Old Gyro Compass

Could that be what we used to call a radio compass? If so, it probably takes 400 Hz 3 phase power, 120V (I timidly think).

Can I probably poke around with a DVOM without hurting it?

I had one of these about 35 years ago. I probably still have some of the parts off it. As I remember, it was a single-phase 115 V

400 Hz. One or more of those big metal-cased capacitors on the gyro inner gimbal shifts the phase for the phase shifted winding to get it started. You can probably get it to start spinning with a large stereo amp and a signal generator. It doesn't actually take a lot of power, but the larger stereo amps can develop 70+ volts output. To get more voltage, you can bridge it across the two output channels' hot terminals. Then, you'd need to supply signals 180 degrees out of phase to the two amplifier inputs.

You could also apply 18 V at 60 Hz to it, but I don't know if that will spin it up to 3600 RPM. You'd also need to increas the phase shift cap by a factor of 6.3 Normal speed would be about 22000 RPM at 400 Hz.

Jon

Ping Jim Weir on rec.aviation.homebuilt

Hmm ... I've got two old Sperry gyrocompass type devices, which run from 115 VAC 3 phase, 400 Hz, and several of the points which I see suggest that this one does too.

Granted -- in the aircraft, the 115 V 3ph 400 Hz was generated by a motor-generator run from 28 VDC, but that was external to the gyro.

The slip-rings in the gimbal bearings are carrying three signals in, and the triangular pattern of the capacitors (I think) suggests that this one runs from three phase, too.

Mine, which was designed to run entirely in the instrument panel, has only a three-pin connector to feed it power. Yours is designed as a transmitter unit, to feed information to remotely-located panel indicators.

One of mine is a gyrocompass (the axis of the gyro is horizontal). The other is an artificial horizon (the axis of the gyro is vertical).

Both have torque motors surrounding the gimbal bearings, and a small dome-shaped object with five contacts and conductive liquid in them (possibly salt water), which feeds a balanced signal to the torque motors when the dome is pointed straight down (according to gravity). If it gets off level, it feeds an unbalanced signal to the torque motors, and forces the gyro to precess until its orientation is correct. This correction happens in perhaps the first fifteen seconds after power-up (and you can see the indicators wobbling like mad). After that, if there is any slow drift, it will correct that, as well. (But it might get errors introduced during continuous acceleration or deceleration -- or perhaps even continuous turning.)

Anyway -- I suspect that at least the gyro motor is spun up by the 115V 3ph, 400 Hz, and I also suspect that there are synchros or resolvers running from 400 Hz as well, to transmit the information from the gyro to the remote unit. Let's see -- the gyro motor needs three pins to power it, and the synchros have normally five pins, two of which (the excitation voltage) could be shared with two of the three phases to drive the synchro, requiring only six pins. It may be that the synchro excitation is separate (as it is normally 26 VAC 400 Hz), or that the last pin is a control voltage to cage the gyro prior to spinning it down. In any case, synchros have three wires on the output signals, or resolvers have four -- so that could also account for the last pin.

You might try tracing the wires back from the slip rings which take power to the motor to determine which pins they are. I would

*guess* (but please test) that they are pins A, B, and C (or 1, 2, and 3, if the connector uses numbered pins.) The rest of the pins don't matter if all you want to is to spin it up. However, you may need them if you want to feed the signal to a display.

Note that some VFDs (including my larger Mitsubishi ones) can be convinced to produce 400 Hz -- and can be convinced to back the voltage down to 115 VAC. Unfortunately, the most appropriate one, my 1/8 HP one, won't go that high in frequency. Obviously, the VFD is not what you want if you intend to mount this in your car or boat -- as the 220 VAC 60 Hz power cord would get a bit long. :-)

Good Luck, DoN.

It would be nice to get afull veiw of part I used to work for a insturment repair shop A strip and dip shop .Thay had soild state power supplys .Millions of parts shoe factorys full of parts

More info about the thing:

I *think* this one is supposed to mount with the plug sticking straight upward and the window facing the back of the plane. "Aft" down. In that orientation the gimbal will always settle with the butt end of it down. Any other way it'll settle at some weird angle that's very unstable. This has a mechanical caging device. A tag on the case says to run it for a few fre minutes and then rotate a knob. On the tail of the rear is a small port with a silted shaft inside. Rotating it will move a small arm in the rear that has a latch at the base. After a full revolution the arm and latch will retract slightly, releasing the gyro. The pin it caught was what I was holding in one of the photos of the inside. I had a photo of the caging arm, but that's stuck inside my dead camera.

Two of the pins are wired together, so, six wires. The seven pins are labeled A-G, A & C are tied together. Unfortunately, I'm nearly totally colorblind and the wires are faded, so I don't know what color goes where. I'll show an artsy-fartsy friend of mine and see if I can trace 'em.

All six wires go all the way to the gyro--there don't seem to be any sort of sensors on any of the bearings.

The delta-shaped arrangement looks like it may be a transformer or a bunch of inductors. Of all three rectangular objects, each has two metal plates going through in parallel and the wires going in go into the jacket. I can't tell if the two strips are connected, but I don't think they are.

The two large capacitors are in parallel. Both ends are tied to wires that go into the gyro housing. One wire from the gimbal feeds to one of the the capacitors, but all the rest go through the delta thingy.

I have the rotor from something similar. The shaft has three contacts on the end that obviously carry current to the windings. The gyro, roughly

2.5" in diameter, spins around this shaft on precision bearings. I suspect that mine is an "inside out" three phase induction motor, but I've never been able to get it going because I don't know what voltage to apply to the windings.

I read one time about a physics professor who had a large military surplus ship's gyro mounted in a suitcase. He travelled a lot and could spin it up (I think is was compressed air powered) inside the suitcase in the cab on his way from the airport to his hotel. When he got there, he would carry his bags into the hotel, being careful to keep the orientation of the gyro suitcase constant. After he checked in he would let the bellhop get his bags. As soon as the bellhop picked up the gyro suitcase and turned around to go toward the elevators, the suitcase would levitate upward around the handle and the bellhop would get into a terrible fix trying to wrestle with the suitcase which had seemingly come alive as far as he was concerned. I always wanted to build something like that.

-- Bob (Chief Pilot, White Knuckle Airways)

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DoN

I'm pretty sure nobody cares for this thread, but, 110 vac 3 phase "400Hz" can be generated with a Delco alternator (for any old car) coupled to a 3450 motor.

Jerry

Right, this is not a closed-loop gyro where servo amplifiers control torquer motors on the gimbals. It is just a free gyro.

That is the flux gate. The earth's magnetic field passes through the iron in those flux gates and is picked up by a sensor. There is some procedure where every hour or so you read the flux gate and realign the gyro's remote indicator with the earth's magnetic field. Of all three rectangular objects, each has two

Yes, these are the phase shift capacitors that allow the motor to run on single-phase power. From the motor, there should be one wire that runs straight to the connector. Another external wire goes to the motor, but also to the capacitors. And, finally, there should be one motor wire that just goes to the capacitors. The external wires should have connectivity to capacitor terminals. And, these should show no connectivity to any other wires. One wire from the gimbal feeds to

Yup.

Of course, you still have the problem of coming up with 400 Hz single-phase power.

Jon

I have a 400 single phase motor gen

What camera? How did it die?

When mine "stuck" I removed the batteries and set it aside until it shut down completely. I then replaced the batteries and it was fine.

Ted

It refuses to read any cards. I have two cards, the old one I tried reformatting with the computer after the camera butchered it, and no change. Tried letting it sit sans batteries for a while too. Olympus D-460. It's always been kind of temperamental. I figure it was built on a friday close to the bell. Figures it would crap out just when I get back to updating my website.

BB

It is probably *not* a good idea to format your camera's memory card with it *in* the computer. It is best to follow the camera's formatting procedure be followed carefully.

Jerry (who has ruined camera memory)

What kind of signal comes out of the flux gate? Could I determine which are which by probing them while I move a magnet around near the gyro? Ooh, I could build a gauss-o-meter.

Exactly what I needed to know. Thanks!

I like the stereo idea someone mentioned. My dad could probably borrow a signal generator from work.