Help with mechanical thumb

   / Help with mechanical thumb #1  

LittleBittyBigJohn

Platinum Member
Joined
Jun 7, 2021
Messages
987
Location
Central Arkansas
Tractor
John Deere 1025R, Spartan SRT-XD 72" zero turn
Morning all,

I got a machine delivered yesterday in preparation for the house build. My brother-in-law has been using the thumb and I need to set it back out of the way but I've never done it. Can any of you give me some info on how I need to configure the mechanism to lock the thumb up against the stick?

Oh yeah, the wife would kill me if she knew I posted that picture of her... She stepped on a snake Saturday in flipflops said she is wearing her muck boots from now on.. She's so excited to get the house built.

20230604_203015.jpg20230604_204340.jpg20230604_204358.jpg
 
   / Help with mechanical thumb
  • Thread Starter
#2  
I got it sorted out yesterday evening. It took me and my wife almost 2 hours. I have blisters and I'm sore this morning.
 
   / Help with mechanical thumb #3  
Mine is sort of like yours. But smaller machine. I have to drop the link off and then pin the bucket to the welded-on bracket. Yours looks similar to mine. Were you able to use the bucket to swing the thumb in place to pin?
 
   / Help with mechanical thumb
  • Thread Starter
#4  
I kept the link attached to the stick and pinned the thumb on top of it.

No I couldn't use the bucket to swing the thumb. The teeth on each fit together and they lock together instead of sliding on each other when the pin is out. I ended up mostly curling the stick parallel to the ground for the thumb to fall open. Then had to use straps and prybars to line up the holes so the pin would go in. It was SO much work!
 
   / Help with mechanical thumb #5  
I kept the link attached to the stick and pinned the thumb on top of it.

No I couldn't use the bucket to swing the thumb. The teeth on each fit together and they lock together instead of sliding on each other when the pin is out. I ended up mostly curling the stick parallel to the ground for the thumb to fall open. Then had to use straps and prybars to line up the holes so the pin would go in. It was SO much work!
I have a hitachi 120-2 with mechanical thumb and can flip the thumb in about 3 minutes. However, mine lines up exactly with the teeth, not in between them, so it's very easy to use the bucket to flip the weight of the thumb once it's unpinned.

If I had to flip it on the machine you have pictured, and the teeth catch, I would take a piece of channel steel or something, and put it over the teeth so the weight of the thumb can still rest on the bucket but not get caught. Even if you have to weld something up. Once you have a method worked out that can use the machine to help, it should be very quick.
 
   / Help with mechanical thumb
  • Thread Starter
#6  
The majority of the work was fighting the slop to get the pins out and back in. Everything is so heavy it was always in a bind. Lots of hammering. The pivot pin on the thumb has more wear than the pin I was moving so the hole in the thumb and the hole to keep it out of the way were hard to line up.
 
   / Help with mechanical thumb #7  
I like JB recommendations. Then you could use anything handy such as a stump, even a trailer with a scrap piece of wood to protect the trailer bed. Anything that will be tall enough and the thumb teeth will not damage just lower the boom to raise the thumb.
 
   / Help with mechanical thumb #9  
On mine, thankfully the hole lines up nicely when it's folded all the way back. Looking at yours, it seems like the thumb is floating compared to the stick, so I can see how that would be a pain. If that was my machine, I'd be welding additional tabs on the top of the thumb that would hit the stick when retracted, and the tabs would line the pin up when the weight of the thumb is resting against the stick. If the machine wasn't mine, I would use a couple pieces of 2x4 on edge between the stick and the top of the thumb to hold spacing, or I'd run a chain all the way around the back of the bucket, over the teeth, and use the curl of the bucket to hold the weight of the thumb, and adjust as necessary by curling until the holes line up.

Bunch of ways to do it, but the common theme is to use the strength of the machine to help you.

I frequently just leave the thumb down but on the highest position when I'm working, it allows you to dig but still have the thumb there if needed, which is nice for the type of work I'm currently using it for. The lower pins are better if doing a lot of thumb work. The higher up you pin, the further you need to reach from the machine to grab something. So the highest pin location is a compromise, not great for digging, not great for thumb work, but it does alright at both. If loading a truck or doing a lot of pure digging, getting the thumb out of the way is nice. Not sure if this was a one time thing for you, or if the machine will be there for a while. If you'll be using it more, it would be nice to get the process so it's quick and not as frustrating for you.

Process for my machine, which should be very similar for yours:

Deploying thumb: configure stick so that it is almost parallel to the ground, bucket will be close to the cab. Bang out the retention pins. On yours, push in some 2x4 blocks or equivalent to hold the weight of the thumb somewhat while you get the pin out. Once the thumb is free, lift the boom, and push the stick out until the thumb falls on to the bucket. Once the weight of the thumb is on the bucket, curl bucket as necessary to line up the pin. On mine, the lower pin of the bar is always connected, and the upper pin is out. I would do this similarly for yours (connect lower pin first), and I would remove the bar entirely when retracting the thumb. If you are trying to line up the upper pin during this step, the weight of the bar will mostly be resting on the thumb, which will make it easier to manipulate by hand or with a small prybar.

Retracting thumb: Use the bucket to hold the weight of the thumb without applying pressure to the pins. Remove the pin from the thumb bar. On yours, I would remove the bar entirely at this step. On mine, the bar folds inside of the thumb teeth, and there is another pin point further up on the stick to hold it in place, and the lower pin where it connects to the thumb never needs to come out. I think that the ratchet strap you have shown will work in a pinch, but is very likely to break long term. After the pins are removed, fold the stick under towards the cab, and boom down, until the stick is close to parallel to the ground. From there you should be able to use the bucket to flip the thumb. This is also the part where additional tabs welded on that hit the stick would be really nice. On mine, once the thumb is tipped, the holes line up fine and you put the pins in and go on your way. On yours, you'll want to check whatever the thumb is going to hit to ensure it's rugged enough, or strap a piece of wood in place that the thumb can hit and hold it mostly at the right height. Once it's mostly folded up against the stick, you can adjust a little from there, or use a chain around the bucket to hold the weight of the thumb and maneuver it to line things up perfectly.

Once you have a process ironed out, it shouldn't be much work to flip it either direction. The key is effectively using the large machine that it's attached to. If I had to flip my thumb without using the machine, I wouldn't look forward to that task.

On another note, looking forward to following your home build. That is a very nice plan you selected, and I can't wait to see how it turns out!
 
   / Help with mechanical thumb
  • Thread Starter
#10  
It's not mine but is in the family. I won't be making this change many times probably. I'm sure the plan is for the thumb to be in the widest position all the time at the farm.

The thumb looks like it's floating but it's got a stop for that position. It looks like it was made to sit just like I have it. There is a tab on the back side of the thumb to hold the thumb bar back against the stick but there is a bit of a gap so it would clang around. I'll find something a little more robust than that old strap to stop the clanging when it fails. I'm mostly loading trucks with driveway shale and going to do a little re-grading around the lip of my pond, so I don't want to fight the thumb the whole time. After doing it the first time I should be able to do better in the future. A lot of the issue is a result of the slop after 5,000 commercial hours. It's in great operational shape but the pins and bores on it are tired and loose. Also the thumb is so heavy there is no way the pin is going to slide unless I get the weight off with the bucket and it's hard to get just right without putting it in a bind the other way.
 
 
Top