BL4690 Bent cylinders

[dfkrug]

An even better method is to plumb in flow control needle valves on the barrel end of the dipper boom and bucket cylinders and simply have a slow moving pair of functions to avoid the problem entirely by restricting available flow to the cylinders in question.

This allows full flow upon extension and restricted flow on the retraction of the cylinder (digging portion)

But, Leon, even if you cut down the flow with restrictors, you will still
exert the same hyd pressure, and therefore have the same force at the
business end of the bucket. All you get is slower action on the dipper.

The problem is still the lack of 6 required relief valves in the valve body for the upper and lower booms and the bucket functions.

The work port relief valves on the hoe valve (if the 4690 has them) will be
set higher than the system RV, however. Not lower. So, additional RVs are
not going to help, unless you replace the existing shock valve (if any)
on the dipper extend cyl work port with a RV that is lower than system
pressure.

It would be much easier to restrict the dipper motion, IMO.

 

[wdchyd]

Dfkrug,

You're right about "Restrictors"......No Good!!!!:thumbsup:

I'll back away from Leonz's advice...:thumbdown:

 

[hawkeye08]

I didn't follow the restrictors either. In my simple mind, it just plain looks like too much force being exerted on that link (the bent cylinder). I suspect it could be solved several ways, the quickest is probably a stronger cylinder (larger diameter rod) or changing the force being applied to the cylinder by changing the design (moving the pin location so less force is applied back to the cylinder that bends when used in the manner that causes the problem). Putting extra relief in where appropriate might eliminate the damage, but would most likely reduce the usefulness of the BH.

Good information to know, if I can just remember it if I ever get a BH for my tractor.

 

[leonz]

But, Leon, even if you cut down the flow with restrictors, you will still
exert the same hyd pressure, and therefore have the same force at the
business end of the bucket. All you get is slower action on the dipper.



The work port relief valves on the hoe valve (if the 4690 has them) will be
set higher than the system RV, however. Not lower. So, additional RVs are
not going to help, unless you replace the existing shock valve (if any)
on the dipper extend cyl work port with a RV that is lower than system
pressure.

It would be much easier to restrict the dipper motion, IMO.

Controlling flow +motion =no broken cylinders and only allows movement at one speed=limited force over square area as the system is protected with one relief valve.


FWIW you can physically peel the rod eye like a potato skin or rip the rod eye off a cylinder rod with an unrestricted flow and enough fluid power.

 

[wdchyd]

I didn't follow the restrictors either. In my simple mind, it just plain looks like too much force being exerted on that link (the bent cylinder). I suspect it could be solved several ways, the quickest is probably a stronger cylinder (larger diameter rod) or changing the force being applied to the cylinder by changing the design (moving the pin location so less force is applied back to the cylinder that bends when used in the manner that causes the problem). Putting extra relief in where appropriate might eliminate the damage, but would most likely reduce the usefulness of the BH.

Good information to know, if I can just remember it if I ever get a BH for my tractor.

Have you ever noticed the largest cyl on an Excavator is the dipper/crowd???

It's all force and levers......

 

[hawkeye08]

Have you ever noticed the largest cyl on an Excavator is the dipper/crowd???

It's all force and levers......

agreed:thumbsup:

 

[dfkrug]

Too much force, but only too much when the rod is fully extended. It
is not too much when the rod is not so far out of the cylinder. That is
an extremely long cylinder, and the rod is only maybe 1.125"?

 

[hawkeye08]

Too much force, but only too much when the rod is fully extended. It
is not too much when the rod is not so far out of the cylinder. That is
an extremely long cylinder, and the rod is only maybe 1.125"?

so,

Stronger rod,
Shorter stroke (limit stroke for that cylinder, either with cylinder stop or boom stop),
or less force.

Really seems like a design problem more than an operator problem. The video really showed it was not operator abuse (at least not the normal sense of abuse).

Edit: someone find the right part number of the stronger cylinder with the right fittings and make it a sticky.

Ok, if I bend the cylinder and it is not covered by warranty, why wouldn't just get one that is stronger? It sure seems that if I pay $300 for a new one, but a new stronger one is $400, then I buy the $400 and be done with it.

 

[leonz]

Mag and kubotaboy


If you would be so kind as to provide me with the dimensions of the cylinder
including

1. cylinder barrel diameter
2. rod diameter
3. rod eye inside diameter
4. rod eye weldment width
5. cylinder rod stroke

a. a replacement cylinder with a stop tube will and a 2 way needle valve be less costly than a replacement cylinder with a larger rod diameter.

b. the retraction speed with a larger diameter rod will have a faster retract speed with or with out resistance (please keep this in mind with your decision)

I will forward many names and contacts of reputable hydraulic cylinders for your use and the part numbers for them with and without stop tubes if you would like them.

I would ask that you make a small contribution to your local SPCA animal shelter or adopt a pet if you like in return.

leon:thumbsup:

 

[hawkeye08]

If you would be so kind as to provide me with the dimensions of the cylinder
including

1. cylinder barrel diameter
2. rod diameter
3. rod eye inside diameter
4. rod eye weldment width
5. cylinder rod stroke

a. a replacement cylinder with a stop tube will and a 2 way needle valve be less costly than a replacement cylinder with a larger rod diameter.

b. the retraction speed with a larger diameter will have a faster retract speed with or with out resistance (please keep this in mind with your decision)

I will forward many names and contacts of reputable hydraulic cylinders for your use and the part numbers for them with and without stop tubes if you would like them.

I would ask that you make a small contribution to your local SPCA animal shelter or adopt a pet if you like in return.

leon:thumbsup:

Not sure who are asking for this information, but it is posted right after my post so perhaps me?

I don't have a backhoe and have no information to send you. Please make a donation to the local food bank for my response. thx.:thumbsup: