by fig1 a and 12b the dampers 100 between the access opening 23 and the belt groove 21 are diametrically opposed the dampers 100 between the belt groove 21 and the rear end 600 of the drum 16 are also diametrically opposed and are offset by 180 degrees from the dampers 100 between the access opening 23 and the belt groove 21 the dampers 100 between the belt groove 21 and the rear end 600 of the drum 16 can have a different size than the dampers 100 between the access opening 23 and the belt groove 21 for example the dampers 100 between the belt groove 21 and the rear end 600 of the drum 16 can be smaller larger and or have a different shape than the dampers 100 between the access opening 23 and the belt groove 21 the embodiments illustrated by fig3 a 12b can be combined in a variety of different ways for example dampers 100 may be placed both inside and outside the drum 16 and or behind and offset from the from the baffles 24 any of the configurations illustrated by fig3 a 12b can be combined with any of the other configurations to form additional damper configurations fig1 a 13c illustrate and exemplary embodiment where the drum 16 is contoured the drum 16 may be contoured in a in a wide variety of different ways.