Anyone know anything about this contraption? I'd like to actually
GYRO FLUX COMPASS
Reg. U.S. Pat. Off.
Mfr's Part No 12002-1-B Contract No W33-038 AC-3827
AN 5751-1 Ser. No. AF-44 57054
BENDIX AVIATION CORPORATION
The plug on it has seven pins in a symmetrical hex pattern with one
pin in the center.
No more pictures--camera died. Damnit!
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.
I have one similar--110V-3ph 400cycles---I took an old ford alternator,
tapped off the three 3ph wires where they tie to the rectifiers, drove it
with a 1/4-+_ electric motor w/ pulleys & belt
and spun it up real nicely. if I recall, I had about 70 Volts at around 400
other alternators might be different--but most anything ought to get it
going.. you realize voltage & frequency both increase at the same time--
J> B.B. wrote:
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
One of mine is a gyrocompass (the axis of the gyro is
horizontal). The other is an artificial horizon (the axis of the gyro
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. :-)
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
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
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
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
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)
I don't have to like Bush and Cheney (Or Kerry, for that matter) to love
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
Of course, you still have the problem of coming up with 400 Hz
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.
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
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.