On Sun, 6 Mar 2005 09:47:58 -0800, "RST Engineering"
wrote:

So, oh wise and noble gurus of engine stuffings, what (sub) harmonics are
going to be of most interest to us and what is their mathematical
relationship to the fundamental?

As an extra bonus question, my sensor is going to be an old phonograph
cartridge. Should I use the lightest weight "needle" that I can find? How
about a tiny little ball of lead at the tip of that needle? Would that help
the sensor? Or hinder it?

Can't help you on the first issue, but adding the ball of lead to your needle is
going to lower its OWN harmonic frequency. The harmonic of the needle may be
brought within the normal range of the engine. Which means you'll get a false
reading based on the characteristics of the sensor.

I know it's contrary to the Weir philosophy, but commercial accelerometers are
available for less than $100. Just because it's not in the Digi-Key catalog
doesn't mean it doesn't exist. :-)

http://www.vernier.com/probes/probes...plate=acc.html

Since this is for an article, you might be able to sweet-talk Analog Devices out
of some of their acceleration transducers...they're pretty cheap, though the
company normally doesn't sell in lots of less than a thousand.

http://www.analog.com/en/subCat/0,28...0%255F,00.html

I got a buddy who works for a company that handles this stuff...let me email you
his address.

Lastly, once I get this sucker up and running with you all's good ideas, is
anybody game to bolt it onto their flying machine and report results? I can
do it for the 182, but I'd really like some other real-world reports.

Happy to stick it on my Fly Baby. A neat spot would be down on the axle next to
the video camera....

Ron Wanttaja