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!

 

[dtd24]

3RRL,
Real nice, you are like the grapple master!!!! I'm just going to follow your lead with projects. I don't know that I can keep up though. Still workin on my grapple for FEL.

My moto: One step by one step

 

[3RRL]

Thanks Scotty and dtd24,
I know everybody was waiting like you guys. I'm just glad it turned out so cool. After testing it out, I have the linkage set just about right for most grabbing and digging work. However, there are the different hole locations available in case I want to vary the amount the thumb opens and have it close faster or slower, depending how much I need to curl the bucket. But this setting seems pretty universal for now.

dtd24,
I saw your progress and you should be just about ready to build in steel after you eliminate that small interference problem. Maybe make the hinge mounts slight higher or cut out some clearance in the arms. You are doing a good job on it and I'll be watching your thread too.

 

[HomeBrew2]

Anxious to see what payload that rig can lift and transport. The attached pic shows my limit and education as to front weighting ... with a baby tractor ... had to drop it and go get a full bucket of ballast to take the pebble to it's new home. I'm still amazed what a bit of geometry and phisics can produce with junk materials and virtually no fab time

 

[tommu56]

Rob why not put video's on YOU TUBE?

tommmu56

 

[3RRL]

Rob why not put video's on YOU TUBE?

tommmu56

tommmu,
I didn't think of it. I have them on Photobucket now. Is YOU TUBE a public viewing domain? It's obvious I don't get out much.

STEVE, my bro...
Whoa, that is one big sucker in your hoe. I'll have to test my thumb on some bigger rocks too, but mine isn't fixed like yours, so it may not be as strong? But that water laden log had to around 1000lbs I would guess. Then again I have the dual bucket grapples for REALLY big boulders. I just have to exercise a little discretion.

 

[tommu56]

Rob

YouTube - Broadcast Yourself.

I've never up loaded but some sent me a link one time

tom

 

[dynasim]

This was a great illustration of how things can be done! Thanks for the education.

One question, and it is a general one, also: Do you have to heat treat the welded areas after completion? I was thinking of welding some attachments to my trailer, and am worried about having a weak point at the welded area.

Chris

 

[HomeBrew2]

Yeh, we all just do what we can do. For the big rocks, I just plow them with the buchet to where I want them ... too much shop time to do the grapple thing.
Hey, we had a bit of snow this week, had some losses from my old-growth cottonwood. Nice to have the thumb so I didn't have to "mud it out" ... see attached. I pinched it in the wrong place and it tried to yank my machine over ... I've pinched the wrong parts before and knew just what to do ... drop it and run before she can grab her gun

 

[Timber]

I so love your projects Rob. I was waiting for this one to be compleated. I don't have a hoe or any intention of getting one so I had nothing to realy add but it was fun to watch you work just the same. As I watch you guys play with the thumb I realize that as adults we never seem to loose the child inside. I see 2 boys and a little girl in a sandbox with a big TONKA truck LOL. You are truly an amizing individual. The vidios are great, I did miss the sound on the last few, is nice to hear the tractor while your working. Looking forward to the next one

 

[3RRL]

This was a great illustration of how things can be done! Thanks for the education.

One question, and it is a general one, also: Do you have to heat treat the welded areas after completion? I was thinking of welding some attachments to my trailer, and am worried about having a weak point at the welded area.

Chris

Thanks again guys,
I'm glad some of you found the thread entertaining.

dynasim,
No, you don't have to heat the welded areas after completion. Letting them cool on their own is generally a good practice. Just don't pour water on them to make them cool faster. Doing that would cause stress and brittleness in the welded area.

Timber,
My Nikon camera doesn't have a microphone, but my wife's Cannon does. So hers are the only ones that have sound. Yes, I love hearing the tractor engine on those.