[time-nuts] OT - DC-10 gyros

Bob Camp lists at rtty.us
Wed Mar 27 18:20:57 EDT 2013


The first question is "how much 400 Hz power do I need?". Without knowing if it's tens of amps (no, it's not…) or a tenth of an amp, it's a bit though to decide how much to spend on the solution. 

Eight ohms at 28 volts would be just a bit under 4 amps. It's also right at 100 watts. I'd be very surprised it you need anywhere near that much current. You probably want a pure sine wave to keep everything happy. A lot of the simple inverters are "sort of" sine waves. I think I'd vote for something like an cheap audio amp driven by a nice clean / stable 400 Hz tone.


On Mar 27, 2013, at 4:40 PM, Bill Ezell <wje at quackers.net> wrote:

> 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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