just another thumb project

[rjmack]

Looks good. How much?

thanks all, i think i'll get some paint on it, use it for a while and work the bugs out... there are always some... and then go from there.
i'm not really set up for mass production, as you can see from the pictures :laughing:

also, the way it is designed opens the opportunity for different... uh, not really sure of the name, but the bottom part with the cleat... there may be some room for other design options that could be easily interchanged... just slide one out and slide another in. i was thinking about one with spread out grapple fingers for picking up brush.

we'll see how bored i get this summer... maybe i'll fab up another one and put it on ebay.

 

[rmully]

Nice job !! Bet it was a fun project ...Now i know i have to learn to weld better

 

[rjmack]

Now i know i have to learn to weld better

me too.

i'm pretty handy with stick and tig, but for some reason i have always had trouble with wire feeders.

i had a diesel portable, but sold it, and now all i have at home is a wire feeder... oh well... if nothing else, i get to practice with it a bit.

 

[MF RED in MT]

Hey rjmack, your thumb looks great, but did you have to add any suitcase weights to your front end, just kidding, . I would assume that you had this exra thick material on hand (looks like 3/4 inch to me) and used it, as I have done the same. I am going to build a thumb for mine, but I am using quarter plate tubing and angle. If I find out that its way to light, then I will add another quarter plate to the existing outside surface of the thumb. I have already built a bolt on to the inside of the front bucket set of brush forks like the Bro-Tek, and also another set that is shorter and acts like a set of teeth on the bucket. When you get it painted, it will look as sharp as any that you could buy, but much stronger :thumbsup:. KC

 

[rjmack]

thanks red

i'm lucky to have a couple piles of sand in the yard, it works as pretty good counterbalance.

the flat bar is 3/8x2".

i have a couple minor changes to make before paint but overall it seems to work reasonably well.

20/20, you were right about thumbs being VERY handy.

i never thought of using a backhoe as an extremely versatile form of grappler skidder but that's exactly what a thumb creates. those logs were finagled out of fairly heavy brush, around trees, and out a narrow trail without causing damage to the surrounding foliage.

luckily i have learned my machine well enough to know when its time to deploy the outriggers

 

[rjmack]

okay, so i gave it a good going over in the field and found a couple of issues. first, i had put the pin boss that connected the cleat positioning arms too tight to the forward arm, such that the two arms bound up earlier than i wanted. this limited the range of movement so i cut the bosses off and remounted them a little further out. this allows for picking objects deep in a hole, or perhaps brush that is almost out of reach.

it also allowed a little more leeway to move the cleat back away from the bucket to allow for picks further out, or picks of larger objects.

as well, i bent a couple pins... i guess the leverage of that curl linkage got the better of them. i can't say the 5/8 pins were too small, because it bent one of the 3/4 pins also. i think i'll try 4140 pins, if that doesn't work then maybe 4340... if that doesn't work then i might have to go with bolts, which i really don't want to. i have the fitting done such that all the pins fit nicely in any hole in the run, that makes adjustments very quick and easy, if i have to go to bolts that will be a real annoyance.

i haven't put it on a scale yet, but am guessing between 25-30 lbs. complete.

 

[J_J]

Nice welds. Did you make it so it would fold back out of the way.

 

[rjmack]

Did you make it so it would fold back out of the way.

i thought about that, and there really isn't any room to do that. also, with hitch pins holding the thumb pins in place it's really quite easy to re/re the various pieces. a person can have the moving parts all on or off in under a minute, and remove the boom saddle as well in under 5 minutes.

i have fit everything such that there is no bashing or banging required to make adjustments, or to remove or replace the pieces, including the boom saddle (although you need wrenchs for that)

the backhoe will fold right tight with the boom saddle on, but i think i would take it off if i didn't plan on using it right away.

btw, lets call the pieces;

boom saddle
fore and aft adjustment arms
fore and aft adjustment inserts
cleat arm

 

[MF RED in MT]

okay, so i gave it a good going over in the field and found a couple of issues. first, i had put the pin boss that connected the cleat positioning arms too tight to the forward arm, such that the two arms bound up earlier than i wanted. this limited the range of movement so i cut the bosses off and remounted them a little further out. this allows for picking objects deep in a hole, or perhaps brush that is almost out of reach.

it also allowed a little more leeway to move the cleat back away from the bucket to allow for picks further out, or picks of larger objects.

as well, i bent a couple pins... i guess the leverage of that curl linkage got the better of them. i can't say the 5/8 pins were too small, because it bent one of the 3/4 pins also. i think i'll try 4140 pins, if that doesn't work then maybe 4340... if that doesn't work then i might have to go with bolts, which i really don't want to. i have the fitting done such that all the pins fit nicely in any hole in the run, that makes adjustments very quick and easy, if i have to go to bolts that will be a real annoyance.

i haven't put it on a scale yet, but am guessing between 25-30 lbs. complete.

Hey rjmack, all you are doing is a little bit of fine tuning to build a better mouse trap, er I mean thumb :thumbsup:. I was thinking that it looked real heavy, but 30 pounds is a real nice weight for a thumb. I was going to use some 1/2 inch trailer hitch receiver pins that I purchaced at HF, but maybe I need to rethink and increase the size if you are bending 3/4 inch pins . KC