Cat 227FB (converted buncher) hyd thumb install

JMR-TBAY · Apr 17, 2022

John C. said:
We always used the half circles like your first photo shows. The reason is that when the thumb is pulled back it slams into those stops and wear a matching groove in the linkages. I've seen plenty of machines with the single sitting in the center which hits the eye of the thumb cylinder rod and over time it makes a mess of the rod eye. The setup in your second photo looks good but uses a lot of steel and welding.

The semi circle rest would press against a beefy piece of linkage, not the cylinder end. It could be made out of 1/2” or 3/4” plate steel. Oh and for clarity, I’d fab 2 pieces, like the first photo.

Option A (wedge shaped stop) seems like it would be a little simpler to fab, and much beefier. Could use 1” steel to match what it would press against on the thumb. It would be about 1” tall on the short size and 2” tall on the long side and about 6” in length.

With either I’d try to attach some conveyer belt rubber as an added cushion.

My only concern with option A would be the cantilever effect it would have on the main pin. The lower the rest is to the fulcrum, the more force that will be cantilevered against the main pin when the thumb is stowed. Not sure if that’s a realistic concern or not.

John C. · Apr 17, 2022

The stops and saddles are installed to keep the cylinder from hitting the stick when the thumb is in the stowed position. It really doesn't matter which way you go.

JMR-TBAY · Apr 17, 2022

I quickly mocked this up with cardboard. I’ll aim to have it made with 1” plate. I’ll be using two pieces…one on either side of the cylinder welded directly to the stick.

JMR-TBAY · Apr 18, 2022

For anyone else in a similar position, here is a cost breakdown of some things:

Mobile welding quote (cylinder mount only) - $1000 to $1250 CAD
Hydraulic lines/fitting/crossover relief valve - $1000 CAD

JMR-TBAY · Apr 23, 2022

I got the thumb stops back from the machine shop. Not bad for $50CAD I’d say.

I got holes threaded so I can bolt across each stop pieces of conveyer belting rubber as a cushion.

Then I can get rid of this monstrosity. Seems awfully excessive. A lot of unnecessary welding.

spitzair · Apr 23, 2022

That looks like it should work perfectly!

JMR-TBAY · Apr 29, 2022

Not sure how long the rubber will last, but this should help cushion the thumb at rest.

Hydraulic hose order came in. Spent some time installing nylon sleeve with zap straps. I saved about $75 by not having discounthydraulics install it. Just ordered a couple sizes larger to ensure it would slide over the fittings.

John C. · Apr 29, 2022

The rubber is a nice thought but won't last long depending on the operator. The linkages seem to pick up speed as the thumb is pulled back.

JMR-TBAY · Apr 29, 2022

John C. said:
The rubber is a nice thought but won't last long depending on the operator. The linkages seem to pick up speed as the thumb is pulled back.

It appears as though the thumb cylinder is hydraulically cushioned. That should help.

Got the lines routed and hooked up. I’m not sure if the crossover relief valve will actually add any protection with a double acting cylinder, but I installed one none the less.

I cycled the thumb cylinder back and forth a few inches and the circuit seems to operate how it should. The cylinder is drifting out though (opposite of gravity) Not sure if that’s from air in the system, or if the aux valve needs a rebuild.

JMR-TBAY · Apr 29, 2022

spitzair · Apr 29, 2022

Could it be that the lines are hooked to a valve that on a buncher might have been set up to constantly apply some pressure to say for example hold the grapple on the cutting head shut so as not to lose grip on a tree? Just a thought, I really don’t know anything about feller bunchers…

JMR-TBAY · Apr 29, 2022

spitzair said:
Could it be that the lines are hooked to a valve that on a buncher might have been set up to constantly apply some pressure to say for example hold the grapple on the cutting head shut so as not to lose grip on a tree? Just a thought, I really don’t know anything about feller bunchers…

I don’t believe so. It should be a standard 6000 series Husco valve with an open center.

Additionally, drift happened in the same direction even after crossing the lines. That leads me to believe the same pressure is present in each line, but the large end of the cylinder overpowers the rod side.

Or air in the circuit is causing funky things.

JMR-TBAY · May 3, 2022

Got everything welded up. My brother helped me out with that. He did 3 passes.

Unfortunately the drifting issue is more severe than I thought. The thumb falls only a little slower than when activated. It drifts with gravity, so with the stick fully extended, the thumb also won’t stay clamped tight to the bucket.

Either the ram seals or a worn valve spool I suppose.

John C. · May 3, 2022

Most thumb cylinders were built extremely cheap. I know of one cylinder builder who did the cylinders for a local thumb and attachment builder. I knew this guy built the cylinders and so I asked him what the deal was. He told me the attachment guy wanted a cylinder for $1,500 and no more. Cylinder guy told him it wouldn't be good. Attachment guy said that is what he wanted so that is what got built. On the cylinder I was handling, he gave me a heck of a deal so I have been recommending him for years. The attachment builder, not so much.

JMR-TBAY · May 3, 2022

John C. said:
Most thumb cylinders were built extremely cheap. I know of one cylinder builder who did the cylinders for a local thumb and attachment builder. I knew this guy built the cylinders and so I asked him what the deal was. He told me the attachment guy wanted a cylinder for $1,500 and no more. Cylinder guy told him it wouldn't be good. Attachment guy said that is what he wanted so that is what got built. On the cylinder I was handling, he gave me a heck of a deal so I have been recommending him for years. The attachment builder, not so much.

I spent a couple more hours before dark messing with it. Turns out the cylinder appears fine. I swapped the output lines to the other spool on the aux valve. No drifting and the cylinder feels strong. This works well because this spool has port relief valves. I’ll work on setting those later.

A small issue appeared with the other lines I attached to the leaky spool. These lines run to a valve used in the swing circuit, and I believe the small amount of flow is causing the swing brake to not activate. Should be an easy solution by just capping the lines and spool ports.

JMR-TBAY · May 3, 2022

I’m slightly disappointed with the speed of the cylinder. I used 5/8 hose. I was actually recommended to use 1/2”. I think 3/4 would have been better, but oh well.

The hydraulic cushioning on this cylinder works very well!

uffex · May 4, 2022

Good day
Nice to see the use of the photo's documenting the installation.
Kind regards
Uffex

John C. · May 4, 2022

I had forgotten that your machine was a logger. There would be an extra valve for a rotation circuit to make the grapple turn either way. It would likely have a motor spool in it. Maybe you could check to see if you hooked into that and not the grapple open and close circuit.

JMR-TBAY · May 4, 2022

John C. said:
I had forgotten that your machine was a logger. There would be an extra valve for a rotation circuit to make the grapple turn either way. It would likely have a motor spool in it. Maybe you could check to see if you hooked into that and not the grapple open and close circuit.

I think you hit the nail in the head, John.

The “leaky” spool is for the tilt circuit. I didn’t clue in that could be a hydraulic motor. Would make sense. That circuit also had line locks as indicated in the shop manual, although they were deleted on my machine.

The spool I’m now using was for the tip circuit.

I had started another thread specifically for the Husco aux valve.
https://www.heavyequipmentforums.co...ut-this-husco-valve.94179/page-2#post-1041226

14 hours later the cylinder has only drifted about 2”. Should be good enough for my use.

Cat 227FB (converted buncher) hyd thumb install

JMR-TBAY

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John C.

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