I don’t think I could have been anything else but an engineer. Following my father’s example, I have a love for moving metal things – both the physical/mathematical aspects and the practical aspects, that apprentices pick up. Engineering systems have personalities all their own – the noisy excitement of a racing motorcycle, the brooding, contented hum of a nuclear powerplant or the clanging and crashing of a steam locomotive in its overrun, literally with fire in its belly. I have picked a few of books which inspired my love for mechanical engineering and you can view it on the Shepherd website.
Ruggedization comes in three flavours, apparently:
- Industrial Ruggedization
- Ingress Protection Ruggedization
- Stability Ruggedization
The reliability principles used to achieve the above three aims are simplification, by removing less reliable parts like irises, replaced with fixed aperture stops. These can be focused once and set in place. The other technique used is simply the removal of components. What is not there, cannot give trouble.
As regards Ingress Protection, lens assemblies are sealed with O-rings and RTV silicone to prevent the ingress of moisture and dust.
Stability Ruggedization is required in high vibration environments, among others. This is achieved by gluing all the lens elements in place, and using a clamping lock once focusing has been achieved.
When one studies the brochure, one sees that in this field, as in all engineering endeavors, compromises are made. To make a lens more “rugged” it has to be made less versatile.
Another Cold War Warrior with a dubious reputation is the Lockheed F-104 Starfighter. Foisted on the nations of NATO, it had a 32% accident rate in the Luftwaffe with 292 pilots killed. The Canadian experience was even worse, with a 50% accident rate. As far as is known, neither of the airforces mentioned ever took a shot at an enemy with these aircraft.
This is an example of mission unreliability at its worst.
We have said before on this site that some of the West’s weapons during the Cold War were not so hot, eg the 1954 vintage F-100 Super Sabre with a 39% accident rate, and 324 pilots killed. Although it could exceed Mach 1 in level flight it was nevertheless under powered at 10 000 lb static thrust. On landing it could get into a situation that the pilot could not rectify, and crash. See https://www.youtube.com/watch?v=Q2qqKwndFW0
If the angle of attack was slightly too much, lift was lost at the wingtips of the sharply swept wings. This moved the centre of pressure forward, lifting the nose even higher. The engine did not have enough thrust for the aircraft to climb out of trouble and so it would crash, the hapless pilot being unable to do anything about it. The contemporary British BAC Lightning fighter had a somewhat better flight envelope due to the 24 000 lb thrust from its two engines, mounted unusually one above the other. On the other hand, the British Swift and Javelin fighters were also poor performers.
F-100
Both sides in the Cold War tried to hide their mistakes. Only after the end of the Cold War has such information as we quote above has become available.
1. Gas Turbines for Cars
“Considering the sports car as a whole, it is in the power unit where we can expect the most striking changes in the next ten to fifteen years. The gas turbine must eventually replace the piston engine as the power unit of the family saloon. There is little doubt of this….” This quote is from the book The Sports Car, its Design and Performance, by Colin Campbell, MSc, AMIMechE. The book was published by Chapman and Hall of London, in 1956. It is a generally excellent work, with much that is still relevant with respect to chassis and engine design. But there are no gas turbine cars in production today, in the 21st Century. The only significant vehicle application of the gas turbine is in the American Abrams tank.2. Automatic Transmissions for Motor Vehicles
“……the prospects for large scale application of the ZF automatic transmission within Germany appear therefore, rather slender.” This quotation appears in the book Automatic Transmissions by R F Ansdale, AMIMechE, MSAE, published by Foulis in London in 1964. ZF today is not only one of the largest producers of automatic transmissions in Germany, but in the world.3. Engine Combustion Chambers
For decades in the last century, the highest form of engine combustion chamber was the hemispherical head, revered on both side of the Atlantic as the ultimate in engine design. One Chrysler engine was and is in fact known as the Chrysler Hemi. The English Jaguar XK120 engine was another classic hemispherical design, shown in the figure here below. The was much nonsense spoken in the motoring press at the time about why the hemispherical head was the best, including the statement that the hemisphere provided the best surface to volume ratio, meaning less heat was lost to the coolant and more heat was converted into power. In fact, the reason for the head shape was that it could accommodate bigger valves, which meant more oxygen into the combustion chamber than through smaller, vertically stacked valves. The other advantage was that the large included angle induced a measure of turbulence, always good for combustion. But conventional vertical valve heads also offered turbulence because of “squish” areas, which were areas where the piston almost touched the head allowing gas to be squished out in highly turbulent streams. An interesting mathematical exercise is to determine how many valves, if mounted vertically, will maximise the area available for induction. In other words, how many circles can one fit inside a circle representing the cylinder bore, to maximise the area? All circles must touch the outer diameter, and there still has to be place for a spark plug and/or possibly a fuel injector nozzle. The answer is four or five, with almost identical total areas in both cases. Some Yamaha motorcycles have gone the five-valve route, with three inlets and two exhausts. (The pressure to get air into the cylinder is less than the gas pressure to get the exhaust out, even if the engine is supercharged, and hence inlet valves are often bigger than exhaust valves, or more valves are used). The alternative to the large valves at a high included angle was to have more than two valves per cylinder. But Philip Smith in his book, The Design and Tuning of Competition Engines, also published by Foulis in 1963, stated that four valves per cylinder was not a good idea because of extra friction leading to induction losses. Then came Honda with its four-valve-per-cylinder motorcycle engines. The small, light valves allowed very high RPM and a greater area for induction, but still with high included valve angles. Thus, the reign of the hemispherical head started to be precarious. Clive Duckworth of Cosworth fame, offered the coup de grace with engines with four valve heads and narrow included angles. These engines developed more power, size for size and with equivalent compression ratios, than hemispherical engines did. Such Duckworth-type heads are now common even in family saloon cars. Hemi RIP.
Jaguar Cylinder Head showing two large valves at a large included angle
Cosworth engine cutaway showing four valve heads at shallow angle
