Electromagnetic Can Crusher

Project Type: Propulsion and Levitation

Project Information

Project Description:

The task is to design and build a device that crushes aluminum soda cans using intense pulsed magnetic fields.  Electrical energy is stored in a capacitor bank and an ignitron is used to transfer the energy to a coil surrounding the unsuspecting can.  The coil generates an intense magnetic field that is temporarily trapped between the coil and the outer surface of the can due to eddy currents induced in the can’s surface.  The trapped field produces a symmetric radial force against the can and coil.  Since the coil is very sturdy and can’t move, the can does and collapses into an hour-glass shape.  The circuit must be designed to have a low stray inductance, the correct discharge frequency, and store just enough energy to crush the can, rather than rip it apart.

Level of Difficulty: Medium

Keywords/Technologies:

pulse power, ignitron, stray inductance, eddy current, Lenz’s Law, skin effect, equivalent series resistance, theta pinch, hoop stress, electromagnetic forming, field shaper, magnetic diffusion

References:

“Can Crusher – Magnetic Implosion,”  Harvard Natural Sciences Lecture Demonstrations, A.W. DeSilva, “Magnetically Imploded Soft Drink Can,” Am J Phys 62(1), 41-45 (1994) https://sciencedemonstrations.fas.harvard.edu/presentations/can-crusher-magnetic-implosion

Ralph Schäfer, Pablo Pasquale and Stephan Kallee, “The Electromagnetic Pulse Technology (EMPT): Forming, Welding, Crimping and Cutting,” PSTproducts GmbH, Alzenau, Germany http://www.pstproducts.com/empt%20forming%20welding%20crimping%20and%20cutting.pdf

Team Roles

Electrical Engineer (2) – Electrical Engineers on the project are responsible for the high-voltage power supply, capacitor bank, and ignitron switching element.  This energy delivery system must withstand the magnetic pressure and have a low stray inductance to maximize crushing efficiency.  The GL7171 ignitron is a triggered device that connects the capacitor bank to the coil.  Electrical Engineers are responsible for the design and construction of a reliable, high-energy trigger system.

Mechanical Engineer (2) – Mechanical Engineers on the project are responsible for the coil and can assembly that will be designed to withstand the pulsed magnetic pressure that deforms the can.  Additionally, the number turns and the insulation gap between the coil and can are designed to produce the correct crushing frequency.  Coils for crushing and can launching will be developed.

Physicist (2) – The Physicists on the project are responsible for calculating the magnetic diffusion properties of the soda can, which determines the system’s discharge frequency.  The use of a field shaper will also be studied.  The Physicists will work closely with the EEs and MEs to design a system that can be shown to be efficient and effective, prior to construction.

Computer Scientist (2) – Computer Scientists on the project are responsible for the diagnostic, control, and safety systems on the experiment.  The machine’s diagnostics include voltage and current measurements of both the charge and discharge cycles.  Control and safety systems include automated interlocks that govern the correct procedure for inserting the can, charging the machine, crushing the can, making the machine safe, and finally removing the crushed can.  Computer Scientists will work closely with the Designers to implement the diagnostic, control, and safety systems into a public display.

Designer (2) – Designers on the project are responsible for making the can-crushing machine safe and easy to use for a public display.  The idea is for people to bring their own cans, operate the machine, and receive a mangled can as a souvenir.  There must be no way for anyone to be injured while crushing a can or for anyone to break the machine through normal operation or clever abuse.

Journalist (1) – The Journalist documents the project’s progress on the website, communicates with the local media, and is responsible for a final report to the principal sponsors and Power Mountain Engineering.  The Journalist also works closely with the Multimedia Artist to provide video and graphic art displays for demonstrations that explain the project to the public.  The whole project is your project.

Multimedia Artist (1) – In addition to the normal team responsibilities of maintaining the project’s progress on the website and presence on social media, the Multimedia Artist will also design, organize, and host a public demonstration of the can-crusher exhibit.

Business Manager (1) – The Business Manager is responsible for reporting the project’s progress against a predetermined schedule, determines critical path items to completion, and tracks project spending to assure that costs remain within a fixed budget.  The Manager works with all team members to identify problems early and resolve them quickly.  The whole project is your project.

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