A leaf spring's strength is determined by its length width, thickness, and severity of the
Leaf Spring
The leaf spring was the first spring to be used with axles and wheels. They were fabricated by blacksmiths during the 1800s who would heat and bend a thin strip of mild steel into a semi-ellipse, or an arch. The length, width, thickness, and severity of the arch are all physical factors, which affect the spring's rate or strength. The width of the spring will affect the rate, and the leaf spring thickness and length have a greater affect on the stiffness of the pack. The arch of the leaf spring creates added strength and recoil action. The spring leaf is drawn and rolled or tapered, which provides flexibility and a smoother ride. Eyes are formed at each end of the main (bottom) leaf spring, then a hole is punched for the stacking (locating) pin.
The rear main leaf spring eye is attached to the vehicle's frame by a shackle that pivots
The leaf spring is now ready for formation and heat treatment. This process heats the leaf spring in a thermostat-controlled furnace and then forms to the proper free arch, ensuring a permanent arch to the spring. Then it is quenched in a hot oil bath and the leaf is Brinelled (hardness tested). To multiply the spring rate or strength, leaf springs are stacked, which creates a spring pack. A thick spring pack with many thin leaves will conduct a softer rate than one with fewer leaves of greater thickness. The leaf spring packs are clamped together. The mono spring or spring packs are hung from the framerail by shackles (hangers), which allow the springs to flatten out during weight increase or load; the shackles would move or pivot, allowing them to absorb the weight increase. The closer the shackle is to a vertical angle, the higher the effective spring rate. When the shackle is laid back at an angle, it actually becomes a moving link with the spring, and the spring ride will feel softer.
The front main leaf spring eye is held stationary, only moving in the bushing.
During static load, spring leaf packs have friction between the leaves, causing the springs to ride rough over small bumps because the spring must overcome the pack friction before it starts to flex. For example, rolling slowly over a speed bump, at the bottom of the speed bump, the suspension is rigid with really no feel of suspension absorbing any of the impact. A leaf spring or springs are connected to the axle using U-bolts and plates sandwiching the axle between the two.
A torsion bar is a straight spring that is splined or brouched on the ends. Used in differ
Torsion Bar
Another strength-contributing component to a truck suspension system is a torsion bar. These pieces of round bar are cut to specific lengths. The diameter and length will determine its strength. Torsion bars are brouched or splined at both ends; one end is fixed in a pocket in the chassis, usually a crossmember. The other end is fixed to a brouched pocket in the lower control arm. As the lower control travels in a vertical motion, it begins to twist the bar, the fixed ends of the torsion bar are giving each end resistance against one another. The resistance is increased the higher the lower control arm is twisted. Similar to anything else that is under continuous tension and motion, such as a torsion bar, it will weaken over a period of time and have to be readjusted or replaced.
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