Shell construction

[Frank Godiva]

Factory tour video from the early 90's shows how a drum shell is made.

https://youtu.be/A4IZnd1uWwc

[Frank Godiva]

On to the wood: We visited the storeroom in which the stacks of wood are kept. Sonor drums are made from two, three, or four layers of three-ply wood, depending on the model. "It is most important," said Andreas, "that we keep control over the quality of the wood. So we buy the wood ourselves before it is made into three ply. We supply our subcontractor with the raw materials for making the plywood, and this way we guarantee the quality." The sheets of ply are stored in a cool room until four days before they are needed for the manufacture of drumshells, at which time they are taken into the much warmer room in which the shells are made. It is necessary for the wood to have time to become acclimatized to the temperature of the shell room, because when the shells are made, the pieces of ply are pressed together at a high temperature.

Wood is sensitive to temperature, and after the ply sections are cut to size, there is no room for error if the ply happens to expand or contract during the process. The inner pieces of ply are cut at an angle to give a diagonal join where the two ends meet. The outer layer is cut straight. The cut sheets are then placed between special rollers that coat them evenly with glue. The sheets that are to become the inside and outside of the drumshell are only coated on one side, while the ones that are to be sandwiched between them are coated on both sides. They are now ready to go into the shell machine.

There is a different machine for each diameter of shell size that Sonor makes. The machines are very sophisticated molds, for molding sheets of plywood together. There is a cylindrical outer casing, the inside of which is the same size as the outside of the required drumshell. The plywood sheets are bent by hand, so that they can be placed in the machine in the position in which they are to be pressed together. The outer layer goes in first, so that it rests against the inside of the "mold," then the next layer goes in with the join in a different place, and so on. When all the plywood is in place, an inside former is moved into position on the inside of the shell.

This former is not only heated, but is able to expand, thereby pressing the sheets of plywood together against the inside of the "mold." The drumshell is left under heat and pressure like this for about 12 minutes to allow it to "set." When it is taken out of the machine, the shell is as strong as any wooden shell of a given thickness could possibly be. It is also perfectly round. Each plywood sheet has been stuck, under pressure but free of tension (without being pulled), around the sheet next to it, so there is no overlap of any sheet against itself, and no possibility of the plies being out of true. In the case of wood finishes, the outer ply is the finish. It isn't a piece of veneer that is added on later. "It is all done at once," said RoIf proudly. "That's a specialty of Sonor."


In the Link Era every line shares the same parts, made by the same 190 people using the same equipment and techniques. So the high quality is the same across all lines, which makes it really difficult to cut costs and make a top of the line and a budget line side by side. Given that, Sonor certainly did have top of line kits, but they were not marketed that way back then.