Effects of thread wrapping, Series 2:




The seemingly miraculous recovery of our strangled boxwood test tenon in "Effects of thread wrapping, Series 1" gave us some hope that a bore-compressed flute, once liberated from its bindings and subjected to deep humidity cycling, might spontaneously gravitate back towards its original shape.  But it's one thing for a freshly-strangled, lightly-made tenon to achieve immediate and spontaneous recovery, and entirely another for a more heavily-built flute that might have been in that contorted shape for 100 years or more.  With the findings of our survey that most old flutes show significant level of bore compression, and that the level of compression is enough for the flute to be operating outside the realms intended by its maker, demand for returning flutes from near-death experience is bound to rise.  Restorers and owners need to know what's possible and what's not.  This experiment is intended to explore that void.

What's different in this experiment?

Surely the test tenons, and the restoration of the strangled cocuswood and boxwood flutes has confirmed that threads strangle flutes, and that we can detect and cure strangulation, restoring strangled flutes to good health.  Why do we need another experiment?

There are a number of reasons:

  • Firstly, the cocus and boxwood strangulation victims were other peoples' flutes, sent to me for repair.  There's a limit to the amount of experimentation you can apply to other people or their flutes without losing friends!  Dr Mengele would be remembered more fondly today if he had kept that in mind.

  • There's also somewhat of a time limit.  Customers are going to want their flutes back, preferably within their lifetime.  So unreasonable!  Don't they realise I have work to do here?!

  • Those two flutes were dramatically strangled, while our survey suggests most old flutes are in the moderately strangled category.  What's needed for seriously strangled flutes might be overkill (pardon the expression) for flutes at more typical strangulation levels.  We want to try coax, before push comes to shove.

  • The test tenon was deliberately lightly made, in order to speed up humidity cycling times and produce meaningful results without waiting for years.  It also was just a tenon, not a tenon connected to a flute.  We need now to see what a flute of more typical dimensions will do, and how long it takes to do it.

  • With a graded series of restoration options, we could get a chance to test the self-cure hypothesis raised in the test tenon investigation.

  • Should self-cure work, it offers the hope of finding out what the original bore might have looked like.  If it doesn't, we will have to find an answer to that conundrum ourselves.  Bring it on!

  • We focussed on upper tenons so far, but old flutes have two or three tenons, equally capable of being strangled.  Here's our chance to consider the lower tenons as well.

  • And, as in any experiment, we might learn all sorts of interesting new things along the way.

Meet the victim, er, honoured guest ...

Fortunately, our experiment has a prospective subject.  The Richard Potter flute included in the survey is a total basket case at the moment, having lost many keys, blocks and ivory rings. It's on my long-term list to try to save, but has no immediate prospects, baring perhaps intercession by Australia's newly canonised St Mary McKillop, or submitting to risky and unproven scientific experiments.  Looks like the latter option is coming up first....

As you can see, this flute has seen better times.  It came to me as part of a trade from Canada where it had laid around for years unused.  You can see why. 

It's Richard Potter's Patent Flute (you can just make out the word PATENT on the ivory band on the head).  He took the patent out in 1785, featuring these innovations:

  • metal valves, or as we have come to call them, "pewter plugs", on all keys

  • a metal tuning slide, with calibrations on the wood covered barrel slide

  • a moveable stopper with calibrations to match those on the tuning slide

  • an adjustable foot register (but only applicable to flutes with Short D feet)

This last feature is not applicable to our guest flute, as it has the C foot.  Well, C# foot as it stands at the moment!  As you can see, the stopper with its cap and calibrated indicator rod is missing too, replaced by a chunk of crudely carved cork.  I do have the G# key, but the upper c key, Bb key and long F key are missing, as is the hinge block for the upper c key.  The spring on the Short F is broken, and two ivory rings are gone.  And there is a bit of a crack in the barrel, as you can see.  "Would suit student."  "Ideal for the home handyman".

This flute will certainly suit our purposes.  It's old enough to be of interest to early music enthusiasts, and recent enough to interest Irish flute players.

I'll admit to a certain affection and reverence for Richard Potter.  While there were many, many makers in London, he was one of the much smaller number of innovators.  I'd like to find out what his flute really felt like to play.  Heh heh, I might be the first in over 150 years!

Eeek, an excision!

The first thing to note is that the flute has been modified.  This escaped my attention at first, as I was concentrating so much on compression in the top tenon, I didn't pay much attention to the rest of the section.  I took the strange change in combing halfway through the tenon as a sign of distortion caused by strangulation - it had some points of similarity with the tenon on the strangled cocuswood flute.  But, when I started measuring the instrument up, I realised the LH section was unusually short for a flute of this era.  Comparing it with the same section of a flute by his son, William Henry Potter, all became clear.  About 13mm has been taken off the front end of the LH section!  The change in combing style is actually where the old combing ends.

Who would have done such a thing?  We need to look no further than the middle to late 19th century.  This is about when high pitch came in, soaring to 452-455Hz.  (By comparison, Richard Potter back in 1785 might have expected something around 425Hz.)  This is quite interesting, as it suggests that this flute was still in use then, well into the post-Boehm period, and 50 to 100 turbulent years after it was built.  Almost assuredly a student or amateur's flute. 

You might think I was downcast to discover this, as it reduces the value of the instrument as a period piece, and complicates our quest to understand what might have happened to it.  But it's exciting too - I'd heard of flutes being shortened, and now I have one.  We'll want to work out exactly why they shortened it this much, and how hard it was to play at that artificially elevated pitch.  We'll also wonder if that was the best solution for their situation.  I predicted further up that we might learn a few more interesting things along the way, and its started already! And, although it complicates our quest, it certainly isn't a killer blow.  We just have to be a little more careful in our assumptions and calculations.

While we are there though, the nature of the shortening bears some interest for us in our primary quest.  To clarify, 13mm (half an inch) has been taken off the front of the section, which would have extended by this much to the left of the image above.  The combing on the left-hand side of picture is what remains of the original combing.  That to the right of centre is new, turned down from the full body diameter.  Note that the person who did the shortening, and therefore the new combing, chose to leave the new section of tenon a slightly larger diameter than the old section had become.  In other words, the tenon had probably already started to collapse by the time of the shortening, in the second half 19th century.  Further, the shortener was possibly aware of it, or he might have been tempted to blend the new work in better with the old.  Instead, he probably wisely left the new section of tenon as large as would fit in the socket.  Although we do have to allow that he might not have been aware of the bore compression and simply wanted the tenon to fit more snugly than the already compressed tenon did.

The bore

The bore graph below confirms what sad condition the poor Potter has fallen into.  Let's take a look...

  • The thick blue trace shows us the bore of the flute body and foot.  Normally, I would show such a diagram starting at the top of the LH section.  But, remembering the 13mm excision, I've shown it bumped to the right by 13mm to remind us of where the cone originally started.

  • The first 13mm is thus shown with the diameter of the head.  Being Potter's Patent flute, it has a tuning slide, meaning that the bore is lined in metal, and can be trusted to be essentially the same as when it was made.  At least we have one reliable point of reference!

  • The thin vertical dashed lines indicate where the tenons (and therefore the relevant sockets on the mating sections) lie.   And the compressions caused by the thread bands in the three tenons are exceedingly obvious, peaking at around X = 26mm, X = 200mm and X = 320.

(You'll possibly find your browser's Zoom facility of some value if you want to examine the bumps and grinds in the graph a little more closely.  Usually found under View.)

Remember I had mentioned, in the previous series of articles, that we had so far only focussed on LH top tenons.  Look at the two lower tenons on the graph above.  They are as distorted as the top tenon!  As the location of each compression will affect a different set of notes, we can certainly expect the flute's intonation to be different to when original.  Unless we are really lucky and they all miraculously cancel out!  Blessed Mary McKillop, I seek your intercession in a technical matter pertaining to a particular flute....

And, remember our excision, carried out in the second half 19th century.  Even though compression had already set in when the tenon was "moved down the flute" by 13mm, the current compression is still centred on the new tenon location.  Serial strangulation at work!

Conclusions so far.

Well, we embark on a new adventure, quite different to Series 1.  Now we're dealing with a real flute, and quite a well-known one. And we're dealing with real life distortions.  And, in the form of the 13mm excision, some real-life tampering.  While there may have been some scope for denial and quibbling in Series 1, we're now facing cold hard reality.  What are we gunna do? 

In our next article, already well advanced, we'll speculate on what the bore might have looked like originally, and examine the evidence for the competing possibilities.  After that, we'll formulate a plan for dealing with the problem.  I hope you'll join me for the ride.

On to Original Bore Shape, or

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  Created 5 April 2011