Author: Gordon (NZ)
Date: 2002-10-30 11:27
A couple of pages down there was a thread "Help! My barrel won't come off! " started by 'Nick'.
There was discussion on whether a jamming tenon joint was caused by the tenon timber swelling or the socket timber shrinking as a result of moisture in the bore.
On 22 Oct I started an experiment. I removed the reinforcing ring from one end of a barrel, measured the bore at this end, corked the other end, and left the barrel full of water. Today, 9 days later, I took measurements of the bore again.
Ken asked me to report in a new thread:
Original diameter = 14.49
The bore is now somewhat oval
New minimum diameter = 14.50
New maximum diameter = 14.57
This suggests to me that when a grenadilla cylinder gets damp inside, it behaves like a metal cylinder that is heated, i.e. the inside diameter increases. This suggests to me that the socket bore diameter must increase if anything, and that it is expansion of the tenon that causes jamming. However the result raises more questions:
1. Does the bore diameter reduce if the outside diameter is constricted by a tenon ring. I think this most unlikely, but who knows!
2. Is it possible that although the tenon bore diameter increases when wet, the outside diameter remains essentially the same. This too, seems most unlikely to me.
The next step of the scientific process would be for somebody to duplicate the experiment, and also to test the above two possibilities with alternative experiments.
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The Clarinet BBoard
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