Insane Hydraulics
Bold and audacious blog about fluid power
So, another friend of mine showed up at the shop this week with a hydraulic cylinder from one of his rigs. "I need your help, man. The gland is too tight, and I don't want to wreck it. I do have this nice little wrench here, but it's bending hard, and the damned thing is not going anywhere!"
This would be the cylinder and the Facom 117.B nut wrench, "enhanced with leverage":
Nothing special. Just a medium-sized steering cylinder with, as is often the case, only a couple of 7-mm blind holes on the face of the extremely well-tightened gland nut. The Facom wrench is a good tool, and it is much sturdier than it may seem, but when enough force was applied to the improvised lever, the arms were flexing, and the pins were slipping out of the holes.
"Oh, I see what you need! You need a better tool for that, and you, my friend, are in the right place because I happen to have enough scrap in the shop to make one "in a jiffy"! Actually, I wanted to make not one, but two tools - because there was one "crazy experiment" that I wanted to try out for a long time, and this cylinder was perfect for my trial!
Now, before we go any further, let me tell you two things right away:
1) The best way to open such a cylinder (any cylinder, for that matter) would be in a proper cylinder bench, period. In that case, unscrewing the tight gland nut would be a breeze, and it would be perfectly safe! Our tiny shop does not have one, unfortunately, but since we are stuffed with other work, I can only afford to accept cylinder repairs from "friends and family," so I can't really say we need one (at least so far).
2) I am about to show you a couple of makeshift tools that I made because I really wanted to try something out, but as a "rural operator" I can think of at least a dozen other ways (or tricks) to undo the tight gland nut - just saying this in case you are already fidgeting in your seat thinking about a torch and an over-sized pipe wrench - I've done them all, believe me, so relax, strap in and enjoy the ride.
Actually... there's one last thing I want to mention. I sometimes encounter an opinion that hydraulic technicians should concentrate their skill set on solving exclusively hydraulic problems and that other shop skills are not that important for them. I strongly disagree! I think that basic manufacturing skills - namely machining and welding/metalworking skills - are of paramount importance for a good hydraulic tech because everything that we touch is either made of metal or is surrounded/supported by metal!
Basic is the keyword here. Maybe I can't make a +/-0.005 mm precision part on a lathe (at least not fast, and probably not on the first try), but I can properly profile and thread a cylinder rod. Maybe I can't run overhead beads, but I can definitely weld the said rod to the respective cross tube, and it will look nice (and even not fall off!). And since I also do over-the-counter hose assemblies - I couldn't possibly tell you how many times I had to weld something to something to make that "proprietary" hose tail for that special machine to work. So far - none of them came back. And if you give me an angle grinder, a stick welder, and a steel profile - I'll freaking build you anything!
I am not a professional machinist or a blacksmith, but knowing my way around their tools has saved my rear countless times in what seemed to be "exclusively hydraulic" situations. So, if you are an "aspiring hydraulic technician" - use (and search for) every opportunity to work with/on metal to gain that invaluable experience - you will not regret it! And if you are running a hydraulic shop, maybe think about finding a way to hone or upgrade the metalworking skills of your employees - it's always a win-win for everyone (and if one of your techs tells you that he does not want to learn how to weld because "we are not welders", well... at least you'll know who in your team has the "fixed" and who has the "growth" mindset).
For the record - I didn't know any of that when I started off, but I was lucky to get my first job at a company that, aside from the hydraulic department, also had large production facilities (industrial fishing equipment and winches of all types and sizes) and as a hand, I was often sent there to... well... give a hand with whatever was needed - and that's where I got my first hands-on with all of this stuff.
I realize that I already digress pretty badly here - but I still want to tell you a story from my past as a shop hand learning to work with rotary machining equipment before we go back to making our gland-removing tool - it'll only take another minute, I promise (and it is kind of important because it has to do with safety)!
One of the things that I was entrusted with was drilling out and threading the holes in winch drums - and the model that we were manufacturing had like a thousand M24 holes on each of the sides. I would spend days drilling and then threading (by hand - mind you!) and then drilling, and then threading... I was working on that massive old-school radial drill press, which had a 10kW spindle motor that could easily punch single-path 21 mm holes, and every time I would lift the bit from the hole, there was always a couple of metal shavings stuck to the end of the bit due to magnetism, and so I developed a habit of wiping the bits off from the end of the bit with my gloved hand every time I moved to the next hole. Until the day my leather glove got caught by the cutting edge of the drill bit, and the damned thing nearly ripped my arm off! Up to his day, I remember the feeling of my fingers being squeezed by the coiling glove and me pulling my hand as hard as I could and finally "getting it back" relatively unharmed... This is why I never wear leather gloves when I work on rotary machines. Never!
So yes - do learn how to work with machining tools, but never forget about safety because lathes, mills, and drill presses can literally rip you in half if you are not careful!
How about that? I started off with making a simple gland-removing tool and ended up talking about getting ripped in half by rotary equipment. Talk about getting side-tracked! Let us get back on track now.
What is the main problem of all removable nut wrenches (of face pin type)? The problem is that while they can potentially transmit significant amounts of torque, they are very easy to slip out of often shallow (and often ovalized) blind holes because there is no lateral force that would hold the pins in the holes (once again - this problem is easily solved on a proper cylinder bench with a fixed gland-rotating tool holder). My "big idea" was to make a normal nut wrench (maybe a bit sturdier than the Facom), but then add a second tool that would clamp onto the rod - and then I would close the cylinder with compressed air - the rod would be pressing the wrench against the nut, and thus I would be able to apply "indecent" amounts of torque to my tool without worrying about the pins escaping the holes, and also - the fact that rod is pushing on the gland nut from the outside would mean the compressing force would not be transmitted to the tube threads, and thus would not affect the untightening toque of the gland nut.
I know, I know - compressed air and hydraulic cylinders make a dangerous mix. But since I was going to close a cylinder with compressed air - the worst thing that could happen would be me pinching "something alive" (and, presumably, belonging to myself) between hard surfaces, so I promised myself that I would be extra careful, and, of course, remeber to vent the air pressure before removing the gland nut from the cylinder.
But enough talk, let us start making. First, I cut a 20-mm-wide ring from an old 120x145 cylinder tube and then marked and drilled four holes - two equally distanced (115 mm center-to-center) pairs - 3 x 6.8-mm holes (for M8 thread), and one 8-mm:
You may notice that I trimmed the ring in the lathe - but that's, obviously, not necessary - I just like the finish, and the center lines are easier to mark, too. Then I threaded the 3 M8 holes and cut the ring into two "jaws":
And then I shaped the inter-locking ends with an angle grinder and a steady hand:
Then I used a broken open-end wrench to create the handle. This is, by the way, a perfect example of why you should never throw away a broken wrench, especially when it is of a "serious" size - sooner or later you may need to create a custom tool - and broken-off wrenches make perfect and extremely strong handles!
And, finally, for the 7-mm pins I used a couple of 12.9 M8 bolts which I ground down using the good old hand drill + grinding stone trick:
And this would be the final product:
Now it was time to make the "rod clamp", and since I really wanted just a proof of concept - I quickly hacked together a basic clamp from two cuts of a 40-mm angle profile and 25x5 mm steel bar:
Finally, it was time for the big test! I inserted the pins into the holes of the gland nut and clamped the clamp onto the rod. It would be much better if the clamp had some sort of a wider base on the side that is pressed against the wrench because it was only touching the bolt heads with its corners:
But I still decided to give it a try. I connected compressed air (5 bar) and once again promised myself that I would not come near the rod end, which was under tension now, and if the clamp were to slip the bolt heads, it would shoot back - which was a major pinching (possibly severing) hazard. I only did it because I was so eager to try it out there and then, but I am an impatient idiot, so don't do this at home, kids!
All I can say is that it totally worked! The clamp kept the tool pins tight in the holes and didn't slip at all, even though I had to throw all of my weight against the pretty long tube that I used for leverage multiple times before the thread cracked (you can actually see in the picture that the tube got slightly bent!). The clamp thing does need the wider base, though. You can see that I also used the wrench to undo the piston, which had the same 7-mm holes. Very handy!
Anyhow, even though I think there's something to it (I mean keeping the pin-wrench pressed against a gland with the rod action) - this is an unsafe practice, because, as I already said, compressed air coupled with hydraulic cylinders are a dangerous mix. Strictly for professionals, who know what they are doing! But the wrench itself turned out not bad at all - so copy at will!