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H u b e r t N. A l y e a Frick Chemical Laboratory Princeton University Princeton. N.J.. 08540
TOPS Projector Devices
These devices a r e cheaper and simpler t h a n the T O P S Proiectors alreadv descrihed,' a l t h o u a h t h e . y require a con. veniional overhead projector a s a n accessory. T h e TOPS Projector-Adaptor T h i s device.. laced on t h e 10 X 10-in. horizontal stane - of a n ordinary overhead projector, converts it instantly i n t o a vertical-stage projector, suitable for projecting T O P S experiments (see Fig. 1). ( P a r t s $60, labor 7 hours).
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Materials Aluminum strips: (1X) 20 X 4 X 0.3 em; (1X) 12 X 2 X 0.3 cm. Cements: Elmers Carpenters Wood-Glue; Black Magic Miracle Adhesive. ... ... . .
Glass lenses: (2X) plano-convex, 86 mm dia., 511 mm focal length. Hinges: (1X) 3.8 X 2.5 cm, 2-hole; (1X) 19 X 4 cm, 4-hole. Knob: thread. Mirrors: (IX) Glass, double weight, 20 X 17.5 em; (1X) glass, single weight, 13 X 8.5 cm; acrylic plastic, 'Is-in., 12 X 9 cm. Plastic: clear acrvlic. (2x1 10.6 X 9.6 cm. . 'In-in: Screws: Hanger-screw, about 1%in. long, one end a wood-screw the threaded machine serew. Machine screws with other end an lock-washersand n u b 6/lz threads: (4X) 3/s-in. (4X) 1-in. (8X) 1'14-in. Wood screws: ( I x ) lv4-in. 8, flat-head. (4X) 5/s-in. #8, round-head. (7X) S/s-in. #6, round-head. Wood: y4-in. plywood with birch finish: (IX) 22 X 19 cm; (2X) 25 X 2 cm. 1l2-in.plywood with hirch finish: (1X) 30 X 29 cm; (3X) 30 X 5.5 em; %-in. plywood: (1X) 12 X 9 em. Triangle: 8.5 X 8.5 X 12 cm; cut from a 2 X 4 stud. Construction Shelf 1) Cut the 30 x 29-cm %-in. plywood T-shaped, with its upright 21 X 9 cm, and its crosspiece 30 X 8 cm. 2) In the four %-in. plywood shelf-pieces, properly aligned, bore four '/a-in. holes; cement and bolt them together, with the front-piece under and theT-pieceoboue the twoside-pieces. Use the 1-in. %2 machine screws. 3) Under the side-pieces cement the two 25 X 2-em runners, each flush with the opening. Mirror Mounting I) Horran '2-in. holein the 12 X 2~maluminumstrip.1 rm fmm rhe luwrr end: and in the upper end rut a 5 X 0.5 rm slit Screw thm the s t r i ~into the mddle of the I d - h a n d runner (11 will EIII)PDI~ mirror). 5) Hinge the 22 X 19 cm 3/b-in. plywood mirror-support, exactly aligned, over the opening, using woad screws in the moveable piece, and machine screws inserted through %-in. holes in the shelf. 6) Screw the hanger-screw into the side of the mirror-support, swing the aluminum strip (item 4) over the hanger-screw, and attach and tighten the knob to hold the mirror-support a t any desired angle. I ) Firmly cement the 20 X 17.5-cm mirror to the 22 X 19-cm mirror-support, using the Black Magic Miracle Adhesive. ~
Lens-Box 8) Tomount the twuglass lrnsrs,rut an 87-mm dia. hole in the 10.6 X 9.6-cm '?-in. p l ~ w w dwirh , 0.5-ern rnnrgrns on three sides, and a 1.5-em margin on the fourth. 9) In this hole mount the glass lenses, flat sidesout, bolted between the plastic plates by four 1-in., %2 maehine screws as shown in Figure 1. 788 1 Journal of Chemical Education
Lens-Mirror Assembly 10) Down the 20 X 4-cm aluminum strip bore six pairs of 'Is-in. holes: two pairs 1and 6 cm from one end and four pairs 0.5,2,4, and 6 cm from the other end (the top). Space these pairs thesamedistance apart as the two holes in the small hinge. Note: ~t'vourpwjecu>r-ndapmris ru he uipd with se\,eral different models of pn,jector*, each requiring a different srtting ot the Imi-hur, mnkp thearranctmmt r h w n i n Finurr I Cut aslit in the aluminum strip [instead of holes]; insertihe machine screw end of a hanger-screw in the lens-box, and fasten it to the aluminum strip with the knob, as shown. 11) To the top end of the aluminum strip, bolt the small hinge smashed tostiffen it so that i t willsupport the mirror; use31a-in. machine screws. Bore two 3116-inlholes in the plastic mirror and halt it also to the hinge. 12) Using the two lower pairs of holes in the aluminum strip, screw i t to the side of the wooden triangle. 13) Screw the lens-mount t o the 2nd from the top holes on the aluminum strip. 14) Mount this lens-mirror assembly on the shelf, screwing the 1%-in., #8 screw into the wood triangle, after passing through a %-in. hole 3.5 cm from the hack of the shelf. 15) Glue the 12 X 9 cm %-in. plywood and the glass mirror to the hypoteneuse of the triangle; it should be a t a 45' angle t o the shelf. Only glue the upper edge of the mirror to the plywood; the heat of the projector lamp is extreme, and if the entire mirror is glued, strains will crack it. Focusing Place the assembled device on the horizontal stage of a lighted Overhead Projector, with its lens-box raised to clear the light-beam from the adaptor. Place a TOPS eell on the stage close t o the opening. Adjust the angle of the large mirror (also, if necessary to achieve exact alignment, swivel it in its hinge) until i t reflects a bright spot to the center of the face-up mirror. Swivel the triangle (finally cement in the best p i t i o n ) . If theTOPS eell projection is not upright, swivel the plastic mirror in the hinge. Final focus is achieved by moving the cell on the stage. (Screw the lens-box in that pair of holes that gives clearest focus). Project a t blackboard height to minimize keystoning. T h e TOPS Projector-Cradle This device, although cheaper a n d simpler ($15 for p a r t s nlus three hours labor) t h a n t h e a d a o t o r iust described. is less hesirable hecause (a) the Overhead kroj&or m u s t be iaid on
Figure 1. Projectw adapter
i t s back, which c a n n o t be done with b u l k y models, (b) t h e l a m p m u s t b u r n upright instead of horizontally; this m a y shorten i t s life a n d add considerably t o costs, (c) a hinged mirror m u s t b e cemented to each projector using t h i s cradle. Materials Aluminum strips: (2X) 16 X 4 X 0.3 cm; (2x1 35 X 4 X 0.3 cm. Cement: Elmers Carpenter's Wood-glue. Hinge: brass, ahout 3.7 em long X 2.5 cm wide. Plastic, acrylic: 8 X 2 X 0.7 cm. Plastic, acrylic, mirror: 12 X 8.5 X 0.5 cm. Machine screws with lock washers and nuts: (4X) %in., %/32 thread. (4X) I-in. ln/24 thread; (6X) bolts, 2-in., %in. thread. Rubber cups to fit the bolts. (6x1. Wood, 'Irin. plywood, birch finish: (1X) 30 X 30 cm; (1x1 16 X 2.5 cm; (1x1 16 X 7 ems. Construction
holes. 2) Similarly bend the shorter aluminum stripes in the middle a t 90°, and bore two 0.5-cm holes to match those in the longer strip.
Figure 2. Projector cradle.
opening (see Fig. 2). 4) I n this olvwood bore twooairs of holesoositioned tomatch those in the &minum strips,'and 6 cms in from the edge on each side. 5) With the ' 0 1 machine ~~ screws fasten the aluminum strips and plywood together. Bolt in the six 3/8-in. bolts, and slip the rubber '
enough tosupport the mirror. Bolt the mirror a i d plastic strip to the hinge with Y-in., =h2,machine screws. Adjustments
BE SURE YOUR PROJECTOR IS A MODEL THAT CAN BE OPERATED WITH THE LAMP BURNING VERTICALLY. Rest the projector in the cradle (see Fig. 3). You may have to cut out a small square on your shield to make room for the rod which supports the lens-box an your projector. Place a TOPS cell on the shelf, turn on the projector, hold the plastic mirror a t a 45' angle against the lens-box, and focus the cell by moving it an the shelf. When satisfied with its operation, cement the plastic t o the lens-box (usually acrylic cement will work in half a minute; otherwise use epoxy). If the TOPS cell projects at a slant, loosten two screws on the hinge, and swivel the mirror to correct this. Project a t black-board height to minimize keystoning.
Figure 3. Projector cradle mounted on overhead projector.
Volume 55. Number 12 December 1978 / 789
