Table Top Marble Roller Coaster

Introduction

This project is about creating a marble roller coaster powered by a DC electric motor. The design is aimed toward high school seniors, both in terms of difficulty and for cost. The design was influenced by commercial roller coaster toys made for kids but incorporates the hands-on and improvised making style that is intrinsic to Rube Goldberg machines. This project will require power tools and a soldering iron.

The roller coaster has 2 main parts: the lifting mechanism and the track. The lifting mechanism uses a DC electric motor to rotate an Archimedes screw. This the brings the marbles from the bottom to the top of the track. The track part is fairly simple in that it is just PVC tubing bent into some layout. The complexity of the layout comes down to the builder's skills and willingness to overcome the challenges they encounter.

Overview of Design

By using an Archimedes screw that is connected to a DC motor, the marble is able to be moved to the top of the coaster. The DC motor is powered by 6V battery power supply. When the marble gets to the top of the coaster, it is dropped on the track. The increase in potential energy transfers to kinetic energy, allowing the marble to roll down the track. The coaster will be mounted to a circular piece of plywood that is 18” in diameter and ½” thick in order to provide stability for the project.

Initial 3D Model

Materials

• 2’x2’ (or more) of ½” plywood
• Wood glue
• Instant adhesive
• 3/8" diameter marbles or smaller
• 24" Rigid plastic rod
• Plastic encased steel wire
• 5V DC motor
• Battery pack
• D Cell Batteries
• ON/OFF switch (Single pole, single throw)
• Thin nails OR Pin
• 22 or 24 AWG Wires
• 5/8" ID x 5’ Flexible plastic tubing

Estimated Cost: $70.89

Tools

• Drill
• Saw
• Tape measure
• Measuring square
• Side cutter OR Flush cutter
• Soldering iron
• Wire strippers

1. Take the rigid plastic tube and securely fix one end. This can be done using a drill (which is advised) or by clamping it down. The other side of the tube should be supported.
2. Take the plastic encased steel wire and wrap it around the rigid tube, keeping a pitch of 1".
3. Tape down the ends of the wire and apply instant adhesive to keep it in place. Applying heat may also help, but too much heat will melt the plastic on the wire and the rigid tube!
4. Once the glue has set and the wire is properly in place, cut the tube down to the proper length, using a wire cutter for the wire and a hacksaw for the tube.
5. If the wire comes loose again resecure the loose end and reapply the glue.
6. Put the shaft of the motor housing into the hole of the rod. Make sure to keep the shaft directly in the center of the diameter of the rod to ensure that the Archimedes screw rotates uniformly. Take a 1/16 drill bit and drill a hole through both the rod and the shaft. Place a small pin in the newly created hole to hold the Archimedes screw and the motor shaft together.
7. 

1. Cut out an 18” diameter circle from the plywood. This will be the base plate. (Make the cut as close to the edge of the plywood as possible as the remaining wood will be used later.)
2. 
3. Cut out a 2”x2” piece of wood. This piece will be used to hold the motor that is attached to the Archimedes screw in place. Glue this piece to the baseplate 1 1/2 inches from the edge.
4. 
5. Cut out a 2"x12" piece of wood. Sand the top of this piece so that there is a U shaped groove in order for the end of the Archimedes screw to sit in. Cut one hole for the 2"x12" piece into the base plate. Make sure to distance this hole apart from the 2"x12" piece far enough to create a 45 degree angle when the screw is in place. Once the desired angle of the Archimedes screw is achieved, and insert the support piece into the hole.
6. 
7. 
8. Glue the motor housing to the 2"x2" piece of wood and place the end of the screw into the U shaped groove of the 2"x12" piece.
9. 
10. Cut out a 2”x10” piece of wood. Glue this piece to the side of the Archimedes screw’s support pieces, leaving less than ¼” between the side piece and the Archimedes screw. Make sure this piece of wood has a piece on the side coming out of it that can be used to mount it to the base plate so that it runs parallel to the Archimedes screw. Ensure that there is a 1" cutout that is parallel with the screw that allows for the marble to fall off of the wire.
11. 

Track sections and support pieces instructions

1. Cut out track supports from the remaining wood. There should be at least four track supports in total. Each piece should be a different height ranging from 10" to 4". All supports must have a U shaped groove in the top in order for the track to fit. To do this, sand down a U-part into the support piece at an angle until the track section can be glued on at an angle of 5 degrees.
2. 
3. 
4. 
5. Use Wood glue to glue the support pieces in place. The farther the distance between the pieces, the greater the difference in height for the support pieces.
6. 
7. Take the plastic tubing and cut it in half lengthwise. Cut one of these two pieces down to the desired length so that the tube can be placed on the first three track supports in such a way that there are no creases that will hinder the marbles movement.
8. 
9. 
10. If the track piece needs to make any turns that are too sharp for it to properly transfer the marble to the bottom of the Archimedes screw, cut out a smaller piece of track section and use it to intercept the marble and turn it sharply.
11. 
12. Glue the track sections onto the track support pieces.
13. 
14. Test to see if the marble properly rolls from the top of the Archimedes screw to the bottom. If it does not, remove a track support as needed, adjust and glue it in the new position, repeat this until the marbles can consistently cycle through the system.
15. 

Electrical Overview

The elevator mechanism will require the use of a DC motor to power the Archimedes screw. This will necessitate the use of an external battery pack, as well as a basic SPST switch. This will allow the motor to run continuously, without the need for any input by the user.

The first step is connecting the positive lead of the battery pack to one of the ends of the DC motor. Once that is complete, connect the on/off switch in between the positive end of the battery pack and the other end of the motor. This circuit will act independently of the lighting circuit. Toggling the switch at the positive end of the battery pack will turn the elevator mechanism on/off. The motor can now be attached to the housing with the rest of the elevator mechanism. The motor counter-clockwise in order for the elevator to function; to reverse the spinning direction, switch the leads of the wires from the motor to the battery pack.

Once the motor is connected to the elevator, the battery pack can be attached to the baseplate with instant adhesive.

Now all that is needed is to load the marbles onto the track and turn the motor on. Enjoy!!!

The device can serve as a platform for expansions to add visual and auditory feedback to the user as the marbles descend down the track. Once such addition could be the inclusion of LED lights that change colors whenever the marble hits a switch on the track. This will require:

• An LED strip (WS2812B)
• An Arduino Microcontroller (ATMega2560)
• Pressure-Activated Microswitch (SPST, Normally Open)
• Spare MTE cables
• Computer with Arduino IDE

Start by connecting the LED strip cables to the ATMega2560 microcontroller. The MTE cables can be plugged into either end of the strip.The red cable on the LED strip will be connected to the 5V output on the microcontroller, while the white cable will need to be connected to ground. Keep in mind that the microcontroller has an output limit of 40mA, which translates to about 14 individual LEDs on the strip. If more LEDs are desired, then the VCC and GND cables on the strip can be connected to the battery pack instead, by placing them in parallel with the motor. The green cable on the LED strip will need to be connected to a digital PWM output on the microcontroller. Look for pin hole 5 on the digital PWM bus. This is the digital output pin used to control the color of the LEDs.

Once the strip is connected, the microswitch will need to be connected as well. Like the microswitch, the outer two pins on the microswitch are used for VCC and GND. Solder MTE wires to the outer pins and connect them to separate 5V and GND outputs on the microcontroller. The middle pin will need o be connected to an output on the analog bus.

After everything has been connected, the code attached can be opened in the Arduino IDE. Connect the full LED control assembly a computer with the USB-B cable. From there, open up the file in Arduino IDE and upload the code to the microcontroller. Keep in mind that this program relies on the "FastLED" library, which will need to be imported to the project. The microswitch can be placed on the track, where the marble will hit it and cause the color change. Afterwards, simply turn the elevator switch on, and watch as the LEDs switch color every time the marble hits the switch!

References:

[1] S. Wongkhead, “Simulation and Analysis of Speed Brushless Direct Current Based on State Space Modeling” - IEEE xplore. Retrieved January 27, 2023, from https://ieeexplore.ieee.org/document/8434469

[2] D. A. Jackson, “US5800240A - marble race toy with elevator and supporting infrastructure,” Google Patents. [Online]. Available: https://patents.google.com/patent/US5800240A/en?q=marble%2Belevator&oq=marble% 2Belevator. [Accessed: 24-Jan-2023]. 

[3] “How to choose the best desk size for your workspace,” Wayfair. [Online]. Available: https://www.wayfair.com/sca/ideas-and-advice/guides/how-to-choose-the-best-desk-size-for-your-workspace-T11398. [Accessed: 17-Feb-2023].

[4] Nick, “Designing a safe backyard roller coaster with Paul Gregg,” Coaster101, 24-Jan-2017. [Online]. Available: https://www.coaster101.com/2016/07/26/designing-safe-backyard-roller-coaster-paul-gregg/. [Accessed: 17-Feb-2023]. 

[5] “Electrical DC Motors - Full-load Currents,” www.engineeringtoolbox.com.

https://www.engineeringtoolbox.com/current-amps-120-240-volt-dc-motors-d_1692.html [accessed Feb. 17, 2023].

[6] “D.C. Motor Torque/Speed Curve Tutorial:::Understanding Motor Characteristics,” Mit.edu,

2019. http://lancet.mit.edu/motors/motors3.html [accessed Feb. 17, 2023].

[7] Target Marbles, 5/8" diameter or 16mm,” www.moonmarble.com. https://www.moonmarble.com/c-77-target-marbles-approx-16mm-or-58.aspx [accessed Feb. 17, 2023].

[8] “A2212 Brushless Motor Pinout, Wiring, Features, Specs & Datasheet,” Components101. Apr. 21, 2018. [Online]. Available: https://components101.com/motors/2212-brushless-motor [Accessed Mar. 2, 2023].

[9] “US5800240A - marble race toy with elevator and supporting infrastructure,” Google Patents. [Online]. Available: https://patents.google.com/patent/US5800240. [Accessed: 03-Mar-2023].

[10] “Learning resources jumbo Archimedes Screw (single) - amazon.com.” [Online]. Available: https://www.amazon.com/Learning-Resources-Jumbo-Archimedes-Single/dp/B06X9CSBT4. [Accessed: 04-Mar-2023]. 

[11] “US9205988B2 - bucket elevator with belt protected by the Bucket Section,” Google Patents. [Online]. Available: https://patents.google.com/patent/US9205988B2/en?q=%28bucket%2Belevator%29&oq=bucket%2Belevator. [Accessed: 03-Mar-2023].

[12] “Amazon.com: 200 pcs beautiful player marbles bulk for marble games,1 ...” [Online]. Available: https://www.amazon.com/Beautiful-Player-Marbles-Multiple-3Whistle/dp/B07S7GQGD8. [Accessed: 02-Mar-2023]. 

[13] “PVC, 3/4 in inside DIA, tubing,” Grainger. [Online]. Available: https://www.grainger.com/product/55YK59?gucid=N%3AN%3APS%3APaid%3AGGL%3ACSM-2295%3A4P7A1P%3A20501231&gclid=Cj0KCQjww4-hBhCtARIsAC9gR3ZETUNikR05a9Nb5ekEMm9KT2qok05WhbL5fub6rrmXB-OhEPWPhCUaAk5XEALw_wcB&gclsrc=aw.ds. [Accessed: 24-Mar-2023].