Investigation of Long Bow Vibrations
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Typ
Examensarbete för masterexamen
Program
Sound and vibration (MPSOV), MSc
Publicerad
2021
Författare
Mosawi, Nasrin
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The work was about mapping which vibrations occur in bows and how they could affect
accuracy. The work was carried out during the Corona pandemic, which meant
limited resources for experimental measurement and the experiments were done in
an office environment and not in the field. If possible, it was important to find applicable
theory behind all experimental results. One goal was to measure with simple
means and really understand what was to be measured and how. All experiments
and measurements were done on a recurve bow. The measurements therefore began
with recording sound using a microphone. Accelerometers were used for further
measurements. To increase the understanding of these, a known source of vibration
was needed. Thereby, a loudspeaker was modified with the possibility of attaching
accelerometers in the middle of the diaphragm. The loudspeaker was powered by a
signal generator via a power amplifier. A PC oscilloscope was used to record and
interpret signals from the accelerometers. Three different oscillations were recorded,
one elemental transverse oscillation of the string, the bending oscillation of the limbs
and the third was transverse oscillation laterally with the string and arrow together.
All three had a period that was much longer than the shooting. It was then considered
important to be able to measure to describe the movement of the handle
during the shooting process, which is specific to each combination archer and bow.
Experiments on this were done with available equipment that was not sufficient due
to too slow serial communication. After creating a theoretical model of the frame,
”cushioning pads” could be shown to have a positive but rather small effect.
Beskrivning
Ämne/nyckelord
Long bow , accelerometer , transverse oscillation , limb vibration , damping eigenfrequensis , loudspeaker as vibrator