Backhoe problem

[2515R Dude]

Wow. Good Videos. That is a lot of unnecessary mechanical movement. Way more than normal for a BH. The swing system is normally much tighter. Here we've been looking at the hydraulics and it may be that the mechanicals need attention first. There is enough movement to make me wonder if one or both of the swing cylinder mounting bushings is missing. It could also be enough play that the slop is what you are seeing and not some sort of air cushion effect at the end of the swing.

I'd replace the bushings in the swing system pivots first. Or make yourself some new ones. And while you have the cylinder out, either disassemble the cylinder or somehow check that the rod is firmly attached to the piston - i.e. zero end play.

Once you get the mechanical slop minimized the hydraulics may make more sense.

rScotty

Yes, It was my first thought, and dealer agree that the play in the piston connections is too much, we disassembled it and there is absolutely NO bushing. Just a hole and the pin goes through it. The Branson also confirmed there is no bushing supposed to be.

Also, if you look at the second video where i recorded where the pistons are going out, you can notice that the piston goes out fast at the beginning, then slows down. hard to see, but it is there.


Now there is some update:
Today i was working with the BH for 4-5 hours. What i noticed and it made me think, it is not that the boom slows down, it looks like it starts too fast, then after 1/5 of the turn it gets to the normal speed, then at the last 1/5 turn it jumps to run too fast.

It is like excessive pressure going to the rams at the beginning and at the end of the swing/cycle.. I was running 1800-2100RPM.
first it was jumping like creasy, then go to the acceptable speed, then jumps again and slams to the tractor so hard, it even bent the step. the buffer could not the impact so violent it was, See the picture.
Can it be excessive pressure?

 

[ning]

I see it smashed on one side, but not the other. Does the swing only get paused in one direction or both?
I'm starting to agree that the flow may be too high here. My backhoe's boom was occasionally crazy when dropping and was like a bucking bronco, it would drop really fast if I wasn't careful and would suddenly stop in a similar fashion.

If you split the flow by operating two valves at once - like bucket curl at the same time as you do the swing - does the jerking still happen?
If so, put restriction valves on the swing so you can slow it down a bit.

Now why this is suddenly acting this way is a different question...

 

[oldnslo]

2515
Have you tried intentionally putting the hoe in a position like sitting on a slope so that the hoe is fighting gravity to swing uphill? When swinging uphill working against gravity does it still change speed?

Do you have equipment and capability to install a pressure gauge in pressure line to the hoe valve?

Curious to see what pressure is doing while hoe changes speed.

 

[ericm979]

The BH760 on my 3725 was too fast and jerky for some motions. Raising and lowering the boom jerked the whole tractor around. When I curl the bucket up the last bit of travel goes faster and the bucket slams into the stop, ejecting most of the contents. I think that one is due to the varying leverage because of the linkage. I put adjustable restrictors on both ends of the boom cylinder and extension side of the curl cylinder to make it run more smoothly.

As I got better with the backhoe I was able to use two or three motions at the same time which smoothed out operation some but did not fix it. I think the problem with mine is cheap valves which don't feather very well, and no internal stops in the cylinders.

My boom swing has a little play in it but not like yours, and the cylinders move evenly.

I think that even with the poorest quality valves the cylinders should move consistently once the valve is open. I think something is wrong with yours.

 

[2515R Dude]

I see it smashed on one side, but not the other. Does the swing only get paused in one direction or both?

Both the same , no difference as i can see

If you split the flow by operating two valves at once - like bucket curl at the same time as you do the swing - does the jerking still happen?
If so, put restriction valves on the swing so you can slow it down a bit.

Now why this is suddenly acting this way is a different question...

ILL try it tomorrow, and yes, why it suddenly happened, especially when Branson say it is correct behavior . Why it was not happening before and don't happen to you guys.

2515
Have you tried intentionally putting the hoe in a position like sitting on a slope so that the hoe is fighting gravity to swing uphill? When swinging uphill working against gravity does it still change speed?

YES, I tried, no changes. The only change I noticed - if I drug the bucket on the ground, today I was working dry creek bad, so all gravel, the boom swings steady, no jumps or any crazy behavior. It is why I started thinking about excessive pressure.

Do you have equipment and capability to install a pressure gauge in pressure line to the hoe valve?

Curious to see what pressure is doing while hoe changes speed.

IT is what the dealer promised to do after July 4th.

 

[rScotty]

Yes, It was my first thought, and dealer agree that the play in the piston connections is too much, we disassembled it and there is absolutely NO bushing. Just a hole and the pin goes through it. The Branson also confirmed there is no bushing supposed to be
Also, if you look at the second video where i recorded where the pistons are going out, you can notice that the piston goes out fast at the beginning, then slows down. hard to see, but it is there.

The outer pivot pins on the cylinder should fit tight in that hole in the swing frame. If wear makes that fit sloppy - caused by not greasing the zerk there enough or doing a lot of side sweeping - then the usual fix is to replace the bushings.
BTW, backhoes aren't set up to do heavy side sweeping. It makes new ones old before their time.
Sincy yours doesn't have bushings on those external pivot pins.... if you keep it youcan put bushings there if you are handy that way.
Are you saying that there is also endplay in the piston connecting rod? Can you wiggle the piston rod back and forth inside the cylinder with just hand pressure? If so, very very not good.... But it would sure explain how it could change sweep speed. The fix involves openin up the cylinder to get to the insides so as to be able to tighten the rod nut.

Now there is some update:
Today i was working with the BH for 4-5 hours. What i noticed and it made me think, it is not that the boom slows down, it looks like it starts too fast, then after 1/5 of the turn it gets to the normal speed, then at the last 1/5 turn it jumps to run too fast.

Glad you were working it. After all, it isn't perfect but beats no backhoe. We had an old beat up 3pt hoe for years that was sloppy as hell but still useful. It would shimmy like a snake. Finally sold it to a friend who used it another decade. Eventually he and I both bought JD310s with thumbs. Over beers last week he and I were trying to figure out what took us to long to get smart.

It is like excessive pressure going to the rams at the beginning and at the end of the swing/cycle.. I was running 1800-2100RPM.
first it was jumping like creasy, then go to the acceptable speed, then jumps again and slams to the tractor so hard, it even bent the step. the buffer could not the impact so violent it was, See the picture.
Can it be excessive pressure?

It is probably not excessive pressure. Back in message #27 you mentioned that the BH pressure was coming from the PB port on the FEL control valve. That PB port pressure is controlled by the same pressure relief valve that sets your working maximum pressure everywhere on the tractor. My guess is that although the relief valve is set to around 2800 psi , you are probably using half that or less to make an unloaded swing motion. Only way to get it to max pressure for an instant is by stalling the swing with a heavy load. A simple change in speed won't go that high.

So if it is not excessive pressure, why is it slamming the stops? Well, two reasons - but only #1 counts.
1. Your hoe should have always had heavy rubber stops at both ends of the travel so that it cannot slam into the steps. Most backhoes have that. Sounds like someone forgot to put yours on. You could buy ones from from someone else's hoe then find the holes where yours should have been and mount them. Or else drill a hole & install a set.
Or use rubber stops for sliding barn doors....
Or a piece of 2x4 with a chunk from an old tire screwed onto it... Or whatever.

Do something, even if it is to wrap a towel around the step. That impact at full swing is half of what is chewing up your cylinder pivot pins. And it could have also loosened up the piston rod in the cylinder - or broke something inside there.

2. The other reason for slamming is design. Nothing you can do about that. The original swing geometry should have been designed so that a constant piston motion gives your hoe a controlled speed of swing even though the motion is through an uneven arc. Getting that sort of thing right requires some real pencil and paper skuill sweat and the designer probably assumed rubber stops plus no odd wear or slop. That's the engineering part. Not much you can do with that except use what you have, fix, and improve it.

Be interesting to see what the pressure show.

rScotty

 

[K5lwq]

Also, if you look at the second video where i recorded where the pistons are going out, you can notice that the piston goes out fast at the beginning, then slows down. hard to see, but it is there.

Could you make another video of the ram moving its full range? Also, one of the boom curl if that is still a problem?
BTW, You are getting good at making videos now. I see a YouTube channel in your future.

 

[K5lwq]

The reason I am asking for a new video is can we actually see the cylinder pause or is it a combination of slop and geometry.

The swing moving faster at the beginning and slower in the middle would be expected to a degree. It depends on the geometry that we can not see in the video.

But when the cylinder is pushing straight out it will move the boom farther with less cylinder movement than when it is in the arc and the cylinder has to move side to side as well as extending. This slight difference will be more noticeable looking at the tip of the boom than at the cylinder.

I do not know if we have determined that the cylinder pauses or not. Until that is determined we do not know if this a hydraulic problem or a mechanical issue.

If it is the geometry then Branson’s response would be somewhat correct. Then slowing things down would help make it more manageable. Also learning how to feather the control valve at the beginning and end of each movement. Some people just move the valve full open to swing then just let go of the handle to stop. This makes for a rough ride.

 

[2515R Dude]

Last update, after 30 minutes of work

 

[K5lwq]

Wow! Now to find out why? Hopefully the dealer will get TYM to warranty this now. I am thinking the slop and slamming is the contributing factor. Good thing you had him look at it and video the issue.

 

[sd455dan]

Last update, after 30 minutes of work

So TYM corporate said this is normal operation.?.
Bet they rethink that after the dealer sent the pic of the rod...

"it immediately starts moving really fast, then at about 1/5 of the way it slowed down almost to the stop, moving really slow with some hesitations on the way almost to the end, and the last 1/8 of the way it moves faster to the end.

My dealer recorded a video and sent it to the branson/tym.
As i expected branson try to shake of any claims.

They say it us supposed to be like that"

 

[rScotty]

Last update, after 30 minutes of work

"......That impact at full swing is half of what is chewing up your cylinder pivot pins. And it could have also loosened up the piston rod in the cylinder - or broke something inside there."

Ah yes... well, bit congratulations on your determination. And you can cancel the friendly dealer's pressure test. It will be interesting to see what the Branson tech has to say. Just looking at it, my first guess is a classic compression failure - being close to a 45 degree angle and in the middle of the rod. Compression failures often start with a microfracture which grows in exactly that manner. A tension failure would be more likely to be a classic cup/cone and have some measureable necking.

In the Branson tech's defense, that is NOT a common type of failure. The whole group of us here on TBN only listed a rod failure as a "maybe"....not an absolute. My own guess when I saw the video showning what looked like excessive end play was that the rod-to-piston fixation was coming loose inside the cylinder. I never thought of the failure you are seeing. It has to be rare; backhoes get slammed around a lot in normal use.

rScotty

 

[2515R Dude]

It broke approximately at 11 o'clock swing to the left. Question is, why the release valve did not open? It should be excessive pressure to do such damage

 

[rScotty]

It broke approximately at 11 o'clock swing to the left. Question is, why the release valve did not open? It should be excessive pressure to do such damage

Which cylinder is this? Are you saying it broke all of a sudden? That must have been a surprise what happened?

I'm not sure that the release valve is involved in this failure, because I'm not yet convinced that type of rod fracture can be caused by the tractor's hydraulic system pressure - with or without the release valve working.
But I could be wrong. If you send some measurements for the rod length, diameter, and same for the piston OD or cylinder ID, then someone can do some rough calculations to ballpark the hydraulic pressures required to break the rod that way.
rScotty

 

[2515R Dude]

What other forces could brake this in the middle of swing with bucket of gravel on flat ground?

 

[oldnslo]

Was the rod that broke still fully attached to the piston? Is the other cylinder rod properly attached to the piston.

 

[JRP3]

If you put the pieces back together and put a straight edge on it is it straight? Wonder if it got bent somehow which might explain the uneven movement and subsequent breakage.

 

[Rich B1]

That rod failure is a mechanical issue with the backhoe. Either the stops are poorly located or the geometry sucks.

The backhoe should mechanically stop swinging before the cylinder bottoms. If it doesn’t, you bend rods or pop pistons off the rod. It may be a design issue or a manufacturing issue, or both.

The cylinders should not be side loaded by the backhoe while swinging. If they are, you fail things.

Your dealer needs to be heavily involved. If this is inherent design issues, you may need to ask for a return of the backhoe.

 

[rScotty]

I'm not sure that the release valve is involved in this failure, because I'm not yet convinced that type of rod fracture can be caused by the tractor's hydraulic system pressure - with or without the release valve working.

What other forces could brake this in the middle of swing with bucket of gravel on flat ground?

The relief valve only protects against over-pressure from the tractor's hydraulic pump .... and depending on the design, sometimes from hydraulic shock loads. The relief valve could be working fine and there still be other purely mechanical forces large enough to break the rod.
They other forces are probably more important now that the rod has broken because they are mechanical functions of the geometry of the backhoe. That is dealer and designer stuff.

One set of forces would happen if the rubber swing stops are not positioned right. You can see those rubber cushions in several of the photos. Those might be poorly located and allow the swing motion to stop by smashing into something solid instead of the cushion. That could start a fracture in the rod. Once a fracture starts, it doesn't take much repeated stress to make it grow. Just repetitions and time.
Or if the cylinder rods were bottoming out internally before the swing stops. That could do it.

Also, something less obvious could be putting side force on the cylinder rod. For example, the open end of the rod has to rotate around a pin. Does it have enough rotation or does something stop the rotation and cause the rod pin end to bind before the end of the swing? I've made that mistake myself.

That rod failure is a mechanical issue with the backhoe. Either the stops are poorly located or the geometry sucks.

The backhoe should mechanically stop swinging before the cylinder bottoms. If it doesn’t, you bend rods or pop pistons off the rod. It may be a design issue or a manufacturing issue, or both.

The cylinders should not be side loaded by the backhoe while swinging. If they are, you fail things.

Your dealer needs to be heavily involved. If this is inherent design issues, you may need to ask for a return of the backhoe.

All good ideas.

Dude also asked "What other forces could break this in the middle of a swing with a bucket of gravel.....?"
Well, there are also hydraulic forces that happen due to sudden changes in motion - especially when you close the valve and the swing suddenly stops. Having a load of gravel in the bucket makes those forces larger. Think of water hammer in house plumbing. Hydraulic forces from abrupt changes in motion are smaller than the mechanical ones of slamming against a stop - but still large. If the cylinder rod already had a crack growing from some other cause, those forces could be enough to cause it to come apart in the middle of a swing.

Or maybe you were just unlucky and got a rod with a defect. It happens, but that might be the best news of all. My guess is that the dealer is still involved in any of thes things.

Luck,
rScotty