two side walls 17 and 18 respectively configured with pyrimidal shaped quarter panels at the apex of walls 17 and 18 are respective internal bearings 19 and 20 for rotatively supporting drum shaft 21 which is fixedly attached to respective distal ends 22 and 23 of drum 11 fig2 a motor 24 rotatively drives the drum shaft 21 thus causing drum 11 to rotate arrow 25 within end bearings 19 and 20 the end walls 17 and 18 are each pyrimidal shaped so that the respective magnetron waveguides 13 14 15 and 16 project the microwaves inwardly toward the center of drum 11 waveguides 13 and 14 are vertically oriented while waveguides 15 and 16 are horizontally oriented such that the microwaves projected from chamber walls 17 and 18 are cross polarized with respect to each other the airflow system of this invention is illustrated in fig2 there are two air ducts 26 only one of which is shown in the sectional view of fig2 each duct 26 has two squirrel cage blowers 27 and 28 respectively disposed therein as shown each of the blowers 27 and 28 feeds air arrows 29 through duct 26 towards and into a common chamber inlet 30 each blower 27 and 28 cools a magnetron 31 disposed adjacent its respective waveguide there are a total of four magnetrons 31 each magnetron 31 produces approximately 700 watts of 2 450 mhz there are two magnetrons 31 in each air duct 26 during the drying portion of the microwave heating cycle air enters inlet 30 of chamber 9 from the two air ducts 26 and is directed with aid of a microwave permeable deflector 42 across the heating chamber 9 arrows 32 towards chamber outlet 33 the airflow 32 passes through tumbler drum 11.