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IMHO the cross sectional area of the penis and not of the tube is needed to calculate the pulling force
Correct. I use a tube that closely fits my size, so I ignored that. If you’re using a larger tube, you’d want the area of your shaft’s base.
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1.9 psi is 1.9 pounds per square inch, correct?I would imagine you’d need 6 psi to get 6 lbs of pressure pulling the penis outwards,
If you were pulling on 1 square inch of area, you’d need 6 pounds per square inch to get a 6 pound pull.
However, you have 3.14 square inches, so you only need 1.9 pounds per square inch to get 6 pounds of pull.
The larger the tube (or base, as Rocco25 noted) the more pull you get for the same amount of vacuum.
It’s the same principle as a hydraulic jack; you might only need a 10 pound push on the handle to lift 1000 pounds because the areas of the piston and the ram differ by 100x. The same principle applies to vacuum power brake boosters on cars, but they’re not as easy to visualize as a jack.