Abstract: A guide rod extends longitudinally through the power piston of a vacuum power booster providing lateral support thereto and tying the master cylinder housing to a bracket on the rear of the power booster housing. A guide rod provides a means of positively laterally supporting the power piston, control valve and push rods of the power booster thereby providing the ability to reduce the relative supportive strength of the housing, housing divider and piston bearings.

Abstract: Apparatus for directly measuring the quantity .sqroot..rho.ck of a test specimen such as a wind tunnel model where .rho. is the density, c is the specific heat and k is the thermal conductivity of the specimen. The test specimen and a reference specimen are simultaneously subjected to the heat from a heat source. A thermocouple is attached to the reference specimen for producing a first electrical analog signal proportional to the heat rate Q that the test specimen is subjected to and an infrared radiometer that is aimed at the test specimen produces a second electrical analog signal proportional to the surface temperature T of the test specimen. An analog-to-digital converter converts the first and second electrical analog signals to digital signals. These digital signals are applied to a computer for determining the quantity .sqroot..rho.ck by computing the quantity ##EQU1## WHERE T.sub.