About the least expensive I have seen a 400-watt Cool Tube selling for is roughly $250.00 plus shipping. There are a number of different plans to be found online of how to make your own for very little expense.
　
Below are instructions from one such home made Cool Tube. I am not saying it is the best home made one to be found or is average or the worst, it is only an example of what can be done. You can Google for more options.
DIY: Best Cool Tube
I had to share these instructions...the best I've found!
Clean, Easy Cool Tube Tutorial
<HR style="COLOR: #258c25" SIZE=1><!-- / icon and title --><!-- message -->(*Note - This is of course, by no means a new idea. This is simply meant to be an informative tutorial based on my experience while searching for a
cool tube solution. I was unable to find any
detailed or
clean instructions on how to make a
cool tube using a Pyrex bake-a-round. They all ommited small details or used a ton of duct tape, random scraps, etc. This is intended for those who want a durable, clean, easy to assemble piece of equipment for thier setup. )
Clean and Easy Cool Tube
This is a detailed tutorial on how to put together your very own
cool tube. You can assemble one of these in about 20 minutes. This is based on a 150 watt HPS, but may be adapted as needed.
What You Need:
1 x Pyrex Bake-A-Round
tube (long discontinued, but available readily on EBay and in classifieds, Flea markets etc surprisingly common) - $10-15
1 x pair of Café Rod brackets (hardware store, where window fittings are located) - $1.50
1 x Ceramic medium or mogul lamp base with standard mounting hole - $0.99
1 x 1-1.5 (approx) hose clamp - $0.80
1 x 3.5-4 (approx) hose clamp - $1.00
2 x 4.5-5 (approx) hose clamps - $2.50
1 x roll of self adhesive insulting foam for hot water pipes. - $2.50
1 x #6 32 x 3/8 (machine screws with nuts) - $0.99
1 x multipurpose (including glass) glue or epoxy (optional) - $3.00
1 x 400°F small
tube of silicone sealant - $2.50
Your HPS/4 duct system N/A
Step 1:
Collect your café rod brackets, lamp base, and screws.
Remove one of the café rods and bend into roughly the shape illustrated in the next photo (you may need a something to help such as a pair of pliers).
Attach the café rod to the lamp sockets mounting hole using a screw and nut.
Connect the wires from your power source line to the lamp socket. The white wire should connect to the silver screw, and the black wire to the brass / darker screw (this is standard color coding). I used a little bit of solder for good measure. Leave the ground wire (green) unconnected for now, ideally left a little longer than the others.
Cut and bend the remaining café rod into three pieces with tabs on the end as shown. The longest/middle section should measure 1&1/8 on each (medium) or 7/8" (mogul). The other sections are of negligible length, but around ½ is good. These are your spacers.
Fasten the spacers to the lamp socket as shown. Use your epoxy or glue if desired in addition to the clamp to make sure everything is firmly in place.
Step 2:
Hang your bulb assembly over the end of the Bake-a-Round. You will notice that there is a slight bit of play between the spacers attached to the socket, and the inner walls of the
tube (if you measured correctly and dont have an oddly sized socket). This is deliberate and is to account for possible thermal expansion in the metal. Fitting the spacers firmly could result in a cracked or broken
tube!
Place the bulb in the socket and clamp the hook hanging over the side of the glass
tube with the ~4 Clamp. Tack the hook and clamp with epoxy/glue for added strength (The glued clamp can still be popped off, so dont worry too much about how you will change the bulb).
Step 3:
Wrap self adhesive insulating foam around each end on the
tube as shown (or only one if you are using exhaust only). This will allow 4 duct to fit very snugly to the
tube (which its self is 3 ¾ O.D.), and will also act as a gasket/seal when clamped.
Thread wiring through the ducting, attach the ducting to the
tube, and clamp in place. Finish with silicone sealant if desired. Connect the ground to the duct or the café rod hook.
Add an optional reflector made from unclosed rigid duct (you can find this in your hardware store its a piece of sheet metal with a snap together seam that hasnt been connected). Simply cut to length, cut flanges a half inch from the ends, and clamp those to the duct/tube. Hang your lamp with light chain available from your hardware store by the foot. The chain attaches under the clamps on the duct. Youre done!
