Detachable fibreglass road shells having an accurate moulding of a true road surface. These shells are usually thicker than the aluminium type, below, and in both cases the floor plates must be adjustable in order to accommodate them.
Detachable cast aluminium alloy road shells, made in segments that may be bolted to the outside diameter of the rolls. The surface usually consists of parallel sided pits that give an approximation to a road surface.
A permanently fixed road surface made up of actual stones bonded into a rubber belt which is bonded to the roll surface.
Most road shells are not capable of running at maximum rig speed because they are difficult to fix and to balance, also they may not be capable of transmitting full acceleration torque. It is therefore necessary to provide safety interlocks so that the