Results are In! Re: moisture in wool or wood.

[Richard Brekne]

Nice reply... interesting experiment... and you are right... I was trying to be a
bit picky... but hey... it paid off didnt it. I take exception only at your last
paragraph... as it seems you misunderstood my errr.. pickiness a bit.. my point
was that Terrys experiment left us with very little information at all with
regards to the size, shape...  or... for that matter amount of compresssion that
would be eventually exerted on the felt. In short... I think I am more in
aggreement with you then you yourself are... <smile> (for a change)

Ron Nossaman wrote:

> >Not meaning to be picky... grin.. but I will... how does Terrys experiment
> >yeild
> >any information about the amount of compression that would be exerted on the
> >centerpin ? I mean the drill bit is really hard and aint going nowhere... a
> >felt
> >bushing would give a bit, and I dont think we are exactly clear on just how
> >much
> >pressure it takes to cause a centerpin to get sluggish.
> >
> >Richard Brekne
>
> Nonsense! Of course you're meaning to be picky, Richard.
>
> My point was that it doesn't take much of an interference fit with hard
> maple to where you couldn't get the rod in at all by hand, so the hole
> didn't get all that much smaller, or possibly didn't remain round. I
> assumed that the couple of thousandths" of size decrease wouldn't make a
> heck of a lot of difference to the pin tightness because the bushing cloth
> compresses, especially if it was just out of roundness of the hole. Since
> Jim hasn't yet posted his results from soaking bushing cloth, and no one
> else has apparently even gotten any wet, I spent the last hour in the shop
> exploring this a little from the bushing cloth side.
>
> Using a dial indicator snap gauge I put together a while back for measuring
> string diameters quickly in the piano, I clamped it in the vise, and cut
> some short pieces of bushing cloth to test. I left the cloth pieces in
> place in the gauge, without disturbing it other than wetting it with a mild
> detergent solution, through each test trial.
>
> Unweighted, with just the gauge spring clamping the cloth, the initial dry
> measurement was 0.0355". Wet, after 5 minutes, it measured 0.0375", for an
> expansion of 0.002".
>
> Weighted with 150grams, dry measurement was 0.034". Wet, after five
> minutes, it measured 0.0355", expanding 0.0015".
>
> Weighted with 211g, dry measurement was 0.0338". Wet, after five minutes,
> it measured 0.035", expanding 0.0013".
>
> Weighted with 211g, double thickness, dry measurement was 0.067". Wet,
> after five minutes, it measured 0.0698", expanding 0.0028".
>
> Note the relative correlation to initial compression by the weight, and
> expansion. Note that the expansion is between 3.5% and 4.5% of the
> compressed thickness in all cases. I would expect the expansion percentages
> to change with different batches and densities of cloth. Nevertheless, this
> would seem to indicate that bushing cloth expands against and
> proportionally to resistance.
>
> Now you tell me how Terry's test tells us what we need to know about the
> size and shape of the hole, and I'll explain to you how it fits with my
> results to explain center pins tightening with humidity increases, if you
> really think it's necessary at that point.
>
> Ron N

--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:Richard.Brekne@grieg.uib.no