I am working on scratch building the train shed from Chicago’s Grand Central Station. The shed contained 14 or 15 (I can’t recall off hand) arched steel trusses. How would you make these?
I run a 1.5 million dollar fiber laser at work, but I think the detail is too fine to cut them out of steel. I’m thinking of making a jig and gluing 3/32 x 3/32 square balsa or basswood rods together.
I like the idea of the jig. I would probably make half-arches then at final assembly bring them together at the center.
I don’t think balsa has the strength or flexibility you would need. I would lean more toward Evergreen styrene using the laminated method and cementing the laminations with very thin solvent.
Then fit the diagonals in using your truss pattern. You could get fancy and use gusset plates at the major joints to help add strength.
I seem to recall a M-R article about an arched train shed that was laser-cut a few years back. I’ll see if I can find the issue.
[edit] It was september 2015, p. 26 Scratchbuild With 3D Printed Parts and it showed a fancy arch end wall. 3D printing may also be a logical solution especially since you need repetitive parts. Again, I believe making them in two halves would be a good way to go and if needed you could have a short filler section in the center if you needed to adjust the width at any time.
Meanwhile, take a peek at the train shed the folks at NAPM have built.
I agree with you. I kind of ruled out styrene because I didn’t think Evergreen made strips long enough for the arch, but they do. That is the route I will go. I will laser cut a steel blank to make the jig this afternoon. I will post up pictures of that.
I would maybe use a mold release or silicone spray in your jig before gluing up since the cement is going to seep through and cause enough sticking to make removing the truss tricky. Probably some careful slicing and prying with a #11 and a chisel-type Xacto blade.
Depending on your final thickness I think several layers of, say, .030 would probably do the trick. Looks like .040 is as thin as they go in the 24" length.
I believe Evergreen has bulk packs of the common sizes, too. (.040 x .100, 50 pieces, 24")
You might want to look up an article or series of articles Eric Bronsky did for Model Railroader years ago - his task was to built the elaborate and somewhat lacy looking catenary towers that the Insull interurbans (North Shore Line etc) used. But they also had to be structurally strong. His solution was a shape of clear acrylic or plexiglass (can’t recall which) with the structural shapes etched in and painted. So in a sense it was an optical illusion. But it was very convincing not only in person but in photographs.
True those were catenary towers, not trainshed supports. But the elaborate and complex look was similar and the need would be similar for greater structural strength than you might get from a totally accurate model built of plastic, metal or wood.
That will be a neat project! I can’t imagine having a tool like that and the knowledge to use it for modelling.
You mentioned that making the trusses out of steel might not work because of the delicacy. Do the truss components have to be exactly to scale? I doubt that too many modellers will be putting a micrometer on them to see how accurate they are. Perhaps increasing the width by 20% - 30% might make them strong enough while still maintaining the basic look.
I’m really excited about the project. Grand Central Station was torn down not long after I was born and about 10 years before my family moved to Chicago, so I never got to see it. I have done a ton of research on this project. I’m figuring the contruction of the station and train shed should take me close to a year. I have a lot going on these days.
I am very lucky to have the job I have. My job is in steel fabrication for a multi billion dollar company and includes running a cnc laser, cnc press brakes, cnc horizontal band saw, cnc plasma machine, cnc horizontal and vertical milling machines, cnc lathes, and I do some welding as well. Unfortunately, not much of this is applicable to model railroading!
If I were to make the trusses out of steel, they would be out of 12ga (.104") or 14ga (.075") material. I really don’t want to thicken things up too much and get out of scale.
I am going to make the trusses out of strip styrene. I will laser cut a jig to help assemble the trusses. I will make a cad drawing of the jig template this weekend and get started on the trusses next weekend. I will post pictures of my progress as I go.
The other thing I will fabricate at work is my turnout contol boxes. The switch panel will be laser cut and etched. Should be fun.
If I had access to such a laser cutter, I would cut them from a single sheet of aircraft plywood. You can get aircraft plywood as thin as 1/64" in 3 plies. It seems like 3/32" in 7 plies would work out to scale and be more than strong and stiff enough.
The cross section trussed ribs you’re looking to fabricate will be about 20" across by 10" high in HO, with struts about 0.10" square. In the scheme of things that is not too big at all. Michael Rose could cut them as a single piece on his home shop desktop laser. Your laser most likely has a much greater capacity. Cutting them as two half-pieces would be, well, half as big.
There are two large bridges on my N scale layout. Both are similar in nature to your proposed structure, and both are larger. The smaller one has a 30-inch clear span; the larger, 60 inches. The web struts and girders on each measure 0.10" by 0.10", about the same as what you propose. Photos posted on my layout build thread.
Here’s a photo of a couple of pieces I cut out from 0.093" (3/32") sheet styrene.
It was quickly designed and quickly fabricated. The pieces have only been minimally cleaned up and they are a little ragged. Just doing this to get an idea of how it could be built. The size is pretty close to what the posted image shows. I cut them out in pieces because my little micro mill is not large enough to hold the stock for a single piece. That would require a bed size of about 20" by 12". There are a lot of desktop laser cutters that can handle that size.
Keep in mind that these are only one bay of the inner ribs of the barrel vaulted structure. No telling how many are needed for the entire structure. The posted image shows some purlins and membranes and details and whatnot that make up the sheathing that forms the outer roof and walls. If I was doing this, I’d put a little more thought into how the fairing and skin of the structure would be fabricated.
The dimensions and layout can be worked out by any competent CAD guy, and the pieces can be fabricated by any competent machinist. The tools and equipment mentioned earlier seem more than adequate for the task.
What micro mill do you have?.. or did you build it yourself? I’ve been pondering building one myself.
I’m going to sit down tonight and start modeling the structure in Solidworks. That is when I will figure out more about how it will all piece together.
Thank you so much for your help and input. You guys are great.
Do you have more technical drawings of the prototype similar to the one you posted?
If so, or even if not, how much detail do you plan to incorporate into the model? Are you gonna be nit-picky and try to get a lot of fiddly bits in the model?
I estimate the model will be just over 6 feet long and about 2 feet wide and about 1 foot tall. Oh yeah, I assuming you’re working in HO.
I also estimate there will be about 6 bays with the full rounded roof (3 at each end) and about 10 bays with the clerestory roof. Is this close to what you have in mind? Technical drawing would clear this up. I’ve only seen a postcard of the old structure, so I’m only guesstimating.
Thanks. Not nosy, but I’m curious in a healthy, technical sort of way.
Yes, the layout will be HO. It’s going in a 1600 sq ft space. The station and train shed will be the centerpiece of the layout. I have debated to build the station and shed to scale or use some selective compression. I’m building it to scale… I think.
Edit:
If you look in the photos you will see the detail of the trusses.
Mighty impressive structure! 3D printing would be ideal to capture the detail but you would probably have to take out a second mortgage to cover the cost!
I followed the link and saw the photos. Plenty of interesting stuff.
Another few nosy questions to follow up on my previous nosy questions . . .
Do I understand that you intend to scratch-build the station as well as the train shed? Do you intend to include a few sidewalks and adjacent streets? Surely you’re gonna include the high clock tower? I figure such a complex (conceived as a working diorama-within-the-layout) would take up an entire 4x8 sheet. Possibly the stub end of a peninsula?
Have you worked out the area of the layout where this will sit? Have you started a thread for layout design and/or build?
I always admire someone who’s not afraid to think big.
Yes, I intend to model the entire station. Clock tower and all. it will go on a 18ft long peninsula.
I haven’t started a layout/build thread yet. I’m still working on the building it’s going in. Probably a few months away from that being done.
I have a few layout possibilities in mind. I will have some surrounding buildings and streets. I have plenty of photos to go off of. The Chicago river was the west boundry for the station. I will have the St. Charles Airline and B&O bascule bridges crossing the river. The track going through the city is all elevated. I will have plenty of viaducts and street scenes. The era I am modeling is the early 1950’s. It will be a combination of freight and passenger trains. I plan on having two freight yards that served the line (Robey St. and the Barr yard) as well as the lincoln coach yard.
I have done over a year worth of research, but I’m finally starting to get moving on it. I have 10-12 years until retirement. I doubt I’ll have it finished by then!
