In 1961, American Car and Foundry (ACF) introduced a new type of covered hopper.  Up until this time, covered hoppers, like most freight cars had a heavy center sill to support the car and transmit the pulling force.  This required hopper cars to have two outlets for each bay; one on either side of the center sill.  ACF’s new design eliminated the center sill, allowing a single outlet that dumped between the rails.  The new design also centered the loading hatches atop the car and was cylindrical in shape.  ACF named their new design “Center Flow”.   The design was refined a few years later, becoming the Center Flow familiar to modelers.  By the mid-70’s, other car builders began producing similar designs.

   Though ACF adopted the name “Center Flow” for their earlier design, they will be referred to as “cylindrical” hoppers in this site to avoid confusion.  Many of the private owner schemes listed here were leased from Shipper’s Car Line or other lessors.  Information on how many cars were leased or how long the lease lasted is difficult to obtain.  Generally, only the built date of the cars is the most that I have been able to determine.  I will include quantities in the columns where car series are listed individually by the lessor, but this is no guarantee that the cars are still under the same lease.

CF Minitrix early.jpg




   The first Center Flow prototype never went into production; numbered SHPX 60000, it toured briefly as a demonstrator before being sold to the New York Central.  Numbered 885980 by the Central, it remained in NYC paint until at least 1987.  Minitrix offered a model of this pioneering car in the early days of N-scale, which was also sold under the “Postage Stamp Trains” label by Aurora.  Sadly, it was offered in the four schemes listed below, but not for New York Central.

DOW CHEMICAL- Minitrix 3121 is painted in a tank car paint scheme.  However, Dow Chemical owned a series of cylindrical hoppers numbered 73501-73533.  The paint scheme was undoubtedly different, but I’ve listed it in the chart below as this road name hasn’t been offered yet by Bowser.

SHELL- Minitrix 3124 is also painted in a tank car scheme.  However, shell owned a series of cylindrical covered hoppers numbered, SCPX 3501-3533.  Both Delaware Valley and Bowser offered more accurate models of this series.

UNION PACIFIC-Minitrix 3123 represents a series of 200 cylindrical hoppers delivered to the UP, which Both Delaware Valley and Bowser offered more accurate models of this series.

UNITED CARBON COMPANY-  Minitrix 3122 is numbered for a series of later 4600 cubic foot center flow hoppers, however, the chart below lists a series of cylindrical hoppers with a nearly identical paint scheme.

Trix Cylindrical chart.png
CF Flexi Flo.jpg





   In 1964, the New York Central received a lot of 25 cylindrical pressure differential covered hoppers for hauling cement from American Car & Foundry.  The cars were successful and two more lots were delivered in 1965 and 1966 for a total fleet of 220 cars.  The cars remained in service with Conrail until the early nineties, when the cars were sold to Merchant’s Despatch and a few other private owners.  A few cars were transferred to non-revenue service as scale test cars as early as 1969, lasting well into the 2010’s.  The Conrail Historical Society now owns the sole surviving car, numbered 80019.


   Roco produced a model of this car for AHM in the early seventies.  It was offered in a variety of road names which did not include New York Central.  Fortunately, Eastern Seaboard Models re-issued the model in several New York Central, Penn Central and Conrail schemes.  However, the model differs from the prototype in having two elongated roof hatches instead of three round hatches and a lack of piping along the bottom of the car.  In addition, the vertical ribs along the bottom of the model appeared only on the first batch of 25 cars; as the two subsequent lots had two large square horizontal ribs.


   The chart below lists the Eastern Seaboard Models and AHM models separately, as the AHM models are stand-ins for two other prototypes; the early ACF 3500 cubic foot Center Flow cars and the later 5250 cubic foot Center Flow.  Of the three railroad names offered by AHM, all three had 3500 cubic foot cars, though none of the number series match.  The Great Northern Scheme is probably spurious, as the large goat logo was adopted with the big sky blue paint scheme.  All of the private owner schemes offered are numbered for 5250 cubic foot Center Flow series.  Finding dates and quantities for leased cars is difficult, but all of the numbers were listed in the April, 1966 Equipment Register.  A few of the schemes appeared on both types of cars.

Flexi Flow chart.png