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The Differences Between Forged Flanges and Cast Flanges Professional

منذ 8 أشهر Multimedia Saïda   389 الآراء

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The railway wheel

A typical railway wheel carries a load of about ten tonnes, roughly twice the equivalent for a road-going truck. The outer surface is called the tread. With a diameter typically of 1.0 m or less, the tread is roughly 100 mm wide. Like a pneumatic tyre, the railway wheel must handle the various forces needed to propel the vehicle forwards, slow it down, and hold it centrally on the track. But there are three striking differences. First, each railway wheel has a narrow lip or flange on the inside edge whose purpose is to stop the wheel from slipping off the rail. Second, the contact stresses between the wheel and the running surface are much more concentrated than those associated with a pneumatic tyre, reaching values that, paradoxically, exceed the yield point of the steel from which they are made. Third, railway wheels are almost always coupled together in pairs, each pair joined by a rigid axle to form what is known as a wheelset. A wheelset is extremely heavy by comparison with its equivalent on a road-going vehicle, and when you look at the various components, it’s not difficult to see why. Let's start with the disk.

One can think of a railway wheel as a solid disk whose tread is machined into the desired profile. In practice, some wheels have a separate ‘tyre’. The tyre, usually about 60 mm thick when new, is made of hardened steel. It is heated and pressed onto the wheel disk, where it shrinks as it cools and tightens its grip so that no bolts are needed to hold it in place. Ideally, for a smooth ride the diameter of the wheel should be as large as possible (see Section G1209), and in fact, the driving wheels on some early steam locomotives were 9 feet (over 2.7 metres) in diameter. They were magnificent examples of craftsmanship, and they needed to be large because they were driven by connecting rods, pistons and valve gear that were liable to fail if worked too fast, and a large wheel compensated by carrying the loco further along the track for each piston stroke. Later, when these limitations were overcome, the driving wheels were scaled down to a more manageable size. Nowadays, they are made of pressed steel, and for many the cross-section is wavy rather than flat. A wavy cross-section provides resilience and allows the rim to expand and contract slightly with changes in temperature without putting the disk under too much stress; useful properties for tread-braked wheels and those with separate tyres. Rubber inserts make the wheel more resilient still, helping to reduce any impact on the suspension when it passes over a gap in the rail.

What Is an Axle Shaft?

An axle shaft is a solid steel shaft that runs from the differential and gear set of an axle housing to the wheel. Used in two distinct configurations, the axle shaft can be a straight shaft with splines machined into each end to engage both the differential on one end and a drive flange on the other. It also can be a straight shaft with splines machined into the differential end and a flange on the other to mount a wheel to the axle. The first design is primarily used with a full floating axle design, while the latter is commonly used on passenger cars and light pickup trucks.