Check-in begins at 4:30PM, bridge loading at 5PM.
The competition will be held in the Comstock Memorial Ballroom in the Comstock Memorial Union, at the corner of 14th St S and 6th Ave S, on the campus of Minnesota State University Moorhead.
The competition is open to all students grades 1 through college. Students are invited to build a structure using only wood and glue that:
You'll load your bridge with weights. When the bridge breaks, we divide the load it held by the weight of the bridge to determine its strength. The strongest bridges win cash prizes!
The contest is open to any student, grades 1 through 12, plus students enrolled full-time in college. Entrants will be assigned an entry class:
Bridges built by teams of students will be assigned the class of the student in the highest grade.
At check-in, judges from the Fargo-Moorhead Engineer's Club will evaluate each bridge. Bridges will be weighed, measured, and reviewed for compliance with rules regarding materials. If a bridge does not comply with any of the rules, it will be disqualified from competing for the prizes, but may still be loaded to determine its strength. The decisions of the check-in judges are final.
The structure will be placed in or on supports made from two 2x4's as shown in the illustration. Structures with no arch in the bottom chord will be placed on the supports to achieve the required minimum span. No lateral or side support is allowed.
Round metal weights, approximately 220 mm in diameter, will be placed on the top of the structure at the mid-span by the contestants until failure. A 160-mm round wooden disk will be available to place between the structure and the weights, if desired. Contestants may use cards to shim the base of the bridge level. Entrants in the elementary class may ask for assistance in loading their structures.
Judges from the Fargo-Moorhead Engineers Club will record the total weight supported by the bridge. The judge will make the final decision as to whether a structure successfully supported the final weight before failure. The total weight supported will then be divided by the recorded weight of the structure to determine the strength ratio of the bridge.
Reminder: Bridge performance is judged by the weight supported divided by the weight of the bridge. The winning bridge might not be the bridge that supports the most weight.
Note from the rules that the winner is judged not on the total weight supported, but rather on the capacity of their bridge - weight supported/weight of the bridge. That means that if a bridge is very light and moderately strong, it can win over a stronger, heavier bridge.
Gluing the toothpicks together can take time and is delicate work. Lay out a sheet of wax paper, glue together several toothpicks to form a base plane, and allow that to dry. Then glue members to the base plane in order to create a space frame.
In the past, many people have built flat bridges - mats of toothpicks only 2 or three layers deep, and containing no support shapes. These have never been successful. They bend under even a very small load and split. Create a bridge with some depth - use some method to create a support structure that transfers the weight from the middle of the bridge to the supports.
Some useful shapes to use as building blocks are:
You will be asked to provide the name(s) and grade(s) of the students for each bridge entered in the competition.