Bullet Impact Test Apparatus
Team: Sam Ruffing, Connor Pugmire, Sam Lewis, and Jax Kraync
Sponsor: Delta-V Energetics
Project Background
Problem Description: With a budget of $5,000, design a system that electromechanically fires three .50 caliber rifles sequentially and activates a high-speed camera to record the impact. A custom firing mechanism must be developed for the existing breach-loaded rifles. The entire system must be designed for use outdoors and have safety features preventing inadvertent firing.
Device In Action
Design Description
The device consists of three rifles that are rigidly mounted to a concrete block. Each rifle has a solenoid mounted behind the breach and firing pin. A remote laptop communicates with an Arduino Uno that controls the electronics and drives the solenoid rods into the firing pin at a user-determined delay. A 24V LiFePO4 battery supplies power to the solenoids. The Arduino Uno also triggers a high-speed camera to record the bullet impact. The solenoid mounts hinge upward to allow access to the breach for reloading.
Performance Overview
| Requirements and Constraints | Target | Threshold | Predicted Performance | Actual Performance |
|---|---|---|---|---|
| All Three Rifles Fire In Time | 100% | 95% | >99% | 100% (4 Tests*) |
| Delay Within 33 ms | Controllable delay | 33ms Controllable Delay | Controllable Delay | Controllable Delay |
| Remote Firing | 100' from rifles | 50' from rifles | >100' | 50'+** |
| Weatherproof | Wet Conditions <32°F | Dry Conditions >32°F | Water/Dust Proof <32°F | Water/Dust Proof <32°F |
| Durability | >500 Uses | >300 Uses | >500 Uses | 5 Uses |
| Consistent Aiming | 1" Grouping | 3" Grouping | ~0.2" Grouping | ~2" Grouping |
*One test failed from user error
**A longer ethernet cable would result in improved distance
Predicted performance was determined using initial designs and physics analysis. Actual performance was determined during final testing using the high-speed camera to verify results. Five firing tests were completed using all three rifles and the final device iteration.
Concrete Mount
The gun post is mounted to the concrete block by torquing down a steel tube bracket with an arc cut out for the post. The bracket is attached to threaded rod embedded into the concrete using epoxy.
Solenoid Mount
The solenoid mount is mounted to the .50 caliber rifle using four ¼" bolts. The mounting plates are bent from 304 stainless steel. 3D printed PETG+ spacers locate the mount to the existing rifle mounting holes. Nylon washers are used to create a friction hinge to move the solenoids out of the way. A knob is threaded onto the solenoid rod for proper alignment to the machined firing pins.
Electronics
The electrical control system is housed in a water and dustproof case with weatherproof connectors. A laptop is used to communicate with the Arduino Uno via ethernet, providing timing control of the camera trigger and solid-state relay switching. When switched, the relays send power to the solenoids, and the rifles fire. Fuses and flyback modules protect the electrical system.
Software
A Python based GUI communicates with the Arduino Uno over USB. Users input initial delay, interval delay, bullet velocity, and target distance, which are used to calculate the camera timing. Pressing "Run" sends a formatted command to the Arduino, which activates the relays and triggers the camera in sequence. This setup enables consistent, adjustable firing control.
Conclusion
- Design Requirements: Our device meets all design requirements through initial testing. Prior to official use the device will need to undergo additional reliability testing
- Lessons Learned: The team learned a great deal about the engineering design process. Particularly about client communication, feasibility testing, and data collection.
- Future Improvements: To improve the design in the future the rifles can be moved to individual mounts so the recoil of one does not affect another. Additionally, the software and electronics can be modified for other firing methods such as a firing button with a keyed switch safety.