WEAK Dipper or jib

[MRCONCDID]

HI guys,
I have a L48 TLB. Here's the problem
The outward push of the dipper/jib is weak (the contraction of the ram), a lot weaker than the pull direction (the extension of the ram)
I know this is the weaker direction for this ram, but it is ridiculous weak.
I can't push 3 inches of top soil at 1800 rpms. All other functions are smooth and strong, very strong at this RPM.
I do not hear a bypass opening, just the wine of the pump maxing out when I try this ram in the push direction.

I have placed a pressure gauge at each end of the ram both push and pull both tested the exact same, 2800psi
I also placed a plug in the push hose bib, then tired the pull motion. the ram started to move about a half inch then stopped.
I then switched the plug to the pull bid and repeated the test, again the ram moved about a half inch and stopped.
By my understanding, this field test is a pass in both directions, and the pressure test is also a pass having the same pressure
on both push and pull.

Is this normal? 3 inches of top soil is barely the height of the teeth on the bucket.. I would think is would do a lot more.
The same pump runs the entire hoe minus the swing. and all other functions on this circuit are very powerful.
I do not know what else to check.

Thanks for your help
MrC.

 

[CincyFlyer]

Given that you have must less surface area on the cylinder due to the rod, you will have generally have about 25% less force (depending on rod/piston size ratio). But you cannot judge that force simply by how much dirt it moves, as that's not repeatable. Perhaps use a crane scale on the bucket, or something that will give you numbers. Measure any forces with the dipper at the same angle. The angle of the cylinder versus the dipper is important, as well; we all find out that sometimes you gotta move the tractor to get the most out of the BH—IOW, sometimes it's working as designed—and it is designed to pull—but it may not work the way that you want it!

 

[LD1]

Sounds normal.

The geometry and cylinder orientation isn't made to generate alot of push force.

The only "pushing" I do with a how is either pushing back loose piles of dirt, or pushing the machine forward. Never trying to push virgin sod. Be especially since the bucket isn't even in a position to allow the teeth and cutting edge to cut properly.

The plug test tells me the cylinder seals are fine, and pressure test confirms you have an adequate hydraulic system. It is what it is, you are generating the max force possible and are limited only by the design of the how itself.

Why are you wanting to push back virgin sod anyway?

 

[MRCONCDID]

I didn't said "Virgin soil", i said top soil it was just a term or example i used for dirt.
I, just like you, need to push the loose soil that has collected at the closest end of my hole or trench, Yesterday I was helping a neighbor by digging a grave for his dog,
I dug about 30 inches deep and about 3.5 feet in length by my bucket width , I wanted to push the accumulated dirt on the closest edge back into the hole. the small pile of loose dirt was about 1 foot tall,
I placed the teeth of the bucket just off of grade (not touching the ground) and attempted to push/rake the pile back into the hole. It would not push 12 inches high x bucket width x 2 feet deep pile of loose dirt, I raised the bucket half the height of this pile and was able to push/rake the top of the pile off into the hole, then the remainder into the hole. I then leveled the bottom of the grave and picked up the dirt I had just pushed in .

I know that the pull is weaker than push, I have read up to 50% as much. That said, this does seem very weak considering how strong all other functions are, I was hoping there was another test I could do to narrow down the problem. May be, because it is so close to the tractor, and at this position it does not have the leverage to do the task, May be I should dig farther out from the machine, and see if it can push more, say at 6 feet out vs 3 feet out. that could make a big difference I am sure. I will try that ASAP.

Thanks guys,
I will report my findings
MrC.

 

[LD1]

Yes, yes.

Too close to the machine.

Your force will be greatest about mid stroke.

Just look at the geometry of the pivots. In close, or full reach, draw a line through both cylinder pins. Base end through rod end pin. The look at that line in relation to the pin the Dipper pivots around. Not far....means not much leverage.

 

[MRCONCDID]

Here's what I found out,
I tested the pressure at the backhoe, found it to be 500psi below spec. spec is 2800psi, it was at 2300psi. I adjusted the pressure relief valve to max spec of 2800psi. then went for a dig, there was a noticeable improvement across the board. I did as you suggested and dug further out from the machine, that did the trick.

Only issue after making these two adjustment is now I have 3 cylinders leaking, one on the hoe and two on the loader curl. none of these leaked before the pressure boost (same pump). I plan to have those 3 cylinders rebuilt, either by me or someone else.. I like the pressure increase. it is stronger for sure.


Thanks for your help,
MrC.