Design and mathematical analysis of an adjustable MDF catapult for variable range targeting.
This repository documents the design, mathematical analysis, and manufacture of an adjustable catapult built by Group 11 at Birmingham City University.
The objective was to design and build a catapult to launch squash balls at targets between 1–5 metres.
- Materials: A single 600 x 600 x 9 mm piece of MDF.
- Fasteners: Maximum of 30 individual semi-permanent fasteners (nuts, bolts, and washers).
- Adjustability: The design must be "settable" for variable distances.
The final physical prototype, hand-cut from 9mm MDF.
We researched three traditional catapult styles: the Ballista, Trebuchet, and Mangonel.
- Morphological Analysis: We compared different sub-functions, such as power sources (elastic stretching vs. twisting) and projectile holders (slings vs. cups).
Morphological analysis used to address feasability concerns.
- Pugh Matrix: We evaluated three concepts against criteria like ease of manufacture and simplicity. Concept 3 was selected with a grand total of 78 points.
Decision-making matrix used to objectively select the final design.
We conducted a series of experiments to find the spring constant (
Ballistic Range Calibration: Using ballistic motion equations and adjusting for drag, we developed a precise setting guide for the catapult:
Settings required to hit targets between 1m and 5m.
The catapult was modeled using CATIA, creating an assembly of five distinct parts: the base, two sides, a post, and the swing arm.
Full assembly render showcasing the adjustable release points.
- Base Dimensions: 350mm length.
- Swing Arm: 300mm length with a 40mm pivot width.
| Side View | Front View |
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Due to the laser cutter being unavailable, we generated a DXF template and cut the pieces out by hand. While this introduced potential human error in accuracy, it proved our design remained within material constraints.
- Lateral Motion: We identified that the arm would throw off-center due to lateral movement. We overcame this by replacing nuts with MDF spacers to stabilize the arm.
- Consistency: By repeating tests 3 times per distance to find a mean average, we achieved consistent target hits.
Full project available at Catapult-project.pptx