Bowmen of Skelmersdale

Controlling Bow Vibration

Vibration is any periodic movement. Vibrational motion has a frequency and an amplitude. Frequency tells you how fast something is vibrating, and amplitude is how large the movement is. Generally it takes more energy to drive higher frequencies, so higher frequencies typically produce smaller vibrations in practice. Frequency is usually measured in cycles per second, or Hertz (Hz). For example, a clock pendulum which swings from one side to the other and back four times a second has a frequency of four cycles per second. In archery, frequencies range from a few Hertz to many thousand Hertz. (The human ear is sensitive to frequencies between about 25Hz and 20,000Hz - the higher the frequency, the higher the note you hear).

Controlling frequency

The frequency of a vibrating system depends on two main factors; the mass beingmoved and the force which returns it to its rest position. The restoring force is usually the strength or stiffness of a spring or, in archery, the bow limb or stabiliser rod. There are two simple rules to remember:

“A STIFFER or SHORTER spring gives a HIGHER frequency”

“A HEAVIER weight gives a LOWER frequency

So if we need to change a stabiliser vibration frequency, for example (we ll come to why later) either a stiffer rod or a lighter weight will increase the frequency and vice versa.

But what causes different frequencies and vibrations?

What bow behaviour needs controlling?

Bow  movement

Timing - When is movement important?

Time and Motion

Controlling bow displacement

Weight, Mass and Inertia

Static and Dynamic properties

The misnamed TFC

Controlling bow balance

Centre of Gravity

Finding the centre of gravity

Changing the balance using weight

Weights and Distances

Rods, weights and risers

Controlling bow vibration

Causes of Bow Vibration

Reducing Vibration - Damping

Bow Resonance

Tuned damping - more on TFC’s