An attempt at a 3D printed O Scale Corrugated Grain Silo

Alternate title: What can be done with a 189.99 USD (MSRP) 3D Printer?

Thought I might share this experiment using a 3D printer with a 100 micron resolution and a print volume of a 4.7 inch cube.

Originally I was going to use my plans to cut styrene sheets (corrugated and smooth) and create the 15 foot diameter by 54 foot tall grain silo in O scale.

However, after prototyping a throttle, I decide to test the capabilities of the 3D printer.

The Experimental Portion

For the experiment a 15 scale foot diameter by 40 scale inch high portion of the grain silo was created in SketchUp Make.

The corrugated siding has ribs 4 inches on center with heights (depths) of 1 inch. The rivets are 1 inch diameter with a head 1/2 inch in height. The H-beams have a 1 foot dimension (it is an experiment and 1 foot H-beams are a little big).

Two 40 scale inch portions will be stacked for the print.

The STL file is exported from SketchUp Make and imported into Ultimaker Cura. The function of the Ultimaker Cura program is to produce gcode that is used to control this 3D printer.

Prior to printing the above, a section of a larger diameter silo was printed at the layer height of 0.13125 mm (the same as the throttle body).

At this resolution the corrugated ribs have definite striations created by the layering of the PLA. These might be covered by painting or possible use of a heat gun to smooth the PLA. 

The print layer height was increased to 0.0875 mm for the next test print.

The corrugated ribs are definitely smoother, however the H-beams have visible lines. Most of the rivets printed, holes in the the rib in the center of the above photo are missing rivets.

Overall not bad for the first test. 

I miscounted the number of supporting columns on the prototype silo, there should have been 10 not 8.

Back to the drawing board to rebuild the model.

Model Corrected

The printers 100 micron resolution  (0.1 mm) should mean 1/2 inch objects are approaching the minimum size for printing. 

For this printing a 0.0875 mm print layer height was used and the print took 8 hours and 7 minutes. 

This section is 40 scale inches in height and has a 30 scale inch hatch. The 1 inch diameter rivets are visible and are close to the correct scale size. The hatch was printed a little smaller  than expected.

DIY - ALOC RS-3 Throttle and Locomotive Control (3D Printing and MCUs)

The ESP32 is a microcontroller with both Wi-Fi and Bluetooth onboard for communications. This low power device can be used to design a model locomotive control system. (consideration must be given to available space in the model)

Locomotive Control

The onboard MCU (ESP32) will act as a WEB server as well as a Wi-Fi Access Point for both the throttle and the model locomotive.

After the Wi-Fi connection is established to the MCU. The onboard WEB SEVER will transmit the control page to a web browser. 

The initial design for the engine’s control page is shown above. Key features are a throttle control (slider) that can be notched representing the 8 notches and neutral on the prototype. The throttle can also be reconfigured to be continuous value representing a speed control on traditional model throttles. A slider is also used to control reverse and forward settings.

Lights (FRONT, REAR, DITCH) will be controlled by buttons as shown in the middle of the screen. The BRAKE button will result in speed reduction but will not alter throttle setting. The STOP button will set the throttle to zero and lock the throttle controls.

Feedback

Every control shown on the above engine control page can be set with code residing on that page independent of the WEB server (engine). This makes this page entertaining but not informative.

The objective is to send values to the engine’s MCU, have the MCU control the engine based on those values and then confirm that the engine’s state has changed.

Part one of this feedback loop is accomplished by pressing the control and having code on the page transmit the new value to the engine’s MCU.

Part two is accomplished by the engine’s MCU transmitting the same setting back to the engine control page and having code on that page place the value from the engine’s MCU into the appropriate control. (circled in red on the above photo)

For the throttle notch setting, the feedback loads the current value that the engine’s MCU has sent.The buttons that control the lights will change color from blue as shown to yellow to indicate that the engine has received the “Light ON” command. Additionally, that STATUS area will be updated by values sent from the engine.

The above photos shows the result of pressing the “Front LIght” button. The engine control page sent the command via Wi-Fi to the ESP32 MCU, the MCU activated the LED representing the light and transmitted back the value that changed the button color to yellow

The above photos show the web page generated on an older iPhone by the locomotive's MCU after connecting to the Wi-Fi Access Point 

Throttle

For the throttle an ESP32 will emulate the ALCO RS-3 braking and speed control. The MCU will be programmed with the ability to simulate the release, running, holding, lap, service and emergency functions of braking system as will as the idle through notch 8 of the throttle and the mechanical interlocks between the controls. 

Using a personal 3D printer to build the throttle components allows for more creative deigns.