A control program for a positive displacement metering system measures the time required for the travel of a free piston in a cylinder of known volume to determine an average flow rate during a full stroke of the piston. The apparatus includes an inflatable and collapsible enclosed structure constructed and arranged to transition between an inflated configuration and a collapsed configuration when pressurized fluid is received therein and released therefrom, respectively. If a failure occurs to a storage drive 171 constituting a RAID group whose redundancy is lost, the storage system 10 sets the broadcast inhibiting flag to inhibiting the broadcast transmission, and if a failure related to the storage drive 171 occurs and the broadcast inhibiting flag of the storage drive 171 is being set to inhibiting the transmission, inhibits the transmission of the broadcast. Wear of the edge of the vanes is decreased by the judicious location of the discharge holes. The add-on is reusable and may be separated and re-attached to various magazines. Also claimed is a method of reversing the drop hammer with respect to the drop hammer housing.