What causes turntable rumble

Nsgarch...A plain journal bearing does not have metal-to-metal contact when the shaft is turning. The turning shaft functions as a pump to keep a film of oil between the metal surfaces.

Air bearings work the same way.

Nsgarch..."Wiffle grooves" are usually used on air bearings such as those in the gyros of the missile guidance systems I worked with. However, as Elizabeth says, regular journal bearings without grooves do pump oil quite nicely. Go look at any mechanical engineering text book.

By the way, your MIT connections don't impress me. Been there, done that.

Nsgarch...Although I attended MIT I transferred and graduated elsewhere in 1961. BMe. My work involved ongoing relationship (40+ years)with MIT Instrumentation Lab, now Draper lab.

The gyro wheel with air bearings is not driven by air jets, but rather by a motor. The wheel assembly is sealed.

It's been many years, but I seem to remember that the viscosity of the lubricant drags it into the narrowed part of the bearing clearance. As I said, check your text book (or maybe look in Google).

Nsgarch...Doc Draper first developed Inertial Guidance for aircraft. The first US Navy Inertial guidance system, MK1, for the Polaris missile was actually a clone of a German design for the V2 which (fortunately) never got into production. Draper's main contribution was the floated Inertial Rate-Integrating Gyro, IRIG, both for attitude sensing and as a component within the Pendulous Integrating Gyro Accelerometer, PIGA. MIT Instrumentation Lab got the guidance system contract because at the time they had the best gyro expertise. I worked on Mk1 (a bit) and all subsequent systems including the next generation, not yet deployed.

I never heard him called "Rusty". Where did that come from? It was always "Doc".