Complete Redesign of Drum Build Process

 The "traditional" California method for building taiko drums requires a jigsaw, a handheld belt sander, and a palm sander. This is efficient, just 3 power tools. However, the resulting drums may be too wide, slightly oval-headed, lopsided, heavy, and mushy sounding. My goal was to make drums that sound good, are easy to play, look good, and are easy to transport. This required coming up with a standard height and width. I also committed to making the drum as round and true as possible at every step, so that each step could rely on a consistent input. I also thought it would be helpful to have tools and jigs that reduce the need for highly skilled woodworkers, since we have none in our group. 

Here's my initial sketch of process design:

Note: "pig in shit" refers to my feeling of joy at the prospect of designing all these jigs.

New jigs were needed for step 3, 5, 9, 10, 11, 12-16. I also made jigs to build the pulleys for the lathe mill. Later on I replaced the step 3 jig with a jigsaw and a bed of 4 wheels to hold the barrel. I designed 5 versions of the recoop jig and built 3 iterations of the best design. I built 4 versions of gluing jig (step 9). I built 3 versions of the lathe mill so far (steps 12-16), and keep modifying the working model. Later I designed and built a head-stretching jig, and made a "fleshing board" for hide cleaning. I also made a steam box and bending form for making wheel felloes from oak. I tried 4 different ways of reinforcing the inner rim of drums. I learned how to 3-D print, useful for making the recoop jig and many other parts afterward. I learned how to use a planer, re-learned how to use a table saw, and learned how to use a jointer. Then I learned how to use chisels for mortise and tenoning, and how to sharpen plane blades and chisels. I learned to start noticing the internal grain of wood in order to select and plan use of lumber in ways that will avoid problems and improve workability and strength. I now know where everything is in my shop and how to maintain it, use it safely, and keep it accessible. I learned about dust collection and many other safety protocols I was previously unaware of. These are just a few things I learned or did that come to mind. Many other false starts and experiments occurred along the way.

Here are some of the tools/jigs currently in use in my process.

Step 1: at first we bought the wrong barrels and struggled to make use of them. Now we have a checklist and supplier for consistent high-quality barrels.

Step 2: at first we struggled to pull the nails to disassemble the barrel. Now I use a prybar vigorously and the barrel is disassembled in seconds.

Step 3: Instead of the jigs and extra work of cutting each stave to length on both ends, I use a method observed at Joe Bowes' shop. I carefully make a pencil line and just jigsaw along it, perpendicular to the outer surface of the barrel. The barrel is ratchet-strapped tight and rotated as needed on a wheel bed. The result is good enough for the following steps.

Step 4: Set aside a few narrow staves, which won't be needed for the smaller diameter. No calculations needed. 

Step 5: Recoop the staves on the table saw. About 1 hour total. This probably saves a huge amount of time and effort compared to using an electric hand plane, which I doubt I could successfully do. The hand plane method requires planing and checking the fit for each stave on both sides, with rework and adjustments as the barrel comes together. My jig is definitely is more practical for me than using a traditional "coopers jointer", the large plane on the left of this illustration. I don't know how fast a skilled cooper was, but I do know they spent years learning their craft.

Video of recooping one stave. Here is the core jig, 3D-printed. No moving parts. The jig can be 3D-printed to make a larger or smaller diameter drum, as desired. The only parameter needed for printing (using the model I created) is the desired diameter, e.g. 18". I'm quite pleased with this design, as it seems elegant, safe, requires no calculations during the work.

Prototype was wood and steel. This photo show how the stave is held with a long side exposed to be cut by the table saw's vertical blade.

Later I added a longer clamp handle as a safety feature so that I load and unload the stave without turning the table saw off.

After gluing, the new drum shell is shorter and narrower than the original barrel. Significantly, this drum shell matches our specified height and head diameter exactly. Here is a side by side view of before and after.

Here is a top view of before and after.

Step 6: Fitting the last piece. You just dry assemble staves using hoops (of the target diameter, which I made from spare hoops) until you have too many. 

Then you recoop that last stave, making it narrower until it fits. Looking around at the fit between each pair of staves, the abutting edges should look parallel. 

Step 9: Gluing the staves together into the shell. I designed this gluing jig to provide rigid circular support so that the drum is round. Also the jig helps make sure the drum is not skewed top to bottom. The glue can be used for about 30 minutes, which is not enough time for me to properly slather glue on all the staves, so Working alone, I have to do it in 3-4 sessions, placing dry staves in for clamping. This means it is more work for one person to do than with 4-5 helpers, because the glue setup and clamping assembly has to be done 4 times instead of once. And it takes 4-5 days instead of one day because of leaving the glue to dry overnight. Conversely, with helpers, it's all glued up in 30 minutes.

This jig uses ratchet straps and bar clamps. I have a more involved design for the gluing jig, which would apply more pressure, but it is not needed.

Step 10: Double check if the shell is round enough to be put on the lathe mill. I use a piece of plexiglass with a circle drawn on it. This one is round enough so that the outer part can be milled off on the lathe, without risking creating any thin, weak spots.

Step 11: Rim reinforcement. This is done to prevent the shell from losing chips if the ends split when the rim is hit with drumsticks. I tried 5 methods so far (plywood ring inserts, kerf-cut plywood with fiberglass, steam-bent wood, and re-using the cut-off ends of the staves ("casting" with slow-setting epoxy or, setting in paste epoxy). I found the last method easiest (stave ends with paste epoxy) although bent wood is strong and elegant so I might try it again. Not only do I want a strong reinforcement, I want a platform for mounting the shell on the lathe mill for subsequent steps. 

This shows the reinforcement pieces being glued in, recessed about 1/2 inch from the rim.

Step 12: "Profiling". This refers to making the shell smooth and round on the outside (not final sanding). After the re-cooping and removing a few staves then re-gluing, the barrel is somewhat irregular on the outside. (Mathematically speaking, we have gone from a 32 sided polygon inscribed in a circle to a 28 sided polygon, i.e. a worse approximation of a circle, which means the vertices are more acute.) 

I built a machine that can slowly turn the shell on it's long axis, with a power tool bit that can be applied from the side, on tracks. This is called a lathe-mill. The lathe part is built around a used treadmill ($50 on Craigslist), mounted on a moveable base and with step-down pulleys to make the barrel turn very slowly. Many design improvements are planned to make this smaller and simpler.

In the front of the lathe mill are two tracks, supporting the cutting tool as it can be moved left-right (X-axis) and forward-backward (Y-axis). I used CNC lathe materials but purposely decided to make the X and Y controls manual instead of Computer Numerically Controlled (CNC). 

This photo shows 2 of the 4 step-down pulleys I made from plywood, some with 3D-printed rims. Also the drum shell is mounted using adjustable brackets, so the axle can be perfectly centered.

This photo shows the tool position when profiling the body of the shell. Note the left side is profiled, and the right side is not yet done.

Here's a time-lapse video during part of the profiling. 

Step 15: Milling the "bullnose", rounded rim. Here's a closeup video of using the lathe-mill in step 14, milling the rim ends. In my final process, this step comes after profiling, but in the video, I tried doing the bullnose before the profiling. 

Step 16: mill the inside of the rim so it falls away from the drum head. Also not shown, there will be angle grinder work to round the hard angles of the reinforcement pieces after the shell comes off the lathe mill and before staining. Advance to 5:00 minutes in this video. again, this video shows this step being done before profiling and rim forming. I suppose I have not yet decided which order is best for these three operations on the lathe-mill, and it may depend on the roundness and thickness of the specific drum. 

Step 17: finish sanding. This is done on the lathe but without using the mill. An attachment could be built so the sander rides on the mill, but I'm not focused on that yet. The first step is with belt sander (this was my first drum, before the lathe became a lathe mill). Then  random orbital sander.

Here's a picture of a finished shell, before staining. This shell uses reinforcement method #1 (plywood discs).

More details to be added here about heading the drum.

The first stretch forms the head shape. 

The second and final stretch is about tone. Here's a video showing that the sound "sustains" for a few seconds when sufficiently tight.

Finally, tacks are added.

Two rows of tacks ensure the tone remains as desired (video), even after the ropes are removed.