By Jim McCarthy | May 24, 2009
G’day again marimba enthusiasts! It’s been a busy couple of weeks. I finally have all the bars sanded back finely and polished. The final tuning and drilling of nodal holes is still to go, but that stage is still a while away yet – The frame needs to be calculated and at least partially built first.
The first step to calculation is to find where the node lines are on each individual bar using the “salt test”. Check out this video I made on youtube to show how this is done.
The photo below shows the complete set of “white note” bars correctly layed out and spaced against a flat wall. From this position I was able to find the “average” nodal line” accross the set of bars from the individual node lines found with the salt test above.
After a decent amount of measuring from this set up I was able to determine the exact frame dimensions needed to correctly support these bars. I won’t go over the whole process here as it’s a lengthy one, but it will of course be available in the building guide at www.makeamarimba.com once the whole instrument is finished and the guide written up.
As I had already designed the frame earlier in the year, I was able to begin on the frame as soon as these dimensions from the bars were obtained. Of course it takes a fair bit longer than it should as I’m taking extra time to take photos and write the process down as I go. Nevertheless, frame building is a welcome relief from working on the bars and goes a whole lot faster. This weekend I put in a couple of “half-days” work, and have cobbled together the basic structure of the frame – at least to the point where it can stand upright! – photo is to the left.
Hopefully there will be some time to make more progress during the next week.!