Cheap FEL cylinders keep bending

[npalen]

i agree, even pressure relief should be stopping them before allowing them to get to that point

Yes, the pressure relief should be protecting the cylinders IF the valve is being used. The relief valve won't protect, however, in the case where backdragging is being done with the valve closed. What I mean is that the relief on the valve only protects when the valve spool is in other than the centered position.

 

[4570Man]

Oh so many things jumps out at me after seeing all the images…

Notice the holes… why are they unused?

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When it should have these brackets in place like these…

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Somebody screwed up at the dealership.

Nobody screwed up at the dealership. The cylinders are non interchangeable. Some bean counter at the manufacturer made a deliberate effort to do this.

 

[JWR]

"a given force will make it buckle regardless of what its attached to."

I certainly agree with that statement. It's interesting how all the cylinder rods bend "down" as if the weight of the cylinder is the determining factor but I think friction in the front pivot joint also contributes.

I do think, however, that the extra link keeping the cylinder rod farther from the pivot joint allows it to take more torque without buckling. I say this because the force produced by a given torque diminishes as the lever arm length increases.

Without the extra link, the cylinder rod will almost fall down on top of the pivot point when it is fully extended. The cylinder rod doesn't stand much of a chance when this close to the pivot.

Yep, concur. Making the failure less likely is worthwhile I would think. My second photo in post #116 shows the extremely extended cylinders right down against the tip end of the loader frame. You'd think some forward scraping, hitting an object like concrete, or down force by the loader while the tip of the bucket is on a rock or log , etc. that I mentioned earlier could potentially bend the cylinder rod upward (arched down over the end of the loader frame) but the cases seen so far are bent in the other direction -- downward.

 

[npalen]

Yep, concur. Making the failure less likely is worthwhile I would think. My second photo in post #116 shows the extremely extended cylinders right down against the tip end of the loader frame. You'd think some forward scraping, hitting an object like concrete, or down force by the loader while the tip of the bucket is on a rock or log , etc. that I mentioned earlier could potentially bend the cylinder rod upward (arched down over the end of the loader frame) but the cases seen so far are bent in the other direction -- downward.

My second photo in post #116 shows the extremely extended cylinders right down against the tip end of the loader frame.

Yes, that picture definitely shows the issue. Assuming a distance of 24" from bucket tip to the pivot pin and 4" from the cylinder rod to the pivot pin gives a ratio of 6:1. So, assuming a point load on the bucket tip of 1000 lbs would produce six times that or 6000 lbs compressive load on the cylinder rod. The load on the cylinder would be reduced by half if the rod was 8" from the pivot pin. Might still bend the rod if too small of diameter.

The rod diameter is, as several mentioned, very important. A 1-1/4" diameter rod, for example, is 56% stronger than a 1" diameter rod.

 

[LD1]

My second photo in post #116 shows the extremely extended cylinders right down against the tip end of the loader frame.

Yes, that picture definitely shows the issue. Assuming a distance of 24" from bucket tip to the pivot pin and 4" from the cylinder rod to the pivot pin gives a ratio of 6:1. So, assuming a point load on the bucket tip of 1000 lbs would produce six times that or 6000 lbs compressive load on the cylinder rod. The load on the cylinder would be reduced by half if the rod was 8" from the pivot pin. Might still bend the rod if too small of diameter.

The rod diameter is, as several mentioned, very important. A 1-1/4" diameter rod, for example, is 56% stronger than a 1" diameter rod.

Actually if you look at the direct pin bucket for this same loader frame....it looks to be about twice the pivot distance as the 4-bar. Reference pics in post # 116 and #120.

So they did account for the longer cylinder by giving the bucket LESS mechanical advantage over the cylinder that now has a longer rod.

Looking at the two loaders side by side....its tough to tell which one would buckle easier, since that is a function of length vs rod diameter as already been discussed...(and hopefully that horse is dead).

Obviously the rod without the 4-bar will buckle under LESS compressive load since it is LONGER and presumably the same diameter.

BUT, the mechanical advantage of the loader over that 4-bar link appears to be about twice that of the direct pin. So as in your example...point load the bucket in the 4-bar with 1000 pounds and you are putting 6000 on the cylinder. Do the SAME thing with the direct pin and you are only putting about 3000 pounds on the cylinder.

So we simply have 6000# on a short cylinder....or 3000# on a long cylinder....which one would buckle first. Thats the great mystery that cannot be solved without some better measurements which I have no way of attaining.

 

[npalen]

Actually if you look at the direct pin bucket for this same loader frame....it looks to be about twice the pivot distance as the 4-bar. Reference pics in post # 116 and #120.

So they did account for the longer cylinder by giving the bucket LESS mechanical advantage over the cylinder that now has a longer rod.

Looking at the two loaders side by side....its tough to tell which one would buckle easier, since that is a function of length vs rod diameter as already been discussed...(and hopefully that horse is dead).

Obviously the rod without the 4-bar will buckle under LESS compressive load since it is LONGER and presumably the same diameter.

BUT, the mechanical advantage of the loader over that 4-bar link appears to be about twice that of the direct pin. So as in your example...point load the bucket in the 4-bar with 1000 pounds and you are putting 6000 on the cylinder. Do the SAME thing with the direct pin and you are only putting about 3000 pounds on the cylinder.

So we simply have 6000# on a short cylinder....or 3000# on a long cylinder....which one would buckle first. Thats the great mystery that cannot be solved without some better measurements which I have no way of attaining.

Not sure we're on the same page here. The "pivot distance" that I'm referring to is the distance from the bucket pivot pin extending perpendicular to the centerline of the cylinder. That distance is clearly much more on the "4-bar".
I can't tell any difference in the length of the cylinders in the two photos. Is there any difference in the rod diameters? Someone may have mentioned that above. These long threads get a bit confusing.

 

[JWR]

Not sure we're on the same page here. The "pivot distance" that I'm referring to is the distance from the bucket pivot pin extending perpendicular to the centerline of the cylinder. That distance is clearly much more on the "4-bar".
I can't tell any difference in the length of the cylinders in the two photos. Is there any difference in the rod diameters? Someone may have mentioned that above. These long threads get a bit confusing.

I think I understand what you are saying, npalen, that the 4-bar gives the cylinders an 8" lever to push against versus only about 4" when the 4-bar linkage is not there (relative to the pivot point.) Not that the 4" or 8" are exact but that means roughly a 2:1 better mech advantage for the cylinders with the extra linkage. That's the same thing I said in post 115 in a bold face OBTW when that lightbulb went on for me.

 

[LD1]

Not sure we're on the same page here. The "pivot distance" that I'm referring to is the distance from the bucket pivot pin extending perpendicular to the centerline of the cylinder. That distance is clearly much more on the "4-bar".
I can't tell any difference in the length of the cylinders in the two photos. Is there any difference in the rod diameters? Someone may have mentioned that above. These long threads get a bit confusing.

No we arent.

I am talking about the distance from where the cylinder hooks to the bucket in relation to the pivot.

Where the 4-bar link attaches to the bucket is ALOT closer to the bucket/boom pivot than the direct pin.

If the bucket was only dumped half way.....the direct pin would have alot greater mechanical advantage.

At full dump or full curl the 4-bar would have the advantage. The lines would cross somewhere in between. It becomes a very complex computation to calculate, because you are taking a linear force and trying to convert it to a rotational force.

Not dissimilar to a piston, rod, and crankshaft in the engine. If the crankshaft is at perfect 180 degrees....you could put as much force on the piston as you wanted and it wont move. IF the crank were at 90 degrees....a pound of force equals way more rotational force going into the crank than say a pound of force on the piston if the crank were at 20 degrees.

And the above is infinitely variable. FULL dump is gonna have a different equation/value than say 2 degrees less than full dump.

 

[LD1]

I think I understand what you are saying, npalen, that the 4-bar gives the cylinders an 8" lever to push against versus only about 4" when the 4-bar linkage is not there (relative to the pivot point.) Not that the 4" or 8" are exact but that means roughly a 2:1 better mech advantage for the cylinders with the extra linkage. That's the same thing I said in post 115 in a bold face OBTW when that lightbulb went on for me.

Think of it as more of a variable lever. Since you are converting linear motion into rotational motion. Similar to the engine/crankshaft I mentioned above. Or even a bicycle and pedals. When the pedals are near the top and bottom of their stroke...it takes alot more force from your legs than if the pedals are at 90 degrees (front and back).

What the 4-bar DOES do is make that variable lever vary a whole lot less. Think of a 4' long prybar that you can grab anywhere. From 1/2 a foot all the way to 4' out for most leverage. That would be a direct pin bucket. Whereas a 4-bar would be more like only being able to use the lever from 2.5-3.5'.

Goes along directly with what I said in post #87

With a direct pin, at full dump and full curl power drops off. The rollback force is a parabolic arc. With the greatest force right in the middle of its range of travel. At full dump and full extend....the pins are getting ever so close to being in alignment.....thus reducing force.

The 4-bar solves not only that problem....kinda flattening the curve of rollback force, but also allows greater articulation. Like upwards of 160-170 degrees of bucket rotation instead of 120-130 degrees of bucket rotation.

 

[Jchonline]

Tractor FELs are unsupported directly by the frame in any position. When you push against something, those forces come straight up to the FEL mount points beside the operator station. The entire FEL arm with its own angles/joints is put under these forces. The weakest point will break, and that is usually the cylinder arm. If you had the Cylinder fully retracted, it would be somewhere else. It is not smart to use your tractor FEL to PUSH on anything that is very heavy. A mound of dirt is fine. A stump in the ground is not. Tractors are meant to pull.

A skid steer/track loader in its lowest position allows the loader arms to rest squarely against the front of the frame. So when you are pushing something there is no play, no force directly on the loader arms. These machines are meant to push.