Turn the drum so that it is upright. Measure 9 inches from the top of the front of the drum and make a mark with a sharpie.
Measure 22 inches downward from that point and make another mark with the sharpie.
Drill two pilot holes where you made the mark 9 inches from the top so that the saw blade can be inserted and used to cut the circle.
Tape or tie an 18-inch long piece of twine to the end of the sharpie and place the tip of the sharpie in between the mark at the top of the barrel and the one at the bottom. Hold the twine in place and trace around the front of the drum with the marker, outlining a circle.
This will create the 18-inch circle that you need to cut out from the barrel.
Cut out the circle with the reciprocating saw and discard the cut circle.
Drill a 1/8-inch hole in the sidewall of the tractor trailer tire. Insert a 1/8 inch eye hook and screw a bolt on the other side of the sidewall to secure it in place.
Lay one of the 2-inch-by-4-inch boards over the center of the tire and secure in place with two 3-inch screws. Secure the remaining boards in the same way, one on the left, the other on the right.
Flip the tire over so that the boards rest on the ground.
Measure the height of the top rim in the center of the tire. Take that height and divide it by two to get half.
Take that total and measure up that many inches up from the bottom of the drum. Drill four 1/8 inch holes around the circumference of the drum at that height.
Insert two of the carriage bolts through the inside of the drum and tighten the bolts and washers to the ends of the carriage bolts inside the drum.
Place the drum into the tire so that the carriage bolts fit under the lip of the top rim of the tire. Insert the two remaining carriage bolts into the remaining two holes so that each bolt holds the drum in place inside the tire.
Drill two 1/8-inch holes 6 inches apart through the groove in the top of the lid. This will help prevent rain from building up inside that groove, keeping mosquitoes from nesting.
Fill the mineral feeder with mineral pellets and drag it to the field you need it in.