Gregory's ServerThis analog computer performed complicated calculations using lots of gears. How did this work? Shafts rotated and their angles indicated values. The main component is a differential gear mechanism, performing addition or subtraction.
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 The process starts with pressure measurements. Pressure transducers (black domes) convert pressure to rotation. Inside, bellows rotate a sensor shaft. This drives a servo feedback loop with magnetic amplifiers and a motor rotating the output shaft, outputting the log pressure. The pressure signals go to differentials (circle-X symbols). Then cams (CCD) apply various functions. Finally, synchro transmitters generate 3-phase electrical outputs that drive pilot instruments, weapons systems, and so forth. Temperature is important because it affects air density. A platinum probe measures temperature through varying resistance. Another servo feedback system produces temperature rotations. The CADC is modular: temperature is this wedge-shaped module. Synchros convert a rotation into three electrical signals. Connecting the three wires to another synchro reproduces the rotation at a remote location, e.g. pilot instruments. Numerous synchros provide outputs from the CADC. I wrote a blog post about the Bendix Central Air Data Computer with more details and photos: https://www.righto.com/2023/02/bendix-central-air-data-computer-cadc.html  @kenshirriff The use of the pressure and temperature servo loops to magnify weak physical phenomenon into something strong enough to turn downstream components is quite interesting. |
By using logarithms, multiplication could be done with addition. Specially-shaped cams converted to logs and back. Other cams implemented functions; 20 adjustment screws warped a metal plate to the exact shape needed.