Abstract: A dynamically balanced exhaust pipe cap which includes an elongated tubular member having an upper end defined by an upper edge lying in a plane extending at an acute angle to the longitudinal axis of the tubular member. A closure flap assembly is pivotally secured to the upper end of the tubular member and includes a closure plate having a pair of balancing plates which extend downwardly from the closure plate on opposite sides of the tubular member. A pair of wind vanes are secured to the two balancing plates.

Abstract: A dynamically balanced protective cap for exhaust pipes, including a tubular element having an angulated bias cut defining a slanted opening at one end thereof. A closure flap assembly is pivotally secured to the tubular element for pivotation about a horizontal axis. The closure flap assembly includes a closure plate configured to lie across the close the slanted opening at one end of the pipe. The flap assembly also has a pair of parallel, trapezoidally shaped balancing plates, each secured along one edge to one edge of the closure plate. The parallel balancing plates are disposed on opposite sides of the tubular element, and each carries a bearing sleeve which receives a stub axel secured to the tubular element. A pair of horizontally spaced, monoplanar wind vanes are secured to aligned edges on the two balancing plates, and each wind vane extends normal to the respective balancing plate to which it is secured.