Thumb Mini Excavator thumb

[BertZegers]

The valve I used to make my hyd thumb has reliefs on both work ports. Need both for when the thumb is pushing or being pushed.

I think you need only one. Click on the picture to enlarge.


The parts added for the thumb are shown in the red circle. In the third circuit are the Quick Connects for the log splitter.

If the pressure comes from the pump (pushing), then there is the main and/or bucket relief valve plus the thumb relief valve. If the pressure comes from the bucket pushing the thumb ( being pushed), the thumb relief valve will act. The thumb relief valve is adjusted to a lower pressure than the main relief valve, but high enough to hold the load.

Without the added relief valve you rely on the main and/or bucket relief valve only.

Here is how I have the relief valve plumbed in.

 

[ptsg]

I think you need only one. Click on the picture to enlarge.

View attachment 637949
The parts added for the thumb are shown in the red circle. In the third circuit are the Quick Connects for the log splitter.

If the pressure comes from the pump (pushing), then there is the main relief valve plus the thumb relief valve. If the pressure comes from the bucket pushing the thumb ( being pushed), the thumb relief valve will act. The thumb relief valve is adjusted to a lower pressure than the main relief valve, but high enough to hold the load.

Here is how I have the relief valve plumbed in.
View attachment 637950

Doesn't your KX41 have Work port relief valves on the thumb circuit already?

 

[BertZegers]

Doesn't your KX41 have Work port relief valves on the thumb circuit already?

Good question! I have never checked. The other reason for me to put this adjustable relief valve in is that I want the pressure on the bushings to be as low as possible. Bushings are very expensive!

I have used the "hammer port" for the thumb. The "hammer port" is also usable for a thumb by taking out the return hose and put a plug in. I basically put the thumb relief valve in the plug hole and used the return hose on the pressure relief valve. ( As the picture in my previous reply shows )

 

[tractorcrazy]

Yes it is already plumbed I just have to connect cylinder hose up to the existing quick coupler on the boom

 

[mike48130]

What model mini do you have? I just looked at my Bobcat 322 service manual and they have the port relief valves listed for the boom, bucket and arm cylinders, but not for the aux ports.

I've been looking at the weld on ones out there, and not sure if I want to build or make. But I think you need something on the cylinder to protect it.

 

[BertZegers]

Doesn't your KX41 have Work port relief valves on the thumb circuit already?

I looked, and all circuits have dedicated relief valves, except the "hammer/auxiliary" port, that is now used for the thumb.

 

[ptsg]

I looked, and all circuits have dedicated relief valves, except the "hammer/auxiliary" port, that is now used for the thumb.

Interesting. Thanks for check that and posting here.

Good thing you installed one anyway. :thumbsup:

 

[nyone]

I built my own thumb for my mini. I used the same rod diameter for my thumb as the rest of the machine. My thumb will uncurl my bucket. I haven't bent or broke anything yet. I think I habe 300hrs on this setup and cleared a lot of brush and stumps with it.