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Splitting crank pins

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Opinion is divided on the need to have even firing intervals for engines. With very few exceptions, road vehicle engines fire at equal intervals, while many two-cylinder engines fire at unequal intervals, and some three-cylinder engines in the past have also had some very odd firing orders. The current Yamaha R1 is a four-cylinder engine that has made use of a cruciform crankshaft to give an uneven firing order. This was based on the successful YZF-M1 MotoGP race bike that enjoyed world...

More on nose-fed crankshafts

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In the previous article on crankshafts, the use of the crankshaft as a centrifugal separator was briefly discussed. The principle of centrifugal separation/refinement is well understood, and one only has to hear of news stories about uranium enrichment to appreciate that its uses are widespread. At the end of the previous article, I said we would further develop the idea of air and debris separation. Air in oil is a real nuisance, especially where we want to use the oil to provide the...

Nose feed

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The use of nose-feed crankshafts has been mentioned before, both in these RET-Monitor articles and in Race Engine Technology magazine issue 49. It is certainly not a new concept, having been used in the Rolls-Royce Merlin engines* with great success, nor is their use limited to the highest level of motor racing, having been used with success in LM P1 and LM P2 sportscar racing as well as some production motorcycle engines. The idea behind them is simple: the oil is introduced to the...

Aerodynamic counterweights

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In the search for increased performance, the common direction of engine development has been to increase engine speed incrementally. While this trend is somewhat on the wane - owing to various regulations such as absolute rpm limits as in Formula One, fuel capacity/flow limits or the NASCAR 'gear rule' - high engine speeds are a good way to raise performance, providing that efficiency can be maintained. With increased engine speeds comes increased component surface speeds, so...

The crossplane I4

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Yamaha is the only company running an I4 in the MotoGP series, a layout to which it has been loyal since the inception of the current four-stroke formula; all the other engines are now V4s. Having the cylinders in a vee, rather than in a line, allows the crankshaft to be shorter and stiffer, with fewer main bearings, and the engine to be narrower. This is, however, perhaps not such a great advantage. The reasoning can be found in the width of the human knee. Complete with protective...