How do I build my own Cool Tube?
Keep in mind that the full list of materials you will need depends on the type of glass you get and the configuration you're looking to build. Here's the materials list with some pictures and approximate pricing:
· $3.99-- Glass, either 4" Pyrex tube (approx. 12" long, 4” diameter) or "hurricane" lamp glass ($3.99 at Hobby Lobby, is 11 3/4" long and 4 5/8")
· $2.99-- 4" H/C venting starter collar
· $4.50-- 5" to 4" venting pipe reducer (for use with hurricane glass only)
· $3.00-7.00-- High-temp foil tape
· $5.00-- Thermal pipe wrap (looks like woven fiberglass tape with no adhesive)
· $8.00-- 4" aluminum "dryer" ducting (hanging configuration)
· $2.00-- 1/2 wood screws (box wall mount only)
· $3.00-- pop rivets or small sheet metal screws
· 4" (dryer ducting and/or Pyrex tube only) and/or 5" (hurricane glass only) hose clamps
· "S" hooks (for hanging)
a. Hurricane glass tube
When working with the hurricane glass "chimney," the irregular shape needs to be overcome so that it can be attached it to a reducer collar that will make up one end of the fixture. You may attach a reducer collar to a single end if you want an open ended design, or you can attach one to each end if you will be running ducting to both intake and exhaust ports.
The graphics concentrate on the exhaust end to which the bulb socket is also anchored. On this end of the glass (at the narrow "throat") numerous wraps of thermal pipe wrapping are wound around the glass and secured with a couple of wrappings of foil duct tape. The wrapping should build up the throat to the same diameter as the opening in the glass - where it snugly fits inside the larger end of the reducer.
This will allow us to use a 5" hose clamp to secure the edge of the reducer collar to this tape wrapped "cushion." (Note: you can use foil tape alone for building this "cushion" but the thermal wrapping makes for a neater seal, and is less susceptible to heat. Also, if a hose clamp isn't available, the reducer can be secured to the glass with foil tape.
If you use a hose clamp, you will need to make some 1" slits in the edge of the reducer collar the glass fits in to allow the hose clamp to compress it enough to hold the glass securely)
Mounting the socket inside the tube
In the graphic, a length of pipe strapping bent in a "U" shape is used to hold the socket far enough inside the glass to place the bulb roughly in the middle of the glass. This glass, $3.99 at Hobby Lobby, is 11 3/4" long and 4 5/8" at each end. Notice this glass is symmetrical. Don't try to use the asymmetrical hurricane lamp "chimney's" available at Lowe's or HD; they're too small and aren't shaped in a way that permits good air flow.
The socket is either screwed or pop riveted to the bottom of the pipe strap "U." My light was made from a 150w HPS security light which used a "medium" base socket; this socket has two little screws in it that more or less lined up with the holes in the strapping.
As for the mogul base sockets used with bigger lamps, I don't know what they have on the bottom of them so you may have to improvise a solution for mounting them. The ends of the strap are bent around to "clip" over the edge of the glass and then secured with a couple of wrappings of foil tape. If you'd like, a more permanent mount can be had by drilling a couple of small holes in the tapered throat of the reducer and attaching the ends of the strap with a couple of pop rivets.
Running the wires
The wires from the socket can be either run through your 4" ducting which will attach to the other end of the reducer or you can drill a hole in the tapered part of the reducer to run the wire out of the fixture to the ballast.
Here's how I actually have it done in my box. There's no venting, it just mounts to a 4.25" hole in the side of my flowering chamber via a starter collar which fits snugly inside the 4" side of the reducer collar. I've got them held together with four pop rivets for a permanent connection. The tabbed end of the starter collar fits into the hole where the tabs are bent around the edge of the hole and anchored with wood screw to the box wall. (In my box, on the other side of this wall is my utility room with a 4" 115cfm computer case fan sucking out the back of it.)
One could just as easily connect another reducer collar onto the other end of the glass exactly as the first side was with "S" hooks for hanging from above. This fixture could then have both intake and exhaust from outside the box.
Originally this is what I would have preferred to have, but as my flowering chamber is only 2'Dx2'Wx3'H, the wall mount actually did better for me.