Originally Posted by Drew Hause
Geoff: I agree the Birmingham date code is 'O' for 1963

Mike: it's complicated frown
Pressures can be converted to modern piezo transducer numbers using Burrard’s formula if originally expressed as (Long) Tons/Sq. Inch by LUP (Lead [Crusher] Units of Pressure), or by adding 10-14% if expressed as PSI by LUP.
Burrard’s estimated Long Tons/ Sq. Inch Lead Crusher Pressure (Cp) conversion to PSI (pound-force per square inch): (Cp x 1.5) - .5 = TSI, TSI X 2240 = PSI.

“Highest Mean Service Pressure” equivalent PSI transducer values as converted from LUP by Burrard’s formula:
2 tons/sq. inch (NOT 2 X 2240) = 5,600 psi (pounds/sq. inch) = 386 BAR
2 1/2 tons = 7,280 psi = 502 BAR
2 3/4 tons = 8,120 psi = 560 BAR
3 tons = 8,960 psi = 618 BAR
3 1/4 tons = 9,800 psi = 676 BAR
3 1/2 tons = 10,640 psi = 734 BAR
3 3/4 tons = 11,480 psi = 792 BAR (The SAAMI maximum for 2 3/4” 12g is 11,500 psi)
4 tons = 12,320 psi = 850 BAR



Drew, could you explain these conversions?

I just plotted PSI against Tons and got a near perfect linear regression of PSI=3360.5*Tons +1121.1. So the regression does not fit well with the origin, but my real question is why is it not PSI = 2240*Tons?

And if I could put my tire gauge on the chamber and, assuming it had the range capability, what would it read relative to these numbers here (i.e., are these PSI numbers real PSI as in a car tire?