JD dealer. They were able to look up the bucket cylinder specs. It's a 2 1/4" bore. My thumb cylinder is a 2" bore." 2.0x14x1.25 side ports. Posting this stuff is serving as a nice documentation repository of the technical details, and having more experienced people reviewing things is invaluable.
So the thumb will necessarily be quite weak when it's fully extended. When the thumb is at a right angle to the dipper, then the bucket and thumb will be fairly well matched and the thumb will be at its greatest strength.
I dug through some of the earlier posts and went to the link for the cylinder that I bought. I tried to get the thumb cylinder to be matched with the bucket cylinder. I have to figure out what the cylinder bore is. I also called JD to get the bore on the bucket cyl.
Welded Hydraulic Cylinder Tang 3500 PSI.
Applications: Welded Double Acting Hydraulic Cylinder.
Tube: High tensile honed cold drawn tube.
Rod: High tensile ground & polished hard chrome plated rod.
Gland: Precision threaded gland with wear rings for long life.
Piston: High tensile steel for heavy duty applications.
Base ends: Welded steel tang mounts.
Piston seals: Top quality five component compact seals for excellent performance.
Rod seals: Standard U-cup polyurethane rod seal with inner O-ring, POM-C wear rings and polyurethane wiper.
Warranty: 2 year limited warranty.
Pressure: 3500 PSI
Here's an earlier comment that I posted: "I dropped by the local JD dealer. They were able to look up the bucket cylinder specs. It's a 2 1/4" bore. My thumb cylinder is a 2" bore." 2.0x14x1.25 side ports. Posting this stuff is serving as a nice documentation repository of the technical details, and having more experienced people reviewing things is invaluable.
Last edited: