Bucket Drop

[Gem99ultra]

While using my L3400 to load up a bunch of limbs with the bucket about 3' in the air for loading convenience, the bucket suddenly let go and dropped to the ground! Glad I wasn't under it. No prior warning, no shuddering, everything seemed to be working just fine.

Before and after that incidence, the FEL worked just fine, no hick-ups. Later, I checked the 3-pt. fluid and discovered that it was about 3 gallons low. Do you think that's what caused the failure? Or should I be looking for a different problem?

Thanks in advance for any advice.

 

[Henro]

I do not think it would be a fluid level issue, as the cylinders would be full and the control valves closed. The bucket will stay up when the engine is off...some stay up longer than others, depending on the leakage in the control valves.

How fast did it drop? The same speed as if you put you control valve in float position?

That is a scary thing to happen. I am guilty of sometimes using my bucket to hold a plank, sort of like a portable scaffold. Have also used it as a pseudo work platform at times...

My gut is pointing my mind at the control valve, but I cannot offer any real help on what to look for.

Hope you find the solution soon! I have always worried about a possible hose failure when standing in my bucket, but NEVER really considered something else as having the same effect...

Bill

 

[teg]

Wow, I would like to know how this happened, too. I've had low oil (3+ gallons) and the tractor worked fine. The oil pickup must be pretty low in the reserve.

So no one was around to play with the controls? :confused3: What did you hear? and I assume you saw it drop?

 

[Gem99ultra]

Wow, I would like to know how this happened, too. I've had low oil (3+ gallons) and the tractor worked fine. The oil pickup must be pretty low in the reserve.

So no one was around to play with the controls? :confused3: What did you hear? and I assume you saw it drop?

Yeah, I was in front of the bucket and son was tossing limbs into it from the side. No-one else around it. It dropped like I had pulled the lever, same as it would in float position. No crunching, no nothing; just a 'swish' and down it came.

I've left the bucket raise for long lengths of time in the past and never had it drop an inch. The tractor had not been used much all winter... do you suppose the control valve might have just been a bit sticky?

 

[teg]

...do you suppose the control valve might have just been a bit sticky?

No. Did you notice the joystick when you got back on the tractor? Was it locked in Float position or was it in the middle, like normal? Wondering if a thrown (or falling) branch might have wrapped around the steering wheel and knocked the joystick into Float....

 

[Gem99ultra]

No. Did you notice the joystick when you got back on the tractor? Was it locked in Float position or was it in the middle, like normal? Wondering if a thrown (or falling) branch might have wrapped around the steering wheel and knocked the joystick into Float....

Son was standing by and was the first one to check the joystick, so I really can't say about the position. The last motion was to lift the bucket, so putting it in float position wouldn't have been a normal motion.

 

[stuckmotor]

I've got to quit walking under my loader.

 

[teg]

Was the engine running or turned off? Basically, the valve is the only thing that lets oil in or out of the cylinders (other than a broken hose or leaking cylinders). Leaks around "O" rings in the valve are usually slow. Let us know if it happens again...

 

[repete]

Would an internal failure of a cylinder seal cause this as fluid rapidly goes from one side to the other? Seems odd that the failure could not be repeated.

 

[rswyan]

Would an internal failure of a cylinder seal cause this as fluid rapidly goes from one side to the other? Seems odd that the failure could not be repeated.

Would require the failure of two seals ... one for each side of the loader.

 

[repete]

Would require the failure of two seals ... one for each side of the loader.

I thought they were tied together hydraulically after the valve, one line out of the valve and then a tee to each cylinder. I did not realize there were independent valve outputs.

 

[KennyV]

I thought they were tied together hydraulically after the valve, one line out of the valve and then a tee to each cylinder. I did not realize there were independent valve outputs.

If one side was leaking internally it would go down SLOW as the fluid volume from Both cylinders would have to go through the one leak. KennyV

 

[repete]

If one side was leaking internally it would go down SLOW as the fluid volume from Both cylinders would have to go through the one leak. KennyV

My thought as well. It could be the cause but there is no way it would recover and function normally from that type of catastrophic cylinder failure which caused an immediate drop.

 

[Henro]

What's the chances that a cylinder seal failed and then fixed itself? I suppose that is possible...

But, I am not sure a cylinder seal failure would cause the bucket to fall anyway. The cylinder has two volumes, the piston side is larger than the rod side

If the control valve seals off each side of the cylinders, in order for the cylinder to move in the direction of the bucket falling, the excess fluid in the loader cylinders and hoses must go somewhere. and there is no where for it to go, if the control valve seals off the lines properly.

The piston side of the cylinder is on the bottom, and when the loader goes down the amount of fluid that exits from the piston side of the cylinder is greater than the amount of fluid that enters the rod side. In normal operation the difference is sent back to the hydraulic tank.

So if one cylinder failed, and became essentially the equivalent of a hose, there still would be no place for the excess fluid to go from the good cylinder, because when the rod tried to move into the good cylinder, the fluid expelled from the piston end of that good cylinder would be more than could go into the rod end, and the cylinder would lock...

My take on it anyway...

Bill

 

[Henro]

Second thought:

Even if both cylinders failed, and leaked internally, the loader would still probably not fall freely, as when the cylinder rods tried to go into the cylinders, there would be excess fluid volume generated that would have to go somewhere in order to make space for the cylinder rods.

In my mind the rapid drop must lead back to the control valve as being the cause. Either because it failed and fixed itself, or because something caught on the control lever and moved it into the lower or float position, for the time it took the bucket to drop...Lower position being more likely, as float has an indent that holds the lever in that position...

Bill

 

[Henro]

Just went out to do something with my tractor and looked at the loader lift cylinders. WHOOPS! I should never trust my memory! The rod side is on the bottom!

Everything I stated with respect to volume of fluid is correct, but we need to consider whether the reversed position of the cylinders voids the conclusion...

OK, I think the net result is the same. When the cylinder retracts, more fluid goes out one end than goes in the other. So the net affect is the same...if the fluid has no where to go, the cylinder will lock...

What do you guys think? Hydraulics is just a hobby at this end...but I am pretty sure I have a fair to good grasp of the principles...

Bill

 

[JWR]

I've got to quit walking under my loader.

You and me both !! I can think of SO MANY times I thought about the risk and went under that bucket for whatever thing of the moment. That is plain scary !

 

[JWR]

I'm going to expose my ignorance by asking a couple of questions on this one: All predicated on "Maybe the low fluid was the culprit after all..." 1) Will the hydraulic pump move air ? If YES then maybe the pump sucked some oil and then some air from the sump because the level was low. Then the cylinder fed by air and oil would go ahead and lift the bucket (being under very light load) and at that point have some oil and some compressed air in the cylinder. That leads to question 2) Is there reason why hydraulic cylinder seals might refuse fluid bypass and yet allow air to leak by ? I'm guessing YES when fluid pressure gets on the order of a few thousand psi and you never see air pressure that high and if you did it would be super hot. You can see where I'm headed ... maybe it took a little while (facilitated by very little/no load in the bucket) for a compressed air bubble highly compressed and very hot to make a path thru the oil to the seals and then "Puffffft !" ??? If it did the hot air breach of the seal would probably open a path, if only temporary, for fluid to go past the seal as well. Just a thought.

 

[JWR]

I thought they were tied together hydraulically after the valve, one line out of the valve and then a tee to each cylinder. I did not realize there were independent valve outputs.

You are correct, it is a tee after the control valve to both cylinders. There are not separate valve outlets for each cylinder.

 

[Gem99ultra]

Interesting evaluations by the above knowledgeable members... and I certainly appreciate that.

The loss of hydraulic fluid I surmised was due to a long term leak at the rear remote control valve. Nothing big and ongoing. At this point, I'm just guessing that the joystick must not have been solidly in the neutral position.

Any other thoughts are certainly welcome. But "Lesson Learned" here is that I will not under any circumstances allow myself or anyone else, under a raised bucket. What was simply a head-shaker could have easily been a fatal accident.