[time-nuts] OT - DC-10 gyros

J. L. Trantham jltran at att.net
Wed Mar 27 21:26:18 EDT 2013

Is this part of an HSI (horizontal situation indicator), ADI (attitude
director indicator), INS (inertial navigation system), or autopilot?  Are
the bearings dust?

Sounds like fun to play with though.  What do you plan to do with it?


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Bill Ezell
Sent: Wednesday, March 27, 2013 3:40 PM
To: time-nuts at febo.com
Subject: [time-nuts] OT - DC-10 gyros

Well, I can come up with something topical, read on. :)

I saw a 'Bendix yaw-rate gyro' on FleaBay recently for $14.50. Of course, I
had to buy it.

What I got was the yaw-rate gyro package from a Northwest Airlines DC-10
that was stripped for parts around 2000. The gyro included the pull tag with
tail number, the license number of the A&P mechanic that pulled it, and some
other cool stuff.

What it turned out to really be is two gyros with two sets of electronics in
one box about 6" x 2" x 5" box, all vintage '80s or so. 
Even better, it's a strapdown system. The actual gyro wheel is about the
size of your thumbnail. I've just started tracing things out, and I've
gotten the gyros to spin up. I really love mechanical gyros for some reason,
too bad there's not a gyro-nuts group. I'm going to have great fun getting
the package traced out and running.

So, to be a bit more topical, the package of course needs 28V 400Hz for the
gyros, 28VDC for something, and +/-15V for most of the electronics.

Question - anyone figured out some clever solution for the 400Hz power? 
I faked it with a signal generator and power amp, but that's a bit bulky.
I'm thinking I'll use one of the class-D amp ICs and a simple op-amp
phase-shift sine generator.

Topical in a more abstract way, strapdown systems really are very
interesting. They require precise integration of the rate output over time
to derive velocity and position, and really weren't practical until the 70's
when small enough computers existed to do the requisite calculations.  (I
worked on the nav system for the Trident missile back in my Draper Labs

Bill Ezell
They said 'Windows or better'
so I used Linux.

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