With the lamps using petrol, the only parts requiring attention are the plate from which gas issues and the wick. Unlike the paraffin nipple, this is a circular stamping of brass approximately 3⁄4 in. in diameter with a fine hole in the centre. To remove this disc, pass a long flat screwdriver blade through two openings in the nozzle and turn to the left (anti-clockwise), holding the body of the lamp firmly on the bench. Before fitting a new disc, thoroughly clean recess and remove any deposit from the inside of the valve box. Unscrew the needle and gland if there is any leak there, and clean and repack with asbestos yarn. A little glycerine on the packing appears to be an advantage. Place the disc in position, dip an asbestos washer in water, and screw the nozzle firmly down.
The wick inside the lamp filters the spirit before reaching the nipple and occasionally needs replacing. Remove the cap from the bottom of the lamp, and with a piece of thick wire flattened at one end and filed to a hook, push it up the tube and withdraw the old wick. The new one is simply put in its place and the cap screwed tight. The washer under the filled cap is of cork and rarely gives any trouble.
CHAPTER XIV
Making Blow-lamps
A Paraffin Brazing Blow-lamp.—The brazing blowlamp shown in [Fig. 70] was made at a total cost of less than 4s. The illustration is printed to a scale of about one-quarter full size. The lamp illustrated is not a mere experiment, as the writer of this description had a similar one in use for over two years, and during that time brazed hundreds of jobs with its aid.
The container is of tinplate, and adapted from a workman’s tea can. When purchased this will have a wire handle and two hinges, and these should be removed and soldered up. The handle shown at H is made from a strip of iron, 1⁄8-in. by 5⁄8-in. section, bent round to the shape shown and riveted to the side of the container. These rivets should be well soldered over inside to prevent leakage. The joint of the longer strip is shown at X. The lid should next be taken in hand, a 5⁄16-in. hole being drilled at one side close to the handle, to take an ordinary Lucas cycle valve. A leather washer is fitted inside, and also one outside under the lock nut, the latter being then tightly clamped up.
At E is shown the filling cap, the body part of which was taken from an old paraffin oil-lamp container, and the screw cap made at the local brass works; but this fitting can be obtained in a finished state from many model-fittings manufacturers. This is soldered to the lid in the position shown, a hole being afterwards drilled in the tin to suit it.
Fig. 70.—Paraffin Brazing Blow-lamp, the container being shown in section
The cock shown at D is an ordinary gas-cock, with a length of 3⁄8-in. outside-diameter copper piping screwed and sweated in beneath. This is passed through a hole drilled in the lid for its reception, and the base of the cock is then sweated in position. Note that the length of this pipe is such that when the lid is in place it clears the container bottom by 1⁄8 in.