"Gyros"

Re: \"Gyros\"

Gyros do not have to have something physically spinning. There are vibration gyros and light beam gyros.
 
Re: \"Gyros\"

almost certainly no spinning parts inside. Solid state gyros are are used. The spinning ones need too much power and they are too delicate for a small boat installation. In small planes, they are "caged" i.e. de activated and locked, during aerobatics, so the bumpong around in a boat all the time wouldn't do them any good. You'd also hear them speeding up or slowing down when switched on/off.
 
Re: \"Gyros\"

OED definition…………a wheel or disc mounted so as to spin rapidly about an axis whose orientation is not fixed but is unperturbed by tilting of the mount………………

Ok, the accelerometer may do the same job and be much more suited to the environment of a boat but it ain't a "GYRO"!
 
Re: \"Gyros\"

There are rotational accelerometers as well as linear ones. I agree these are not Gyros.

However, there are solid state gyros as well.
 
Re: \"Gyros\"

The Raymarine "gyro" should really be called a rate gyro or rate of turn transducer.

They are a piece of piezo crystal mounted up such that it can detect rotation and give an output relative to the rate of turn. The software can then modify the pilots gain to cope with slow and fast turns with the same accuracy(!?).

Strictly speaking a "true" gyro has a spinning mass, be it a large rotating mass or a tiny photon (laser gyro), so calling these gyro is not strictly correct, but i suppose the crystal move in a rotational manner, even if only a fraction of a degree!

Geoffs.
 
Re: \"Gyros\"

So we are back to English language troubles and the way language gets bastardised until the new variation becomes de facto. I give up and reckon we should try to describe what we are talking about in detail to overcome language problems.
Yes a gyro is a spinning mass we could argue that all the others are gyro substitutes. A spinning mass gyro has the atribute of wanting to remain rigid in space and also of wanting to precess when forced to turn. A free gyro mounted in a gimball is usefull in a gyro stabilised compass in that the magnetic field continuously but gently aligns the spinning mass with magnetic field (north) suchg that any wild swings or rapid turns are accurately shown by the gyro remaining aligned to north.
A rate gyro is a spinning mass which is mounted so it isforced to turn with the ship but in being forced to turn will tilt indicating the rate of being forced to turn.
In an aircraft the former is called the directional gyro which may or maty not be autoamtically slaved to the magnetic north and is called the directional gyro or gyro stabilised compass. The latter type is the turn idicator oftern mounted with a spirit level type balance indicator all known is the turn and bank (or bat and ball) indicator.

Another type of gyro is the gyro compass. This is innteresting in that it relies on the effect of the spinning gyro when rotated around the earth. (One turn per day) this rotation actually causes the gyro to precess or align itself (if permitted to freely move) with the rotation of the earth. Which is incidentally true north. So you have a true bearing compass not affected by variation or deviation. Unfortunately these take a long time to align themselves and are only practical in large ships where they runn continuously.

Now about the time of the introduction of B747 aircaft the inertila navigation system was introduced. This uses alaser gyro which has laser beams rtunning arounnd in a circular space. 2 beams one in each direction such that if the device rotates then one beam arrives earlier and the other slightly later. By interferometry these changes in arrival times can indicate rotation very accurately. So they have 3 of these one in each plane of rotation. pitch roll and azimuth.
They also fitted acceleometers which measure acceleration can in various palnes. the whole nav system is based on integrating the acceleration with the time before deceleration if any again to determine distance travelled. The system had an accuracy approaching that of GPS.

Now years later it is found that accelerometers are cheap and can be used with computer technology to stabilise a boat autopil;ot with more accuracy thyan just relying on a floating compass needle.

here endeth the lesson on gyros olewill
 
Re: \"Gyros\"

I thought you meant those greek/turkish fast-food things, that come served in a pitta-bread... /forums/images/graemlins/frown.gif
 
Re: \"Gyros\"

Unless you are on a very large or very expensive vessel (read commercial or military) it is highly unlikely that your autopilot has a gyro at all. Ring laser gyro systems cost thousands of pounds. Your autopilot probably makes use of a flux-gate compass, which may or may not be "stabilised" electronically - I would think lower-end units do this through programming, though high-end sets might use accelerometers.
 
Re: \"Gyros\"

Raymarine autopilots do indeed have a fluxgate compass (mounted separately) but recommend the addition of a "gyro" if radar is fitted to better stabilise the picture. The gyro can be located separately (and is packaged like the compass) or built into the autopilot control unit (which presumably then has to be correctly orientated). This addition also allows the autopilot to "auto learn" which sounds well worth while.
 
Re: \"Gyros\"

To basics. Gyros measure angular velocity. Integrate it and you get angle of rotation. They require a fast moving item either rotational, vibrational or light.

Angular accelerometers measure angular acceleration using a slow moving mass, a spring, and a deflection measurement system. These are integrated to get to angular velocity. Then again to get to angular position.

Accuracy over short time intervals is high compared to GPS. Over long intervals accelerometers drift and need correcting.
 
Re: \"Gyros\"

There are some solid state "gyros" which operate as tuning forks. These can give angular velocity, and can be very small (and cheap). Does anyone know whether any maker is using them for boats?
 
Re: \"Gyros\"

[ QUOTE ]
Strictly speaking a "true" gyro has a spinning mass, be it a large rotating mass or a tiny photon (laser gyro

[/ QUOTE ]Do photons spin? And don't they have zero mass? (I'm only asking in a spirit of bloody-mindedness. Probably best just to ignore me.)
 
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