I've been doing some rough calculations to get an idea of the effect a vacuum behind a piston might have. Can someone check my sums for me?

Calculation of the area (A) of a piston with a 70mm diameter (= 0.07m) is

0.07 m X pi

= 0.2198 m^2

(And pi = 3.14)

Pressure (P) of 1 bar = 100,000 pa = 750 mmHg = 14.5 psi = 29.5 "Hg


Putting the (metric versions of these) numbers into the relationship Force (F) = Pressure (P) X Area (A)

Force (F) = 100,000 Pa X 0.2198 m^2

Force (F) = 21.98 N = 2.24 kgf = 4.94 lbf



The relationship / equation above is assuming a frictionless perfectly sealed piston where the pressure (P) is the pressure difference on each side of the piston.

Please note this is a scalar quantity - no "plus" or "minus" sign has been used to indicate the direction of the force.

I plan to do some more complicated calculations - but I thought I'd check to first to see if I can get the basics right!

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



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