AUGUSTA -- The classic cars and souped-up racers on display at the Northeast Motorsports Expo were impressive. click image to enlarge Kevin A. Purnell II demonstrates a radio controlled helicopter at the Granite Leisure Time booth during the Northeast Motorsports Expo on Sunday afternoon in the Augusta Civic Center. Staff photo by Joe Phelan Select images available for purchase in theMaine Today Photo Store But it was Kevin Purnell's miniature vehicles at the Augusta Civic Center Sunday that generated excitement for radio-control hobbyists. Radio-controlled vehicles take the shape of cars, rock-crawling trucks, boats, planes, helicopters, tanks and motorcycles, and range…