|Object Name:||Type C Rate Gyro Mechanism|
|Year of Manufacture:||1960|
|Location:||Main Object Store|
A rate gyro is a type of gyroscope, which rather than indicating direction, indicates the rate of change of angle with time. The gyro has only one gimbal ring, with consequently only two planes of freedom and is used to measure the rate of angular movement.
The original concept of an integrating rate gyro was a design by Siemens dating from 1939. The concept was developed further in Germany during WWII where it formed part of the rudder control system on the Hs129 and was possibly used in the "V2" weapon. After the War the design was brought to RAE Farnborough eventually being offered to industry.
Each Rate Gyroscope consists of a 1.5” hysteresis gyro motor mounted in a single gimbal to give a precessional torque which is proportional to the rate of instrument rotation about the sensitive axis. A multi-coil assembly is mounted on an arm from the gimbal ring, so positioned that the windings move axially in an annular permanent magnet when the gyro precesses. A second arm carries a fine wire pick-off making contact with a fixed winding which is fed from a 28VDC supply and can be set for correct zeroing of the instrument. The voltage between the centre-tap of the DC supply and the pick-offs fed to one of the coils so that interaction of the magnetic fields opposes the precessional torque; thus the gyro precesses against an "electrical spring”. Other moving coils (the gyro shown has three coils but some models only have two) can be used for transient velocity damping or for enforcing an artificial precession, or can be short-circuited for electromagnetic damping.
The voltage between the pick-off and the supply centre-tap is proportional to the magnitude and direction of the precessional torque, so it is also used as the output signal. If a large capacitor is wired between the pick-off and the spring coil the spring still resists precession, but the gimbal does not return to its "neutral" position when the precessional torque ceases With this treatment, the output signal from the pick-off is proportional to the integrated rate of rotation.
The RAE design was modified by Don Kierley of Elliott Bros but was made in Flight Controls Division not Gyro Division. Variants of the gyro were fitted to Elliotts' Flight Control System for the Jindivik in the late 1940s and subsequently to the Lightning (the Type "B") and the FIAT "Flying Bedstead" and although it was proposed for Concorde it was not actually used.
This design was supplied for the General Electric AN/ASA-32 Autopilot & Flight Control System Group; used in F-4B/C/E, RF-101. Rate Gyros for Roll, Pitch and Yaw were fitted.