The illustration shows the various radii employed in setting out a brake block for a standard railway wagon. The diameter of the wheel is 3 ft. 1 in., and the radius for the sole of the brake block is half the diameter of the wheelthat is, 1ft. 6 1/2in., as it is the rule to set out the blocks to the same radius as the wheels on the tread.

Setting Out Railway Wagon Brake Blocks.