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Revision as of 10:30, 22 October 2019
Contents
Supervisors
Honours students
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.
Abstract
Based on the Huber Effect, the ball bearing motor can be made to continuously rotate in either direction when supplied with either a DC or AC voltage. This phenomenon was first observed in 1959 and has since motivated a number of theories to explain the underlying principles behind the motor's operation. This projects aims to test the validity of some of these theories by taking a modular approach to testing the ball bearing motor. An attempt to evaluate the electromagnetic behaviour is made with the use of the a simulation software called ANSYS Maxwell and yhe relationship between angular velocity and motor torque are also obtained by measuring a physical motor with the use of a load cell and tachometer. The completion of this project hopes to assist future research into the application of the ball bearing motor in micro electrical-mechanical systems whilst leading further research into the Huber Effect in the right direction.
Deliverables and Tasks
Semester 1
- Start Project Work (Week 1)
- Proposal seminar (Week 6)
- Thesis draft (Week 12) - only one report needed in wiki format
Semester 2
- Ball Bearing Motor Mystery YouTube video (Week 3)
- The reactions of metals with Gallium YouTube video (Week 7)
- Final thesis (Week 12) - only one report needed in wiki format
- Final seminar (Week 13)
- Project exhibition 'expo' (Week 13)
- CD or stick containing your whole project directories (Week 13)
Weekly progress and questions
Background
Specific Tasks
- Step 1: Film the construction and operation of the motor.
- Step 2: Use COMSOL to simulate the motor to see if you can investigate what happens in simulation.
- Step 3: Characterize the motor. Using an encoding wheel and a photosensor, plot curves of torque versus angular velocity of the motor.
Method
Previous works have shown that the ball bearing motor exhibited several self destructive behaviours when subjected to high currents. This has historically limited the measurements of the ball bearing motor as heating of the metal components expands and seizes the ball bearing races. One way to minimise these self destructive effects is with the utilisation a liquid metal that submerges solid disks. This metal liquid will act as a slip ring that allow for current to be supplied to a solid disk. Not only will this method limit the heating of the ball bearing races but will allow for the Huber Effect to be investigated when the electricity is not being applied to a rotating component. The liquid metal will also act as a fluid heat sink to minimise degrading of the metal disks.
Liquid Metal
Gallium is chosen for this experiment due to its relatively low melting point (30 degrees Celsius) and its non-toxic behaviour which allows it to be safely handled. It is highly corrosive to other metals, however, it has also been proven to be an effective cooling agent with low viscosity making it very adequate for this project.
Galinstan, an alloy consisting or gallium, indium and tin, was also considered due the similar properties it shares with pure gallium. It was, however, dismissed due to its high cost when compared to gallium.
Solid Disks
A list of materials including; tungsten,copper,aluminium and stainless steel were tested against gallium to see which would be best suited for the manufacturing of the solid disks. Copper and aluminium showed obvious corrosion when placed in liquid gallium for 30 minutes. Whilst copper exhibited clear signs of becoming brittle, the aluminium rod that was tested completely snapped in half. Tungsten and stainless steel on the other hand showed little to no corrosion at all. Ultimately the solid disks were made out of stainless steel due to its relatively low cost and availability
Results
Conclusion
Glossary
References and useful resources
- Method to measure torque
