Backhoe Slow Dipper Stick Cylinder

john_bud · Nov 3, 2008

Air in the cylinder?

If you don't have a puddle, then maybe the check valve is stuck open. Most hoe's have a check that limits the down travel. A full bucket can over power the hydraulics and force it out super fast.

jb

amitysanimal · Nov 3, 2008

JeffandTamara said:
Looking at this some more, I can say when I raise the dipper stick it goes up smooth and fast, appears to operate properly. When I bring it back down, it seems to go a little too fast, almost like it is freefalling. When it gets to a certain point it comes to a stop and within a second or just a little more, it seems like the Hydraulics catch up and begin to apply pressure to move the dipper stick all the way in ( dipper stick cylinder completely extended).

Can anyone seen this before and help explain this phenomena?

My main boom does that, it will drop like a rock and you have to hold the lever for a few seconds if you want to apply any down pressure. I have been told its common, the boom drops down faster than the pump can push it down. Hope I explained it right to you.

john_bud · Nov 5, 2008

amitysanimal said:
My main boom does that, it will drop like a rock and you have to hold the lever for a few seconds if you want to apply any down pressure. I have been told its common, the boom drops down faster than the pump can push it down. Hope I explained it right to you.

To solve that problem, my early '60's vintage hoe uses a special adaptor fitting on the hose that gets the fluid from the cylinder when it drops. It has 6 holes in the fitting and a sliding sleeve. It's hard to visualize, but...

Picture the normal hose end fitting. It's just a hole, right? Imagine that you block the hole with a cone (pointy end out). Drill a small hole in the pointy end and then drill 5 holes equally spaced around the edges of the cone. Inside the fitting put a thin sleeve that is able to easily move up and down so it can cover and uncover the 5 holes around the edge. You still with me on this? Now, imagine the fluid going to the fitting from the outside direction. The fluid goes thru the 1 inner hole and 5 outer holes. The fluid pushes the sleeve up and away so fluid flow is relatively easy in that direction. Picture the fluid flow reversing. The flow pushes the sleeve down where it covers the 5 perimeter holes, limiting flow to the center hole and some from the other 5. That's what Ford put on the hydraulic line so that when the boom is going down the weight of the boom + dipper stick + bucket + spoils in the bucket can't overpower the flow and cause cavitation.

jb

amitysanimal · Nov 5, 2008

I understand what your saying. I'll check around locally and see if I can find something like it.

Thank You,

amitysanimal

JeffandTamara · May 3, 2009

Started using the backhoe a little more, and now I get these pops on just about every stroke of the dipper cylinder. I have looked for any binding on the frame and can't see a thing. I am guessing it is a bent cylinder as has been suggested earlier in this thread.

(1) Is there any procedure for making sure this is in fact a bent cylinder?
(2) If it is, can anyone walk me through how to pull the cylinder off the hoe. I have taken it off the tractor. Great Bend 851

(3) Also,, Any ideas on how the cylinder could have been bent...I typically just idle the tractor when using the hoe,,,and I really can't remember of putting the hoe in a hard bind of any kind. Probably have used it less than 8hrs in two years...

Thanks...

J_J · May 4, 2009

I think you are sucking air past the seals when you raise the dipper, and when you bring it down, it comes down fast until the air is compressed. I also think you may have a bent rod. Check the rod by putting a straight edge on it at different places. It should be obvious.

JeffandTamara · May 26, 2009

Talked to a tractor mechanic today...Described the Popping noise to him. He thinks the nut that holds the cylinder rod at the base is loose. Sounds plausible..since I can't see anything bent or scored or other wise binding up.\

The pictures atttached are of the dipper cylinder. If it is the rod bolt on the end of the cylinder, how do I get to it? I assume the first step is to remove the cylinder off the hoe. I have the backhoe off the tractor in the barn, so I can crib it up or chain it up as needed. I think I can get it off. Is there anything special I should do about keeping fluid in the system? Should the rod be extended full out or does it matter?

ANY AND ALL IDEAS / SUGGESTIONS ARE APPRECIATED....THANKS!!!

Great Bend 851 backhoe

JeffandTamara · May 26, 2009

Attachments failed to come along with the reply...Hopefully here they are...

Brad_Blazer · May 27, 2009

amitysanimal said:
My main boom does that, it will drop like a rock and you have to hold the lever for a few seconds if you want to apply any down pressure. I have been told its common, the boom drops down faster than the pump can push it down. Hope I explained it right to you.

That's correct. The weight forces fluid out of the top of the cylinder faster than the pump fills the base. It only takes 15psi to pull a full vacuum (air doesn't have to suck past the seals) so at the bottom of the swing the pump has to fill the resulting void before the dipper (for example) continues to move. I don't think such large scale, slow moving cavitation causes any problem other than an annoying delay.