Page:Popular Science Monthly Volume 88.djvu/470

442 A Simple Air-Pump

IN order to obtain great heat or a high temperature, with a blow torch, it is necessary to have a tank supplying com- pressed air.

Obtain an iron-pipe, 2″ inside diameter, 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 ½″ hole and thread with a standard thread. The pipe should be

Construction diagram of a simple air-pump which will supply a blow torch with compressed air

cut 5″ long. Now from the plain end measure in V and cut the pipe diagonally across, as shown in diagram, ⅛″ 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 1″ thick. In the middle on the disk a hole is chiseled out measuring ½ × ¼″ at the bottom and ¾ × ¼″ at the top and is ⅜″ deep. Through the middle of the side and passing through the center of the circle of the disk, a ¼″' hole is drilled right through from one side to the other. At either end of the hole and with the same center a ½″ hole is now drilled. This is to admit the piston pin and the ½″ holes admit the nuts at either end. This part may be seen in the diagram. A and A1 are the inlet valves and are ¼″ diameter, and the center of each hole is ¼″ from the edge of the disk. Leather is placed in these holes measuring ½″ × ⅝" and is glued to the disk by a section about 3/16" from the farthest edge of the leather hinge. The drawing shows this by dotted line across the rectangle. In order that there will be little or no leakage, ½" leather strap is wound around the disk ¼" from top and bot- tom. This is done by making a ridge 1/16″ deep and ½″ 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 ⅜″ iron rod. The length when finished should measure 8½″ This length is not at first needed because we flatten the ends out to the shape, and dimensions given in drawing. The holes are for the bearings 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 ¼″ (perhaps 3/16"). The wire at the top prevents the ball bearing from escaping.

The pressure arm is 1″ × ½″ × 10″ over all. Holes are drilled ⅜″ and 3″ from one end. One serves as the pivot