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bass clarinet extention piece

11K views 47 replies 12 participants last post by  pangul 
#1 ·
I recently made a bass clarinet extention piece for my instrument and I need some help figuring out keywork. It is made of abs plastic and wood, plays in tune, attaches to my existing bell and will soon be painted to match my instrument. Pictures can be supplied if asked for
 
#5 ·
I have a more german style bass clarinet so the bore does not flare at the bottom, I determined this by caliper measurements at the top, middle and bottom, all .91 inches. However with a lathe or a small file and a lot of time you can make such a taper. To remove the taper from the existing body, you could make a small piece to fit inside the instrument or use wax/tape.
 
#8 ·
I apologize for the length of this post.

Right, how I made my extension piece.
This can be broken down into a few steps: measurement, calculation/design, building and tuning.
The first step was to measure all of the tone holes on my instrument: the measurements were frequency, diameter, depth and distance from the top of the instrument to the top of the tone hole (not the with the mouthpiece or neck but where the neck connects to the body). In hindsight I really only needed to measure the notes in the table below. All of my measurements were in Inches as that was the caliper that I had. All measurements should be to the hundredth of an inch or smaller.

All math modified from Acoustical Aspects of Woodwind Instruments, Revised Edition by C.J. Nederveen

After the measurements were taken and recorded in a data table, i created a ti-89 titanium graphing calculator program to do the math for me (program available if you have an 89, just ask). To start out I calculated the acoustical length from the equation Acoustic length=speed of sound/(4*frequency). If using inches the speed of sound is 13622.0472 in/sec and if mm it is 346000 mm/sec.
I then calculated the length to hole with the mouthpiece attached
D1=.325*di of hole*(di hole/(2*g)^.39-1)
g=2^12-1
lah=(.25+di hole+D1)*(di bore/di hole)^2-.45*di bore
z=.5*g*sqrt(1+4*lah/(g*acoustic length))-.5*g
D2=(-3.3*10^-4)*frequency/(speed of sound)
LL=acoustic length-z*acoustic length

To calculate to length of the mouthpiece
Create this data table in Microsoft excel or similar
Numbers
note frequency number Actual Length LL Mouthpiece Length
A 196 1 (=LL-Actual Length)
G# 185 2
Thumb F 155.56 5
E 146.83 6
low A 98 13
low G 87.31 15
low F 77.78 17
Lowest E 73.42 18

Run a linear regression for frequency vs. mouthpiece length
Run a linear regression for number vs. mouthpiece length
Write the equations down and weight them so they are more closely related to the lowest E
Calculate the Mouthpiece length for the next notes, table below

note frequency number LL Mouthpiece Length Actual Length
extension D# 69.3 19 (=LL-Mouthpiece Length)
extension D 65.41 20
extension C# 61.74 21
extension C 58.27 22
note B 55 23

Calculate the relative lengths of the pieces
change distance
E flat to D# (=Actual length first-Actual length second)
D# to D
D to C#
C# to C
C to B

Design
I created my extension piece in five parts, one for each tone hole and another because i made a female joint where i should have made a male joint. All of the pieces will have the same interior and exterior diameter as your instrument and it is advisable to make all the tone holes the same size to facilitate finding keywork and pads (all of mine are .85 in. diameter). Skills on the lathe are highly recommended in this next part, else you can have someone else make the part for you and you can tune it.
The lengths that were calculated earlier are to the top of the tone hole. The first piece should start as the length from E to D# holes, minus the length of the top of the E tone hole to the start of the bottom tenon. Then that piece needs to have designed into it a female joint that is slightly larger in diameter(by .001-.002 inches) than the diameter of the bottom tenon cork, slightly compressed by the caliper. Then add the radius of your tone hole length to the bottom of this piece and that is the center of the tone hole. draw in the tone hole, add about an inch and a half to the piece and create a male joint. continue with previous steps, until the last piece is reached. Add the remaining length to hole where B should be and create a male joint to fit into the bell. (I made a female joint and it took me a week to fix it).

Building: I had access to a 3D printer, so i used that for the majority of my model. A lathe and drill press would work fine, or sending plans off for someone else to make it.

Tuning: This piece will be slightly out of tune, it is a fact of life. To sharpen the note sand the top of the male joint down as well as the tenon in question to fit. To flatten-pull out

Final Shaping and such
there needs to be an eighth inch deep, quarter inch wide groove running around the middle of each tenon to attach cork. This is best done with a hand file or lathe. The tone holes need to be leveled then cut to the proper shape. The outside and inside need sanding, any sharp corners need a slight bevel and if it is made of abs plastic it needs painted, proper clarinet wood needs oiled and other woods, oiled, waxed, or otherwise waterproofed, not sure on the best method.

*most mistakes can be fixed with super glue

Pictures:
 
#11 ·
If I remember correctly the Vito model 7168 bass clarinet (the version with the low-Eb on the body, and a plain bell without tonehole) has a flared bore towards the bottom, similar to soprano clarinets.

For what it's worth I've built about a half-dozen low-C extensions to date, half of them straight and half of them curved. I currently play on two instruments with my own extensions, an old Kohlert Boehm-system bass with a curved low-C extension; and an F. Arthur Uebel (courtesy of Ben) Oehler-system bass with a single-note straight extension for low C (the factory instrument, with just a bit of added keywork, had a range to low C#).

In another thread you may find a photo or two of my former "Frankenhorn" (since sold), a metal Kohlert bass clarinet (Boehm-system) with a curved extension to low C, and using an alto clarinet bell at the far end.

I did not use any calculations to determine the lengths of the extensions or locations of toneholes; I just measured a few other low-C instruments and fine-tuned my extension designs using good old trial-and-error (heavily biased towards the "error"!).

It's a lot of work to make an extension, but very satisfying when completed and working; and sure beats paying eight or nine thousand dollars for a factory Buffet or Selmer low-C instrument (in my humble and financially-constrained opinion).
 
#18 ·
From what I can remember all bass clarinets bell bores continue to widen, and I assume they match the connection it to the end of the low joint bore, to continue it. When you say from its receiver I imagine you mean from the bottom of the receiver, which is the beginning of the bore.

I think this is because it requires less complex tooling to replicate a tapered bore than a polycylindrical one.
Are you saying that a polycylindrical bore doesn't benefit from the flare while a non-polycylindrical bore does? Eeither way, AFAIK the professional models made now and also most (maybe all, or almost all) in the past have a straight bore.
 
#23 ·
I make my 'custom' keywork mostly from brass rod stock purchased at the local hardware store, and the key touchpieces/spatulas either from flat brass plate stock cut and bent to shape, or from bits of donor sax and bass clarinet keys and rods out of my 'junk box'. All soldered (brazed) together with high-temperature silver solder, then after grinding/filing/sanding all the joints smooth, I silver-plate everything with liquid silverplating compound obtained from Caswell Plating.
 
#25 ·
For brazing (a.k.a. "silver soldering") I'd suggest you get a good high-temperature silver solder (my favorite is from Ferree's Tools), some compatible flux (acid paste or liquid which is brushed on the area to be soldered to clean and prepare the metal), and a MAPP gas bottle and torch head (for high-temp soldering) or propane gas bottle and torch head (for medium-temp/lower strength soldering); these things are sold in every hardware store and large variety stores (the most common brand in the US probably is BernzOmatic, see link below:)

http://www.bernzomatic.com/products/torches/professional-torches.aspx

It takes some practice to learn how to jig up the mating pieces, how much heat to put on the joint, and where to place heat sinks (large metal clamps or pliers, for example) "downstream" of the joint area to keep heat from traveling down the rod and damaging/melting/de-soldering other joints (if any) along the rod.
 
#26 ·
Hobby lobby has angered me
I found brass online from them, but when I went to a store they had a few sheets, double their online price, and a box of bent sixteenth inch rod. Nor could I find wood glue there. Local hardware stores have not turned up anything in the rod or tube department, but I did manage to find wood glue and some eigth inch brass salvaged from a doorknob facing. I have determined that the brass needs to be ordered online, with the expected high shipping.
 
#29 ·
How about a Dremel with a cutoff wheel? I can cut through soft steel or solid copper of that thickness with this setup. It does wear out wheels pretty quickly, but they come in 20-packs for a reason. Also, because the wear of the wheels themselves carries a lot of the energy of cutting, the parts don't get as hot as fast as you'd expect.
 
#34 ·
Does anyone have an idea of the measurements of a low D extension for alto clarinet? I have a friend that said he'd lathe it for me out of wood, but I just need the dimensions.
 
#35 ·
According to my table, to get from Gb to F (which is the Alto's "D") you need to extend the tube from 935.15 to 990.76 mm, which would mean an extension of 55.61mm (make it >56 mm to be on the safe side). If the extension needs a tone hole, make that in the same spot as the bell's tone hole, ie think of the extension as a rather short and straight bell.

Inner and outer diameters as well as socket depth and tenon length depend on your instrument.
 

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#45 ·
it is possible that there are leaks that I haven’t seen with a leaklight, I got rid of one on the bell key. Where I did see a leak (and it played better straight away)I could float the pad..........but I am not a technician.

I will have the horn looked by Casper van der Spek.
 
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