REFLECTOR:weak gas struts / beating a dead horse dept.

[Dave Black]

Alex,

> Are you saying that you can pull indefinitely (movement) on a sealed piston
> as long as you exert 14.7 psi on it?

Not quite. You'll have to overcome system friction as well as atmospheric pressure.

> you think that you will be able to pull out a (1 in3)
> piston with 14.7 pounds of force?

Yes. Once your pull force exceeds the force of atmospheric pressure plus the
friction of the piston in the cylinder, the piston will move. Once the piston
begins to move, it will travel to the mechanical stop of the system without
need to increase pull force any further. If the cylinder has no mechanical
stop, the piston will pull completely out of the cylinder.

Given that a total vacuum can provide only 14.7psi of 'suck' at sea level, any
additional piston holding force must derive from some other physical source.
What property of oil would increase the 'suck' of a true vacuum? 

Dave Black
Shortwing RG