Middle School Bridge Design 2015
Event Coordinator:
Ken Moliterno kmoliterno@oahornets.org
Description:
The objective of this project is to design and build the lightest bridge capable of supporting a given load.
The bridge is a cantilevered wooden structure, which will be attached to a vertical- testing wall at one end,
and supporting a load at the distal end.
A Team up to:
2 Students represented at Tech Wars3 Bridges Per / School
The Competition:
Materials:
1. The bridge is to be a SINGLE structure constructed of wood and bonded by Titebond 1 glue. No
other materials shall be used. Bamboo is NOT a wood.
2. The bridge must be constructed of pieces of wood no larger than ¼” high and ¼” wide. Any
dowels used cannot have a diameter greater than ¼”.
3. The bridge will have an attachment base which will be constructed of standard (Solid) pine wood
with a dimension of 11” x 6” x ¾” thick. The base board must be a solid board, unmodified, cut
or drilled…and cannot be created with laminating. The attachment base MUST then be
permanently attached to the bridge.
4. There is no limit on the length of individual wood pieces used in the construction, with the
exception noted for the attachment base.
5. Only common Titebond 1 wood glue may be used.
6. NO Gussets can be utilized(With any material), even with glue…
Construction
1. All construction must be completed prior to the event.
2. Sound engineering practices such as good truss construction, and mitered joints are encouraged.
3. Do not coat the bridge with any materials (i.e. paint, stain, or glue).
4. Unlimited lamination (i.e. bonding together layers of wood) by the student is allowed not to
exceed the maximum 1/4”x1/4” sizing.
5. The bridge must be constructed to meet the following parameters:
1. It must be designed in such a way that it can be attached to the vertical-testing wall with
two ¼” bolts. The bolts will be precisely 7 7/8” apart on center horizontally. The bridge will
have a permanently attached base in such a fashion that it can be attached to the Testing
Wall.
2. The bridge must support the loading block at a minimal horizontal distance of 15 ¾” from
the vertical-testing wall.
3. No part of the bridge may touch the vertical-testing wall further than 6” below the
attachment holes.
Testing
1. All bridges will be assessed prior to testing for construction requirements and dimensions.
2. Students must wear eye protection during loading and testing.
3. The loading block, testing wall, attachment hardware and loading material will be provided.
4. The vertical testing wall will be a piece of 3/4” thick plywood or other suitable material around 17
¾’wide and 11 ¾” high with two ¼” diameter holes 7 7/8” apart on center horizontally 2” from
the top.
5. The bridge will be attached to the vertical-testing wall with one or two 2” long ¼” threaded
bolt(s), washers (not to exceed 3/4” diameter) and wing-nuts through the holes in the testing
wall. The bolts will be placed so that the head of the bolt is on the same side as the bridge.
6. The center of the loading block will be placed on the bridge beam a minimum of 15 ¾” from the
vertical-testing wall. Remember that the loading block is 2” wide so the length of the bridge
should be GREATER than 15 ¾”.
7. The load will be applied to the loading block by an eyebolt and S-hook.
8. The loading block will be 2” long and 2” wide and ¾” high.
9. A bucket will be attached to the S-hook, and the S-hook is attached to the eyebolt on the loading
block.
10. The student will add sand to the bucket.
11. The maximum allowable time for set up and loading will be ten minutes. If the time expires, the
bridge is ranked with those that could not hold the 33 lbs.
12. The student will add sand to the bucket until failure occurs or the maximum load (33 lbs) is
supported. The maximum load (33 lbs) incorporates the total mass of the loading apparatus,
bucket and sand.
13. Bridges that experience failure before reaching 33 lbs will not be disqualified.
14. Failure is defined as the inability of the bridge to carry additional load without breakage or the
inability to hold the maximum load for 5 seconds. Excess sand added after failure will be
removed.
Scoring
1. The score (Structural Efficiency) will be determined by the equation:
Structural Efficiency = Load supported (grams)/Mass of Bridge (grams). The maximum load
supported cannot excel 33 lbs.
2. The bridge that held all 33 lbs for 5 seconds with the highest structural efficiency would be the
winner, while others with lower efficiencies would place next.
3. Bridges that meet all the specifications under Materials and Construction, but did HOLD the
entire 33 lbs will be ranked next.
4. All bridges with Construction and Materials programs will be ranked next.
Maximum Time:
10 Minutes
Impound:
Yes