The Ottawa CWC Engineering Competition will be postponed until 2009
Location: TBA
Date: TBA
Projectile fabrication
The projectiles are the same as last year. They are concrete filled wiffle-balls, 10 cm in diameter. The empty white plastic shells can be purchased for $5 at Toys-R-Us. The concrete is a basic ready-mix with aggregate that is small enough to fit through the wiffle-ball hole. You can make a slightly larger hole to make it easier to fill the ball. The ball should be wrapped in tape to cover the other holes though. The ball should weigh approximately 770g or 1.7 lb once the concrete has cured.
1.0 Objective
To design a lightweight wood catapult capable of accurately hitting targets at 20, 30, and 45 meters using a 2-lb ball.
2.0 Eligibility
Teams must consist of students registered at a Canadian university or college, and one faculty sponsor, who will oversee the design and construction phases of the project. Each team can have a minimum of two and a maximum of ten participants.
There are no restrictions to the number of teams a university or college can have.
Each team is responsible for transportation and operation of their prototype at the competition site. Each team will designate a captain who will ensure compliance with competition rules.
3.0 Required Materials
3.1 Materials allowed
All structural and propulsion materials must be made out of wood. All native wood species, engineered wood products (I-joists, lumber, glulam, PSL, LVL, etc…), and wood panel products (plywood, OSB, particle board, MDF) are allowed. Steel screws, nails, dowels, pin, hooks, and bolts are allowed in connections.
For trebuchets, counter-weights may be any material.
Glue is allowed to join wood members together.
Single flat steel plates, 6 inch x 1.5 inch x 1/4 inch thick maximum, are allowed on a maximum of two sides in a connection.
Yellow propylene or polyethylene rope is allowed. No other rope type is allowed.
A metal winch to wind the catapult is allowed.
Metal pulleys are allowed (2 inch wheel maximum, must be commercial pulley, not home-made). Metal safety latch mechanism is allowed.
Cloth netting or metal bowl or cup to hold projectile is allowed. Winding bars (for ballistas and onagers) may be out of metal.
3.2 Materials disallowed
Non–wood materials, including wood-plastic composites, concrete or steel, as or in, structural members;
Angle iron and welded plates;
Sheet metal and protective steel;
Hidden metal connections or anything other than specified in 3.1;
More than one plate on one side of a connection;
Steel in areas other than connections;
Steel bearings;
Elastics and bungey chords.
A momentum-inducing mass may be composed of any material (included in allowable weight), should it be required. ONLY WOOD IS ALLOWED AS PROPULSION MATERIAL; Steel and elastics are not allowed in this case.
The lock and release mechanism must safely retain the potential energy of the armed catapult.
Failure to respect these rules will not limit a team’s participation in the competition; however, the team will severely impede contention for any prize.
3.3 Contravening penalties
Should a team contravene to the rules above, point penalties will be applied as a means to keep the team in contention for prizes.
These offences are cumulative. If a team commits more than one type of infraction, they will be summed and tallied against the score obtained at the competition.
If a team is deemed unsafe during the execution of their trials the judges reserve the right to stop their trials or give time penalties in increments of 2 minutes.
A sheet with penalties types and points loss will be distributed on the day of the event prior to the beginning of the trials.
4.0 Design
The prototype cannot have a mass of more than 70 kilograms – including the momentum-inducing mass or ANY winding tool, but excluding the projectile. The weight of any material used to keep the apparatus in place during the trials is not counted in the overall weight measurements. The catapult must be light enough to be carried by hand and must be designed to be easily assembled and disassembled on-site – if necessary.
The maximum length of the launching arm is 4 metres, from the fulcrum to the end. For a crossbow-type arrangement, the lateral flexion arms can be no more than 8 metres from end to end.
5.0 Rules of the Competition
5.1 Prototype Presentations
Each team will be required to submit a short report (10 pages or less) in three copies to CWC by January 29, 2007. The report should include:
Technical description and materials used;
Methodology to arrive at the final design;
Prototype plans, and details or photos, and
Any preliminary testing and results.
The report will be counted as part of the performance trials. However, there will be an independent prize given to the best presentation.
Each team will be required to make a 15-minute presentation of their prototype on site, explaining the design and function, the type of materials used, overall specifications, performance of initial tests, and any other tests that were done prior to the competition. Teams will be judged on:
The prototype plans and details (10%);
The methodology used to arrive to the final design (10%);
The quality of the presentation (20%);
The quality of the report (25%); and,
Their use of wood (35%).
The presentation should be clear and include the following:
Design process;
Technical description of materials used;
Overall specs of the catapult;
Any material testing;
Preliminary trial results; and,
Any modification performed on the design before the event.
5.2 Performance Trials
Each team will be required to assemble their prototype on-site; that is, it is expected that the prototypes will be partly disassembled for transportation and assembled near the test site. Team members will be required to carry the catapult to the launching area. The trials will be as follow:
Three one-square-metre targets installed vertically at ground level will be placed in alignment at 20 metres, 30 metres and 45 metres. The objective is to hit all targets at least once within a period of 30 minutes using the 2-lb ball provided, and then accumulate as many points as possible. Rebounds or bounces will not count as a hit. Points will be awarded as follows:
20 metre target- 20 points per hit;
30 metre target- 30 points per hit;
45 metre target- 50 points per hit.
Priority will be given to teams that hit all three targets. For example, a team may still win with 100 points by hitting all three despite the fact that another team gained 110 points by hitting the first target once and the second one three times and never hitting the third one. There is no required order with which participants must hit the target.
No more than two members of the team are allowed to wind, or provide the potential energy to the catapult. The catapult must be able to launch the projectile without human intervention. That is, only the mechanisms of the catapult can provide energy to the projectile.
During trials, team members are not allowed to lean over the catapult to hold the pivoting arm or any movable component in order to accelerate the winding process. Team members must remain clear of counterweights for the trebuchet. At all times, team members must be at a safe distance from the catapult.
All projectiles will be provided by the competition. Teams should ensure that the catapult design include provisions to keep the projectiles attached to the apparatus during launching.
5.3 Distance Trial
Independent distance trials will be organised after each performance trial. Teams will be given five supplementary minutes or three chances to achieve the longest throw possible using the 2-lb ball used in the performance trial. This throw is irrespective of accuracy but must be in the forward direction. A separate prize will be given to the team that achieves the longest throw.
6.0 Judging criteria
In order to win, a team must hit all three targets and accumulate as many points as possible in 30 minutes. Should none of the teams hit all three targets, the team that hit the most targets and accumulated the most points wins.
7.0 Location and Dates
The competition will take place at the Museum of Science and Technology on Saturday, February 10, 2007. Participants are responsible for their accommodation. On the day of the competition, both lunch and award supper will be organised and provided by CWC.
Students can register at any time. Final date for registration to the competition is November 24, 2006. The form should be mailed or faxed to CWC by the deadline date.
8.0 Prizes
Prizes and awards will be distributed at an award supper, organised and sponsored by CWC.
Winning teams will receive a team cash prize as well as individual copies of CWC manuals of their choice. Winning prizes will be as follows:
- 1st Place - $1500 + 1 CWC Manual
- 2nd Place - $1000 + 1 CWC Span Book
- 3rd Place - $500 + 1 CWC Span Book
- Best Presentation- $300
- Maximum Distance Prize- $200
There will also be prizes for aesthetics, and Spirit.
For more information or clarification on the competition, please contact info@cwc.ca or 1-800-463-5091 x239.
