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.

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   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.

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   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 one 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.


   Delaware Valley was the first to offer an N-scale model of an early ACF Center Flow, which is now available from Bowser in both three-bay and six-bay versions.  In researching these cars, I’ve noticed that the six-bay cars had a slightly higher capacity; 3,960 cubic feet versus 3,500 to 3,700 cubic feet for three-bay cars.   Generally, the models have the correct number of bays, and the few exceptions are noted below.


  A large number of these cars were leased by Shippers’ Car Line and North American Car, and Bowser offers a large selection of private owner road names, including several colorful fantasy schemes.  The chart below lists those schemes that correspond to actual car series, though I can’t guarantee that all the listed schemes are prototypical.  Sadly, what is missing is what was likely the most common scheme for this body style; a plain ACFX, NAHX or SHPX car.


BALTIMORE & OHIO- The B&O’s large fleet of cylindrical hoppers included both three-bay and six-bay cars; the chart lists the total for both types.  Bowser 37294 is numbered for a series of six-bay cars. 

BURLINGTON NORTHERN and GREAT NORTHERN- Though Bowser produced some of these road names on three-bay cars, I believe all of the prototype cars had six bays.

CENTRAL OF NEW JERSEY- The CNJ’s cylindrical hoppers were leased from North American and differed from the model by having two bays, four roof hatches and low handbrakes.   These 2,700 cubic foot capacity cars were used for hauling sand.

CONRAIL and PENN CENTRAL-  Some of the Bowser models for these road names are six-bay cars; however all the cars inherited from the New York Central, Pennsylvania and Erie Lackawanna were three-bay cars.  The totals for Conrail include the two-bay Jersey Central cars.

EAST ERIE COMMERCIAL-  Bowser 37841 represents a series of former Pillsbury (PBLX) modern four-bay cylindrical hoppers patched for the EEC.  Though Intermountain offers a more accurate body style, I don’t think it’s been offered in this scheme.  The cars still carried their original reporting marks in the July, 1999 Equipment Register, so this a post 2000 scheme and not included in the chart.

GRAND TRUNK WESTERN- GTW’s cars were acquired second-hand from North American Car; they had low handbrakes and initially wore a plain grey “patch” scheme.

ILLINOIS TERMINAL- Bowser 37287 is numbered for series 110-124; I haven’t been able to confirm that these 3,800 cubic-foot capacity cars were cylindrical hoppers, but two other series 100-109 and 125-134 match the dimensions so all three series are included in the charts.

MISSOURI PACIFIC- All of the Bowser models are numbered for a series of 300 cars originally built for Texas & Pacific subsidiary Kansas, Oklahoma & Gulf.  These three-bay cars differed from the model in that the roof walk did not extend to the ends of the car, much like AHM’s Flexi-Flow models.  A series of 100 leased cars (LOCX 709900-709999) were identical.  Both series were re-lettered to T&P with no change in number before being re-lettered again for MP in the late seventies.  In addition, there were 400 conventional six-bay cars numbered MP 710200-710399 and T&P 710400-710599.  The quantities in the charts include all the above cars with MP reporting marks.

NORFOLK & WESTERN- The totals in the chart include the original Norfolk & Western series (71850-71899) as well as former Wabash cars (332950-333050) which were repainted after the 1964 merger.

SHIPPERS’ CAR LINE-  ACF leased cars through their Shippers’ Car Line subsidiary.  Around May of 1968, Shipper’s Car Line changed their reporting marks from SHPX to ACFX. (A few Center Flow demonstrators received ACFX reporting marks as early as 1962.)  The Equipment Registers did not distinguish between ACFX and SHPX cars until the January, 1987 issue, which listed only seven SHPX cars.

WILKES BARRE MILLING-  By 1981, the WBMX reporting marks were registered to Lauhoff Grain.

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   In 1964, ACF introduced the “classic” Center Flow familiar to modelers.  The early cylindrical body was replaced by a teardrop shape which optimized the amount of usable space.   Atlas 2321 is a model of the first Center Flow; a 5,250 cubic foot car, which was highest capacity covered hopper at that time.  The new design was successful, and a large number of Center Flow hoppers were built in a wide variety of capacities and configurations to suit specific commodities.  Construction lasted for decades, and numerous changes occurred over the years.


   Our N-scale models can be grouped into three categories:

1- Cars constructed between 1964 and mid-1966 were constructed with high hand brakes and full side ladders.  These early cars had a horizontal rib across the side near the top of the car.

2- About June 1966, new freight car standards went into effect, requiring low hand brakes, short side ladders and end platforms.  Full height end ladders were retained to permit access to roof hatches.

3- Late in1971, the horizontal rib near the top of the car was replaced with two small beads along the top chord of the car.


   Other changes occurred over the years, and later Center Flow hoppers differed a bit from the models, and some models are stand-ins for similar cars from other car builders.   






   Two-bay Center Flows are available in N-scale from four different manufacturers:  Athearn offers a model of an early Center Flow hopper with a low handbrake, which is appropriate for cars built between 1968 and 1971.  The Atlas, Intermountain, and Micro-Trains models all represent late Center Flow hoppers as constructed in 1971 or later.  Although information on schemes later than the mid-eighties is outside the scope of this website, I’ve included all schemes in the chart below.  For roads that owned both early and late cars, I’ve separated them in the charts wherever possible.


BURLINGTON NORTHERN- Upon its formation in 1970, BN inherited about 430 early Center Flow hoppers from the Burlington, Great Northern and Northern Pacific.  The 1980 acquisition of the Frisco added about 245 late Center Flow hoppers.  This ratio remained roughly the same into the merger with the Santa Fe.

CHICAGO & NORTH WESTERN- The C&NW owned three series of early Center Flows totaling 460 cars. The first series, 96620-96769 was delivered in 1966 and had high handbrakes.   A series of 100 late Center flows was delivered in 1976.  Intermountain 66542 is numbered for a series of similar cars built by Thrall in 1994.

CSXT- CSX inherited early Center Flows from Western and Monon as well as a large number of late Center Flows from the Baltimore & Ohio and Chesapeake &Ohio . Micro-Trains 09200390 represents a series of similar 3,250 cubic foot hoppers built by Gunderson in 2013.

GREAT NORTHERN- According to “the GN Color Guide” only three cars were known to have been repainted into the blue scheme.

GRAND TRUNK WESTERN- GTW’s cars were early Center Flow hoppers obtained secondhand from Shippers’ Car Line; they don’t seem to have been given full GTW paint jobs until the eighties.

MONTANA RAIL LINK- These models represent a series of similar 3,000 cubic foot cars built by Thrall in 1992.

NORFOLK SOUTHERN-   Atlas 39221 is numbered for the series 233000-233485 which were former Norfolk & Western cars.  This series is listed in the chart as the cars most closely resemble the model.  Micro-Trains 9200240 is numbered for the series 294220-294319, a group of 100 similar cars built by Thrall in 1998.  Athearn 12493 is numbered for series 235100-235674 which were former early Southern 3,200 cubic foot Center Flow hoppers with trough hatches.   The July 1999 Equipment Register listed 197 cars in this series.

ROCK ISLAND- The Rock Island adopted their new “Rock” image in 1975.  The January, 1979 Equipment register listed fifty-seven two bay Center Flow hoppers with ROCK reporting marks.  The Rock Island folded in 1980, and the bulk of their cars went to the Union Pacific.

SOUTHERN- With a capacity of 3,300 cubic feet, Southern’s hoppers were about ten feet longer than the model and had trough hatches on the roof.  The first series,(91000-91599 ) were early Center Flows delivered in 1971, while the second series (91800-92099) were late Center Flows delivered in 1976.  Except for the L3 stencil, Intermountain 66519 appears to be an “as built” scheme, though some cars were delivered with the name in green (A scheme that Intermountain canceled).  Micro-Trains 92120 is numbered for the second series, but could represent either series as repainted in the eighties.

WINCHESTER & WESTERN- Atlas 50001308 and Intermountain 66514 are numbered for a series of cars delivered in 2005, however series W&W 7001-7300, delivered in 1997, were similar.


SHIPPERS’ CAR LINE (ACFX)- In 1968, Shippers’ Car Line produced at least four different demonstrator schemes on two-bay Center flow hoppers. Three of these schemes are available in N-scale, though the Atlas and Micro Trains offerings have L2 stencils which date them to 1973 or later.  Presumably, demonstrator schemes were one-of-a kind, however all four manufacturers offer models of a plain ACFX car with L3 stencils that could be backdated to L2 stencils.

NORTH AMERICAN CAR- Atlas 3912 is numbered for a series of early Center Flow hoppers leased to Corning Glass.  Athearn 12263 is numbered for the same series, but is decorated in a plain scheme.  The quantities listed in the chart for the Athearn car represent the total number of NATX cars matching the dimensions of a two-bay Center Flow.  

PQ CORPORATION- The model has a built date of 6/74, when the company was known as Philadelphia Quartz.  The name change occurred in 1978, however, the L3 stencil on the model dates it to the eighties.

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   The 3560 cubic-foot Center Flow hopper filled a niche for transport of commodities that were less dense than cement, but denser than grain.  Judging by the paint schemes offered by Atlas, the commodities were primarily salt, potash and fertilizer.  The Atlas model is offered in a variety of road names spanning a time period from the late sixties to the present day.  Though most road names are accurate for the model, some represent similar covered hoppers; those that differ are indicated by a note in parentheses in the “ROAD” column of the chart below.  A number indicates the cubic capacity of the prototype, while “late” indicates Center Flow hoppers built after 1971 that lack the stiffening rib near the top of the car.  “NSC” indicates similar cars built by National Steel Car of Canada for hauling potash in the 2000’s.  Other differences are outlined below.


CHESAPEAKE & OHIO / CSX- The C&O received two series of cars; the first series (601200-601299) had a single trough hatch instead of five round hatches.  Both series are included in the chart below and both were used for hauling salt.


DELAWARE & HUDSON- Atlas 5000387 is numbered for a small series of two-bay Center Flow hoppers that were about six feet shorter than the model, had a 3,200 cubic foot capacity and high handbrakes.


SOUTHERN / NORFOLK SOUTHERN- Atlas 50002281 is numbered for a series of 1,200 similar 4000 cubic-foot Center Flow hoppers delivered in 1969.  An additional 500 cars numbered 99200-99699 were added in 1974; they were late Center Flows and are not included in the chart. 


SHIPPERS’ CAR LINE (ACFX)- Shippers’ Car Line was the leasing division of American Car and Foundry.  While some leased cars bore the logos of their lessee, most did not, particularly after the seventies.  The quantities listed for Atlas 39919A indicate the grand total of all ACFX 3650 Center Flow hoppers.  Little information is available on leased cars, but what little I could find is listed in the 7/69 column.  The dates listed for leased cars indicates the earliest date for the scheme without regard to the consolidated stencil on the model


GENESSEE & WYOMING (GWIX)-  The number series for Atlas 50000536 doesn’t appear in any of my Equipment Registers.  However, the GWIX reporting marks first appear in the January, 1987 issue and listed a fleet of covered hoppers used for hauling salt from a mine near Rochester, NY, so the model could at least be a stand-in. 


GEORGIA PACIFIC (GAPX)- The reporting marks had changed to GPPX sometime between 1979 and 1981 as Georgia Pacific had transferred them from their Southern Division to their Portland (OR) Division.


INTERNATIONAL MINERAL (IMCX)- The quantities listed for Atlas 50000538 list cars that had been renumbered into new series and presumably repainted, however, cars from the original series were also repainted into this scheme.

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