Electromechanical porn

[mikeselectricstuff]

.. enough power to enable the erection motors to run. Those are the motors in the cage, they are switched on by the mercury switches to provide a restoring force to slowly bring the gyro cage back to centre, with a higher power being applied if the fast erect button is pressed.  The reason they are slow is that if you fly with a bank for around 5 minutes they will bring the horizon bar back to centre, removing the bank. This is deliberate to allow the gyro to compensate for the rotation of the earth.

I'd pretty much concluded these were motors, but wasn't aware they would normally be running. I may investigate driving these as it would be nice to have it moving by itself as a display piece.

[robrenz]

There are gyro gimbal bearings that have driven intermediate races (like a bearing within a bearing).  Those middle races are driven opposite directions on each end of a gimbal.  It has 2 purposes, to eliminate the starting torque of the bearing which is higher than the running torque, and whatever bearing drag torque remains is equal and opposite thereby cancelling out. this allows as close to frictionless pivot action possible mechanically. 

Do you think this has this bearing style and the corresponding motor/s to drive the middle races?

[SeanB]

No, those motors are only powered when the mercury switch detects the gyro is out of level, and places a very low torque on the axis to restore the gyro to the central level. It is very low and slow, taking minutes to do so so that the motion of the aircraft does not cause it to show an incorrect attitude. It averages out the switch operations so that only the nett effect of a long period is acted on.  The motor is a split capacitor motor ( thus the capacitor on the gyro frame in the video) with the switch selecting a direction for reaction, or nothing when the axis is close to level.The fast erection switch simply shorts out a series resistor to change the action from minutes to seconds. If you are not flying level the fast erection will lock in an incorrect attitude that will take a long time to level out.

You do have synchro outputs from gyros, but these will not have a motor style core, but will only have a single pole rotor, fed via slip rings, and a 3 phase stator winding. This is normally used to drive either a computer or a 3 axis display ( a ball) remote from the gyro, allowing the gyro to be placed at the mass centre and the display to be at the cockpit a way away, where it will not be affected by false readings during turns or pitching.

[mikeselectricstuff]

The motor is a split capacitor motor ( thus the capacitor on the gyro frame in the video)

So would this effectively be single phase, like a normal induction motor with a run capacitor?
From memory  think there were 4 connections

You do have synchro outputs from gyros, but these will not have a motor style core, but will only have a single pole rotor, fed via slip rings, and a 3 phase stator winding. This is normally used to drive either a computer or a 3 axis display ( a ball) remote from the gyro, allowing the gyro to be placed at the mass centre and the display to be at the cockpit a way away, where it will not be affected by false readings during turns or pitching.

Presumably the wirewound pots on this one are used to provide a position signal for external systems - autopilot or co-pilot display perhaps?

[SeanB]

Yes, a simple 115V 400Hz split phase motor. Somewhere there will be either a big resistor, or a choke, to do the 2 torque settings.

The pots are probably an output to the autopilot to enable it to do attitude hold, so that it will keep the control inputs it makes to predetermined levels. The pots are probably fed with 26VAC 400Hz, so as to enable noise reduction, by sampling at the phase peak. A very common method on aircraft, where there are a mix of technologies, synchro and resistive sensors will use the same input circuit, and will give the same output as well for the same angle of rotation.