Generally, shopping carts in shopping malls have 4 casters, and there are luggage carts in airports. It can be seen that the axle of the caster is not fixed, but can rotate freely around the vertical axis. Because the axle and body are fixed, the casters can only go all the way forward, so the shopping cart cannot turn.
Also, the casters always follow the rear of the swivel axis when you push the cart forward. If changing from front to back, the caster user will suddenly turn 180 degrees near the vertical axis and still follow the axis of rotation. Under normal circumstances, the rolling direction of the casters must be consistent with the forward direction, so that the cart can go with the local movement. Once the rolling direction of the wheel is not consistent with the forward direction of the vehicle body, the friction force on the ground will generate torque on the vertical rotation axis in front, pushing the wheel to a position consistent with the walking direction.
Similar to shopping cart casters in shopping malls, bicycles have a similar phenomenon. If the pivot axis of the front fork of the shopping cart extends to the ground, the intersection point between the fork and the ground is always in front of the contact point of the front wheel and the ground. When you push the pad forward, the front wheels follow the direction smoothly. If the stroller is rolled backwards, the opposite position of the front wheel and front fork is exactly the opposite. The sideways friction forces are in the opposite direction, and the front wheels oscillate. The relative position between the front fork pivot and the contact point of the front wheel with the ground is very important to ensure the stability of the shopping cart.
For any inquiry or assistance please contact us by sales@shangxincaster.com or whatsapp + 86 152 5836 8162
