Re: Music Box Cylinders
By Tony Gray, forwarded by Tony Gray
To: clocks@listserv.syr.edu
Subject: Re: music box cylinders
Good evening John,
>> Many thanks for your constructive and informative addition
>> to the discussion of music box cylinder repair.
Not at all, it's a pleasure to exchange ideas ( there are quite a few differing ones ) on this interesting subject. I can't tell from the mail header, but presume that you posted this reply to the list. As it seems to be of interest to several people I will do likewise.
>> I would readily agree that there is a benefit to "stripping"
>> a cylinder of all its pins if a major restoration is indicated,
I have seen boxes where attempts have been made to replace *some* pins and the result is not usually very satisfactory. Ok, it works, sort of, but invariably employs wire of a considerably larger size than the original. The new pins are nigh on impossible to set to the correct angle of rake and the melting of the "cement" inside the barrel will almost certainly destabalise and alter the positioning of some, or many of the other pins. Conventional wisdom has it that this is an "all or nothing" job, either you re-pin the cylinder altogether, or you settle for a cylinder with some missing pins.
>> A hot solution of alum
I have never tried alum, and I have never heard of anyone else trying it but yes, the theory sounds ok, if this will remove the pins without attacking the brass, fine.
>
>> Now I come to a question. I have advocated the use of pins
>> .001" or even .002" larger than the diameter of the original
>> pins. In your description of repair techniques, if there is no
>> softening of the brass surrounding a hole left when a pin is
>> dissolved, then the friction of a given hole might be presumed to
>> remain the same. In fact, if my argument defending the driving
>> or "pressing out" of old pins is valid, is there any need to use
>> larger replacement pins? I have done it because I was told to,
>> rather than from any reasoned conclusion.
Cylinder pins generally have a diameter of between 0.011" and 0.013" and again it is not considered good craftsmanship to increase the size, but rather to use damper wire as a plug in an oversized hole (there are always a few). There are a number of reasons for this and mainly concern the angle of attack of the pin on the tip of the comb and the geometry of the comb tooth tip.
>> I believe the pin should be "nudged" just enough to exceed
>> its elastic limit etc.
Hm, I'm going to have to disagree with you on this one, most musical box pins are raked anyway (more on this in a minute) and this process on its own will have a tendency to distort the hole a little. The procedure you are advocating will distort the hole on *both* sides and make life very difficult if the cylinder has to be repined again in the future. Not good I don't think from a long term conservation point of view.
>> My next question comes from observation of a technique of
>> manufacture which has never seemed to serve a useful purpose.
>> Why are pins sometimes bent ten or more degrees in "lead" of
>> their contact with the comb?
Ok, you will probably have noticed that the tips of the comb teeth on *all* musical boxes are placed at an angle *above* the axis of the cylinder. This angle is actually an amount of 15 degrees between the plane of the comb and a line from the tooth tips to the center of the cylinder. The cylinder pins do not *strike* the comb teeth, but gently lift them at a speed of about a tenth of an inch per second, then the important event takes place, the release of the tooth. What is of vital importance in any musical box is a clean and sudden release of the lifted tooth. With this in mind it is probably easy to see that the release of a tooth from a raked pin is going to be much cleaner than that from a radial pin. The other advantage of a raked pin is that it reduces the bending moment on that pin as it works to lift the tooth. There is yet another reason for raked pins concerning the pins action on the tooths "damper", but I doubt it is possible to explain this clearly without the aid of a diagram.
>> Finally, is "pin wire" still available, and from whom?
Yes and in all of the required sizes, but it is not of course sold these days as "pin wire" and neither is it conveniently prepared for that purpose.
Sufficient unto the day I think :-)
With best regards,
--
Tony Gray MBHI
Kent. England. UK
Tony@Goodwin.demon.co.uk |
(Message sent Wed 15 Nov 1995, 20:06:48 GMT, from time zone GMT-0600.) |
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