side view of a preferred embodiment shows an alternative method of securing and restraining the expansion 18 of transfer arm 6 in this embodiment the elevation 2 shown in fig3 is replaced with a removable multi layered shell 40 as shown in fig6 this embodiment eliminates the pronounced deviation in the smooth curvature of the outer surface of the helmet created by elevation 2 of the previous embodiments the shell is composed of two walls 41 42 an inner wall 41 fits closely over the outer surface of the helmet 43 covering the crown of the helmet and extending down the sides of the helmet the edge 44 of the inner wall 41 is relatively flush to the helmet providing a minimal deviation from the smooth curvature of the helmet along the edge of the shell the shell is comprised of a single wall extending up the sides of the shell away from the edge and toward the crown the single wall diverges into two walls the inner wall 41 described above and an outer wall 42 approaching the crown of the helmet the outer wall develops a radius of curvature greater than the inner wall thereby creating a cavity 45 between.