Big-Bang Model 8FR Noise Reduction
There are actually four versions of the Big-Bang 8F. Not shown here is the all iron model we know and love and the die cast version which is less common. Even harder to find are the two noise reduction models. The exact reason for the noise reduction models is not known, but it can be deduced that some municipality required noise makers to have some form of adjustment.
The version I believe to be earlier has a butterfly valve at the muzzle that is open or closed to attenuate the noise. A wing-nut is used to lock the valve in position. At first inspection one would think this is some homemade modification, but I have seen several and they are all the same.
The valve shaft is a slotted head screw. Under the screw head is a coil spring that is about two coils long. Between the spring and the barrel is a flat washer. Inside the barrel is the stamped butterfly, formed to press fit on the screw. On the opposite side of the barrel from the screw head is a brass wing nut. This cannon uses the 8F iron barrel. When the butterfly is closed all the way the cannon report cannot be heard.
The noise reduction device is a threaded brass plug with a flange large enough to cover the muzzle. The edges of the fins are threaded and the plug screws in and out decreasing or increasing a annular opening, thus attenuating the noise. To avoid loosing the plug, it is chained to the axle with a light metal chain. At least two styles of chain were used.
As if for a salt shaker, there are six small holes in the flange that allow the escape of gas when the plug is screwed all the way in. At this setting the cannon report cannot be heard.
The die cast 8F's also use the shorter 7F drags. Die-cast 12F's are know to exist, however there is no evidence of a 12FR.