The effect of piston rotation speed and fluid viscosity on the performance of free-piston gauges with a controlled clearance was studied as part of an experimental program aiming at the better evaluation of pressure by these primary pressure standards. Calculated effective area is shown to be greatly influenced by both speed of rotation and choice of a fluid. An optimum rpm resulting in the smallest possible uncertainty in effective area should be determined experimentally for each fluid and pressure range involved. When all the pertinent parameters are properly selected an appreciable improvement in accuracy can be achieved.

A,falling body viscumeter was developed to measure viscosity of k~bricnnts behueen 10-I to 1 O5 P a s at high pressures (up to 3 G P a ) and temperatures of 20-200°C. The viscometer was incorporated into a variable-support pressure vessel mounted in a n Orframe press. A solenoid is zcsed to raise the .falling sofi iron p17rnger to its upper position, where it closes a pa.ir of contacts. O n deactivating the cipper solenoid, the ph~nger, falls to the lower position to close a second pair of contacts. FOIL times are measured by a timer in 0. Is increments. Viscosity of a few,fli~irls, namely a synthetic t~irbine engine oil, a mineral oil, white gasoline and a I : I mixture of the n~ineral oil and white gasoline were meamred to demonstrate capability of the system. For the synthetic turbine eng?ne oil, i.sovi~coz~~ czcrves for 1 02, 1 O3 and 1 O4 Pa.s are presented on a P -T diagram and estimates are made of the viscosity at which dynamic effects can be expected.

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A method is presented of designing optimum proportions for cylinders in the composite design of a pressure vessel that limits catastrophic fatigue failure.