A bolster or turntable is a device (or rather a set of devices) that allows long loads to be transported on two transporters, with a relatively short length, instead of one single transporter with a length (almost) equal to the load. Such a transport is also referred to as a “dolly transport”. The turntables or bolsters allow transporters to pivot underneath the load to negotiate turns and corners and (to a certain extent) super elevation and articulation, as well as inclines and declines.
A turntable consists of two parts: a lower part that is secured to the transporter called the Lower Fixed Part (LFP) and a movable or rotating upper part that is secured to the load, called the Upper Rotating Part (URP). The URP rotates around the center of the whole assembly. The two parts are held in place by a pin or a ball bearing. The contact area between the URP and the LFP is lubricated with grease or oil to allow the rotating motion with minimal friction.