ADJUSTING SIDE AND MAIN RODS
Transcript of Locomotive Engineers And Firemen: 
by Charles A Hoxie, 1876
 
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 ADJUSTING SIDE AND MAIN RODS

 The proper adjustment of the side rods is a somewhat difficult task, and requires the exercise of considerable patience on the part of the Engineer who is careful to get them exactly right. It should always be done while the boiler is under a pressure of steam. Sometimes it will be necessary to put them up and take them down several time before they are satisfactorily adjusted. Before placing them in position, the main centers should be trammed from the center marks. After setting up the wedges snug, a few trips should be run in order to ascertain whether or not they are so tight as to require letting down, which should be avoided if possible after the rods are adjusted. The wedges being right, the side rods should be taken down and the pins examined to see whether they do not require re-turning. The side rod brasses should then be reduce to the pins, the brasses when keyed up being left brass and brass. The straps should then be adjusted with the brasses in their places,
  

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the latter keyed up tight and then the exact center of each brass on both ends of the side rods should be obtained. The side rods being thus ready for tramming, the main centers should be trammed alike on both sides, equidistant from center to center, and the same tram may be used on the pin centers, and should they not be exactly right, as is often the case, the rear driving wheels should be slipped until they come right. The main centers and the pin enters being alike, the side rods may be trammed with the same tram, applying it from center to center of the brasses, putting in or taking out "liners" to bring them exact. The key should then be driven down hard and marked next the strap with a scribe or knife. When this is accomplished on both sides and the distances between main centers, pin centers and brass centers are exactly the same, the side rods may be put up, driving the key to the mark made while tramming, and the work is then properly done.
 Frequently a side rod will get to short or too long  wearing  or keying of the  

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brasses. It is then essential that the rod should be adjusted to the proper length, and before it is taken down the end which remains in position should be keyed up. In adjusting the right hand rod, the cross-head should be placed on the extreme forward center, when a screw-jack may be place for convenience sake under the strap end of the rod and the strap slipped back so that the liners back of the brasses may be reached, when they may be lessened or increased as required. There should be as many liners back of the inside brass as it will take without wedging the pins apart, while as many should be placed behind the strap brass as will permit the bolts and key to occupy their proper position through the strap and rod,. The rod should then be keyed up as tight as possible, shaking it with one hand. In the case of an old engine, or one that has been out of the shop from twenty to thirty-six months, it is important that the cross-head should be placed on the extreme forward center on the side of the engine form whence the rod is removed. In such an engine, the pins are likely to be worn out of round where
  

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the friction is greatest, and that point is from the forward side of the main pin to the following quarter. When a rod is keyed up it should always be keyed on the largest part of the pin, so that when the engine is moving the brasses will not bind upon the pin, and the rod will ten run cool and give no trouble.
 A word or two is also proper in reference to adjusting the main rods. In all cylinder there is, or should be a clearance of from one-quarter to three-eight’s of an inch, to prevent the piston form striking the cylinder-heads as the rod varies in length by reason of wear or from unequal lining and keying of the brasses. The clearance should be equally divided in both ends of the cylinder in the following manner: First, key up the main rod, that all lost motion maybe taken up, then ascertain the extreme travel of the piston at both ends of the stroke by placing the cross-head on the extreme center forward and back, making a mark across the guides and cross-head. These marks will be the traveling points of the piston, The striking points of the piston should then be

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obtained by disconnecting the main rod, prying the cross-head back until the piston strikes the cylinder-head and making a mark from the mark first made on the cross-head across the guides, which will be the striking point at the back end of the cylinder Then pry the cross-head forward until the piston strikes the forward cylinder-head, and a mark as before will constitute the striking point at the forward end. The difference between the traveling point and the striking point, will be the clearance of the piston in the cylinder, and it should be divided equally in both ends by taking out or inserting liners. The use of a jack under the rods when putting on the strap renders its adjustment to the proper length much easier. A rod may be shortened by taking out liners between the rod and the brasses and putting them in the strap behind the brasses, and lengthened by reducing in the strap and putting them forward of the brasses next to the rod. Putting them between the brasses and the rod has the effect only to raise the key. And when the brasses are filed, as is often the case, it is only necessary to
 

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insert a thin liner to keep the key raised to its proper place. In reducing brasses the usual rule is to put the same or sufficient thickness in liners back of the brasses as is taken from the brasses , to keep the rod the same length, and also keep the key raised to the proper height. Special care should be taken, as the Engineer will generally find it necessary to use his judgment as to the thickness of the liners. The edges of the brasses should always be rounded off well, no matter how accurately they may be fitted to the pin , otherwise they are liable to run hot. For example, where brasses on two different rods are reduced, one set being rounded and the other left square, it will be found that the former will run the longest and with much less liability to heat. Rounding the brasses is especially advantageous on engines and tender trucks. The attention of engineers is called to this more particularly, because of the fact that most men, in reducing brasses, do little more than take off the sharp edge. They should be rounded at least one-eighth of and inch on the edge, and three-eight’s back from the edge.
 

Chapter 1 - Introduction 
Chapter 2 - Locomotive 
Chapter 3 - The Fireman
Chapter 4 - Advice to Young Engineers
Chapter 5 - Tramming and Center Marking
Chapter 6 - Adjusting Side and Main Rods
Chapter 7 - Pumps and Pump Valves
Chapter 8 - Cylinder and Cylinder Packing


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