Cutting the bars to length

With my bench mounted mitre saw I now cut the 50cm karagatch lengths down to their new sizes.

This meant that each bar was 5cm in width, 2.3 or 2.4cm in depth and ranged from 23cm to 39cm in length.  Here is the table I worked to;



SOPRANO marimba C4 D4 E4 F4 F#4 G4 A4
Frequency 261.60 293.60 329.60 349.20 369.90 392.00 440.00
F4 (4 x Fundamental) 1046.40 1174.40 1318.40 1396.80 1479.60 1568.00 1760.00
F9.8 (9.8 x fundamental) 2563.68 2877.28 3230.08 3422.16 3625.02 3841.60 4312.00
Bar width cm 5.00 5.00 5.00 5.00 5.00 5.00 5.00
Bar thickness mm 22.00 22.00 22.00 22.00 22.00 22.00 22.00
Bar length cm 39.00 38.00 37.00 36.00 35.00 34.00 33.00
Nodes cm from ends 8.78 8.55 8.33 8.10 7.88 7.65 7.43


B4 C5 D5 E5 F5 F#5 G5 A5 B5 C6
493.80 523.20 587.30 659.20 698.40 739.90 783.90 880.00 987.70 1046.50
1975.20 2092.80 2349.20 2636.80 2793.60 2959.60 3135.60 3520.00 3950.80 4186.00
4839.24 5127.36 5755.54 6460.16 6844.32 7251.02 7682.22 8624.00 9679.46 10255.70
5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00
22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00 22.00
32.00 31.00 30.00 29.00 28.00 27.00 26.00 25.00 24.00 23.00
7.20 6.98 6.75 6.53 6.30 6.08 5.85 5.63 5.40 5.18

The frequencies in the table are the fundamental frequencies plus the most significant harmonics that are found at 4 times the fundamental and 9.8 times the fundamental.  I hoped I might 'triple tune' my keys, but at this stage I will accept 'in tune' with the fundamental frequency!

I transferred most of this information to the templates before using them to guide me in cutting the keys.  Once I had finished cutting all 17 keys I gave them all a tap in sequence going up the scale to see how much work I needed to do to get them in tune.  I had hoped that by some amazing miracle they might all be perfectly in tune with each other but that was definitely not the case!!

As you can see from my photograph I had also made the rails by this stage.  This was another use of the templates.  They allowed me to gauge the gap between the bars and create rails that would fall under the nodes of each of the bars.  I also bought vine screws from the market and ran cord through these to provide a sprung surface on which to lay the keys.  Once I had got this far the next task was to drill lateral holes through the bars at the nodes so that secondary cords could be passed through the keys on each side to hold them on the rails.  Now I really felt like I was making progress and went to bed happy that night.




Ps.  The electric sander in the workshop is not mine and to the best of my knowledge it doesn't work anyway.  Since I took this picture I have been given a new space to work in where there I do all my routing and sanding by hand to fine tune the bars.

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