Why do streetcars make a “squealing” sound when they go around curves?
The wheel sets underneath a streetcar are called trucks. On shorter cars there is usually one truck that is fixed to the car body and incapable of swiveling. On longer cars, there are usually two trucks that are capable on swiveling on curves. In both cases the actual wheels are fixed to axles which rub against the inside of the rail causing the squealing. To eliminate the noise a rail grinder can be used to smooth rails or grease or graphite can be placed on the inside of the rails reduce the noise.
