On Friday, April 7, 2017 at 5:30:08 PM UTC-4, Clare wrote:
On Fri, 7 Apr 2017 08:51:21 -0700 (PDT), wrote:

Yo Jim -- and anyone else who may be interested.

I spend an hour last night tracking down some noises in my furnace blower, using my usual piece of aquarium hose stuck in my ear g, and I wondered if there might be a market for an advanced kind of mechanic's stethoscope -- something that ought to be a piece of cake for someone like you.

Maybe something like this is on the market. If so, forget it. If not, consider this:

I had two noises, from different sources, and the interference between them made it all but impossible to find the origins of the noises. One was some mechanical interference between the centrifugal fan and its housing, at one end of the armature shaft; the other was vibration resulting from stickiness in the centrifugal throw-out switch (a fail-safe switch that prevents the gas valve from opening), at the other end of the shaft. I finally took the whole thing apart and found both problems, but it wasn't easy to find them when the motor wasn't running.

So, I wondered about the idea of making a small, cheap, battery-powered amplifier, with a mike and a headphone jack, that contained a couple of active, adjustable audio filters, one high-pass and another low-pass. Made a notching filter or bandpass filter to make it slick.

I don't play with engines much these days, but I can recall times when such a device would have made quick work of tracking down engine noises.

There it is. If you make it and sell it, the idea is yours. Watch out for patents.
They have been on the market for decades.. Steelman Engine-ear and
Chassis-Ear, along with 8-Mile-Lake and SKF TMST3 are pretty common in
the industry. The Chassis-Ear has several remote sensors you can
install in multiple places and switch between them on the run.

Too little, too late, once again. g

--
Ed Huntress