[time-nuts] OT - DC-10 gyros

Bill Ezell wje at quackers.net
Wed Mar 27 16:40:22 EDT 2013

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 days).

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

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