A brass tube, flattened in section, then rolled into a part circle. When pressurised it tries to straighten up, and this small movement drives a quadrant and watch gear to the pointer; for vacuume it tries to curl up more.

@Audin
Ya gotta love SteamPunk. The gauge range will be in inches of mercury, 30 to 0 is one Atmosphere (14.7psi) and +60 should be two more atmospheres or about 30psi, so go real easy with your compressor and never try and drive a gauge like this without an air receiver in line.

I think a SteamPunk air-clock would work great in some public space, but the running noise would drive you bonkers at home.

@macona
Most are unfilled, the most common filling is a light oil, but they can be filled with all manner of stuff, and blanked with various types of rubbery “socks” as well. Depends on the process/material being monitored.

But as soon as you see the vacuume side it suggests that it was unfilled.

@M@
Mullard did a radiation scaler that used transistor dual-ring-of-five counters to drive a row of meters as the readout, so they should make a fine (if obscure) clock display.

Going the other way, Practical Electronics once did a nice looking Nixie clock that consisted of a bunch of rotary switches cobbled together into a gear train, driven by a 1RPM motor.

The copper tube inside your gauge is called a Bourdon tube. I actually just wrote a short piece about how they work on the PopSci website: http://www.popsci.com/diy/article/2009-11/dissection-air-pressure-gauge

This project looks really nicely done so far. Nice work.

Looking at the size of the gauge, it’s probably in PSI. A gauge that size trying to withstand 60 ksi or bar would more than likely rupture, and the vacuum side is a dead giveaway. 30 inHg is maximum vacuum pressure, and so I’m guessing the other side of the gauge is in english units.

I figured the stepper was acceptable to get the project moving along.

When I run into another gauge I might try animating it with steam. A small electric boiler and two solenoid valves. If nothing else it would make neat sounds….hhhhiiiiiiiisssssssss. But it wouldn’t be something you could leave running for extended periods. One question I have on this though is what sort of pressure ranges these gauges run over. There isn’t a unit printed on the face of this one. So I’ve no idea how much pressure ’60′ would imply.

I like the idea of a kitchen timer. You could do a completely analog one. A button to pressurize the gauge and then a controlled release of pressure (i suppose that would be the hard part) would cause it to count down. You could use co2 cartridges for the pressure supply.

As far as them being oil filled… a few are. Extreme duty gauges are to dampen vibrations. The cheaper ones that I’ve taken apart just have a curled copper tube that straightens out slightly and turns a gear as the pressure goes up.