Abstract: A method of making a coil spring wherein the external surfaces of the convolutions have cylindrical major portions and flats which abut the neighboring convolutions when a spring is compressed flat under load. This reduces the likelihood of radial displacement of one or more convolutions under load and the likelihood of a reduction of the axial length of the coil spring when in its unstressed condition subsequent to being repeatedly compressed flat under load. The external surface of each convolution can be provided with one or two flats, and the planes of the two flats preferably make a small acute angle if the coil spring is caused to assume an arcuate shape when in actual use.

Abstract: A torque transmitting apparatus which can be installed between the prime mover and the transmission of a motor vehicle has a primary flywheel connectable to the output element of the prime mover. A secondary flywheel is coaxial with and rotatable relative to the primary flywheel. A friction clutch with a clutch disc drives the input element of the transmission when the clutch is engaged. A damper is provided between the two flywheels. The damper and the friction clutch constitute a power train which is provided with a coupling device serving to afford access to the clutch disc without damage to the elements of the power train, and with one or more slip clutches which limit the magnitude of the torque transmittable from the primary flywheel to the clutch disc in the engaged condition of the friction clutch. The slip clutch or slip clutches can form part of the coupling device or vice versa.

Abstract: A coil spring wherein the external surfaces of the convolutions have cylindrical major portions and flats which abut the neighboring convolutions when a spring is compressed flat under load. This reduces the likelihood of radial displacement of one or more convolutions under load and the likelihood of a reduction of the axial length of the coil spring when in its unstressed condition subsequent to being repeatedly compressed flat under load. The external surface of each convolution can be provided with one or two flats, and the planes of the two flats preferably make a small acute angle if the coil spring is caused to assume an arcuate shape when in actual use.