The ball bearing motor mystery 2019

Supervisors

• Prof Derek Abbott
• Dr Andrew Allison

Honours students

Jayden Hayward Richard Saing

Project guidelines

• Project Handbook

General project description

The ball bearing motor is a mystery because to this day as no engineer knows how it works! No one understands the physical principle at all. Your job is to do some experiments to investigate this motor and why it is that it rotates. Understanding the principle is important. It may not be useful for large motors, but it may be interesting for micromotors and micropumps that have numerous applications.

Specific tasks

• Step 1: Get the workshop to construct a ball bearing motor. It is simply a metal shaft with two ball bearing races either end. If you connect a power supply (eg. a car battery) across the two races it spins at over 1000 rpm and it doesn't matter if it is AC or DC! The objective is to film it working using your smart phone and create an entertaining YouTube video demonstrating it working. This video will be something visual for your presentations and is very important.

• Step 2: Use COMSOL to simulate the motor to see if you can investigate what happens in simulation. The trick here will be to simulate simpler versions of the motor that we will show you. The full ball bearing motor is too complex to simulate first off, so we must simplify.

• Step 3: Characterize the motor. Using an encoding wheel and a photosensor, plot curves of torque versus angular velocity of the motor. For reasons we will go into later, the ball bearing motor itself is not easy to characterize. So the idea is to capture the principle in another way that is simpler. You can get a same effect by getting a metal disc to rotate in liquid metal. We'll show you this idea in detail when you get started. Because mercury is poisonous we will not use that. There are safe non-toxic metals such as gallium and various alloys of gallium with low melting points. Do some research and make a table of these liquid metals, showing their their properties and their cost. We will then select a metal that fits within your project budget. The quantity we can get at reasonable price will also determine the size of your liquid contact motor.

Deliverables

Semester 1

• Start Project Work (Week 1)
• Proposal seminar (Week 6)
  • File:142 Proposal Seminar2019.pdf
• Thesis draft (Week 12) - only one report needed in wiki format
  • File:142 Progress Report2019.pdf

Semester 2

• Final thesis (Week 12) - only one report needed in wiki format
  • Final ball bearing motor thesis 2019
• Final seminar (Week 13)
  • File:142 Final Seminar 2019.pdf
• Project exhibition 'expo' (Week 13)
• CD or stick containing your whole project directories (Week 13)
• YouTube video (Week 13) - add the URL to this wiki
  • https://www.youtube.com/watch?v=P-OtHLq0KVU

Weekly progress and questions

This is where you record your progress and ask questions. Make sure you update this every week.

• The mystery of the ball bearing motor 2019 weekly progress

Approach and methodology

Use a dual approach of performing the actual experiment with an encoding wheel and using COMSOL to simulate the effect. You may also consider simulating "Faraday's needle," which is a similar effect. Use COMSOL as a tool to plot fields and find out what it is going on.

Possible extension

You need to figure out how to account for any viscous drag caused by the liquid metal. Perhaps you can perform your experiment with different surface areas of the disc dipping into the liquid metal. You could try just using water instead of metal. The problem with water is the discs will rapidly oxidize. But it should not be expensive to get discs with thin gold plating to prevent this.

Expectations

If you solve the ball bearing motor mystery that is great. However, as it is unsolved for over 50 years we won't mark you down for not solving it. What we expect to see is a structured logical approach to both your lab and COMSOL experiments. If you can definitely eliminate any effects this would be great.

• It is important to regularly see your main supervisors. Don't let more than 2 week go by without them seeing your face briefly.

• You should be making at least one formal progress meeting with supervisors per month. It does not strictly have to be exactly a month, but roughly each month you should be in a position to show some progress and have some problems and difficulties to discuss. On the other hand the meetings can be very frequent in periods when you have a lot of activity and progress to show.

• The onus is on you to drive the meetings, make the appointments, and set them up.

Relationship to possible career path

The project impacts on the areas of micromotors, micropumps, microelectromechanical machines (MEMS), and electromagnetics.

See also

• Final Report/Thesis 2018
• Final Report/Thesis 2019

References and useful resources

If you find any useful external links and resources, list them here:

• ....

Back

• Back to MyUni
• Back to Derek Abbott's homepage
• Back to EEE Department page
• Back to the University of Adelaide homepage