The ornamental design for a swingtrainingdevice, as shown and described.
FIG. 1 is a top perspective view of a swing training device;
FIG. 2 is a front view of the swing training device;
FIG. 3 is a back view of the swing training device;
FIG. 4 is a top view of the swing training device;
FIG. 5 is a left side view of the swing training device;
FIG. 6 is a right side view of the swing training device;
FIG. 7 is a side view of an alternate arrangement of the swing training device wherein the central shaft is disconnected from the base, shown here in a top perspective view, and connected to a vehicle hitch receiver; and,
FIG. 8 is an enlarged view of the ball swivel joint of FIG. 6.
The broken lines showing a vehicle are for the purpose of illustrating environmental subject matter and form no part of the claimed design. All other broken lines in the drawings depict portions of the swing training device that form no part of the claimed design.