442 



Popular Science Monthly 



A Simple Air-Pump 



IN order to obtain great heat or a high 

 temperature, witli a blow torch, it is 

 necessary to have a tank supplying com- 

 pressed air. 



Obtain an iron-pipe, 2" inside diam- 

 eter, and having one end closed up with 

 a pipe-end which may be removed at 

 will by unscrewing. In the center of this 

 end drill a %" hole and thread with a 

 standard thread. The pipe should be 





/ 



Constxuction diagram of a simple air-pumfj. which will 

 supply a blow torch with compressed air 



cut 5" long. Now from the plain end 

 measure in V and cut the pipe diagon- 

 ally across, as shown in diagram, y^" 

 holes should then be drilled at either end 

 and in the same line of the pipe. These 

 holes are for the screws, which are to 

 hold the cylinder in place on the base, 

 and therefore they should be sunk 

 rather deep so as not to interfere with 

 the working of the piston. It will be a 

 good idea to smooth the inner sides of 

 the pipe with some emery cloth. 



The piston is the most important part 

 of the pump and ought to receive most 

 attention. It is made of a wood disk 

 2" diameter and V thick. In the middle 



on the disk a hole is chiseled out measur- 

 ing i-i" X 1/4" at the bottom and %" x 

 Vx" at the top and is %" deep. Through 

 the middle of the side and passing 

 through the center of the circle of the 

 disk, a Vx' hole is drilled right through 

 from one side to the other. At either 

 end of the hole and with the same center 

 a 1/2'" hole is now drilled. This is to 

 admit the piston pin and the V2" holes 

 admit the nuts at either end. This part 

 may be seen in the diagram. 

 A and Ai are the inlet valves 

 and are V-t" diameter, and 

 the center of each hole is 

 I/4" from the edge of the 

 disk. Leather is placed in 

 these holes measuring i/i" x 

 %''' and is glued to the disk 

 by a section about 3/16" 

 from the farthest edge of 

 the leather hinge. The draw- 

 ing shows this l)y dotted line 

 across the rectangle. In or- 

 der that there will be little 

 or no leakage, a \-z' leather 

 strap is wound around the 

 disk 1/4" from top and bot- 

 tom. This is done by mak- 

 ing a ridge 1/10''' deep and 

 1/2'" wide in the middle of 

 the side of disk when it is 

 turned out. The leather 

 should be* glued in with the 

 rough side out. 



The connecting rod is 

 made of %" iron rod. The 

 length when finished should 

 measure S^^"- This length 

 is not at first needed be- 

 cause we flatten the ends 

 out to the shape, and dimensions given in 

 drawing. The holes are for the bear- 

 ings of piston and arm pins. It is very 

 easy to forge the ends in a fire made for 

 heating the house and to hammer them 

 on a small piece of iron. 



The air is kept from returning to the 

 pump by a valve set on top of the tank. 

 The drawing gives all the information 

 necessary. The ball bearing used is a 

 little smaller than 14" (perhaps 3/16"). 

 The wire at the top prevents the ball 

 bearing from escaping. 



The pressure arm is \" x y-^' x \o" 

 over all. Holes are drilled %" and 3" 

 from one end. One serves as the pivot 



