Burlington Northern Trough Train

Mr. Trainiac Aug 3, 2020

  1. Mr. Trainiac

    Mr. Trainiac TrainBoard Member

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    I came across a thread on another forum about trains that modelers wish were available in the hobby. A few people mentioned the Trough Train, so here it is. The intermediate units are almost done, and I'm about to start on the end units. I had thought about making this car before, but finally felt inspired to do it now.


    Here are a few intermediate cars rounding a hypothetical 22" radius curve. The trucks under the articulation joints are just regular freight trucks, so I won't make a printable file for these them. It would probably be easier and cheaper to buy Kadee or Intermountain trucks. These are just stand-in dummys to check clearances. Intermediate cars on 22 Inch Radius.PNG
    The articulation joint is kind of strange on the prototype. It looks like the bolster of one end fits inside the adjacent car and the truck kingpin links them. While it's possible to model that on the computer, I wanted the cars to assemble like well car models (Think Athearn or Intermountain). Instead of an inside and outside bolster, there is an upper and lower. That allows for easy assembly and storage by simply lifting the last car off the tracks.

    The ends of the car are partially open to allow the 'trough' to fill in one pass. The side profile on my model is pretty close to the prototype. Each car has a sheet of metal that overlaps the next car's, and when the car rounds a curve, they slide past each other to expand or contract. I'm not sure that the floor of the articulation joint is totally correct though. Our models of course have tighter radii, so I needed a way to keep coal from falling through the bottom when the car flexes. It is a bit chunkier than I would like, but it keeps the car relatively sealed.

    However, I had to leave a bit of a gap between the 'male' and 'female' ends to allow for some error in printing and to keep the cars from binding on our imperfect model trackwork. It is most evident in the top view. Now you can experience the same problems the prototype did on your own model railroad Intermediate Male End.PNG Intermediate Female End.PNG Articulation Top View.PNG
    If you guys have any suggestions on how to improve the articulation joint, or you have more references for this car, don't be afraid to leave a reply on this thread. The door detail is kind of proto-guessed. The prototype underbody is painted black, so it is hard to see everything. I'm pretty sure the door's cross-sectional profile is accurate, but the hardware and hinge detail is just based off some basic car schematics. Who knows if I included everything.
     
    Last edited: Aug 3, 2020
  2. SLSF Freak

    SLSF Freak Staff Member TrainBoard Supporter

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    Cool project. I wanted to do this one as well but I've got too many projects on the burners right now. Glad to see someone doing it!

    -Mike
     
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  3. rch

    rch TrainBoard Member

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    First of all, excellent work so far! The way you handled the movable part between the individual units is very nice.

    I assume you'll handle the articulated joints like the A-line/Intermountain well cars, where a truck is attached to the "lower" articulated unit and the "upper" unit rests on top of the screw holding the truck onto the lower unit. The only concern I'd have is the inability of the car to absorb any torsion along the long axis because the bodies overlap. This would leave the trucks to be mounted somewhat loosely, say loose enough the truck could rock back and forth and side to side. I wonder if you could make the upper articulated joint have a combined conical and hemispherical cavity instead of a cylindrical through hole and have the lower articulated joint have a cylindrical shape with a hemispherical top, simulating a ball joint? This might allow the body to absorb any twisting action, though with the close clearance between the carbody sides through the articulated joint, it wouldn't be much motion.

    Here's a section view of the concept I'm describing which would allow almost five degrees of movement between units along the car's length. Again, the motion allowed between units rotating about the long axis through the articulated joints would be limited by the space between adjacent carbodies:

    articulated joint.PNG

    Athearn did something similar to this with their original 48' Gunderson Maxi Stack III five unit cars, but the "ball" part of the ball joint had a vertical pin that passed through the "cup" part of the joint effectively eliminating any rotational movement about the ball and limiting all the movement to horizontal motion about the pin. The cars were never very good operators. I've had success trimming the pin down on those Athearn cars and making more of the ball part of the joint so the concept works but it relies more on gravity to keep the units together than the original Athearn design.
     
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  4. HemiAdda2d

    HemiAdda2d Staff Member

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    Such a BN-distinctive car, watching to see this evolve into a model!
     
  5. rray

    rray Staff Member

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    Very interesting! What was carried in a trough train?

    Oh, I searched and found it was for coal. Nice looking paint scheme.

    Found some history too: 23 of the 13 section cars were produced, but quickly sidelined due to mechanical failures of the articulating panels grinding coal on turns, and the 33 ton per axle capacity actually ended up costing more to ship than an 120 ton aluminum coal car's 30 ton per axle capacity due to the fact that a failed wheel or brake stalled 460 tons of coal shipments vs 120 tons with the non articulated cars. Innovative, but didn't pan out.
     
    Last edited: Aug 4, 2020
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  6. Mr. Trainiac

    Mr. Trainiac TrainBoard Member

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    My main concern for this car, at least operationally, is going to be stringlining. The cars are all linked by the horizontally 'expanding' baffles, which doesn't give a lot of room for individual car roll. I think Ryan identified that potential problem too. Another thing I may need to consider is change in grade. As the car transitions from level to inclined track, the units need a way to pitch up in relation to each other, at least slightly. However, the units are so short that the angles between any two adjacent ones should be pretty small. Based off a schematic for the 5-unit experimental car, truck centers are only 21'5".

    My only concern with a ball and cup joint is that under tension, the hemispherical surfaces will ride up and over each other and come disconnected. An empty train especially will not have a lot of gravitational force to combat that tendency. I think we would need some kind of vertical surface to act on the tension to keep forces in the horizontal direction, which is why the pin coupling was my default. It is easy to make and to assemble the model on the tracks.

    I'll continue working on this model and get the two ends done, and them finalize the articulation system. Outwardly, the A and B end are pretty much the same. The brake equipment is between the articulated units, so there isn't much to look at on the ends. I made a model of one end yesterday and realized I messed up a pretty basic dimension, so I hope I can go back and change it without messing up all the subsequent measurements and details.
     
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  7. Mr. Trainiac

    Mr. Trainiac TrainBoard Member

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    Here is where the end unit stands right now: End Unit Underside Iso.PNG
    This is the 'B' unit; the A end will have the opposite articulation joint. Usually, we think of the B end as having the brake equipment, and while the 13-unit car has 4 brake wheels, they are all between articulated units. Neither the A nor the B unit has a brake wheel at the end. I did not include the end ladders either. I think Tichy parts will be better than trying to print all those freestanding details. However, there are grab iron holes on the sides. This view also affords a look at the bottom unloading doors. This is the best representation I could figure out. I don't have a ton of information to work off of; the chute ends are obscured by the trucks, while the door face is pretty slab-like in all the photos I have seen.

    I still need to make the single-axle truck that goes at this end of the car. The articulated joints have standard 100-ton trucks, while the A and B ends have single-axle pedestal trucks. The design intent was to keep axle loading at maximum efficiency: there wasn't enough weight on the end of the car to necessitate a 2-axle truck.

    A stencil on the car says 'National Castings Unitruck III'. The Unitruck II was used under the infamous Front Runner spine cars, but I don't know the differences between the two designs. The two types look pretty similar, so the biggest difference is probably the wheel diameter. The spine car had those small 28" wheels, while the Trough Train had the 36" wheels appropriate for a modern coal-hauling car.
     
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  8. rch

    rch TrainBoard Member

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    The end unit looks great from this view. I'm really surprised how much information you've been able to divine from the photos I've seen online.

    Do you have the Front Runner drawings from Model Railroader September 1985? They were very helpful to me when I did the Uni-Truck II for the Walthers Front Runner. I can send you the scan I have if you like.
     
  9. Mr. Trainiac

    Mr. Trainiac TrainBoard Member

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    If you would be willing to show me your Unitruck drawings, that would be great. Obviously I would have to make changes to the Front Runner design, but the suspension and the spring interfaces are what interest me.

    I was lucky with this project because I found a set of dimensions on a basic outline sketch. If you look on the internet, you will probably see the picture I'm talking about. The link may be broken now because I can't get it to full resolution, but I had saved the high quality version on my computer a while ago. With those major dimensions, I can build a body core and scale photos to measure the placement of the smaller details. Published drawings in the magazines are a valuable resource, but for unpreserved prototypes, we can't go back in time and measure them if drawings don't exist. This method is probably as good as it's going to get for more obscure cars.
     
  10. rch

    rch TrainBoard Member

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    Here's the scan.

    Front Runner Drawing MR 09-85.jpg
     
  11. Mr. Trainiac

    Mr. Trainiac TrainBoard Member

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    Here is where the Unitrucks are at right now: NACO Unitruck III.PNG

    I treated them as basically scaled up Unitruck II's. I increased the width so it was sized for 36" axles and changed the height dimensions a little bit too. There are a few minor differences between the two trucks, which I tried to at least represent. I'm not sure how totally accurate it is though. The retaining buckles on the ends look a bit different than the Unitruck II, and I omitted the lightening holes on the upper casting too. I wanted it to be more solidly mounted to the car, considering this will be 3D printed, and with the lightening holes, the sides just looked too flimsy for mounting in the tight space under the car. The basic structure is pretty much done, I may go back and add some fillets or round some corners to make it appear more like a cast metal piece.

    The rectangular protrusions fit into the sides of the I-beam to help prevent the sideframes from bowing out. The end sill rests on the opposite notch. I am debating whether or not to make this a one-piece truck or to keep both sides separate. With separate parts, it allows for easy assembly without fear of breaking the truck. Bending sideframes to get axles in their bearings always scares me, especially with the more brittle Shapeways resins. There is no chance of the truck being too narrow or too loose. The axle will fit every time because the modeler can set the spacing.

    On the other hand, it will take some skill to keep the axle centered under the car. I may extend the rectangle locators so they hit the coupler box to fix this. If both sides are pushed up against the coupler box, the axle should be centered.

    Tell me what you think about the truck assembly design. Should it be a one-piece casting or should each half be independent?
     
    Last edited: Aug 14, 2020
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  12. gjslsffan

    gjslsffan Staff Member

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    I vote independent. Great to see you guys working together on this.
     
  13. rch

    rch TrainBoard Member

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    If you're going through Shapeways, I'd definitely make the sideframe halves separate so you can assemble the trucks around the axle. I've done several truck designs and there's no way to get the plastic to bend enough to insert the wheels.
     
  14. Mr. Trainiac

    Mr. Trainiac TrainBoard Member

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    The Trough Train cars are live on Shapeways right now. I have them available in both the Versatile and Fine Detail Plastic, although some of the finer details like the I-beam flanges might not fare too well in Versatile. If I need to beef them up, I can, but at the same time, I don't want the model to look to chunky in Fine Detail either.

    The trucks and coupler box cover are included as a small sprue underneath their respective end units. Listing them separately didn't get over the minimum Shapeways price, so it is a bit more economical to just include them with one of the cars. And like most of my other models, finer details like grab irons and ladders are left to the end user. Decals are another story. Those will have to be custom printed.
     
  15. Ike the BN Freak

    Ike the BN Freak TrainBoard Member

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    Now this would be cool in N scale also...but does anyone make decals for the cars?
     
  16. Mr. Trainiac

    Mr. Trainiac TrainBoard Member

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    As far as I know, decals do not exist. I know a guy who prints his own decals, so if I ever print one, I may contact him. I think a few other printers do commissions too. I may need to rework some of the smaller details so they don't break on an N scale print. I don't have a timeframe for that though.
     
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