Over engineered........

Not sure of over engineered is exactly the right term for what I'm talking about but it's a good start.

I've seen it before on other machines, but in this case the culprit is the bucket cylinder on a newer 120 JD excavator. Getting it taken apart this morning, with the intentions of repacking it, was a breeze since the head was simply bolted on with a handful of socket head capscrews. Unfortunately once apart my plan got brought to a screaching halt when it came time to remove the nut holding the piston on the rod.

The first thing to overcome was to get a setscrew out that was holding a ball bearing tight in a locking groove. Not only was the set screw TIGHT, they had also punched/staked the top of the hole in two places so that had to be ground out before the set screw would even move. Once that was out of the way it was time to take the nut loose. I started with my one inch drive IR impact. With my compressor putting out 75 CFM at 150 psi the impact will always perform to it's rated potentialand then some. When that didn't work I broke out my 1" drive Swench which is rated at 2000 ft lbs. I spent about 10 minutes working with that and still got nowhere. So, I placed a call to my local JD dealer. Talking to the service guy I find that the nut in that cylinder is torqued to just over 2900 ft lbs. Since the first cylinder bench I built for Dad's business is basically tied up in my parents divorce proceedings, I got to spend the evening starting on another one. When done it will be alot simpler than the other one, and I hope more user friendly as a result, while still working like I need it to.

That said, I got to ask you, WHY is there any need to torque the nut that tight in this situation. I mean they made cylinders for YEARS, with hex nuts and thread's larger than this one and didn't tighten the nut that tight. Instead they used a bit of common sense and used a lock nut, and/or a mechanical lock of some type, and often even a bit of Locktite, and the nuts have stayed on for years just fine.

Over the years I've talked to alot of other mechanics and to this day I only know of one time when a rod nut backed off in a cylinder. In that case a truck mounted crane popped the lift cylinder's rod out of the barrel, forcing the boom to knucle over backwards, tear loose at the boom pivot pins, and crush the cab of the truck. Now that was a heck of a mess, and it should not have happened, but it did....but that's another story all together.

In the end I guess what I should say is that when properly assembled, (ie not reusing certain types of lock nuts, staking threads, or using Loctite when needed, etc, etc) the thing isn't gonna come apart, so there is no need to tighten a nut to 2900 ft lbs, in a situation like this...ESPECIALLY when also using a mechnical locking device that wouldn't allow the nut to back off even it it was left loose.

I guess my point with this whole mess is the extent of over engineering put into way too many products nowdays. Granted in years past there have always been special tools needed to work on many products, and I think that will always be the case. Unfortunately, more than likely, it'll only get even worse than it is now. Thing is though, in years past, even the large Mfg's like CAT often had diagrams in the service manual telling you how to make the needed tool, or the tool was readily available at a fair price. Nowdays they add onto the whole 'special tool' mess by doing things like tightening nuts so damm tight you have to have a cylinder bench to take them apart...and then to make matters worse they come up with some off the wall design for a part (((ie the shape of the rod nut)), or do something else that's just plain odd that no "normal" tool can do anything with. Once they have you by the 'short and curlies, then the special tool is either treated like a 'trade secret', or if available for purchase winds up costing as much as the machine it's needed to work on. That just ain't right............

Like I said I know there have always been things that have been a PITA when working on equipment, but oh how I long for days gone by when the 'special tool' was nothing but a wrench with an odd shaped handle, when parts books actually contained the words, " obtain locally", and when EVERYTHING (including the headlights) didn't need a computer telling it what to do...............Now those were the days.........

The way I see it, a company employs X number of engineers. They do a good job, make a good product, now they all go away and look for work? Nah, they are just going to keep changing things to justify a paycheck, and then when all the things that needed improving are all working well, they will start changing things that don`t really need changing. Gotta love it.

Yep, I think they started making changes just to justify their jobs a long time ago. Heck I've read articles talking about how they are taking this 4 piece mechanical design and adding 10 more parts and making it electronic in an attempt to "simplyfy" the part.......... That particular article was in a trade magazine I get aimed mainly at engineers. Funny, they are constantly complaining about not getting paid enough, not getting the credit they deserve for this or that, etc, etc, etc. Never a word about those of us out here that have to deal with the over complicated crap they are spewing on the market nowdays......

A simple task like rotating tires has now become a task for a specialist with a tire pressure monitoring system reprogramming tool thanks to our wonderful bunch of polecats in DC.

The old black smiths who used to make horse shoes and wagon wheels. They complained bitterly about the complicated Model T.
Engineers are subject to the cost cutting accountants and the legal department worried about liability. Sometimes the result is some convoluted designs.

I'm a drafter/designer who has worked with engineers for years and also designed my own fair share of parts...I'd say it's the liability issue. Overengineer something and you won't have to worry about it failing. Which in a lot of ways is good (safety and reliability), but it can also make maintenance a nightmare (as you've found) and drive up costs.

A former company I worked at designed (amongst other things) I-beam constructed baseplates ('skids'). A long time ago, an engineer had written a design guide (rulebook) for these skids such that the skids always were overengineered, and were much stronger than they needed to be. The main reason was so that dumb drafters like me could, by using the design guide, design a skid without an engineer having to approve it. It was mostly for lifting of the skids, so that there was a 4x safety factor. Hiring 10 drafters was a lot cheaper than hiring 10 engineers to design the same thing, even if you used more material.

Amen!

WOW 2900 ft lbs. ! The only thing I have to remove something like that is a flame wrench.

The attitude in business today is, make as much money as you can, wherever you can. Can't say as I can blame businesses that much, because margins these days are slim, and the government has their hand in their pockets at every step.

In the good ole days, the special tools were a "fair" price because the company was selling them at a loss as a good will service to their customers.

Then the bean counters took over, and decided that good will was dead. If you're going to waste time and resources on these tools, you may as well make it worth your while, and turn them into a profit center.

I worked in a hydraulic cylinder rebuild shop for several years, so I can empathize with your predicament. If the rod is not bent, nicked,gauged, chrome peeling off, etc. why don't you try repacking the piston on the rod? (Assuming you can work the packing over the eye end of the rod.)

I've seen a few excavators with the nut come off inside the cylinder. takes guys a while to figure out whats wrong if they aren't sharp.

My guess is they wouldn't have put some much effort into that nut if they hadn't had problems with it.

Next will be the over-unity machines harvesting the energy from a magnetic field. (E=MC2) FYI Joe has closed the loop. His machine is self running. He has a generator connected that puts more back in the batteries than it takes to run the machine. Perpetual motion at last.

(quoted from post at 08:50:27 02/22/12) Next will be the over-unity machines harvesting the energy from a magnetic field. (E=MC2) FYI Joe has closed the loop. His machine is self running. He has a generator connected that puts more back in the batteries than it takes to run the machine. Perpetual motion at last.

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And all the Tigercat logging equipment I operate and fix puts more fuel back in tank than they burn. I will get more return on my investment with logging equipment than you ever will with your crackpot machine.

That ruined my day. :evil: I'm gonna go kill more trees now. :twisted:

You missed the other point, if it's to darn hard to fix you'll by a new one from them, take it to them to fix or trade it. They'll fix the old one with all their special tools and resell at a profit OR break it for parts. Planned obsolescence has been a big part of the equipment and automotive industry. GM started it, tried to convince people the new car was better than the one you had OR that you needed to trade up to more expensive model. Implement dealers used two tactics to get you to trade, bigger is better and the new ones are bigger, so you can do more in less time, only thing was you had to do much more to make the same money. They also used "features" like live power, improved hydraulics, better operator interface, quieter cab, better heating/cooling, better visibility, better easier shifting, front wheel assist, and so it goes on.

As a mechanical engineer I'm going to throw this out there for comment....

The days of the farm grown engineer (with or without degree) are a thing of the past. We very rarely get any new engineers with any practical sense, and in my opinion engineering school are stressing the wrong things. Too much time is spent on computers including FEA and not enough time on how to make things; both physical manufacturing, ease of assembly/maintenance, and functionality.

It's possible that with that size nut and tension in the rod that is what the torque actually calculates to. Doubtful though.

But as stated above, I'd rather have it be a PITA to take off than have it come apart when I didn't want it to.

I'm going to post a poem I've got framed on my wall for your enjoyment since I think it pertains.

And remember, its more often the bean counters fault than the engineers....

The Successful Designer

The designer bent across his board
wonderful things in his head were stored
and he said as he rubbed his throbbing bean
how can I make this hard to machine

If this part were only straight,
I'm sure it would work first rate,
But 'T would be so easy to turn and bore
It would never make the machinist sore.

I'd better put in a right angle there
Then I'll watch those babies tear their hair
Now I'll put the holes that hold the cap
Way down there where they're hard to tap

Now this piece wont work, I'll bet a buck,
For it cant be held in a shoe or chuck;
It cant be drilled or it cant be ground
In fact this design is exceedingly sound.

He looked again and cried, "At last--
Success is mine, It can't even be cast"

Author Unknown

The rod is in great shape, the rod seals have just started seeping to the point they will leave a stain when parked. Thing is the guy needs them fixed since he operates in alot of hard surface areas like parking lots, and on alot of residential properties where grass has already been planted. Unfortunately the only way to change the seals is to remove the piston to get the head off. Funny the piston seals is still in great shape and is giving absolutely no trouble at all, as has been the case in 95% of the other cylinders I've built on equipment in the 20 year old or newer range. Rememeber when they used V packing on the rods and if you had a leak all you had to do was remove a few shims to tighten it up or, worst case, remove the old stuff and cut the new stuff diagonally and put it in with the cuts staggered like a set of piston rings? I've seen machines with the V packing that gets run everyday and they seem to get better life out of them than any of the new stuff. Again, those were the days.

My auto mechanics teacher in high school had a saying. "Engineers always work in pairs. One of them comes up with some dumb a$$ idea...and the other finds some place to put it where it can't be worked on..."

I think your right, there is too much emphasis put on what I call engineering for the same of engineering. By that I mean the time spent desiging stuff so something looks 'pretty' with no regard as to how that extra little 'pretty' piece will effect being able to maintain the item. Too, I read an article in machine Design recently talking about designing with the idea in mind that the part was going to have to be machined, cast, etc, and how many new engineers have only the slightest idea what a milling machine or lathe is, how a mold has to be made, etc, etc. Basically it goes right along with the jist of your poem, it looks good on paper so it has top work..........

Funny story, the guys at the RR repair facility once had an engineer tell them that the piece of material in the shop WOULD FIT IN THE HOLE HE HAD DESIGNED IT TO FIT IN. Thing is the piece of material he wanted to fit in the hole was 3/4 thick, but the hole was only 1/2 inch thick. Still he swore up and down it would fit together because it it said so on his computer screen....until they made him walk back in the shop and take a first hand look at things....

Personally I think when they used slide rules the guys doing the designing spent more time really concentrating on what they were doing and put alot more thougt into it. They figured there was a degree of error in everything they did and allowed for it. Nowdays when the computer says you'll need .002 clearance to remove a part that's all that you get. Thing is they fail to take into account that the parts around it have a tolerance of +/- .004. So if one of those parts is at it's max on the plus side then the part that needs to be removed now want come out because of a .002 clearance issue. Right or wrong I don't know but having worked on both the old stuff and the new stuff I have more clearance issues on stuff 20 years old and newer than I have ever had on the older stuff.

You need that much torque so as to not pound the nut loose when some fool operator is rapping out his bucket. It is all a matter of inertia and how fast you want to stop it.

Think 2900 ft-lbs is too much? Try the nut on an EX5500 arm cylinder....over 55,000 ft-lbs.

I am a Hitachi Service Rep and the Deere 120 (designed by Hitachi)is either an EX120-5 or if newer, a Zaxis 120

I agree to a point (seeing both sides)

A lot of engineers only get to work on one small aspect of a system not seeing the whole picture e.g. one person designing the engine and one the engine compartment. They often have envelope dimensions but not the actual parts/models.

This sometimes explains why some things are a bear to work on anymore. Also since maintenance procedures often aren't written till after a product is designed/built they include things like "pull engine to access #8 spark plug"

I'm not condoning this, just stating facts/opinions.

As far as your fit example I call it CADD cancer, and hate it. Just because a computer program defaults to four decimal places .0001" does not mean it needs to be that exact. There is a fine art to understanding fit and finish....

If a saw cut will do why machine and grind to a tenthousanths of an inch.... why because the drawing said 4.3125. That's why to this day I use fractional dimensions where ever possible. It shows the machine shop that it's just not that critical. But I too have made some boneheaded 3/4" pin 1/2" hole mistakes... It happens, but I'll be the first to admit fault and let everybody have a good laugh.

I had an intern once say something that I'm still quoting.

He said "Boy it sure does get expensive when you put it in steel.

He hit the nail on the head... paper's cheap... it gets expensive when you put it in steel!

Must be one heck of a big rod end and nut to take 2900 lb-ft! What do you hold the rod down with to apply that ammount of torque?

55,000 or 5500? I've seen hydraulic torque wrenches used to tighten 3 3/4" flange nuts on 36" pig traps for the Trans-Canada pipeline. There was 24 bolts on the flange and the flanges were about 5" thick! It took 500 ft. lbs to tighten them enough so they wouldn't leak during hydrostatic testing. Before they got the hyd. wrenches they did it by hand with about 12 ft. snipe. 55,000 ft. lbs. seems awfully high?

They also used "features" like live power, improved hydraulics, better operator interface, quieter cab, better heating/cooling, better visibility, better easier shifting, front wheel assist, and so it goes on.

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Wow. We've had all this advanced technology for hundreds of years? You mean we could've been farming with 425HP rubber-tracked Steigers in the 1940's? They held this technology back as a part of planned obsolescence?

Who are "they" anyway?

OK, sorry if I oversimplified things. We didn't get very many JD cylinders, like the one your describe, in the shop. when we did, we usually couldn't remove the screw either. In that case what we did is 1) make a new rod (we were a fully equipped machine shop), or 2) cut the piston off the rod (with the customers permission) and subsequently machine a new end on the rod. A few inches of travel would be lost, but it was usually no problem. Where are you located in NC? If within reasonable driving distance of Pittsboro, why don't you bring the rod/piston in the shop (Atlantic Hydraulics LLC) and let them advise.