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End bolt nuts

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I gather that the normal way end bolt nuts fit into the bellows frame is the way it's depicted on page 34 of the concertina maintenance manual: attached with two wood screws into an indentation in the top rim of the bellow frame.


My Wheatstone (the one I got from Greg J.) isn't like that. From where the chamois is coming up in a couple of places, I can see that the nuts are inserted into windows cut into the side of the bellows frame. One of the nuts I can see has come loose, and is sort of wobbling around.


What's going on here? What's supposed to be going on here? Are the nuts in this configuration meant to be glued in place, or held in place by friction, or what? Should I do anything about the one that's come loose?

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As I explained to Johanna when she considered buying this instrument it came to me as a hybrid. Someone had successfully grafted a Lachenal 6-fold bellows so that Wheatstone ends and rivet reed pans comfortably fit. (I should add that I was surprised to discover this combination myself. I reduced the price of this hybrid from what I would normally charge for a reconditioned rivet reed Wheatstone even though the sound and response was equivalent to a pedigree Wheatstone.)


Johanna, Lachenal used two methods to fit end bolt nuts. What we consider as the conventional method is a plate mortised into the top bellows rim and fastened with two screws. At some point, probably to save time and money another method was introduced that apparently involved routing a slot in the bellows frame and inserting a small brass plate with threaded hole to serve as the end bolt nut. I'm thinking that theoretically the insert should fit snug enough to prevent movement. In practice this is not always the case. Sometimes the inserts, which probably were originally glued in place, break loose enough to rotate a bit causing bulges in the endruns. My approach to securing this type of end bolt nut has been to rub some yellow carpenters glue, with sawdust if needed, into any spaces around the nut where it sits inside the bellows frame.


As a physicist you have an appreciation of the potential power of the inclined plane. The force exerted by the end bolts may continue to break the nut free.


This type of end bolt nut system is not as elegant as the other kind but I have to admit it seems to work most of the time and I have only rarely needed to replace one of the inserts.



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Hi Greg,


Yes, of course I remember the part about the bellows being Lachenal. I'd just gotten used to thinking of the concertina as "the Wheatstone" (because, as you say, it effectively is). And then I was a bit startled to see a loose end bolt nut where I wasn't expecting to see any end bolt nut at all.


My sincere apologies to the late Mr. Wheatstone (a fellow physicist, after all) for inadvertently implying that he had anything to do with this.

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