Simple Designs for Siieet Metal Working 



I. — Trench periscope or comer lookout for boy scouts 

 developed from a ninety - degree elbow pattern 



By Arthur F. Payne 



Assistant Professor Manual Arts, Columbia University 



ONE of the most important "safety 

 first" inventions of the present great 

 war is the trench periscope. By the 

 aid of this very simple invention the soldier 

 is able to look over the top of the trench and 

 observe the movements of the enemy in 

 comparative safety. It is also used in 

 looking around the corner of one of the 

 modern zig-zag trenches when a part of a 

 trench has been captured and the enemy is 

 still in the other part. 



The periscope is a necessity to the 

 soldier, but there are many ways in which 

 the out-of-door boy may use it. In "I 

 Spy," "Hide and Seek," etc., the posses- 



as shown in the diagram. The mirrors 

 must lie squarely across the elbow, being 

 held in place by strips of tin soldered to the 

 pipe on the inside and then bent over the 

 mirrors. 



For the benefit of the boy who is working 

 in a shop and wants to make periscopes for 

 sale, or who wants to know the inside of 

 that mysterious process called "developing 

 patterns" the method of developing the 

 pattern is given. The same pattern will do 

 for all the pieces A-B-C-D. All that is 

 necessary is to develop the pattern for 

 piece A. Draw the elevation "A" the size 

 and shape of the elbow desired. Draw the 

 bottom view of the pipe as shown. Divide 

 the bottom view into i6 equal parts and 

 number them. Draw the base line E-F, 

 getting its length by taking the distance 

 between any two points on the bottom 

 view, and stepping it off 1 6 times. Number 



A pattern layout for the construc- 

 tion of an ordinary elbow in sheet 

 metal. Diagram showing mirrors 





sion of a periscope gives one a de- 

 cided advantage. It is of value in 

 Boy Scout activities; looking 

 over a wall, from the back of a ^iJ"V 

 building, or from behind a bush or 

 rock, the scout can observe the 

 territory beyond without exposing himself. 

 To make one, take 3 pieces of tin pipe 

 2'in. in diameter. The largest piece should 

 be 20 in. long. Solder the two short pieces 

 to the ends of the long piece at right angles 

 to it, forming an ordinary 90 deg. elbow. 

 Before the pieces are fastened together, fit 

 two pieces of mirror in place in each elbow 



these points from i to 16. This will give 

 the circumference of the pipe. It may 

 seem strange that at each end of the base 

 line we have a line numbered i, but when 

 the pipe is bent around into a tube these 

 two lines come together and form one 

 point, as is seen in the bottom view where 

 it is marked number i-seam. From the 



985 



