Permissible mine car adapter assembly

A fire-safe torque transmission apparatus comprising a walled explosion proof container, a sleeve member defining a throughgoing bore secured to a wall of said explosion proof container, the bore allowing communication of the interior of said container with the atmosphere, an adapter plate assembly removeably mounted to said sleeve member, said adapter plate assembly comprising a support member and a shaft support member connected to said support member, said shaft support member defining a throughgoing bore with first, second and third annular steps at each end, the third step forming a common step for both ends and defining a cylindrical bore adapted to receive a rotatable shaft, the first step serving as a bearing race seat and the second step serving as a flame baffle, ball-bearing race means mounted on each end of said shaft support member in said bearing race seats, a rotatable shaft of smaller diameter than the diameter of the cylindrical bore formed by the common third step mounted on said ball-bearing race means and rotatably positioned within said cylindrical bore, one end of said shaft being connected to a motor mounted inside said explosion proof container and being adapted to be rotated by said motor with the spacing between the inner wall of the shaft support member defining the cylindrical bore and the outer surface of the rotatable shaft not exceeding 0.014 inches and extending a length of not less than about 11/2 inches to prevent a flame from passing therethrough.