side rod bearings?

[lonewoof]

This question occurred to me after reading about someone with a model loco that had a bind in the siderods: HOW did REAL locomotives handle this? There has to be SOME way of allowing some slop; the drivers are sprung so the rod journals have to adjust. I can't believe they just wallowed out the journals to allow for movement.

[ndbprr]

This is not going to be a 25 word or less answer! Pre roller bearing (ball bearing to most novices) a brass or broze bearing was used. We used these on Corliss steam enginesat one plant I worked early in my career. The pin was steel and the bearing was brass because it waseasier to replcae the bearing then the pin. Yes wear occurred - daily. You could tell when an adjustment was called for because it would start to knock a little. The bearing was in two halves with a wedge behind one half. The two brasses per bearing were molded so there wasa gap between the edges where they would normally touch. It was a routine matter to stop the engine, remove the retainer, tap the wedge with a hammer and put the reatiner back on. This all took about 5-10 minutes and was considered routine maintenance. Brasses on a side rod could be changed out in a roundhouse on one shift without the need for a crane with one restriction. The engine needed six drivers ormore so that at least two bearings supported the side rod while additional bearing were removed one at a time and replaced when wear exceeded limits. On 4 drivered engine it would be necessary to support the end of the side rod with a come along or crane. Now move forward to the roller bearing era. First of all railroads didn't buy roller baerings for freight cars or freight engines until very let in the manufacture of steam. Timken sponsored and engine called the four aces (#1111) that astonished the railroads with reduced maintenance and rolling characteristics. Freight cars started getting serious numbers of roller bearings in the 60's but in any case a properly maintained and lubricated roller baering has very little wear and is designed to do a couple of things on a side rod. The first is to provide rotational bearing surface as the rod rotates around the pin. the seond is to sometimes provide lateral movement when the wheelbase is on a curve. So sometimes there was the ability to change the allignment slightly from 90 degrees to the pin. This is much easier to describe with a picture than words but if you look down on a bearing lined up with the pin you could take the outer race and turn it so the front edge and back edge are turned a little like looking down on your tire when going around a turn. The obvoius give away for engineswith rller bearingsis a thickening of the sdie rod over normalamounts in the bearing area . The N&W J, A, and Y classes are great examples.

[Leon Silverman]

The springing allowed only vertical play in the movement of the drivers and connecting rods. The binding that occurs in model engines occurs because there is a horizontal interference or rubbing that occurs. If these rods were laid on a flat surface, or viewed from directly on top of the model, then a curvature or surface roughness would be evident. This distortion is what causes the binding if the pieces have been lubricated.