Now we will describe the method for constructing the face moulds of a handrailing for a stair suitable for the plan shown in Stair Parts Fig. 5. In this example two problems are used to obtain the development of tangents, bends and twists of the rail.
Let Stair Parts Fig. 31 represent the ground plan of cylinder with the risers marked in position, also the elevation and "pitch" inclination of center line.
It will be noticed that the pitch-line is perfectly straight. This is caused by the risers being placed so as to bring them exactly the width of a step from each other on the tangent line, as shown in the plan and elevation, Stair Parts Fig. 23 to Stair Parts Fig. 31 This is a point the student should always bear in mind; locate the risers this way whenever practicable, and you are sure to have a good-looking, easy rail.
To construct Stair Parts Fig. 31, the plan of cylinder being made with risers and center line of rail drawn, swing out A and D to meet BC extended, also the risers E and F; place the pitch-board at the point where E cuts the line BC, keeping the risers parallel with BA, and the raking side cutting through the point where A swings, around to BC. Mark the step and riser and continue the elevation as shown; draw the pitch-line, draw GH, continue DC to L, draw MN at right angles to GH and extend to chord line at S; from N at right angles to pitch-line draw a line indefinitely; with L for center and LH for radius, describe arc cutting
Stair Parts Fig. 31
line drawn from N at O; connect" LO, and the triangle OLP gives the tangents for the face mould.
The pitch-line being straight, the tangents are all of equal lengths, so it will be seen at once that the face mould obtained will be the same for both upper and lower wreaths, and the bevel for both ends is found at R, as shown.
Stair Parts Fig. 32
Stair Parts Fig. 32 is similar to Stair Parts Fig.12, excepting the development of tangents, which it will be observed is obtained somewhat differently.
Stair Parts Fig. 33 describes how the development can be obtained by the method shown in Stair Parts Fig. 12. While this method is perfectly correct in all cases where the tangents are of equal lengths, still it is better to use the methods shown in Stair Parts Figs. 32 and 34, as they will be more correct whenever a change occurs in the pitch. Stair Parts Fig. 34 is a facsimile
Stair Parts Fig. 33
Stair Parts Fig. 34
of the "development" in Stair Parts Fig. 31, and is drawn in order to make the student more familiar with this important problem.
In order to produce the face moulds, bevels, etc., for the flight of stairs exhibited in the plan, Stair Parts Fig. 6, we must proceed as follows. Fig. 35 shows the ground
Stair Parts Fig. 35
plan and elevations of treads and risers. The explanations given for the 'solution of previous examples will apply to this one if the figure be properly, studied, as the method of proceeding to lay down the rail is exactly the same.
In the elevation it will be seen that one pitch is employed for the wreath and the connections made with the pitch of the flyers by a ramp above and below.
Stair Parts Fig. 36, 37, 38 (from top to bottom)
One pattern answers for both ramps, as the pitch over the flyers is the same in both cases.
By carefully studying Stair Parts Fig. 12, the landing wreath, Fig. 36, will be easily understood. Care must be taken to locate the last riser as near half a step from the level tangent as possible. Stair Parts Fig. 39 shows tangents, center line of rail and the application of the bevels for the wreath. Stair Parts Fig. 38 shows pattern for lower ramp, and is simply reversed for' the upper.
These examples are simple and ought to be readily digested by any workman who has ever had the least experience in stair-building. The young student ho has never helped to build a stair or erect a handrail should master these simple problems (on paper) d the first opportunity that offers to see a flight of stairs and handrail set up he should embrace it, and the whole mystery of handrailing will disappear at once.