Homemade Articulated Mechanical Thumb

[dfkrug]

Too bad I can not see the video. Glad you got it all working.

What was the electrical problem?

 

[3RRL]

So I had to fix the Thumb and straighten out the bent links and jaws. While Larry decided to completely redo my electrical system ... (he installed an automotive fuse box and repaired several switches and connections) I went to work making additional 3/8 x 2" stabilizer bar to brace the jaws.



I also had some 3/8 x 1" bar stock that I cut to the length of the linkage. Then welded them on top of the linkage to make them like "T" beams. After completing that repair, the jaws and linkage were super strong. It was actually fortunate to test it to failure so I could make the improvements right there at camp. Now I know what to avoid and the limits of the mechanical thumb.

 

[3RRL]

Dave,
Sorry you can't see the videos, they are pretty neat.
The electrical problem was a bad ground from the battery cable to the frame. My bad because I measured 12.7 volts through the ends of the cables and everywhere I checked. But Larry checked it under load and the voltage dropped to zero. So he knew right away there was a faulty connection. Then he went to work on the rest of the electrical and did a super fine job.

 

[3RRL]

Now it was time for me to try out the thumb again. It had been raining so it was hard to get the welded areas primed and painted again, but there was enough time to do it after all.
Here I am getting ready to try it out again.



At last, success. The mechanical thumb was a lot stronger than before. In fact, I could dig dirt and pick up rocks with it. This video shows how this basketball size rock is squeezed into the bucket!! I had to tamp the bucket down to dislodge it.



After I got it out, I picked it up again and tossed it out of the way. Now I'll be able to do some serious rock moving.



Thanks for looking,

 

[HomeBrew2]

Howdy neighbor Rob!

Ditto what dfkrug said.

The way I test a thumb is to grab onto a seemingly dead 2" california blue oak branch about 5' above ground ... ya know, to clean the tree out. Give the machine half throttle and prepare yourself to yank the seeming dead branch to the burn pile while enjoying your due glory. Once you recover from the entire front end of tractor going 2' into the air (seemingly dead limb not dead), asymetrically, thus torquing the thumb somewhat, backoff the gas! At that point, you evaluate your BH thumb design. Mine passed the test with only about 1/2" twist. After 1 year of use, a brutal year, I straightened it with a short handled 8# hammer and painted it (primer). Oh, the stately baby Kubota BH seemed to be no worse for wear, THAT was the real surprise

 

[EddieWalker]

Rob,

Great post!! The video is amazing. It really shows how handy that thumb can be moving those rocks. I also enjoyed seeing Larry work your tractor and move those logs around. Real nice to see how easy it can be with the right tool!!!

Thanks,
Eddie

 

[tlbuser]

Thanks for posting the videos. That mechanical linkage thumb is awesome.

 

[dfkrug]

Sweeeet!

 

[3RRL]

Thanks All you guys.
I am soooo glad that it works as slick as it does. I wish for those who can't, ... to see the video's somehow. They are great to see it in action.
Now I've get to work on Larry's project for his rear blade. He's got me making a worm gear box to make his rear blade fully hydraulic. He's got some great ideas.
It's weird, but after posting back and forth for nearly 2 years, you feel like you know him personally. It was great to finally meet each other and get together at camp. He's one of the nicest and smartest man I've ever met.

 

[scott_vt]

Afternoon Rob,
Ive been patiently waiting for those action shots Looks real nifty and how great is it to have an electrial guru from the forum fly out to meet you and diagnose your problems !

Thanks for the great videos and update!