I wrote this up for a question on another site but thought that you might be interested in the info as well.
Here is some Energy Absorbing Steering Column Design 101
Starting in 1967 there have been several generations of energy absorbing steering columns. They all have been designed to collapse from both directions and limit the amount of force and absorb energy from the driver direction. The steering columns were primarily designed to reduce the forces on the chest of an unbelted driver and also to prevent the steering shaft from being displaced rearward so as to act as a spear and impale the driver. The basic concept is still used today even with inflatable restraints (air bags) being incorporated into the steering wheel on all cars and trucks.
Original GM design (1967-1968) with expanded mesh steering column jacket.
2nd generation steering column jacket (1969 onward) with ball bearings between the upper and lower tubes. The ball bearings "plowed" grooves in both tubes as they telescope onto each other.
Plastic injection joints in the shift tube (upper drawing) and the steering shafts (lower drawing) that hold the upper and lower parts to a correct length and prevent "rattle" at the junction of the two parts. Plastic is sheared with minimum force and upper shaft(s) telescope quite easily over the lower shaft(s).
Jim
Here is some Energy Absorbing Steering Column Design 101
Starting in 1967 there have been several generations of energy absorbing steering columns. They all have been designed to collapse from both directions and limit the amount of force and absorb energy from the driver direction. The steering columns were primarily designed to reduce the forces on the chest of an unbelted driver and also to prevent the steering shaft from being displaced rearward so as to act as a spear and impale the driver. The basic concept is still used today even with inflatable restraints (air bags) being incorporated into the steering wheel on all cars and trucks.
Original GM design (1967-1968) with expanded mesh steering column jacket.
2nd generation steering column jacket (1969 onward) with ball bearings between the upper and lower tubes. The ball bearings "plowed" grooves in both tubes as they telescope onto each other.
Plastic injection joints in the shift tube (upper drawing) and the steering shafts (lower drawing) that hold the upper and lower parts to a correct length and prevent "rattle" at the junction of the two parts. Plastic is sheared with minimum force and upper shaft(s) telescope quite easily over the lower shaft(s).
Jim