On the left, it has been steered, and we clearly see that the castor angle has introduced negative camber.
On the right, the wheel is shown with no steering input pointing straight ahead. The beneficial effects of castor can be seen in the figure. One other effect of a large pivot to contact centre offset is when one of the wheels hits an obstacle like a bump or pothole in the road a large opposing twisting force would be created momentarily which would be relayed back to the driver's steering wheel in a twitching fashion. This small offset permits the pivot axis to remain within the contact patch, thereby enabling a rolling movement to still take place when the wheels are pivoted so that tyre scruff and creep (slippage) are minimized. A compromise is usually made by offsetting the pivot and contact wheel centres to roughly 10–25% of the tread width for a standard sized tyre. No offset (zero offset radius) ( Figure 10.5) prevents the tread rolling and instead causes it to scrub as the wheel is steered so that at low speed the steering also has a heavy response. A large pivot to wheel contact centre offset requires a big input torque to overcome the opposing ground reaction, therefore the steering will tend to be heavy. When turning the steering the offset scrub produces a torque T created by the product of the offset radius r and the opposing horizontal ground reaction force F (i.e.
#King pins for trucks Patch#
The offset between the pivot centre and contact patch centre is equal to the radius (known as the scrub radius) of a semicircular path followed by the rolling wheels when being turned about their pivots.
If the swivel ball or pin axis is vertical (perpendicular) to the ground, its contact centre on the ground would be offset to the centre of the tyre contact patch ( Figure 10.4). Swivel pin or kingpin inclination is the lateral inward tilt (inclination) from the top between the upper and lower swivel ball joints or the kingpin to the vertical ( Figure 10.3).
0 kommentar(er)
