T/CCI’s QP7H15 Wobble Plate compressors are classified as either HD (Heavy Duty) or SHD (Super Heavy Duty). On occasion we get asked the question what is the difference between HD and SHD and what type of extra life can be expected of the SHD version. Since T/CCI’s customer base is primarily in the Heavy Duty markets like truck, bus, emergency vehicles, and military, a lot of design and development effort has been put into both the HD and SHD designs. The difference is in the clutch. Every time a clutch engages (or cycles) there is a small amount of metal wear as the stationary armature plate “engages” with the spinning pulley. T/CCI’s HD clutches are of a Spring Leaf (sometimes referred to as Leaf Spring) design and are rated at 1,000,000 cycles for extra-long life. However, T/CCI’s rubber ring armature SHD clutch takes the life to a whole new level. An industry best astounding 2,000,000 cycles!!