Jessica LinusMs. Fitzpatrick

December 5,2012

Engineering Design Project

Catapult

Define The Problem

Students will research, design and construct a catapult that will be able to launch a clay ball of varying sizes (3 grams, 4 grams, 5 grams) a certain distance.

Brainstorming

The catapult must be stable and the projecting arm must limit restriction to enable it to be elastic enough to hurl the clay bar a certain distance. Rubber bands should be efficient enough to launch the projecting arm.

ResearchA catapult is a device used to throw or hurl a projectile a great distance without the aid of explosive devices—particularly various types of ancient and medieval siege engines. Although the catapult has been used since ancient times, it has proven to be one of the most effective mechanisms during warfare.

Identify Criteria and Constraints

Criteria: (1)Students will supply all materials for this project(2) Students will not be allowed to purchase kits(3)This is an individual assignment (4) Students must use the 12-Steps of the Engineering Design Process to complete this assignment(5) Students must document each step in a presentation format using any presentation software (PowerPoint, Prezi, etc)

Constraints:(1) Elasticity(2) Budget(3) Probability of projection(4) Stability

Explore Possibilities

Making A Model

TestingThree-gram clay ball Four-gram clay ball Five gram clay ball

Test 1 time (seconds)

.54 .68 .53

Test 1 Distance (cm) 150 200 130

Test 2 (seconds) .62 .54 .58

Test 2 Distance (cm) 120 100 100

Test 3 Time (seconds)

.71 .38 .50

Test 3 Distance (cm) 130 70 140

Test 1 speed (cm/s) 277.8 cm/s 294.1 cm/s 245.3 cm/s

Test 2 speed (cm/s) 193.5 cm/s 185.2 cm/s 172.4 cm/s

Test 3 speed (cm/s) 218.1 cm/s 221.2 cm/s 232.6 cm/s

Refining

I would have used a lighter wood, instead of a 2x4 perhaps a 2x2. I would make the projecting arm longer, instead of 12 inches, perhaps 14 or even 16”I would Make the sides longer, instead of 12” probably 18”. I would also make the structure before the projecting arm stable using nails instead of screws.

Creating

To create my catapult I used:

3 pieces of wood 12 inches long 8 pieces of wood 6 inches An assortment of small screws and/or nails 1 large rubber band or several smaller ones 2 eye hooks (to the right of the rubber band Some glue (optional but a good idea)

Results

My catapult was efficient, however due to lack of stability it wasn’t able to fling items far distances.