Why five mechanisms?
Bessler was adamant that five mechanisms were necessary to the successful operation of his wheel and the reason is this. The most useful part of the ‘power arc’ described earlier measures 90 degrees, because if the pendulum is expanded before three o’clock it does not contribute its maximum possible torque until three o’clock is reached. If the pendulum is retracted before six o’clock it will lose some of the torque available. Time must be allowed for the expansion and retraction of the pendulum to take place at either end of the limits of this portion of the arc. It is also clear that with four mechanisms there can only ever be one mechanism operating within the ‘power arc’ at anytime. With five mechanisms there will sometimes be two
of them within the power arc.
In the upper two adjacent drawings there are five black pendulums with bobs at the end of each one. They show that there is always at least one pendulum and sometimes two, in the red power arc, which runs from three o’clock to six o’clock as before. The four blue pendulums in the lower two drawings, show that there can only ever be one pendulum in the power arc at any time. Three pendulums provide insufficient impulse to rotate the wheel enough to engage the next one. Bessler suggests that an odd number of mechanisms is necessary and these drawings demonstrate why.
Seven or even nine mechanisms might have been fitted inside the large Kassel wheel which could explain the reason for describing the sound of “about eight weights which could be heard...” . The word “about” has always conveyed to me the uncertainty experienced by the witness of knowing exactly how many sounds he could accurately establish hearing. There must have been other sounds coming perhaps from the backwards turning mechanisms which would tend to confuse the senses.
