From Engineering Exposition

SPONSORED BY

The UofL Student Chapter of the American Society of Mechanical Engineers (ASME)

A PDF of the rules can be downloaded here.

Contents 1 Mousetrap Catapult Design Competition 1.1 Background 1.2 Deadline and Contacts 1.3 Rules Regarding Materials To Be Used 1.4 Rules Regarding the Design 1.5 The Competition 1.6 Scoring 2 Registration Form 3 Acknowledgements

Mousetrap Catapult Design Competition

Background

This competition is based on the medieval catapult: a device that was used to hurl large "rocks" into an opposing force's castle. The catapult was designed to be adjustable to meet varied conditions such as the distance from which the rocks were hurled at the castle and the elevation between the catapult and the castle.

The objective of the competition is to design and construct a catapult that shoots Ping-Pong balls, using inexpensive and readily available materials.

Deadline and Contacts

Registration for this event will be open until the week before the event March 1st. So come and register!!

Any questions about the competition or rules may be sent to Tyler Kmetz, the president of ASME, at tmkmet01@louisville.edu.

Rules Regarding Materials To Be Used

1. A standard, commercially available mousetrap (i.e. not a rat-trap) will be used as a catapult to throw ordinary Ping-Pong balls into a sand pit target.
2. The competitors are allowed to use any inexpensive and readily available materials to build the catapult. Commonly used items, such as plastic spoons, string, glue, Popsicle sticks, wooden dowels, rubber bands, etc., are common materials that may be used. In other words, no titanium shafts, no rocket launchers, no explosives, etc. are to be used. If competitors have a question about the use of a particular material, they are asked to contact the competition's sponsor to obtain a ruling.

Rules Regarding the Design

1. The swinging arm of the mousetrap may not be assisted in the direction of throw (acceleration) by anything attached to the main body of the structure or launching surface. Simply stated... don't use rubber bands (or anything else) to boost the power of the mousetrap spring.
2. The length of the mousetrap arm may be extended. The swing of the mousetrap arm and any extension shall not be assisted by anything attached to the main body or launching surface. The throwing action must be the free action of the mousetrap.
3. The catapult may be attached to a wood or cardboard base plate no more than 1/2" thick. The base plate can have any width or length, as long as it fits within the launching site (2' x 2'). The plate must sit firmly on the launch surface and cannot be used to adjust the height of the toss although it may be pivoted (rotated) for aiming in the proper direction.
4. There is no restriction on the orientation of the mousetrap. The catapult can throw the Ping-Pong balls overhand, side arm, or underhand. However, the Ping-Pong ball must, at some point from the initial firing position to the time it is released, pass within 3 inches of the base plate. Bottom line - long legs can't be used to artificially raise the height of the catapult.

 

The Competition

1. Each team will bring their catapult to the competition site fully assembled and ready to compete.
2. The competitor's device will be placed within the launching site on the floor. No part of the device may extend outside the launching site before a shot.
3. The target is a sandpit with inside dimensions of 2' x 3' and it is 2' to 3' high. The 2' side of the pit will be parallel to the leading edge of the launch site. The distance from the center of the launch site and the center of the pit may vary from 8' to 15' (see drawing).
4. The catapult may be manually held in place on the floor to steady it; however, the participants must be completely clear of the launching arm.
5. The launching arm must be set in motion by pressing the normal mousetrap release lever using a pencil or dowel stick to insure the safety of the participants.
6. Each team will be given 5 minutes to setup the catapult in the launch site and complete ten shots at the target. Then, the target will be moved to a new position and the process repeated. No practice shots will be allowed; however, adjustments may be made to the device between shots. (Teams are encouraged to develop and use some method to determine the best launch parameters to use during the event. Room ceiling height may be a factor.)

Scoring

1. Any hit within the sandpit will count equally. However, the shot must land inside of the pit and create an impression in the sand in order to count as a hit. A shot that strikes the edge of the pit will not count as a hit. The team with the most hits out of twenty shots is the winner.
2. Ties will be broken by a one shot "shoot-off" for distance. The team that can make the necessary adjustments to their catapult and get the most distance will be declared the winner.

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Registration Form

Acknowledgements

• ASME.org
• The USC Student Chapter of the Institute of Industrial Engineers (IIE)