This is my system for mixing my own potting soil. It was made from a recycled dryer drum. I use a microwave to pasteurize the compost when making soil to propagate from seed. The microwave is from a yard sale at $5.00. A plastic shoe box with lid fits in the microwave and usually takes about 10 min to get to 165 deg f depending on moisture content of the compost.
The door consists of ¾” plywood, two hinges and six pull clasps. There is a 2” hole in the center of the door to permit inserting a wand of a tank sprayer to spray water just before completion of tumbling to eliminate dust from the vermiculite. The top of the door folds down to permit loading of material.
The top of the door folds down to permit loading of material and inspection of results after blending. I can load about 2 cubic ft or 15 gallon of material at a time. If the material is lumpy, I also add about one dozen #2 gravel (recovered after blending) to aid in breaking up the lumps.
I don’t think the standard drive unit or motor on a dryer would handle the added weight so I used a 3/4 HP motor and a worm gear speed reducer. I also used a heavier belt from the speed reducer to the drum.
When a batch is finished, I attach a plywood funnel to the front panel to reduce spillage. I also use a 40 gal trash can to store the soil in. I usually fill it about 2 times a yr.