Some engines use double overhead camshafts (DOHC), so would have as many as four across two banks of cylinders. Because you need at least one camshaft per cylinder bank, inline engines need as few as a single camshaft, whereas a V arrangement would require at least two. There can be a varying number of camshafts in an engine, depending on its cylinder arrangement and valve operation. This is better known as variable valve timing. Moreover, the shape of the cams themselves is also carefully crafted to control the speed at which the valves open and close. To ensure this timing, the camshafts are connected via a timing belt or chain to the turning of the crankshaft - which is directly moving the pistons inside the cylinder. This makes them not only critical to the operation of an engine, but because the opening and closing of the valves must be carefully and perfectly synchronised with the movements of pistons, they also have a drastic effect on performance. Their calibration precisely controls the amount of air-fuel mixture that enters the chamber, and how efficiently the spent exhaust gases from the previous ignition can exit the chamber making way for the next charge. In a modern internal combustion engine they are typically, but not necessarily, positioned directly above the cylinder banks where they act to control the valves. When the shaft is rotated, the shape of the cam allows it to act upon a valve or switch to a degree matching the severity of its shape - with the speed of rotation controlling the rate of action. Synchronicity and ShapeĪ camshaft is a relatively basic component – a simple length of rod, or shaft, with shaped lobes positioned along it, these have been christened ' cam lobes'. This is because the cam itself is an incredibly ancient idea that stretches right back to 13 th century Turkey - where it was used in a variety of mechanisms by the legendary Ismail al-Jazari and described in his ‘Book of Knowledge of Ingenious Mechanical Devices’.įast forward to the 21 st century and its principles of operation are the same now as they were then. The camshaft however, is one of the older parts and has been dutifully working since the early days of engine invention and progression. It sounds simple enough, but as we know the internal combustion has gone through more refinement and development than just about any other mechanism on the planet, so that is now an extremely complex system of parts. We’ll assume you’re familiar with the basic function of a combustion engine – fuel and air are ignited inside a cylinder, producing explosive energy that’s converted into motion via the pistons, crankshaft and transmission. Remember also Mass and Weight are not the same thing.Camshafts are another of the many critical components required to enable a combustion engine to work, but what exactly is a camshaft and why is its role so important? Old Tech Most common was in the early 1900's and especially after WWI (World War I) when all the surplus army trucks were put into service delivering goods on non-paved roads across the nation and world. So on-road was what today is called "off road"
Yes, it is the term used for the LOAD capacity 2.5 tons (5000 pounds), and note, back in those days there were not many paved roads. “Deuce and a half" is an extremely common term, and has been used, I would say, since there were motorized vehicles and trucks. I would even go as far to say it is more sexually based referring the female anatomy either to cleavage or the rear end meaning a pair and a half, meaning of course very well endowed. I would say definitely say it is American slang either about weight 250 pounds not Kilograms (551#) needless to say it is derogatory. It comes from the French "deux" probalby through tennis. Never heard of calling a woman a duce and a half, however "deuce" is a term meaning "2". Some people say it is the number axles or the axle load in addition to vehicle weight.
If you ever Googled the term you would definitely see the 2-and-a-half-ton army truck is the first thing that pops up.