How Gyrocompasses Work + Corrections to Earlier Videos

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Published on Dec 29, 2023

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In this video I go over how a gyrocompass works, my own unique explanation of gyroscopic precession, and several corrections to my earlier videos. A gyrocompass is just a spinning wheel with 2 degrees of freedom and a mechanism to induce precession as the Earth rotates, thus allowing it to detect True North. Compare this with a gyroscope that has 3 degrees of freedom. Gyroscopes have 2 main properties: rigidity in space and precession, which is the change of direction of its spin axis.

In mainstream physics, precession is explained by the right hand rule: curl your right hand along the direction of the gyro spin with thumb pointing outwards, do the same for the applied torque, and the direction of precession follows the vector sum of the directions of the thumbs. In MES physics, I explain precession as the gyro spin and applied torques want to line up with each other, and that precession itself is a torque that can cause the gyro to rise upwards against gravity.

Gyrocompasses require an additional precession mechanism because the Earth rotates very slowly, so friction in the bearings typically can overcome precession due to Earth's rotation alone. One mechanism of inducing precession is by attaching a mercury tube to the gyro such that as the gyro lifts the tube due to its rigidity in space, the liquid mercury flows to the opposite side. This induces precession such that the gyro will spin opposite of Earth's rotation. Another mechanism is by simply adding a weight to the bottom of the gyrocompass: as the gyro lifts the weight, there is a downwards force by the weight that induces precession such that the gyrocompass aligns in the same direction as Earth's rotation.

Further in the video, I clarify some errors I made in my previous videos. The gyrocompass explanation image I showed previously was actually correct and my edits were wrong. The compensator weights in the WW2 gyrocompass video I went over were used to balance the weight of the gyro and not to induce precession; it too used a mercury tube setup which they referred to as a "mercury ballistic".

Timestamps:

Intro: 0:00
MES Note: 0:33
Topics to Cover: 1:19
How Gyrocompasses Work: 1:41
Gyroscope Properties: 4:22
- Rigidity in Space: 4:32
- Precession: 7:33
  - Gyroscopes want to line up with applied torques: 18:20
- Important Note: High spin speeds overcome small torques: 22:22
How Gyrocompasses Detect True North: 24:51
- Debunking Flat Earth high friction gyrocompass: 27:07
- Mechanism to induce precession: Mercury Tube: 31:41
- Adding a weight to induce precession: 37:53
Further Corrections to my earlier videos: 40:49
Outro: 43:29