A common type of mechanical spring in a form of ahelix, manufactured in different styles and sizes for many different applications.
1962 June, “The design of the S.R. electro-diesels”, inModern Railways, page395:
The nests ofcoil springs at each end of the bolster, resting on the spring plank, are in line with the swing links between the swing plank and the one-piece fabricated bogie frame; [...].
