Tower 2018 Division B and C September 2017 to May 2018 - Greg Marconnet Chuck Stachovic Steve Dean Jay Ralph - Wisconsin Science Olympiad
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Tower 2018
Division B and C
September 2017 to May 2018
Greg Marconnet
Chuck Stachovic
Steve Dean
Jay Ralph
October 2017
Questions/Comments? Write gmarconnet@gmail.com 1
Tower Objective
Design and build the lightest
tower to achieve the highest
structural tower efficiency
Tower Efficiency =
mass held by tower /
mass of tower
Bonus points can be obtained by
designing the Tower to span a
29 cm diameter circle
October 2017 2
Structural Efficiency
• Structural Efficiency (SE) is a normalized
measure of how a design and it’s
construction performs in relationship to
its mass
• Weight Lifters can often lift twice their
mass resulting in a SE = 2
• Ants can lift more than 100 times their
mass. SE >100
• A good tower can hold 1,000 times it’s
mass (~15g tower that holds ~15kg) SE
= 1000
• National tower champion may have a SE
of >3,000 (
What is new in 2018? • Transition in tower size. Rule 3.d • Bonus points for designing the Tower to span a 29 cm diameter circle. Rule 3.b. 5,000 g bonus. Rule 6.c • Tie Breaker: Students must predict the Load Held. 4.a.iv October 2017 4
Rules Review
The purpose of the following section is to
help you better understand the rules but
this section does not replace the rules!
In the 2009 Wisconsin state competition, 19% of the
structures did not meet the building rules!
October 2017 5
1. Description Prior to the competition, teams will design and build a Tower meeting requirements specified in these rules to achieve the highest structural efficiency. TEAM OF UP TO: 2 IMPOUND: NO EYE PROTECTION: B MAXIMUM TIME: 6 minutes October 2017 6
2. Event Parameters a. Each team is allowed to enter only one Tower built prior to the competition. b. Team members must wear proper eye protection during the set-up and testing of the Bridge. Teams without eye protection must not test and must be ranked in Tier 4. c. The Event Supervisor must provide all assessment devices, testing apparatus as described in Section 5 October 2017 7
Eye Protection
Excerpt from July 29, 2015 update.
• Competitor/Coach Responsibilities: Competitors are
responsible for providing their own protective eyewear
manufactured to meet the American National Standards Institute
(ANSI) standard applicable at its time of manufacture.
• CATEGORY B
– Impact protection. They provide protection from a high inertia
particle hazard (high mass or velocity)
– ANSI designation/required marking: Z87+
• Note: Prescription glasses must bear the "Z87+" mark to
be used
• Web link: http://www.soinc.org/eye_protection
8
October 2017
3. Construction Parameters
a. The Tower must be a single structure, with no separate or
detachable pieces, constructed of wood and bonded by
adhesive. No other materials are permitted.
i. Wood is defined as the hard-fibrous substance making up the greater part of
the stems, branches, trunks, and roots of trees beneath the bark. Wood does
NOT include: bark, particleboard, wood composites, bamboo or grasses,
paper, commercial plywood, members formed of sawdust and adhesive.
Wood may never be painted, color enhanced, or have preprinted/paper
labels affixed. Ink barcodes or markings from the construction process may be
left on wood.
ii. There are no limits on the cross-sectional sizes of individual pieces of wood.
Wood may be laminated without restriction by the team.
iii. Adhesive is defined as a substance used to join two or more materials
together. Any commercially available adhesive may be used. Adhesives
include, but are not limited to: glue, cement, cyanoacrylate, epoxy, hot melt,
polyurethane and super glues. Adhesive tapes are not allowed.
October 2017 9
3. Construction Parameters b. The Tower must span a 20 cm x 20 cm opening on a Test Base (5.a.) and may be placed on the Test Base surface in any configuration such that the loading chain is suspended within 2.5 cm of the center of the opening in the Test Base. Bonus Points (6.c.) can be obtained by designing the Tower to span a 29-cm diameter circle, centered on the 20 cm x 20 cm opening of the Test Base. c. The Tower must support the Loading Block (5.b.i.) a minimum of 50.0 cm (Division B) or 60.0 cm (Division C) above the Test Base. There is no maximum Tower height. October 2017 10
3. Construction Parameters
d. The portion of the Tower more than 25.0 cm
NEW (Division B) or 20.0 cm (Division C) above the
Test Base must pass through an 8.0 cm
diameter opening or hole (5.f.).
e. The loading point on the Tower must be
constructed to permit placement of the Loading
Block (5.b.i.) and suspended chain (5.b.iii) on and
through the Tower, to support the bucket (5.c.).
f. The Tower must be constructed such that only the
Loading Block (5.b.i.) supports the chain and
bucket.
October 2017 113. Construction Parameters
g. The Tower may not be braced against any edge of the Test Base
(5.a.) for lateral support at any time.
h. No portion of the Tower is allowed to extend below the top
surface of the Test Base (5.a.) prior to testing.
i. Students must be able to answer questions regarding the
design, construction, and operation of the device per the
Building Policy found on www.soinc.org.
October 2017 12Building and Tools Policy
CONSTRUCTED DEVICES
Amended July 20, 2008 - Original Adoption 1986
• The process of design and resultant product is the students’
responsibility. All components must be made by the student or, if
permissible by the event rules, available by purchase. Students will
assemble the device.
• Safety shall be of paramount importance. Students will be
encouraged to use tools and technology within their age-related safety
range. The use of chemicals should also follow age-appropriate use rules.
• Adults may act as facilitators in the building process by asking
questions, offering ideas or suggestions and providing references.
• Event supervisors may extensively question the lead student as to
the design and construction of the device.
• If the students on the device team cannot answer the questions correctly
and/or the coach cannot verify the device was student-built, then the
Event Supervisors have grounds to believe the students did not
design and build the device. The team will be disqualified from the
event and scored accordingly.
https://www.soinc.org/building_tools_policy
October 2017 134.a. Competition Check-in
i. The team will measure the Tower height using provided materials so
the event supervisor can determine if it meets or exceeds the
minimum Tower height (3.c.) in cm to the nearest 0.1 cm.
ii. The team will verify the size restriction (3.d) by passing an 8-cm
diameter circular ring gauge freely over the section of the Tower and
NEW measuring to the point where the ring rests. The ring may not be
forced over any tight spots. If the ring is not level when in the resting
position, the measurement will be to the high point of the ring. The
ring will be removed before testing.
iii. The team will place their Tower on the scale so the event supervisor
can determine the mass, in grams to the nearest 0.01 g.
October 2017 144.a. Competition Check-in
iv. The team must submit their Estimated Load Scored (6.b.) to be used
…
as a tie breaker (6.e.).
v. No alterations, substitutions, or repairs may be made to the Tower
after check-in for competition.
vi. The event supervisor will verify that the combined mass of the
Loading Block Assembly, bucket and sand, is at least 15,100 grams but
no more than 15,200 grams prior to testing.
October 2017 15Check-in Scoring Sheet
The scoring sheet is a Team Number: ___ Team Name: ________________________________________ Division: ________
summary of the rules. It does Student Names (up to 2): _______________________________, _________________________________
3.a.i
4.a.iv
Did you and/or a team member design and build the Tower being tested?
Load Scored Estimate (loading block assembly, bucket, sand) May not exceed 15,000 g
______ Yes _____ No
_ _ _ _ _. g
not replace the rules! If a video is captured do you want a copy? e-mail: _______________________________________________________
Students - Do not write below this linethis line
(Y) (N)
2.b Eye Protection Category B, Impact protection. ANSI: Z87+ (N = Tier 4)
Construction Parameters (Y) (N)
3.a Single Structure constructed of wood, bonded by adhesive
3.c Supports loading block a minimum 50.0 cm (Div. B) or 60 cm (Div. C) above test base
3.b Spans opening of 20 cm x 20 cm and loading chain centered in opening
However, you should review 3.d
3.e, f
3.g
Tower higher than 25.0 cm (Division B) or 20.0 cm (Division C) above the Test Base must
pass through an 8.0 cm diameter circular ring gauge
Accommodates loading block and allows chain to pass thru Tower to support bucket. Only
the loading block supports the chain and bucket
Does not brace against any edge of the Test Base
.
your design with this sheet!
3.h Does not extend below the top surface of the Test Base .
Competition (Y) (N)
4.a.v No alterations, substitutions, storage or repairs made after check-in .
4.b.i Team did not leave event area after check-in or gain outside assistance, materials, or
communication
.
4.b.ii Set-up and completed test in 6 minutes or less .
4.b.iii Team members place tower. Mount loading block, chain and bucket. Adjust tower as
Web links:
necessary before loading sand
4.b.vi Team members load sand and stabilize bucket with stabilizing sticks. Loading continues
until failure or time expires
Measurements (Y) (N)
4.a.iii Mass (grams to the nearest 0.01g) _ _ _._ _ g
https://www.soinc.org/towers-b 6.b
Scoring
Load Scored includes loading block, chain, hooks, eyebolt, wing nut bucket and sand.
May not exceed 15,000 g
_ _ _ _ _. g
(Y) (N)
https://www.soinc.org/towers-c 6.b
6.c
Supports loading block assembly (N = Tier 4)
Load Scored Bonus (5,000 g; 3.b, 4.b.iv Tower Spans 29cm circle for entire test)
________
.
Tier 1: meet all construction parameters/no competition violations
6.d ________
Tier 2: one or more competition violations
Tier 3: with construction violations or both construction and competition violations
Tier 4: unable to be loaded
6.a SCORE = (_________________ + __________________ ) / _________________ = ________
Load Supported (g) Load Scored Bonus (g) Tower Mass (g)
4.b.viii: Failure is defined as the inability of the tower to carry additional load, any part of the load is supported by anything other than the tower.
6.e: Ties are broken: 1. Load Scored estimate (4.a.iv) closest to actual without going over, 2. Lowest Tower mass
- Completed at check-in TowerCheckIn2018DRAFT
October 2017 164.b. Competition Testing
i. Once participants enter the event area to compete, they must not
leave or receive outside assistance, materials, or communication
until they are finished competing.
ii. Participants will have 6 minutes to setup and test their Tower to
maximum load or failure.
iii.The participants must place the Tower on the Test Base and
assemble the Loading Block Assembly and bucket as required to load
the Tower. If necessary, participants may disassemble the Loading
Block Assembly. The bucket must be mounted to allow enough
clearance above the floor for the bucket to tilt or the Tower to
deflect.
October 2017 174.b. Competition Testing
iv. The event supervisor through out testing (e.g., just prior to loading
sand, during loading)will verify that no part of the Tower’s span
touches or is supported within the 29.0 cm diameter circle for the
Tower to qualify for the “Load Scored Bonus".
v. The participants will be allowed to adjust the Tower until they start
loading sand. Once loading of sand has begun, the Tower must not be
further adjusted.
vi. Participants will load the sand into the bucket and be allowed to
safely and effectively stabilize the bucket from movement caused by
sand loading. Direct contact with the bucket by participants is NOT
allowed. Teams choosing to stabilize the bucket must only use the
tips of the bucket stabilization sticks (5.e.)to touch the bucket.
October 2017 184.b. Competition Testing
vii. Loading stops immediately when a failure occurs or when time
expires. The event supervisor will remove any parts of the Tower in
the bucket or any sand added after failure or time expiration.
viii. Towers that fail before supporting 15,000 g will be scored according
to the actual weight supported at time of failure (6.a.), measured to
the nearest gram, or best precision available. Failure is defined as the
inability of the Tower to carry any additional load, or any part of the
load being supported by anything other than the Tower. Incidental
contact by the chain/eyebolt with the Tower is not failure.
ix. At the event supervisor’s discretion, more than one Test Apparatus
may be used.
October 2017 194.b. Competition Testing
x. Teams who wish to file an appeal must leave their Tower with the
event supervisor.
xi. The supervisor will review with the team the data recorded on their
scoresheet.
October 2017 205.a Test Apparatus
The Test Base will be a solid, level
surface with the following
characteristics:
i. be at least 55 cm long x 32 cm
wide, with a 20 cm x 20 cm square
opening at its center 20 cm x
20 cm
ii. have a smooth, hard, low-friction square
opening
surface (e.g. hardwood, metal, 4.b.iv
“Load
Scored
high-pressure plastic laminate) Bonus
” Zone
which is stiff enough that it does
not bend noticeably when loaded 4.b.iv NO “Load Scored Bonus”
Zone within 29 cm diameter circle
iii. have a 29-cm circle drawn on the
surface, centered on the 20 cm x
20 cm square opening
October 2017 215.b. Loading Block Assembly
i. A square Loading Block measuring 5 cm x
5 cm x approximately 2 cm high with a
hole no larger than 8 mm drilled in the
center of the 5 cm x 5 cm faces for a ¼”
threaded [made of any material…
typically wood, plywood, steel or
aluminum]
ii. ¼” threaded eyebolt (1” nominal eye
outside diameter), no longer than 3”, and
a ¼” wing nut.
iii. A chain and S-hook that are suspended
from the Loading Block Assembly.
October 2017 225.c Bucket 5.d Sand c. An approximately five gallon plastic bucket with a handle to be suspended from the chain and hook d. Sand or other clean, dry free-flowing material (hereafter “sand”). Ref: 4.a.vi Combined mass of Loading Block Assembly, bucket and sand: 15.1 to 15.2 kg prior to testing October 2017 23
5.e Bucket Stabilizing Sticks e. Two (2) stabilization sticks, each made up of a piece of ½” dowel approximately 18 inches long with a spring-type door stop screwed into one end. Refer to example on www.soinc.org Direct contact with bucket is not allowed. Students must use stabilization sticks October 2017 24
5.f Circular Ring Gauge f. A circular ring gauge with an inside diameter of 8.0 to 8.1 cm, not weighing more than 10 g, that retains its shape and flatness when handled. See the event page at www.soinc.org for designs. October 2017 25
6. Scoring a. Score = [Load Scored (g) + Load Scored Bonus (g)] / Mass of Tower(g). High score wins. b. The Load Score is the measured load supported, including the Loading Block Assembly, bucket and sand, but may not exceed 15,000 g. The lowest Load Scored is the mass of the Loading Block Assembly. c. Load Scored Bonus: Towers spanning the 29 cm diameter circle receive a 5,000g bonus. No part of the Tower may touch or be supported within the 29 cm circle throughout testing to earn the Bonus Points. October 2017 26
6. Scoring
d. Towers will be placed in four tiers as follows:
i. Tier 1: meeting all the Construction Parameters and no
Competition Violations.
ii. Tier 2: with one or more Competition Violations.
iii. Tier 3: with Construction Violations or both Competition and
Construction Violations.
iv. Tier 4: unable to be loaded for any reason (e.g., cannot
accommodate Loading Block, or failure to wear eye protection),
and will be ranked: 1st-Lowest mass; 2nd-Greatest height.
e. Ties are broken as follows: 1. Estimated Load Scored (4.a.iv.) closest
to, without exceeding, the actual Load Scored (6.b.), 2. Lowest Tower
mass
October 2017 27Test Day
Check-in Set Up Test
• No impound, bring • Follow
your structure stored directions from
safely until the event! your judge.
• Bring Eye Protection!! • Put on Eye
Protection
4) Connect chain to bucket
and confirm chain’s 6) Test
1) Measure tower mass position in center of • Wear Safety Glasses!
stand opening • Load sand
• Stop at full load, when tower
breaks, or 6 minutes expire!
3) Time starts,
place tower on
test stand,
mount loading
block & chain.
2) Confirm tower 5) Confirm tower span
measurements (BONUS) 7) Measure Load Held
28 October 2017Building & Design • It is not the purpose of this document to provide design specifics. It is your structure, not ours! • Teams should do some research… look in books, search the internet…or just look at some structures in the world around you. • This document will provide some thoughts about general topics related to the building and design of your Structure. • Be creative and have fun!! October 2017 29
The Scientific Process
It’s All About The Discovery!
• Talk with your Physics or
• Read the rules; Re-read the rules TechEd teachers! They will
• Research: books, internet…or have ideas!
just look at some structures. • Draw a design and build
Hypothesize Develop Ideas
“Research & Select” “Design & Build”
• Predict what will
happen
Improve Target 1 cycle Gather Data • Video all tests!
“apply learnings” “Load Test”
per week! Review in slow
motion.
• iPhones work great!
Conclude Evaluate
“What Happened”
• Build an “optimized” tower • Tower Breaks: Where did the tower
break? Why?; Evaluate bonding, wood
failure points
• Holds 15 Kg: Overbuilt? What members
are not needed? Can wood cross section
be smaller? Can design be simplified?
October 2017
Most of all…HAVE FUN!!!
30Steps to FUN and Competitiveness
What Students Can to Achieve! Hypothesize
“Research & Select”
Develop Ideas
“Design & Build”
Improve Gather Data
“apply learnings” “Load Test”
Hypothesize Develop Ideas
“Research & Select” “Design & Build”
Conclude Evaluate
“What Happened”
Improve Gather Data
Hypothesize Develop Ideas “apply learnings” “Load Test”
“Research & Select” “Design & Build”
Hypothesize Develop Ideas Improve Gather Data Conclude Evaluate
“Research & Select” “Design & Build”
“apply learnings” “Load Test” “What Happened”
Hypothesize Develop Ideas
“Research & Select” “Design & Build”
Sub 10 g
Improve Gather Data
“apply learnings” “Load Test”
Conclude Evaluate
Hypothesize Develop Ideas Improve Gather Data
“What Happened”
“Research & Select” “Design & Build”
“apply learnings” “Load Test”
Conclude Evaluate
“What Happened”
Hypothesize Develop Ideas Improve Gather Data
“Research & Select” “Design & Build”
“apply learnings” “Load Test”
Conclude Evaluate
“What Happened”
Improve Gather Data Conclude Evaluate
“apply learnings” “Load Test”
“What Happened”
10 g
Conclude Evaluate
“What Happened”
Perfection!
20 g Design
modeling
Mastery in and
material optimization
Vertical & selection &
symmetrical
30 g
Test setup & bonding
construction
sand
Design addition
refinements
Good
building
Selection techniques
and Sizing of
Follow Rules Materials
October 2017
31Project 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:
• Research
• Design hypothesis
• Design and calculations
• Testing notes, photos and sketches
• Observations and conclusions
• Web references
• http://www.sciencebuddies.org/science-fair-projects/printable_project_logbook.pdf
October 2017 32Suggested Tools
• Rules!!
• Paper to draw plans on or copy of
template
• Wood
–Your Choice! typically balsawood;
some use bass wood
–Available at hobby shops, Ace
Hardware or on-line
• Metric Ruler
–At least 400mm long, metal seems to
work well
• Glue
–Careful not to glue fingers!
• Cutting Tools
–Razor blades or Exacto® knife
–Dremel® tool works well
• Holding Devices
–Pins, clips, and / or clamps – be
careful not to damage wood
• Sand Paper (very fine grains)
• Flat Work Surface
–¾” building insulation cut to size
–Attach plan to board
–Cover with wax paper
• Square
October 2017
33Top Competition Issues • Structure not built to specifications • Not the right size: span too small, not tall enough • Built for wrong division • 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 • Not built keeping loading position in mind (center of opening in base) • Structure did not have enough cross bracing • Poor glue joints October 2017 34
It’s All About Efficiency!
• Efficiency =
Mass Held/Mass of Structure
• Examples -
–20 g structure holds all 15,000 g (15 kg )
15,000/20 = 750
–15 g structure holds 12,000 g (12 kg)
12,000/15 = 800
October 2017 35Bonus Impact
Assume no change in tower mass
+667
+632
October 2017 36What’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 October 2017 37
Where to Start? • Research online – Cantilevers, Bridges, & Trusses • Student drawn rough designs • Discuss what might work • Talk with your Physics Instructors, Tech Ed Instructors October 2017 38
Where to Start?
Mimic Real World Examples; They Are Everywhere!
October 2017
39Where to Start?
Research/Learn from other designs from internet
October 2017
40Web Support
• Science Olympiad main page: http://www.soinc.org/
• Science Olympiad Towers, Division C: http://www.soinc.org/towers_c
• Science Olympiad Towers, Division B: http://www.soinc.org/towers_b
Check out the Student Wiki and Topics forums
• Truss Analysis Application for Tower Design: www.nexote.net
October 2017 41Where to Start?
•Plan to Build >3 Towers for Competitions
(Two Regional Tournaments, and State
Final Tournament)
•Mimic An Existing “Real World” Tower,
with Alterations to Meet Requirements
•Reduce Size of Members to Reduce
Overall Mass
“V” Brace (also Inverted “V”)
“X” Brace “Diamond” Brace
October 2017
Try Any Combinations of Typical Brace Designs
42Building Process
A B C D E F
A. Print out Template PDF Files print options:
B. Cut & Place Template on Layout Board. • Printable on 8.5” x 11” paper (click on the
"poster" button in the pdf print menu)
Cover with waxed paper • Preformatted to Scale (Take to the office
store for Printing)
C. Build Side to Template (Build 2 sides)
D. Prop Up sides on Template
E. Connect Sides with Support Members
43 F. Trim and Level Finished Tower
October 2017Tower Building Considerations • Design • Wood • Glue • Building Tips • Testing Day October 2017 44
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
October 2017 45Tower 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).
October 2017 46Photos from Previous Meets
Heavy and probably Heavy, probably overbuilt Narrow design .
overbuilt
October 2017Photos from Previous Meets
Bent wood on No top connectors .
the 4 corners
…nice
October 2017 48Photos from Previous Meets
Looks legal
October 2017Photos from Previous Meets
Unique design Painting is not allowed Only three sides!
October 2017 50Wood for the Structure • Any type or size of wood may be used. • Bamboo, grasses and paper are not wood and not allowed! • No limit on the cross section size of individual pieces of wood or team made laminations. • Check carefully for grain defects, cuts, chips or other damage • Wood typically has better tensile (pulling) strength than compression strength October 2017 51
Wood for the Structure • Consider laminating thin layers of wood to take advantage of multiple wood grains but remember glue is heavy… unlimited laminations by students is allowed • Check wood pieces for consistency of density… especially balsa. Use wood of higher density in compression applications October 2017 52
Wood for the Structure
Balsa; strongest wood, pound for pound!
Density
(Lbs / cu
Species Ft) Stiffness Bending Compression
Balsa 8 72 70 75
Balsa 10 100 100 100
Balsa 14 156 161 149
Basswood 26 261 288 288
Pine, Spruce 28 230 260 289
Yellow Pine 28 222 277 288
Balsam Fir 30 241 291 341
Black Walnut 37 301 506 512
Oak 48 295 430 366
Hickory 50 379 638 514
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 http://www.go-cl.se/balsa.html
October 2017 53Joints
• Good craftsmanship is critical!
• Cut wood with sharp tools, do not crush wood
• Good joints = joints with no gaps
• Slight roughness of wood glues better than super smooth
Poor Joints Good Joints
Well cut Flat joints
and fit are easy to
joints make
54
October 2017Lap Joint • One of the strongest • Use as often as possible • only as strong as the face of the wood! October 2017 55
Butt Joint • Under Tension will pull apart • Under Compression will stay together October 2017 56
Notched Joint • Stronger than Butt Joint • Less strength than a Lap Joint • Difficult to build October 2017 57
Diagonals and Cross Bracing
• Diagonal Pieces & Cross Bracing are
important!
– Prevents structure from torqueing or
twisting
– Adds additional strength
– Adds additional weight
• If the Cross Braces cross (make an
X), Glue them at the cross
October 2017 59Adhesives
• 3.h.iii Any commercially available adhesive may be used. Types of
Adhesives
– Glue: liquid adhesive obtained by boiling collagenous animal
parts such as bones, hides, and hooves.
– Cement: a synthetic adhesive
– Epoxy: A thermosetting resin capable of forming tight cross-
linked polymer structures.
– Cyanoacrylate: Adhesive made form acrylic polymer. AKA:
Super Glue
– Polyurethane: chemically reactive formulations that may be
one or two part systems and are usually fast curing
– Silicone: adhesive made from silicone.
– Hot Melts: thermoplastic glue
October 2017 60How Does Adhesive Work? • Primarily mechanical bonding between the adhesive and the wood surface occurs when the adhesive works its way into the small pores of the wood. • The adhesive acts as if millions of microscopic fingers are holding the surfaces together. October 2017 61
Adhesives • Read the Material Safety Data Sheet (MSDS)…Safety First • 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 your Adhesive modestly! . . . It is heavy! • Adhesive shelf life is typically only a year or two...use fresh Adhesive October 2017 62
Adhesives
Polyvinyl
GLUE OPTIONS Polyurethane Epoxy Cyanoacrylate
Acetate
Shear Strength
3,600 3,500 2,000 3,000
(psi)
Open Time /
Clamp Time 10 / 60 10 / 120 15 / 45 1/1
(Minutes)
Water based, will Needs moisture Will not fill
Notes Does not shrink
not fill gaps to cure gaps
Health / Safety Wear PPE* Wear PPE* Wear PPE*
Cost ($/oz) (more
stars, higher cost)
Titebond Original,
Gorilla, Elmer’s Gorilla Super,
Elmer’s Carpenter’s, System Three T-88,
Brands Probond, Titebond, Krazy glue, Super
Tacky Formula Industrial G-1
ExcelOne ‘T’, Permabond
Modeling Glue
October 2017 63
*PPE = Personal Protective EquipmentCyanoacrylate Adhesive (CA) • CAs are acid stabilized, single component adhesives that react rapidly at room temperature when contacted with moisture (a weak base). • CA accelerators are solvent based products that increase the cure speed capabilities of CA. They are especially useful in the winter months when the environment is very cold and dry. • For CA’s, fixture time is usually seconds. Full cure is achieved when the adhesive has reached its highest bond strength ~24 hours. October 2017 64
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 typically
October 2017 65Bending 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 October 2017 66
Storage and Transportation
Cardboard box with The ultimate in transport
Styrofoam packing boxes, wooden box with Foam lined box used for a
peanuts works great! carrying handle for a boomilever
(Shown with Elevated tower!! Includes a space
Bridges) for the tower and
protective eye gear
(Cover not shown)
October 2017 67October 2017 68
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