Finding Locomotive Dead Centers
Page 3 of 5
By Jeffrey G. Hook
(Scroll down for all illustrations. Captions above illustrations.)
Image 1. - Deerfield and Roundabout Railway engine number 284 over the "drop pit" at the Deerfield shops. The side rods will not be taken down which will require all driving wheels to be turned when finding the dead centers. The locomotive is equipped with roller bearing driving boxes and pedestal binders of sufficient strength that allow shim blocks to be placed between the driving boxes and pedestal binders which raises the axle center lines to their normal working height relative to the cylinder center lines. If a "drop pit" was not available, or the bottom half of the driving boxes or the pedestal binders could not support the driving wheels, then the locomotive would be moved forward and backward as needed on a section of straight level track. In full size practice, to eliminate the necessity of moving the locomotive, a power operated roller device is placed under the main driving wheels. The side rods are removed, the main rods are installed, and the drive rollers of the device are adjusted to raise the main driving wheels slightly off the rails. If necessary, jacks are applied to the frame to bring the center line of the cylinders into proper relation to the center line of the main driving axle.
Image 2. - For finding the front dead center the dial indicator and associated support rods are clamped to the valve-stem crosshead guide and positioned so as not to foul moving parts such as the combination lever.
Image 3. - The dial indicator is positioned to make contact with the front flat of the crosshead wrist pin nut and adjusted to read zero when the crosshead is near to the apparent front dead center. The crosshead wrist pins on this locomotive do not rotate which makes it feasible to use the crosshead wrist pin nuts as contact points.
