The ornamental design for a winch drum, as shown and described.
FIG. 1 is a perspective view of the first embodiment for a winch drum of the present invention;
FIG. 2 is one end view thereof;
FIG. 3 is the other end view thereof;
FIG. 4 is a side view thereof with all the sides being the same;
FIG. 5 is a perspective view of another embodiment of the present invention;
FIG. 6 is one end view thereof;
FIG. 7 is the other end view thereof;
FIG. 8 is a side view thereof with all the sides being the same;
FIG. 9 is a perspective view of another embodiment of the present invention;
FIG. 10 is one end view thereof;
FIG. 11 is the other end view thereof; and,
FIG. 12 is a side view thereof with all the sides being the same.
The broken line showing of a handle and some elements in some of the figures is included for the purpose of illustrating environment and forms no part of the claimed design.