3D Printed 28' Flat Cars with Wood Beam Trucks
Years ago I bought 3 28 foot flat car and truck kits from Alkem
Scale Models. I built these up and found that they were fine
models of the typical type flat car that the USMRR used at City
Point. There were at least 28 of these cars at City Point.
Though they aren't seen very much in images of the line outside of City
Point itself , they are in many images taken at City Point.
Ordnance Wharf at City Point. Crop of Library of Congress image (LC-DIG-cwpb-01978) showing flat car loaded with lumber.
It can be seen in surviving images that they were used for carrying sand
and lumber, among other things. One was even built up into a stock
car. Since I am
primarily modelling City Point, I needed a lot more than 3 of these flat
cars. Alkem Scale
Models no longer sells the kits and the likelihood of finding NOS or
built up kits is small. Bachmann's old time flat cars are a scale
40' long, much longer than the originals. I decided I had to
recreate them with my 3D
printer. I figured that having them match my existing
models would be easier if I just took measurements from the Alkem
models. I could have started from scratch and modeled them
from surviving documentation and images, but I really like the
appearance of the Alkem models and wanted to make my new ones to
match. I am pretty happy with the result.
To the left, is an original Alkem flat car. Two of my 3D models
are to the right. The shading and weathering of the cars is
a bit
different, but the bottom line is that there is no glaring
difference,
so that the overall visual effect of this scene remains coherent.
The
Alkem car has a bit finer detail, but I think that is mostly due to the
limited resolution of my entry level filament printer. You may get
better results with a better 3D printer.
Coupler and Truck Considerations
I'm currently using anachronistic #5 Kaydee couplers on my layout and
built pockets for them into the model. The ears and tube on the coupler
covers that come with the #5 Kaydee kits are trimmed off to make them
fit. I use #4-40 x .25" machine screws for connecting the trucks and
couplers. I use 5/64" and 7/64" drill bits to clean out holes for the
screws. 5/64" for the pilot holes that the screws go into and 7/64" for
clearance holes (trucks and the coupler cover). The couplers hang a
bit low according the Kaydee gauge, but they seem close enough for my
purposes. It will be pretty easy to increase height should there be
problems, as the coupler boxes are modeled as a single object in the
design file. I don't have a 4-40 tap, but for brittle resin models you
may need to use a proper tap in order to avoid cracking the model.
There is very little clearance for the trucks to swivel, but they seem
to work fine on my layout which has prototypical radius curves and #6
switches. If you have tighter turns or switches you may need to do some
modifications. I am using modern 33" wheelsets for the time being.
Prototype and Model Image of the Same Scene
.jpg "Flat Cars at Repair Shed (LC-DIG-ppmsca-08267)")
Above is a crop of a Library of Congress image (LC-B8184-10465) Showing a string of flat cars at City Point.
3D Files
I modeled the flat car and trucks using a program called Blender and printed them on a Bambu Labs A1 mini.
Here are the 3D files used to create the trucks. The trucks need
to be a bit flexible in order to fit the wheels, so I think there may be
problems with typical resin type prints. I used a standard eSun
PLA filament and did break a couple of trucks getting the wheels in, but
the cost to print is so low, that I consider that a minor issue.
The Alkem trucks use nylon(?) bearings, but my trucks do not appear to
need them. I do think that rolling resistance could be slightly reduced
if quality bearings were used. For the ends of the cars without brakes you can simple cut off the brakes.
A blend design file can be downloaded: truck_w_brake5.blend
A .stl file that can be used for printing can be downloaded: truck_w_brake5.stl
Next are the 3D files used to create the flat car bodies. Since
there is no need for flexing the structure in this design, I think resin
printers should have the potential to make a finer print than I was
able to accomplish.
A blend design file can be downloaded: flat car23.blend
A .stl file that can be used for printing can be downloaded: flat car23.stl
Follow on Work
There is a lot of potential for adding to this basic car. For
instance, here is an image of a stock car at City Point that I believe
was constructed on a flat car chassis. This is coupled to a
passenger coach. Enlisted men did not travel in coaches, so I
assume that the stock car was intended for transportation of the
officers and VIPs horses.
Crop of Library of Congress image (LC-DIG-cwpb-01855)
Here is my version of that car at the same location on my layout.
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