The reading of this indicator is the gas mean pressure in an engine cylinder during a complete cycle of the engine. The housing 1 of the instrument is connected to the space in which the pressure is to be measured by connection 2. The housing contains cylinder 3 with plunger 4. The pressure of the gas moves plunger 4 downward, compressing spring 5. Through a four-bar linkwork, motion of plunger 4 is transmitted to segment gear 6 which meshes with gear 7. Mounted on the shaft of gear 7 is flywheel 9. The flywheel has a considerable mass and it absorbs all the fluctuations in pressure acting on plunger 4. Owing to its inertia, flywheel 9 holds plunger 4 in a position corresponding to the mean pressure. Flexibly linked to flywheel 9 through a spring is damping disk 10 which is mounted on shaft 11 together with hand 12 which indicates the mean pressure on scale 13 of the instrument.
$4021$THP,M$