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JD 48 Dipper cylinder

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harvey
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2003-04-25          53740

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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TomG
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2003-04-25          53752

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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harvey
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2003-04-25          53773

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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TomG
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2003-04-26          53790

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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harvey
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2003-04-26          53820

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 :-). 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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TomG
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2003-04-27          53836

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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andyw
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2003-07-15          59572

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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TomG
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2003-07-16          59585

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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harvey
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2003-07-17          59653

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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jeff r
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2003-07-17          59658

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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TomG
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2003-07-17          59668

G'morning Harvey. I don't disagree with anything you said. I do wonder if you were referring to a particular valve or valves in general. I think it's pretty common for valve assemblies to have relief valves on the cylinder circuits, although often they are intended to provide protection against load shocks when the valve is in neutral and they are set for over 3,000 lbs. pressure. I don't know whether it's common for valves used on hoes to have circuit reliefs, or cylinder stops for that matter but many valve assemblies have them,. Sounds like you may know some specifics.

I'm not sure if the discussion is about when a valve is open or closed but I think there'd be large differences between the two states. When a valve is operated the cylinder would see the any relief valve in the valve inlet section and probably the tractor relief valve as well. You'd think something would be engineered so the machine wouldn't be likely to bend or break anything at any bucket angle at speced relief pressures when the valve is active. Well, maybe not. I'd guess that much greater stresses would be possible if the valve were closed and the cylinder were working against a load shock relief or no relief at all (Well, I guess the hose could be thought of as a relief). Design might not be adequate if for example a bucket were resting against something solid and the stabilizers came down.
....

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Murf
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2003-07-17          59671

Harvey, I beg to differ but there HAS to be a pressure relief valve in the system somewhere. Without one the system would only last a few seconds (if that long) before it ruptured from excess pressure. The pressure relief valve is internal to a CUT and is usually the very first thing the fluid gets to after leaving the pump.

That's not to say it isn't set to high for this particular application though.

Best of luck. ....

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harvey
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2003-07-17          59715

I'll stand by my statement. There is no seperate pressure relief in the bucket curl circuit. You are right Murf there is a main pressure relief valve for the entire block. The Dipper stick and the boom also have a seperate set of relief circuits because they come up againt hard stops. The bucket curl can and does stroke to the limit of the cylinder. The other 2 can not because of the hard stops.

That is why you need to be very careful when you have a bucket curling onto something solid.

I have the valving sechmatics with the valve arangements and the reliefs for the boom and dipper circuits.

I think I said before I have had the whole block out to restack the valves with the proper reliefs to agree with the heavy construction industry arrangement.

When I have a few minutes I'll track down the specific site at JD for the valving and relief and circuit reliefs and post it. (I may have to do something else to post the circuits because to get to it you have to be registered with JD to use that area.)

I am still not pleased with the hard stops but I have not had time to play with the big cat's at work and look at their specific strokes. I'll try and keep ya-all posted.

Havin fun in the BIG sandbox and they give me money to do it!!!
Harvey ....

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jeff r
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2003-07-17          59718

I checked mine and just as I thought there is a relief valve for the ENTIRE valve block for ALL cylinders. For these sizes of backhoe entended for CUT tractors I would venture to guess there is no separate relief valve dedicated to any particular cylinder, but somebody can correct me if I'm wrong. Adding a separate relief valve to protect a given cylinder sounds like something that will cost some BIg $$$$s. Tell me I'm wrong??? On a second look there appears to be some kind of a plug atop the valves for the boom and swing cylinders but if they are relief valves and I would bet they aren't they are no type of adjustable relief valves I have seen nor are they anywhere like the main relief valve that protects the whole block. Check out picture #10 for how my backhoe valve block is configured. ....

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TomG
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2003-07-18          59730

When a valve is in neutral oil is trapped in the cylinder and lines. Hitting a bump when carrying a heavy load will cause large shock loads on the trapped oil. That's the purpose of circuit reliefs (sometimes called safety valves). As far as I know virtually all 3ph's have a safety valve and they also are desirable for many applications such as loaders. Most valves also have lift checks that prevent back-flow that would allow a load to drop a short distance when a valve is opened until the pressure from the pump increased. The main relief would provide protection when a valve is open. I haven't cross my eyes enough looking at schematic diagrams to know which side of the load checks a main valve relief would be on. If they were on the pump side then the main relief in many cases would duplicate the tractor's relief valve.

Having though through this a bit, I guess I can see that a circuit relief on a hoe bucket may not be too important if reliefs are used on the boom and stick circuits. Shock loads on the bucket should also load the stick and boom circuits so maybe these reliefs also protect the bucket circuit. If Harvey says there isn't on one his JD valve, I've got to believe that's true. I don't think I'd want to have the latch plate locked with the bucket pointed down and then back into anything though. Well, I can't imagine myself doing something like that so maybe it's reasonable if a design doesn't cover the possibility.
....

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Murf
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2003-07-18          59743

Jeff, those plugs on top of certain circuit valves are probably covers over the refief valves. The easiest way to check is to look at the hydraulic lines to the valve, a valve with a relief valve will have a third hose to return oil to the reservoir after the valve opens.

As for adding a relief valve, it is pretty straight forward. As for cost it should be less than $100 to add a relief valve to any circuit. It shouldn't take more than a few hours even if you've never done it before.

Best of luck. ....

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Murf
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2003-07-18          59744

Harv, sorry I misunderstood when you said "Breifly there is no pressure reliefs in that circut.".

The main relief valve certainly IS part of that circuit.

I now understand that you meant to say "seperate" pressure relief circuit.

I would think that $100 is a lot less than fixing or replacing a cylinder a few times.

Best of luck. ....

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jeff r
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2003-07-18          59777

Murf,

Assuming those are relief valves, is it normal they would put them on the boom and swing cylinders and not the dipper or bucket curl cylinders?????? I will check it out for the return lines like you said and ask my brother. If they are relief valves they sure don't look adjustable like the main relief valve. ....

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harvey
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2003-07-18          59778

John Deere specifically calls them "Dipperstick circuit Relief valve" and Boom circuit relief valve". These 2 circuits also have an anti-cavitation valve.

Both relief valves are addustable with shims.

If you look at your 47 0r 48 block you will see on the second to left (dipperstick) the relief (looks like a big nut) on top and 2nd from right (boom) the relief is on the bottom. (If you haven't changed them around like me)

These two cylinders need the protection because they come against a hard stop before they reach their full extended stroke.

The bucket curl makes a full stroke both directions there for does not need one. The problem is curling the bucket around something with no give that would act like a hard stop and the cylinder rod is probably ganna get bent.

I have no idea if you changed the main pressure reliefs to a much lower setting if it would save the bend or not.

On the JD blocks you could add the relief valve to the bucket curl circuit very easy and I am sure it would not be expensive.

Parts are: poppet spring, cartridge, o-ring,poppet, shim/s,spring, plug. You would have to pressure test the circuit and add or remove shims for the relief pressure you want.

JD specs state 48 has the Main system relief valve set at 2400-2550 psi, the 47 is 2100-2250.

I will have to figure out a way to post JD's theory of operation which explains Control valves, load check valves, main system relief valve, circuit relief and anticavitation check valves and the restrictors. Of course I'd probably get shut out at JD's maint site.

My little episode with this issue has a lot of research and picking the JD mechanics brain before I switched it all around to suit me.

Tom knows hydraulics well me thinks he talks "Tom" and I talk "Harv" both saw the same thing only one is ONTARIOAN launguage and the other??? who can figure out harv talk...

Murf my dopy fingurrers never put on the puter what my brain is working on...

Dumb fiungurers....
....

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TomG
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2003-07-19          59799

I'm still trying to get my mind around a couple of things. The first is full stroke. I imagine full stroke is where movement is stopped by cylinder stops before the limits of movement in the pivot point are reached. If that's the distinction, I can't quite understand why one would need a circuit relief and the other wouldn't.

The other is hard stops. I don't know if that's a mechanical limitation to movement as opposed to the hydraulically cushioned stops that are a feature on some cylinders. Cylinders that can't move to almost full stroke may not have cushioned stops even if the cylinders had the feature.

I can't find a schematic drawing of an entire valve assembly in my collection so I don't know how a main relief is plumbed or how one may work with a load check valve. I believe that the way a load check works is that if a sudden load increase happened while digging (a rock shifts or something) the cylinder pressure may increase higher than pressure supplied by the pump in which case the load check would close to prevent back-flow. Circuit relief would provide protection but I don't know if the main relief would operate in this case or even if a main relief just duplicates the tractor's system relief valve.

I may be confusing issues by trying to make a distinction between pressures that are developed by the pump working against a load and by pressures loads create on trapped oil (oil that's isolated from the pump).
....

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jeff r
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2003-07-19          59806

Tomg,

Here is way I'm looking at it. A full stroke is when a hydro cylinder ram goes ALL the way out. FULL STROKE...if it is a 24inch stroke the ram has extended 24 inches out of the cylinder REGARDLESS of what is is pushing. When the piston/ram has come to the end of the cylinder it stops, pressure rises ,and relief valve opens. Hydraulic cylinders ALWAYS push or pull in a straight line/ linear direction just like the pistons of your car. Any other less than full stroke is when whatever the ram is connected to has come to the end of travel WITHOUT the Ramshaft of the cylinder coming to the end of the stroke. Is this what we are talking ABOUT GUYS????? ....

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TomG
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2003-07-20          59831

Well, I'm probably guilty of being obscure. The subject is why a JD hoe valve would have circuit reliefs on the boom and stick circuits but not on the bucket circuit. I can theorize about several reasons why one may be unnecessary and I'm just curious what the actual reason might be. ....

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harvey
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2003-07-20          59833

Mornin Tom

Me thinks the reason is: the bucket curl cylinder can stroke the full lenght of the piston and only forced to stop at the ends of the cylinder.

The dipper stick and the boom have hard stops, mechanical, build in limits that stop the dipper or boom before the cylinder reaches its full stroke.

I think (if I remember my measurements) the dipper has 3/4-1 inch of travel left in its stroke when it hits the stop welded to the frame. The bucket teeth lack 6" of touching any thing on the boom. So that is why way back when I was talking about grinding some material of the stop.

Some where along the line we'll get a common language here.

The simplest way for me to think about it is: wood splitters. I have seen several bent hyd rods in that application. Usually all are bent just before the end of the full stroke is reached. Just seems like all of the rod is hanging out with nothing to support it and that is where its gonna bend when something has to give and that big notty maple block won't.

....

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TomG
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2003-07-20          59836


Yes, I think that's a pretty good bet. There'd be lot of rod that can flex, and there's probably only one point in the travel where all force would line up absolutely square with the cylinder. Ah, the temptations of language. I almost wrote 'vector,' which is probably an easier way to describe it. But then, I have a statistician's grasp of vectors rather than an engineer's so maybe not. Besides, I'm also an educated hick. Proud enough of my family origins but my language does end up obscure no matter where I am. Trained in probability and statistics too. I've made obscurity into an art form.

If the length of rod plus a vector (oops!) near the end of travel is the problem, a relief valve in the circuit probably wouldn't help. The pressure may have to be so low to provide complete protection that the circuit might not have good digging power. The best solution probably is that skilled operators should help the engineers by recognizing that some things should be avoided. There does seem to be a bunch of 'don't do this' warnings for hoes.



....

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harvey
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2003-07-20          59839

The engineers could build them to Gov't spec's "NIN-COM-POOP-PROOF" with 4" cylinders and 2" shafts. Of course the building of doubley or trippley extra strong would add considerable cost and weight and still someone would still be able to break it or bend it...

Been there seen that...

....

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DRankin
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2003-07-20          59845

When I was building and servicing artificial kidney machines we tried to achieve a standard we called "nurse proof".

We never got close. ....

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TomG
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2003-07-21          59879

I remember the MIL-SPECS mostly because the prices tend to be many times higher then pretty much the same thing from a hardware store.

When I was in the Air Force some buddies worked on B47 ECM equipment. When a particular electron tube in the equipment went bad at least six were ordered because most of the MIL-SPEC ones didn't work in the circuit. The logistics system would project huge world wide consumption and purchase even more of the things. They must have had warehouses full of the things. I heard that a few people started going the drug store (they had TV tube testers back then) and buying some because the drug store ones worked where as the MIL-SPEC ones didn't. The AF couldn't get its logistics system to work either. It'd regularly make ridiculous consumption projections and then stuff would be warehoused for a decade and then go to surplus. I used to receive tube that were manufactured 15 years before I got them.

My buddies cleaned and polished the very last flying 47 and a crew flew it off to the AF museum. Maybe it still has a drug store tube in it nearly 40 years later.
....

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BrentB
Join Date: Jul 2003
Posts: 21 Illinois
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2003-07-21          59920

The reason the bucket cylinder does not have a line relief
is that it is designed to have the highest breakout force.
In other words, when you can no longer pull in the stick
or raise the boom, the operator should still be able to
curl the bucket to finish the load. This action may introduce higher than system pressure loads in the
boom or stick, which is why they need line reliefs.

Another interesting design trick is that when flow
is shared between circuits, the boom lift gets priority.

Last comment, I'm told you should never hammer with the
bucket fully curled because the cyl is fully extended, and
the impact loads through the bucket links can pull the
cylinder apart. ....

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TomG
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2003-07-22          59926

Brent: Thanks for the comment. It seems to tie both the relief valve and the bent rod questions together and also indicates that everybody's thinking was in the right direction. When the bucket is operated, it shouldn't need a relief since the main relief would provide protection and when it isn't operated either the boom or stick relief provides protection.

Not withstanding my earlier comment about the latch plate locking the sticking and boom reliefs out, I guess the idea works the other way as well. If either the boom or stick is operated the pressure in a cylinder that does have a relief is always going to be higher than in the bucket circuit so the bucket circuit is still protected. Clever, those designers.

You don't happen to know if the 'boom has priory' trick is a particular design or whether it just the way a tandem connection 'lightest load moves first' happens to work out? I believe that most modern valve assemblies have an internal passage that produces a tandem connection when several valves are operated simultaneously. I don't know if there is a special design used on hoe valves to guarantee boom priority.

I think I've seen the priority switch back and forth on my hoe, which sounds like a tandem hookup so maybe it doesn't have a priority feature. I can't recall exactly since I now pull just one valve at a time. I decided I'd rather make the choice of what moves rather than letting the hoe decide but who knows, maybe after some hours pulling valves maybe the hoe would make better choices.
....

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BrentB
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2003-07-23          60004

The boom gets priority on Caterpillar excavators because I think the boom takes more oil flow (and hence time) to get out of the trench. Better to have your stick stop extending
than the boom stop lifting for cycle time efficiencies.

Excavator hydraulics are pretty elaborate since they include
clever oil recirculation loops and anti-drop valves as well.

I guess I don't know for sure that a backhoe boom would get priority, but I think the first valve stack in a pressure beyond system would get dibs on the flow.

Brent ....

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jeff r
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2003-07-23          60008

Brent,

I will have the correct answer for you tommorrow. My brother is the head troubleshooting honcho for the largest construction equipment dealer/leaser in Michigan. He will know instantly and by ALL major brands. I will ask about CAT specifically and then the rest. ....

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TomG
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2003-07-24          60016

Yes, lifting full buckets out of a trench is what takes me the most time, and boom swings are a close second. Anything that helps speed would be good.

I think it takes some tricky hydraulics to get true simultaneous operations with differing loads from a single pump. The basic connection is in tandem where several cylinders receive pressure but the lightest load moves first. I'm always interested tricky hydraulics and any descriptions are appreciated.

I've heard that heavy equipment sometimes use more than one pump to run a hoe (especially to run the swing cylinders). I guess that's a different approach than fancy hydraulics. Genuine simultaneous operation of the swing plus either stick of curl circuits would sure save a bunch of time.

In a valve assembly without an internal passage sometimes called a 'power passage' operation of the first control valve in a stack cuts of flow from downstream valves. A separate downstream valve assembly may be operated by cylinder exhaust oil from the upstream assembly unless the upstream valve has a separate TANK return line to the reservoir for the cylinder exhaust oil. ....

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Murf
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2003-07-24          60017

Tom, it's not so much tricky hydraulics as it is a matter of flow rates. Full-size excavators have staggering pump capacities.

The Caterpillar 345 for instance, which is still considered a 'medium size' unit and has a pump output of 95 gpm at 5,000 psi. In fact the 'pilot circuit' which is the seperate hydraulic system strictly to activate the main 'working' system produces an additional 10.8 gpm, but at only 675 psi.

If your little Ford could produce only 10% of those rates you would find a HUGE increase in operating speed. In fact people I have spoken to who upgraded to a pto-drive hydraulic pump have noticed dramatic increases in performance.

Best of luck. ....

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Misenplace
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2003-07-24          60081

Mark H, if you ever do achieve that proof rateing would you kindly let us know ? lol. ....

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TomG
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2003-07-25          60095

Murf: My comment about speed was incidental. I was more interested in hearing some about the more elabourate techniques that aren't likely to be available on our basic tractor hoes. However, I think we've done pretty well with the relief valve and bent rod questions so maybe the subject needs a rest.

It would be handy if I could extend the stick while swinging the boom when dumping though.
....

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