Insane Hydraulics

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Pressure Gauge That Measures Pressure Through Walls

I was "deep-cleaning" the shop the other day, and found a cardboard box with the phrase "old pliers" written on the side. What can I say? Even if a pair of pliers or an Allen key is broken, it doesn't mean one can't re-use them in a DIY project, so I tend to keep tools that lost their primary utility but still look too good to throw away. Unfortunately, I also tend to store stuff and then forget about it completely! (One of the reasons I started to put labels on all of the shop storage boxes this year). The amount of dust on the box meant it sat undisturbed in its place for a very long time...

I looked inside and got taken some twenty years back. I couldn't believe my eyes! I found a very old "project" of mine I honestly thought was lost. It's from the days when I was starting to work with hydraulics, and like any person who is initiating in an area that is new to him, I was inventing all sorts of crazy stuff back then (in hopes of revolutionizing the field, of course!) - and this crude contraption is one of such "inventions". The quality of the build (especially the welds) clearly indicates that it was hacked together by a person very new to anything shop-related. Still - can you guess what this thing is for?

I can give you a hint - it is supposed to work with a dial gauge - like so:

I'll tell you what it's for now. Back then, very few of the hydraulic machines that I used to work with were spoiled by the presence of pre-installed pressure measuring test points, and taking pressure readings was always a challenge. I still carry these two big (and very heavy) tool boxes filled with pre-assembled Ts (JIC, BSP, DIN, ORFS, CAT, KOMATSU, etc...) and straight thread adapters whenever I go out on a call (and very often hear people call me crazy for hauling around some 60 kg of hydraulic fittings I never use). I guess I like the feeling of being prepared, but I do admit that I don't use the stuff in the boxes as much as I used to back in the day.

Anyhow, since every pressure reading was a challenge, I wondered if I could invent something that would allow me to measure pressure in a line instantly, without disassembling anything. Kind of like electricians do when they measure tension with a multi-meter (you lucky bastards!). And so - I came up with the very ugly contraption that you see in the pictures above.

Yes - you heard me right. The hacked locking pliers are a pressure gauge! Insane, I know! My genius idea was to clamp a hydraulic hose, deforming it slightly into an oval shape, and then - as the pressure in the hose would change, so would the force that it would exert on the clamp, trying to return to its original round shape, and since this force would be proportional to the pressure, theoretically one could use it to measure the pressure inside a hose simply by clamping a device on it.

In my mind it would be like this - I would come up to a system, clamp the "super pressure gauge" on a hose - and then see an instant pressure reading! No fuss with removing lines and inserting Ts and of course - no oil spills!

Pure genius, I know. You can stop clapping (laughing?..) now.

But does it work? Actually, it kind of does, but at the same time it does not. I can even show it to you. I was so excited to find this relic from the past, that I decided to film it in action. Have a look:

Obviously, the hose tries to straighten itself out under pressure, and obviously, this tool shows this, but that's about it! You can't use this device to take an accurate pressure reading. The hysteresis alone is the size of a planet, and all other variables you need to take into account make such a system pretty much useless. Especially in this day and age when "proper" hydraulic equipment manufacturers (finally) started to include test points in their designs.

Still, I find the idea neat, and therefore I wanted to share it. This tool may not show a correct pressure reading, but it does show one thing. It shows how "insane" I was back in the day. And I like this memory. A lot. In fact - I secretly hope I didn't change that much!