The University of Warwick, where I study chemistry, holds the Rootes Memorial fund that allows students to complete a project unrelated to their degree.
Born from a dream, it is due to this fund that I have been able to build my cornet.
Andy Taylor, (who builds the fantastic Taylor series of trumpets) agreed to teach me to spin the bells I would need for the echo
chamber. I visited him at Christmas and watched him construct the echo bell mandrel on a lathe, by cutting down from a solid cylinder of brass. This was based on a Hawkes and Son echo cornet I had borrowed.
I needed to build two bells – one small, using the mandrel Andy had built, and a longer bell to connect the echo to the 4th valve. The basic shape was cut out from lightweight sheet spinning brass,
bent centrally over a bar mandrel to curve it, and the edges flattened to about 4mm. Brass becomes stiff on working and so has to be constantly annealed throughout the process. Tabs cut into one of the flattened
edges overlap when the edges are forced together. This is done in two stages due to the flare of the bell. Wire is used to hold the unfinished end closed. Smelt; an alloy of metal chippings in borax
solution, is placed into the join. Heating gently drives off the water – causing the borax salts to turn white, then heating very strongly melts it and seals the joint. The wire is removed, and the bell
acidified to remove the glaze from the borax salts and oxide from heating. Excess smelt is removed by scraping, before the process is repeated to seal the other end of the joint.
The bell is now
elliptical, and the joint has 2 thicknesses of metal. The joint is very carefully hammered flat in several lines. The bell is placed onto an oiled mandrel of its final shape and the back (opposite the joint)
"broken" or crushed in with a large soft hammer. The bell is slammed onto the mandrel several times to push it into approximately the right shape and then re-annealed. The outside of the bell is oiled and
repair plates used to smooth the bell with downward strokes.
The mandrel and bell are placed onto a lathe and spinning tools used to smooth the bell onto the mandrel along its length, so that it fits snugly. A
flat file is used to remove any inconsistencies along the surface – particularly the join, before the bell is sanded smooth and polished with a green scratchy household cloth.
Musical Instrument Repairs (MIR) in
Hales Owen was my next stop. A small 4th valve such as is normally found on echo cornets would have to be custom built, well beyond my skills at this point. Neil and Dave Toy and I experimented, until after much
bother, we used the 2nd valve of a tenor horn, turned through 90 degrees. The top port was filled with serrabend (a low melting metal alloy), the corresponding ferrule of the valve chamber removed, and the hole
patched. A variety of knuckles and bits of other scrap slides were used to connect the valve.
The long bell I had built was filled with serrabend, bent, cut short and a piece of a second echo bell built
by Andy while teaching me, was added to flare it to the correct width without adding much length. The length of the echo bell system is measured from the original valve block up to the apex of the echo chamber.
Echo bells tend to be very out of tune, so I added a tuning slide to mine. Placed underneath the echo bell, it helps to turn the bell around so that it can run parallel to the valve block, making it harder
to damage.
The addition of the 4th valve made the instrument very flat. Old cornets often have 2 tuning slides, the smaller of which was completely removed on the echo cornet and the curved end of the
slide soldered in. Any tuning problems are now my own fault!
Major joints were unsoldered prior to silver plating and the pieces polished separately, removing loose silver plate and any grease or dirt. The
cornet is re-assembled, wired up with 3 lengths of copper wire and washed with degreasing agent. Flash plating – dipping in a strong solution of silver/ potassium cyanide and wires connected to a variable current
source, gives a thin layer of silver on the instrument. A greater amount of silver is forced onto it using a second weaker solution for around 30 minutes. Rinsing, then polishing to a very high sheen with
T-cut and Jewellers rouge produces the instrument as you see it.
I built this instrument with the view to other people potentially using it for recitals and performances. If you would like to play the
instrument, then contact me. Also, the above is a much foreshortened version of the full text – if you would like a full copy, please contact me .
(the following are captions - the photos will be linked soon!)
Tabs fit above and below the other edge
Hammering the joint flat.
Sealing the joint
Spinning the bell
I did this!!
After flash plating – the white parts are burned areas and can be polished off later.
Echo bell before being joined on. |
