Back when my son-in-law was dating my oldest daughter, and was 17 at the time he said he wanted to learn how to weld. So we rounded up some old fuel tanks, scrap iron and some other parts and pieces and the tutorial began. My son, 10 at the time had already been burning a few rods on occasion and was ready to put our go-cart project on hold to let Mike learn how to weld. What you are looking at is a project 95% welded by two beginners...but I have to take credit for the layout. That way you know who to blame when you see something funky !!
Taking 1/3 off the bottom of the round tank and the top 1/3 off of the oval tank allowed us to lay out a larger tank kinda shaped like a light bulb. The oval fuel oil tank was a lot longer, so we sliced it in half and slid them together to match the 52" length of the round tank. The plan was to use the wider round area for the rotating hog and the narrower tank for the heat. The three smoke pipes have individual dampers and are adjustable to assist in evening out the heat distribution...more on that later.
A salvaged cast iron boiler door from a recent tear out at a local college was a perfect fit for the firing end. The small door was for combustion air to the gas boiler flame and does its same duty providing air to the briquets in the first third of the heat chamber. Note the 3 x 3 x 1/4" angle iron skids. No flats to fix. Hook on with a small tractor and move into location. Of course a couple years later I did fabricate a roaster-specific trailer for it, though its no longer on it now...(another story). Note the cooool three piece 90 degree elbows...the elbows and smoke pipes are fabricated out of 4" schedule 10 black iron pipe, scrounged from the trash hoppers.
A little handle and latch had to be made to open and lock the combustion door. Again, the majority of the air provided by this door is for the front of the firebox....
Note the 2" copper pipe at the bottom in the front ?? Well a blower assembly off of a computer mainframe slides into the end of the pipe and provides combustion air for the other 2/3rds of the firebox... We burned holes through the firebox and chipped out the firebrick and have individual ball valves on each to control the amount of air to their respective locations. Monitoring the temps on the ends of the firebox, a combination of adjusting the smoke pipe dampers and the ball valves for combustion air allows very even control across the hog. I found 325 degrees was the prime temperature, didn't matter the size of the pig or hog.
Salvaged 2"x6" firebrick from the same boiler lines the inside of the firepit and have kept the firebox from burning out for 16 years.
Guess maybe an inside view of the heat chamber would be good...Either the spit which is a 1 1/2" stainless steel shaft or the octagonal expanded metal cage rests in the two angle iron "bearings". They are lined with high density poly board so its not metal to metal contact.
We used some unistrut to mount the bearings,sprockets and gearhead. I don't remember the ratio but with a 1725rpm motor the hog rotates at 1.7 rpm's. Seems to be adequately slow in rotation. We stick a meat thermometer in one shoulder and in the opposite ham to monitor the core temp. Cook to anything above 165 degrees and it is done and ready to pull off the heat. The lard renders out of the fat and drips down into a tray under the hog filled with lava rocks to minimize flare ups...and a drain off the end of the tray drips the excess grease out the rear of the roaster.
I've got more fabrication pictures, but they are regular pictures and not digital...Shots of the boys doing their thing, sometimes scrunched up and welding inside the roaster and sometimes laying on the ground, sometimes grinding but all the time smiling !!! All in all quite a good project for a pair of 10yr old and 17 yr old boys !!!!
The biggest hog that was roasted so far was 238 pounds on the hoof. It cooked in approximately 7 1/2 hours at 350 degrees. Man...I'm feeling a good old roasting coming up maybe in the fall....