members 19 arranged perpendicularly to the base of the rack so as to support and hold the canisters 10 in place also the rack base is raised from the floor by two support rails 20 and five horizontal beams 21 attached to provide the necessary clearance for engaging an elevator assembly 30 see fig5 four roller assemblies 22 assure minimal friction in the event of contact with the side walls of storage bays 54 see fig1 tapered wedges 23 on the lower surface of the support rails 20 compensate for the incline built into the floor of the storage bays 54 six load bearing pads 24 on the lower surfaces of the horizontal beams 21 provide a uniform stroke for all six hydraulic cylinders 38 see fig6 a in the elevator assembly 30 see fig5 the storage rack 17 may for example be 6 feet 7 inches by 8 feet with an overall height of 10 feet when loaded with canisters 10 referring to fig5 a and 6b a drive unit 25 is supported on rails 26 located in a control tunnel 27 the control tunnel 27 is physically separated from a storage bay access tunnel 28 by a shield wall 29 suspended from the roof of the storage facility the drive unit 25 is coupled to a storage rack elevator assembly generally indicated at 30 by a set of parallel wire ropes 31 see fig6 a and also by air hoses 32 and electrical cables 33 the drive unit 25 and attached elevator assembly 30 move along the parallel control and access tunnels 27 28 and the parallel wire ropes 31 may be extended to allow the elevator assembly 30 to.