There is a curious consistency about all four of Johann Bessler’s wheels, which is interesting and leads one to certain speculations about them. The details which follow are all taken from www.orffyre.com. This website is run by an old friend and correspondent of mine dating back to our earliest research days, and his information is accurate to date. From the afore-mentioned website:
(Bessler used the Leipzeg ell in his measurements - 1 ell = 22.3 inches
First wheel - Gera
Diameter = 4.6 feet
Thickness = about 4 inches
Speed = over 50 RPM unloaded
Rotation = uni-directional, required restraint when not in use
Axle = unknown
Sound = unknown
Power = unknown
* size in ell units: reported diameter = 2.5 ell = 4.6 feet; reported thickness = 4 Leipzeg inches = 3.7 inches *
Second wheel - Draschwitz
Diameter = 9.3 feet
Thickness = 6 inches
Speed = over 50 RPM unloaded
Rotation = uni-directional, required restraint when not in use
Axle = 6 inches diameter (probable diameter = 1/4 ell = 5.6 inches)
Sound = loud noise
Power = unknown
* size in ell units: reported diameter = 5 ell = 9.3 feet; probable thickness = 1/4 ell = 5.6 inches *
Third wheel - Merseburg
Diameter = 12 feet
Thickness = 11.15 inches
Speed = 40 RPM or more
Rotation = dual-directional, required gentle push start in either direction
Axle = 6 inches diameter (probable diameter = 1/4 ell = 5.6 inches)
Sound = banging noise at descending side of wheel
Power = estimates range from 20 Watts to 100 Watts
* size in ell units: reported diameter = 6 ells = 12 feet; reported thickness = 1/2 ell = 11.15 inches *
Fourth wheel - Kassel (Weissenstein Castle)
Diameter = 12 feet
Thickness = 18 inches
Speed = 26 RPM unloaded - 20 RPM under water screw load
Rotation = dual-directional, required gentle push start in either direction
Axle = 8 inches diameter (probable diameter = 1/3 ell = 7.4 inches)
Sound = about 8 bangs per revolution at descending side of wheel
Power = estimates range from 25 Watts to 125 Watts
* size in ell units: reported diameter = 6 ells = 12 feet; probable thickness = 3/4 ell = 16.7 inches
Bessler's apparent use of the Leipzig ell suggests he probably built his wheels to whole ell units and simple fractions thereof. The above diagram shows feet and inches derived from Leipzig ell conversions as listed in the data above.)
Ok, this me! The first thing to notice is that the first three wheels turned at a speed close to 50 rpm. Given the difference in the sizes of all three devices we might have expected a larger variation in their output. The fourth wheel, the Kassel wheel, the largest one tested, only rotated at 26 rpm, but given that it was designed to undergo an endurance test of several weeks, it would be surprising if Bessler had not designed it to turn at approximately half the speed of the others.
It seems likely that he increased the thickness of the wheel to compensate for the reduced weight-lifting capacity caused no doubt by reducing the speed or the actions of the internal mechanisms, thus slowing its rotation. Although we know little about the interior of the machines we can speculate on what alterations he might have made to the mechanisms within the fourth wheel, (the Kassel wheel) compared to those earlier ones to make turn more slowly.
In the most basic terms, we know that there were weights which must have moved about relative to the axle, and they had to be able to move from one place to another, and then return within one rotation. There seem to be limited potential variables, and I ruled out alterations in the mass of the weights. This leaves only a variation in the number of weights, and the distance they can move.
Again if we take into consideration the common rotational speed between the first three wheels, (Gera, Draschwitz and Merseburg) we might speculate that although the distances the weights moved might vary from wheel to wheel, perhaps their effect was controlled by the amount of torque each one could produce, and regardless of weight and mechanism size, perhaps no variation could occur, other than a reduction in top speed due to friction or work.
The first two wheels (Gera and Draschwitz) would begin to spin spontaneously as soon as a brake was released. We can infer that they were both in a state of permanent imbalance. I ignore suggestions that the wheel was stopped in a certain position in order to provide this effect. Besides Bessler stating that they had to be locked to stop them continuing to rotate, there is plenty of evidence from onlookers that he spoke the truth.
The second two wheels (Merseburg and Kassel) did not have this feature, but would begin to spin after being given a gentle nudge in the desired direction. They were capable of being started in either direction from which point they accelerated to their top speed. Clearly their two-way capacity led the two directions being balanced when stationary. This leads us to another question. If the first two wheels could attain a speed close 50 rpm, it seems surprising that the third wheel (Merseburg) also achieved the same speed in either direction. We can leave aside for the moment, the slow-turning Kassel wheel because we know it was designed to be slow.
One might think, as I did, that the two-way wheels had a second set of mechanisms designed to turn in the opposite direction, which allowed the wheel to be turned either way, but that might seem to create resistance in one mechanism being turned the wrong way which would either prevent the wheel turning, or lead to it turning more slowly. This apparently did not happen because the two-way Merseburg wheel was able to match the speed of the earlier one-way wheels. If a duplicate, but mirror image mechanism was installed within the Merseburg wheel, it was twice the thickness of the second wheel which would probably provide enough space for a double mechanism.
Given this problem perhaps he had found another way to allow just one set of mechanisms to cause rotation in either direction, this would have been the ideal solution, it would have simplified things. But we cannot work out how he might have done this until we know how his one way wheel worked.
So what is it that seemed to allow the first three wheels to reach around 50 rpm? Well we do know that several witnesses remarked on the great regularity of all the wheel’s evenness of rotation. There was no jerkiness nor bumpiness in each rotation. I presume there would be a limit to how fast the weights could move and this could be a limiting factor, regardless of size of any internal mechanisms. This could possibly be improved in these modern times, not just by reducing friction but by improving the configuration of the each mechanism. It would be a curious feat if one could improve the speed up-to 60rpm, measuring exactly one minute.
A single second was, historically, established by calculating the time it takes for the Earth to rotate once about its axis and dividing the time by the 86,400 seconds in each solar day, (60 x 60 x 24 = 86,400). Of course we have a much more precise method now, but in 1656, Dutch scientist Christiaan Huygens invented the first pendulum clock. It had a pendulum length of just under a meter which gave it a swing of one second, and an escapement that ticked every second. It was the first clock that could accurately keep time in seconds. By the 1730s, 80 years later, John Harrison's maritime chronometers could keep time accurate to within one second in 100 days.
But, if Christian Huygens pendulum clock had a pendulum length of just under a meter which gave it a swing of one second (39.27 inches), might that give us a hint at the length of levers in Bessler’s clock? Were they also just under a meter in length to time the wheel to close the 60 rpm? Allowing for friction that might have slowed the rotation to what it actually was.
I suspect that Bessler’s weighted levers had a much longer swing than Huygens’ 6 degree swing because it was generating force rather than measuring minutes, but given the work they did, they moved more slowly than any clock pendulum, so being close to 60 rpm may or may not be just coincidental.
JC
