March 10, 2009 

'Inside Hydraulics' Newsletter

1. How do they answer this question?
2. Straight talk about bent cylinder rods
3. Why hydraulic oil is different
4. Content for your web site or e-zine
5. Help us spread the word
6. Tell us what you think


How do they answer this question?

Not everyone digs Brendan Casey. And frankly, I'm OK with that. You may not always agree with me, but at least you're never left in doubt where I stand. I'd be a terrible failure as a politician.

Mixed in with the occasional barb I receive, is a lot of feedback from members that do 'get' where I'm coming from. I got one such letter last week from David Schreier, the gist of which is worthy of comment here:

"I am the owner/operator of a small business that uses a skid-steer loader and a medium size tractor to do landscape type work. I have worked with, around and on heavy equipment for over fifteen years. In all that time, I have been stymied by my lack of knowledge about the hydraulic systems and how to do proper servicing of them...

Then I found out about Mr. Casey's work on the internet almost by accident. I soon subscribed to his newsletter and availed myself of several of the book offerings. I have been an ardent fan and reader ever since...

I am looking forward to a better business year in 2009 and being able to purchase the simulation software and more books so as to be able to continue a small but profitable business. But I am really looking forward to learning enough to be able to possibly do preventive maintenance and repair work for others as an additional means of income."

David, YES you can.

And the reason I've published David's comments here is NOT to trumpet the fact I have a few fans out there.

Here you have a small business owner who, despite the economic slowdown - and the gloom served up by the mass-media on a daily basis, is looking forward to a better business year in 2009. And has identified - and is acting on - an opportunity to earn additional income by adding more 'strings to his bow'.

The global economy needs more David Schreier's right now. Perhaps more than it needs multi-trillion dollar stimulus. I think our politicians either entirely overlook this or underestimate it.

So the next time you hear someone whining about the cards they've been dealt in the current economic climate, ask them what five things they've done recently: books read; courses taken, to improve their lot in life. Far too many people won't be able to give you one thing, let alone five.

I heard from an experienced hydraulics technician with a young family, who got laid off recently. It came as a shock to him. But he quickly replaced the lost job with a better one.

And it came out during the conversation that, in addition to working full time, he's steadily progressing through Advanced Hydraulic Control, studying business management at night school and was one of the first to join my NEW Hydraulics Pro Club.

When he ends up running his own show, some people will wonder:

"Gee, how did HE manage to do that?"

No mystery to most of us.

The Nice Things People Say

"The knowledge I've gained from this information has been so valuable it has earned me a raise!" Find out more ...

Jack Bergstrom
Heavy Equipment Mechanic
Sharpe Equipment

2.   Straight talk about bent cylinder rods

In Chapter 13 of Insider Secrets to Hydraulics, I explain how to check the straightness of hydraulic cylinder rods and calculate allowable run-out. This is an essential task when repairing any hydraulic cylinder, because if a bent rod gets put back in, the life of the rod seal(s) is compromised and the cost of the repair largely wasted.

I also explain that bent rods can, in many cases, be successfully straightened and re-used. Provided they can be straightened to within the allowable tolerance.

One of our members who works for a cylinder repair company, sent me his counter position on this:

"In our experience, "straightened" rods are never really straight. They almost always have an S curve in them after straightening has been attempted - because they do not re-bend in the same place they originally bent. Using these bent "straightened" rods greatly compromises the column strength of the cylinder, and is unsafe for a heavily loaded cylinder. It also wears unevenly on the gland and rod bearing, and frequently doesn't seal well. For these reasons, we never try to straighten or reuse a bent rod. I would urge you to rethink your advice on straightening rods."

I respect Don's viewpoint. I just happen NOT to agree with it.

Before I explain why, let's clarify what I mean when I say "bent" and "straight". I'm not talking about bent like your elbow. I'm talking about a deflection that's only detectable with a dial gauge. In this context, a rod is "bent" when it's run-out is outside allowable tolerance, and "straight" when within allowable tolerance.

Now, here's why I don't agree with Don. Many years ago, I worked for a company which repaired a lot of cylinders off mining-size hydraulic excavators - 250 ton and above. So we're talking about rod diameters of 200 millimeters (8") and up. Many of these rods were induction-hardened. And a lot of them would come to us "bent" as defined above.

At the time, the replacement cost of the smallest of these rods was around 10 grand. So if we had refused to straighten these rods, we would have made a heap of dough - right up until the point our customers woke up and we lost all this work to our competitors.

Back then, we gave a 6,000 hour warranty on all our rebuilds, and the expectation of any rod we straightened to our satisfaction, was that we wouldn't see it again for at least 10,000 hours.

Notice too, I said many of these rods were induction hardened. In the interest of full disclosure, I have heard third or fourth-hand accounts of the induction-hardened layer violently shattering while straightening was been attempted. In my direct experience of straightening induction-hardened rods, I've never known this to happen. Nor have I ever heard a first or second-hand account of this happening from a reliable source.

My suspicion about this is, when it has occurred, the rod being straightened was bent like your elbow, rather than "bent" as I have defined it above. Either way, the benefit of doubt, and therefore the possibility of this happening, must be conceded. You have been warned.

And by way of concession to Don, attempting to straighten a rod that's bent like your elbow is a dumb waste of time. Whether it is induction hardened or not. Furthermore, not all "bent" cylinder rods can be straightened. And not all "bent" cylinder rods should be straightened.

But if you're a machine owner and your cylinder repairer has a blanket policy of not straightening "bent" rods - period, grab your cylinder and run in the other direction.

"This book has the potential to save many organizations lots of money. It should be on the bookshelf of every engineer, supervisor, planner and technician who deals with hydraulic equipment... it's worth its weight in gold." Find out more

Alexander (Sandy) Dunn
Plant Maintenance Resource Center

3.   Why hydraulic oil is different

Hydraulic oil is different to other lubricants. In my column in the January-February 2009 Issue of Machinery Lubrication, available here I explain why and examine a field trial which proves your hydraulic oil choice can save you real money.

4. Content for your web site or e-zine

Need some fresh content for your web site or e-zine? You now have permission to reprint these 'Inside Hydraulics' articles on your web site or in your e-zine, provided:

1. Each article is printed in its full form with no changes.

2. You send an e-mail to to advise us where you'll be publishing them.

3. You include the following acknowledgement at the end of each article:
About the Author: Brendan Casey has more than 20 years experience in the maintenance, repair and overhaul of mobile and industrial hydraulic equipment. For more information on reducing the operating cost and increasing the uptime of your hydraulic equipment, visit his web site:

5. Help us spread the word

If you've found our 'Inside Hydraulics' newsletter interesting and informative, then chances are you have a colleague who would too. Help spread the word about 'Inside Hydraulics' by forwarding this issue to a colleague. If they share your interest in hydraulics, then they will surely appreciate being told about this newsletter.

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6. Tell us what you think

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