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AN ALL-PURPOSE DEVELOPING DRUM
Photographs by LEWIS C. COOK
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ESPITE the reversal processing provided by leading film manufacturers for their products, there are a number of amateur film technicians who enjoy doing their own laboratory work. I am among that number.
Whether your effects are limited to exposure test strips, to developing positive titles, or to the complete reversal of black and white film, you will need some sort of easy method of bringing your films and solutions into and out of contact. The special feature of the design presented here — its retractable carrier for solution and rinsing trays — provides this.
Here are the key dimensions and data on its construction, all of plywood except the tray raising handle.
Baseboard and Sides: The base — % inch stock, cut 23 inches wide and 18 inches deep. The sides — % inch stock, cut 8 inches high and 18 inches deep; the risers to support the drum are fitted into holes cut in the sides (see Fig. 4) and extend to a total height from the base of 15Y2 inches. The sides are then reinforced with strips of % inch plywood.
Tray Carrier and Handle : The carrier — % inch stock for base, cut 21 inches wide and 17 inches deep; % inch stock for sides, cut 3V4 inches high and 21 inches deep. The handle — 1 inch pine stock, 4 inches high and 27 inches long, of which 9 inches extend beyond the carrier.
Developing Drum: The ends — % inch stock cut 17% inches in diameter. One half inch holes are drilled in their centers to accept brass collars which hold the drum shaft. This is a solid brass curtain rod, % inch in diameter by 26 inches in length. The slats — 48 slats, Vg inch thick, 1 inch wide and 17 inches long. They are attached to the end pieces with small brass screws.
Motor Drive: Two % inch wide pulleys, 5 inches in diameter; they are attached by setscrews to the drum
FIG. 1: Tray raising handle, key feature of author's developing drum design, is seen in down position. Note beveled edge.
and motor shafts. One fiber belt cut to order. One motor and one snap switch for outside control. The motor I used came from an old electric phonograph.
Motor Housing: The base — */2 inch stock, cut 6x/2 inches wide and 5V4 inches deep. The sides — % inch stock, cut to fit base. The top — % inch stock cut same as base. Note air hole cut in outer wall to cool motor in operation.
In operation, the unit is best used with at least three of the 16 by 20 inch trays. One of your three trays should be used for developer, the second for rinse water and the third for the fixing solution. With each of these filled and ready, their interchange is only a matter of seconds.
If your developing needs will not be large scale, you could economize all around by using 8 by 10 inch trays and scaling your design accordingly.
FIG. 2: The tray raising handle, smoothed out of 4 inch slab of pine, is hinged to baseboard for pivot of action. Paint is acid resistant.
FIG. 3: With handle in down position, solution tray carrier is installed. Note strap hinges on carrier which link with those on base.