After we laid out our measurements on our board, we determined the final dimensions. (At the end of the series, we'll provide full cut sheets and dimensions.) To cut out the sides, we clamped a straightedge (extra 1x2) and used it as a guide so we could use a router and make the cuts. (We were limited on our selection of router bits, so we had to improvise a bit.)
A router makes quick work of the cuts. If you don't have one, you can get away with a circular saw or jig saw.
We clamped the original on top of our second 14-inch wide board and duplicated and routing the edge onto the second board.
For our enclosure, we'll need to have a solid structure. Once the internal lenses are placed, we'll finish up the top support structure. For now we're doing the essentials. We cut the front panel and the three rear/lower pieces on the table saw. We eyeballed the angles and managed to get a decent fit for the panels. We've got plenty of plywood, so we just went for it with the cuts.
We clamped our pile of boards together to test fit the panels and get a feel for the final product. If it doesn't work out, at least we'll have a coffin for next Halloween.
Imagine that the square is the LCD panel. It'll rest on a spacer block, and sit in the channel of the frame we made earlier. We'll be mounting the display a little bit higher, but this stage is all about verifying and developing the design.
We need to make the front port for the projection lens. The lens will be on an internal slide, so we'll need a hole that it can freely move through.
Since we've got a 5-inch hole saw, we marked the center of the front panel and chucked it onto our drill press.
Back in the enclosure, we've got plenty of clearance for the lens (but not too much).
For focusing, the projection lens needs to move back and forth. Because it's such a large piece, we decided to use a set of 16-inch drawer slides from Lowes. The lens will be mounted in a carrier, and the slides on the sides of the enclosure.
The slides are about 1/2-inch thick, so we cut down one of our plywood pieces to 16 and 1/2-inches wide on the table saw.
The body of the lens is 111mm wide, so we need to cut a custom hole for the lens carrier. To cut the hole, we'll use a speaker box building trick. We marked off a 56mm radius on our router base.
Then we drilled a 1/4 inch hole at our mark with the drill press.
And repeated it on the center mark of the carrier board we cut down.
About half way, we pulled the router and checked our radius. It looks perfect. (We used a 1/4 inch router bit as our pivot.)
Finished up, we've got a decent mounting hole for our lens.
To center the lens, we measured the distance from each edge to the side of the carrier board. Then we moved the lens until both measurements matched.
For later, we marked the location of each mounting hole in the edge of the lens. Once we pulled the lens, we added more definitive marks so we can find them later.
A test fit of our carrier reveals that we'll be pretty tight on clearance to the upper and lower edges of the case. (We'll be filling them in with 1/4-inch birch plywood.) We trimmed off about 3/8-inch from the top and bottom of the carrier on the table saw.
To mount the carrier to the drawer slides, we cut a pair of 6 inch long pieces and a pair of triangles to keep them squared up.
Since it'll be carrying weight, we drilled holes for the 2-inch drywall screws we'll use to keep things together.
Then we hit the edges with some decent wood glue.
Once everything was glued and screwed, we left it to sit and dry. The screws act as clamps while the glue dries. We used two screws for each side and two screws for each triangle to pull everything together.
Moving to the back of the projector, we need to build a mount for the mogul base and the bulb. We'll need the mount to allow fine alignment of the light source, but we should mount it in approximately the correct location.
The left base came with our ballast. The right came from Lumenlab. The decided to use the Lumenlab base because it came with threaded brass inserts for mounting. Too bad, we liked the screw terminals built into the other base.
We picked up some 1-1/2-inch 8-32 screws to hold the base to our mount.
We cut a 3 inch square, a 3 x 4 inch rectangle and a 3 inch triangle our of our 3/4 inch plywood.
We glued and clamped the mount together and left it to dry overnight. The blue shop rag kept it from being glued to the table top.
To mount the base, we measure the mount holes and drilled a pair of slots into one side. The slots will let the base be moved to align the bulb in one direction. (We can also add shims here if we need to achieve a certain angle.
Here's the mogul base, screwed down to our mount. For the final build, we'll add a pair of washers.
Next time we'll finish up mounting everything and we might just get to test fire the system. We've still got plenty of work to do on the cooling system, internal lens and reflector mounts. Oh, then we've got a bit of hardware hacking to do to really tie the system together. Watch out, we're nearing completion!