Yamaha out of tune

[Ron Nossaman]

At 10:47 PM 8/29/98 EDT, you wrote:
>
>In a message dated 8/29/98 10:09:39 PM, nossaman@SOUTHWIND.NET wrote:
>
><<This doesn't happen with the floating plate
>system because the bolt is locked to the plate by the threads and the bolt
>head. Hope that makes sense. >>
>
>Ron; 
>I understood what you said...does that mean I should start worrying?? :-)

* Hmmm... I see what you mean. All things considered, I'd say no. Everyone
else, however, could be in big trouble. %-)



>As for the quote above, I understand that the bolt and lag are both locked to
>the plate via threads on/in the plate/lag but...........it is the lag to rim
>wood connection that I was thinking of.  Granted there will be little, if any,
>soundboard positioning post (conventional type) movement, as the board doesn't
>touch the plate, but won't there be expansion contraction in the lag/rim
>connection?  And if there is isn't that the same point as a regular
>conventional lag develops 'most' of its looseness??
>Jim Bryant (FL)

* Yea, but it's a different situation. In a conventional system, the lag
clamps the plate *down*. When dowels, pads, or whatever the plate is bedded
on, expand with humidity increase, the expansion that happens between the
lag threads and the plate contact is crushed. Then everything dries out
again, the wood shrinks, but since some compression set has occurred, it no
longer fully contacts the plate like it did before the last expansion. There
is now enough slack in the fit to allow the lag to be tightened to *fix* the
problem, which guarantees more compression set with the next humidity
increase. See, the lags didn't get *loose*, the bedding was crushed, and the
plate gets very slightly lower with each tightening of the lags. Actually,
the lags can be pulled loose by this periodic tightening, but it's the
constraint of the wood between the lag threads and the plate that causes the
problem.

With the floating plate system, the plate isn't bedded on dowels or wooden
pads of any sort (except the pinblock). Here, the bolt acts more like a leg
than a clamp. When the rim and soundboard panel expand with humidity
increase, they aren't constrained by much of anything. Since there isn't any
wood being crushed against the bottom of the plate during expansion cycles,
there isn't any cumulative compression set, and the lags/bolts don't feel
looser because the plate bedding hasn't changed. The bolts will loosen in
the rim somewhat because you will have some compression set in the wood of
the rim where it engages the bolt threads, but it won't be severe enough for
you to detect it.   

I hope I'm making this better, instead of worse.



>"expansion is progress..........isn't it?"
>Faintly Dull

It sure is for the people who sell me new pants with ever increasing waist
measurements at increasingly closer periodic intervals, and if you
understand that, you are surely past all hope. %-)

 Ron