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The topic is so large, and life is so short
Old fashioned rotating iron gyroscopes only

Other types include
- Fibre optic gyroscope
- MEMS gyroscopes, a subset of Vibrating structure gyroscope

as of December 15, 2018

Most of us have been fascinated,
at least for a minute,
by a child's "top" and/or a gyroscope.

Table of Contents

- Introduction
- My experience
- "my" defunct 1952 rate gyro & a working purchase
- Vtg Aircraft Part SPERRY Directional GYRO Indicator TYPE C-5 Aviation gyroscope
-_ Humphreq Vertical Gyroscope Aircraft Helicoptor VM02-0110-1
- Interesting On-Line Manuals
- Saturn Guidance .doc - from Charles Carter
- Temporary Other - Feb 2018
- Minuteman ICBM guidance unit

When the rotor isn't spinning, a gyro is just a floppy thing,
but when the rotor is spinning, the dynamics are so unusual !!
Odd that just making the rotor spin causes such a difference !!

High school physics instructs one how to calculate its reactions, :-))

assuming you can measure the angular velocity and moment of inertia :-((
but I still don't have a physical sense of its behavior.

My experience - not much :-((
In the Army, I was in the Nike antiaircraft missile program which used free and rate gyros as part of the missile guidance control system. However, I was in the radar/guidance area, not the missile area - so never physically saw the gyros.

After the Army, I considered myself a real techie hot shot, and lucky enough got a job at Minneapolis Honeywell Aero Division testing "HIG" and rate gyros. I can wave my hands and kind of explain how those work,
but a gyro

- configured as a compass,
- capable of finding "True North" using the rotation of the earth and "down"
- used for navigation,
eluded me.

A friend is an ex-submarine electronic tech who was inpart responsible for maintaining a gyro compass,

and another friend (Norman Paik) made his bundle selling Litton gyrocompasses.
Litton LN-3 Inertial Navigation System of an F-104 Starfighter

The purpose of this page is to wave my hands some more

and imagine that I understand the operation of gyro compasses such as used in ships, especially submarines :-))

A bit of a confusion - an aircraft "gyro compass" is frequently a free gyro which must be frequently preset to magnetic north. It is used to indicate "North" during turns and accelerations that cause magnetic compasses trouble. It is not self-aligning (using the earth's rotation) with true north in the sense of a marine gyro compass.

When stabilised the spin axis is maintained in the meridian plane by a precession equal but opposite to the drift at the particular latitude. When there is no tilting effect the marine gyrocompass will lose its directional properties and become useless. This is the case at the poles and also when a vehicle moves due west with a speed equal to the surface speed of the Earth. Because the latter condition can easily exist in an aircraft in the middle and upper latitudes, it cannot be used for air navigation.

Pictures of the SperryRand MK-19 gyro compass installation in the Nautilis Submarine on exhibit at Groton, CT.



"my" defunct 1952 rate gyro & a working purchase
- started December 2018, updated February 26, 2019.
Norman Paik was an army friend and was later associated with Litton Gyroscope. He died in December 2018. His widow, Kathleen, had heard Norman and I talking gyroscopes.
She asked if I wanted a souvenir Honeywell Rate Gyro Norman had, and set it to me :-) She had warned me that the souvenir probably had a defective motor winding.
And it did (as measured with an ohmmeter) :-( However, something is better than nothing, and here it is - fresh out of the mailed box.
Later correction, scraping the pins hard with "alligator clips" yielded the resistance almost identical to the purchased gyro, and 400 Hz will spin the gyro :-))
On Feb 22, 2019, Marc Verdiell showed me the clean up job he had performed on this dusty corroded gyro. Looks almost new - even the spring looks metallic :-))
  The right hand pictures are of a similar second hand rate gyro I purchased in January 2019 from E-Bay "Flying Fish Aircraft Parts" - Collins Honeywell 3326-2 Rate Gyro Assembly JG7005A55 GUARANTEED WORKING (8783)
On Feb 26, Marc Verdiell e-mailed:
"I received the [400 Hz] inverter yesterday. Today I could wait no more. Both of your gyro have been spun... I did not spin the “Hawaiian” one to full speed, but it spun quite well too.
Both are quite noisy, so I am a bit worried about the state of the bearings / balancing. I spun it first with cover on, just in case. I spun it down right after it seemed to have reached steady state.
Towards the end of the video I rotate it a bit and it does its gyro rate thing faithfully.
Takes about 50W to spin up, gets down to less than half that at speed.

New YouTube of spin up and spin down

So, what do we have here??
This is the under side of the base plate
Unfortunately, the specifications are not available (on-line)
There is no rating, such as input power, max measurable rate
I *guess* the measurable rate might be 30 degrees/second, a common rating when I was testing aircraft rate gyros

This shows important gyro axes (the plural of axis)
  • Spin Axis - the axis of the spinning mass
  • Force or Sense Axis - rate of rotation about this axis is what this instrument measures
  • Precession Axis - Rotation about the Sense Axis, above, applies force about this axis. This force is countered by the rusty Centering Spring
Sense Potentiometer - very fine wires wound about an insulating rod.
  • a positive voltage is applied to one end, see silver solder
  • a negative voltage is applied to the other end
  • the two pick-off brushes (actually wires) pick off positional voltage (rotation about the precession axis) for output
The Brits in The A4 / V2 rocket in detail: Bringing a V2 rocket gyro back to life (minute 6:29) refer to these tiny "brushes" as "fly legs".

A better view of the connection to the outside world.
pins A & B connect to the spin motor (DC resistance 75 ohms)
Pin E connects to the top of the Sense Potentiometer (512 ohms)
Pin F connects to the bottom of the Sense Potentiometer
Pin G connects to the pick-off brush of potentiommeter
Amphenol 7 Pin Female Plug MS3106A 16S-01S, MIL SPEC - works fine
Three Rotational Power Contact Points for the gyro motor
co-axial with the Precession Axis.
The other side of the Rate Gyro.
Seen is a corroded cylindrical capacitor. I'm *guessing* that it is used to phase shift the gyro power (likely single phase 110 volts AC 400 Hz). This can provide starting torque for the gyro (spin motor) - the third wire into the gyro motor. Since this capacitor is not polarized, and low loss, no need to disconnect it after start-up.
The side opposite to the electrical plug.
The right hand structure is another view of the Sense Potentiometer
And of course a top view :-)
Unknown structure, may be an off null switch?
The two wire contacts ('brushes") may be positioned between two conductive plates. This may be a switch to indicate some finite rotation about the sense axis of the gyro?

Vtg Aircraft Part SPERRY Directional GYRO Indicator TYPE C-5 Aviation gyroscope
AirForce type C-1, C-5, (Sperry) Handbook, Operation, Service, Overhaul Thanks to Marc Verdiell

Humphreq Vertical Gyroscope Aircraft Helicoptor VM02-0110-1
Vertical Gyroscope thanks to Ken Shirriff
ad from e-bay

Interesting On-Line Manuals
Elementary Non-technical Introduction to Gyro Gompasses
Good Start A 1944 Sperry (before Rand) GYRO-COMPASS GYRO-PILOT MANUAL
Add gun stabilization A navy document MK-19 and MK-23 gyro compass. 6.5 MByte
Wonderful ;-)) THEORY OF THE GYROCOMPASS ( ) 1,2 MByte Local copy)
Directional Gyro Indicators AirForce type C-1, C-5, (Sperry)
Handbook, Operation, Service, Overhaul
Apollo reference "Apollo guidance, navigation and control - Design survey of the Apollo inertial subsystem"
"Apollo Guidance, Navigation, and Control (GNC) - NTRS - NASA"
THE collection of Apollo info
including Spec for procurement of Apollo Inertial Reference Integrating Gyro Thanks Mike Stewart

Temporary Other - Feb 2018
from "" Feb 2, 2018

please have a look to the photos.
The "golden" gyro was fully tested in 1994.
Both seem to be in good working condition.
Both have 3,4 kg and give the same noise shaking slightly...
Which one should i open ?
I think the best way will be to desolder a small part of
the thin sheet metal strip of 1 cm size around the gyro, beginning at
the thick solder point and then continue mechanically with
assisted heat and rolling the sheet metal over a kind of a can opener.
Best regards

as announced i opened the gyro.
Please have a look...
Due to the size of the data i reduced the resolution of the pictures.
If you want more details then tell me what picture you mean...
Best regards


























Minuteman ICBM guidance unit
Ignacio Menendez May 15, 2019, sent:
also see PIGA accelerometer