Home Movies (1944)

• Fig. I — Traveling guide automatically lays film on processing reel with uniform spacing between loops, insuring against film damage from overlapping. AUTOMATIC REEL WINDING GUIDE Boon To Film Processors Is This Gadget That Spaces Film Accurately On Reel u ^LHCKER loading of developing reels in total darkness, automatic uniform spacing of film on the reel, and insurance against footage loss through overlapping of loops are just some of the advantages offered the home film processor in the automatic winding guide illustrated and described here. Until I devised this film guide, one of the operations I disliked intensely in home processing was winding the unexposed film on the developing reel. It is imperative to a successful job of processing that the film be wound carefully on the reel so that one loop of the film will not overlap another; also that the film be handled as little as possible to avoid finger marking and scratching. In winding the film on the developing reel preparatory to processing, it must start at one end and spiral around the reel with uniform and adequate spacing between each turn. The gadget pictured above does this chore more or less automatically. It consists of a threaded M carrier shaft upon which rides a guide spool over which the film passes on its way to the developing reel. As the reel is turned, drawing film from the camera spool, the guide spool, motivated by friction of the film, revolves and moves gradually to the right, guiding the film so it lays on the reel in loops uniformly spaced. Each loop of film is laid between the spacing pegs on the reel as accurately as if laid by hand. With my motordriven developing reel, a hundred feet of film thus can be wound upon it in about a minute and a half. The guide spool which travels laterally on the threaded carrier shaft is a regular 100 foot 16mm. projection reel. To provide additional traction surface, diameter of the core was increased by encasing the original core with one of wood. A split wooden disc 3 '/t inches in diameter was inserted and nailed in place as shown at B in Fig. 2. The spindle holes in the reel were filed to a larger diameter in order to HOME MOVIES FOR FEBRUARY accommodate a piece of Ys" brass tubing. This tubing forms a bearing for the reel and is soldered securely to the metal sides. The tubing also extends x/z" beyond one side of the reel and this provides for a spring and pin which engages the reel with the threaded shaft as shown in Fig. 2. This feature, shown in detail in diagram A, consists of a hollow rivet inverted and soldered over a small hole drilled in the tubing. A small brad or nail, filed to a point, is inserted through the rivet and extends below inside surface of bearing to engage groove in threaded shaft. A means for retaining the brad in place and allowing it to be withdrawn slightly in order to move the reel quickly back to starting position, is provided in a piece of clock spring bent, as shown in diagram A, and soldered to the extended tubing. The most exacting step encountered in building this device, is to calculate the correct thread or spacing of the spiral groove on the carrier shaft. To accomplish this, it is first necessary to count the number of turns that a 50 or 100 foot spool of film will make on the processing reel at hand, allowing uniform and adequate spacing between each turn. Spacing pegs, of course, should be provided on the reel, but they should not be mounted until after the automatic film winding guide is completed and exact location of each turn of film actually determined by practice. Done this way, the film, distributed by the automatic guide, will lay between the guide pins every time. A complete loop around my processing reel requires 5 1 ^ inches of film. Therefore, 100 feet of 16mm. film will provide 23'/^ turns of the reel. Since core of guide reel is 3 l/4 inches in diameter and my processing reel 16% inches in diameter, the guide reel would revolve five times to each complete revolution of the processing reel. Thus to determine the spacing of grooves in the spiral threaded shaft, the following mathematical formula was followed which will apply to any combination of processing reel and guide reel diameters: Diameter processing reel 16%". Circumference processing reel %\Vi" . Turns of film required for 100 feet of 16mm. film with allowance for stretching when wet — 24 turns. Dowel length: 24 turns of film times %" width equals 15" for film. 24 spacing pegs times 16" width equals \x/z" for pegs. Therefore 15" for film plus 1 yz" for pegs equals \(>Vi" length of dowel. Since diameter of the guide reel core was determined as approximately 1/5 the diameter of the processing reel, it was decided to make circumference of 62