Hydraulic thumb

[ridefst]

Thank you very much for the photos and measurements Topstrap.
Looks like your thumb is about the same size as my original, but your excavator is about half again larger than mine (8,000lb vs your 12,000), so I think I probably overshot a bit.
Think I'll try another cardboard alligator, but maybe something like 28" long thumb, see how that works out.
Do you think it would be a real problem if the thumb was a bit shorter than the bucket at full extension? Doesn't seem like a big problem to me, would make the overlap less when curled, and would still give a couple inches clearance to the boom when the dipper is pulled in tight.

 

[Topstrap]

I really don't think the length is super important since you very seldom use it to grab things that are so small that you'll worry about not reaching your teeth with the end of the thumb. I kinda compromised between open and rolled up. I wanted mine to swing way down since I work around houses and close quarters a lot and didn't want to have to extend the boom way out to be able to get the thumb down far enough to pinch things between it and the bucket. This way I can still have the bucket in close to me and swing the thumb down far enough to still pinch concrete/timbers/brush or whatever. A thumb that don't swing down far enough needs to have the stick out to get the right angle to allow the bucket to pinch items to the thumb.

I'm sure mine could be improved on with someone with some good math skills but I just played around till it looked about right and welded it up.

Good luck on yours, if you are like me though we do tend to sometimes overdo things but I didn't want to have to worry about it bending or being torn up from use.

Topstrap

 

[ridefst]

Well, it's been quite a while since I started this thread; but this morning I finally finished it.

I've had the steel cut out for a month or so, but the only welder I had was a little 110v Lincoln MIG. Nice welder, but completely out of its league with 1/2" steel.
I decided that a stick welder was the way to go; mainly because I can't afford a big MIG (and don't need one most of the time)
Looked at some Lincoln buzz boxes, but ended up with a new Everlast inverter-based welder. 200amps, weighs about 30lbs, DC, works very well so far.

Tacked everything up with the MIG and ran the hydraulics around a bit; seemed to be in the right spot and lined up, so I welded it all solid with the stick (no welds across the dipper though, heard that was a no-no)
Used Cat II toplink pins to hold everything together.
They're just clipped in at the moment, but I'll probably go back and weld a few of them solid for strength.

Got it all welded up and took it out to test it.

Seemed to work great with the little stuff; now it's time to see if I can break it

It was all the hoe could do to lift this log up, had to keep it as close as possible so it wouldn't tip over, but it worked great.
Carried it a hundred yards to add it to the firewood pile.

Checked everything out after that, nothing bent/cracked/etc so I think it'll hold up for quite a while.
Easy to adjust with the toplink, and two pins will take it right off for dirt work.