2011 Towers. Jay Ralph Steve Dean Greg Marconnet Wisconsin Science Olympiad January

Transcription

1 2011 Towers Jay Ralph Steve Dean Greg Marconnet Wisconsin Science Olympiad 1

2 Tower Objective Design and build the most efficient tower as defined by the Tower Score to hold a single point mass Tower Score = mass held by tower 2 / mass of tower. Key changes from previous years Wood size no longer limited the ¼ x ¼ rule dropped! Mass held is squared! 2

3 Project Log While it is not required, we encourage the development of a project log for the following reasons. Reinforces use of the scientific process or method It is good documentation for this year s and next year s team! Practice for workplace research (future career?). Include in the log: Tower research Design hypothesis Tower design and calculations Testing notes, photos and sketches Observations and conclusions Web references 3

4 Key Construction Rules for 2011 Rule Rule Text 3.a Tower must support loading block a minimum of 50.0 cm above test base 3.b The tower must span a 20.0 cm x 20.0 cm opening on a test base The tower must not be braced against any edge of the test base for lateral 3.c support at any time. No portion of the tower is allowed to extend below the top surface of the test base prior to testing. 3.d The portion of the tower more than 30.0 cm above the test base for Division B, or more than 15.0 cm above the test base for Division C, must pass through an 8.0 cm diameter circular opening or hole 3.e The loading point on the tower must permit placement of a loading block and supporting a chain 3.f The chain must pass through the tower and be within 2.5 cm of the center of the test base opening when the bucket is attached. 3.g Single structure, no separate or detachable pieces Constructed of wood and bonded by glue. Other materials must not be used (e.g. 3.h no particleboard, wood composites, bamboo, paper, or commercially laminated wood). 3.i Unlimited lamination by the student is allowed In the 2009 Wisconsin state competition, 11 of the 59 of the Elevated Bridges did not meet the building rules! 4

5 Div. B & C =50.0 cm Div. B =30.0 cm Div. C =15.0 cm Tower Measurements Rule 3.a. Tower is a minimum of 50.0 cm high to loading block Rule 3.d. The portion of the tower more than 30.0 cm above the test base for Division B, or more than 15.0 cm above the test base for Division C, must pass through an 8.0 cm diameter circular opening or hole 8 cm dia. or less Height: OK, at or above 50 cm Height: NOT OK, below 50 cm Height: OK, at or above 50 cm Height: OK, at or above 50 cm Transition: NOT OK, above 15/30 cm Transition: OK, at or below 15/30 cm Transition: OK, at or below 15/30 cm Transition: OK, at or below 15/30 cm 5

6 What s not in the rules! Tower may slide during loading Tower may sag when loaded (but not touch the base) No maximum size of tower, but needs to fit on test stand 6

7 Web Support Science Olympiad main page: Science Olympiad Towers, Division C: Science Olympiad Towers, Division B: Check out the Student Wiki and Topics forums Truss Analysis Application for Tower Design: 7

8 Tower Building Considerations Design Wood Glue Building Tips Testing Day 8

9 Tower Building Considerations Legs: 3?, 4?, or more? 3 legs would seem to be the most efficient, but the 60 degree angles are hard to build. 4 legs is easier to build as the 90 degree angles of the sides are easy to work with. Personally, I would start here. More legs makes construction more difficult and I do not see any advantages. 9

10 Tower Building Considerations If the dotted lines represent the 20cm by 20 cm opening to be spanned orientation of the tower can allow for a smaller base (square base). 10

11 Photos from Previous Meets 11

12 Photos from Previous Meets Heavy and probably overbuilt Heavy, probably overbuilt and may not meet 8cm rule Bent wood on the 4 corners nice

13 Photos from Previous Meets

14 Photos from Previous Meets

15 Photos from Previous Meets

16 Wood Balsa, strongest wood, pound for pound! Species Density (Lbs / cu Ft) Stiffness Bending Compression Balsa Balsa Balsa Basswood Pine, Spruce Yellow Pine Balsam Fir Black Walnut Oak Hickory NOTE ABOUT CHART: The strength of balsa varies in direct relation to its density or weight - the heavier the wood the stronger it is. The above chart was designed with 10 lb./cu. ft. balsa as the median. In other words, balsa at IO Ibs./cu. ft. has been tested given a value of 100. The other woods were then tested in the same way and given a figure that is numerically in proportion. By comparing the relative strength figures in the chart, it will be seen that balsa is as strong or stronger, pound for pound, than most of the species shown. From: SIG MANUFACTURING'S INTERESTING FACTS ABOUT BALSA WOOD 16

17 Wood Check carefully for grain defects, cuts, chips or other damage. Mass like size woods for consistency of density especially balsa. Consider laminating thin layers of wood to take advantage of multiple wood grains. 17

18 Joints Good craftsmanship is critical! Cut wood with sharp tools, do not crush wood Good joints = joints with no gaps Slight roughness glues better than super smooth Poor Joints Good Joints Well cut and fit joints Flat joints are easy to make 18

19 Glue Read the Material Safety Data Sheet (MSDS) Safety First Glue Choice not critical from a strength point of view. Wood shear parallel to grain is less than 2,000 psi for common woods, most glues above 2,000 psi. Use sparingly it is heavy Shelf life is typically a year or two...check date code 19

20 Glue GLUE OPTIONS Shear Strength (psi) Open Time / Clamp Time (Minutes) Polyvinyl Acetate Polyurethane Epoxy Cyanoacrylate 3,600 3,500 2,000 3, / / / 45 1 / 1 Notes Water based, will not fill gaps Needs moisture to cure Does not shrink Will not fill gaps Health / Safety Wear PPE* Wear PPE* Wear PPE* Cost ($/oz) (more stars, higher cost) Brands Titebond Original, Elmer s Carpenter s, Tacky Formula Modeling Glue Gorilla, Elmer s Probond, Titebond, ExcelOne System Three T-88, Industrial G-1 Gorilla Super, Krazy glue, Super T, Permabond *PPE = Personal Protective Equipment 20

21 Gluing Clean, dry, dust free surfaces! Maximize surface area wet both surfaces with glue and then assemble. Normally need to clamp joint for best bond and air elimination Glue at 65 F or higher 21

22 Assembly Tips Draw plan to scale Place plan on Styrofoam Cover with wax paper Build: pin in place & glue Weigh down or clamp 22

23 Assembly Tips Based on your design, align sides so they are straight, square and parallel. Be sure to install cross bracing between sides to prevent sideways sagging Consider building a fixture or jig. See photo: 23

24 Bending Wood Design shape, build form. Styrofoam can be good for Balsa wood. Steam or soak wood in hot water until soft Use diluted glue if laminating. Clamp until dry Web reference: 24

25 Storage and Transportation Cardboard box with Styrofoam packing peanuts works great! (Shown with Elevated Bridges) The ultimate in transport boxes, wooden box with carrying handle for a tower!! Includes a space for the tower and protective eye gear. (Cover not shown) 25

26 Test Day! Finally! No impound, so bring Tower in a box and store safely. Register for a test time Check-in 10 minutes before test time and have Tower inspected Test! 26

27 The scoring sheet is a summary of the rules. It does not replace the rules! Check-in Scoring Sheet However, you should review your design with this sheet! Web links: Wisconsin SO: National SO: Division B: click on scoresheet National SO: Division C: click on scoresheet 27

28 Eye Protection Contestants are responsible for providing safety spectacles with side shields (rule 2.b) Eye protection must be manufactured to meet the American National Standards Institute standard. The current standard is ANSI Z Approved protective eyewear can be identified by the mark "Z87" High impact particle protection may be used and is designated by Z87+ Note: Prescription glasses must bear the "Z87" mark to be used. Web link: 28

29 Eye Protection 29

30 Test Stand Sand or similar will be used for the load kg of sand will be loaded into the sand hopper before the test (including loading block assembly). Sand hopper Sand release handle Test base 30

31 Test Base Minimum Size: 55 cm x 32 cm Opening 20 cm x 20 cm Smooth, hard surface (such as metal or laminate) 31

32 Loading Block 6 mm diameter maximum Block 5.0 cm x 5.0 cm Made of any material (typically wood, plywood, steel or aluminum) Bolt ¼ inch threaded eye bolt with washers and wing nut. Outside diameter of eye will not exceed 6 mm Chain Standard wire chain, 75# test Open s hook for attachment 32

33 Testing Contestants will: Wear eye protection Set Tower on stand Set loading block and attach bucket Load the sand until failure, until15 kg. loaded or until 10 minutes has expired. 33

34 Tower breaks Failure is when: Tower deflects so that the Tower or loading block touches or extends below the top surface of the test base within the clear span. The bucket rests on the floor (Rule 5.h) 34

35 Ranking of Towers Summary of section 6 of rules Tier 1 meets all construction parameters Ranked ahead of Tier 1 and Tier 2 by score Event Winner: Tier 1 Tower with highest score Note - Load Supported for scoring purposes the load scored cannot exceed 15,000 grams 35

36 Ranking of Towers Tier 2 one or more construction rules is not met Ranked after Tier 1 Ranked by Score Tier 3 unable to be loaded Ranked after Tier 1 and Tier 2 Ranked by lowest to highest tower mass 36

37 Top Issues with Past Towers Tower not built to specifications Tower does not span 20cm x 20 cm opening Height, less than 50 cm Transition too high Painted or coated wood Loading block will not fit on structure Chain does not pass thru structure Structure is broken or damaged in transporting to meet Not built straight causing unbalanced forces 37

38 Suggestions Read the rules Re-read the rules Do some research; books, internet or just look at some Towers. Talk with your Physics and TechEd teachers! They will have ideas! Video all tests! Review in slow motion. Build, test, break, review and document in log. Build, test, break, review and document in log. Build, test, break, review and document in log. Target 1 cycle per week! HAVE FUN!!! 38