Moisture Meters?

[Fenton Murray]

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
>
>