STC Shops: AHM Flexi-Flow Kitbash

A car rarely seen outside home rails (uncredited internet photo)

The ACF "Flexi-Flo" covered hopper is surely among the most unusual railroad freight cars in the US. Developed with the New York Central RR in the late 1950's, the Flexi-Flow hopper was an alternate take on pneumatic pressure-differential "rapid discharge" dry bulk hopper designs such as Pullman-Standard's "Airslide". In this function it served very well, and most of the cars built are still in use today over 40 years later. But close inspection of its design and construction reveals it to be a rare "working prototype" leading toward the development of the far more ubiquitous Cylindrical and "ACF Center Flow" hoppers that appeared within a decade of this one. To wit, if built with a full-height ladder cage, it might look similar to a Cylindrical hopper. But since cylindrical designs of this size were not yet proven for strength, the round hopper body appears to be resting in a crudely braced "cradle" of sorts. Of course the protective / strengthening end cage is completely missing, with naught but a couple vertical posts for crews to grab. It's truly an odd, evolutionary design. The second batch was a bit cleaner in appearance with numerous modifications, but still retained the low, open end platforms and "cylinder in a cradle" (hotdog in a bun?) appearance.

Only a couple hundred Flexi-Flos were built, in two different batches, all for the New York Central RR. Since they were so specialized and only owned by one Class 1 railroad, they were (and are) rarely seen outside of a handful of assigned routes in the northeastern US. Nonetheless, with their headquarters in the NYC's backyard, AHM solicited a model of this car from Roco of Austria in the early 60's. And it's been a sort of enigma in the hobby ever since!

Before the internet, this was a car relatively few people had ever seen in real life. Compounding the confusion, AHM themselves mistakenly called the car a "Center Flow Hopper" even though those cars - direct descendants thought they were - are far, far different! But the crude tooling made it even more difficult to understand certain features: The large posts angular on the ends of the car certainly did not look like handrails. The walkways were a scale 7 inches thick and devoid of detail. And those who actually were familiar with the real life cars found significant errors such as pneumatic plumbing on both sides of the model (instead of one), oval roof hatches (instead of round), and blocky, solid end panels (instead of smooth and hollowed).

In a final and most surprising bit of irony, AHM never even offered the Flex-Flo in the New York Central paint scheme! Aside from a handful of plausible private-owner cars, the only railroad schemes offered were for western lines - about as far from the real cars' home rails as one could get!

Even now, the only way to get an accurate model of the Flexi-Flow is to spend a couple hundred dollars on an imported brass model - if you can find one.

My challenge in this project is to turn the lowly AHM car into a respectable model.

But why bother? Blame the following photo:

Look closely under the grime and layers of paint...

There's a ton of backstory hidden in this weather-ravaged car. Recently, it even used to look like the car at the top of this page and believe it or not, the two were photographed right next to each other. But three decades later, this particular car is stubbornly betraying not just one, or two, but THREE of its previous identities in a railroad history lesson! If you look at the right (closest) end of the car, you'll see a mish-mosh of weatherbeaten logos covering each other in varying degrees of preservation and decay:

- The first owner, New York Central, is evidenced by the top curve of their oval logo, which is obscured by...
- The infamous Penn Central "Mating Worms" logo... in the photo appearing as some condensed black lines, obscured by...
- The remnants of the Conrail logo, which kept Penn Central's carcass under wraps from 1976 through 1999.

More recently, this car has been sold to a fourth, private owner, as evidenced by the "MDTX" reporting marks. But the identity crisis doesn't end there:

- The car number on the end does not match the one on the side (which incidentally makes the photo a rare piece of evidence of a major shop goof)...
- And the large "Flexi-Flo" lettering is brandishing its Turquoise glory all the way from the 1960's when the NYC first applied them. Truly an amazing and ironic display of real-world weathering!

My goal is to paint and distress my model to look exactly as the real one does above. But first, I need to correct the numerous deficiencies in the old AHM model:

The victim lucky donor. A typical AHM example, found at the Haunt in 2006. For starters, compare the thick, fat, angular posts at the ends of the model, to the slim and curvilinear wireform hand grabs on the real cars! The problems don't end there. AHM even decorated this example with a Build Date of 1927!

The car needed to be hacked up quite a bit, and that's just for starters! First, the black "detail parts" (walkway, ladders, etc) were removed. Then I had to cut, carve, and remove the cast-on walkway supports (easy) and roof hatches (difficult). Resulting and original holes were filled with green putty and sanded for contour. The incorrect end panels were cut out, and the inner cylindrical contours were refined.

New end panels scratchbuilt from sheet styrene... also that nasty gap between the original & separately-cast roof panel and the ends proved to be a mild challenge. The gap was simply obscured by the walkway, previously. At this point I was unsure if the roof should remain removable, so I needed to make a curved brace beneath in order to layer putty on top. Bah.

Using clues provided in the original model's tooling, I decided to replace the end platforms with brass diamond plate. I have yet to find a conclusive overhead shot of the real cars to determine if the platforms were hollow like a typical walkway, or standard solid diamond-plate. A case could be made for either. In the end, I decided a hollow platform would add visual interest. If that turns out to be grossly inaccurate or look ridiculous, it will be easy to add thin styrene underneath.

There are no commercial walkway kits designed specifically for the Flex-Flow. So I adapted a couple of Center Flow kits to match. Here, the stanchions are installed...

...followed by the walkways. This is a test-fitting. I later went back to rearrange the thick and thin supports to match the real cars, and adjust the end walks to more closely fit the curved roof without a gap between.

The pneumatic piping has been cut away. The original model had bulky, solid supports that needed to be removed, in favor of "hollow" sheet-metal support brackets that I am scratch building from Athearn stantions.

Shot of one of the ends, showing the access hole. The brake and pneumatic air reservoirs will go here, and need some complex piping I will have to fabricate from wire.

This project is maybe to the halfway point. I need to build and install the end ladder posts and intricate, curved grab irons. Plus the aforementioned air plumbing as seen on the ends. Only THEN can I design the custom decals which will be necessary to finish the whole thing....

MORE TO COME

EDIT May 02, 2009

Finally some progress to report; details below the photo!

I made numerous mistakes on the roofwalk, owing to naught more than sheer laziness when it came to printing reference photos. ALWAYS print your photos and keep them at the bench! I'd originally installed the vertical supports at the joint where the horizontal reinforcing rib meets the curved carbody. This because it seemed to offer the best fit for my parts, which were sourced and adapted from a Plano kit for Cylindrical Hoppers. But, reviewing photos later, I realized the posts were supposed to extend flush with the outer edge of the rib! So I had to remove all those fine parts without destroying them (again), redrill fifty-two #79 holes, and reinstall. This of course extended the width of the end walks by a scale 8 inches, but I'd previously trimmed them to the smaller length. Thankfully I was at least wise enough to keep the bits of scrap from the initial trim!

I rebent the end walks to place the "hump" slightly off-center; when adding the trimmed scraps to the short side, this recentered the hump over the end of the car. While the seam is not entirely invisble, it works, and given that this car is supposed to display 40+ years of service-abuse as I'm modeling it, a few rough edges certainly won't hurt. That's also my excuse for the fact that the Plano roof supports, having been designed for Cylindrical Hoppers, aren't quite the exact dimensions to fit the curvature profile of a Flexi-flow, and as a result bow out just slightly; I'm hoping that's less noticeable once they're buried under a nice coat of flat gray paint. Er, primer.

The piping for the brake and pneumatic discharge air reservoirs proved to be aggravating. I searched the junkbin for approximate parts for the reservoirs and valves, then custom-bent .80 brass wire for the piping. I wanted the piping to be sturdy, which it was to a fault; very difficult to make adjustments for fit and correction. And now that it's finally in place, it almost looks a hair too big. Oh well, I'm not messing it up again now. This was not intended to win any museum-build contests, but to illustrate some of the interesting features of these cars better than the original model.

To that end, my scratchbuilt grab posts were more successful, if highly tedious and aggravating. I bent the same .80 wire to the signature curve profile, inserting the curved end into .80 holes drilled into .40 styrene posts. The fits need to be exact in order for the posts to remain vertically plumb; I'm happy to say all look acceptable, but I won't be doing this again any time soon!

Add proper wire stirrups as well as some sill grabs (not shown in the picture), and I'm almost ready for paint! Just need to add some more wire bits and find a proper brake wheel...

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UPDATE May 14, 2009

Nearing completion of the build phase, I applied a quick coat of primer to get a better feel for what work remained. I'd initially feared the brass wire would be too big, but with the shine removed it actually looks like an appropriate size! Without the mishmosh of colors and materials, it almost looks like a real car. The discolored portions of the roof where the filler still shows, look somewhat like lading spillage and will blend nicely with weathering to come. The primer leaves an awesome, slightly textured flat finish and were it not for the decal work still necessary, I would leave it this way. As it is, I plan to leave the ends and sills as they are, and only treat/paint the main body where decals will go.

A preview of the decals I am working on. I am drawing all the graphics - including the Penn Central and Conrail logos - from scratch. Fortunately I had a font that perfectly matches the Flexi-Flo herald, so that saved a bit of time. That's never happened before!