Analysis of variance in complex experimental designs

An apparatus for forming heat exchanger turbulators from a roll of sheet metal strip stock employs two forming wheels with generally triangularly shaped teeth meshing with one another and one roll being driven about a fixed axis and the other roll being journalled on a second axis parallel to the first and disposed in floating relation thereto with means for adjustably biasing the second roll toward the first. A special tooth on each roll is used to form the turbulator handle and cut-off blades may be included to automatically cut the formed strip into individual turbulators.