We Australians excel at remembering and celebrating our sporting heroes, from cricketers to particularly successful race horses, but are not so good at celebrating the great people who helped build our civilization, particularly when those builders are Australian. Today, I want to celebrate the birthday of a revolutionary Australian engineer, A. G. M. Michell.
Innovator and Inventor
Anthony George Maldon Michell was an Australian engineer who made enormous contributions to a wide range of engineering sciences, from publishing the seminal work on structural optimization, to the invention of the Fluid-film Thrust Bearing. Michell’s inventions operate quietly in the background, but have made a huge impact on our every-day lives.
Early life and education
Michell was born in London in 1870 while his parents were visiting from Australia, but grew up and attended primary school in Victoria. He returned to England to attend Grammar school and spent a year studying at Cambridge. He returned to Australia in 1889 to study engineering at the University of Melbourne.
Bearing the load
Of all of Michell’s inventions and innovations, the one that has had the greatest impact is the Michell Bearing, or Fluid-film Thrust Bearing, which he patented in 1905. Michell created a bearing with tilting load-pads that would maintain a thin film of lubricating oil between the metal surfaces. He mathematically derived the pressure distribution in the oil so that the pivot for the tilting pads could be optimally placed to ensure that the pads tilt automatically, under varying load, to the most efficient geometry. At the start of the 20th century, this bearing was revolutionary (pun intended). It could sustain enormous thrust loads with minimal wear and without overheating, while being only one tenth of the size of the bearings it replaced.
The low-friction of Michell’s bearings made them much more efficient. Within a decade they had found almost universal application in generators and ships’ thrust blocks. There was some reluctance by the British to adopt Michell Bearings in their ships, until the discovery that the German Navy were using Michell Bearings in their WWI U-Boats, which gave the U-Boats a range and speed that surprised the Royal Navy.
As well as being efficient, the low-wear of Michell Bearings mean they need little maintenance and are very reliable. A Michell Bearing installed at the Holtwood Hydroelectric Power Plant in Pennsylvania in 1912, supporting 165 tonnes of turbine and 40 tonnes of water pressure, is still in operation today. That bearing has been estimated to have a maintenance-free life of over 1000 years.
Michell Bearings, for their strength, efficiency, and reliability are still used on all large ships, power plants and turbines today.
Going with the flow
Another of Michell’s brilliant inventions is the Cross-flow turbine, which has found applications in hydroelectricity generation. This turbine is not used as often as the more common Kaplan, Francis, or Pelton type turbines because it has a lower maximum efficiency. However, cross-flow turbines have a much better efficiency than any of these three when operating at partial load. This gives cross-flow turbines an advantage in small-scale hydroelectric power generation, in situations, such as small rivers, where water flow and pressure can vary widely over the year. Cross-flow turbines are also easier to build, are easier to maintain, and are partially self-cleaning due to the way in which water flows through the blades of the rotor.
Other innovations
Michell’s other notable innovations include the first published work on structural optimization. Unfortunately, Michell was ahead of his time and this field of research did not gain momentum until computers became a useful research tool some half-century later.
Michell also designed a crankless engine that drew on his work on the thrust bearing and used slipper-blocks on a slanted wobble-plate to convert the reciprocal motion of the pistons into rotary motion of an output shaft. By eliminating the crankshaft, connecting rods, and associated bearings, Michell’s crankless engines could be lighter and more compact than conventional automotive and stationary engines. Proper dynamic design of the wobble-plate also made the engine very low in vibration. Despite successful demonstrations, improved efficiency, and several licensed derivatives, the crankless engine failed to gain wide-spread acceptance and the company formed to produce and market the technology was placed into receivership.
Later life
Michell was elected a Fellow of the Royal Society and received several prestigious awards including the Kernot Memorial Medal for distinguished engineering achievement in Australia, and the James Watt International Medal. He continued to make major contributions in engineering research until his death in 1959 at the age of 88.
When asked to list great Australian inventions, most Australians might include the Hills Hoist, Vegemite, the Victa lawnmower, and not much else. Michell, and his bearings that transformed movement and power in the 20th century, deserve to be amongst the first things a proud Australian should include on their list.
David Gozzard 