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Automatic tire deflators are popping up all around the world. They vary in size and shape, and some
look virtually identical to our Staunies. My objective was to see how they worked. And since I was
not in on the design, I could not say what the other manufacturers' design objectives were, or if they
were working properly, all I could do was report how they worked for me in the situations below. The
videos present that information.
However, I can tell you what the Staun automatic tire deflator design objectives were. We wanted a valve
that decisively turned on, decisively shut off, and did not leak after shut off. We wanted a deflator
that was easy to adjust without tools, and was repeatable and reliable.
I first put all of the deflators on our standard trade show tire deflator demonstration fixture. I'd
inflate the simulated tire to 30-something psi, screw a deflator on the standard valve stem just as I
would a tire, observe and listen to how it started and shut off.
All deflators were adjusted to 15 ±2 psi. Some of the valves were hard to adjust because they did
not have distinctive turn on or turn off qualities. Since I had a microphone near the valve stem, I also
tried looking at the audio waveform to determine if I could see a distinct change in waveform amplitude.
On some, this helped and on others it was of no help.
View air test video
Knowing that my ears, and maybe even the microphone could miss the sound of residual air flow after shut
off, I ran each valve underwater. Water reveals the slightest trace of residual air flow. The fixture
is simply a two-port manifold, underwater, with gauges and valves to measure and control the process. I
had a video camera and microphone to observe the whole thing with lasers to help disclose even the
slightest trace of bubbles. I chose to run each valve along side a Staunie to ensure the skeptical that
there were no tricks.
View water test video
Using water idea is not new. When I first evaluated the Staunies for my newsletter in 2001, before I
went to work for Staun, I did the same thing. And for the skeptical, I have personally had the occasion
to lower my tire pressure in a stream after finding the stream bed traction gave out, so using the
deflators underwater is not that far fetched.
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