How a Timpani is Made
The road to finishing a timpani kettle
What is the kettle made of?
The timpani kettle is made of 100% copper. Recently in Japan, copper is used to make 10-yen coins. 95% of the coin is made of copper, while the remaining materials used are zinc mixed with tin. FRP (fiber reinforced plastic) and aluminum is also used to make some kettles.
Copper can be easily stretched out and shaped to create a timpani shell with deep sound and long sustain, and has been used for timpani kettles since the past. However, the method of manufacturing the kettle has changed completely over time.
Cutting and rounding the kettle
First of all, a flat copper plate several millimeters thick is fitted to the size of the kettle to be made and cut in a round shape. When cutting the shell while rotating it, a small hole is formed in the center, which becomes the bottom. This hole is later enlarged to shape the shell.
Next comes the process of metal spinning. The flat copper plate and round mold are spun around and around vertically on a large machine, and a roller is used to press the copper plate onto the mold. The plate eventually assumes a round shape.
Once the plate has started to take shape, it is removed from the machine and annealed. This is necessary in order to avoid wrinkles and cracks in the plate, as copper work hardens quickly.
What is "work hardening"?
Although copper is a rather soft material, it transforms into a harder substance once it is machined. This is called "work hardening".
For instance, if we were to bend and unbend a wire over and over again, it would eventually break. Also, when you keep chewing a piece of gum for a while, it gets harder; and the more you slice flour or buckwheat dough, the firmer the noodles become. When you stress a material by processing or machining it, work hardening occurs. Because of this, the material must be heated with flame to soften it during processing.
After this, the shape will be worked further, as the surface is gently smoothed out, and the rim along the edge is cut to measurements after the edge has been pulled out. Everything up to this point is what we call the metal spinning process.
From annealing to inner face polishing and coating
Once the kettle has been formed, it is annealed again, and the form is stabilized by releasing the force that causes it to return to its previous shape. When the shell is heated, it reacts with the oxygen in the air, creating an oxidation layer, and causing a mottled color on the surface. However, this mottling can be cleanly removed by polishing. The shell is then buffed to create a smoothly polished surface.
Now, it is time for polishing. When a timpani is played, the air inside the kettle vibrates as well. Polishing the inside of the kettle to make it smooth gives the timpani a crisp sound with sharp attack.
Next, the kettle is cleaned. A jig is attached to the hole at the round bottom of the kettle, and the kettle is hung and dipped into a vat of water for washing. Air is let into the inside and the kettle is quickly rocked back and forth to bring out bubbles.
After this, any moisture on the surface is wiped off, and the kettle is hung up to dry in the air. Once is dry, it is coated, using a clear coat in a dust-proof environment. At last-our shiny new kettle is complete!
Why is the kettle hammered to make it harder?
On some kettles called hammered kettles, a hammer is used to beat and harden the entire surface. Each blow is carefully made by hand to make the surface harder.
(Note: some models are hammered both by hand and by machine.)
Hardening the material of a timpani kettle makes the pitch sound even more clear. Hammering the kettle evenly is very exacting work. Over a period of ten years of hammering the kettle directly using the hammer face so that no odd marks remain, the hammer face ends up getting noticeably shorter.
Assembly time! The heart of the timpani goes behind the base
The last part of manufacturing a timpani is assembly. The rear side of the base, or in other words the part that is closest to the floor is flipped over, and tension rods are passed through the round center hole and attached to the kettle in a radial pattern. This is what we consider to be the heart of the timpani, as this part plays the role of changing the pitch.
The relationship between tension rods and pitch
The tension rods work together with the tuning rods to change the tension of the head. Tightening the angle of the tension rods will pull the head, which makes the higher pitches in the tonal range of the instrument sound more clear. However, this makes the pedal feel heavier. For this reason, we make fine adjustments to the tension rod angle, considering both sound and operability.
The balance on all eight tension rods is adjusted precisely to make the head tension uniform. When even one tension rod is out of adjustment, the pedal will not move smoothly when it is depressed, which feels strange when playing.
After adjusting the rear, the timpani is turned over and the wire leading to the tuning indicator is connected. As with the brake on a bicycle, this wire runs through the timpani and is pulled when the pedal is depressed, which changes the reading on the indicator.
The ball you see below the pedal is used to tighten the head. On the completed timpani, the head tension and the force from the spring inside the pedal will pull against each other; but since we have not attached the head yet, a ball is inserted below the pedal, which we will remove once the head has been attached. This works as a substitute for head tension.
The kettle is set inside, and once the head is attached, the timpani is finished.
Finally, the tuning
To finish, we do the important job of tuning the timpani. Using a tuning meter to tap around the edge of the timpani head with one hand, we check to see whether the drum makes the same sound wherever it is struck. The lowest pitch is checked without pressing the pedal, and if it is incorrect, the base is flipped over once more and the tension rods are readjusted.