N scale Model Train Freight Car Bulk Carrier Flat Car Four lengths: 40' ~ 45' ~ 60' ~ 70' w/Wire Spool & Container Magnetic Loads for Micro-Trains Couplers

2nd edit added some pole loads as well in both 40 & 60 lengths, as well as four different pipe loads from the new Log / Pipe Car. All with two magnets each.
edit Just include a 60' and 70' version to the series, also made the updated versions easier to print, removing the attempt at simulating more of a wood surface, marked as 3B (length) base bulk flatcar. The 70' has 5 magnet spaces, but you can just use three depending on what loads you want to carry.

I saw a bulk carrier flat car and knew I needed one! But how to make it work? Multiple colors and a hidden set of magnets! There are 6x1mm round magnets buried in the car and the loads. So the cars can be empty, loaded with Cargo Containers or Coil Rolls or with empty Coil Carrying Bases. Or a mix of them. The 40' car is my standard sized car and fits two coils or two of my standard 20" containers or one 40' container. I also wanted a three coil car so made another 45' version with three coils, or a 45' Cargo Container.
You don't need to use different colors, but on my railroad I like to... The pause command for adding the magnets allows the printer head to move to the side and gives space to add the magnets. Here's a short video on how to slice and print the color changes and magnet pauses. https://youtu.be/maQcGIF4u0A

Make sure you use the same orientation on the magnets or the car will repel the load! I always use a finished piece to hold the magnets for the new prints. Use a Load for Loads and a Car for Cars! Once you have made your first piece, use that as your guide. If you want to share with a friend make sure your magnets are the same way! <

I got the magnets here: https://nl.aliexpress.com/w/wholesale-6x1mm-round-magnets.html?spm=a2g0o.detail.search.0

I use Micro-Trains Medium Shank Couplers for the wheel sets using the push pins included with the couplers. There is a smaller and larger pin, once of which has always fit so far. Here is a link to the version I use - there are 10 pairs per box
for 10 cars total. https://www.micro-trains.com/index.php?route=product/product&path=63_113&product_id=421 (they used to be about 1/2 the cost when I started this journey during Covid - damn inflation! ) Here is a small video on how to install the couplers. https://youtu.be/iG7ReV6t0

Most slicers have a place to add scripts during and as an ending script. The codes tend to be very similar if not the same, below is the method I use with Simplify3D slicer.

For Simplify3D slicer Pause Commands can be added to the Scripts tab under Post Processing add:

{REPLACE "\nM117 Layer XXX, Z=" "\nM300 S2000 P80\nG1 X10 Y55 Z25\nM300 S2000 P100\nM0\nM117 Layer XXX, Z="}; pause at layer, move head, play sound

Just replace both of the XXX's with the layer number when the open space for the magnets first gets covered. You can find this layer number by pre-slicing the model first and raising the slicer layer until you see the space for the magnets get bridged i.e. layer 9 the space gets printed over, you would then replace both of the XXX's with a 9 in the script and then re-slice with the script changed and print.

This will move the extruder to the side and beep alerting you to the pause. Add the magnet (Use another load for loads or a car for cars to orientate the magnet the same way) and hit the button on the controller again. This is specifically for the Creality CR10 V3 printer.

Change Color Command:
I used a change color command to make the car's flooring usually a wood or metal color and underside of the car either a brown, black or silver metallic color with the rest of the car yellow or other colors. Here is a short video on how to add color changes using Gcodes. https://youtu.be/5vR1_HEw6Fs

To add the color changes to the S3D slicer I use the following code added on the Scripts tab under Post Processing.

{REPLACE "\nM117 Layer XXX, Z=" "\nM300 S2000 P100\nG91\nG1 X10 Y5 Z20\nM600 S500 P100\nG1 E-6.0 F1200\nG90\nM117 Layer XXX, Z="}; pause at layer, move head, play sound, change filament

Change the XXX in BOTH places to the layer height you wish the new color to start on. Determine this by slicing the boat and picking the height for the color change and then seeing what layer that happens to be. Then change the code to that layer in BOTH places.

The added code starts with the M300 which beeps to alert you of the color change. The G91 command makes the G1 move the extruder head using relative position moving the print head aside. M600 changes the color. Then I added a G1 retract to reduce any oozing. G90 goes back to regular position movements. Make sure you switch BOTH of the TWO (2) XXXs for the correct layer where the new color begins.