broken hydraulic cylinder on BL4690 backhoe

[bigbenkubota]

So first post ... I bent the rod on the boom/crowd hydraulic cylinder. This is a BL4690 backhoe mounted on my L3710. I don't have a ton of experience with hydraulics and have a few questions.

First, I couldn't run the backhoe with the Kubota controls as most of my time has been on a Yanmar excavator. I switched hydraulic lines to change the joystick controls to the SAE layout after reading a couple posts (dipper swapped with lift). Because of how tight things are and not knowing any different, I pulled only the very end of the lines off and didn't move the inner fittings or restrictors. Did I screw something up by not moving everything? From the manual, it now looks like the dipper has a restrictor on the upper hose while the lift has the same restrictor on the lower hose.

Second, after researching the bent rod/cylinder, it sounds like this is somewhat common with this backhoe. Possibly most commonly when you're working close in to the tractor and curl the bucket. It seems like this would be more likely when you're close in, but pushing something away with the bucket. Either way I don't want this to happen again. I read about upgrading the hydraulic cylinder. The info I found did not appear to come up with clear info for part numbers, so I've taken measurements and found this cylinder:
http://www.surpluscenter.com/Hydraulics/Hydraulic-Cylinders/Double-Acting-Hydraulic-Cylinders/2x20x1-25-DA-HYDRAULIC-CYLINDER-WOLVERINE-WWXT2020-S-9-8771-20.axd.
Any thoughts on whether this would work? Or a better option? This cylinder retracted is 1" shorter than the Kubota cylinder, but with a 1" longer stroke (correct overall length). Could I add a 1" stop to the rod to make it the correct retracted length? Other than the dimensions I took, I don't know if they are the same pressure or hydraulic fitting types.

Alternatively I could just buy another Kubota cylinder for $357, but I hate having to worry that this will happen again. A new rod and seal kit would be around $160, but I don't know how to know that the internals of the cylinder aren't messed up too.

Other thoughts to either fix this or to keep this from happening again?

Sorry for the long first post...

 

[coachgeo]

This message got snagged as potential spam being so long and with a link thus it was automatically hidden from viewers by the spam software of this webiste. I just approved the post. Others can see it now and you'll get some replies from good people.

 

[rentthis]

This cylinder appears to be sae and Kubota Cylinders are metric. You would have to do several things to make the change. First, you would have to adapt fittings to the cylinder that would connect to the hoses or the hose ends could be made to connect to sae at the cylinder. The main problem I see is matching pins and pin bosses. I really don't know an easy way to do that. I think it would cost more than the extra $200.00 to buy the new Kubota cylinder

 

[rbargeron]

... I bent the rod on the boom/crowd hydraulic cylinder.......

First, the restrictors affect the speed of operation but not the maximum force that develops. How bad is the bend? Is some part actually broken? Can you post a pic? Bent cylinder rods can often be fixed.

 

[bigbenkubota]

Thanks for the cylinder info - is there another option that would work better? I believe the pins should work - the pin and the cylinder are both 1". I'm more concerned that it doesn't bend again over the cost savings.

Here's a pic:


Is this able to be straightened?

If I were to continue using the Kubota cylinder (either straightened or new) is there anything else I can do to prevent this again?

 

[bigbenkubota]

Regarding the restrictors - the new setup is probably smoother than before. So if their purpose is solely speed and didn't cause this, then that's a relief. I'd like the bucket curl in particular to speed up - would it be safe to remove the restrictor to do this?

 

[rbargeron]

The restrictors slow the flow in some circuits so the machine is less jerky - but the max pressure is the same. It takes less volume to retract than extend a cylinder - restrictors can be used to equalize motion speed.

The bent rod looks like it could be straightened. It's likely nothing inside is damaged. Probably doesn't even need new seals. In general it's less hassle to stay with the original cylinder rather than redesigning for something else. But if a different one will improve your confidence in the backhoe, pins and fitting adapters are cheap and easily available.

If it were mine I'd knock out the pin, take out the gland, take the rod & gland out, carefully straighten the rod in a press, use a straight edge to get it within say .030" over 2 feet. If there are scratches on the rod, file the high points off and fill any grooves with superglue. Put it back together and use it. Probably never happen again.

When I bought my first backhoe, the dipper rod had two slight bends in it. I used it a lot - never had a leak or other problem with it. Just sayin' Take care, Dick B

 

[D2Cat]

I've had rods bent like you show. I removed the rod and took it to a shop. He set it up in his press using brass pieces to be sure no marks were made on the ram. Came out fine, still using it today.

Ive also had the inside of a cyl. scratched. When I took it to the hyd. shop they said they would recommend it being replaced. (But they work on equipment like used at World's Of Fun, and have to back up everything they send out)

I took some emery paper and formed a roll. Cut the end of a 3/8" all thread and inserted the emery paper in it. I put a piece of heater hose over the rest of the threads. Inserted the rod in a variable speed drill and dressed the cylinder. Still using it also. No leaks, no problems.

Like Rbargeron said, take it apart, straighten it, clean it, use it!

 

[Tooljunkie]

I find it odd that the cylinder bent. Usually they are pretty robust.
Restrictors couldnt be playing a part in this as mentioned,but determining what caused it to bend will help prevent it from happening again. Like backing into something with tractor or pulling/tugging with tractor and cylinder extended as shown in your photo.

Had a friends baler bend two rams a few weeks ago, bad hydraulic controls forced the door and hinge bolts sheared. Once we repositioned door the rams returned and appeared straight. They were subjected to a lot of stress.

It would be difficult to determine what caused bend as l would have never noticed unless it affected operation or i watched it bend.

 

[bigbenkubota]

Thanks for the replies - i'll take it apart and see what I can do.

Now for the actual taking it apart part ...
I should be able to just pull the top pin, then rotate the rod so the retaining ring comes out, and pull it apart? I haven't had to do this before so any advice would be appreciated.

Also, what's the best position for the dipper/boom to be in? Rest the end on a sawhorse?

Regarding how it occurred - I can't say it was in any sort of extreme circumstance. I was trying to peel some rock so it was working harder than soft sand.

 

[rbargeron]

..... for the actual taking it apart part ...
I should be able to just pull the top pin, then rotate the rod so the retaining ring comes out, and pull it apart?........what's the best position for the dipper/boom to be in? Rest the end on a sawhorse?

Take the pin out and fully extend the rod. Block the cylinder sloping up a bit so there's less oil drainage to deal with. Clean everything up to reduce the chance of dirt getting in. Take out the retaining circlip. Loosen the hydraulic fitting to vent air as the rod assembly is pulled out. Bag the open end.

The o-ring should be replaced. Car-part/service places should have a match for it. Some would be able to straighten the rod. Good luck, Dick B.

 

[bigbenkubota]

... Turn out the retaining ring. ... Good luck, Dick B.

Is there a Kubota tool for removing this retaining ring? buy a off the shelf one? make your own? Two pins on a length of steel?

 

[rbargeron]

EDIT 10-17 2pm - According to a friend who has similar cylinders, the gland is held in by large internal circlip that fits a groove in the barrel. See other posts below for getting the circlip out. The window can be lengthened with an angle grinder to help get hold of the. On my friend's cylinders the circlip has two ends sticking out that can be squeezed together to release the gland.

With the pin still installed the bent rod could be putting side force into the gland, making it move hard. It will move easiest of fully extended with the pin removed.

 

[bigbenkubota]

So I had just a minute and tried turning the gland with this tool that I found (the rod wasn't fully extended or disconnected): http://www.armstrongtools.com/wrenches/spanner/armstrong-34-154-adjustable-face-spanner-wrench-3.html. I hit it with a dead blow hammer pretty good and couldn't get anything to budge.

What's the best way to get the retainer ring to move?
I tried tapping on the ring itself to get it to free up.
I tried rotating the gland both ways - being aluminum the holes are starting to wallow a little so I don't want to keep trying something that could make it worse.

I'll extend the rod all the way and try it again.
I could use the penetrating spray but I doubt it will reach very far.
How hard should this turn?

It appears there is (was) a little tang on the end of the retainer ring. Because of how thin and maybe a little rusty it was, it broke off. Will the retainer ring still rotate regardless of the condition of the tang? I assuming the rod itself does not need to rotate with the retainer ring (since its isn't disconnected it currently can't)?

 

[bigbenkubota]

Here's what it looks like now:

 

[G.rid]

I haven't come across a tang or keeper like that before, hopefully someone else can chime in on that part.

I have rebuilt a number of cylinder at work. The easiest way we get them to move is tapping around the outside of the cylinder itself, careful to not hit the edge and roll the threads over. This helps break up the rust between the threads. Sometimes heat is involved to get things moving. Once broken free, most will come out relatively easy.

A big difference is we have them drained and strapped to a cradle. Even though you haven't disconnected the lines, have you released the pressure off both sides of the cylinder? (Set down the boom, shut off the tractor, the wiggle the controls until that cylinder stops relaxing). If not, that would be a lot of force fighting you from moving the gland.

It's not much but I hope I helps.

 

[Yooper]

I just worked on this same type of cylinder on my stump grinder build. The arrow that I added to your picture points to a retainer ring that you 'roll' out of the cylinder. Start by taking a small punch and tap the exposed part of the retainer from the opposite side of the arrow. When you get enough of it started coming out, use a pair of vise grips to pull on the retainer while rotating the gland clockwise. It will roll right out. I included a picture of a cylinder disassembled (sorry about the bad quality) so you can see the groove in the gland that the retainer sit in.

Basically, you reverse the procedure for assembling. Just use some grease on the retainer to help it slide back in. Hope my explanation is clear enough to help. Good luck!

 

[D2Cat]

That piece sticking out is a piece of keyway stock with a hook on one end that is wrapped around the entire diameter.

You need to hook the end, or drive with a punch, or get a hold with a vice grips. It then works it's way around and out.

Patience is often a virtue in this project!

 

[bigbenkubota]

I believe I generally understand how the retainer ring works and more now with the last couple posts, but to really confirm this further:
So the gland rotates clockwise? Meaning that the square end of the retainer ring should go down into the cylinder as the rest of it comes out (that's actually the 'butt' end of the ring and as I described in a previous post I broke off the front)?
Is the ring and gland able to rotate separate from the rod?

I tried rotating it both ways and did actually tap on the end of the ring, but now with any sort of force.

The pressure should be off the cylinder, but its still upright. I'll lay it down on something and really let it relax and extend.

And I will tap on the outside.

Thanks for the help, i'll see what progress I can make with the current tools that I have. If I need to put more force on the gland then i'll have to buy the tool shown above.

 

[D2Cat]

The retainer has a hook that is usually about a 1/4" bend. You can usually get a hold if it and pull/drive it out. If the little hook is missing you may need to take a wire welder and tack a nubbin' on there to get something to work with. It does not matter which direction you use to get it out, but once again , the hook makes it come out only one way...you can't drive the hooked end through the slot.

After looking at you picture again, you may be able to clamp a vice grips on the nubbin and tap it with a hammer to get more material out. Then get a better bite to keep it coming around.