JD 48 Dipper cylinder: Back Hoe  -- Tractor Attachments Implements 3ph Discussion Forum and Review JD 48 Dipper cylinder: Back Hoe -- Tractor Attachments Implements 3ph Discussion Forum

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 04-25-2003, 04:31 Post: 53740
harvey



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 JD 48 Dipper cylinder

JD 48 bent dipper stick cylinder. Last Sat am put hoe on to dig a new burn pit. Working close to tractor with dipper stick. The dipper stick must have been real close to the stop. Went I started to lift the boom I heard a bang. Thought what to heck and realised I had pulled the dipper stick. Boom and Dipper stick levers on JD are backwards from Industry standard. Most of our big construction equipment, at work, the boom on right and dipper on left. I figured when I got the 48 that what little I'd use it I would not fuss over it and I would be careful. OH WELL!

Called Dealer Monday they overnighted new cylinder in and I removed old cylinder, swapped at dealer, and installed new one, NO CHARGE! Cazenovia Equipment, NY IS THE BEST!!!

New cyl is $585.00 to rebuild is $300.00+

One non JD mechanic suggested to swap hoses. I told him you can't do that because of Problems with relief valves and restrictors and anti cavatation ports. Was ganna just swap restrictors etc but a little orifice in the Boom body must be moved requiring the valve block assembly to be removed anyway. Talked it thru with JD service manager Rich and the cut mechanic Doug. Both felt just move/restack the valve bodys.

Pulled whole block out restacked the valves in the new order. Moved hoses to new locations. JD said the warranty will still stand.

The dipper cylinder still strokes just a little too far and requires the relieve valve to function, the cylinder still flexes quite a bit. Do Not know yet why the relief valve did not save the cylinder on Sat. But do believe the block on the dipper stick needs tweaking to let the cylinder stroke to its limit. Until I get it sorted out Dipper stays out away from tractor.

Any way I've said it many times: You might pay a little more at a dealer that provides excellent service up front. Cheapest purchase is not always the best. Cazenovia Equipment has taken excellent care of my needs for any work. The mechanics answer my questions and they offer good advice.

Harvey






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 04-25-2003, 08:57 Post: 53752
TomG

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 JD 48 Dipper cylinder

That sounds like a very good result. Certainly better than my thought of a dumb quick and dirty fix when I started reading the comment. I thought, maybe just putting a different knob on the dipper control valve lever would help keep them straight.

I don't know why the relief valve didn't protect the cylinder. I guess that implies that the circuit needs a relief pressure that's lower than the tractor's system relief pressure as well. the only thought I have about the newly stacked valves is that if the dipper control valve originally was the last in the series, there's a possibility that the power passage doesn't go through the valve. If such a valve was put in the middle of the stack, the later valves wouldn't have the simultaneous but lightest load moves first feature that's fairly common. That would be a pretty small issue for me and I might not notice whether I have the feature or not.






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 04-25-2003, 17:15 Post: 53773
harvey



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 JD 48 Dipper cylinder

Tom That was my concern why did'nt the pressure relief pick it up. My only thought there is: It was so close to the welded stop and the rpm was 1700 or so and the opening of the valve was just to much of a spike. I reread most of the old posts about the bent cylinders and looked things over from those and the only unprotected one is the bucket curl with a big rock or a solid stump in bucket me thinks there could be a problem.

JD folks were very concerned about using the hoe to move the machine. I am guilty of that. So I guess I really need to pay attention to those forces on this small stuff.

I believe I am going to grind the welded block so the cylinder can do a full stroke instead of the dipper hitting the welded stop.

The valving on the block is pretty straight forward 6 valves and 2 end caps I swapped 2 & 5.

I can not see any issues with the cylinder on the dipper stroking a full stroke. There appears to be plenty of bucket clearance.

Your thoughts on full stroke of cylinders. I know you know lots about hydraulics and your advice is appreciated. I do not read only what I need to too fix them. I should probably read more but...






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 04-26-2003, 06:36 Post: 53790
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Harvey: Apologies for the length of this but I just got to thinking--always a problem for me. There are stories around about inadequate heat-treating of some JD hoe cylinder rods. I can't recall which cylinders, models or years. I can't recall for sure but some people have had cylinders replaced for that reason.

I don't know if your cruise through the archives here and maybe elsewhere found discussions about heat-treating but maybe your Dealer could check if there were problems reported for your particular batch of rods. Anyway, the rod itself would a convenient explanation and I'd want to eliminate that possibility before doing anything else.

I can't visualize the welded block but I guess the question is whether the block, bucket or the internal cylinder stops take the load at full stroke. Guess I'm having vision problems this morning but the way I'm thinking is that load creates pressure and it shouldn't make a lot of difference to the rod where in the stroke high pressure occurs. Vectors may change as the dipper rotates but I can't imagine that hitting any designed stop should make much difference to loading on the rod--or at least the rod should be engineered for it. I would keep in mind that cylinders do have internal stops far as I know so the block may serve some other purpose and I'd be reluctant to remove it without careful thought.

There is one thing though. If something is against a stop then relief valves won't provide protection against load shocks. For example, if the tractor was jacked up on the stabilizers and the dipper was against a stop, then lowering the stabilizers or other weight shift would place the entire weight of the tractor rear on the dipper rod. Sounds like there may be a possible explanation there.

I don't know the JD hoe valve, but many valves have a relief in the inlet section. When used on most tractors there are two relief valves in the inlet line that should provide protection to any circuit where the control valve is open. Either one should be adequate unless the hoe valve is speced for a much lower pressure than the tractor valve. Many valves have circuit reliefs but they generally are intended to provide protection against load shocks when the control valve is closed. I suppose circuit relief pressures could be set at any pressure, but most are set well over system relief pressures. You'd expect a hoe would be designed to accept loads up to circuit relief pressures. So I guess a question is whether the circuit relief was working.






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 04-26-2003, 19:59 Post: 53820
harvey



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Tom I've gone through it fairly well. The block prevents the dipper stick from getting to close to the boom. I'd like to grind some off the block but bucket curl would hit boom then. When I bring the dipper into the block now the cylinder will flex some (more than I'd like) but the circuit relief will pick it up. Works that way it the shop anyways. Would guess it could bend again if close to block at 1700-1800 rpm, where I operate at, and the valve is opened. Maybe it was just a fluke... who knows at this point...

It's, the valving, is where it's gonna stay. Had it out this afternoon to stress it on some pine stumps 25+inches 60 or so cm Smile. I am happy with it. I forget it's not a big machine and tend to try and push it a little harder than I should.

I am a little gun shy yet. Still remember backwards JD system to standard systems. Have a little JD ingrained memory yet in the fingers yet or so it appears.

Seems strange to have that. On Caterpillar never even a consious thought about controls.

Anyways the hoe working good. On to the new wood shed project...

Thanks for youe advice and comments. Harvey






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 04-27-2003, 07:16 Post: 53836
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I did a little more thinking later in the day. If the dipper was against the block or cylinder stop and the dipper was on the tractor side of vertical with respect to the boom then there'd be no place for the dipper rod to move if weight came down on it. The circuit relief wouldn't provide protection and it wouldn't make any difference if the control valve was open or closed. However, the boom or bucket circuit reliefs might provide protection if the geometry was such that they'd develop enough pressure to open.

I'd guess the design would depend on the boom reliefs for protection under those circumstances. Just the same, I'd likely avoid having the bucket on a hard trench floor when the dipper is fully back. Good that everything's back to work now and I hope the tractor's working harder than you are.






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 07-15-2003, 20:36 Post: 59572
andyw
2003-07-15 00:00:00
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 JD 48 Dipper cylinder

Hi,

I just went through two cylinder rods on the bucket cylinder on my 48 backhoe which is just over two and a half years old. I was removing tree stumps in a 4 yo 8" dia. range. The first rod bent like a pretzel. I had to cut the shaft with a hack saw and destroyed the nut trying to remove it. I was quite suprized to see an indent in the rod from where it had jammed against the nut. I replaced the rod and nut and proceeded to remove more stumps. At stump number five the rod bent again. Now I am really pissed off. My dealer told me that JD would not warrant the first rod and that I had abused the back hoe. This back hoe has approx. 15 hours of use. I decided to call JD customer support and had a discussion with the Canadian service manager reguarding my problems. He stated that there is no problem with my aplication and this should not have occured. Now if you remeber earlier I said I cut the shaft off with a hacksaw. The material that the shaft is made from is very soft and appears to be Supperior Shafting. I purchased a length of hard chrome shaft and made up my own shaft. You will not cut this shaft with a hack saw. I feel this will solve the problem. I did this because I felt that replacing the shaft with a third JD part would end up with the same result. I was of the understanding that all cylinder shafts where made from hard chrome shaft. It does not appear to be the case with the JD 48 back hoe. I am still waiting to see if JD will do anything to back there product.






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 07-16-2003, 07:38 Post: 59585
TomG

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 JD 48 Dipper cylinder

There are some stories around that maybe shafts used on some JD hoes were overly soft. Whether it was factory specs for the parts or a faulty batch I don't know. I thought I heard that the problem was fixed and some people had received replacements. Maybe you'll be in luck but my recollection could be wrong.

You're probably aware that the harder shafts will make it possible to place greater stress elsewhere on the hoe and tractor. I hope there are decent safety factors engineered somewhere. I also hope the shafts aren't so hard that they might break rather than bend.






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 07-17-2003, 03:11 Post: 59653
harvey



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Morning there are a couple of other posts about the bucket curl shafts. Breifly there is no pressure reliefs in that circut. If you have a stump in the bucket and curl it to much to hold it while you move it you are gonna bend or break something. The shaft makes a full stroke so there is no need for mechanical stops or pressure releif.

That part of the system is a concern for me also. I am VERY careful when I pull up a BFR (big fine rock) which would have no allowance for error. Me thinks a good size stump would do the same thing if I held the valve open curling it to long. I'd bend a shaft.

This thread reminds me I need to get to work at a hyd supplier to locate the parts I need for replacements and spares so I have one or two on the shelf late Sat night or early Sun am when most of my stuff happens.






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 07-17-2003, 04:03 Post: 59658
jeff r



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Harvey,

I would seriously get a hydro gauge made up and check that relief pressure. Even if the shaft was of low hardness or tensile strength, your relief valve should have saved you. Never a day goes by that some operater is begging my Tech Rep brother to increase the relief pressure of the Big Kamatsus, Cat/ or JCBs. Bad things happen with too much or no relief valves are working properly. A relief valve is put there for a reason and it seems yours failed. I will bet your relief pressure should be set at somewhere between 1800 to 2200 depending on specs. If that pressure was set properly and the shaft still bent then we can blame it on the shaft hardness or tensile strength.






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Discussion Boards > Active Subjects > Messages as Posted > Back Hoe Forum

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