Maybe people involved in mechanics and technology are aware of the concept of percussive maintenance.

During the Apollo 12 mission, when one of the cameras stopped working an Astronaut tapped on it with a hammer.  According to NASA, the failure was due to the Astronaut pointing the camera at the sun, burning out the vidicon tube.

I suspect that the inability of the Astronaut to repair the camera was due to the incorrect application of percussive maintenance, more specifically his choice of percussive tool.

The individual who taught me more about percussive maintenance than anyone else was one of my formers graduate advisors, a Ph.D. in mechanical engineering and former nuclear propulsion chief.

When something broke in the lab, our first instruction was “tap on it with a wrench.”

The point cannot be stressed enough: do not hit things with a hammer!

A hammer is not the proper tool for percussive maintenance precisely because hitting things is exactly what a hammer is normally used for.

Under normal circumstances, you do not hit an advanced piece of technology or complex mechanical system, but when applying percussive maintenance you do.  Since under normal circumstances you hit something with a hammer, under percussive maintenance you don’t.

These sorts of counter-intuitive ideas exist in engineering all the time.  How do you put out an oil well fire?  You blow it the fuck up with a shitload of explosives.  One normally thinks about explosives causing fires, but when you already have a raging fire, explosives blow it out.

The same is true with percussive maintenance.  The best tools for this are threaded fastener torque applying devices.

Wrenches and screwdrivers.

When light maintenance is required on delicate equipment, the handle of a screwdriver works best.  Again, we see the counter-intuitive nature of  percussive maintenance.  Hold the screwdriver by the bit and apply a dynamic corrective action with the handle.

If more dynamic corrective action is required, a wrench works best.  When using a wrench, an open-end wrench works best.

Note that standards here are critical.

Do not apply percussive maintenance to an SAE standard machine with a metric wrench or vise versa.   

In the lab we had a huge Dewar of liquid argon, with a pressure release valve.  If the valve opened up for too long, it would freeze the value open and continue to blow out argon.  So when the valve started to vent, one of us would continue to tap on it with a wrench until it re-seated.  One time one of the undergrads who was doing some work for us for credit tapped on the valve with the wrong standard wrench and causes to pop wide open.  Only through a smart strike with a metric wrench were we able to get it to sea again.

Note that this dynamic works even works on Russian equipment in space.

Percussive maintenance is a time-honored way of fixing things, but be sure to do it correctly, by applying the right too, which is actually the wrong tool for the usual job of hitting things.

When in doubt, hit it with a wrench.

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By J. Kb

14 thoughts on “Percussive maintenance with a threaded fastener torque applying device”
  1. Wrenches can solve problems in non-percussive ways, too.
    Back during my rather short stint in Corporateland, the software types were forever summoning me (and the other hardware guys) to the lab to look at “hardware problems” that generally turned out to be either software problems or really obvious dumb stuff like cables not being connected right.
    One fine day at Horror Fright, I came across a 24″ crescent-style wrench, which I (naturally) bought and kept in my cubicle for responding to “hardware problems.”
    My interruption rate went down significantly.

  2. Electronic devices only function because they contain a quantity of magic smoke inside of them. If something damages the device, the magic smoke escapes and then the device stops functioning. We used to refer to that as “letting the smoke out” of something.

  3. “Magic Smoke” (TM) is a property of solid-state devices. It does not apply to hollow-state devices. Fortunately, except in high-power applications, like the finals of a radio transmitter, and in antique electronics, we rarely find hollow-state devices, so I’m not surprised that Mr. Divemedic appears to have been unaware that “Magic Smoke” (TM) is not universally applicable in electronics.

    On the matter of percussive maintenance, obviously the racing team once known as “BFH” might not have been properly trained in the application thereof.

  4. Back its the late seventies, I was an operator at a nuclear test reactor. We were making the transition from analog displays (i.e. meters) to digital displays (mostly LEDs). With the analog meters, a few gentile taps with the forefinger was often needed to make sure meter movement wasn’t hung up. I was amused at times to see some of the other operator tapping on an LED display in an effort to bring the reading closer to the desired reading.

  5. This is why they pay us maintenance guys so much. Not so much for the hitting things with wrenches, but for knowing which wrench, where and how much. 😀

  6. Truer words never spoken.

    Much like it is important to have the correct swear or combination of swears in your repertoire to get the job done; you can’t just use any ol swear on any ol job. You need to have the knowledge and experience to match up the correct word with the desperation, frustration, and importance of the job

    When percussive maintenance move into the realm of requiring a hammer, it is no longer percussive maintenance, it is now persuasion. Persuasion has its place and is an important building and maintenance technique but is often I’ll suited for delicate work.

    1. My hammer don’t do delicate, when it gets involved, it’s either the piece of crap starts working or the hammer will destroy it, then I replace the defective piece of crap. Problem corrected, I’m now relaxed with a big shiteating grin on my mug.

  7. My best friend used to do emergency maintenance on radio transmitters. I.e. the stations main transmitter is down so they are using the backup and are losing 10k an hour in income.

    At that time a big supplier of those transmitters was RCA and their logo was a big red circle with RCA in it.

    When Jim and his partner got on site they would go up to the broken transmitter and with a big dead blow hammer hit it hard on that big red logo. 6 out of 10 times the transmitter would come on line. They would then order the needed replacement parts and get payed. Normal maintenance would then replace the part.

    RCA mounted the primary oscillator on the cabinet wall right behind the logo. Hitting the logo would start the oscillator going again.

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