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There is a spring Posted by Ari [Email] ![]() ![]() In Reply to: Tire pressure gage, jim Kane, Fri, 7 Jun 2002 10:34:37 Members do not see ads below this line. - Help Keep This Site Online - Signup |
There are three parts inside the tube of the pressure gauge - a cylindrical piston that fits closely to the walls of the inside, a spring, and the rod with the calibrated numbers on it. Note- The rod ISN'T attached to the piston. It floats free.
The spring pushes the piston to the bottom (input end) of the tube. When you push the gauge onto the tire, air pushes against the piston, which pushes on the spring. The equilibrium point is a function of the spring and the tire pressure. More pressure, the farther the piston moves. The piston hits the calibrated rod and pushes it out.
When you take the gauge off the tire, the pressure is released, and the spring pushes the piston back to the 'bottom'. But the rod isn't connected - it stays in place, because there's a little rubber grommet at the end to give it some friction.
So the pistons springs back, but the rod stays in place so you can remove the gauge and still read it. If you grab the rod, it slides back and forth easily, because it's not attached to the piston or the spring.
posted by 140.157.4...
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