3DPrintedRailRoad Infrastructure

Turn-Table

Any self-respecting railroad needs a turntable for obvious reasons.  This turntable can be used as a center of a roundhouse (more about this later) or as a center switch for multiple track paths.  The basement layout used the turntable for both as shown in the photo.

Before you start printing you will need some hardware (nuts and screws).  You’ll only need one of each for this project but purchase a supply if you intend to construct other projects such as the rolling stock.  I use M3x10mm stainless steel cap head screws for a lot of projects.  The US based big box hardware stores generally don’t have this size.  So, you can use McMaster-Carr , an internet supplier I’ve found, or do an EBAY search.   Here’s your McMaster-Carr shopping list with the recent prices:

Description                           McMaster-Carr Part Number          Cost

“M3x10” x100 QTY 1 Stainless Steel Screws      91292A113         $6.00

“M3x0.5″ x 100 QTY 1 Stainless Steel Nuts       91828A211         $4.73

Ball-End Screwdriver, 2.5 mm Hex, 5-1/8”      5497A53           $3.01

Once you’re on their website, copy and paste the part number into the “Find” box at the top of the page.  You’re ordering a box of 100 3x10mm cap screws and a box of 100 matching nuts.  If you have a set of metric Allen wrenches (hex) you wouldn’t need the screwdriver but I found the Ball-End screwdrivers more useful than hex wrenches for assembly.

Now you’re ready to start printing.  The files you will need are the Track_Roundhouse_turn_table.stl , Track_Roundhouse_Rotator_Bumper.stl , and Track_Curve_9_18_deg.stl .  In the “Files” tab click on the appropriate download link to save these STL files on your machine.

I slice STL files in Slic3r®.  Generally I use a 0.25mm layer height and put about 1mm of plastic on the outside surfaces as a shell.  Since my printer has a 0.5mm nozzle I use 2 vertical shells and 4 horizontal top and bottom shells.  I set a honeycomb fill pattern with a 25% fill density.  I don’t use support when printing the turntable or the rotator.  However, the curved sections of track will benefit by having the “Support turned ON” for printing the track pattern on the bottom against the platter.  I print almost exclusively using ABS.  If you use PLA send a comment about how your turntable came out.

The turntable base has 8 track ports (one IN and seven OUT).

There is a nut trap printed on the bottom for one of the 3mm nuts you just ordered.  Clean out any extra plastic filaments from the nut trap.  Insert a screw through the center hole and start a nut on the bottom.  Then using the ball-end screwdriver or (an Allen wrench) pull the nut up snugly up into the nut trap (make sure the corners line up) and back out the screw leaving the nut in place.  Save the screw for the rotor section.

The “rotor-bumper” file contains the center rotor for the turntable plus three “End Bumpers” for ends of track that may be used on sidings or for parking rolling stock around the turntable.

 At your discretion, you could print these parts in a different color to make the rotor stand out.  When finished printing, put a 3x10mm screw down through the center of the rotor and the turntable base.   Tighten enough so friction will hold the rotor in place when turned.  Turn the assembly over and put a drop of super glue (cyanoacrylate adhesive) on the nut and threads so the screw can’t back out during use.  It may be useful to turn the screw in and out with the screwdriver to work the adhesive up into the threads (before it sets).  Leave the rotor snug.

There are rail track “ports” every 36 degrees around the turntable.  This was a trade-off in the design.

The rotor needed to be long enough to fit the engines but the entire base needed to be small enough to fit on an 8 inch (200mm) printing platter.  This causes a problem in aligning track since the turns in the standard Thomas® track comes in 45 degree increments.  The curved track sections account for 9 and 18 degree arcs so that any port may be aligned with the track layout.

After printing, check all the track connectors and trim them to fit your track. 

Roundhouse Bays

Any number (up to seven), of the roundhouse bays may be incorporated with the turntable in any configuration.  Before you start, make sure you have sufficient filament.  My printing software indicated that I would need about 33 meters of 3mm plastic filament for the print.  That’s about a quarter of a 2 kilogram spool.  If you want all your bays printed with the same color purchase a new spool of plastic before you start.

This will be a long print and your printer will need an 8 inch (200mm) heated bed if you’re using ABS.

Download the Track_Roundhouse_Bay.stl file or the version with heat shields.  The heat shields help (but only help) to prevent stress cracks if you’re printing with ABS.

Slice the .STL file the same as for the turn-table.   I use the “Skirt” option when printing.  This gets plastic flowing to avoid a skip as the print starts.  If you’re slicing software allows: set 2 loops, 2mm from the object, with a skirt height of 2 layers (the dual layers makes for an easier removal after printing).

This is a large/tall print and thermal stresses can cause cracking between layers.  After a molten layer of plastic is deposited, it cools.  Once the plastic solidifies and continues to cool to room temperature it tries to contract.  This produces stresses between layers.  At the corners and ends of long plastic runs the forces can be sufficient to pull the layers apart.  A heated bed reduces the temperature gradient in the plastic close to the bed but doesn’t help as the height increases.  The stresses in PLA are smaller since the melting point is closer to room temperature.   PLA isn’t affected as much as ABS.

You may wonder about the presence of all the “windows” in the Roundhouse Bay.  The first reason is simply practical.  When engines or rolling stock are placed in a bay, they sometimes get derailed.  All the windows are convenient for little engineer fingers to maneuver the piece so it may be withdrawn.  The second reason is for thermal stress reduction.  The shorter runs of plastic don’t build up as much stress as longer runs.

When your piece completes printing you may be dismayed at some hairline and larger cracks in the corners above the height of the windows.  For small cracks (in ABS prints) dip a toothpick in acetone and touch it to the crack.  You may have to repeat this step a number of times but eventually a drop of acetone will be drawn into the crack and will seal it against further propagation.

For the larger cracks take the “skirt” from the printing and cut lengths that fill the cracks.  Again take the toothpick and place a drop of acetone on the patch until it fills in.  Note: this acetone trick only works for ABS.

Station and Ticket Office

A railroad would not be complete without a train station and ticket office.  The station base was merged with a section of track to become an integral part of the line.  Plus the base had to be elevated to align with the freight and passenger cars.  The station base is printed as a series of arches to minimize plastic.  Then using a different color the walls of the ticket office were printed and finally the roof was printed with a third color.

 Download the Track_Station_Ticket_Platform.stl, the Track_Station_Ticket_Office.stl and the Track_Station_Ticket_Office_Roof.stl. Note: when printing roof structures you may need to increase the number of vertical (sidewall) shells in your slicer program.  The shallow roof pitch may require multiple “loops” around the roof perimeter for each layer to avoid leaving gaps where rain could penetrate.

Trim off the adhesion pads with a knife after printing the “platform”.  The “platform” has alignment bumps for the “Office Walls” and the walls have alignment bumps to align the roof.  Trim out any “elephant’s foot” plastic in the cups in the walls and roof. Assemble using a bead of super glue (cyanoacrylate adhesive) on the bottom and top of the walls followed by a weight until the glue sets.

Train Wash Station

Your train can become dirty from normal operations.  So a wash station was added to the layout.  You will need to download the Track_Car_Train_Wash.stl file and the Track_Car_Train_Wash_Roof.stl file or the Track_Car_Train_Wash_Roundhouse_Roof.stl file.  In explanation for the two roof files, decide where this wash station will be located in the layout.  If connected to the turntable next to a roundhouse bay you need the “roundhouse_roof” version for clearance.  If the wash station is to be located away from other structures the regular roof can be printed.  Assembly is the same as for the ticket office except when using the “roundhouse_roof”. In this case the roof can only be assembled in one orientation to clear the roundhouse bays.

Loading Platform

The station needed a platform for passenger and freight loading and unloading.  A modular platform was created by extending the station base design and integrating a section of track.  Platforms can be stand alone, ganged together, or connected to either side of a station.  Download the Track_Station_Platform.stl and after printing, trim off the adhesion pads.

 Tunnels

No respectable rail road could exist without tunnels.  This short tunnel represents about the third design generation.  Each version getting wider and higher as new cars were added.  Even now, as seen in the photo, the automobile carrier has restricted clearance if automobiles are placed on the top rack.

 This piece needs the Track_Tunnel.stl file downloaded and printed.  After printing the adhesion pads need to be trimmed off.

Long Tunnels

Sometimes you need long tunnels.  The first tunnel design was adapted to extend to the end of the track section.  That way multiple tunnels could be connected in series for an arbitrarily long cut.  Notice that there are windows in the sides of the tunnels.  This is for the same reason that there are windows in the roundhouse bays.  Windows provide thermal stress relief while printing plus they allow finger entry to maneuver stuck vehicles.  The greatest benefit for tunnel windows is so young engineers can watch trains as they pass through the tunnel.

You’ll need to download the Track_Tunnel_Long.stl and again trim off the adhesion pads after printing.

I told the grandson that this was the mountain station on the railroad.  I was informed that “there are no hills”.  Proud of my quick thinking, I replied that “the tunnels go through the mountains so it’s flat”.   I don’t think he believed me.  However, this is an idea for future expansion.  The problem is that the 3DPrintedRailRoad car connectors only swing sideways.  They don’t handle elevation changes well.

President’s House

The railroad needed a residence for the president of the railroad.  A cramped building like the ticket office just wouldn’t fit the style for a railroad’s president.  The president would need a grand residence for showing off his prestige.  When the grandson first saw the president’s house he picked it up, looked inside, and said “where’s the rooms?”   Recently I asked him if he thought the president of the railroad lived in that building.  He thought it looked more like a museum.

Download the Track_Station_House.stl and the Track_Station_House_Roof.stl files.  The roof can be printed in a different color if desired.  There are alignment bumps for assembly so the procedure is the same as for the ticket office.

Trees for the Railroad

Any self-respecting railroad needs trees in the landscape. 

Here are designs for three kinds of trees.  There’s a regular tree Rail_cars_Tree.stl, a tall tree Rail_cars_Tall_Tree.stl, and a pine tree Rail_Cars_Pine_Tree.stl.

Tree

Tall Tree 

Pine Tree

When printing you may have to increase the number of (side, top and bottom) shells if the print doesn’t cover the fill at the top of the tree.

While the first tree is printing (I used green ABS plastic but you could have alien trees with almost any color).  Run down to the local Lowes Hardware or Home Depot (big box hardware store) and purchase a 3/16″ (4.7mm) poplar dowel for the trunks (unless you just assembled the railroad crossing signs).

When the first tree has finished printing use a 13/64″ (5.2mm) drill to clean out the trunk holes in the base and the bottom of the tree. A 3/16″ (4.7mm) drill will leave a friction fit.  Remember not to drill all the way through the top.

Cut the trunk material (the poplar dowel) to the height you want for your tree (a 2″ (50mm) piece of dowel is good for a start).  I use a jackknife to score the dowel by rolling it across a scrap piece of pine board.  Hold the knife at right angles to the dowel when you press down and roll or it’ll cut a spiral.  After a couple turns the dowel can be snapped at the score mark.

Gorilla glue or super glue works well for assembling trees.  Just put some glue on each end of the dowel for the regular and tall tree and push on the top and base.  For the pine tree slide the two branches onto the dowel, glue on the top, add glue to the dowel below the top and slide the branches up.

Railroad Crossing Signs

Railroad Crossing signs are needed where automobile traffic cross the track.

This looks like a bumpy crossing since I haven’t designed the track component for an official rail crossing.  The rail crossing signs were created as a replacement to one that was broken in the grandson’s setup.

This is a quick printing project with two STL files that will make a pair of rail crossing signs.  I printed the crossing sign base in green ABS and the cross bars in red ABS.  If you want the crossbar and the base to be the same color then both files can be added to the Slic3r® platter when generating the gcode.

The files you’ll need to download are for the base Rail_Cars_Crossing_Base.stl and the cross bar Rail_Cars_Crossing_Crossbar.stl. 

You’ll need a couple of 3/16″ (4.8mm) dowel pieces about 1 and 5/8″ long (41mm) to connect the base and crossbar.  I use poplar dowel from Lowes hardware or Home Depot (big box hardware store).  I once purchased dowels from a hobby supply store that were made in China but didn’t like the way they cut.  They were too pithy (you can’t say that fast).

Depending on your printer you may need to clean out the holes in the base and crossbar.  A 3/16″ (4.8mm) drill will leave a tight friction fit.  A 13/64″ (5.2mm) drill will leave clearance for the dowel.  Gorilla glue or super glue will work well for the final assembly.

Your railroad should now be well accessorized.