Practical Switch Work: A Hand-book for Track Foremen

Front matter

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Index

PAGB

The Turnout 7

The Theoretical Lead lo

The Shortened or Practical Lead 14

Turnouts from Curves 21

The Stub Lead 29

Switch or Moving Rails 33

The Frog Number 36

The Frog Angle 40

The Frog Point 43

A Frog-Board 45

Numbers to Use, and Where 48

The Gauge at the Frog 51

Widening the Gauge of Curves 53

To Line Turnout Curves 59

The Line at the Heel of the Frog 67

Cross-overs upon Curves 84

A Ladder Track 100

Curves 127

A Regular Curve 127

A Compound Curve 128

4 INDEX.

PAGE

A Reverse Curve 129

The Degree of Curvature 130

To Ascertain the Degree of Curvature 133

The Limit of Curvatur'^ . , 138

To Line a Curve 139

To Line and Elevate a Reverse Curve 172

Preface

There is, perhaps, no part of track work in regard to which there are so many unimportant differences of opinion upon the part of trackmen as that which pertains to switch work. Trackmen naturally form their opinions from local conditions, and follow the practices of their predecessors or the instructions of their superiors, so it would be only natural for each one to think that his way is the best.

This book is intended for the trackman particularly, to give him, in a concis^ and comprehensive way, what is the best general track practice, from which he may select that which will best meet the requirements or conditions under which he may work.

There are, of necessity, in a book of this kind slight but unimportant departures from mathematical accuracy, also what may seem unnecessary detail of explanation, and also the use and ,: frequent repetition of words or expressions which ^«ijs common among trackmen, all of which are . necessary to make it thoroughly understood and useful to this most worthy class of practical men,

6 PREFACE.

It is not expected that the formulas will be intelligible to them, but, so far as possible, where it is necessary, the formula is accompanied by a simple mathematical demonstration, which, it is hoped, will not be beyond the clear understanding of all.

It is not claimed that this is something new and superior to anything hitherto published.

It is simply a combination of theory and practice, so far as possible, based upon common sense in track work and verified in the experience of hundreds of the best trackmen of the day. So there need be no hesitation to use what is in the book from a fear that it may not be correct, should it happen not to be in strict accord with local practices.

THE TURNOUT.

The single turnout from one track to another is the most simple of all switch connections, the more complicated ones being only developments of it, and what is true of it is also true of them.

The turnout curve, from a theoretical point of view, is most generally assumed to be a simple circular arc or curve, beginning at the point of the switch point or head-block, as C, and ending at the point of the frog B, as shown in diagram No. i : —

That portion of the turnout between the head-block and the frog point, as A to B, is called the lead, and its length for a point, or split switch, as it is most generally called, is the distance from the point of the turnout curve or, in this case, the head-block of the split switch, to the point of the frog measured along the main or straight rail, as A to B in diagram No. i ; and for a stub switch it is the distance to the frog

8 PRACTICAL SIFITCH WORK,

point from the head-block only, the former being called the "point lead" and the latter the "stub lead."

The turnout curve is from C to B, and although the difference in distance between it and the lead from A to B is only a few inches, it should not be mistaken for the lead, nor so regarded.

Whether the turnout is from a straight or curved track, or the switch is a point or a stub, the lead should be measured, as frotn A to B, along the main rail in which the frog is already or is to be placed.

Before any lead can be calculated or ascertained it is necessary to know the gauge of the track, the frog number, and, in the case of a stub switch, the throw also, as the lead and the degree of the turnout curve vary for every different frog, throw, and gauge.

Practically, the difference of a half inch between the two standard gauges— 4 feet 8^ and 4 feet 9 inches — is so small that there need be no difference between them recognized, although it is well to do so where the distances or rules for each gauge are given to calculate the lead.

The "throw" is the distance the sliding or moving rails move at the head-block. The

THE TURNOUT, Q

throw of a point switch in nowise affects the lead, but the throw of a stub switch does.

It has been found in practice that the theoretical length of the lead as obtained upon the assumption that the curve begins at the poirt of the switch and ends at the point of the frog, is too long when used for frogs higher than No. 7, and makes the turnout curve flat near the switch or sharp, in comparison, near the frog. This is on account of the switch point not being thin enough to conform to the theoretical curve, its gauge line at the heel being several inches inside the theoretical curve at that point.

To remedy this it is the practice to reduce the length of the lead so as to obtain a more uniform turnout curve between the heel of the switch and the frog point.

To distinguish these two leads, one is called the "theoretical" or long lead, and the other the "practical" or short lead. ,^

THE THEORETICAL LEAD.

As has been mentioned before, the theoretical lead is the distance to the frog point obtained by calculation upon the assumption that the turnout curve begins at the switch point and ends at the frog point.

For the engineer, the formula or mathematics for this lead, for any gauge and frog, is l=2gn^ in which / is the lead, g the gauge, and ?i the frog number.

For the trackman, it means that the lead is equal to twice the gauge multiplied by the frog number.

For example: What is the lead of a No. lO frog, 4 feet 9 inch gauge ? Twice 4 feet 9 inches is equal to 9 feet 6 inches, or 9^ feet, and ten times 9i feet are 95 feet, which is the theoretical or full lead of a No. 10 frog, 4 feet 9 inch gauge.

For the same frog and 4 feet 8^ inch gauge, the lead is twice 4 feet 8J inches, or 9 feet 5 inches, which, multiplied by 10, equals 94 feet 2 inches.

For No. 8 frog and 4 feet 9 inch gauge, it is 76

feet ; and for 4 feet 8^ inch gauge, it is 75 feet 4

inches.

THE THEORETICAL LEAD, II

It is evident from this that the one-half inch diftercnce between these two standard gauges is so small as not to affect the lead practically, and it is not necessary to make any distinction between them in considering and applying practical rules. But for the purpose of making this formula and rule more easily remembered and useful to the trackman, it can be simplified in^ this way :

Rule, — For 4 feet 8^ inch and 4 feet 9 inch gauges, the theoretical or long lead is equal, practically, to 9^ times the frog number.

9i times 10 equals 95 feet, the lead for No. 10 frog. 9J times 8 equals 76 feet, " " 8

9J times 6 equals 57 feet, " " 6

This will not apply to any other than 4 feet 8i inch and 4 feet 9 inch gauges, and with point or split switches. For all other gauges use the rule of "twice the gauge multiplied by the frog number" for the theoretical lead.

The following is a table of leads obtained by this rule for 3 feet, 4 feet 8^, and 4 feet 9 inch gauges : —

PRACTICAL SWITCH IVORK.

TABLE No. I.

Theoretical Leads.

Frog No.

Leads.

3 Feet.

Feet, incbes.

Feet, inches.

Feet.

37 8

47 6

30 4

;l

56 6

65 11

66 6

84 9

85 6

§4 lO

94 2