Backhoe Mechanical or Hydraulic thumb?

[jchealey]

I have been thinking about getting a thumb for my backhoe. I used one on a large excavator to tear down a house and rip a tree out of the ground and it would be a useful addition to my lazy man tools. Do you have any recomendations as to how to size, or mechanical vs Hydraulic? I have plenty of pressure for the Hydraulic.
From the pin to the end of the teeth is 22 inches. Backhoe is a Woods 1050.

Jerry
L48

 

[rScotty]

I have been thinking about getting a thumb for my backhoe. Jerry
L48

I have had hoes with and without a hydraulic thumb. Before I had a hydraulic thumb I just had a piece of metal that I would pin onto the dipper arm. I guess you could call it a mechanical thumb, but it didn't move.

The hydraulic thumb makes the hoe into a whole new implement. I can pick up and place heavy things with it now. Not just rocks, but even fairly fragile things. No more dragging things to the side to get them to slide into the bucket, it's just lower the bucket and grasp them.

There's a bit of a tricky relationship between the thumb and its geometry. You want the bucket to always be able to overpower the thumb and also design it so that the thumb can never get into an "over-center" position. There also needs to be a pressure relief valve or circuit so that the lines to the thumb don't burst when the bucket forces it backwards.

All in all, I think that using it has given me the understanding to design one myself now if i had too....but it was worth while to go ahead and buy the proper factory one for my hoe. Costly, but worth it.
Good Luck, rScotty

 

[hr3]

Hydraulic for sure,, I have a mech. one now and wish I had spent the money when I bought the hoe.. Now I have to convert it..

 

[Kyle241]

Hydraulic if you can afford it.

 

[20 20]

The obvious answer on which one is better hyd-vs-mech would be hyd. With that written I have had both and no matter what both have been VERY usefull. I built my own{3or4} mechanical and hydraulic, I bleieve one of the most important things is to make the thumb weaker then the bucket. Much cheaper to fix a thumb JMO.

 

[cal1]

How do you do that?

 

[20 20]

How do you do that?

If you're asking me then I'll try to give a quick explanation. I use material {if mechanical } that will bend/break instead of causing damage to the arm/bucket/cylinders/etc. On hydraulic units there are different ways of making the thumb cylinder weaker then original equipment. Hope this helps what I wrote.

 

[hayden]

I'd get a hydraulic thumb if at all possible.

 

[cal1]

Thanks 20 20, I was wondering how to make a hydraulic unit that would be weaker than the arm. Guess you'd need to be pretty familar with both the existing system and the thumb. I don't know if there are any adjustments to reduce power on a piston. I've done a lot of electronics (mostly digital) but wish I had more usable knowledge.

 

[rScotty]

Thanks 20 20, I was wondering how to make a hydraulic unit that would be weaker than the arm. Guess you'd need to be pretty familar with both the existing system and the thumb. I don't know if there are any adjustments to reduce power on a piston. I've done a lot of electronics (mostly digital) but wish I had more usable knowledge.

Nothing wrong with being familiar with the existing system, but it's not really necessary. That's because it's normal practice is to plumb the thumb system with relief valves anyway. The reason being that either the bucket forces the thumb or the other way round....and in either case both systems have to have relief valves and bypass lines to avoid breaking something expensive. So just build it that way and as a bonus you can simply do some cautious experimenting and set the relief pressure appropriately.

That's how most backhoes work and it's also how Kubota solves the problem of relative hydraulic strength with the hydraulics in their stock backhoes. Our M59 came with either 8 or 10 adjustable relief valves mounted in a double row right onto the backhoe lever manifold. The bypass lines are internal to the valve block. Kubota set the pressures at the factory, but there's been some adjustment required since. That's pretty much typical.
rScotty