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Ferguson's Paradox - the solution. Before leaving this subject, it is appropriate that one of Ferguson's orrery-type models should be mentioned, namely, the Mechanical Paradox. Although this was a straightforward piece of mechanical hardware, it owed its origin to a theological discussion. Ferguson related the story in a very long letter to a friend, the Rev Mr Cooper of Glass, Banffshire, written many years later. The original letter does not appear to have survived, but Henderson printed it in full from a copy said to be in Ferguson's own hand; it had previously been printed in the Horological Journal for 1858. The essence of the story was as follows.

One evening Ferguson went to a weekly gathering (probably a dining or drinking club), where one of the other people present, a watchmaker, 'began to hold forth against a Trinity of persons in the God-head, wondering at the impudence of the person who broached such an absurd doctrine'. CNC Cookbook: Astronomical Clock. Notes on Constructing an Orrery / Antikythera Mechanism I've always had a great interest in Astronomy, and I read with great interest recent articles about the Antikythera Mechanism, which was apparently an ancient orrery or simulator of motions of the heavenly bodies.

The machine, which was constructed circa 80 BC, could represent the motions of most heavenly bodies known in its time using a clockwork consisting of 37 gears. Differential Gear Mechanism Was Way Ahead of Its Time... The front dial would show the progression of the Sun and Moon through the Zodiac according to the ancient Egyptian calendar. The lower back dial gives the Metonic cycle, the Synodic cycle, and the Lunar year of 12 Synodic months. Later researchers determined that the device could show the motion of the visible planets through the Zodiac, as well as predict Solar and Lunar eclipses using the Saros scale.

It also displayed the Calippic scale. Front and Back of a Reconstructed Model of the Antykthera Mechanism. A Simple Lamina Flow Engine. A Simple Lamina Flow Engine I learnt of this engine, at an International Stirling Engine Conference, some years ago. In discussions with Jim Senft he referred to it a Lamina flow engine, in US patents it is usually called an acoustical heat engine. Jim's explanation seemed, at the time, clear however on my return to the UK it was evident I had not fully understood the theory since I failed to get an experimental engine to work! Subsequent research unearthed patents and other literature dating back to the 1950's, these clarified the working cycle of this type of engine. The schematic drawing, below, taken from a US patent granted in 1984 is for a heat pump. After a lot of experimentation I found the solution to turning this into a motor was simply a matter of applying heat to the end of the regenerator stack nearest the piston.

This is a very simple engine to make since it has, effectively, only one moving part--the piston. (Click on figure to view enlarged drawing) Piston & cylinder. Solar Heat Engines. Jerry E. Howell - Model Project Plans & Kits Home Page.