The ornamental design for a swingarmclamp, as shown and described.
FIG. 1 is a perspective view of a swing arm clamp showing my new design;
FIG. 2 is a top elevational view thereof;
FIG. 3 is a first side elevational view thereof;
FIG. 4 is a front side elevational view thereof;
FIG. 5 is a bottom elevational view thereof; and,
FIG. 6 is a second side elevational view thereof.
The dash-dash broken lines depict a clamp handle and parts of the swing arm clamp in FIGS. 1 through FIG. 5 that form no part of the claimed design. The dash-dot-dash broken lines depict the bounds of the claim in FIG. 5 and FIG. 6. All broken lines form no part of the claimed design.