How to Build the Projection Trays

To build the trays to support the slide projectors, one over the other, you need to cut lumber to the following specifications in Figure 1 (metric conversions at the bottom). You will need:

• 1 Top tray
• 1 Bottom tray
• 2 Side supports labeled "A"
• 2 Side supports labeled "B"
• 2 Pivots labeled "C"
• Copious quantities of "L" brackets, with screws short enough for the wood thickness you've chosen.

The side supports can be purchased in 6 inch widths, so you'll only have to make one cut. To make the two side supports "A", start with a 24" piece of lumber and drill the hole in the exact center, as in Figure 2. I used a doorknob cutting attachment on my drill.

Once the hole is cut, cut the board in half through the hole. Save the piece you cut out as it will be the pivot "C". You will need to waste a small piece of the same type of wood to make the other pivot "C" piece.

The two side supports "B" do not have holes cut in them. Assemble the pieces as shown in Figure 3.

Screw two "L" brackets on each side support "A" on the end away from the semicircle hole. Then, centering the side support on the edge of the Bottom Tray, as shown, screw the "L" brackets in place on the tray.

Approximately 2 inches from the top of the side support "B", center and screw the pivot "C" into "B". It may help to pre-drill the hole first. You may also want to use several screws- you don't want this piece to rotate around the screw.

Screw two "L" brackets on each side support "B" on the end furthest from the semicircle hole and on the opposite side. Then, centering the side support on the edge of the Top Tray, as shown, screw the "L" brackets in place on the tray.

Finally, set the Top Tray into the side supports of the bottom tray, add the projectors, and you have the best possible way to project 3D without mirrors (a method I have not experimented with), as shown in Figure 4.

This is very portable, and allows you to correct for vertical misalignments quickly and easily. You get the hang of adjusting them in a few minutes, and if you show the same slides over and over, you can usually predict how much to adjust them and do so without causing your audience stress.

The following table is an approximate conversion of the English units in the drawings above.

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