A few months ago, in May I believe, we looked at a variable duration cam made in two pieces. While this was a novel approach to optimising the airflow into an engine over a range of conditions, reader Reine Gustafson of AGAP in Sweden contacted me recently about another cam design idea. This too consists of more than one piece and, as you will see, is simplicity itself.
Now there can’t be a cam designer or engine builder who hasn’t been confronted with this problem at times and
The surface of a camshaft or its associated follower can fail in a number of ways. Adhesive wear leading to abrasive wear, and corrosive wear, are perhaps the most common but another type of wear - surface fatigue - is sometimes perhaps harder to understand.
Adhesive/abrasive wear tend to be lubricant-based issues. Poor lubrication or an incorrectly specified lubricant - it amounts to the same thing - will cause the oil film to break down under extreme loads, producing metal-to-metal contact causing abrasive wear (scuffing Read more…
The complex interaction of components that represents the valvetrain operates in some of the most difficult tribological circumstances. With rapid changes in instantaneous direction between adjacent parts, and high contact stresses, the challenge of maximising the output of the engine while maintaining an acceptable level of reliability has never been more onerous.
While it is true that the vast majority of camshaft wear takes place during cold start and warm-up, when the temperature of the oil is less than 60 C, the durability and performance of the valvetrain can still be a major consideration when the engine is operating at its normal working temperature. At the most basic level it’s all about friction and its inevitable consequence - wear. Read more…
One of the biggest issues with any machine tool, camshaft grinders included, is that of axis backlash. Defined as the loss of motion when the machine’s axis, either rotational or linear, reverses, it can have a major influence on the precision of the component being made.
With camshaft lobes needing to be ground to accuracies of +/- 6 microns or better, the backlash in the machine is therefore of critical importance. The result of loose or worn components in the Read more…
Given enough time in engine research and development, only someone who is very blinkered could say they’ve never come across something a bit, shall we say, unusual. Devices to increase fuel economy substantially tend to be the norm here. Now and again I get a full-size drawing of an engine concept, and invariably the sender is looking for introductions or funding. This month, however, I have a camshaft, and for once its owner/designer has sent me the actual component, which looks interesting. Read more…
If you talk to anyone in the camshaft manufacturing business, it isn’t very long before the name of Landis crops up. Old timers might reflect fondly on such machines as the Berco RAC1500 cam grinder - “The best manual cam grinder in the business” or be rather less complementary about the Storm Vulcan machine going back into the 1950s, but the one machine that everyone agrees upon, to the point where it is now assuming the position of an icon in the camshaft manufacturing business, is the Landis 3L. Read more…
Perhaps the most noticeable trend in lubricant technology over the last 30 years or so is the movement towards lower viscosity oils. The relentless drive for greater efficiency and hence higher power has led to developments where in the past claims of an increase of up to 25kW have been made in a Formula One engine just by changing the oil. Whether you believe this to be true or not is immaterial but research over the years has shown that reducing the viscosity of the oil can lead to friction reduction in the piston ring pack and the bearings. However with its altogether much Read more…
Invariably measured in crankshaft degrees, the duration of any camshaft is generally accepted to be the number of degrees the valve is lifted off its seat to the instant that it shuts again. Ideally it should open instantaneously to its maximum lift and then remain open until it would be closed again equally quickly. This would produce a square shaped valve motion diagram and cause the maximum amount of charge air or exhaust gas to flow. In real life however, the opening and closing are constrained by the laws of physics and valves have to be carefully lifted off their seat, accelerated to maximum Read more…
It always surprises me how often people approach a recognised expert in a particular subject and yet fail to act on their advice. We can all think of occasions when say, consulting a solicitor or lawyer, since theirs is a world of uncertainty and risk, it might be reasonable to seek alternate council. But in seeking advice from a reputable camshaft supplier it seems silly to ignore their advice and go for a completely different cam to that suggested. And yet, I am told, it still happens.
In selecting any new performance camshaft the starting point must surely be the catalogue Read more…
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 to each other and in particular to that of the piston motion, can never be overstated. Read more…
