Carver grinned as Finkelstein did [i]exactly[/i] what he was hoping for. Just as the Doctor was passing by, he swung the arm down and jammed it between the spokes of the wheel closest to himself. 

The motion of the wheel yanked the arm down, backward, upward--and smashed it into the electric motor attached to the back of the chair's underside. The force of the motor wasn't enough to do significant damage from the collision, but the arm blocked the wheel from continuing to turn, and thus prevented the chair from moving forward. 

Before Finkelstein could react, Carver shoved the arm the rest of the way across the bottom of the chair, threading it through the spokes of both wheels. Then he stepped back to examine his work where he was out of range of retaliation.