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kthompson
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2007-11-06          147825

Has anyone had experience with a bolt on or pin on THUMB for a backhoe or excavator? Thanks kt

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earthwrks
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2007-11-06          147827

What are you looking for Kenneth?

There are different types. Some of the newer ones use the bucket pivot and have to have a hydraulic cylinder that holds it out to meet the bucket. Both can be controlled for better accuracy in picking up stuff.

If you go with a manually set thumb you're limited to the range of motion when picking stuff up---you'll find you have be a certain amount of feet away to get a good grab.

You'll still have to do some considerable welding on the mounting bracket to the boom. I saw some crappy installations down south that fell off or got twisted during use.

Be sure the boom is strong enough to hold the bracket AND withstand the power exerted by the bucket as it can crush the boom like I found out on my backhoe DOH!

Case has or had booms that you could not weld to. These thumb brackets have to be bolted to the booms which are prone to sliding back and forth.

Price goes hand-in-hand with strength and quality, so keep that in mind if you're offered one that is several hundreds cheaper. ....

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Murf
Join Date: Dec 1999
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2007-11-06          147832

We got them on all the excavators and even some of the small machines.

I think I might have some pictures of one I did for a buddy from plasma cut steel parts from a local company here, I sent them an AutoCad drawing and they delivered all the bits. It was to go on a 3,000 pound mini-ex he has for doing stone work.

What exactly would you like to know?

Best of luck. ....

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kthompson
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2007-11-06          147842

It will be used for limbs and stumps. Not many stones here.
Would want hyd cyl set up. Machine has the circuit already plumbed. Seems hyd thumb would be easier to work with than fixed ones.
The excavator it will go on weighs 10,000 lbs.
Have concerns about welding on the boom. The boom has two pin holes that I should be able to use near the rear end of the mount to hold that end and prevent the mount from sliding frontward or backwards.
EW, I have seen some designs that would seem had to twist with anything that was not a straight load. There is one on ebay off and on that just looks like you and I could twist it.
Murf, need idea on steel for the jaws and cylinder needed. What size pins and are normal strenght tractor pins ok?
I have seen two legs and single leg design. It would seem the single leg would be easier to twist or bend. All thoughts are appreciated. kt

....

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Murf
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2007-11-06          147847

Kenneth, in no particular order, yes, regular hitch pins will work just fine. Usually they are 1" in size.

As for steel, if you mean dimensions, that will vary depending on the power you want / need.

The big problem will be the plumbing, without the proper setup, including a low pressure by-pass valve to prevent damage should you try to clamp too tight you are just wasting your time.

If all you want it for is limbs, brush and stumps you will be happier with a proper grapple setup on a tractor. Ours are really only used for feeding the grinders, they are too slow for anything like clearing.

Are you sure your machine is already plumbed for a thumb and not a hydraulic breaker or packer? Those types of remotes are very common on mid-sized machines and are not the same as what you want for a thumb at all.

Best of luck. ....

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earthwrks
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2007-11-06          147848

Kenny it's more than leg type, number etc.--there's the height, width, steel type and thickness, pin diameter, etc.

As far as pins go, we use the same chromed rod stock used in hydraulic cylinders. It's about $5 an inch for 1.5" dia. but a fraction of what you pay at the dealer. ....

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kthompson
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2007-11-06          147852

Murf, on the hyd set up...not sure...I know it will run auger. Still waiting on the machine the manual is running behind it.

"Additional double-acting hydraulic control
valve for an attachment circuit with folding
control pedal and circuit for direct return
of oil to the hydraulic tank.
Attachment circuit piping (double-acting +
return) as far as the bottom of the boom."

is the wording I find in brochure as standard equipement.

Following is for optional set up which I do not believe it has.

"Circuit for hydraulic breaker with direct
return to the tank.
Hydraulic circuit for double-acting
attachments.
Hydraulic circuit for operating a clam-shell
bucket (opening/closing and rotation of
the bucket)."

I understand what you said about low pressure so not to put too much pressure against it but what is the difference between a fix thumb on this and one with a hyd cyl? kt ....

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earthwrks
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2007-11-06          147854

Murf this low pressure valve you speak of--I haven't seen that. Are you sure a regular hydraulic thumb on a smallish machine can't use the accessory plumbing as is? It has relief protection doesn't it? ....

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Murf
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2007-11-06          147860

Kenneth, it 'sounds' like the machine is equipped with the right kind of circuit, but I can't be sure from that description, "Attachment circuit piping (double-acting +
return) as far as the bottom of the boom." does sound like the one, but likely you will have to run the piping, etc., since the decription says it stops at the bottom of the boom. Probably terminated into a loop or capped off next to the boom.

But then in the 'options' category (which you say it does NOT have) "Hydraulic circuit for double-acting
attachments." is precisely what you need to have, so who knows?

The difference between a fixed thumb and a properly setup mechanical one is simple, one is real easy to use, the other is real easy to break. ;)

Seriously you just need to be very cautious when using it so you don't over crush the setup and bust something.

Jeff, yes you 'could' use any circuit and depend on the system relief valve, but I've never seen a thumb yet that was strong enough to not get mangled long before the relief valve said 'uncle' and stopped it.

What I was talking about is a 'standard' valve but with the difference of having a built-in relief valve which is different in two ways, first, the valve can be set down to a VERY low pressure point, and secondly and most importantly, the pressure relief valve dumps the excess pressure right back into the return line, and will do so whether the circuit is in use or not. If the thumb is just sitting there and the bucket crushes back into it with enough force to create a pressure above the set-point, the valve will open, allow the fluid to escape and the thumb to move back out of the way rather than overload it.

Best of luck. ....

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earthwrks
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2007-11-06          147864

(Sound of shaking my head with mouth open and cheeks flapping) uhhhh?

Whatchootalkin' 'bout Willis?

IMHO---NO!, IMEO ("E" stands for Emperical---hahahaha) having a low pressure relief especially on a thumb could spell disaster if something like a slab of concrete were picked up on its end and then changed position and increased leverage on the thumb---it would fall out without warning.

I see no difference in operation if the boom had a manual or hydraulic thumb--a manual stiff thumb has to have the same resistance as a hydraulic in order to work right. And it would be the bucket curl circuit that would do the relieving especially when using a manual thumb--there is no choice. ....

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earthwrks
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2007-11-06          147865

Murf I referred to my Caterpillar Performance Handbook and there is nothing I could find about relif valkves for a thumb. There is a rating of about 4350 PSI for a typical machine Kenny is looking at (I picked a 312). The only category they have a rating for is "Implement" which to me is inclusive of a thumb, no? Even the much bigger units have only the same category.

Can you learn me somethin' Canucker! ....

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kthompson
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2007-11-07          147893

It would seem if any lifting device were built so it would turn loose a load use the concrete in EW example without warning that could be dangerous. Sure would make it important to let nothing of value ever be under the load.

I do not understand how, if you are using the bucket curl pushing against a hyd or fixed linkage thumb would be any different as to possible damage. If the hyd setup had the ability to have more force than the bucket curl and that was used, that I can understand the difference.

Well three questions..
1) any brand(s) or companies anyone suggest:
2) saw a site that offered a thumb to meet the edge of the bucket and one to slip inside the bucket: thoughts
3) still wondering about a bolt on set up. Have seen one or two that bolt around the boom sort of like leaf springs and saw one that must have bolted into the bottom of the boom. Could not understan that last one unless you drill and thread the boom which I don't think would be good.

Again, thank you, kt ....

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earthwrks
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2007-11-07          147908

Kenny I should have said some of the newer machines come equipped with mounting "tabs" to quickly install the thumb---some don't. If by bolts you mean like U-bolts like I mentioned earlier, those will stretch the bolts then slide up the boom once they have pressure against them. The best way is to weld the mount to the boom. And be sure the guy knows how to weld. As far as mfg's. I would stay around town and check out their quality. Things to look for ar overall quality--how does it look? Does it look it was a 10th grade welding project or did someone take the time to engineer and build it? Paint work says a lot. Even though these will be toast in a matter of minutes, mfg's. who care do decent paint jobs. Ones that don't, send it out without paint, or if it is it's a cheap spray paint. Pin diameter and how the pins are secured says a lot. I saw some down south that were held on with TSC hitch pins that fell off and twisted as a result when it picked up a stump. Are the components loose---do they slide around against each other? If yes it will only get worse with each use. More slop means easier to break the next time. ....

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