Abstract: The invention comprises a mechanism for aiding in the closing of a bi-fold door, and for maintaining the door in a closed position, which includes a door frame having vertically spaced apart frame members, an upper horizontal frame member extending between said vertical frame members, the frame members defining an opening in a wall, a pair of bi-fold doors hinged together at adjacent edges adapted to at least partially close the opening, one of the doors of each pair being in a fixed position to pivot about points at the top and bottom thereof adjacent one of the vertical frame members, a guide and supporting track extending longitudinally along the length of the upper frame member, a roller member extending upwardly from the other of the inner doors into the track and being guided thereby in the track whereby the other of the doors at the free end thereof has sliding longitudinal movement in the track and the pair of doors may move from an open position in which they are in a generally V-shape into a closed

Abstract: A vehicle chassis dynamometer for measuring available vehicle road horsepower is disclosed together with means for compensating an apparent dynamometer horsepower reading for dynamometer vehicle rolling resistance, and vehicle drive line losses, and adjusting for ambient barometric pressure, temperature, and fuel specific gravity to obtain an accurate reading of engine flywheel horsepower that may be used directly for comparison with engine manufactures SAE rated horsepower.