Specifications

In the traditional design of a trap the clay is loaded on to the end of the throwing arm.  This means that any vibration in the arm during throwing can influence the trajectory of the clay.  In the design used by Parker Clay Pigeon Traps, based in Wisbech, Cambridgeshire the clays are released from the loading mechanism on to a plate; then, the rotating arm whips the clay from the plate into its trajectory.  The support plate provides a rigid platform from which the clay can be launched with greater accuracy.

The trap incorporates a powerful coil spring which is offset-secured to a block mounted on the opposite end of the shaft that carries the arm.  When the arm is cocked and latched, the spring is under considerable tension, waiting to provide the several thousand pounds of force required to drive the arm.  It reaches about 2000 rpm as the clay leaves the trap.

The spring propels the arm through about half a revolution - the clay leaving the trap after about 90 to 120 degrees when the spring has lost most of its energy and the arm is slowing down.  The arm continues to rotate well beyond the unloaded position of the spring until its kinetic energy is dissipated by the spring and it comes to a stop when it is restrained by a backstop mechanism.  Then, the arm is positively driven forward to the cocking and latching position, putting the spring under tension again.  Parker uses an electric-driven cam to provide this drive.

Parker asked Cross & Morse to design a packaged unit that would incorporate the throwing arm drive shaft and backstop sprag clutch as one assembly.  The specification required that backlash and axial-free play be kept to a minimum to optimise accuracy of clay projection.  To achieve this, Cross & Morse custom-designed a carburised and hardened steel mounting block which also acts as the outer face of the sprag clutch.  The inner face has been machined on to the drive shaft, the latter being supported by two ball bearings which are press-fitted into the same block for optimum rigidity.  Special sprag elements were selected for their accuracy and reliability.

This design utilises few components, thus minimising the build-up of manufacturing tolerances and ensuring rigidity of the assembly.

The cam drive starts to rotate as the throwing arm is released and catches up with the latter as it slows to a stop.

At this point, the clutch engages to prevent the arm from reversing its direction and, in doing so, retains its kinetic energy.  The arm is prevented from oscillating, and faster re-cocking and latching for the next throw is achieved.