BRIDGE BUILDING CONTEST

 

Objective: 

Make a bridge that will withstand the greatest amount of force without dropping to the ground.

 

Rules:

Sticks- A maximum of 75 coffee stirring sticks may be used.  The sticks can be cut in any direction, shaved, drilled, sanded, tapered, doweled, or otherwise worked to suit the design.  Only wood given by Mr. Hund may be used.

 

Glue- Any form of glue can be used but not resin.  Sticks and glue only!!

 

         Length- A minimum of 40cm.

 

Width- A minimum of 5cm with a solid unobstructed deck which an object could travel across.

 

Height- A maximum of 20cm.

 

Design Principles:

         When lightweight and strength are needed, a truss is useful.  One truss design is shown below.  The arrows show the forces that are felt by various parts of the truss.  Struts transfer force from one chord to the other.  The secret of the truss is the way it redirects the downward force to the side.

 

 

 

 

 

 

 

Construction Tips:

Be sure that all pieces fit well.  A solid glue joint is very important.  A glue joint will be stronger if the pieces are clamped together during drying.  Clamps, cloths pins, or a stack of books will do the job.  Glue becomes stronger with time.  The glue joint will be vastly stronger after one week than one day. Bridge building links are available at my web sites. https://robhund.tripod.com/mrhundscience/

 

Force Test:

The bridges will be placed between two desks 36cm apart.  A testing devise will be put over the top of the bridge and mass will be added to a bucket below. I will not test any bridges that do not meet the minimum rules requirements.

 

Grading Procedures:

All students start with 30 points.  The students who design the four strongest bridges in each class will receive 10 extra credit points.  The students with the next four strongest bridges will receive 5 extra credit points and the next four bridges will earn the students 3 extra credit points.  Five points will be taken off for the following and will not qualify for extra point.

 

                  SLOPPY WORK                   LESS THAN 40 cm SPAN

                  TOO TALL                             MORE THAN 75 STICKS       

                  TOO WIDE                            ANY EXTRA MATERIAL

 

The students who design the top four bridges from Team Excel will have lunch at HilbertoÕs.