The Boy Mechanic Part 114

** Drying Films [412]

The drying of photographic film in full lengths without scratching or curling is quite difficult. Various devices are used to keep the film straight, and

[Ill.u.s.tration: Pins Keep the Film Straight]

push pins or thumb tacks are supplied with almost all of them. The ill.u.s.tration shows a simple and inexpensive device constructed of common wood clothespins without any metal pins to come in contact with the film and cause rust streaks. A pair of pins are fastened at each end of the film by pushing one pin over the other which in turn is clamped on the film. A string tied to the heads of one pair of pins provides a way to hang the whole on a nail. The lower pair of pins makes a weight to keep the film straight.

--Contributed by J. Mac Gregor, Montreal, Canada.

** Grooved Pulley Made from Sheet Tin [412]

A grooved pulley which will run true and carry a round belt may be made without the use of other tools than a compa.s.s and pair of shears, with a drill or punch for making two rivet holes.

Layoff a circle on the tin, of the diameter desired for the bottom of the groove. Then layoff a concentric circle of 1/4 in. greater radius. Cut out along the lines of the large circle. On the line of the small circle mark with a p.r.i.c.k punch or nail a series of slight dents, about 1/4 in. apart, all the way around. Now make cuts from the line of the large circle to these dents, stopping when the shears give the little "click" on entering the dent. Bend the little tongues thus formed alternately to the right and left, then by shaping them with some care you will have a good running surface for the belt. It will not make any difference if there are more tongues on one side than the other, or if they are not equally s.p.a.ced, within reason.

For the hub, solder or rivet a "handle" across the center hole and drill a hole through it of the same size as the center hole. With the help of solder a grooved pulley which will answer almost every experimental purpose may be made, and it is remarkable with how slight care a perfectly true wheel may be made in this manner.

The same principle might in some way be applied to gear-wheels, for light and temporary use.

--Contributed by C. W. Nieman, New York City.

** An Emergency Gla.s.s Funnel [412]

[Ill.u.s.tration: Cutting a Funnel]

Secure a gla.s.s bottle having a small neck and tie a string saturated in kerosene around the outside at A and B as shown in the sketch. Light the string and allow it to burn until the gla.s.s is heated, then plunge the bottle quickly into water. The top or neck will then come off easily. The sharp edges are ground or filed off smooth. This will make a good emergency funnel which serves the purpose well for filling wide necked bottles.

--Contributed by Jos. W. Sorenson, Everett, Wash.

** An Electrical Walking Stick [413]

A cane that will produce an electric shock when shaking hands is one supplied with the electrical apparatus shown in the sketch. An ordinary cane, 1 in. in diameter at the top and having a metal band A, is bored about 8 in. deep, to receive the battery B and induction coil C. One of the electrical connections is through the metal tip D to the earth, the other is through the

[Ill.u.s.tration: Battery and Coil In Cane]

metal band A when the push b.u.t.ton E is pressed.

The one using the cane merely holds the metal end D in contact with the earth and while shaking hands with a friend he pushes the b.u.t.ton and starts the coil in operation.

--Contributed by Stanley Radcliffe, Laurel, Md.

** Convenient Shelf Arrangement [413]

A convenient device for crowded shelves and cupboards is shown in the accompanying sketch. Halfway between shelves A and B is installed a second shelf C which is only half as wide as the other shelves. This

[Ill.u.s.tration: Shelf]

provides a convenient place for small articles and utensils, while in a china closet it furnishes a splendid s.p.a.ce for cups, sauce dishes or other small pieces. It also adds a neat and pleasing appearance.

--Contributed by E. M. Williams, Oberlin, Ohio.

** A Shoe Sc.r.a.per [413]

On steps of public buildings, shops and dwellings is usually found some sort of a mud sc.r.a.per for the shoes. These remove the mud from the sole of the shoe and leave it on the edge and sides. The sc.r.a.per shown in the sketch is of simple construction, and removes the mud from the soles and

[Ill.u.s.tration: Sc.r.a.per of Thin Steel]

sides of any size shoe in one operation. The sc.r.a.pers spread and bring pressure to bear on all sizes. The side sc.r.a.pers must be made of metal that will spring. The standard is of heavy sheet metal with the thinner strips riveted to the projecting uprights at the ends.

** Fastening a Shade to a Roller [413]

Tack the shade A in the usual manner and roll it as far back as possible

[Ill.u.s.tration: Fastening a Shade]

and while in this position apply an ample quant.i.ty of glue near the tacks, as shown at B. A shade attached in this manner will not come loose from the roller.

** Vegetable Slicer [413]

The slicer is made of a knife blade, screw and pin handle. The screw is soldered into the end of the knife blade. As the screw feeds into the vegetable

[Ill.u.s.tration: Slicer In Vegetable]

or fruit, the blade will slice it in a curl of even thickness.

--Contributed by H. C. Roufeldt, Toledo, O.

** How to Make an Etched Copper Picture Frame [414]

Secure a heavy piece of copper about 8 or 10 gauge, cut to 7 by 7-3/4 in. Make a design on a piece of paper. The accompanying sketch offers a suggestion.

[Ill.u.s.tration: Etched Copper Picture Frame]

If the design is to be symmetrical, draw a line down the middle of the paper, make one-half the fold and trace the remaining half by placing a piece of double-surfaced carbon paper between the halves. Fasten this design with a little paste on the copper at two of its corners and trace it on the copper by means of the carbon paper.

Remove the paper, and, with a small brush and black varnish or asphaltum paint, cover the part not to be eaten by the acid of the bath into which the metal is to be immersed. Two or three coats will be necessary to withstand the acid. The conventional trees, the border as shown in the ill.u.s.tration, and the back are covered with the varnish or asphaltum.