FATIGUE AND WEAR IN A JOURNAL BEARING (during start-up and boundary lubrication)When two bodies are pressed together contact stresses occur. The results of the work done in this area are due to Hertz and are referred to as Hertzian stresses. Two special cases of hertzian stresses are: contacting spheres and contacting cylinders. An example of contacting spheres would be a single row ball bearing, with a single ball contacting the inner surface of the inner or outer race. An example of...
In a good camshaft design the cam profile is but one half of the story. Lifting the valve off its seat and then opening fully before closing it again and dropping it gently back onto its seat requires a lot of careful mathematics and, executed well, should give the maximum valve area opening period for the minimum of forces involved. But just as much as efficient inlet and exhaust cam profiles are critical to any high performance engine, the timing of their opening and closing in relation...
The use of polymer coatings in racing engines has been widespread for many years, but is to some extent being displaced by the newer generation of coatings such as titanium nitride, chromium nitride and DLC as examples. In a lot of circumstances the newer coatings are an improvement, but the coatings rely on the fact that there will be no significant deformation of the coated surface, otherwise the thin coating, which itself is brittle in comparison to the underlying substrate, can craze...
Last month, we looked further into the use of titanium for con rods and this month we look briefly into the use of steel, which remains in many cases the material of choice for con rods. There are far more manufacturers of con rods who offer steel rods than any other material. Titanium is definitely on the increase, and possibly the time will come where steel becomes a ‘minority’ material choice. Some of the reason for steel remaining popular is the price of the raw material...
We should all be very familiar with the primary functions of a crankshaft, namely as part of the mechanism which converts reciprocating motion into rotary motion, and to transmit torque to the outside world, where it might drive a gearbox, a generator or other piece of equipment. What a great many crankshaft designs also do is to provide lubrication channels which allow the passage of oil to the big end bearings, and possibly thereafter to the small end of the connecting rod. Many years...