Jan 25

Build an earthquake-safe structure

2015 April 26ready for judges

Day of the competition! Team 476 Gravity Rex gathered at the Tech Museum of Innovation with our building and engineering journal to compete with thousands of other kids and face a panel of judges. Our engineering journal was pronounced “good” as we could back up everything we claimed about our building and the process we followed to create it.  Our building, too, was good, leaning very little as the shake table tried to take it down.  Here are videos of our team’s introduction and three runs on the shake table.

Coteam staging areangratulations, team! Click on the photo to the right to see a panorama of the team staging area:

Our Thursday class is done, but we can look forward to the 2016 Tech Challenge on “flight”.  The Tech Museum may take a few months to figure out the details and guidelines for the competition, then test and revise them before public release.


2015 April 23

checking stability final building measuring floor separation Noting bulding specsIn our final class before the competition, we added a roof and the laser-reflecting paper.  Maverick had worked on the agenda and calculationsbuilding in between classes, adding metallic footing at the base of each of the four vertical dowels, and screwing these to a wooden baseplate replacing the earlier cardboard baseplate.

Nathanael documented the weight and height of the building.  He also measured spacing between floors and estimated usable floorspace.  Maverick diagrammed the final building on a 2-page foldout for our engineering journal.  He also wrote up an acknowledgement of help received from his father. Documenting sources of assistance and information is important in science and engineering.

To calculate floorspace, we reviewed the mathematics of linear and area measures. The vertical supporting posts are nearly half an inch thick, occupying almost 1/4 square inch.  With one at each corner, we lose one square inch of usable floorspace on each floor.  Diagonal bracing costs us even more.

We added an opening page to the engineering journal with our team number 476, name Gravity Rex, grade 7-8, and roster.  Maverick took the engineering journal home with the building and may do some homework on them.

We cleaned up our unused materials from the shed, recycling cardboard and taking home usable cardboard and dowels.  Sunday is our competition at the Tech Museum.  We will meet at 10:00 AM at

180 Park Avenue
San Jose, CA 95113
(Between Market Street and Almaden Boulevard)

.  More information is at http://thetechchallenge.thetech.org/important-dates/event-day.


2015 April 9

setting the 2nd floorteam namesWe began our fieldtrip with the discovery that our building had been damaged in storage.  Undaunted, we took the parts plus duct tape, string, and utility knife to the Tech Museum of Innovation.  There, we joined dozens of other teams working on their buildings.  Here are photos of the team names and of us working on our building.

There were wonderful varieties of buildings at the trials.  One, pictured, slide back and forth atop a foundation that insulated it from the shaketable almost entirely.  The judges kept increasing the energy of the shaketable, but the building hardly seemed to notice.competitor that rolls with quake  Some buildings were very tall, reaching toward the 7′ height limit (check the rules for 7′). Some had a central core that appeared to test the limit of 5″x3″ cylinders in the rules.  One building looked very light, with clear plastic floors and fishing line or dental floss as cross-bracing.  Some buildings were short and ungainly.  Others used bolts and springs to space floors.  Some were worked on by families, including adults well beyond the age categories. I find it hard sometimes to keep my ideas to myself and simply guide students to find their own answers and create their own building.judge meaures floor

Holes around our octagon are not symmetric, so we tested and rotated each floor until the supporting dowels were vertical.  This time, we labeled one side of each floor to ease alignment in the future, if our building is taken apart.  Using string as diagonal bracing proved difficult.  Unless taught, the string helps little, and getting it taught took persistence in choosing different anchor points and styles of knots.  Eventually, we got our building to stand upright, unlike the Leaning Tower of Pisa.

Called up for inspection by judges, we were surprised to find that our floors are less than 5″ apart.  That’s an area we had been careful to assure, by cutting oversize (and hard to find) straws to 5″ and using them to space the floors.  Something went wrong, which we will investigate in our next class.  Good news is that we are very light, so we can add much structure without violating the weight limit.  We know that we need at least one more floor to carry load bolts plus a roof with a card to reflect a laser beam (Nathanael will bring the cardstock).viewing shaketable from safety area

leaning tower of PisaOn the shaketable, our twine cross-bracing could not prevent the return of the Leaning Tower of Pisa, shown in one photo alone and one next to our team posed. Yes, our team is standing vertically so our building’s skew is no optical illusion. On the drive home, there was talk of a whole new approach, returning to a square floor.  With just 2 classes left before the April 26 competition, a fresh start may not be possible.  Nor may it be possible to go after the bonus points that the judges displayed in one of our photos.bonus points

posing by shaketableSince students have been haphazard at keeping an engineering journal, its creation will have to fit into one of those two classes or as a homework assignment.  Students may use this blog to jog their memory in that process and also print photos from here include in their journal, which must be on paper.


2015 April 2

Brennan wiring magnetic support Maverick spaces floors with straw sleeves over sticksMaverick and Brennan raise floors of the octagon Maverick measuring baseplate to within a quarter inchstring crisscrosses supports to strengthen against sway

Maverick sleeved the vertical wood columns with large straws (for which he and his father had to search many stores) to space floors the minimum of 5″ apart.  Since holes in the cardboard floors are just large enough to allow the wooden sticks through, the straws prevent each floor from collapsing onto the floor below.  While straws can bend, the wooden stick prevents their buckling, giving the straws apparent strength.  For our April 9 or 16 class, Maverick will try to bring more straws plus clear tape (e.g. scotch tape) to combine short straws.

Maverick also brought twine to create a crisscross pattern across vertical columns.  He tested this on one face, showing that it did provide good stability in one direction.  Crisscrossing every face should provide stability in all horizontal directions.

Brennan crafted magnetic supports, insulating the building from horizontal motion of the baseplate.  He wired a pair of repelling modules together in an attempt to keep the 4 pairs of repelling magnets from moving so far that they attract. The first length of wires he used did, however, allow sufficient shift to turn repulsion to attraction.  Bending the wires hurt his hands, discouraging him from testing shorter lengths in class.  He took the materials home to continue experiments.

Without functional motion isolators (magnetic or sliders, as Brennan developed earlier), Maverick duct-taped the octagon building directly to the 20″x20″ cardboard baseplate he fashioned in this class. The building has 3 floors, which we started populating with load bolts.  For the competition, we will need at least 4 floors, excluding 1st floor and roof, to accommodate all 20 load bolts.  We will also need to mount the cardstock that Nathanael will bring (he was away this class) and string all the open faces.  For next week’s test trial, we have enough of a building to test, so the fieldtrip is on.

Next week, please meet at Iris at 3:00 for a 3:15 departure time.  At the event, each student needs a helmet and safety goggles.  While a hardhat would look cool, a bicycling helmet would do.  I have safety glasses and a few old bicycle helmets (that fit me well, but may not students), so please let me know by Wednesday if you would like me to bring either for anyone.  I anticipate our return by 6:15, but cannot predict how much time students will want on the shake table or how slow traffic will be over the mountain.  If I can anticipate an earlier or later arrival time before starting to drive back from San Jose, I will text parents. Once driving, I will not text.

The inspiration of seeing other student groups testing their varied designs may be as valuable as testing our own and seeing more clearly what remains for us to accomplish.


2015 March 26

Maverick tests paper towel tubes to space floors Nathanael explores geometry for floors

Maverick continued development of an octagon building, while Nathanael came up with a geometry he has kept secret (we could only guess by looking at his building).  We had hoped to have straws to space floors in the octagon building, but nobody visited Jamba Juice since the previous class.  Cutting paper towel cores did not work well, as they were too large in diameter, though they would have satisfied the rule restricting size to 5″ long and 3″ in diameter or less.  Since floors must be separated by at least 5″, spacers thicker than 1/2″ must be exactly 5″.

Brennan brought a magnetic support he’d built since the last class.  It is a prototype that he prefers to the sliders he fabricated earlier.  We need at least 4 supports per floor, so Brennan will make at least 3 more, if not sets of 4, before our next class. He designed these supports on his iPad.

Maverick brought sticks and will bring straws and string next time.  Nathanael will bring sticks and the official cardstock for next class.  We have just one class before our fieldtrip to the Tech Museum for testing one or more buildings.


2015 March 19

Maverick drills octagon floorBrennan models twisting triangular floor Magnet concept, algegra, geometryMaverick is interested in octagonal  floors and Brennan in triangular floors. Both recognize that floorspace will be lost because the rules specify a maximum of 16″x16″ for lower floors, which is a square.  Other shapes fitting within those dimensions will have less area than the square.  Maverick thinks octagons will be more stable and look cooler. Brennan thinks triangles will be more stable because they have fewer directions in which they can fall, fewer axes of freedom.

Octagons and triangles gave us reason to explore geometry and algebra.  To calculate the size of an octagon inscribed in a square, we used the Pythagorean Theorem and Quadratic Formula, as shown in our very crowded dry erase board.  Each side of the octagon will be about 6.6 inches (metric would be easier, but the Tech Museum uses Imperial units).  That means we measure about 4.7 inches (just shy of 4 3/4 inches) in from each corner of a 16″x16″ square to identify the triangles to cut off in order to form an octagon. Maverick had multiple cardboard floors and punctured holes in each for supporting sticks.

To create right triangles from 16″x16″ squares, we could cut the diagonal, but Brennan wanted the symmetry of equilateral triangles.  He used geometry and a stick marked at 16 inches to sweep out arcs from two ends of a 16 inch line drawn on our giant cardboard sheets.  Those arcs intersect at one point, the 3rd vertex of the equilateral triangle. Brennan made multiple cardboard floors and modeled a building.

Brennan brought updated sliders, disc-within-in-a-circle, that are deeper and use Gorilla Glue (the hot glue on the previous shallow version failed).  He also proposed a magnetic flotation system with two magnets for each corner of our building.  In a square building, that would mean 8 magnets per floor.  With 5 floors, that would require 40 magnets.  He will test this concept with just 2 magnets to make sure it is worth scaling up.

For next class, please bring the following:

  • Brennan will bring magnets (or an assembled mag-lev pair with wood) and large straws (possibly from Jamba Juice) to slide over sticks for Maverick’s floor supports
  • Maverick will bring sticks and string (any might do, but he prefers twine)
  • Nathanael will bring sticks and one sheet of card stock (8.5×11″ 110 pound white)

We have 2 more classes before our April 9 fieldtrip to the Tech Museum.  If we do not have at least 1 building to test on the official shake table by the end of our April 2 class, we will cancel the fieldtrip to spend that time in class to develop buildings.  Today’s progress suggest that we might have 2 buildings, octagon and triangle, to test.  The fieldtrip would be 3:15 – 6:15 (approximate return time, I will text updates from the Tech Museum), replacing our regular class.


2015 March 5

Brennan and Nathanael test cross-bracingMaverick makes our first multifloor modelBrennans suspension idea

Brennan assisted Nathanael in testing cross-bracing on a building.  Components were longer than allowed in Tech Challenge, so this was proof of concept, so it was taken apart after the diagonal bracing proved resilient.  Maverick created our first multi-floor building, following component length restrictions.  We retained this model to build upon in our next class.

Brennan described a disc-within-a-circle system to isolate our building from the shaking ground.  I sketched from his description.  He committed to fabricating this before the next class because he did not have the tools or materials to do so in class.



2015 Feb 26

Maverick tests load bolts in cardboard flooringBrennans model of shock absorberNathanael drawing lines to cutagenda and mathMaverick tested load bolts on the cardboard that we plan to use as flooring.  He found no visible flexing, suggesting that placement near or distant from supports won’t affect flooring.  Placement may, however, affect building resonance and stability.

Brennan mocked up a horizontal shock absorber that he imagined.  It comprises a horizontal disc that can slide wihtiin alarger circle.  The disc would support the building and the circle would be mounted on the foundation. He has more modeling to do before we can test how well it might work.

Nathanael cut cardboard for structural elements within the size restrictions of the Tech Challenge rules, mocking up new building designs.  We all cut squares out of a giant cardboard box that Maverick brought to class. We will figure out how to attach these to structural elements for our building.

Discussion of a Science & Engineering Fair project about capturing energy from kicking a soccer ball led to the very useful technique of “dimensional analysis”.  We used it to figure out the total number of kicks a soccer ball sustains in a game if each of 20 players kicks an average of 12 times per game. Our dry erase board shows how the units of measure cancel when multiplying kicks/player x players. We implied the units of “game”.


2015 Feb 19

Nathanael building slow motion recording of impact 1 Tslow motion recording of impact 2he team tested resonance of a building design by striking the building with a toy sword while recording in slow-motion with an iPad.  Outside of class, students will seek parental permission to use YouTube so they can share this video.  Next up: analyzing the video to guide our designs.

The team considered splitting into two, with one focusing on taking the building apart and reassembling it for the competition and the other team focusing on making the building resist falling down when shaken.  Discussion included the difficulty / inefficiency of splitting design constraints between different teams and the competition rules apparently not requiring disassembly. The team concluded that they should maintain a single team.

Maverick brought cardboard and foam corners.  Nathanael brought duct tape.  We used all but the foam corners, as we concluded that they violate competition rules.  They are too large for either the 20″ x 0.5″ x 0.5″ envelope or the 5″ tall x 3″ diameter tube for structural elements.  Flooring need not fit within these dimensions.


2015 Jan 29

materials building models notes ready to shake shaking table

The team brought balsa wood, measured it, and discussed sizing factors (practicing addition of fractions with different denominators).  The competition shake table will move in only one axis, so we discussed axes: x, y, z.  We even introduced the 4th dimension of time, and how it is both similar and different to the physical dimensions.

They came up with three candidates for team name so that Maverick, out sick, could pick one: Nitro Banana, Ow Son of Cow, or Gravity Rex.

We watched a PBS Nova documentary on earthquakes, providing background to our project and emphasizing that resilient buildings may be the best defense against earthquakes.  Quote from the documentary: “Earthquakes don’t kill people; falling buildings do.”

We built test structures with mini-marshmallows and toothpicks.  Then we tested them on a shake table fashioned from a skateboard, peg board, and clamps.  Mini-marshmallows and toothpicks will unlikely be our building materials, so this was to test building geometry.  We were pleasantly surprised how long our structures stood up.  Testing will be harsher once we incorporate the “load” bolts into floors.  For next class, we want cardboard and load bolts so models can be closer to our competition model.


2015 Jan 22

We have a team competing in the Tech Challenge at the Tech Museum of Innovation in San Jose, CA (http://thetechchallenge.thetech.org/).  This year’s challenge is to design and build an earthquake-safe structure.  Lots of rules make for an interesting design challenge.  On April 26, our team’s building will be shaken on a motorized table through three simulated earthquakes.  Points for a team journal documenting our process and for a building that does not fall down (or sway too much or have little floor space).

Here are some of our notes on open questions, evaluating design ideas, and formulas for mechanics of motion:

open questions open questions 2feature evaluation matrix mechanics and machines

Updates on our progress will appear in this posting.

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