Slack adjusters have been installed in all freight cars to maintain appropriate spacing between the brake shoe and the wheel tire when the brake is loosened.
4.5 Brake Shoes
Most freight cars employ a variety of brake shoes, however, synthetic brake shoes (e.g., of resin), which, comparatively speaking, maintain a constant value for friction coefficient in the face of speed, have been used. Some low-speed freight cars employ cast iron brake shoes.
Fig. 4.1 and 4.2 show typical brake systems of freight cars.
5 Pendulum Car
5.1 Pendulum Car Principle
When traveling along curves at high speeds, cars are subject to centrifugal acceleration (Fig. 5.1) in relation to curve radius and runing speed. Passengers experience a force that works to fling them beyond the curve, making the ride uncomfortable. Measures have been taken to reduce the centrifugal acceleration felt by passengers (αu in the diagram) by raising the outer rail along curves to increase the cant (C0 in the diagram) and incline the car body to the inside. However, as there is a risk that cars will topple inward when they stop at curves if the cant is increased by too great a margin, restrictions apply, resulting in excess centrifugal acceleration (αu) that cannot be offset by cant when the running speed along curves increases.
The relationship between these amounts is expressed as follows:
Where V: running speed g: acceleration of gravity
R: curve radius C0: cant
G: gauge
In reality, the acceleration experienced by passengers in cars is 20 - 30% greater than αu described above because the car body tilts outside curves due to flexing of the car springs. The speed must be restricted to reduce the lateral constant acceleration felt by passengers below a specific value (the recommendation in Japan is 0.08 g) and ensure that riding comfort is not impaired.
