# Need help understanding a concept in Gyroscopes

1. Aug 6, 2014

### ME101

So I've been trying to understand a concept in gyroscopes and I hope the guys and girls here can help me with it.

I first read it here, the part about mounting 2 gyroscopes with their axes at right angles to each other. It said that the platform will remain totally rigid.

I tried to consult a few of my teachers about this but none of them seemed to have an answer why. I've been searching online and the closest I came to finding something that relates is an old US patent No. US3398586. Fig 1 seems to be working around the same concept.

So does anyone here know why this happens? Any help would be greatly appreciated. Thank you and have a great day.

2. Aug 6, 2014

3. Aug 8, 2014

### Baluncore

No forces may be transformed by the gyroscopes, without causing precession. The platform with the two gyroscopes must therefore be free to rotate space, or mounted in gimbals on a vehicle.

One gyroscope can give you a single reference axis direction, relative to the stars. It takes a second gyroscope, with an axis that is not parallel with the first, to resolve another direction. Given those two axial directions you know platform orientation relative to the stars.

A vehicle can be made to remain stable by sensing vehicle orientation relative to the gyro platform and applying torque to the vehicle to correct the vehicle orientation.

4. Aug 9, 2014

### ME101

Hi Baluncore and thank you for your response. I just want to know that if two gyroscopes with perpendicular axes are mounted on a platform that is in turn mounted on gimbals, will the platform maintain its orientation in space such that the gimbals rotate? If it does, why does that happen?

5. Aug 9, 2014

### Baluncore

Yes, it will be stable, but only if it is precisely balanced, has no friction in the bearings and is operated in a vacuum.

It must obey principles of conservation of energy and momentum. Without some external force being applied there can be no change in orientation. http://en.wikipedia.org/wiki/Gyroscope#Properties

It turns out that a gyroscope's frame of reference is the same as the stars. It is called a “gyroscope” because it was originally intended to demonstrate that the Earth rotates. http://en.wikipedia.org/wiki/Gyroscope#History