DRUM BUILDING

 

 

Drum Making Materials and Other Taiko Supplies:

                      

 

Taiko Drum Building Using Coil Spring Compressors:

Kaze Daiko is in a unique position to develop new drum building techniques. Each member owns their own drum and hence when they leave the group they take their drums with them. When new members are added, the group works together to build drums for them.

 

Use of coil spring compressors (see note 1) to stretch the hides was developed by a parent of one of our troupe members in late 2008. In the picture of the drum below the coil spring compressors are the black bolt with the two silver hooks. This process allows for both skins to be stretched at one time, thereby reducing in half the time to do this part of the drum building process.  Because both sides are stretched at the same time, the tension in both ends will just about the same and hence the sounds will be the same. We currently are using a two stretch process. The first stretch is to form the head which is allowed to dry. This drying strengthens the mimi for the final stretch.

 

A benefit is that this process does not require an elaborate fixture as we had used...no more hydraulic jack, 4 x 4's and plywood sheets.

 

Drum building is more of a craft since the materials used are not consistent. Hides are not consistent thickness of itself as on side of the same hide will be thicker than the other side. Wine barrel staves are  not consistent in dimensions nor material properties.

 

The goal for stretching the hide is to get it as tight as possible without tearing the mimi and thereby get the highest pitch possible. To achieve this we use processes to first improve the capability of the mimi to carry the stretching load and second reduce loss of stretching load, which increases load directly stretching the skin over the barrel end.

 

Increase amount of load that the mimi can take:

  1. More dowels is better as it spreads the stretching load over more points. We originally started with 8 dowels, but changed to 10. This gives us 20% more load capacity overall....not so fast my friend..This justs adds two more places to apply the same load!

  2. For each dowel we changed from two holes to four. At each mimi this doubled the load carrying capacity of the skin. Most drum builders use four.

  3. The goal is to have the lowest load per length of mimi (wrapped portion around the dowel).  For example if you had mimi that had wrapped length A+B=8 inches vs A+B=4 inches and applied the same load to each, the 8 inch wrapped length would have have 50% of load per inch as the 4" wrapped length...and hence half the stress. This would reduce the chance of tearing the mimi during pulling. See wrapped length A & B in following picture.  The 100 lbs load is hypothical.

  4. When you make the holes in the skin for dowels, we don't recommend using slits. He use 1/2" leather punches to make the holes. From engineering we know that the end of the slit is like a crack and is subject to tearing. Did you know that you can use a hole at the end of a crack to stop it from continuing?

 

Some additional analysis of how the pulling load is transferred from the rope to the mimi can significantly increase the load capacity. Also there may be different ways to fix the rope to the dowel (non traditional) to change the load paths somewhat.

 

Reduction of load loss can be achieved through several techniques:

  1. A radius is added to the ends of the drum allowing the skin to pull over the ends more easily.

  2. This end radius is waxed to reduce the friction to allow the skin to pull over the ends with less load loss.

  3. The first stretch forms the skins over ends of the drum. The skins are allowed to dry which form a hard (dried) band around the drum. During the stretching process this hard band of skin around the circumference is pulled using the dowels (see the picture below), but is restrained by the diameter of the drum (which gets larger). Hence a significant portion of load is used to stretch this hard circumferential band of dried hide. The pulling load is wasted as it is not used to stretch the skin over the end. In order to mitigate this loss we have put vinyl sheet under the mimi. We recently incorporated this process change.  Can you see the grey tape holding it down? For the second (final) stretch we will remove this vinyl which has formed a gap. This gap will allow the circumferential band of dried hide to be pulled over the increasing diameter of the drum. This should allow more of the pulling load to go directly into the skin. 

We were able to compare drums that we have recently made with other groups purchased drums and the sound is comparable. We believe with some additional process improvements that we can get higher pitched drums with pitch equal on both sides!

 

Of note: We had thought that the tension in the skin would cause the holes for the tacks to become oblong over time. When we remove the original skin from the drum the tack holes have not become oval.  This suggests that there is a significant friction force between the skin and barrel even with the sloping sides of the barrel. This can be explained by the skin shrinkage around the outside of the barrel. This implies that a single row of tacks would hold the skin satisfactorily...though we do love the look of two rows of tacks.

 

For the second stretch we use the "Second Soak"process that Stanford Taiko uses. See Stanford Taiko Drum Building and then stretch and tack down.

 

Notes:

 1.) So what is a coil spring compressor? Your car most likely has four coil springs in its suspension as part of the "strut assembly". The compressors are used to compress the spring when the strut assembly is being serviced. So coil spring compressors come in many different configurations, but are all basically the same a fully threaded bolt/nut with hooks on both ends.

 

 

We are using pieces of carpet between the coil spring compressors and the barrel. We use 1/2" diameter steel dowels and braided nylon ropes.

 

Finished drum: To hear the sound follow this link

 

 

For making the skin "round" we made a plexi-glass template with holes for marking dowel hole locations.

 

We do not reinforce the ends as we believe the compressive load of the stretched hide will hold the ends together. We have never had a failure of the drum ends.

 

Oval Shaped Drums:

Barrel staves seem to come in two thicknesses, 3/4" and 1". In last couple of years barrel that we have received have had 1" thick staves. The ends of these drums are pretty round. In the last year the last three barrels that we have received have had 3/4" thick staves.  We have noted some ovaling of the ends when gluing the staves. We have devised a simple fixture to hold the barrel to a rounder shape while the glue is drying.

 

We believe that 1" thick staves hold a rounder shape than the 3/4" thick stave. A drum made with 3/4" thick staves will be 25% lighter than with 1" staves, which for our chudaiko weights would be 30 pounds versus 40 pounds.  So there appears to be a trade-off between tendency to oval versus weight.

 

 
 

Last updated: 23 May 2011 07:26:51 PM