Abstract: A shingle stacking machine including a shingle stacking station, a shingle bundling station, and a conveyor for removing bundled shingles from the machine. The shingle stacking station includes a pair of parallel and elongated wheel assemblies rotatably mounted to a frame of the machine. A drive mechanism is provided for rotatably indexing each wheel assembly during a drive mode of operation and permits free wheeling of the wheel assemblies during a jam mode of operation. The drive mechanism includes a motor for continuously driving a vacuum operated clutch assembly. The clutch assembly includes a pair of electromagnetic valves for controlling operation of a drive shaft which is connected to the wheel assemblies through an elastomeric belt drive. The shingle bundling station is disposed beneath the shingle stacking station and includes a pair of shelf-like supports pivotally carried on the machine frame.