Hydraulic Cylinder Leak Down on Box Blade???

[Leejohn]

If I did put a large shock load on the cylinder like that, I would think the tractors relief valve would open and allow the cylinder to move?

That part is not right because the work port are closed. Everything is blocked from there back.

 

[Piston]

Just to be clear here, the rod was extending, not retracting?

As far as the safety concerns others may have regarding those relief valves, all I can say is that I have sold several replacement cylinder units that I have made up for a couple hundred $$ vs the $500+ that Woods wants for their replacement and as of yet, no one has contacted me with any sort of problems. That's not to say that there won't be, but none so far.

The rod itself was retracting when the scarifier bar was lowering under its own weight. I think I messed up the wording in my last post.

However, with the cylinder on my bench and hoses connected, I was able to pull the rod out of the cylinder by hand. I did not need to bleed the lines at all.

 

[Piston]

If I did put a large shock load on the cylinder like that, I would think the tractors relief valve would open and allow the cylinder to move?

That part is not right because the work port are closed. Everything is blocked from there back.

Ahhh, that makes sense.

 

[Piston]

Just to be clear here, the rod was extending, not retracting?

As far as the safety concerns others may have regarding those relief valves, all I can say is that I have sold several replacement cylinder units that I have made up for a couple hundred $$ vs the $500+ that Woods wants for their replacement and as of yet, no one has contacted me with any sort of problems. That's not to say that there won't be, but none so far.

I really don't anticipate it being an issue, and if it is, it's clearly operator error for not having the cylinder retracted all the way which engages the lock mechanism when the scarifiers are down.

 

[MtnViewRanch]

The rod itself was retracting when the scarifier bar was lowering under its own weight. I think I messed up the wording in my last post.

However, with the cylinder on my bench and hoses connected, I was able to pull the rod out of the cylinder by hand. I did not need to bleed the lines at all.

You would be able to extend the rod with the relief valves wedged open. What is so odd is the ability for the rod to retract. The only way that is even possible is if there was air in the cylinder, a LOT of air.

Here is an example that everyone can understand. Cylinder full of fluid with rod extended = a glass of water full to the top. Now if you can put your finger into that glass of water with out spilling any, then that is how the rod can be pushed back into a fluid filled hydraulic cylinder.

In other words, it is impossible for the rod to be pushed into the cylinder. It is only possible if there is a void. (air) Glass of water is not full.

 

[jenkinsph]

You would be able to extend the rod with the relief valves wedged open. What is so odd is the ability for the rod to retract. The only way that is even possible is if there was air in the cylinder, a LOT of air.

Here is an example that everyone can understand. Cylinder full of fluid with rod extended = a glass of water full to the top. Now if you can put your finger into that glass of water with out spilling any, then that is how the rod can be pushed back into a fluid filled hydraulic cylinder.

In other words, it is impossible for the rod to be pushed into the cylinder. It is only possible if there is a void. (air) Glass of water is not full.

The finger in the glass of water is a good analogy. I do not recommend sticking your finger in a hot cup of coffee though.

The ball check will allow the cylinder to extend easily allowing the rippers to raise easily. The ball check will block the flow of oil when retracting.

I suspect that Matt will be buying the replacement cylinder at some point. While I use this same box blade frequently I do occasionally miss the latch and have the rippers raise up. When it happens to Matt he will likely bend up his linkage. He has been warned though.

 

[jenkinsph]

I think I have an explanation as to what happened. If the box blade was not raised up off the ground the rippers and the cylinder did not have a full stroke.

 

[Piston]

You would be able to extend the rod with the relief valves wedged open. What is so odd is the ability for the rod to retract. The only way that is even possible is if there was air in the cylinder, a LOT of air.

Here is an example that everyone can understand. Cylinder full of fluid with rod extended = a glass of water full to the top. Now if you can put your finger into that glass of water with out spilling any, then that is how the rod can be pushed back into a fluid filled hydraulic cylinder.

In other words, it is impossible for the rod to be pushed into the cylinder. It is only possible if there is a void. (air) Glass of water is not full.

I see what your saying. So because of the additional volume of 'space' that the rod itself occupies, there would HAVE to be some amount of air in the cylinder in order for it to retract. So the combination of that ball check valve being stuck open, and the fact that there MUST have been air in the cylinder, is why it could retract so quickly under it's own weight.

The finger in the glass of water is a good analogy. I do not recommend sticking your finger in a hot cup of coffee though.

The ball check will allow the cylinder to extend easily allowing the rippers to raise easily. The ball check will block the flow of oil when retracting.

I suspect that Matt will be buying the replacement cylinder at some point. While I use this same box blade frequently I do occasionally miss the latch and have the rippers raise up. When it happens to Matt he will likely bend up his linkage. He has been warned though.

I have actually done that same thing a handful of times with my Landpride 3578 as well. I imagine that cylinder was similar and had these two ball check valves in the same fashion. Obviously the manufacturer puts those two ball checks there for a reason, and they probably aren't 'supposed' to be sealed off with JB Weld. :laughing:
Your right though, I've been warned, and when the day comes that I do bend something up, I'll be sure to let you know so you can say "I told you so".

 

[jenkinsph]

We all learned something here. Under normal operation if you had air in the cylinder to evacuate you could raise the box blade up to clear the rippers and hold it for a second or two and it would purge any air from the lines. One time with the rippers fully down would do this.

Matt, I recommend you look carefully at the linkage in operation and decide which is cheaper to fix. Those parts along with the piston itself could get expensive. I would see if a new piston with valves could be purchased separately. I have never used JB Weld for anything so don't know whether you could remove it or not.

 

[ovrszd]

Just to be clear here, the rod was extending, not retracting?

As far as the safety concerns others may have regarding those relief valves, all I can say is that I have sold several replacement cylinder units that I have made up for a couple hundred $$ vs the $500+ that Woods wants for their replacement and as of yet, no one has contacted me with any sort of problems. That's not to say that there won't be, but none so far.

He had previously said "retracting". And by the video, it appears to be "retracting" (getting shorter). This is the scenario that several knowledgeable hydraulic members have said is impossible. I'd like some clarity on that subject as well. :confused3: