Steam Locomotive Driving Wheels,Trucks and Motion
  Most non articulated Steam Locomotives have a Driving Motion  
 made up of Cylinders Pistons, Connecting and Coupling Rodds, Big
 Ends and Slide Bars. The Driving Wheels vary in Size and Nos from
 Two in early engines up to 12 in Very Powerfull Locomotives built
 in the USA such as The Bigboy and The Challenger, Articulated
 Locomotives such as SAR Garratts can have even more. Smaller
 Wheels called Trucks Support the Front end and rear end of most
 locomotives
    The operations involved in Manufacturing a pair of Locomotive
 Drining Wheels are many , the wheel centres are purchased as 
 castings these are put into a large Boring machine, which bores
 a hole in the boss for the axle. They are next marked off for the
 keyway, etc., then placed on a key-seating machine, which cuts the 
 keyway. They are then taken to the hydraulic press, where the axle 
 (supplied accurately machined by the machine shop) is placed in 
 position for the wheels to be pressed on it. Suitable keys or wedges
 are then fitted and driven in. The wheels (now on the axle) are next
 placed in a turning lathe, which turns the rims for the tyres. After 
 this the wheels are taken to a gas furnace, where the tyres 
 (already bored out) are  heated and shrunk on, afterwards being 
 firmly secured by a fastening which is rolled in place by machinery.
 The wheels are then placed in the lathe and tyres turned on the tread
 to the correct dimensions, after which they are put in a quartering
 machine which bores holes to receive the crank pins, which are
 pressed in the wheels by hydraulic press.
     An interesting feature of this shop is a wheel balancing machine,
 an ingenious device for ensuring the corre& balance of wheels for 
 locomotives. By its use adjustments can be made to the wheels until
 they are truly balanced, thus giving smooth running and lessening 
 wear and tear when in service.
     A gas furnace is employed for expanding tyres, for taking off
 or putting on. Gas, with air, passes through a mixer in the correct
 proportions and is conveyed to a tubular ring, and thence through 
 flexible tubes to the burners which surround the tyre at equal 
 distances, thus ensuring uniform heat.