The Locomotive Of Today

The Framing, Wheels, etc. : Balance Weights, etc. 131 ment of the coupling rod. Ihe number of spokes or arms radiating from ths boss to tiis rim or frams depends upon the size of th6 wh.661, thsy bsing1 usually spa-csd about 10 or 11 inch.es apart at th.6 rim. Ihe cross ssction v aries from an ellipse to an oblong' with rounded corners, according to the fancy of the designer; but in the cast iron variety, channel or H section is frequently adopted. To ensure smooth running and even wear of tyres and the engine generally, it is necessary to balancs tiis reciprocating and revolving' weights of the motion, and with cast iron wheels as shown it is usual to cast the weights in place. In inside cylindered engines, the driving wheels on the crank axle hav e the balance weights placed on one side of the centre line of the axle and crank pin, the reason for this being that the power is applied to a point somewhat removed from the plane of the wheel. If the weight was exactly opposite. it would not cor- rectly balance, as the other crank which is at right angles has an influence upon it. The exact amount of offset is ascertained when the wheel is designed. It is usual to com- pletely balance the whole of the revolving and two-thirds of the reciprocating weights. In the leading and trailing coupled wheels the weight is placed exactly opposite the crank pin, and is much smaller, being only sufficient to balance the coupling pin and. boss, and half tiis sids rod. In the sketch, the fulf lines represent the outline of a driving wheel, and the dotted lines that of a leading or trailing coupled wheel. In outside cylindered engines the balance weights are placed exactly opposite the crank pin, as the power is here applied approximately in the plane of the wheel, and the influence of the other crank is not felt. With wrought iron wheels the weights may be forged in place, but it is more usual to fit them in afterwards and fasten by rivets passing through them and plates on the outside and inside of the spokes. The hole for the reception of the axle is bored out, and m some cases has a recess about ot an inch deep and an inch larmer than the hole for the reception of a collar turned 011 the axle, this being done to prevent the axle from being forced on too far. Most makers also fit the driving wheels with a Steel key about 1 inch by inches in section, in a keyway formed halfin the wheel and half in the axle to prevent the wheel from turning upon the axle when working; but it is not customary to provide keys in the uncoupled or carrying- wheels as they are an unnecessary precaution. The axles are forced in cold by a hydraulic pressure of from 45 to 50 tons in in cast iron wheels, and from 80 to 120 tons in those of cast Steel.