Popular Mechanics/Volume 50/Issue 5/A Spanish-Desk Radio Cabinet
A SPANISH-DESK RADIO CABINET
By E. M. LOVE
PART II
THE BOX consists of a framework sheathed on the ends and top with 1/4in. three-ply figured walnut. (See Fig. 5.) Build each end of three stiles and two rails halved together, made from 1 by 2-in. pine. When the glue is dry, rabbet the front stiles 1/4 by 1/4 in., and smooth the joints.
The bottom is preferably made from 3/4-in. five-ply pine, but two widths of 1 by 10-in. solid stock, doweled together, may be used. It is dimensioned in Fig. 8. Assemble with the ends, bracing them at right angles with diagonal strips tacked on the edges. Reinforce the joints with two 3/8-in. dowels in the back stiles and one in the middle and front.
Cut a back upper rail from 1 by 2-in. pine, getting the length from the bottom between the stiles. Size the ends with glue so that they can dry while the front stile is being made. The latter is of walnut, dimensioned in Fig. 5.
Glue the back rail in place, laying a clamp lengthwise to hold it while a couple of dowel holes are bored in the corners. In the same way place the front rail, putting one dowel into the thick part.
Two walnut door stiles are cut from rough stock to sizes given in Fig. 5. rabbeted by 1/4 by 15/16 in. on one side and 1/4 by 1/4 in. on the other, and notched on the upper ends, to fit around the upper rail. Size the ends.
The shelf, of three-ply pine, is dimensioned in Fig. 5. The ends are marked by contact with the box end stiles and are notched around them. The front edges of the ends are flush with the 1/4-in. rabbets, but the front edge of the shelf is notched back 2 3/8 in. farther for the center section, terminating 7 1/8 in. from the ends.
Force the shelf into place with the underside 7 1/2 in. above the box bottom. Support the ends with 3/8 by 1-in. cleats, glued and brass-screwed to the box stiles. A couple of screws through the shelf into each cleat will suffice to hold it in place.
Joint the door-stile edges to allow for the end panel veneer to be glued in front. Set them with the inner rabbets 7 1/8 in. from the corner-stile rabbets. Put a dowel into each end. Glue a shelf-support cleat to the back edge of each stile, a stop strip along the bottom, flush with the rabbets in the panel spaces, and a walnut stop. 1/4 by 1 11/16 in., to the bottom, flush with the backs of the rabbets.
To complete the tone cliamber, fit three-ply partitions between the shelf and the top, the back edges coming flush with the shelf and the front ones being 1/2 in. back from the shelf edge, forming backing for the grill. The outer faces are 7 3/4 in. from the insides of the box-end frames. Temporarily nail the lower edges through the shelf, and the upper back corners with nails through the rail.
The front of the door desk and the two end panels are made from the same piece of walnut veneer, so that the grain will match straight through. Fit the panels tightly to their rabbets, making them a full 7 1/8 in. wide. Rabbet the stile edge on the back face of each, paring away the inner veneer and core until the front veneer is stripped. Glue in place, laying the box on its back, so that the panels can be weighted. The veneer must be held tightly to the stile edges with strips of wood well clamped. When dry, the projecting veneer is trimmed flush with these edges.
Next sheath the box. Glue a piece of walnut plywood to the top with the ends projecting 3/8 in. Secure with bolt clamps and any other means available, with the pressure well back to insure flatness. When dry, chisel away the under wood from the veneer projecting, cut the end-pieces, and glue them on, making sure that the veneer joins perfectly with the upper ends.
Glue triangular cleats inside the four corners of the tone chamber, and square cleats at the tops of the compartments against the partitions.
Make the arched upper section of the speaker grill of walnut plywood. (See Fig. 6.) The arches are centered 1/4 in. above the lower edge. Make two end posts of 1/4-in. walnut, 7/8 in. wide by 7 1/4 in. long, and a lower rail 1/4 by 11/16 in. by 1 ft. 6 3/8 in. A front rail, 1 1/2 in. wide and 1 ft. 8 1/2 in. long, an upper rail, 1 3/4 in. wide and 1 ft. 6 5/8 in. long, and a pair of stiles, 3/4 in. wide by 12 1/2 in. long, are glued over the others, as shown, to make the assembly. The front lower rail shows a 1/16-in. margin on the one behind, while the stiles give a margin of 1/8 in. on the posts. Fit caps, 7/16 in. wide, over the stiles, letting them projects 1/16 in., to correspond to the caps of the turned pilaster. Turn the latter as a single spindle, to be ripped down the center.
Stretch brocaded silk over the back of the grill, placing the design with respect to the arches and holding it in place with backing stiles and rails. 1/4 in. thick. Two 3/4-in.-wide stiles are added between the arches to carry the pilasters, which are nailed from the back with brads.
Fig. 8, Box End Frame; Fig. 9, the Desk Open; Fig. 10, Veneered Box with Glued-Up Desk Door
Install the grill in front of the tone chamber, with the lower front rail bearing against the shelf. Make two walnut side stops, 3/8 by 3/4 in., notch them to fit against the grill, so that the back edges line with the back of the grill rail and the bottom stop, and tack in place with three brads each. A stop at the top, 1/2 in. wide, completes this. Joint the front edges of the box and glue a 1/16-in. veneer over them, mitering the corners.
Glue up the door, using walnut plywood outside and in, with a center core of three-ply pine. Bind with wire, force wedges underneath, and add clamps to the edges. When dry, fit it snugly, screw on the piano hinge, and scribe the edges with a clearance at sides and top of 1/16 in. Glue veneers on these, to hide the plies, and surface with sandpaper.
The back of the case is closed with a cane panel, the frame being built of 1 by 2-in. pine, halved together at the corners. (See Fig. 5.) Wet the cane webbing before tacking on. Trim the edges and tack a flat molding in the rabbets. When dry, the cane will be stretched as tight as a drumhead, and the panel can be fitted into the box. Put a stop along the top, and secure the panel with four brass screws, so that it can be quickly removed to get at the set.
Cut down the hasp hinge as required, mortising it into the upper door rabbet, and mortise the staple into the door. Have them plated to match the plaques.
Half and quarter patterns for the brass plaques are given on page 830. Cut the plaques out and paint one side of each with asphalt varnish. Heat them to the smoking point, and allow to cool. Coat the reverse sides with wax. Trace the patterns onto the asphalt, afterward scratching through the paint with a sharp metal point. Build a dike around the edges with wax, to hold dilute nitric acid in the proportion of one to five, 1/4 in, deep. Some parts may be eaten through ahead of others, spilling out the acid; but the others will be so thin that they can be easily knocked out. Clean off the paint and smooth the rough edges. Give them an antique finish, or etch the surface lightly with acid, and coat with clear lacquer.
Fig. 12, Measuring Acid for Etching: Fig. 13, Squaring the Stand; Fig. 14, Trying the Back Panel
The old Spaniards were fond of red-velvet backing under the plaques, but velvet is a dust catcher, and a coat of magenta lacquer will be found much more satisfactory, or the finished wood itself will give a good effect. Use small round-headed escutcheon nails to attach the plaques.
Sandpaper the cabinet carefully before filling. The amateur will find oiling and waxing the easiest finish to apply, and it is much to be recommended. Repeated oiling, from time to time, combined with "elbow grease," will result in a fine finish, more beautiful from an artistic standpoint than the gloss of polished varnish.
Fig. 16, Carving the Flower Ornaments; Fig. 17, Shell Ornaments in Process of Carving: Fig. 18, Outlining the Carving
For the mechanic who has no lathe, and does not wish to bother with an improvised one. the stand design for flat stock is given in Fig. 11. The upper rails are cut from material 1 3/4 in. thick and 3 1/2 in. wide, and the legs from stock 6 1/2 in. wide. Stock 5 in. wide is required for the lower rails, and 5 1/2 in. wide for the brackets. The upper rails are attached to the legs with double tenons. Saw the parts roughly to profile.
MATERIAL LIST
For Cabinet
- 2 pieces, 1/4-in. three-ply figured walnut panel veneer, good one side, 18 in. by 6 ft.
- 1 piece. 1/4-in. three-ply figured walnut panel veneer, good one side 24 in. by 4 ft.
- 1 piece, 3/8-in. three-ply pine panel veneer, good one side, 36 in. by 5 ft.
- 1 piece, 3/4-in. five-ply pine panel veneer, good one side. 17 by 36 in.
- 1 piece, 3 by 3 in. by 5 ft., rough walnut.
- 1 piece, 2 by 2 in. by 2 ft., rough walnut.
- 1 piece, 1 by 6 in. by 10 ft., rough walnut.
- 1 piece. 3 by 3 in. by 3 ft., pine or fir., S4S.
- 1 piece, 3 by 4 in. by 4 ft., pine or fir, S4S.
- 5 pieces, 1 by 2 in, by 8 ft., pine or fir, S4S.
- 1 piece, cane webbing, 18 by 34 in.
- 1 qt. liquid glue.
- 4 ft. 1/4-in. hardwood dowel.
- 6 ft. 3/8 in. hardwood dowel.
- 1 pt. light oak filler.
- 2 ft. piano hinge.
- 1 heavy iron hasp and staple.
- 2 1/2 sq. ft. No. 21 gauge, sheet brass.
For Flat Stock Stand
- 1 piece, 2 by 7 in. by 10 ft, rough walnut.
- 1 piece, 2 by 4 in. by 3 ft., rough walnut.
- 1 piece, 2 by 5 in, by 2 1/2 ft., rough walnut.
- 1 piece, 2 by 6 in. by 5 ft., walnut. S4S
- 1 piece, 1 by 6 in. by 3 ft., pine, S4S.
The radio installation is made entirely from the back, but the grill must be removed from the front.
Full-sized blueprints of the half and quarter patterns for the brass plaques may be obtained from Popular Mechanics radio department, 200 E. Ontario St., Chicago, for 25 cents to cover cost and packing. Specify blueprint No. 137.
New Speaker Employs Double Diaphragm
Top. Left, Speaker Installed in Cabinet with Tapestry Front; Right, Rear View; Below, Construction Details and Front View of Large Diaphragm
The speaker shown in the illustration consists of two vibrating diaphragms, tightly stretched upon two frames, the center point of each diaphragm being connected to the other. The pin of the reproducer unit is fastened to the balanced center point. The speaker may be used with all 210 and 171 power amplifiers and is suitable for all types of amplifiers including the 50-watt power type. It is said to give a uniform response from 50 to 10,000 cycles, reproducing with practically equal facility all notes from that of the bass viol to the highest note of the piccolo.
Homemade R.F. Choke Coils
Radio-frequency choke coils are a necessary part of most modern receivers. These coils are not costly, but if you prefer to make your own, cardboard tubing from tissue rolls is about the right size. Shellac the tubing and allow it to dry thoroughly, then place it in a warm oven for half an hour. Two holes are punched in the tubing, 3/4 in. from the starting end of the coil: then the wire is threaded through these holes to anchor it, leaving an end about 6 in. long. For standard broadcast wavelengths wind about 250 turns of No. 32 d.c.c. wire on the tube and secure the finishing end through two small holes as at the start. Both ends of the coil are then connected to two small binding posts or Fahnestock clips at the finishing end, the starting end being brought up inside the tube. The mounting block consists of a piece of 1/2 by 1/2-in. wood rounded at the ends to fit into the bottom of the tube. This wood strip is drilled at the center to take either a wood or machine screw for mounting the coil upright on the subpanel or baseboard. Choke coils of this type may be used also in short-wave transmitters, but in that case the wire should be No. 26. The number of turns necessary for wavelengths below 100 meters should be about 130. No. 26 wire is of sufficient size to carry the plate current of a 500-watt transmitter, yet small enough so that the necessary number of turns may be wound on the tube.