Sheet metal drafting/Chapter 10

by Ellsworth M. Longfield

CHAPTER X
COMBINATIONS OF VARIOUS SOLIDS

Objectives of Problems on Combinations of Various Solids.

Problem 35
ATOMIZING SPRAYER

66. The Atomizing Sprayer.—This type of sprayer consists of a cylindrical tank or reservoir in which is soldered a small tube that reaches nearly to the bottom of the tank. Upon this tank is mounted a pump, having a nozzle in the form of a scalene cone, and with a relatively small orifice. The small tube is placed in the tank in such a manner that its top is directly in front of, and on a level with, the center of the orifice of the pump. When a stream of air is expelled from the pump, it creates a partial vacuum in the tube, causing the liquid to rise. When the liquid encounters the stream of air flowing from the pump, it is broken up into a fine spray.

The Elevation (Fig. 199).—A circle 4 in. in diameter is first drawn to represent the end of the reservoir. The elevation of the pump barrel is drawn next, placing it in a horizontal position and tangent to the reservoir. The following are next drawn in order: (1) The pump rod assembly; (2) the $\scriptstyle {\frac {1}{16}}$-inch diameter tube in its proper location; (3) the wooden plug that guides the pump rod; (4) the brace, according to the dimensions given.

Pattern of Conical Nozzle (Fig. 200).—The elevation of the cone is reproduced and a half-profile attached directly to the base. This half-profile is divided into four equal parts. The shortest distance from the base to the apex is the line from point 1. Therefore, with point 1 as a center, arcs are drawn from points 2, 3, and 4 of the half-profile, cutting the base of the cone as shown in Fig. 200. With the apex as a center, arcs are drawn from each intersection of the base of the cone. Any point on the arc from point 1 is selected and is connected with the apex. This line will serve as the starting line of the pattern. The compass is set equal to the distance between any two divisions of the half-profile. Starting from point 1 of the pattern, point 2 is found by drawing an arc (with the compass as already set) that intersects the arc drawn from the second intersection of the base line of the cone. In like manner points 3, 4, and 5 can be located. A straight line from point 5 to the apex will give the half pattern. Since both halves are exactly equal, the other half may now be drawn by reversing the process already described. A ¼-inch lap should be added to one side of the pattern.

Figs. 199–203.—Atomizing Spray Pump.

Pattern of Pump Barrel (Fig. 201).—The pump barrel blank is a rectangular piece of metal whose length is 19⅝ in. (⅛ in. being added for joining to the nozzle), and whose width is (1¾ in.×π)+½ in. for locks. A pattern of the pump barrel should be drawn as shown in Fig. 201, The ⅛-inch screw holes should be equally spaced with the circumference of the barrel, the outside holes being $\scriptstyle {\frac {1}{6}}$ of the circumference distant from the circumference lines, in order to bring the seam in the center. A $\scriptstyle {\frac {3}{16}}$-inch hole must be provided, as shown, for a vent.

Pump Rod Details(Fig. 202).—The pump rod should be 21½ in. long and should have a stop washer soldered 3½ in. from one end. This stop washer prevents the leather packing from becoming injured by striking the nozzle. A ¼-inch standard stove bolt thread (18 threads per inch) is cut on each end of the rod for a distance of ½ in. The thread near the stop washer is intended to screw into wooden handle. Two iron washers of unequal diameter are drilled and tapped to receive the thread that is cut on the pump rod. The cup leather is clamped between these washers, the larger washer being on the side near the handle of the pump.

Pattern for Reservoir (Fig. 203).—The pattern for the body of the reservoir is a rectangle whose length equals (4×π)+½ in. for locks, and whose width equals 5 in. A center line is drawn and the $\scriptstyle {\frac {1}{16}}$-inch hole for the tube is located upon it. A hole for the ¾-inch screw can top is also located as shown in Fig. 203. The pattern for the ends of the reservoir is a circle 4 in. in diameter to which is added a ⅛-inch burr to act as a lap for soldering the ends to the body. The brace is a rectangular piece of tin ¾ in. wide. The length of the brace is taken directly from the profile as it appears in Fig. 199.

Schedule of Materials.—When making a drawing of an article that has many parts, a schedule of material is included in the drawing. This schedule saves a large amount of description regarding material, etc., that would otherwise have to appear on the drawing for each part, thereby complicating the drawing and making it more difficult to read.

67. Related Mathematics on Atomizing Sprayer.—In planning an article that is to be manufactured the draftsman must constantly strive to keep the cost as low as possible. The largest items entering into the cost are material and labor. The various parts must be so designed that they will "cut to advantage" from the stock sizes of sheets. However, there are cases where a small amount of extra wastage will be more than compensated for by the saving in labor. Figure 204 shows a layout that would preclude the possibility of using the squaring shears and the circular shears for cutting out the blanks.

It is evident that cutting must be done with the hand snips. While this would be desirable if but one sprayer were to be made, it would result in an increased labor cost in quantity production.

Figs. 204-205.— Plan for Cutting Atomizing Spray Pump Parts from Sheets.

Figure 205 shows the method of arranging the pump barrel and brace patterns on the sheet in such a way that they can be cut in the squaring shears. The ends for the reservoir and the pump nozzles are arranged for cutting in the squaring shears by cutting along the dotted lines. After the sheet is cut into blanks, the circular ends may be cut true to shape in the circular shears. The nozzle, however, will have to be marked from a master pattern and the curved edges cut by the hand snips.

Problem 35A.—Show by means of sketches how the patterns for the atomizing sprayer should be arranged on the sheet in order to obtain the greatest saving in material and labor in the manufacture of twelve complete sprayers.

Problem 35B.—What is the percentage of waste per sprayer?

Problem 36
ASH PAN WITH SEMICIRCULAR BACK

68. Ash Pan with Semicircular Back.—Figure 206 shows the plan of an ash pan having a semicircular back. The sides and back flare 1⅛ in., while the front of the pan flares 1½ in. Figure 207 shows an elevation of the pan. The pan is made from five pieces of metal (two sides, front, back, and bottom), all joints being double seamed. The top is reinforced with No. 8 wire.

Pattern for Semicircular Back.—The plan and elevation are drawn according to the dimensions given in Figs. 206 and 207. An extension line is carried downward from the center from which the semicircular ends are drawn. Another extension line from the slant height (line 16–17 of Fig. 207) is drawn to intersect the first extension line, thereby locating the apex of the cone of which the semicircular end is a part. With the apex as a center, and a radius equal to the distance from the apex to point 17 in Fig. 207, the arc of stretchout, Fig. 208, is drawn. The spaces 2, 3, 4, 5, 6, 7, and 8, taken from similarly numbered spaces in Fig. 206, are set off upon this arc. The pattern is completed by an arc drawn from point 16, using the apex as a center. One-half inch locks are added to both edges of the pattern, a ⅜-inch wire edge to the top and a $\scriptstyle {\frac {3}{16}}$-inch single edge to the bottom of the pattern.

Pattern for Sides of Pan.—Extension lines are dropped from points 9, 13, and 8 of Fig. 206. At any convenient location the horizontal line 9–8 of Fig. 209 is drawn. Parallel to this line, and at a distance equal to line 16–17 of Fig. 207, the horizontal line 12–13 of Fig. 209 is drawn. The intersections of these lines with the extension lines previously drawn will determine the location of points 12 and 13. Lines 8–12 and 9–13 are drawn. A ⅜-inch wire edge is added to the top, and a $\scriptstyle {\frac {3}{16}}$-inch single edge to the bottom of the pattern. A ½-inch double edge is added to side 9–13 for double seaming. These patterns must be formed "right and left" in making the pan. The rivet holes for the bail ears must be located as shown in Fig. 209.

Pattern for Front of Pan.—The line 9–1 of Fig. 211 is drawn equal in length to line 9–1 of Fig. 206. A line is drawn parallel to this line and at a distance equal to line 14–15 of Fig. 207. Perpendiculars are dropped from points 1 and 9 of Fig. 211 cutting the line last drawn. A distance of 1⅛ in. is measured in from each perpendicular in order to locate points 10 and 13. Lines 1-10

 

Figs. 206-212.—Ash Pan with Semicircular Back.

 

and 9-13 complete the pattern. Three-sixteenths inch edges are added to the sides and to the bottom, and a ⅜-inch wire edge to the top of the pattern.

Pattern of Bottom of Pan.—The profile of the bottom, Fig. 210, of the pan as shown in Fig. 206 should be reproduced, and a ⅜-inch double edge added to all sides of this profile in order to double seam the bottom of the pan to the sides and ends.

The Bail.—The bail is made from galvanized ¼-inch rod, and is attached to the pan by bail ears. The bail ears are located "off center" to assure steadiness when carrying the pan. Figure 207 gives the location of the bail ears. An elevation of the bail, as shown by Fig. 212, is drawn. If care is taken to give center line measurements, the workman in the shop can "scale" his dimensions directly and, therefore, a pattern for the blank will not be needed.

69. Related Mathematics on Ash Pan.—Problem 36A.—What is the area of Fig. 208?

In solving this problem use the formula ${\frac {B+b}{2}}\times H={\text{Area}}$

${\begin{aligned}B&={\text{length of longest arc}}\\b&={\text{length of shortest arc}}\\H&={\text{length of ``line a''}}\end{aligned}}$

Problem 36B.—What is the total area of the sides (two wanted) as shown in Fig. 209?

Use the formula ${\frac {B+b}{2}}\times H={\text{Area}}$
in which

${\begin{aligned}B&={\text{lower base (over-all dimensions)}}\\b&={\text{upper base (over-all dimensions)}}\\H&={\text{total height between bases}}\end{aligned}}$

Problem 36C.—What is the total area of Fig. 211?

Problem 36D.—What is the area of Fig. 210? Figure 210 is a combination of a rectangle and a semicircle.

Problem 36E.—How long must the wire be to stiffen the top edge of the pan? How much rod is needed to make the bail?

Problem 36F.—Number 24 gage black steel weighs 1.02 lb. per square foot. How much will the pan weigh exclusive of the bail and the top wire?

Problem 37
ROTARY ASH SIFTER

70. The Rotary Ash Sifter.—This problem on the rotary ash sifter presents a composite of nearly all of the pattern principles that have been given in the preceding problems.

Figure 213 shows a section and Fig. 214 an end elevation of the sifter. Extension lines should be used to establish the elevation positions of the views, but these are omitted from the drawing to avoid confusion of lines.

Pattern of Side (Fig. 215).—A line of stretchout is drawn and upon it is placed the spacing between letters A, K, B, J, C, F, D, and H as shown in Fig. 214. Measuring lines are drawn through each of these points. It should be noticed that points E and D, G and H, M and A fall on the same horizontal lines of Fig. 214. Because of this, they should be similarly placed in the stretchout, Fig. 215. Starting from point A of Fig. 213, an extension line intersecting measuring line A of Fig. 215 should be dropped. In like manner all points of intersection are located. Three-sixteenths inch single edges are added, where shown, to provide for double seaming, and a ⅜-inch edge which is to be bent at right angles to receive the hook of the sliding cover, is allowed for.

Front End of Hopper (Fig. 216).—A line of stretchout is drawn first. Upon this line the distance MK of Fig. 213 is laid off. Measuring lines are drawn through these points. Extension lines from each end of the lines M and K are dropped until they intersect the measuring lines of Fig. 216. These points of intersection are connected by four straight lines to obtain the outline of the pattern. The necessary allowances, as shown, should be added. A notch must be cut out to provide for each hinge strap which is to be folded over the exposed wire and riveted to the cover.

Patterns for the sliding cover, front end of outlet, and bridge are developed by the same method as was the front end of hopper. The spaces KJ, JH, and EFG are taken from correspondingly lettered spaces of Fig. 213. The hook, shown in Fig. 218, is made of 1 in.×⅛ in. band iron.

Pattern for Cover of Barrel (Fig. 220).—The cover is made from one piece of metal, the rim being "flanged" as described in Chapter VII for the treatment of the ash barrel bottom. The width or the opening is represented by line DE of Fig. 214, and the length by line D-E of Fig. 213. A ⅜-inch double edge is added to the long sides and a $\scriptstyle {\frac {3}{16}}$-inch single edge to the short sides of the opening. The allowance for flanging must be computed by the formula

 

Figs. 213-221.—Rotary Ash Sifter.

 

given in Chapter VII. Outside of this allowance a ⅜-inch wire edge is provided for covering the wire.

Pattern for Hopper Cover (Fig. 221).—This pattern is a rectangle whose length equals line AM, Fig. 214, plus ¾ in. for clearing

 

Figs. 222-229.—Patterns for Rotary Ash Sifter.

 

the wire, and whose width equals line AM of Fig. 213, plus ⅜ in. for clearance. Rivet holes for the hinge straps should be laid out carefully. A double edge is provided on three sides to be formed according to the sectional view, A ½-inch hem will serve to stiffen the cover at the hinged edge.

Pattern of Rotating Screen (Fig. 222).—The rotating screen is made of 3 mesh No. 18 wire galvanized netting. It is in the form of a frustum of a cone as shown by Fig. 222. A cast-iron frame, shown to the left of Fig. 222, is provided for each end of the screen. The outer face of this frame is tinned and the netting is soldered to it. The edges of the screen have a ⅜-inch lock turned outward, and a galvanized-iron clinch strap is slipped on, hammered down, and the whole seam "tacked" with solder. The pattern of the frustum, Fig. 223, is obtained in the manner described in Chapter V.

Pattern of Rear End (Fig. 225).—A rear elevation of the sifter is drawn as shown in Fig. 224, all dimensions being taken from Figs. 213 and 214. A line of stretchout is drawn and upon it are set off the spaces AC and CD of Fig, 213. Measuring lines can now be drawn and extension lines dropped from points A, C, and D of Fig. 224, Straight lines connecting points of intersection will give the outline of the pattern, A ⅜-inch wire edge should be added to the top, and ⅜-inch double edges to the other three sides.

Pattern for Galvanized Screen (Fig. 229).—Figure 226 shows that part of the sectional view. Fig. 213, that has to do with the screen and shield, while Fig. 227 is a front elevation. The pattern for the galvanized iron shield is copied directly from Fig. 227, and the necessary laps added as shown by Fig. 228. The line PR is extended to the right of Fig. 227, making RW equal in length to BS of Fig. 226. With R as a center, arcs are drawn from points 15, 5, 6, 7, 8, and N, cutting the line RT, which is drawn at right angles to RW. At any convenient point, a line PR, Fig. 229, is drawn equal in length to line PR of Fig. 227. With R and P of Fig. 229 as centers, and a radius equal to WN of Fig. 227, arcs interesting at point N are drawn in. With P and R, Fig. 229, as centers and radii equal to W–8, W–7, W–6, W–5, and W–15 arcs bearing away from point W are drawn. Starting at point N of Fig. 229, the distances N–8, 8–7, 7–6, etc., should be made equal to distances N–8, 8–7, 7–6, etc., of the profile of the circle in Fig. 227. The straight lines setting forth the flat and curved surfaces should be drawn in. A 1-inch lap is added to the curved surfaces.

71. Related Mathematics on Rotary Ash Sifter.—

Areas of Trapezoids.

Problem 37A.—What is the area of Fig. 216? Of Fig. 217? Of Fig. 218? Of Fig. 219? Of Fig. 225?

Area of Circle.

Problem 37B.—Find the area of Fig. 220, using the over-all dimensions. What per cent of the metal is cut away for the opening?

Area of Rectangle.

Problem 37C.—Compute the area of Fig. 221 by using the overall dimensions.

Areas of Triangles.

Problem 37D.—Divide the pattern of the sides of Fig. 225 into triangles and compute the area of each.

Problem 37E.—What is the combined total area of both sides?

Problem 37F.—Treating Fig. 229 as a combination of triangles, what is its area?

Frustums of Cones.

Problem 37G.—What is the area in square inches of Fig. 223?

Problem 37H.—By drawing the imaginary line between points 5 and 13, Fig. 228 would be converted into a trapezoid. What would be its area?

Problem 37–I.—What is the combined area of all of the patterns required for the rotary ash sifter?