T. B. Meyer
The following, with accompanying diagrams, gives full directions for making an electric flash sign, such as is used extensively at the present time in the larger cities, principally for advertising purposes.
Heretofore electric flash signs have been confined to the more expensive apparatus, such as are seen on the theatres and buildings requiring an expensive flasher and motor to operate the same. The sign here described is used more particularly for window displays though the principle involved may be applied as well to larger signs.
We will confine our attention to one consisting of an ordinary 1 1/2- picture frame moulding, taking an 18 x 24 in. glass or sign. This, allowing for the usual £ in. rabbet in picture frame moulding, would make our sign over all 20 1/2 x26 1/2 in. Such frames may be procured at any picture frame store, to order, for from 30 to 60 cents, depending, of course, on the wood selected and finish of the moulding. A frame may also be made of moulding used for interior finish or dados.
There are two methods by which we may complete the front of our sign: By employing an 18x24 heavy cardboard with the desired lettering painted thereon; white board with black letters will answer, though white letters on black background are to be preferred, or by having the wording painted on glass in stippled white in order to insure transparency, and filled in all around with black. The latter will cost more but makes by far the better appearing sign.
If cardboard is used, a plain glass front must also be used to prevent the cardboard from buckling. The lettering is punched in outline as shown in Fig. 1; the holes being spaced about 1/4 in. apart; on the back of cardboard are then pasted various colors of tissue paper, which give a varied color effect from the single plain lamp placed behind.
As a support for this lamp, as well as a reflector and means of keeping out other light, we next build a semi-circular box, as shown at Fig. 2. This consists of two pieces of | in. soft wood, 24 in. long by | in. at the ends and 6 in. at the center. Fig. 3. These are fastened together by two strips of wood 3/4 in square 16i in. long, with ordinary finishing nails. Next, as a backing for the box, fasten a sheet of 20 x 28 tin with carpet tacks to the framework just completed, tacking down well over the curve ab and cd, Fig. 2, and the sides of the strips s at the end of the frame-work. Paint the outside black with thin asphaltum or black paint, and we then have a light-tight box, which may be fitted in to the frame with hinges at bottom to swing open, and a catch hook and screw eye at the top, taking care to allow for the thickness of card-board and glass.
Our next step is to make an electric thermostat by soldering or riveting together a strip of brass and of soft iron, 1-16 in. thick, 1/2 in. wide and 4 1/2 in. long. Drill two holes 1/2 in. apart, at one end, large enough to clear a 6-32 machine screw, and a third at the other end, tapped for a 6-32 machine screw. This is our contact making screw, and should be brass with a 1-8 in. piece of No. 16 or No. 18 platinum or hard silver wire soldered to the end of it. Bend the two-metal pieces slightly at a point 1 in. from the two-hole end.
Then cover between holes with five thicknesses of paraffined paper, shellac down to- hold in place, and wind with about 33 ft. of No. 36 single silk covered German silver wire, first soldering end directly to thermostat at E, Fig. 4. The winding should be 3 in. in length and clear the holes in the two-metal strip by 1/4 in. at either end. Care must be taken that the wire rests only on the waxed paper.
Next fasten this thermostat to an insulating base of slate 4 1/2 in. long by 3/4 in. square, with two 1 6-32 in' round head machine screws, with nuts to match on the underside and place a contact screw with 1-8 in. square of platinum or hard silver soldered on its head in the other end of base, so as to come directly under the contact screw in the thermostat. See Fig. 4. The lower contact screw should also be provided with nuts underneath, and the upper one in thermostat with check nut for adjustment.
Connect, as shown in Fig. 4, the brass strip of thermostat on top, and with right hand end wire under screw head at A. The insulating base B, Fig. 4, may now be fastened by screws and nuts to the bottom of the box at C, Fig. 2, or by two 6-32 machine screws through holes at B to a metal angle carrying the lamp and fastened by screws and nuts to the tin back of box. This angle is drilled and tapped 6-32 to take ordinary keyless receptacles and lamp, the latter being placed so as to come near center of back of box. See Fig. 5. Connections are made as shown in Fig. 4, the cord of from 6 to 10 feet being fitted with the ordinary plug and coming through an insulating porcelain or glass bushing in the tin to the lamp and thermostat. Thermostat should be placed with B side down in order to bring the adjusting screw D to the front, and if put on the. wood bottom of the box should have apiece of thick asbestos cloth under it. The cord E should be what is called window cord in preference to the ordinary lamp cord, and may be had for about four cents per foot.
The apparatus being ready, see that the point of adjusting screw D comes within 1-16 in. of contact A, before turning on the current. The lamp will burn dimly at first, and about 60 to 80 seconds are required before the the thermostat becomes sufficiently warmed up to operate. The period of flashing may be varied by the screw D; setting it closer to A causes the sign to operate more slowly, while increasing the distance between the two contacts brings about a quicker flashing.
Several thermostats and as many different colored lamps may be placed in one sign, producing a beautiful and ever changing effect. The wiring for three lamps of different colors is shown in Fig. 6. The total cost of material should not be over $4; the sign retails for from $10 to $15.