dburgette - find a local weld shop, especially one that builts trailers... lots of scrap pieces!!! I have a good friend that has a metal shop... he helps me with my projects that my little Mig won't handle (plus he's just got some awesome metal tools...he and I together have a thousand ideas for building projects...if we just had an investor!!!).
As far as the size, I have 3 3/4 inch pipe size inlets, one with a ball valve. my current basket is 15" dia and almost 20 inches tall (don't need it that tall...it came off a propane heater I canibolized) I can put 11 lbs (half a big Kinsford bag) and not come halfway up. With 11 lbs of charcoal and as many as 12 2" dia hickory chunks, I can get this up to 225 degrees in about 20 minutes, put my meat in, cap one inlet completely, leave one open, and set the ball valve about 1/3 shut and run at 225 for 16 +hrs...I know that I can, because I just shut it down from a smoke I did last night with 40 lbs of butt; meat on at 8pm, checked it every 30 mins for a while the hourly then at 2 went to bed...that UDS never varied more than 3 degrees either way. This morning I pulled the meat off after 12 hours, left the smoker going and just shut it down at about 4 pm today temp just starting to drop off (it was at 190) THATS 20 hrs!!!...still a bit of charcoal in the basket!!!!
As far as the size, I have 3 3/4 inch pipe size inlets, one with a ball valve. my current basket is 15" dia and almost 20 inches tall (don't need it that tall...it came off a propane heater I canibolized) I can put 11 lbs (half a big Kinsford bag) and not come halfway up. With 11 lbs of charcoal and as many as 12 2" dia hickory chunks, I can get this up to 225 degrees in about 20 minutes, put my meat in, cap one inlet completely, leave one open, and set the ball valve about 1/3 shut and run at 225 for 16 +hrs...I know that I can, because I just shut it down from a smoke I did last night with 40 lbs of butt; meat on at 8pm, checked it every 30 mins for a while the hourly then at 2 went to bed...that UDS never varied more than 3 degrees either way. This morning I pulled the meat off after 12 hours, left the smoker going and just shut it down at about 4 pm today temp just starting to drop off (it was at 190) THATS 20 hrs!!!...still a bit of charcoal in the basket!!!!