| Chicago Transit Authority 3 at Skokie, Illinois on April 20, 1965, Kodachrome by Chuck Zeiler. Car 3 was built by the Saint Louis Car Company in 1950 using components salvaged from PCC cars. This was the northern terminal of the Skokie Swift and car 3 is seen changing ends, thus both pans are up. Four cars were chosen for the initial operation of the line (1-4) and car 4 received the pans first, custom built at the CTA's Skokie Shops. Tests revealed that the pans would not maintain contact with the overhead wire at speed, so airfoils, designed by George Krambles, were built at the shops, installed on car 2, tested and adjusted, factoring in prior tests done on the Illinois Terminal. The actual design was basically two standard trolley poles with their spring bases mounted parallel and joined by a light frame supporting a pantograph bow. A roof-mounted motor-driven retriever handles the trolley rope and a solenoid latch holds the pan down when desired. The tendency of wind pressure to push the pan down at speeds in excess of 35 mph is offset by the lift produced by the airfoil installed between the poles below the bow. While a pantograph concievably could have done the job, at the time the existing pantographs available either in the USA or abroad did not meet the extreme conditions of 22 foot high wire, low car roof, and weight limit permissible on the light roofs of the cars. Stools under small, light pantographs would not have met clearance limitations at shop doors and overpasses. |