Building A Progressive Thumb

[wolf44]

After looking around and getting prices on thumbs I came to the conclusion that thumb manufactures are on crack. Way out of line on prices. So I started to design and build my own progressive thumb. Here is the steps I have gone thur so for in my design build. First my machine is a Kubota KX-71-3. I started buy taking pictures and getting dimensions of the stick and the connection links and the pin sizes. One of the problem that I began to notice when I started looking at thumbs was that they were either to small or to large or they welded on and had poor travel amounts. My other excavator is a Cat 312-CL with a hydraulic thumbs which has always irritated me that the thumb travel was less than I would like, so when I got the little mini I was determined not to have that problem.
The first thing I did was make cardboard cut outs of the stick and the bucket and the control link and the H link and to work out the travel and the pivot positions. after the card board cut outs I made aluminum mock ups to test and refine the pivot positions and linkage shapes and thumb detail. Then on to the solidworks cad program to design the part for flame cutiing.

 

[wolf44]

More on the design -build

Just got the burn outs in today. A little explanation on my thumb design. I have a 24 inch bucket and a 12 inch bucket. if you have a wide thumb you can not dig past the bucket pivot without removing the thumb so I have designed a bolt on tine attachment to the center 2 tine thumb when needed.
I still need to make the pins and machine all the pivot points but it is a start.

 

[wolf44]

H Link

Still in Solidworks but going to Surfcam for G code and the machining center next. I added a picture of the little beast.

 

[td25c]

Looks like a good plan wolf44:thumbsup Keep us posted on the thumb project.

 

[upnover]

Looks like you have thought this out well. You are right on with the pricing of some of this stuff but keep in mind cost of overhead, labour, mark-up, shipping, distributor and all the other costs of what goes into making a product. I built some snowmobile tie down clamps (Superclamps) several years ago for exactly the same reason. By the time I had all the pieces flame cut and I welded it up I saved about 70% of what buying in the store cost plus I had the satisfaction of doing something productive.

Cant wait to see the finished product!

 

[csquared]

hate to ruin your parade, but your design sucks. that thumb will stink for picking up logs and rocks with out any curve

 

[tylermckee]

Looks like some top notch work you do, but i think i agree on the curve of the thumb, If it were mine i would want some curve in the tines, but I'm assuming you have a reason for going with that design

 

[wolf44]

Design Issues

There is more hook than it appears. The teeth on the bucket and the thumb have apposing angles. This design is a test run for modifying my 312 thumb.
If it works as planned great, if not I will modify it.Half the fun of doing this.

 

[N.B.CONCRETE]

Man thats some mad skills .:drinkup

 

[mitch504]

hate to ruin your parade, but your design sucks. that thumb will stink for picking up logs and rocks with out any curve

I built thumbs for my backhoe and then my 45,000 lb. trackhoe and have been using them for better than ten years on several machines. They are both straight. I like them much better than curved ones for picking up logs. They are equal with big logs but the straight ones are much better for small and medium ones. the curve of the bucket is enough.

Both my thumbs are much narrower than my wide buckets and I have not wanted them wider for demo debris or vines and clearing debris.

 

[littlejoe4]

If you can do all that with the computer and with aluminum mock ups why would you buy any part through the dealer, that is really impressive nice work.

 

[wolf44]

Diet Plan

Some times it is cheaper to buy things than build them. I can always build the trickest parts around I just have trouble finding the time.
Here is a few pictures of machinining the control links and some weight removal. They started a 6.9 lbs and when milled on both side like the pictures show they weigh 3.9 pounds. more to come:usa

 

[mitch504]

Is that your CNC machine?

 

[wolf44]

My shop

Here is a look at the machining bay.

 

[stumpjumper83]

so i think you have the tools part covered... I take it your a machinist by trade.

 

[wolf44]

Engineer,business owner,

 

[tootalltimmy]

I am sure there are lots of people drooling over your shop picture. Thanks for sharing with us!

 

[stumpjumper83]

So are you selling thumbs too?

Working on a tacheuchi tb53fr...

 

[wolf44]

Gee, Let's finish this one first and make sure all is well and then lets talk.

 

[tootalltimmy]

For us guys with standard link thumb, how hard would it be to convert? You can do anything if you throw enough money at it I suppose.

I was also thinking of a way to add to the rotation when you need it and then change it back when you you are mostly digging. Something like the folks with a mechanical thumb do.

I find that the rake is almost horizontal when it grabs small stuff and it brings a lot of dirt to the pile. More travel would keep the brush piles cleaner.

Didn't mean to hijack your thread. This should have gone to the thumb thread above
in full size excavators. Mods could move it?