Ocean Drum Extension Kit

In my frame drum extension series, we have so far built a bendir extension and a daf extension. In this instructable now, we will build a flexible and removable ocean drum extension. An ocean drum (or sea drum, as it is sometimes called) is a two sided drum filled with metal balls. If you hold the drum horizontally and make the balls slowly roll over the drum head from one side to the other, you can imitate the sound of breaking waves. That’s why it is called sea drum or ocean drum. Holding the drum vertically, the balls can also serve as some kind of shaker alternative, e.g. when giving a steady pulse to the drum with your foot in sitting position during playing.

Of course, we cannot make a one sided frame drum two sided! But we can add a cover to the back of the drum, so as to be able to temporarily fill it. As cover, I used an acoustic cloth, a sound transparent fabric, which is usually used for loud speakers. The goal was to have a back cover, but minimal sound disturbance or sound reflections from it.

All in all, we need the following material:

  • A frame drum
  • 2.5mm wire (so as to create a stable ring with it)
  • Acoustic cloth as back cover (which will be mounted on the ring)
  • Some 3D-printed parts (so as to be able to mount the ring on the drum)
  • Four 2mm*10mm self-tapping screws
  • Drum filling / ocean sand: Some metal balls, wooden balls, etc.

Most commercial ocean drums seem to be filled with metal balls with a diameter of 4mm. 300 balls seem to be some kind of a minimum.

For testing reason, I have also ordered 200 wooden balls, 6mm, without drill holes. And I have to say: I like them even more than the metal balls! They are fare less aggressive on the synthetic drum head and give a warm and rich sound. But just test what you like! Chickpeas also do work as filling. But they are loud, too, and do not roll as nicely as perfectly manufactured wooden or metal balls. All in all, keep in mind when choosing fill material: Due to the construction of the mounting clamps, there is always a small 2mm gap between the drum and the back cover. Material smaller than 2mm is therefore prone to be lost during transportation and playing.

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Step 1: Printing the Parts

The following instructions again presume a 22” Remo frame drum with Renaissance head. If you have a drum with different dimensions, you need to adjust the attached Fusion360-CAD-file first (OceanDrumExtensionKitV2.f3d).

Start with printing the clamps for the drum (MountingDrum.stl). We need four of them. It is important to print them in a lying position due to the force that will be later applied to the part by clamping them on the drum. The parts need to be printed with support material. To improve bed adhesion, especially when printing with ABS, it is also important to add a brim. Cura slicer settings: infill “50%”, infill type “grid”, wall line count “3” (i.e. print it with 3 outer walls). Moreover, I printed the parts with a support blocker for the small screw hole, see the Cura forum for more details on how to use the so called "support blocker tool".

Next print the mountings for the rings (MountingRing.stl). We need for of them, too. They can be printed without a brim, but need support material. Infill “50%”, infill type “grid”, wall line count “3”.

Finally check the printed parts and get rid off any sharp edges and corners. For this task, I usually use a needle file on which I have fixed a piece of 120 grit sand paper using double-sided adhesive tape.

Step 2: Back Cover Ring Creation

Place the drum in front of you and mount the four clamps: One in 12 o’clock position, one in 3 o’clock position, one in 6 o’clock position and one in 9 o’clock position. Fix them with tape to prevent them from moving. Before starting to work with the wire, if protected the drum head with some towels. You never know. Now start to form a ring with the wire on the inside of the drum. Ideally, the gap between the wire and the drum is always 2mm. When finished, check carefully for an equal, 2mm gap on the whole ring and mark the beginning and end of the ring on the wire with a pen. On the marks, cut the wire with a wire cutter, and solder both ends together.

[UPDATE: In the long run, soft-soldering did not work for me. The ring broke. Since I could not try out to hard-solder the ring, I now use a 15mm long metal sleeve / threaded sleeve and epoxy glue to close the ring, see picture.]

Step 3: Cloth Mounting and Stretching

It’s time for mounting the acoustic cloth on the ring. Lay the cloth on a table and place the ring on it. Cut out a circle that is about 4 cm bigger than the ring. Use fixing pins to get the cloth into position and to stretch it a little bit. Do not place the fixing pins directly next to the wire but in a distance of 1.5-2cm. We need the space for the sewing foot of the sewing machine. For sewing, I used a Jersey needle to prevent damage to the fabric. As sewing foot, I took the foot normally used to sew in zippers. It glides nicely on the inside of the ring, and the seam’s distance to the wire is quite low. Finally remove the fixing pins and cut off the excess fabric.

Step 4: Final Assembly

Place the ring back into the drum mountings. Before putting the screws in, I have put fabric glue on the spots, where the screws will punch through the cloth. This should prevent runners in the cloth. When the glue is dry, put on the ring mountings / cappings and bolt them down tightly. Remove the towels from the drum and put in your filling. When demounting the back cover, I do it step by step by moving one of the clamps up by 1 cm. Then I go on with the next clamp near by, all the way round until it is loose. This procedure prevents the ring from getting bent too much.

Step 5: Enjoy!

You have filled the drum with the material of your choice? Remount the back cover and enjoy playing your new ocean drum! And by the way: If you found this instructable inspiring and life-enhancing for you, you can also buy me a coffee :-).

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