raygun said:I made one years ago and it still works great! just need to change out the carbon/kitty litter crystal mix every 4-6 mo. to keep in top performance. Costs are minimal its like $20 for carbon every time i change and the 1 tub of kitty crystals will last at least 3-4 changes so over a year at a 1:3 ratio kitty:carbon
Mine is 6" in diameter and a little under 2' long basically extends from my fan intake to the edge of my cab. You could make it 8" in diamerter just as easily for extra filter power as well.
here is an IC mag link to the model i used to make mine.
http://www.icmag.com/ic/showthread.php?t=29402
I made the same scrubber and I agree it works well. If I had it to do all over again I would probably just buy one. I've got my scrubber up in an attic crawlspace. Crawling through the insulation and hauling out the scrubber to replace the charcoal is a nasty job. I suspect that the that the Can filters use more carbon and last longer than the homemade ones. If you have a filter location that is easy to access I would definitely recommend making your own.