hyd thumb cylinder

[eianewb]

does anyone know where to find a good used cylinder for a hyd thumb, my excavator is already plumbed, but i only have a mechanical link. i am looking to turn it into a hyd thumb.

i am located in eastern iowa.

thanks.

 

[fred@pemberton]

Just putting a Cylinder on a Manual thumb usually doesn't work very well, unless the thumb was designed from the start to accept both a stiff leg and a cylinder.

You'll never get it to retract the right way.

And the geometry on the extended side of the cylinder might put the cylinder rod in suck a weak position that it will just bend the rod and destoy your cylinder.

The best way would be to contact the company who made it and see what they say.

 

[eianewb]

i have a welder and a torch sure wouldn't be the biggest modification we ever done. the stick also already has the tabs there for the cylinder, just gatta add some to the thumb.

 

[excavator]

First off all, what size excavator? Pretty much every different size machine takes a different size cylinder. Thumb circuits shouldn't run more than 1800 psi so you don't need a high pressure cylinder. And what Fred says is true. Most mechanical thumbs are not made for a hydraulic cylinder. I'm not saying it can't be done but I have seen guys try it and it didn't work well. Does your thumb pivot on the bucket pin or does it pivot on it's own bracket welded to the stick?

 

[eianewb]

kobelco 130. the thumb pivots on a welded on bracket. i have not measured the size of cylinder i need yet, but i have pivoted the thumb all around with the link unhooked with the bucket. it has the full range of motion i need, all i have to do is fund a cylinder that has the right (approx) collapsed length and stroke. i say approx because i am sure that nothing will be perfect, just pretty darn close.

is there a spacific bore i should be looking for for this size machine? i dont want it too big in diameter and break the end of the stick off.

 

[mowzall]

https://www.surpluscenter.com

build it with a pencil & paper first though.

 

[Hendrik]

From looking into thumbs I have learned that the thumb cylinder needs to be weaker (perhaps have a relief valve) than the bucket cylinder because something has to give or there will be problems. Although this has more to do with warranties than actual working of the mechanism because a mechanical thumb does not have any relief function.

 

[eianewb]

i was out running my ex today for a while and saw that there was another set of holes on the thumb itself, looks like for a cylinder to hook up. i guess maybe it was designed for one afterall? i guess i did forget to measure the length of cylinder i need tho. ointhead

a hyd thumb would sure be nice taking out trees and roots and such. i would sure think that it would be better on the machine to move the thumb by itself, rather than move the stick and boom to readjust all the time.