BOOMILEVER 2020 - NC Science Olympiad
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BOOMILEVER 2020 Think of a boomilever as a horizontal crane arm attached to a wall. The “holdback” for the load is a single mounting hook high on the wall, and the crane arm bears against the wall at one or more lower points. The load is suspended near the far end of the boom. (note: the pictured boom will not meet the 2020 construction and competition rules
BOOMILEVER 2020
This is an Experimental Engineering event that places maximum emphasis
on innovative design, efficient use of materials, and quality of
construction
– Coaches primary job is to help students understand the expectations
of the event; ALL competitors should arrive at competitions with
TIER 1 boomilevers that can meet construction and competition
requirements.
– Coaches primary job is to help students understand the experimental
process; students should be encouraged to push the design envelope
and learn what works through repeated structural failures, design
revisions, and retests.
– Student experimentation with different designs, material selection,
and construction techniques will result in gains in efficiency, and thus
improved results.
– Experimental process. Student design, photographs, video and testing
data records help document sequential boomilever designs, failure
modes and improved results.
UNDERSTANDING THE BOOMILEVER EVENT
BOOMILEVER 2020
SIGNIFICANT 2020 RULES
Materials …
No manufactured composites, plies or laminates, bamboo or paper products
No size limit on materials cross section
Construction …
Must be a single structure with NO separate or detachable pieces
Must be long enough to suspend load between 40cm and 45cm from wall
Contact DEPTH LINE is 20cm for Division B and 15cm for Division C
Contact WIDTH LINES are 4cm right & left of the centerline (@ hook)
Scoring …
A maximum load of 15,000 grams (15 kg) is used for score calculations
A 5,000g (5kg) BONUS is awarded for holding the entire 15 kg load
TIER 2 is for competition or construction violations & it will hold a load
TIER 3 if the boomilever cannot be loaded (will not hold block & chain)
1st tiebreaker is the estimated load score
BOOMILEVER 2020
Scoring Tiers …
Tier 1 boomilevers have NO violations AND can be tested (hold at
least the loading block & chain
Tier 2 boomilevers have CONSTRUCTION and/or COMPETITION
violations AND can hold a (any) load.
A 5,000g (5kg) BONUS will be added to the load supported for
boomilevers that support 15kg
SCORE for Tiers 1&2 = (Load held in grams + BONUS) / mass of boom in
grams
Tier 3 boomilevers are UNABLE TO BE LOADED / CAN’T BE TESTED.
Tier 1 boomilevers are ranked by score, and beat ALL Tier 2 & 3 booms.
Tier 2 boomilevers are ranked by score, and beat ALL Tier 3 booms.
Tier 3 boomilevers are ranked by closest estimate, then by lowest mass.
UNDERSTANDING THE BOOMILEVER EVENT
BOOMILEVER 2020
Photos of mounting hook
installed on wall
Photo of testing wall mounted on sand loading device (breaker)
2020 rules have only ONE mounting hook
Top of horizontal tape lines identify the Contact Depths for C
(upper) and B (lower)
Vertical blue tape area lies within the CONTACT WIDTH
LINES (a new exclusion zone, where the boomilever can’t
touch the Testing Wall either before, nor throughout testing)
UNDERSTANDING THE BOOMILEVER EVENT
BOOMILEVER 2020
2020 rules have only ONE mounting hook for both Div B & C
Examples of successful designs for “holdbacks” that work with the single “Mounting Hook”.
Note that the hook is not disassembled during the boomilever setup for testing.
The boomilever “holdback” slips easily in the gap between the hook and the wall, and resists
the load by pulling on the curved part of the hook.
UNDERSTANDING THE BOOMILEVER EVENT
BOOMILEVER 2020
2020 rules have only
ONE mounting hook
Top of the horizontal lines
lines identify the Contact
Depths for C (15cm,
upper) and B (20cm,
lower)
Vertical blue tape area
lies within the
CONTACT WIDTH
LINES (a new exclusion
zone, where the
boomilever can’t touch
the Testing Wall either
before, nor throughout
testing)
UNDERSTANDING THE BOOMILEVER EVENT
BOOMILEVER 2020
• Knowledge base …
– General understanding of loads and forces on booms and
structural girders; and the relative strength of materials
(balsa wood) subjected to tension, compression, shear,
bending & buckling loads
– Girder and truss designs for efficient, LIGHTWEIGHT load
bearing structures; and how girders and trusses members are
loaded (compression, tension); TRIANGLES for stiff and
strong structures
– Construction & gluing techniques; the importance of precise
dimensions and balanced designs to resist vertical (gravity)
loads and compressive and tensile loads
– How to conduct Experimental Test Program, analyze failures,
improve “weak” members, and achieve “Predictable” results
UNDERSTANDING THE BOOMILEVER EVENT
BOOMILEVER 2020
“UNDERSTANDING THE 2020 RULES”
Only those boomilevers meeting the construction and competition
specifications will compete for medals. Common mistakes include …
Boomilever LENGTH and structure won’t support the load block assembly so the
centerline of chain hangs between 40cm and 45cm from the testing wall
(paragraphs 3.c)
Boomilever DEPTH exceeds the CONTACT DEPTH LINE where it touches the
testing wall before and/or during testing (paragraph 3.d)
Boomilever touches the TESTING WALL between the (new) CONTACT WIDTH
LINES (paragraphs 3.d and 5.a.v)
… or … USING A PREVIOUS YEAR’S SPECIFICATIONS …
MENTORING THE BOOMILEVER EVENT
BOOMILEVER 2020
“UNDERSTANDING THE 2020 RULES”
EXPERIMENTING (building and breaking boomilevers OR component parts
of boomilevers) is the ONLY reliable approach to achieve high loading
efficiency scores
The 2020 scoring rules give a 5,000g (5kg) BONUS to boomilevers that hold a
minimum of 15kg
A boomilever that will hold substantially more than 15kg has extra weight,and will
lessen the load score (structural efficiency)
BUT, under the 2020 rules, booms holding less than 15kg will be at an even
greater competitive disadvantage (NO 5,000g BONUS).
Learn from your experiment(s) and build a boom STRONG ENOUGH to hold 15kg
and earn the 5,000g BONUS.
ONLY THEN should you build LIGHTER boomilevers to improve your calculated
efficiency score.
MENTORING THE BOOMILEVER EVENTBOOMILEVER 2020
“UNDERSTANDING THE LOADS: BOOMILEVER”
Simple engineering statics and geometric relationships can be used to
approximate the loads that will be experienced in the primary boomilever
members_ (1) the “hook holdback”, (2) the “tension members” and (3) the
“boom truss” (see next slide)
The magnitude of the loads can be understood by calculating the loads
that will be experienced when 15kg is supported.
Students can then design and test individual components to support these
loads without building and testing the entire structure.
Once you are confident that you have adequately designed and built
components that will support the design loads, then put them together
into a complete boomilever and continue testing to optimizing your
structure.
You should not stop until you’re confident you can support 15kg, and earn
the 5kg BONUS.
MENTORING THE BOOMILEVER EVENT‘B’ Division Dimensions & Forces Engineering statics shows that the forces in
members are proportional to the ratios of the
hook lengths of the members.
Use known forces and dimensions for your
BOOMILEVER to calculate approximate
forces in the main structural members.
Length aMENTORING THE BOOMILEVER EVENT
BOOMILEVER 2019
Girder Designs
MENTORING THE BOOMILEVER EVENTBOOMILEVER 2020
SOUND DESIGN FUNDAMENTALS
Gravity acts DOWN, VERTICALLY at the point of the load.
The load will transfer through the boomilever structure to try to pull the
“Mounting Hook” from the wall. Think of pulling a rope. TENSION.
The load will transfer through the boomilever structure to push against the
wall. Think of a tower on its side. COMPRESSION & BENDING
“Triangles” are more rigid than rectangles
ALL compression & bending resisting structures should incorporate diagonal
members. Yours should, too.
Diagonal members should be incorporated in all three planes (x, y, z)
“Truss Beams” or “Laminated Beams” are efficient for bending loads
Place most of the material in these beams along edges
where the maximum loads occur
MAXIMIZE glue joint surface area
Arrange structural members face-to-face for strongest gluing
Liberally use gussets for reinforcement of “butt” joints
Never “hang” a load on a simple “butt” joint
MENTORING THE Inclined BOOMILEVER EVENTSTRENGTH OF MATERIALS AND JOINTS
TYPE OF WOOD …
Balsa is the lightest wood available. Medal winning boomilevers are made from BALSA.
Basswood has a high strength-to-weight ratio, but use it SPARINGLY, if at all.
Spruce may also be available, but is MUCH TOO DENSE.
GLUE JOINTS …
Strong “sticks” but weak joints equals a weak boomilever
Strong glue joints maximize the surface area to be glued
Gussets maximize the “shear bonding area” for glue joints
Glue adds WEIGHT. Excess glue is excess weight … Trim it off
Use “quick-set” glue to build and test designs.
Thin CCA glue runs like water. Use a special TIP to control it DROP by DROP.
DON’T USE GORILLA GLUE.
SIZE OF STRUCTURAL MEMBERS …
Make “Thicker” structural members by gluing thinner sticks together (laminating).
Custom laminating can place the weight (wood) where the greatest stress is.
Cut “sheet” stock to size. A “skin” provides a lot of “directional” strength
There are lots of good glues
Its not so much which type of glue you use, its’ how you
use it
MENTORING THE BOOMILEVER EVENTAlways inspect glue joints !!!
Some students weigh and mark each QUALITY
“stick” to ensure “balanced” structure
CONSTRUCTION
Use a sanding block
NEATNESS REALLY DOES COUNT
Inspect each “stick” for flaws
GLUE WEIGHS MORE THAN BALSA
CUT, DON’T CRUSH BALSA
ONLY NEW EXACTO OR RAZOR BLADES ARE SHARP
A “THIN” GLUE JOINT IS STRONGER THAN A “FAT” ONE
THE WOOD REALLY IS STRONGER THAN THE GLUE (IN TENSION)
DON’T LET “WOOD SHRINKAGE or EXPANSION” CREATE AN “OUT OF
SPECIFICATION” BRIDGE (build it a tad longer, narrower, lower)
THE BOOMILEVER WORKS IN 3-DIMENSIONS
Use triangles to resist loads in each direction
MENTORING THE BOOMILEVER EVENTThe concept of gusset-reinforced joints
MENTORING THE BOOMILEVER EVENT
BOOMILEVER 2020MENTORING THE BOOMILEVER EVENT
EXPERIMENTAL TESTING PROGRAM
WHY ???
Students will load their own boomilevers during competitions
Bottled Sand, Loose Sand, Combination of bottles and loose sand,
Hopper-loading
Students need to be cautious, yet confident.
Need to have done it before.
Testing EARLY will identify your team’s best builder
Encourage students to build boomilevers at home.
Testing to failure will identify design deficiencies
Video recording & slow-mo replay can show failure mode & location
Testing & analysis will identify the weak link in the design
Always improve the weak link in the next design
Always test to destruction !!!!
Otherwise you don’t know how underbuilt (no BONUS) or overbuilt
(AND OVERWEIGHT) a boomilever design is.
MENTORING THE BOOMILEVER EVENTBOOMILEVER 2020
EXPERIENTIAL LEARNING WORKS.
BREAK STICKS/JOINTS BEFORE BREAKING BOOMILEVERS
BREAK “MOUNTING HOOK” CONNECTIONS BEFORE BOOMS
BREAK WHOLE BOOMILEVERS BEFORE COMPETITIONS
STRIVE TO BUILD FOR REPEATABLE RESULTS
EVOLVE DESIGN TO ACHIEVE MINIMUM STRENGTH of 15kg
DOCUMENT YOUR TESTING AND DESIGN EVOLUTION [data
table, photos, videos]
BUILDING & BREAKING IS JUST
TOO MUCH FUN
MENTORING THE BOOMILEVER EVENTBOOMILEVER 2020
Suggested Materials for your BOOMILEVER Team
TESTING SUPPORT CONSTRUCTION TOOLS
Simulated Test Wall (see next slide)
Metric ruler, meter stick & caliper
paragraph 5.a.i
2ftx3ft sheets of masonite, plywood, etc. for
2- 5cmx5cmx2cm loading blocks
cutting & gluing surfaces
Eye bolt, chain & S-hook(s)
Exacto knives (or balsa cutter) COACH CONTROL
2- 5-gallon buckets
Fine sandpaper, sanding block
50 # of dry, white sand
Engineering triangles (for right-angles)
Digital bathroom scale (reading to 0,1 kg)
Thin tip extensions for CCA glue bottles
Digital balance, 0 to 100g, (reading 0.01g)
Saran wrap & wax paper for gluing surface
Bubble level
BOOMILEVER MATERIALS
Balsa sticks_ various dimensions_ square & rectangular x-section_
from 3/16 to 1/32in dimensions
Balsa sheets_ from 3/16 to 1/32 thick, 2-ft long
CCA glue (thin & gap-filling), Insta-cure, Un-cure
Wood glue (yellow type)
MENTORING THE BOOMILEVER EVENTPhoto of simulated testing wall (not using
mounting hook)
MENTORING THE BOOMILEVER EVENTPROTECT THE INVESTMENT
Do not “over-test” the same boomilever.
Boomilevers previously tested to loads nearing the breaking point may
have been damaged.
If you are getting consistent results, the smartest approach may be
to build two identical boomilevers; one for testing to failure, and a
second for the competition.
Stress the “fragility” of the boomilever to the student(s), the
lighter it is, the more easily it can be damaged through mishandling.
The student should do all handling, assembling, and loading,
as it is his/her responsibility.
Even event staff have been known cause damage by mistake.
Plastic & cardboard boxes are great for storage & transport of
boomilevers.
Foam inserts will restrict movements and limit damage from loose
tools and objects inside the box.
MENTORING THE BOOMILEVER EVENTBOOMILEVER 2020
Tips for a COMPETITIVE Boomilever
(1) The Mounting Hook connection is critical, but don’t overbuild it. Build and
break this piece many times as a component, then attach it to your boom
(2) Choose structural members of different x-sections for heavily-loaded and
lightly-loaded uses and locations
(3) Diagonal cross-bracing can be quite thin, but is important. It keeps long,
compressed members from BUCKLING. Diagonals are needed in all 3 axes.
(4) Square & rectangular x-sections of the same area have the same weight,
but the rectangular x-section is stronger if oriented properly
(5) Your stronger structural members should be aligned with the wider edge
resisting the direction it wants to bend
(6) Larger strength members should always have rectangular, never square x-
sections. You can laminate multiple square members to make a rectangular
one
(7) Precision, balanced assembly can allow a good design to EXCEL, whereas a
more haphazard assembly of the same, good design may result in only half
the failure load (and scoring efficiency)
WHAT DO COMPETITIVE BOOMILEVERS look like ?You can also read
