bucket drops

[SPYDERLK]

That is the most it will resist. Once it moves (if at all), unless it sucks more air in from somewhere, the resistance increases as vacuum increases on the cap end of the cylinder.

What is your position on retracting

Same as yours. Pressure has no limit. ... Vacuum does.

 

[J_J]

Mayee this article can shed some light on the subject.

How to troubleshoot hydraulic cylinder drift

It does seem odd though that when changing out the piston seals on a loader,, the lift arms and bucket stays up.

 

[LD1]

Mayee this article can shed some light on the subject.

How to troubleshoot hydraulic cylinder drift

Good article. So why did you say this earlier:

There is an exception to your theory, and that is, if there is a pulling load on the cyl it will extend the rod if the seals are leaking. .

Same thing if there is a load pushing on the rod, it will leak down if the seals are leaking.

 

[J_J]

If there is a seal leak,with a pulling load, the fluid will transfer until the pressure equalizes.

As you stated, the load could pull a vacuum.

 

[LD1]

If there is a seal leak,with a pulling load, the fluid will transfer until the pressure equalizes.

As you stated, the load could pull a vacuum.

Yes it can, but would reach equilibrium, and not continue to drift at the same rate.

But you are avoiding my questioning of the loader itself drifting down. Compressing a cylinder??

 

[J_J]

Well, answer this, do you think all loader arms descending over night is caused by valves?

Are you saying that it could not be caused by the cyl seals?

 

[LD1]

I am saying yes, it ain't the loader seals.

It can be the valve, gland seal leak, hose leak, but not the piston seals.

 

[SPYDERLK]

If there is a seal leak,with a pulling load, the fluid will transfer until the pressure equalizes.

As you stated, the load could pull a vacuum.

As soon as the port blocked cyl extends its volume increases. Since it is full a hard vacuum immediately develops on both sides of the leaky piston. Neglecting seal friction, the force then remains constant at 14.7psi X rod area as the cyl continues to its stop. This leaves an empty void in the cyl. The oil and any included water -- EVERYTHING VOLATILE -- boils into the void at ambient temperature raising the pressure slightly above 0 Absolute.
larry

 

[arlen4720]

As soon as the port blocked cyl extends its volume increases. Since it is full a hard vacuum immediately develops on both sides of the leaky piston. Neglecting seal friction, the force then remains constant at 14.7psi X rod area as the cyl continues to its stop. This leaves an empty void in the cyl. The oil and any included water -- EVERYTHING VOLATILE -- boils into the void at ambient temperature raising the pressure slightly above 0 Absolute.
larry

Sometimes the glands aren't very good at holding a vacuum though, and air is sucked in around the rod, and the whole process repeats. A situation that I've observed countless times on industrial press brakes.

 

[SPYDERLK]

Yeah, but then it just extends easier since the cyl holds a less complete vacuum.

 

[arlen4720]

Yeah, but then it just extends easier since the cyl holds a less complete vacuum.

Yes, I'm in agreement.

 

[J_J]

Does your theory suggest no one has to replace the piston seals anymore.

So why are people replacing seals, just for the he** of it.

I'm just saying.

 

[LD1]

Does your theory suggest no one has to replace the piston seals anymore.

So why are people replacing seals, just for the he** of it.

I'm just saying.

Someone replacing piston seals for a loader drifting down overnight....yea, must just be for the he** of it, or someone gave them bad advise.

When piston seals are shot, the loader still holds, but you would notice a lack of power. Cause when trying to lift, Pressure is applied to the base end of the cylinder, and the rod end is opened back to tank. So the pressure bypasses the seals, out the rod port, and back to tank. Thus it is hard to develop full pressure, and the loader lacks power.

But when the valve is in the neutral position, The cylinder "should" be isolated if the valve is good. And its NOT GONNA DRIFT DOWN even if the seals are totally gone. It says something just like that in the article YOU linked.

 

[SPYDERLK]

Does your theory suggest no one has to replace the piston seals anymore.

So why are people replacing seals, just for the he** of it.

I'm just saying.

With bad piston seals you will see very hi pressure develop in a cyl holding against compression forces after a lift. In a valve centered position the seal leak allows the pressure to equalize on both sides of the piston. The net piston area is now the rod cross section. ... If youre experiencing repeated popped lines in transport of a load check the seals.
larry

 

[mach1rider]

Update........ Dealer did testing and found deep gouge inside one of the bucket rams, replaced ram and says its holding now.
Time will tell if they are correct.

 

[mach1rider]

Re: bucket drops UPDATE

So the dealer did not fix the problem at all and does not know when part will ever come. Have returned it for refund and bought a Cabela LM35H. Twice the tractor better more bells and whistles and only a couple grand more. The plus really is NO computerized crap on it.

 

[beenthere]

Re: bucket drops UPDATE

Will be interested to hear how the Tong Yang Moolsan company does for you.

 

[bigtiller]

Re: bucket drops UPDATE

Will be interested to hear how the Tong Yang Moolsan company does for you.

They have been making agricultural machinery since way back in 1968 and have been selling their products in the U.S. since 2004. Look out JD, CIH, NH and Kubota, TYM is sneaking up behind you.

 

[mach1rider]

Re: bucket drops UPDATE

Will be interested to hear how the Tong Yang Moolsan company does for you.

Sadly it seems that JD has gone the way of the car manufactures, Deny that there is a problem till someone gets hurt. the family has had JD tractors for more than 5 decades and yes they are older models but solid work horses with simple care. What I found with the new JD I purchased is lack of honesty in the dealer and the corp for the product.
Trying to pass along the excuse that it falls within JD spec's is just wrong. If they wish to build unsafe equipment, That is on them but I don't have to buy it or their excuses so maybe its time to give the other companies a chance.