Abstract: A suspension system comprises a first hub, bearing means spaced from the hub, a second hub carried within the bearing means and rotatable relative to it, and torsion bar means carried by the first and second hubs and extending between them. At least the second hub is positioned within a stationary, hollow tube of non-circular cross section, with the second hub defining rotary motion limiter means that moves into contact with the hollow tube at a desired limit of rotary motion of the second hub, to prevent further rotary motion beyond the limit. The second hub also carries a transversely extending arm. The second hub, including the limiter means and the arm, is made of a single, cast piece for improved manufacturing efficiency.

Abstract: A torsion bar suspension unit includes a pair of hubs, one of which is attached to a rotationally oscillatable member, and torsion bar means secured and extending between the two hubs. Various improvements to the structure are provided.

Abstract: An air filter of the type having a porous filter medium body layer supported in a complementary unitary frame has a perforated panel supportingly engaging one face of the layer with folded up narrow panels along the edges of the layer, narrow retainer panels overlying the margins of the opposite face of the layer from the perforated panel, and each of the retainer panels being provided with spaced extensions which overlap adjacent the corners of the layer and are secured together as by means of adhesive, there also being anchoring adhesive securing two of the retainer panels to the filter layer. The overlapping extensions are perforated.An efficient method of making the air filter is provided.