Design of a Low Velocity Railgun Jason Fodstad Thomas Morris Julie Duryee Vardaan Chawla Final Presentation – MSE 4021 April 26, 2005 Faculty Advisor: Dr. Naresh Thadhani The Capacitor Bank

Outline Project Description Theory Final Design Budget Learning Experience Conclusion Acknowledgements Demonstration

Project Description Design a safe tabletop railgun to be used for performing experiments in a high school classroom Fire lightweight projectiles at low velocity Design laboratory experiments and/or classroom lesson plans Budget : $700 Client: Ms. Anne Marie Johnson, Science Dept. Chair, Chamblee Magnet School

Railgun Theory To determine the force that acts on the armature - Lorentz equation I = Current L = length along which current is flowing B = uniform magnetic field To determine the exit velocity of the projectile, we find: where, V = velocity L' = inductance of rods I = current t = time length of current pulse m = mass of projectile

Final Design Rails Injection System Armature Capacitors Charging System Casing

Final Design - Rails Requirements –High conductivity –Durable –Low coefficient of friction Material Selection: –Silver-Plated Copper 110 Alloy L Shaped to plug directly into capacitor bankL Shaped to plug directly into capacitor bank

Final Design – Injection System Purpose: Give the armature initial velocity to prevent welding Final Design Original Design Old design  Spring Based  Inconsistent Final design  Compressed Air Powered  Remotely activated

Final Design - Armature Requirements –Conductive –Low coefficient of friction –Lightweight Aluminum, GraphiteMaterials Selection: Aluminum, Graphite Aluminum high conductivity low wear resistance lower melting point than rails, armature melts instead of rails causes frictional wearGraphite low conductivity high wear resistance higher melting point than rails, rails melt instead of armature self lubricating, minimal frictional wear

Final Design - Capacitor Requirements –High Capacitance / Energy –Fast Discharge –Maximize current generated Panasonic Computer grade electrolytic, 450VSelection: Panasonic Computer grade electrolytic, 450V –Fast discharge –Cost effective –Mechanically sound

Final Design – Charging System Uses building power (110V AC) Fuses and resistors for safety Solenoid Capacitor Bank Rectifier Transformer Fuse Railgun

Final Design – Casing and Spacer Casing: Plexiglas –Material Selection: Plexiglas clear so students can see all parts Spacer Material Oil Filled Nylon 6 –Material Selection: Oil Filled Nylon 6 Self lubricating Resistance to wear Cheaper than Teflon

Budget Current Spending: –Copper Bars: $28 –Nylon: $34 –Solenoid valve: $54 –Capacitors: $200 –Misc. Parts for Charging system: $60 –Misc. Parts for Injection System: $10 –Acrylic: $0 (Donated) –Transformer: $0 (Donated) –Bolts: $0 (Donated) –Compressor: $30 –Voltmeter: $30 –Misc. mechanical parts: $30 –Replacement parts: $100 –Advisor Consultation Fees: $124 Budget $700 Total Spent $700 Remaining $0

Learning Experience Design is a dynamic process and must be flexible to allow for changes Buy the ideal materials based on function as opposed to cheap alternatives Machining takes a lot longer and is a lot more complicated than originally assumedTeamwork!

Conclusion Our objective was to build a low-velocity railgun for high school demonstration use Unique challenge because most research is concentrated in the area of high velocity railguns Still within Budget

Demonstration

Acknowledgements Dr. Naresh Thadhani and The High Strain Rate Lab Matt McGill