Abstract: In a sheet stacking system employing a spirally slotted wheel and a stripping plate to remote sheets from the wheel and form them into a stack, the sheets are conveyed to the stacking wheel by a vacuum drum having a slot around its circumference into which extends the extremity of the stacking wheel. The sheet continues to be held on the drum surface by the vacuum until it encounters the stacking wheel extremity which, by virtue of the lower peripheral speed of the stacking wheel, acts against the vacuum to strip the sheet from the drum. The stacking wheel axis may be mounted for pivotal movement about the vacuum drum axis to accommodate different output stack sizes, permitting the formation of a sheet store buffer.