Mack Rail – The Rail Cars

kscarbel2 · November 12, 2013

From as far back as the early 1920s, many railroads were interested in the concept of light rail, then described as self-propelled passenger rail motor cars for local and branch lines whose passenger demand couldn’t support a locomotive-hauled passenger train but exceeded the ability of a rail bus.

Mack Trucks, one of the American pioneers of light rail development, was actively designing and producing “light rail” cars with versatile passenger and freight configurations that delivered maximum productivity at moderate costs. By providing a means for comprehensive and affordable urban public transport, Mack Trucks helped to advance both America’s economic development and quality of life.

Mack Trucks and the J.G. Brill Company of Philadelphia formed a joint venture in 1923 and produced the first Mack rail car, the model AH. Fifty feet in length and mounted on a pair of double trucks*, Mack’s rail car was used for demonstration purposes to prospective clients carrying the number 801.

The trucks were assembled by Mack Trucks in Allentown, with a six cylinder gasoline engine situated within the forward truck driving a prototype electro-pneumatic propulsion system. Mack then shipped the trucks to Brill for mounting of the body.

The Mack AH rail car featured right-hand operator’s cabins front and rear, vestibules at each end, salon, coach and smoking sections, lift sash windows, conductor’s signaling system, storage room for baggage and/or mail, both street and platform level doorways, and modern lighting, heating and ventilation.

Standard couplers and end pass-through doors permitted multiple unit operation.

*The term “truck” refers to the pivoting structure (bogie) under each end of the car including the axles, suspension, brakes and propulsion motors.

kscarbel2 · November 12, 2013

At a cost of one million dollars, Mack engineers next developed the dual-engined model ACP rail car utilizing two 60 horsepower Mack AC four cylinder engines. The ACP could be ordered either as a passenger car or as a combination passenger and freight car, with the bodies produced by Pullman Car and Manufacturing Company of Chicago. Allentown’s Plant 4 completed three ACP rail cars in 1925, two as demonstrator cars and the third unit for the Chicago, Rock Island & Pacific Railroad.

After extensive tests by engineers from both Mack Trucks and the Philadelphia & Reading Railway, the two demonstrator ACPs were put into regular service with the Lehigh Valley Railroad operating between Mauch Chunk, Pennsylvania and Newark, New Jersey, and between Easton, Pennsylvania and Jersey City, New Jersey.

But just as Mack Trucks had arrived at a viable self-propelled passenger rail car, a growing preference for gas-electric propulsion systems* over electro-pneumatic propulsion brought an end to ACP production.

*One or more gasoline engine/generator combinations remotely mounted from the trucks in the rail car producing electricity for traction (propulsion) motors mounted on one or both trucks. The term “truck” refers to the pivoting structure (bogie) under each end of the car including the axles, suspension, brakes and propulsion motors.

kscarbel2 · November 12, 2013

From 1926, Mack rail car production shifted from Allentown to the company’s Plainfield, New Jersey plant.

In 1927, Mack’s Plainfield unit unveiled the new lightweight single-engined model AS, midweight dual-engined model AQ, and the heavyweight triple-engined model AR combination rail cars featuring gas-electric propulsion systems (A quadruple-engined rail car was available on special order). The AR had a reinforced underframe, drawbars and couplers to withstand the added stresses of multiple car and trailer operations.

Enhancements to the new range of rail cars included shatter-proof windshields with electric windshield wipers, and an isolated engine room with both side and roof-mounted radiators. A frontal roof air scoop was integrated into the rail car’s design that circulated air through the engine room which then exited via a roof vent.

Specifications varied as all Mack rail cars were built to meet customer-specific requirements.

Each six cylinder 135 horsepower Mack AP engine was connected via a Mack-designed torque insulator to a 450 volt 90kW generator and a separate 32 volt generator for interior lighting.

Typically, the AS and AQ had two 140 horsepower traction motors located in the forward truck, while the triple-engined AR had an additional traction motor in the rear truck as well. Maximum speeds for the AS, AQ and AR were 45, 54 and 61.6 miles per hour respectively.

The sales marketing group of Mack Trucks’ rail car department promoted the fuel economy advantages of the company’s multiple engine propulsion system which allowed one or more engines to be shut down under light load conditions.

Mack’s model AQ demonstrator no. M200, later sold to the New York Central System, averaged an operational cost of twelve and a half cents per mile (gasoline, oil and maintenance) during a long-term six month test.

Mack’s triple engined model AR demonstrator no. M2001, later sold to Pittsburgh & Lake Erie Railroad, successfully demonstrated a multiple rail car towing ability throughout the mid-western United States.

*The term “truck” refers to the pivoting structure (bogie) under each end of the car including the axles, suspension, brakes and propulsion motors.