KX057-5 front blade hyd. not strong enough

[TheOldHokie]

I have the same issue with my old excavator. I understand what Dan is saying. Think about it.

If you have a hydraulic cylinder and fully extend it by pushing oil in the cylinder, and then cap the two ports on the cylinder, and if the seal at the cylinder rod functions normally, so no oil leaks out, then if the cylinder rod went into the cylinder, the volume inside the cylinder would decrease.

So where would that oil go? Nowhere, since it cannot leak out of the cylinder. So the cylinder rod will never enter the cylinder unless there is someplace for the oil inside the cylinder to go.

So unless there is a leakage path outside the cylinder when the cylinder for the blade is fully extended, the blade will not move.

With my high hour little mini ex I am going to install a pilot operated check valve on the cylinder. I do not want to spend the time or money to make things factory original. Just want my blade to stay down while using the excavator, without having to keep manually pushing it down every few minutes.

Henro I know when we talked about this I suggested the lock valve but I had not considered the possibility there was a port relief on that circuit. After this discussion I now realize that the digging operation really poses a risk of exceeding the working pressure on that blade cylinder. You want to be careful you do not defeat any port relief that might be on your machine by putting the check valve between the relief and the cylinder. That would not be good. My apologies for the have azzed advice - I am not accustomed to these types of applications and I really need to be more cautious with my advice.

Dan

 

[Henro]

Henro I know when we talked about this I suggested the lock valve but I had not considered the possibility there was a port relief on that circuit. After this discussion I now realize that the digging operation really poses a risk of exceeding the working pressure on that blade cylinder. You want to be careful you do not defeat any port relief that might be on your machine by putting the check valve between the relief and the cylinder. That would not be good. My apologies for the have azzed advice - I am not accustomed to these types of applications and I really need to be more cautious with my advice.

Dan

Thanks Dan. I will look further but do not remember any PRV being in the circuit.

Actually I am not sure how much force the blade cylinder feels when digging. BUT mine leaks down with out any digging at all.

So I GUESS that if there was some kind of PRV device in the circuit, and IF I installed a pilot operated check valve at the cylinder, all that I could damage was the cylinder itself, and nothing external to it.

So I think that is what I will do...

Edit: I love the ability forums like this let us share knowledge and experience with others!

 

[TheOldHokie]

Thanks Dan. I will look further but do not remember any PRV being in the circuit.

Actually I am not sure how much force the blade cylinder feels when digging. BUT mine leaks down with out any digging at all.

So I GUESS that if there was some kind of PRV device in the circuit, and IF I installed a pilot operated check valve at the cylinder, all that I could damage was the cylinder itself, and nothing external to it.

So I think that is what I will do...

Edit: I love the ability forums like this let us share knowledge and experience with others!

A port relief is also protecting the structure on which the cylinder is mounted. You want the cylinder to retract before you break an expensive or NLA casting with too much leverage. Just saying.....

Dan

 

[Henro]

A port relief is also protecting the structure on which the cylinder is mounted. You want the cylinder to retract before you break an expensive or NLA casting with too much leverage. Just saying.....

Dan

Understand what you are saying, Dan.

I think, but will have to look, that the blade arms attach to the frame of the excavator, which is not a casting but rather welded steel. My gut is telling me the cylinder itself would be the weak point, as it is normally fully extended when the blade is down for stability.

Of course, I have learned to trust my gut most when dinner time is approaching! I always keep this in mind too when evaluating things...