Mechanical Thumb Question

[06B3030]

I have a B3030 and I picked up a Kubota BH1976 mechanical thumb today. I'm planning on mounting it on my BH75, where I'll be fabricating/copying the upper thumb mount on the BH77.

Question...Is there a pressure relief valve for the bucket when it curls up against the thumb?

 

[bbxlr8]

I will let more knowledgeable people chime in to double check but I have a factory BH77 and Kubota mechanical thumb and understand that it is just that = mechanical and no changes to the hydraulics with the install.

 

[06B3030]

I will let more knowledgeable people chime in to double check but I have a factory BH77 and Kubota mechanical thumb and understand that it is just that = mechanical and no changes to the hydraulics with the install.

If the thumb is down in a forward position, do you have to manually "stop curling" once the bucket hits the thumb, or does the curl pressure stop once it maxes out without anything being damaged?

Just wondering if you can "overdrive" the bucket against the thumb, or a "relief" kicks in.

 

[NorthwoodsLife]

If the thumb is down in a forward position, do you have to manually "stop curling" once the bucket hits the thumb, or does the curl pressure stop once it maxes out without anything being damaged?

Just wondering if you can "overdrive" the bucket against the thumb, or a "relief" kicks in.

You'll mash it to max rated curl pressure unless you release the lever. It will damage, crush, or destroy whatever you want or don't want. You are the relief valve.

 

[nbryan]

No worries the thumb withstanding curl pressure. The factory installed thumb on my BH77, when engaged and in use somewhere in its adjustment travel, holds whatever I grab at full curl pressure, and the hydraulic bypass cuts in.
Rocks, logs, stumps, or whatever is being curl-crushed against the thumb has no effect on it.
It's solid.

 

[Tarmy]

This is what you want. It gets very tiresome hopping on and off the BH.

And as mentioned, you are the brains of the rig…and will feel/hear the stopping point.

 

[06B3030]

No worries the thumb withstanding curl pressure. The factory installed thumb on my BH77, when engaged and in use somewhere in its adjustment travel, holds whatever I grab at full curl pressure, and the hydraulic bypass cuts in.
Rocks, logs, stumps, or whatever is being curl-crushed against the thumb has no effect on it.
It's solid.

THANKS!

I figured that the hydraulic system relief valve would kick in at some point. I know the curl function exhibits the strongest force in the backhoe functions, just wanted to make sure it would kick in before any damage occurred.

I looked at the BXpanded thumb, but it looked pretty flimsy compared to the Kubota thumb. i could see that one getting worn/damaged.

 

[06B3030]

This is what you want. It gets very tiresome hopping on and off the BH.

And as mentioned, you are the brains of the rig…and will feel/hear the stopping point. View attachment 112731

I figured I'd "walk" before I "run"! LOL

 

[Jchonline]

I figured I'd "walk" before I "run"! LOL

Yes you will be walking alot...getting off the machine to adjust the thumb in and out!

 

[fried1765]

Yes you will be walking alot...getting off the machine to adjust the thumb in and out!

A hydraulic thumb is a wonderful thing,....... but it also lightens the wallet.

 

[bbxlr8]

I

A hydraulic thumb is a wonderful thing,....... but it also lightens the wallet.

I would love one and see where they would be GREAT but "do the dance" due to budget.
BTW - I've gotten pretty efficient at it

edit - not that I'm not getting other "stuff" ex. the WM stump grinder this year!

 

[NorthwoodsLife]

THANKS!

I figured that the hydraulic system relief valve would kick in at some point. I know the curl function exhibits the strongest force in the backhoe functions, just wanted to make sure it would kick in before...

Respectfully, you, the OP, keep saying "relief valve".

Just to clarify, there is NO relief valve, other than maximum force designed into the curl function. That goes for all functions in hydraulics on your BH, FEL, etc. It only stops pushing pressure when it hits max capacity, and then, it kind of groans and doesn't move anymore. OR, you release the lever.

What others stated is that the thumb can handle the max capacity if you're not paying attention and stay on the lever. Is it abuse? Maybe, if done a lot. But the thumb is designed to handle the force.

You are the relief valve.

 

[NorthwoodsLife]

I once knew a guy who operated a backhoe daily. Passed away by now. Rumor was, with a commercial BH, he could tap someone softly on the shoulder, or pick up an egg with it.
I never saw him do that, but time in the saddle makes perfection.

 

[06B3030]

Thanks everyone!

 

[06B3030]

Respectfully, you, the OP, keep saying "relief valve".

Just to clarify, there is NO relief valve, other than maximum force designed into the curl function. That goes for all functions in hydraulics on your BH, FEL, etc. It only stops pushing pressure when it hits max capacity, and then, it kind of groans and doesn't move anymore. OR, you release the lever.

What others stated is that the thumb can handle the max capacity if you're not paying attention and stay on the lever. Is it abuse? Maybe, if done a lot. But the thumb is designed to handle the force.

You are the relief valve.

I guess I should have been more clear and asked if the max curl pressure, once the system relief valve kicks in, would cause any damage to the thumb, or dipperstick/cylinder. Sounds like the thumb assembly was designed to stop the bucket without any damage occurring.

I've reached max system pressure working with the tractor, and know what that sounds like. It's all about feel, and I'm sure once the thumb is working, it'll just take a little practice.

Thanks!

 

[SRRGC1]

I have a B3030 and I picked up a Kubota BH1976 mechanical thumb today. I'm planning on mounting it on my BH75, where I'll be fabricating/copying the upper thumb mount on the BH77.

Question...Is there a pressure relief valve for the bucket when it curls up against the thumb?

Short answer is "YES". Relief valve will open, and you may hear a squealing type of noise presuming hydraulic system is working correctly.

 

[Soopitup]

I wasn't very impressed with my BX mechanical thumb the one time I've tried it so far.
Trying to pick up a section of foundation wall out of the hole, thumb/bucket kept slipping off.
I ended up having to turn around and fight it into the loader and move it that way.

A hydraulic thumb is a wonderful thing,....... but it also lightens the wallet.

What doesn't on these things?