BrainQuest 2011 Darul Arqam North

Transcription

1 BrainQuest 2011 Darul Arqam Nrth The Tthpick Bridge Challenge The cmpetitin is pen t all students in grades 4 thrugh 12. Students are invited t build a structure using nly rund wden tthpicks and glue that: Spans mre than 56 centimeters. Stands n mre than 30 cm tall. Weighs less than 85 grams. Must have an pen ROADBED where a car culd pass thrugh if it were used as a real bridge. There MUST be a lcatin t place the lad-testing apparatus n yur bridge! Yu'll lad yur bridge with weights. When the bridge breaks, we divide the lad it held by the weight f the bridge t determine its strength. The strngest bridges win cash prizes! The Rewards: 1st Place High Schl (Grades 9-12) 2nd Place High Schl (Grades 9-12) 3rd Place High Schl (Grades 9-12) Best Appearance High Schl (Grades 9-12) Entrants: The cntest is pen t any student, grades 6 thrugh 12. Entrants will be assigned an entry class: Middle Schl (Grades 6-8) High Schl (Grades 9-12)

2 2011 Official Rules The gal f the cmpetitin is t design the strngest pssible structure t span at least 560 mm using nly rund wden tthpicks and glue. The strength f the structure will be determined by dividing the lad it supprts by its weight. Design Cnstraints: Mass: The ttal mass f the structure cannt exceed 85 grams (3.00 z) Span: Each structure must span at least 560 mm clear f any supprts. Height: The verall height f the structure may nt exceed 300 mm. Tthpicks: Only rund wden tthpicks may be used (square tthpick with runded ends will nt be allwed). At least 50% f the surface area f each tthpick must be visible and clear f glue. The tthpicks are t be glued tgether as they cme frm the bx. N cutting, splicing, r fraying f the ends is allwed, except: the tips f the tthpicks at the tp f the structure may be trimmed ff t enable the weights t rest flat n the tp, and the tips f the tthpicks at the ends f the structure may be trimmed t allw the structure t butt up flush with the supprts. Glue: Only a white glue, such as Elmer's, r a yellw wdwrking glue, such as Titebnd, may be used. Structures built with ther glue will be disqualified.

3 Catings: Structures may nt be painted, sprayed r dipped in any cating material. Cmpliance: At check-in, judges will evaluate each bridge. Bridges will be weighed, measured, and reviewed fr cmpliance with rules regarding materials. If a bridge des nt cmply with any f the rules, it will be disqualified frm cmpeting fr the prizes, but may still be laded t determine its strength. The decisins f the check-in judges are final. Supprts: The structure will be placed in r n supprts made frm tw 2x4's as shwn in the illustratin. Structures with n arch in the bttm chrd will be placed n the supprts t achieve the required minimum span. N lateral r side supprt is allwed. Lading: A (9) inch diameter rund cntainer will be placed n the tp f the structure at the mid-span by the cntestants. Gravel will be added t the cntainer until structural failure. Scring: Judges will recrd the ttal weight supprted by the bridge. The judge will make the final decisin as t whether a structure successfully supprted the final weight befre failure. The ttal weight supprted will then be divided by the recrded weight f the structure t determine the strength rati f the bridge. PRIZES: The three strngest bridges verall will be awarded First, Secnd and Third Place prizes. First Place - Trphy and a gift certificate. Secnd Place - Trphy Third Place - Trphy Best Appearance - Plaque A panel f judges will view all the bridges as they are checked in, and will award a prize, based n quality f cnstructin, and verall appearance.

4 Tips n Tthpick Bridge Engineering Gal: T make a cnstructin f tthpicks and glue that will weigh less than 85 grams, have a clear span f 56 cm, and will supprt a weight stacked n a 9" diameter wden disk placed n tp f the structure. Nte frm the rules that the winner is judged nt n the ttal weight supprted, but rather n the capacity f their bridge - weight supprted/weight f the bridge. That means that if a bridge is very light and mderately strng, it can win ver a strnger, heavier bridge. Gluing the tthpicks tgether can take time and is delicate wrk. Lay ut a sheet f wax paper, glue tgether several tthpicks t frm a base plane, and allw that t dry. Then glue members t the base plane in rder t create a space frame. In the past, many peple have built flat bridges - mats f tthpicks nly 2 r three layers deep, and cntaining n supprt shapes. These have never been successful. They bend under even a very small lad and split. I strngly urge the students t create a bridge with sme depth - use sme methd t create a supprt structure that transfers the weight frm the middle f the bridge t the supprts. Tp members need t be strnger than bttm members - when the lad pushes dwn, the tp ges int cmpressin, bends and snaps. The bttm ges int tensin. It just needs enugh glue t keep it tgether. Ask yur students if they can pull a tthpick apart as easily as they can push n them and break them. Here are sme typical shapes in tthpick bridge cnstructin: A) Psts - glue several tthpicks tgether side by side t build up a rund member the size f a pencil. These members will be very strng in cmpressin, but will still need supprt t keep them frm buckling. B) Triangular space frames. Typically, the strngest space frames are made by cnnecting triangles. Yu can begin by building a tetrahedrn. First, glue tgether 3 tthpicks t frm a triangle. This is yur base plane. When it dries, add 3 mre tthpicks (ne at each crner) t frm a 3-sided pyramid, r tetrahedrn. Yu can add t this shape by gluing 3 mre tthpicks t any f its triangular faces. The weak pint n these is usually the crners - let the tthpicks crss ver each ther slightly, and cver the jint in glue. C) Trusses - like the rafters in a rf, r the typical steel bridge. Trusses are usually built by cnnecting a series f triangles in a plane. Bridges can then be built by setting tw trusses parallel t each ther and cnnecting them with crss members.

5 Tthpick Bridge Designs - Truss Bridges A cmmn bridge design was the Warren truss bridge patented by James Warren and Willughby Mnzni in The diagnal braces f this design pint bth twards and away frm the midpint f the bridge. Thus they experience bth tensin and cmpressin stresses as a lad, such as a trains, crsses frm ne end t the ther. Similar t the abve Warren Truss Bridge, the vertical supprts at greater stability and strength. When building yur tthpick bridge, be sure t include these vertical struts. It really makes a difference. Subdividing yur tthpick bridge using smaller pieces f tthpicks will reinfrce yur design. Be sure t select the best tthpicks as the quality will affect the strength f the tthpick bridge.

6 The Hwe Truss Bridge (designed by William Hwe ) was patented in The advantages f the Hwe Truss Bridge t the railrad cmpanies f the era were that it was easy t prefabricate ffsite and t ship by rail. When building yur tthpick bridge using the Hwe Truss, be sure t use crssing members t give it strength. Variatins f this crssing member design are easily lcated n the internet. As yu can see, the Baltimre truss bridge is a simple mdificatin t ther standard truss bridges. The smaller struts have been added t increase the supprt and imprve the lad distributin acrss the structure. When building yur tthpick bridge, be sure t glue the smaller struts perpendicular t the main crss beam.