Excellent. ----- Original Message ----- From: "Ron Nossaman" <rnossaman at cox.net> To: "Pianotech List" <pianotech at ptg.org> Sent: Thursday, January 31, 2008 6:09 AM Subject: Re: Moisture Meters? > >> You're right, EMC is important only in that it predicts dimensional >> change. If you want to know the dimensional change, measure the >> dimensional change...duhh > > "Simple" is the part we hustle past looking for the more difficult answer > and the shinier tool. > > >> Ron, did you calibrate you're sample using the standard >> shrinkage/expansion charts? > > Nope, I asked the wood directly. Make up a cross grain spruce strip for > the meter, maybe a foot long, and another identical one (test piece) just > short enough to be measurable with a 6" digital caliper. Make them from > the same plank, something of as uniform a grain density as you can find. > Make the frame and dial indicator mount and have everything ready to > assemble before you start finding the MC and expansion rate of the sample, > so you can do all this before the MC in the real piece changes. Measure > and weigh the test piece. You don't have a very big sample to work with, > so accuracy is important. I used a little reloading scale, and got the > weight in grains, but tenths of a gram on a digital scale should be fine > enough. Once you have the length and weight of the sample, dry it in an > oven at something around 200°F until the weight quits changing. Might take > an hour or two. When the weight quits changing, moisture content can be > considered to be zero. Measure and record the dry weight and length. The > MC% of the strip you'll use for the gage is figured from the data gotten > from the test piece as (wet weight - dry weight)/ dry weight * 100. The > dimensional change rate is calculated from the same data as a 0.001" per > 1" per MC%, and the gage strip is anchored in it's frame at an appropriate > distance from the end so that it will respond at 0.010" per MC% over it's > length. Set the dial indicator in the frame so the MC reading corresponds > to what your test data said, and you're there. Oh, I capped the strip with > a strip of maple where the dial indicator plunger rides, so it wouldn't > indent significantly over time. > > > > >> Your gizmos officially qualify to to be referred to as >> elegant....congratulations, and thanks. >> >> Jim I > > You bet. I want to see the new gage when it's built. <G> > Ron N > >
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