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Peter's Model Railroading | The Layout | Equipment | PRR GLa
Construction: Hopper


To be able to get the hopper body itself as square and level as possible, I decided to build a simple assembly jig out of strip wood glued to an MDF base. In the background you see the raw parts of the hopper body, consisting of 0.020" sheet styrene. The smaller end pieces, all six of them, are clamped together to make sure that they are all the same size. They are cut to be a scale 9'5" long and 2'6" wide (should be 2'6-11/16", but that fraction is just too hard to measure, even in S-scale). The bigger sheets are side panel sheets cut to 7' wide, and they will be trimmed to 30'9" in length.

It took me a while to figure out how to get the hopper body's slope. However, it turns out that the top of the hopper stands at 10' above the rails, while the hopper body is 7' tall. This means that there is 3' between the bottom of the hopper body and the rails. Since one of the scaled drawings available for this car shows that the bottom of the hopper buckets are 12" above the rails, that means the buckets are 2' in vertical height. The scaled drawing also shows the two tips of the buckets are 8'2" apart. Given those measurements, I used two scale 12" strips of styrene, placed them against a metal ruler, and then taped it all to the hopper body side panel. I had marked the center of the hopper side panel and then measured 4'1" to the left and right of that mark, and drew two vertical lines. I also placed a mark at the ends of the panel at 2'6" down from the top. I could then draw a line from the 2'6" mark diagonally to 4'1" lines off of the center mark on each side, extended down the 2' of the scrap styrene strips. This effectively gives me the line of the hopper's interior sloped sheet. The final mark that needs to be made is the short vertical line, which represents the vertical part of the cut-out of the side panel. This was made at 4'2" from the ends of the body, as per the scaled drawing. The scratched-out section of the side panel will then be cut out.

I marked all six side panels, and then removed the cut-out. I did that by cutting through the styrene at the shorter vertical line, and then using the score-and-snap technique to snap the diagonal line. The six parts are now ready to be assembled into the three hopper bodies.

I then placed the four parts making up one body around the strip wood jig I'd built, and using metal squares, verified and glued the parts together. The side panels are a bit too long, so they will need to be filed down. Also, because of the 0.020"-thick styrene used, the parts bowed out a bit, but that will go away once they are mounted to the frame and other structural parts are added. 0.020" comes out to 1-1/4" thick steel in S-scale.

Filing the ends of the bodies down was easy and left a nice smooth corner.

It was then time to glue the hopper body to the frame. I put the body back on the jig, so that I knew the corners would be square. I used these miniature clothes pins to the clamp the frame to the body. I centered the frame, by eye, on the body and made the bottom of the body be flush with the bottom of the frame. Three clamps on each side held it all in place. It was then just a simple matter of applying Testors styrene glue to the joint.

And here's where we stand now. Three bodies on the track. Part of the reason why I stopped working on this project in 2014 was that I thought building the bodies would be difficult. I also had this mental picture to get to the stage shown in this photo would take a very long time. It is weird how the mind can fool you. Now that I know how to build the basic shape of the body, it is actually quite easy.

The corner braces are cut from scale 4-inch styrene angles. I cut them roughly to length, leaving myself a bit of a spare, and then file down one side of the angle to just about 10 inches (the height of the frame). I then glue it to the frame and to the hopper. These should line up perfectly, but they didn't quite.

The angle braces butts up against the end sill of the frame (which is where part of the angle was filed away from). When the glue is dry, I cut and file the top of the angle bracket to match the top of the hopper.

This is the drawing for the large slope sheet. The triangles in the bottom left and right need to be cut off from the main piece. These measurements were not based on any prototype drawings or measurements, just what I needed to get it to fit correctly and be in the correct position.

These are the outside sloped sheets of the hopper. I made mine out of 0.040" styrene, so that their extra thickness would help with the solidity of the hopper body. Also, I am planning on have my models carry a live load, so they need to be sturdy. I cut two pieces, each a scale 13' by 9'5". I then marked a line 6' from one edge. To clear the center sill of the frame, the central portion of the piece has to be cut out. This is set in 3'11" from each long edge, leaving 1'7" of material to remove. I made a few passes with the knife along its short edge, and then used the knife to cut all the way through the long edges. This then allowed me to snap the center piece out with only minor clean-up. The outside edges need to have a 2" strip of material removed (up to the 6-foot line) so that the sheet clears the outside frame members. Also, the "exposed" part of the sheet needs to have a chamfer-cut of material removed because the hopper bays slope in toward the center of the track, to aim the load into the chutes below the track. The dimensions of this triangle were determined based on the S-Helper Service's PRR GLd model I have, presuming that most hoppers of that time were built in a similar manner. All of the hashed parts of the sheets in the photo below are what needs to be removed.

It was then a matter of lining up each sheet with the outside of the angled section of the hopper's side panels, and pushing it flat against the end panels. While holding that delicately in my hand, I glued one angled edge first. I set it aside and let it dry for a while. I could then come back and glue the other edge to the other side panel. Finally, I pushed the end panel toward the sloped sheet and glued it down. There tended to be a slight gap there, but there will be strips of styrene placed over those seams soon, as per the prototype. I then did the other sheet. The quality-control step here is to make sure that the sloped sheet sticks out, vertically, a scale two feet below the bottom of the car's frame. Ideally, the bottoms of the two sloped sheets should be separated by 8'2". I was unable to attain that, being a few inches short.

Not knowing the actual dimensions of the inner slope sheets of the hopper, I used this contour gauge to get a profile of the interior of the S-Helper Service's GLd hopper model that I have. I used that to come up with measurements.

However, later as I was starting to build the inner slope section, I realized that the GLd has a vertical edge to it before it gets to the hopper doors, while the GLa doesn't (which you can make out from the prototype photo I've included here; see the orange line pointing to the inner slope's rivets). This actually makes the construction of the inner slope pieces easier.

Before I had realized that, I had already made a side-profile piece out of styrene (bottom piece in the photo below). Only the top, pointy side of the profile turns out to be needed. To get the slope, I made that top section 5 scale feet wide and the point is 15" above that. For the actual inner slope assembly, I cut two pieces of 0.040" styrene 2'10" wide and 9'5" long (matching the interior of the car). I put a slight chamfer along the edge where the two pieces were to be glued together, so as to increase the gluing surface. I then glued them together, and made two triangles that match the side-profile's slopes to act as the braces (which will not be seen).

When the glue had dried thoroughly, I put the piece right-side up and rubbed it on a flat piece of sandpaper to give it a flat bottom edge, making sure not to go beyond the outside edge (to preserve the part's overall width). This makes it easier to glue the hopper doors to it later on.

Installation couldn't be easier; just drop it on the center sill and the outside edges land on the side sills. I eye-balled the position so that it is centered between the outside sloped sheets, and then glued it into place.

The next step is to make and install the hopper bay doors themselves. Again, because my models are expected to carry a live load, the doors need to be sturdy and glued into place. I cut a section of 0.040" styrene to match the length between the top of the inner sloped sheet and the outer slope sheet. I then cut that section to length such that it fit in between the center and side sills at the bottom, and made a chamfer on one corner to line up with the 2'4" bottom of the outer slope. The photo shows two of those pieces glued in place; 10 more to go. These hoppers bays have some complex angles!

Here's a view of the interior of the car with the doors glued into place.

Next up are the side walls of the hopper bays. I thought this was going to be difficult, but it turned out to be fairly straight-forward. I cut a piece of 0.040" styrene to the rough length of the bay's side, and then held it in place and traced out the outline of the bay with a pencil. I then cut the triangular piece of styrene to those pencil lines. Next, I glued the piece in place and gave it plenty of time to dry. I then used an Xacto knife and shaped the piece to match the profile of the bay.

I used that same method on the exterior side walls. Those, however, I made out of 0.020" styrene, because I didn't want them to be even with the side sills. Here you can see the pieces marked off, cut to the mark line, and then glued in place. I am getting ready to shape them to the profile of the bay. I used wood-carving methods to get the pieces shaped. It is very easy to damage the rest of the styrene model, so it is important to take your time in this step. Of the twelve bays the knife only slipped once, but I was able to back-fill that with some slivers of styrene. Gaps will be filled in later.

And here is a view of the underside of the car with the hopper bays essentially finished. Door details, etc. still need to be added, but the basic box is done.

And here is the interior view up to this point. The next step is to make the top "hat" over the center sill.

Yes, I really am building three cars at the same time!

The orange lines point to the angled caps that sit on top of the car's center sill. These were made the old-fashioned way, by hand-filing and cutting and fitting. Trying to get the angles right at the ends was definitely a chore. At first I was going to make these out of two pieces of styrene glued to each other at the appropriate angle. However, I just couldn't see how the top of this section was going to come out nice and crisp. So, I let it sit there for a few days. Then one morning while bike riding, the idea came to me to use a scale 12"x12" strip of styrene, and essentially cut it in half diagonally. When I got home, I measured the diagonal of the piece, and sure enough, it was almost exactly the width of the center sill. I then used my electric bench grinder to get rid of most of the throw-away half of the styrene strip. I then used a disk sander to file it smooth until it was just shy of the diagonal cross-cut line. The rest of the filing was done by hand. This all took a substantial amount of time and got quite tedious, having to do this six times.

When I was finished with adding those top strips, I noticed that there was a gap from the center sill's C-channel pieces visible inside the hopper bays. I have no real good photos of the interior of a prototype GLa, but the S-Helper Service GLd interior has this closed off. So, I used a scale 4"x8" strip of styrene to fill the interior of the C-channel. I had to file it down both in its width and thickness to get it to fit. After shaping, I slipped the piece in from the outside, by the end sill, and then pushed it all they way until it covered the interior of the bay. In the photo below, you can see the covered bay on the right and the uncovered one on the left. A strip of 4"x8" styrene is included in the photo to show what I used. Each bay has its own piece, so I had to do this 12 times. Let's just say, I am glad I am only building three cars at a time. However, in the future, I may add these pieces before I build the bays, or consider using a solid piece of styrene for the center sill.

Some model photos I've seen include a strip of metal around the angled caps' ends. I used a strip of scale 1"x4" styrene and formed it to look like the piece shown in the extremely close-up photo.

I glued those around the edges on all four ends.