 The Clarinet BBoard
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Author: clarnibass
Date: 2004-11-10 05:16
Hi
I searched but couldn't find this. What exactly is a polycylindrical bore? I don't really know what polycylindrical means but physically what does it mean about the bore? How does a bore that is not polycylindrical look like?
I noticed my R13 (which is polycylindrical right?) have a cone-shaped bore at the bottom.
Thanks.
Post Edited (2004-11-10 05:31)
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Author: Fred
Date: 2004-11-10 11:12
A polycylindrical bore can change bore diameters a varying number of times along the joint. This is opposed to a straight bore that measures the same diameter at the top of the joint, bottom of the joint, and anywhere in between.
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Author: Don Berger
Date: 2004-11-10 14:06
Hi C B - We have talked about clarinet bore configurations several times, so our archives are worth searching. While a number of our "good books" at least briefly mention the subject, the best, most comprehensive discussions [I know of] are in Benade's several works, and in Gibson, "Cl Acoustics", and especially Stubbins "The Art of Clarinetistry'" the latter 2 giving some measurement examples and their effects. To me, "polycylindrical" [a number of cylindrical sections-areas] merely describes a machinist's simulation of conical boring, which [I am guessing] is a much more difficult/expensive method in view of the very small dimensional changes desired for better tuning of the 12ths [clarion register-3rd harmonics]. I measured the top and bottom diameters of my Sel Omega's U J, as 14.83 and 14.75 mm's respectively, [.08 mm !] .Others, please help, got wordy again, dern it !! Don
Thanx, Mark, Don
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Author: Don Berger
Date: 2004-11-10 15:02
Gosh yes, Ken, many TKS for repeating this "Same Time Next Year" question and our current answering attempts. I find it similar to trying to describe "The Calculus" also a subject where I'm rather "out of my depths". Don
Thanx, Mark, Don
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Author: ned
Date: 2004-11-11 03:52
''I measured the top and bottom diameters of my Sel Omega's U J, as 14.83 and 14.75 mm's respectively, [.08 mm !] ''
Don,
Does this indicate that your instrument is wide bore or narrow bore? Seems from what I have gleaned over the time, that is is narrow.
jk
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Author: clarnibass
Date: 2004-11-11 04:22
Thank you for those links Ken. I read your post and the only thing I didn't understand, is if the upper joint is made from 3 cylinders, there must some small cone-shaped parts (even if they are really small ones) between every two cylinders.
Thank you.
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Author: Ken Shaw ★2017
Date: 2004-11-11 14:17
First, they run a small router all the way through. Then they run the medium one partway through from the top and then the bottom. Finally, they run the large one through a shorter distance from the top and the bottom. Thus the bore is stepped.
I think, but am not sure, that the steps (which are only a few thousandths of an inch) are then blended together at their intersections, but perhaps the corners are just rubbed off in the final polishing. I doubt that any blended areas are straight-sided cones -- just rounded off.
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Author: Don Berger
Date: 2004-11-11 18:00
Makes very good sense, Ken, any OLD machining technique I ever had is gone. There are of course are very specialized hones which could be used to "round of" any "rough" edges, or to cut a truly conical taper into the top several inches of the U J. Perhaps we have some skilled machinists who can help us out. John K, AU, I regard the Sel-O as being medium bore, between the 14.6 and 15,0 mm bores current. Many good LeB's are of this size. Don
Thanx, Mark, Don
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Author: shmuelyosef
Date: 2017-02-27 06:44
Reawakening this old thread. I understand everything that's been said here (I'm an ex-machinist), but I have yet to see a clarinet that is cylindrical even at the top joint. I play mostly older Selmers (I have two Centered Tones and a Series 9). If I measure the top and bottom of the LH joint of those, I get bore diameters that differ between 0.25mm and 0.3mm. I just measured my daughter's late model (ca 2000) R-13 and it has a difference of 0.3mm at the top and bottom of the LH joint. It does, however, have undercut holes which neither of my Selmers have. I also have a Leblanc Dynamique (early model before the Dynamic, Dynamic II and Dynamic H) and it has different entry and exit bores in the LH joint, but does have undercutting (large), and was made in the mid-50s.
The Selmers I own are generally referred to as "cylindrical" and the R-13 is, of course, the template for "polycylindrical" clarinets.
Is this really a useful set of designations? It appears that even in the early 50s when the CTs were launched, Selmer understood that intonation (and other aspects) could be improved by varying the bore diameter.
Regarding the 'cone shape' at the bottom, I believe that the conic transition to the bell has started in the RH joint since at least the turn of the century (1900)...correct??
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Author: Caroline Smale
Date: 2017-02-27 23:53
The Leblanc LL and similar models of the period, The B&H 1010 and 926, amongst many others all have truly parallel bores in the top joint.
++++ at the time of manufacture ++++
During use the failure to properly oil or look after the wood and/or fault swabbing or use of improperly seasoned wood, can readily cause a change to apparent dimensions.
A very common fault is that the bore swells inwards underneath the tenons, but especially under the top tenon, which is most subject to hot moist breath.
It is unsatisfactory to measure the bore very close to either end with a vernier or similar measuring tool as they often give misleading results.
A proper bore guage, capable of measuring all the way into the bore is the only accurate way.
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Author: Dibbs
Date: 2017-02-28 18:22
shmuelyosef wrote:
>
> Regarding the 'cone shape' at the bottom, I believe that the
> conic transition to the bell has started in the RH joint since
> at least the turn of the century (1900)...correct??
At least 1800.
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