HELD AT ARM’S LENGTH ABOVE THE HEAD] The backshop for locomotive repairs has rails on the floor--and rails up in the air, too. An engine chuffs in on its own tracks and stops. When it has cooled down, an overhead crane travels on its rails high above the floor. It swoops down, picks up the body of the locomotive and carries the whole thing away, leaving the wheels behind. Now a dozen men swarm over the engine’s body, and before long it looks like an old piece of junk. Some parts get thrown away. But many of them just need cleaning or mending. As the hundreds of parts come off, they are marked with the engine’s number. Then they scatter all over the shop to be inspected and cleaned or fixed and tested. Meantime, other workers take charge of the wheels. In the old days, they had one particular way of testing a wheel. They gave it a good sharp rap with a hammer. If the metal rang out clear and bell-like, it was supposed to be all right. Inspectors in railroad yards went about tapping car wheels, too. And that’s how repairmen and inspectors got their nicknames--car-knocker, car-whacker, car-tinker, car-tink, car-tonk. Wheel experts in the backshop now have scientific tests to make sure [Illustration] that wheels are in good condition. Sometimes they even do X-ray tests, looking for cracks hidden deep inside the metal! When you walk around a big railroad shop, everything seems noisy and helter-skelter. Noisy it is. Wheels screech, hammers pound, fires roar. But the work is really planned out in a very orderly way. And nothing goes to waste. When big machine parts get worn down, they can often be shaved and smoothed and made over into smaller parts for a different purpose. Even the shavings have their uses. A machine with a magnet in it sorts the tiny bits of metal. The iron bits stick to the magnet and other kinds drop through into containers. Later, each kind of metal is melted down to make new parts. Iron dust from one engine’s axle may turn up later in one of the thousands of new car wheels that railroads keep in huge yards. [Illustration] [Illustration] All of this fixing and testing and making over takes a lot of time. A locomotive may spend a month or more in the shop. But at last it is all put together again, complete with a new coat of paint. Now it goes out for a test on the slip-track. This is a greased track where the engine’s wheels whirl round as if it were going at top speed while it is really almost standing still. If everything works all right, its old number is put in place, and an almost new locomotive is ready to highball again. [Illustration: STOP 1 SHORT RELEASE BRAKES PROCEED 2 LONG SNOW BOARD WHISTLE POST] LOCOMOTIVES More than forty different kinds of locomotive work for the railroads. Some of them haul freight, and some are passenger train engines. Some are steam locomotives, some are not.