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Ascend Consulting Ltd4-9 Mechanical Engineering Building
University of Alberta Edmonton
AB, T6G 2G8
March 9th, 2012
Dr. Dan Sameoto
Assistant Professor5-01LMechanical Engineering,University of Alberta
Dear Dr. Sameoto;
Subject: Spiderman Climbing GearProject Phase 2 Deliverables
Ascend Consulting is pleased to submit the Phase 2 Conceptual Design Report for the SpidermanClimbing Gear project. This report includes the following:
Conceptual Design Description Preliminary Design Costs
Conceptual Design Evaluation Matrix
Revised Project Schedule
Detailed Conceptual Design Drawings
Macro-scale Test Results
Further to your approval and review of the Phase 1 report detailing project deliverables and scope,Ascend Consulting has designed three different conceptual solutions. A detailed description of eachconceptual design, relevant design calculations and drawings are included in the enclosed report.
To date, the conceptual design phase has required a total of 227 hours and a total project cost of $58,000.
This includes labour costs of $56,850 and prototyping costs of $1050 and material testing costs of $100.Phase 3 is estimated to require 179 hours. The final Phase 3 report detailing the chosen design will besubmitted by April 5th, 2012.
Please review the package and do not hesitate to contact me by email atdting@ualberta.ca.Thank you forconsidering Ascend Consulting for this project.
Sincerely,
Darren TingCc:
Dr. Ben Jar, University of AlbertaDr. Yongsheng Ma, University of AlbertaDr. Kajsa Duke, University of AlbertaDr. Jin-Oh Hahn, University of AlbertaDr. Larry W Kostiuk, University of AlbertaDr. Roger W Toogood, University of AlbertaMr. Joel Tannas, Ascend ConsultingMr. Calvin Ng, Ascend ConsultingMr. Ooi Kai Wen, Ascend Consulting
mailto:dting@ualberta.camailto:dting@ualberta.camailto:dting@ualberta.camailto:dting@ualberta.ca8/10/2019 Ph 2 Report NOTT Spiderman Suit (3)
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Executive Summary
The objective of this project is to design a set of climbing gear that uses a dry adhesive provided
by the client to adhere to the wall. The design should be capable of supporting a 150 pound climber and
allow the climber to ascend and descend a 20ft smooth plexiglass wall.
Three conceptual designs were developed:
Concept A: A design which uses a lever mechanism to provide mechanical advantage when
initiating peel (by pulling on flaps).
Concept B: A design that initiates peeling using a user-actuated rod. The rod is constrained
such that it pulls on the flap only when in a certain position.
Concept C: A design that uses segmented plates for increased flexibility when peeling.
The three design concepts were evaluated utilizing a design matrix that may be found in
Appendix I.Ascend Consulting recommends concept B for future development. A macro-scale materialtest of the adhesive was performed to better understand its material properties. An attached report on
the material testing may be found inAppendix VI.
The main determining factors for choosing Concept B were simplicity, cost, and ease of
manufacturing. Very few parts are required for this design, and the ease of fabricating replacement
parts for Concept B was also contributed to its overall score. Additionally, the design of the device
makes premature peel less likely.
For phase 3, detailed calculations will be performed for the chosen design. Design details (such
as exact part sizing and tolerances) will be finalized in Phase 3. This includes a study of deflection and
stress distributions. Prototype construction and testing will be conducted if time permits.The Phase schedule was updated to incorporate a more detailed breakdown of remaining tasks
(found inAppendix IV). The updated estimated hours for Phase 3 are 179 hours, while the total
estimated project cost is $58,000. This includes a labor cost of $56,850, prototyping costs of $1,050, and
material testing costs of $100.
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Table of Contents
Executive Summary ....................................................................................................................................... 2
Table of Contents .......................................................................................................................................... 3
Table of Figures ............................................................................................................................................. 5
Table of Tables .............................................................................................................................................. 6
1.0 Introduction ...................................................................................................................................... 7
2.0 Concept Design A-Lever mechanism ................................................................................................ 8
2.1 Concept A- Hand Gear Application ............................................................................................. 11
2.2 Concept A- Hand Gear Removal ................................................................................................. 12
2.3 Concept A- Foot Gear Application .............................................................................................. 13
2.4 Concept A- Foot Gear Removal ................................................................................................... 143.0 Concept design B-Flap design ......................................................................................................... 15
3.1 Concept B- Hand Gear Application ............................................................................................. 17
3.2 Concept A- Hand Gear Removal ................................................................................................. 18
3.3 Concept B- Foot Gear Application............................................................................................... 19
3.4 Concept B- Foot Gear Removal ................................................................................................... 20
4.0 Concept Design C: Slotted L Bracket ............................................................................................... 21
4.1 Concept C- Hand/Foot Gear Application .................................................................................... 24
4.2 Concept C- Hand/Foot Gear Removal ......................................................................................... 25
5.0 Feasibility Analysis .......................................................................................................................... 26
5.1 Adhesion Ability .......................................................................................................................... 26
5.1.1 Hand Gear ............................................................................................................................... 26
5.1.2 Feet Gear ................................................................................................................................. 26
5.2 Peel Prevention ........................................................................................................................... 26
5.2.1 Hand Gear ............................................................................................................................... 27
5.2.2 Feet Gear ................................................................................................................................. 27
5.3 Peeling initiation ......................................................................................................................... 27
5.3.1 Hand Gear ............................................................................................................................... 27
5.3.2 Feet Gear ................................................................................................................................. 27
5.4 Ergonomics .................................................................................................................................. 28
5.5 Replacing Adhesives .................................................................................................................... 28
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5.6 Manufacturing and Cost ............................................................................................................. 28
5.7 Safety harness ............................................................................................................................. 28
6.0 Project management....................................................................................................................... 29
7.0 Recommendations .......................................................................................................................... 31
References .................................................................................................................................................. 32
Appendix I Updated Design Specification Matrix ............................................................................... I-1
Appendix II Concept Drawings ............................................................................................................ II-1
Appendix III Manufacturing and Cost Estimates ................................................................................. III-1
Appendix IV Project Schedule ............................................................................................................ IV-1
Appendix V Calculations ..................................................................................................................... V-1
Appendix VI Material Testing Procedure ........................................................................................ VII-26
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Table of Figures
Figure 1: Assembly of Concept A hand component. ..................................................................................... 8
Figure 2: Assembly of Concept A foot component ....................................................................................... 9
Figure 3: Application of concept A hand component ................................................................................. 11
Figure 4: Detachment of concept A hand component ............................................................................... 12
Figure 5: Application of concept A foot component ................................................................................... 13
Figure 6: Detachment of concept A foot component ................................................................................. 14
Figure 7: Assembly of concept B hand component .................................................................................... 16
Figure 8: Assembly of concept B foot component ...................................................................................... 16
Figure 9: Application of concept B hand component ................................................................................. 17
Figure 10: Detachment of concept B hand component.............................................................................. 18
Figure 11: Application of concept B foot component ................................................................................. 19
Figure 12: Removal of Concept B foot component ..................................................................................... 20
Figure 13: Assembly of concept C hand component .................................................................................. 21
Figure 14: Assembly of concept C foot component .................................................................................... 22
Figure 15: Application of concept C ............................................................................................................ 24
Figure 16: Detachment of concept C .......................................................................................................... 25
Figure 17: Foam backing for peel prevention ............................................................................................. 27
Figure 18: Man hours distribution by phase ............................................................................................... 29
Figure 19: Project cost by phase ................................................................................................................. 30
Figure III-1: General assembly for replaceable adhesive .......................................................................... III-2
Figure IV-1: Phase 1 project timeline ....................................................................................................... IV-2
Figure IV-2: Phase 2 project timeline ....................................................................................................... IV-3
Figure IV-3: Phase 3 project timeline ....................................................................................................... IV-4Figure V-1: Free body diagram of climber ................................................................................................ V-1
Figure V-2: Equivalent body postures Avalues of (a) 180 (b) 90and (c) 0.......................................... V-2
Figure V-3: Free body diagram of Rod E ................................................................................................... V-4
Figure V-4: Free body diagram of Rod D ................................................................................................... V-4
Figure V-5: Plot of Fayforces versus A...................................................................................................... V-5
Figure V-6: Plot of Faxforces versus A ...................................................................................................... V-6
Figure V-7: Plot of Fbyforces versus A...................................................................................................... V-6
Figure V-8: Plot of Fbxforces versus A ...................................................................................................... V-7
Figure V-9: Plot of Fresultantforces versus ................................................................................................ V-7
Figure V-10: Free body diagram of analysis model ................................................................................... V-9Figure V-11: Plot of LFZ versus A ........................................................................................................... V-11
Figure V-12: Plot of LHZ versus A ........................................................................................................... V-12
Figure V-13: Free body diagram for concept A ....................................................................................... V-16
Figure V-14: Free body diagram for concept B ....................................................................................... V-18
Figure V-15: Free body diagram for concept C ....................................................................................... V-20
Figure V-16: Free body diagram for concept C after peel initiation ....................................................... V-21
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Figure VI-1: SEM image of a typical micro-structured synthetic adhesive ........................................... VII-26
Figure VI-2: General setup of experiment ............................................................................................ VII-27
Figure VI-3: Side view of backed adhesive strip .................................................................................... VII-28
Figure VI-4: Side view of unbacked adhesive strip ............................................................................... VII-28
Figure VI-5: Shear strength versus micro-scale feature size ................................................................. VII-33
Figure VI-6: General experimental setup .............................................................................................. VII-38
Figure VI-7: Peel test sample specimen ................................................................................................ VII-39
Figure VI-8: Shear and normal test sample specimen .......................................................................... VII-39
Figure VI-9: Peel test configuration ...................................................................................................... VII-40
Figure VI-10: Shear test configuration .................................................................................................. VII-40
Table of Tables
Table 1: Manufacturing and cost details for concept designs .................................................................... 28
Table 2: Project time and resource allocation ............................................................................................ 29
Table I-1: Design Matrix Revision Table ...................................................................................................... I-1
Table I-2: Design Importance Legend ......................................................................................................... I-1
Table I-3: Updated Design Specification Matrix ......................................................................................... I-2
Table I-4: Design Matrix Additional Notes .................................................................................................. I-3
Table I-5: Design matrix score reasoning .................................................................................................... I-3
Table III-1: Manufacturing cost breakdown for concept designs ............................................................. III-4
Table III-2: Estimated cost of design component ..................................................................................... III-5
Table VI-1: Adhesive strengths ............................................................................................................. VII-31
Table VI-2: Raw shear test results ......................................................................................................... VII-35
Table VI-3: Raw peel test results ........................................................................................................... VII-35
Word Count : 2447
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1.0Introduction
The clients research on micro-fabrication has resulted in a dry adhesive that can withstand up
to 1MPa in normal force under ideal conditions. Ascend Consulting was requested to develop a design
that can utilize this material to scale a smooth wall and demonstrate its adhesive properties on a largerscale.
The objective is to design a set of climbing gear that allows a 150lbs climber to scale up and
down a 20 feet smooth wall using the provided dry adhesive. The greatest challenge when approaching
this design problem is that the climbing gear should both adhere strongly and detach easily whenever
required. These conflicting requirements serve as the focus for developing feasible conceptual designs.
The dry is strong against normal forces but significantly less so for shear forces. With this in
mind, the client has requested design values of 100kPa normal strength and 20kPa shear strength. The
adhesive is very prone to peeling at the edges. Once peeling is initiated, the adhesive can be removed
with minimal force due to peel propagation.The material properties of this adhesive were translated into several criteria for the design of
the climbing gear. The design should minimize the probability of unwanted peeling.
To detach the climbing gear from the wall, the design should take advantage of the adhesives
weak peel strength. The design should initiate a peeling action when desired to allow premature
detachment of adhesives from the surface. Also, a rigid backing is also required for the climber to apply
a preload to the adhesives. Therefore it is important to note that the design should have the means to
be flexible or rigid when required.
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2.0Concept Design A: Lever Mechanism
Figure 1: Assembly of Concept A hand component.
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Figure 2: Assembly of Concept A foot component
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The following concept design (seeFigure 1)provides the user with a mechanical advantage using
a lever. By using a lever, the force required to initiate peeling of the adhesive can be greatly reduced by
adjusting the levers pivot point. A unique feature of this design is that the user of this design would
push into the wall to initiate peeling and pull out to prevent peeling.
The feet gear design utilizes a simple fixed plate and an angled. This design has a strip offrictional material at the bottom end of the flat plate to initiate peeling. The reason behind this is that
the feet would generate a moment which applies the most inward normal force at the bottom end of
the plate which results in a high frictional resistance. Dry adhesives on the remaining areas of the plate
would resist any remaining shear force and prevent the design from peeling at the top of the plate due
to moment. The friction material at the bottom of section of the feet gear resists shear and provides a
peel interface.
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2.1 Concept A- Hand Gear Application
1
Flaps unlocked
2
Pivot point
3
Figure 3: Application of Concept A Hand Component
Step 1: Initially, the flaps are locked in angled position. The climber applies the main plate to the glass
and pushes into wall to pre-load the adhesives.Step 2: The climber gives the handle a quarter turn twist.
Step 3: The climber pulls away from wall. The pulling motion of the handle causes the lever to push the
flap against the wall. This would apply a pre-load on the flaps dry adhesive fixing the flaps to the wall.
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2.2 Concept A- Hand Gear Removal
2Flaps locked
1
3
Figure 4: Detachment of concept A hand component
Step 1: To detach design, climber gives handle a quarter turn twist and pushes into wallStep 2: Lever would cause flaps to pull away from wall to initiate peeling and the flaps will be locked in
angled position.
Step 3: Climber then pulls away from wall to remove rigid plate and entire design from wall.
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2.3 Concept A- Foot Gear Application
Figure 5: Application of concept A foot component
Step 1: Climber pushes plate against wall to apply a preload.
Step 2: Climber presses heel downwards on platform. Moment is generated on design. Dry adhesives
resist any normal forces at the top generated by the moment (orange arrow). Strong inward normal
force applied by moment onto frictional material for maximum shear resistance (blue arrow). Design isnow fixed to wall. The inward normal force generated by the moment prevents peeling.
1 2
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2.4 Concept A- Foot Gear Removal
Peel Initiation
Figure 6: Detachment of concept A foot component
Step 1: To detach, the climber lifts their heel. The resulting moment pulls frictional material from wall
easily as they dont resist any normal force. Dry adhesives will peel from bottom as plate is removed.
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3.0Concept design B-Flap design
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Figure 7: Assembly of concept B hand component
Figure 8: Assembly of concept B foot component
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Concept design B uses two plates attached via a hinge that allows the user to initiate peeling at
the lower section when removing the gear from the wall. This design uses a slide-able rod that can be
engaged in two positions. One position only loads the main plate, while the other loads the peel plate.
The leg gear comprises a hinged plate and a knee pad for preloading purposes. Similar to the
concept B, The climber will lift his feet to initiate peeling.
3.1 Concept B- Hand Gear Application
1A
1B
View
B
Rod in Engage
Position
Figure 9: Application of concept B hand component
Step 1: Ensure that the slide-able rod is fixed in the position shown in Figure 9.This avoids the climber
from applying a moment that initiates peeling at the lower plate once climber is fully supported.
Step 2 Apply pushes gear into wall to preload adhesives.
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3.2 Concept A- Hand Gear Removal
Figure 10: Detachment of concept B hand component
Step 1: Slide the rod through the sliding slot as shown in 2A ofFigure 10.Step 2: Pull on handle to initiate peeling of lower plate as shown in 2B ofFigure 10.
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3.3 Concept B- Foot Gear Application
Figure 11: Application of concept B foot component
Step 1: The climber pushes against the wall. Initial contact will be between the lower plate and the wall
Step 2: Climber applies preload through the knee pad by pushing leg against the wall. Design is now
fixed to wall.
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3.4 Concept B- Foot Gear Removal
Figure 12: Removal of Concept B foot component
Step 1: To initiate peeling, the climber will lift his heel and generate a moment to pull the frictionalmaterial on the lower plate from the wall. The dry adhesives will peel from the bottom as the plate is
gradually removed.
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4.0Concept Design C: Slotted L Bracket
Figure 13: Assembly of concept C hand component
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Figure 14: Assembly of concept C foot component
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The L-bracket designs main feature is its segmented plates that allow for greater flexibility
during peeling motion. A block acts as a backing to the plates when rigidity is required. The staggered L-
brackets provide users with a mechanical advantage by facilitating a gradual peel. Since this design only
requires an up-down motion, the same concept can be applied for the feet of the climber.
T L bracket peeling design uses segmentation of the gecko material. Separation of the sections
reduces the amount of normal force needed to disengage with the wall, but increases the number of
peel locations.
The different sized L bracket causes the shorter segments to apply a normal force first to
remove each section one at a time. Each individual set of L brackets essentially concentrates the load at
each individual segment before moving onto the next segment.
The drawback to this design is it will only work under almost ideal conditions. With the amount
of moving parts and complexity it is likely that a section will be exposed to an accidental peel.
Thankfully, accidental peeling of one section will not cause the entire device to be removed.
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4.1 Concept C- Hand/Foot Gear Application
1 2
Figure 15: Application of concept C
Step 1: Climber pushes block into wall with their forearm to apply required preload.
Step 2: Climber slides block downwards to lock studs in L-brackets. Note that segmented plate is now
rigid and design is fixed to wall.
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4.2 Concept C- Hand/Foot Gear Removal
1 2
Figure 16: Detachment of concept C
Step 1: Climber slides block upwards.
Step 2: Climber pulls block away from wall. Pulling force is concentrated at the edge and removal of
segmented plate is initiated. This continues along the length of the entire design until entire segmentedplate is separated from wall.
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5.0Feasibility Analysis
A free body diagram force analysis of a climber on the wall was performed (calculations in
7.0Appendix V). Although the existing dimensions for the design are not fixed, the surface area of the
dry adhesive for each design is sufficient to resist the forces exerted by the climber was found to be
0.12m2. All designs were scaled accordingly to reach this value.
5.1 Adhesion Ability
5.1.1 Hand Gear
For the hand component of concept A the two step process of force application could be an
advantage for the climber as a smaller force is required for sufficient preload. However, depending on
the size of the rigid plate and the flaps, this advantage could be miniscule.
For concept B, the climber has to apply a preload to the entire surface area of the adhesive
(including the flap) which could mean a higher force requirement. Higher stress concentrations are
speculated for this design as load application occurs at the edges and not the center of the adhesive
sheet.
For concept C, a similar preload force to concept B is estimated as the force is applied to the
entire adhesive area. Force is applied using the forearm which could be hard for the climber. Stress
concentrations can be minimized provided tolerances on the L-brackets are sufficiently tight.
5.1.2 Feet Gear
The angled design of concept A allows the climber to use their body weight to apply the
required preload to the adhesives. On the other hand, concepts B & C require the climber to apply a
load using their shins which could be potentially awkward or hard to do.
5.2 Peel Prevention
A good measure of the design its ability to apply a preload for the adhesives to stick to the
surface. Although load concentrations cannot be avoided, a rigid backing for all designs can minimize
this effect. Currently, all concept designs can be easily modified to achieve the needed rigidity (which
will be determined in Phase 3).
The size of the rigid plate gives rise to a concern that air pockets might be trapped between the
adhesive and the glass surface during application. These air pockets should be avoided as they provide
an interface for peeling. Therefore an initial force should be applied to the edge of the adhesive before
pushing the gear into the wall.
A feature to prevent peeling is to have the thin layer of soft foam that is countersunk into the
edges of adhesive plates in spots where peeling is not wanted. When applying a preload to the adhesive,
the foam will compress first, applying a preload to the foam before the rest of the plate. When pulling
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outward, the low stiffness of the foam means that less force will be transmitted to the adhesive on the
foam than on the rest of the plate. This ensures that loading is kept to the center of the plate.
Figure 17: Foam backing for peel prevention
5.2.1 Hand Gear
Concept B and C both initiate peeling from the bottom of the design which is ideal as accidental
peel is more likely from the top. Concept A initiates peeling from both sides and peeling could happen
prematurely at the top hinge corners (since the flaps push in).
5.2.2 Feet Gear
Concept A is least likely to peel since the foot placement reduces moment. Concept B does not
avoid moment generation but the lack of edge of loading avoids accidental peel. Concept C is likely to
peel if rigidity is not maintained.
5.3 Peeling initiation
5.3.1 Hand Gear
Concept A uses a lever to give the climber a mechanical advantage. Also, the peel interface is
doubled due to flaps on both sides. Concept B does not have mechanical advantages, but the flaps can
be sized to a desired removal force
Concept Design C would require the climber to exert a relatively high initiation force on each
individual plate to initiate peeling requiring additional effort for gear removal. However, the segmented
plates would reduce the probability of adhesion failure by avoiding unintentional peeling from one plate
from propagating throughout the entire adhesive sheet.
5.3.2 Feet Gear
Depending on the rigidity of Concept A, peeling can be difficult but the ratio between adhesives
and frictional material can be tailored to a specified removal force. Concept B better facilitates removal
as it allows the material to flex. Concept C has a very similar removing system but peeling initiation is
required for each plate making it the hardest to peel.
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5.4 Ergonomics
Concept Cs hand component is strapped to the users forearm, forcing the climbers body to be
closer to the wall increases the application of shear force in the hands. Concept B requires lateral
movement of the forearm to initiate peeling. Concept A however requires more delicate hand control.
Feet components for both concept B and C require the climber to apply a preload using the
shins. This can be difficult when the climber is trying to maintain a distance from the wall surface to
maximize inward force on the feet.
5.5 Replacing Adhesives
Deterioration of the adhesives strength is unavoidable due to contamination and
microstructural damage. Therefore all designs would use detachable metal plates to replace the
adhesives. Details regarding replaceable plates (applicable to all three designs) may be found in
Appendix sectionIII.2.
5.6 Manufacturing and Cost
Concept B has the least components and is simple to assemble. Concept C requires many parts
with tighter tolerances, leading to higher costs. The hand component for Concept A involves many
moving parts. However, the feet component is much simpler.
An analysis of the estimated manufacturing costs of all designs was performed. The
methodology and detailed breakdown are found in Appendix sectionIII.6.Weight estimates were taken
from solid modeling of the concepts (drawing inAppendix II). The final cost and weight estimates are
shown inTable 1.
Table 1: Manufacturing and cost details for concept designs
Design Number of Parts Est. Mass (kg) Est. Mfg. Cost
Hand-A 33 7.9 $700
Hand-B 10 4.6 $325
Hand-C 38 3.0 $650
Feet-A 4 6.9 $200
Feet-B 12 5.5 $200
Feet-C 38 3.5 $650
5.7 Safety harness
From initial inspection, no interference between the designs and standard climbing harness is
anticipated.
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6.0Project management
Actual hours spent for Phase 2 were overestimated by approximately 50 hours. The allocation of
hours on each individual item is where discrepancies occurred. Three items that had significant
discrepancies occurred at Conceptual Design Calculations, Test Material and Conceptual BrainStorming.
The time required for material testing was underestimated due to technical difficulties and
apparatus preparation. Other unexpected issues such as smoothness of the test surface and epoxy
failures extended the time required to successfully complete the material testing process.
Table 2: Project time and resource allocation
Phase Number Baseline Hours Baseline Cost Real Hours Real Cost
Phase 1 90 $8,400 92 $8,280
Phase 2 286 $3,1740 227 $20,430Phase 3 179 $16,710 TBD TBD
Figure 18: Man hours distribution by phase
0 50 100 150 200 250 300 350
Phase 1
Phase 2
Phase 3
Design Poster
Design Conference
Hours
Real Hours
Baseline Hours
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Figure 19: Project cost by phase
The hours spent on the design conference and posters are not billed to the client and therefore
are not included in the cost estimates.
From the issues found in Phase 2, Phase 3 was updated with more detail to determine a more
realistic date of completion. Significant changes include more time to further develop our final design
with the client and the intermediate engineer, to complete calculations, to prepare manufacturing
drawings, and to review final costs. Refer to6.0 for both the most recent schedule and the original
baseline schedule made in phase 1.
0 5000 10000 15000 20000 25000 30000 35000
Phase 1
Phase 2
Phase 3
Hours
Real Cost
Baseline Cost
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7.0Recommendations
Three design concepts were compared in the design evaluation matrix inAppendix I.The Must
Have design conditions were checked on a pass/fail basis to ensure that critical conditions are met
before any further design evaluation is performed. It was found that design concept B best fit the
desired specifications, followed by concept design A and C. Ascend Consulting recommends Design
Concept B for the final design.
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Gecko Climbing Gear Concepts
References
[1] K. Ono, "Contact Mechanics Anlaysis of a rubber on a smooth plate," Proceedings of the ASME/STLE
2009 International Joint Tribology Conference, 2009.
[2] "ANTHROPOMETRY AND BIOMECHANICS," 5th July 2008. [Online]. Available:
http://msis.jsc.nasa.gov/sections/section03.htm. [Accessed 20th February 2012].
[3] D. Sameoto, "Spider-Man" Climbing Gear Project Proposal, Edmonton, Alberta: University of Alberta,
Department of Mechanical Engineering, 2012.
[4] "Ace Hardware," Ace Hardware Corporation, 2012. [Online]. Available:
http://www.acehardware.com/home/index.jsp. [Accessed 13th Fenbruary 2012].
[5] Biomimetic Systems Lab, Dept. of EECS, UC Berkley, 2012. [Online]. Available:
http://robotics.eecs.berkeley.edu/~ronf/Gecko/gecko-compare.html.
[6] M. S. I. Inc., "Metal Supermarkets," 2012. [Online]. Available: http://www.metalsupermarkets.com/.
[Accessed 20th February 2012].
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Phase II Report Appendix I-
Gecko Climbing Gear
Appendix I Updated Design Specification Matrix
This appendix outlines the design specification matrix for the Gecko Climbing Gear Design Project. The matrix presented here has been updated with updated criteria that were found as more was learned about the project. Each
specification is accompanied by a number that describes how important it is to fulfill each criterion. This appendix consists of the following tables:
A legend of the design importance meanings
Table I-2
A design evaluation matrix (Table I-3)
A table of additional notes concerning the design specifications
A table of additional notes concerning the ranking scheme
A revision table of design matrix changes (Table I-1)
Table I-1: Design Matrix Revision TableRev Comments
0 Initial Version
1 Edited to clarify certain requirements
Table I-2: Design Importance Legend
Number Significance
9 to 10 Must meet requirement to the letter, non-negotiable
7 to 8 Must meet the spirit of the requirement
5 to 6 Highly Suggested
3 to 4 Recommended
1 to 2 Nice-to-have
0 Not Significant
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Table I-3: Updated Design Specification MatrixItem Specifications/Requirements Design
ImportanceDesign ALever
Rank Design BRod & Hinge
Rank Design CL-bracket
Rank
Compliance 0-10 Value Compliance 0-10 Value Compliance 0-10 Value
1 Adhesion Ability1.1 Design must support the weight of a 150 lbs climber. Must Have 1.2 Designs adhesive strength should achieve a minimum safety factor of 10. Must Have
1.3* Adhesive normal adhesion strength will be taken as 100kPa for design purposes. Must Have 1.4* Maximum normal force to remove climbing device from a smooth surface should be no more than 15lbf (70N). 9 9.6 86.4 7.3 65.7 1.8 16.21.5* Maximum force to attach climbing device to a smooth surface should be no more than 15lbf (70N). 9 8 72 8 72 5 451.6 3 point contact during climbing is assumed. Weight of climber should be fully supported by 3 individual climbing
gear components.Must Have
1.7 Adhesive shear strength will be taken as a 20kPa unless material testing confirms otherwise. Must Have
2 Material2.1* Design must use the dry adhesive supplied by the client (composed of specially molded ST-1060 polyurethane)
as the sole means of adhering to the wall.Must Have
2.2* Bonding between adhesives and replaceable parts should not fail in normal operation. Must Have
3 Design3.1* Design should not incorporate any external power sources. Must Have 3.2* The design should be easy to clean by the climber while on the wall. 2 3 6 5 10 3.4 6.83.3* Design should have means to change the parts the adhesive material. 0 0 A
a) Hand Gear 6 5 30 5 30 7 42b) Foot Gear 6 8 48 5 30 7 42
3.4 Replacement parts for design should be easy to fabricate and easy to install with basic hand tools.a) Hand Gear 2 3 6 7 14 4 8b) Foot Gear 2 3 6 9 18 4 8
4 Ergonomics4.1 The climbing gear should be easy to grip and control while on the wall 5 5 25 7 35 8 404.2 Design should be easy for the wearer to put on and take off 5 7 35 7 35 7 35
4.3* Maximum width of climbing gear should not exceed 26. Must Have
5 Weight5.1 Total weight should be no more than 11 kg. 6 3.7 22.2 5.4 32.4 8.5 515.2 Heaviest individual climbing gear component should be no more than 3kg. 5 3.8 19 5.4 27 8.6 43
6 Manufacturing6.1 Ease of manufacturing with standard machine shop tools 5 6 30 8 40 3 156.2 Labour hours to attain design prototype shall not exceed 1 week 4 4 16 8 32 3 12
7 Additional Features7.1 Compatibility with climbing harnesses Must Have
8 Costs8.1 Funds for prototype and experimental testing should not exceed $1,000. 4 5.1 20.4 9.4 37.6 3.9 15.6
Totals 422 478.7 379.6
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Table I-4: Design Matrix Additional Notes
*Additional Notes:
1.3 The adhesion strength of 100 KPa does nothave the safety factor of 10 incorporated.
1.4 & 1.5 15 lbs. is the speculated force that the climber can comfortably exert with one hand while climbing.
2.1 The adhesive material has the greatest adhesive strength in the normal direction, and significantly reduced adhesive strength in shear loading. The client has agreed
that a non-adhesive material with a high friction coefficient may be used for resisting shear forces.
2.2 Material testing found that a chemical bond between adhesive sheets and an acrylic plate will be necessary.
3.1 The design must not require any external power sources such as batteries, power cords, compressed air, motors, etc
3.2 The client has communicated that the adhesive materials adhesive strength deteriorates with use due to dust and damage to the microstructures on the materials
surface. It is preferred that the design incorporate away to easily cl ean the material when needed and lengthen the useful life of the material.
3.3 The client has warned that the once the material is chemically bonded to a surface, it is almost impossible to remove it and therefore the surface would have to be
changed out as well.
4.3 This value is based on the humans average shoulder width.
Table I-5: Design matrix score reasoning
Item Design Notes3.3a A Replacing the adhesive means replacing pieces in both the adhesive plate and peel plate.3.3b A The simple foot design with no moving parts makes replacement backings easy to manufacture and install3.3a B Replacing the adhesive means replacing pieces in both the adhesive plate and peel plate.3.3b B Replacing the adhesive means replacing pieces in both the adhesive plate and peel plate.3.3a C The lack of connection between the adhesive plates means that replacement parts are small, simple, and interchangeable.3.3b C The lack of connection between the adhesive plates means that replacement parts are small, simple, and interchangeable.3.2 A The rotating handle and the weight may make the lever design difficult to maneuver. This will make cleaning difficult3.2 B The weight will make the rod & hinge design difficult to maneuver.3.2 C The smaller plates and lower weight make this design easier to maneuver. This makes it easier to clean while on the wall.3.4 A The number of pins and their critical alignment makes maintenance difficult.3.4 B All parts on this design are low precision and have easily accessible bolts. The requirement for a water-jet machine makes replacement parts difficult to obtain.3.4 C The critical alignment of the pins and slots in this design make maintenance tricky. However, many parts are used repeatedly, so replacement parts can be made ahead of
time.4.2 A The rotating handle of this design may make it difficult to hold on to.4.2 B This design is relatively easy to hold on to, but the weight prevents it from getting a higher score.4.3 C The additional arm slot in this design makes it very easy to maintain a grip on.
6.1& 6.2 A The care required when welding aluminum and the slots required in thin bars make this design tricky to manufacture, however the loose tolerances make the overall difficultyaverage.
6.1 & 6.2 B The loose tolerances and simple construction of this design make it very easy to manufacture. The requirement for the use of a water-jet machine prevents it from getting ahigher score.
6.1 & 6.2 C The tight tolerances for the slot profiles and for the plate thickness on this design make it difficult to manufacture, probably requiring advanced techniques.8.1 All Score = 1000$ / Cost * 10; refer toAppendix III for source
1.4 All Score = 70N / Force; refer toAppendix V for source5.1 All Score = 11kg / Total Weight * 10; referAppendix II for source5.2 All Score = 3kg / Total Weight * 10; refer toAppendix II for source
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Phase II Report Appendix II-
Gecko Climbing Gear
Appendix II Concept Drawings
II.1 Concept A Drawings
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II.2 Concept B Drawings
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II.3 Concept C Drawings
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Phase II Report Appendix II-1
Gecko Climbing Gear
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Phase II Report Appendix II-1
Gecko Climbing Gear
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Phase II Report Appendix III-1
Gecko Climbing Gear
Appendix III Manufacturing and Cost Estimates
III.1 Method
The concept drawings focus on communicating function, not on making manufacturable designs. For cost estimates, rough estimates of
the required material profiles were made, and then costs for these base materials were sourced from materials suppliers [1] [2]For certain
suppliers, these costs included the cost of cutting it to the proper size, eliminating the need for labor estimates. For pieces that needed extra
machining, the Mec E machine shop internal labor cost of 20$/hr was used (since the client is a professor at the U of A). Labor hour estimates
were based off group member experience in machining, carpentry, and woodworking. Economies of scale for manufacturing a part repeatedly
were not considered, since this requires a more detailed consideration of manufacturing methods. Supplier quotes were for machining deemed
not necessary until the detailed design stage. Plastics were avoided since these designs are one-off constructions and making plastic molding is
a high-volume manufacturing method.
III.2Adhesive Plates
The adhesive backing plate on al l designs was chosen to be thick aluminum plate. This is so that the adhesive will have a rigid backing.
The thickness of the plate will be revised in the final design, but the plate provides a consistent reference for cost and weight estimates.
Additionally, the adhesive plate will be a combination of a replaceable acrylic plate that the adhesive is bonded to and the rigid backing for extra
stiffness (see [ref: figure]). An area of 0.12m of adhesive was used for sizing the designs. Any design that uses a hinged plate will require milling
in order to countersink the hinge into the plate.
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Phase II Report Appendix III-2
Gecko Climbing Gear
Figure III-1: General assembly for replaceable adhesive
III.3 Design Concept A
The cost estimate for the two feet components was found to be $400, and the cost of two hand components was found to $1600. The
simple design of the feet and extremely loose tolerances mean that they can be manufactured with a cut-and-weld approach. Extra labor time
was allocated given the challenges of welding aluminum. The hand design manufacturing is significantly more involved, requiring milling on all
pieces. Though all the parts are manufacturable from common shapes (plate, round, and angle metal profiles), they all require significant
customization (a.k.a. labor cost).
III.4 Design Concept B
The cost estimate for the two feet components was found to be $400, and the cost of two hand components was found to $650. These
components are built from common metal profiles, with final machining being possible with a drill press or vertical milling machine. The hand
design currently requires square slots, meaning a laser cutter or water-jet machine will be needed. If these slots are not possible, round slots will
be substituted so that a milling machine can be used. This will require the substitution of the square bar with a round bar and some changes to
the handle design. For the feet design, the main challenge is to make sure that both the main adhesive plate and peel plate engage evenly with
the wall (to ensure even loading and to prevent premature peeling). This means that the design will require a way of tuning the range of
motion. This will probably be by using a steel cable and turnbuckle.
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Phase II Report Appendix III-3
Gecko Climbing Gear
III.5 Design Concept C
The cost estimate for the two feet components was found to be $1300, and the cost of two hand components was found to $1300.This
design has a relatively complex set of slots and tabs to initiate peeling. Because of the way they are designed, they will require smaller
tolerances in order to function. This means more engineering time, higher labor costs, and more scrapped parts. Additionally, the segmentation
of the adhesive plates means there are far more parts than the other designs. Although no special tooling is required for the manufacturing
process, this design has a very labor (and cost) intensive manufacturing process.
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Gecko Climbing Gear
III.6 Cost Tables
Table III-1: Manufacturing cost breakdown for concept designs
Concept Description Mfg. Process Mfg.
Cost
Material Profile Material QTY. $/Unit QTY. Cost
Feet-a Adhesive Plate N/A $0 6061 Aluminum 0.25" Plate 260mm x 500mm $52 2 $104
Feet-a Foot Plate Water-Jet $10 6061 Aluminum 0.25" Plate 320mm x 500mm $54 2 $128
Feet-a Support Strips Saw + Weld $30 6061 Aluminum 0.25" x 1" Flat Bar 220mm $10 4 $159
Feet-b Adhesive Plate Milling $20 6061 Aluminum 0.25" Plate 400mm x 350mm $49 2 $138
Feet-b Piano Hinge N/A $2 Stainless Steel N/A 400mm $3 2 $10
Feet-b Peel Plate Milling $20 6061 Aluminum 0.25" Plate 400mm x 125mm $29 2 $99
Feet-b Stop Braces Sawing $5 6061 Aluminum 1"x1"x0.125" Angle 100mm $9 4 $57
Feet-b Foot Blocks Sawing $2 Spruce 2"x4" 1 foot $3 6 $30
Feet-b Wire Brackets Sawing + Drilling $5 6061 Aluminum 1"x1"x0.125" Angle 1" $2 4 $29
Feet-b Steel Cable Cutting & Looping $10 Steel 0.125" Diameter 12" $2 4 $50
Hand-a Adhesive Plate Milling $20 6061 Aluminum 0.25" Plate 400mm x 300mm $49 2 $138
Hand-a Peel Plate Milling $20 6061 Aluminum 0.25" Plate 400mm x 50mm $21 4 $163
Hand-a Pins N/A $1 1018 Steel 3/8" Round 2" $6 16 $112
Hand-a Lever Cross Bar N/A $1 1018 Steel 3/8" Round 10" $10 4 $44
Hand-a Handle Grip Milling $50 6061 Aluminum 0.25" Plate 4" x 3" $21 2 $141
Hand-a Handle Shaft Milling $120 6061 Aluminum 1" Round 4" $13 2 $266
Hand-a Handle Pins Gluing $10 1018 Steel 3/8" Round 4" $6 4 $64
Hand-a Bracket Milling $10 6061 Aluminum 2" x 3" x 0.25" Angle 1" $10 32 $654
Hand-b Main Plate Milling $20 6061 Aluminum 0.25" Plate 340mm x 380mm $52 2 $144
Hand-b Peel Plate Milling $20 6061 Aluminum 0.25" Plate 340mm x 100mm $26 2 $92
Hand-b Slot Bracket Water-Jet $15 6061 Aluminum 3" x 3" x 0.25" 150mm $17 6 $192
Hand-b Handle Water-Jet $15 6061 Aluminum 0.25" Plate 150mm x 120mm $27 2 $84
Hand-b Rod Drilling & Cutting $20 CREW Steel 3/4" x 0.065"
Square Tube
500mm $13 2 $66
Hand-b Stop Pins N/A $10 1018 Steel 1/2" Round 2" $6 4 $64
Hand-b Piano Hinge N/A $2 Stainless Steel N/A 400mm $3 2 $10
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Phase II Report Appendix III-5
Gecko Climbing Gear
Concept Description Mfg. Process Mfg.
Cost
Material Profile Material QTY. $/Unit QTY. Cost
Feet-c Foot Plate Sawing $20 Pine 2"x6" 1ft $5 2 $50
Feet-c Hard Plate Woodworking $30 Pine 1"x6" 8" $4 2 $68
Feet-c Slot Brackets Water-Jet $10 6061 Aluminum 0.25" Plate 2"x3" $5 24 $370
Feet-c Pegs N/A $0 6061 Aluminum 0.5" Round 1" $6 24 $141
Feet-c Piano Hinge N/A $2 Stainless Steel N/A 400mm $3 10 $50
Feet-c Adhesive Plate Water-Jet $15 6061 Aluminum 2" x 0.25" Flat Bar 480mm $18 12 $395
Feet-c Knee Brace Sawing $10 Pine 2"x6" 1ft $5 2 $30
Hand-c Hard Plate Woodworking $30 Pine 1"x6" 8" $4 2 $68
Hand-c Slot Brackets Water-Jet $10 6061 Aluminum 0.25" Plate 2"x3" $5 24 $370
Hand-c Pegs N/A $0 6061 Aluminum 0.5" Round 1" $6 24 $141
Hand-c Piano Hinge N/A $2 Stainless Steel N/A 400mm $3 10 $50
Hand-c Adhesive Plate Water-Jet $15 6061 Aluminum 2" x 0.25" Flat Bar 480mm $18 12 $395
Hand-c Handle Bought $0 Brass Door-Handle 1 $10 2 $20
Hand-c Arm Slot Water-jet $10 6061 Aluminum 0.25" Plate 150mm x 120mm $27 2 $74
Table III-2: Estimated cost of design component
Design # of Parts Estimated CostFeet-a 8 $391
Feet-b 24 $412
Feet-c 76 $1104
Hand-a 66 $1581
Hand-b 20 $652
Hand-c 76 $1118
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Phase II Report Appendix IV-1
Gecko Climbing Gear
Appendix IV Project Schedule
Ascend Consulting has developed a baseline schedule plan and to track project progress. A commercial project planning software (Liquid
Planner 2011) is being used to monitor project progress and allocate tasks to team members. A timeline was proposed with the aim of having a
functional prototype built within 4 months as the best case scenario. The schedule is accessible by all team members and a project supervisor
(Dr. Ben Jar) for tracking project progress.
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Figure IV-1: Phase 1 project timeline
No items are shown as no items
remain to be completed
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Phase II Report Appendix IV-3
Gecko Climbing Gear
Figure IV-2: Phase 2 project timeline
No items are shown as no items
remain to be completed
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Phase II Report Appendix IV-4
Gecko Climbing Gear
Figure IV-3: Phase 3 project timeline
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Phase II Report Appendix V-1
Gecko Climbing Gear
Appendix V Calculations
V.1 Free body analysis of climber
For this analysis, the human body is approximated as a two rigid member linkage with the hands
and feet of the climber modeled as pin connections to a rigid vertical wall. The client has agreed that
performing a quasi-static analysis is reasonable for this design. Therefore this analysis assumes that
climbing movements are performed as sufficiently slow speeds such that inertial forces are negligible.
The objective is to determine the vertical and normal forces exerted by the climbers hands and feet
during climbing.
A
B
C
Fax
Fw
Fby
Fbx
L1
L2
L3
L4
Fay
G
x
y
Rod D
Rod E
Vertical
Normal
Figure V-1: Free body diagram of climber
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Phase II Report Appendix V-2
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V.1.1 Assumptions
1. The human body can be approximated as a two rigid member linkage pivoted at points A and B
which corresponds to the climbers wrist and ankles respectively. Point C is equivalent to the
shoulder of the climber.
2. The weight of the average male climber is approximately 700N.
3. The coefficient of friction for rubber on glass is 2 [1].
4. The model is quasi-static, i.e. inertial effects are negligible.
5. Length of rigid members is equal to body measurements of an average human male. Values are
obtained from the NASA website for anthropometry and biomechanics [2].
6. The comfortable working range for is 45
0
to90
0
. Further explanation as follows.
A
B
C
A
B
C
A
B
C
Rod D
Rod E Rod E Rod E
Rod D
Rod D
(a) (b) (c)
Figure V-2: Equivalent body postures Avalues of (a) 180 (b) 90and (c) 0
Figure 2 is a clear depiction of how affects the free body model of the analysis. By initial
speculation, it was clear that case (a) and case (b) are both unrealistic models and therefore excluded
from further analysis. Preliminary calculations have also proved that values above 450resulted in
large shear forces that cannot be resisted by adhesives of a practical area size.
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Phase II Report Appendix V-3
Gecko Climbing Gear
V.1.2 Calculations
General dimensions (refer toFigure V-1)
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Fby
Fbx
Fw
L3
L2
c
Fint
B
Rod E
Figure V-3: Free body diagram of Rod E
Figure V-4: Free body diagram of Rod D
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Phase II Report Appendix V-5
Gecko Climbing Gear
V.1.3 Result
Fay(N)
A (radians)0.8 1 1.2 1.4
0
50
100
150
200
Figure V-5: Plot of Fayforces versus A
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Phase II Report Appendix V-6
Gecko Climbing Gear
Fax(N)
A (radians)0.8 1 1.2 1.4
400
300
200
100
0
100
Figure V-6: Plot of Faxforces versus A
Fby (N)
A (radians)
0.8 1 1.2 1.4500
600
700
Figure V-7: Plot of Fbyforces versus A
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Phase II Report Appendix V-7
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Fbx (N)
A (radians)0.8 1 1.2 1.4
10 0
0
10 0
20 0
30 0
40 0
Figure V-8: Plot of Fbxforces versus A
A portion of shear force is resisted by frictional material (assumption 3):
= 2
Fresultant (N)
A (radians)
0.8 1 1 .2 1.40
50 0
1 103
1.5 103
Figure V-9: Plot of Fresultantforces versus
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Phase II Report Appendix V-8
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V.1.4 Conclusion
This analysis has revealed that the climbers hands exert a considerably smaller magnitude of
force than the feet. FromFigure V-5 andFigure V-6,the maximum force exerted by the hands in positive
normal direction is found to be slightly above 300 N. A maximum downward vertical force was
determined to be 150 N. On the other hand, the climbers feet exert a maximum of 150 N normal forceinto the wall and a downward shear force of 700 N. Fortunately, a portion of the feets shear force is
resisted by friction due to the normal force acting into the wall.
A general trend was observed from this analysis. Shear force was found to increase at the hands
but decrease at the feet as the overall distance of the climbers body from the wall surface was
increased. However the reverse was noticed for the feet. Since in a typical climbing situation, the pushes
for vertical ascend is mostly fueled by the feet, shear should be avoided in the hands and maximized at
the feet. This is also consistent with the clients request. Therefore it can be concluded that the climber
should try to maintain a maximum distance from the wall to achieve this ideal scenario.
It is also very important to note that shear resistance due to friction played an immense role in
supporting the climber. Without it, the size of required adhesives would be immense and unrealistic due
to its size. The possibility of the design impeding the movement of the climber and interfering with
standard climbing safety equipment would also be incredibly high. Similarly, the climber should try to
maintain a maximum distance from the wall to maximize normal force (and therefore friction force) on
the feet.
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Phase II Report Appendix V-9
Gecko Climbing Gear
V.2 Force equilibrium for three point contact
This analysis aims to determine the magnitude of lateral forces (z-direction) as shown inFigure
V-10.As soon as a climber detaches one component of the climbing gear, lateral forces would develop
as the remaining gears re-balance the moment of the climber. The objective is to investigate the
significance of lateral forces and their effects on the loading of the design and the adhesive.
V.2.1 Assumptions
1. The climber is modeled as a rigid body supported by a maximum of four pin connections.
2. Lateral load is distributed evenly between hands and feet.
3. The weight of the average male climber is approximately 700N.
4. The model is quasi-static, i.e. inertial effects are negligible.
5. Dimensions for model correspond to body measurements of the average human male [2].
6. Climbers hands are at equal height. Similarly, climbers feet are at equal height.
Figure V-10: Free body diagram of analysis model
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V.2.2 Calculations
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Scenario 1: Climber releases right foot.
Conditions: No loading on the right foot, i.e.: RFX=RFY=RFZ=0
V.2.3 Results
LFZ(N)
A (radians)
0.8 1 1.2 1.40
100
200
Figure V-11: Plot of LFZ versus A
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Phase II Report Appendix V-12
Gecko Climbing Gear
Scenario 2: Climber releases right hand.
Conditions: No loading on the right hand, i.e.: RHX=RHY=RHZ=0. Conditions below were inputted into
MathCad to simulate the climbers right foot being not attached to the wall.
V.2.4 Results
LHZ(N)
A (radians)
0.8 1 1.2 1.4
40
20
0
20
Figure V-12: Plot of LHZ versus A
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V.2.5 Conclusion
The maximum lateral forces acting at the climbers hands and feet are 20 N and 150 N
respectively. These forces are significantly smaller than forces found in the x- and y- direction. The gain
from counteracting this force is minimal and therefore it is negligible. A higher lateral force was found
for the legs and therefore greater adhesive strength could be required for the feets climbing gear.
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V.3 Minimum required contact area
The aim of this analysis is to determine the minimum area of adhesives required for the design.
This analysis was performd for the feet as it exerts the largest and therefore the critical load in the
design.. This calculation includes rubber as a high frictional material to utilize the climbers normal
reaction force to minimize the total load experienced by the feet.
V.3.1 Assumptions
1. Material properties used are obtained from material tests and are as follows:
Peel strength = 0.2
Initiation Force per length of adhesive = 1
Normal strength of adhesive = 100
Shear strength of adhesive = 20
V.3.2 Calculations
The maximum force resisted by adhesives was found to be:
V.3.3 Conclusion
The minimum adhesive area required for the feet is 0.1252. Note that this value is obtained by
assuming the adhesive will be loaded entirely in shear which was considered the worst case scenario.
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V.4 Concept Design Calculations
The aim is to estimate the force required to initiate peeling relative to the three concept
designs.
V.4.1 Assumptions
1. The initiation force required to initiate peeling is linearly dependent on the adhesives
peel length
2. Peel initiation strength, = 1
(estimated from material testing found in
Appendix VI)
3. The peel strength of the adhesive after initiation has occurred is linearly dependent on
the adhesive peel length.
4. Peel strength, = 0.2
(estimated from material testing found inAppendix VI )
5. The normal and shear strength of the adhesives are taken to be 100 kPa and 20 kPa
respectively.
6. Dimensions for concept design are equal to preliminary dimensions from design concept
models.
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Phase II Report Appendix V-16
Gecko Climbing Gear
V.5 Concept Design A: Lever concept calculations
La
Fremoval
Pivoted rod
member
hinged flap plate
Lb
Adhesive layer
Fflap
Om
Finitiation
Figure V-13: Free body diagram for concept A
General Dimensions (Refer toFigure V-13)
Pivoted rod member angle
Length of flap plate
Peel length
M 0:=
Lpeel 5c:=
Lflap 25c:=
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V.5.1 Calculations
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Phase II Report Appendix V-18
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V.5.2 Concept Design B- Rod and hinge calculation
Figure V-14: Free body diagram for concept B
General Dimensions (Refer toFigure V-14)
X
La Lb Lc
Finitiation
Fflap
Fremoval /2 Fremoval /2
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V.5.3 Calculations
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Phase II Report Appendix V-20
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V.6 Concept Design C- L-bracket design
Figure V-15: Free body diagram for concept C
General Dimensions (Refer toFigure V-15)
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Phase II Report Appendix V-21
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V.6.1 Calculations
Figure V-16: Free body diagram for concept C after peel initiation
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V.7 Concept Design Conclusion
Concept Design A
Lever Mechanism
Concept Design B
Rod and Hinge
Concept Design C
L-bracket
Maximum removal
force (N)7.31 9.56 65.22
These forces contribute to relevant scorings for each design in the design matrix found inAppendix I.
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Phase II Report Appendix VI-23
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Appendix VIAverage human body lengths
The 50thpercentile was taken to be a reasonable measure of an average male climbers body
proportions. All of the following body size charts came from reference [2].
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Phase II Report Appendix VI-25
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Phase II Report Appendix VII-26
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Appendix VIIMaterial Testing Procedure
VII.1Introduction
As part of the design project for a set of climbing gear, the adhesive properties of the
employed biomimetic material are required. The adhesive properties of this material change
significantly with the direction of applied forces. Also, the adhesive strength of the material
degrades as it picks up contaminants and with repeated usage. In order to gain a better
understanding of how the material will behave when it is used in the climbing gear, the following
tests were designed to test the adhesive strength of the material in normal, shear, and peel loading
when they have been applied under less than ideal conditions.
Objective:To determine the normal, shear, and peel strengths of an adhesive sheet under
non-ideal conditions after repeated usage.
Figure VI-1: SEM image of a typical micro-structured synthetic adhesive
VII.2Required Materials
A set of laboratory weights (ranging from 10g to 3kg)
Acrylic block as shown in AppendixVI.9 A bubble level or equivalent
Two C-clamps
Metallic bar as a spacer
Selected samples of the adhesive sheets with and without acrylic backing in rectangular strips of
2cm x 1cm
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VII.3Assembly
Adhesive Backing
Block
C-Clamps
Table
Acrylic
Block
Metal bar
Weights
Table Vise
Figure VI-2: General setup of experiment
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Weight
Adhesive Pad
Acrylic layer (pre-
attached, 1mm thick)
Glue ( epoxy or
alternative)
Aluminium Backing Block
Figure VI-3: Side view of backed adhesive strip
Unbacked
Adhesive PadSquare Tubing
2cm
Epoxy
Figure VI-4: Side view of unbacked adhesive strip
VII.4Procedure
Although the design construction of the adhesive material is an advanced and delicate
process, the macroscale testing ignores much of the finer detail. This is to more closely approximate
the experience of the climber, who will not have the opportunity to ensure exact conditions are
followed.
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VII.4.1General Setup
1. The Polyethylene (PE) film that is attached to the acrylic backed samples was removed.
This step is crucial as the PE film has a low bonding surface energy which prevents
epoxy from properly bonding to the surface.
2. Epoxy was applied to backed samples and aluminum blocks were attached. Epoxy was
applied to one end of un-backed samples and square tubing was attached. The epoxy
was then left to dry for one hour to ensure maximum strength.
3. The samples were trimmed to obtain desired 2cm x 1cm test samples.
4. Thirty pound test fishing lines were run through the aluminum blocks and square
tubing. Figure VI-7 shows samples ready for testing.
VII.4.2Shear Loading Test
5. Acrylic surface was wiped down with ethanol and left to dry.
6. A backed sample was attached to the vertical side (A) of the acrylic block. The sample
was preloaded with a 5 kg weight.
7. Acrylic block was clamped to metal bar with c-clamps and a bubble level was used to
ensure that the acrylic block is properly aligned.
8. Weights were attached to the string slowly to avoid impulse loading.
9. Applied weight was increased until adhesive separates from acrylic block. This final
weight was recorded.
10.Steps 4 through 8 were repeated for remaining samples.
VII.4.3Normal Loading Test11.Acrylic surface was wiped down with ethanol and left to dry.
12.A backed sample was attached to the normal side (B) of the acrylic block. The sample
was preloaded with a 5 kg weight.
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13.Acrylic block was clamped to metal bar with c-clamps and a bubble level was used to
ensure that the acrylic block is properly aligned.
14.Weights were attached to the string slowly to avoid impulse loading.
15.Applied weight was increased until adhesive separates from acrylic block. This final
weight was recorded.
16.Steps 10 through 14 were repeated for remaining samples.
VII.4.4Peel Test
17.Acrylic surface was wiped down with ethanol and left to dry.
18.An unbacked sample was attached to the inclined side (C) of the acrylic block with the
orientation shown inFigure VI-4.The sample was then preloaded manually.
19.Acrylic block was clamped to metal bar with c-clamps and a bubble level was used to
ensure that the acrylic block is properly aligned.
20.Weights were attached to the string slowly to avoid impulse loading.
21.Applied weight was increased until sample begins peeling. This weight was recorded.
22.Weight was removed and reapplied slowly. Weight was increased until a peeling
interface of constant velocity is achieved. This weight was recorded.
23.Steps 16 through 20 were repeated for remaining samples.
VII.4.5Normal Preload Test
24.Gently place the aluminum block backed adhesive specimen on the appropriate surface
of the acrylic block.
25.Gently place a 5g weight on the aluminum block and wait for approximately 30 s or until
adhesives are evenly preloaded.
26.Gently attach the acrylic block to the metal spacer and ensure that it is leveled using a C-
clamp.
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27.Gently attach weights to the string attached to the aluminum block until failure. Record
the weight at failure.
28.Repeat the test with increasing preload weights with an initial increment and doubling
the weight increment for each subsequent test to determine the maximum preload for
which no further increase in normal stress is observed.
VII.5Results and Discussion
Table VI-1: Adhesive strengths
Microscale
Feature Size (m)Average 45
o
Peel Force (N)Average fai lu re
shear stress (kPa)
16 0.22 88.3
24 0.20 119.732 0.15 102.8
40 0.20 90.3
Table VI-1 summarizes macroscale test results for pure shear and 45opeel tests conducted.
VII.5.1Peel Test
Table 1 summarizes the force required for continuous peeling from an existing peel interface. It
was observed that for all samples an initial force of 1N was required to initiate the peeling of the
adhesive strip. The test results indicate that there is no significant variation in the normal and tangential
peeling strength of the adhesive with the microscale feature sizes tested. This was expected by the
client as the adhesive was tested on a flat surface, and smaller features are only more helpful on curved
surfaces. However, the experiment used weights with a smallest increment of 10g, and this may have
been too large to accurately test the peel strength. A smaller weight with a finer resolution may have
given better results. Alternately, the materials engineering department has recently acquired a peel
strength testing machine. Though access to the machine is very limited right now, later tests may be
able to make use of this device.
VII.5.2Shear Test
Table VI-1 summarizes pure shear test results with varying microscale feature size. On average all
adhesive samples exceeded the initialed assumed shear strength value of 20kPa. Dry adhesives with
microscale feature size of 24 microns displayed higher failure shear stress values in comparison to the
other adhesives. However, no conclusions on the samples shear strength should be drawn due to the
low precision of shear strength obtained. Even so, it can be concluded that shear strength of 20 kPa for
the adhesive is a valid assumption as none of the samples failed below that threshold.
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One major setback was discovered which jeopardized the performance of this test. During the
test, many of the samples separated from the aluminum backing either before or during the test. It was
later discovered that the polyethylene protective sheet on the acrylic backing of the adhesive was not
removed before epoxy was applied. Therefore the shear test for many of the samples could not be
performed.
VII.6Normal Test
A normal test was attempted but no results were obtained due to failure of the epoxy. From the
shear test, it was speculated that the aluminum backings would be separated from the adhesive backing
before a maximum supported weight can be obtained. However, the assumed value of 100 kPa for
normal strength can be considered safe as this value was provided based on extensive normal strength
tests performed by the client.
VII.7Improvements
It was found that just removing the protective polyethylene layer was insufficient in preventing
the epoxy between the backed adhesive and the aluminum blocks from yielding. The client suggestedreplacing the aluminum backing blocks with acrylic ones. These acrylic blocks can then be strongly
bonded to the adhesive backing using acetone as a solvent. The client warned that a white residue could
remain but should not have any impact on the experiment. Another suggested method was to use a hot
gun to melt the block and the adhesive backing together. This method however raises concern of how
the heat would affect the adhesive.
Due to the environment in which this experiment was performed, the samples were exposed to a
lot of handling and dust. A lint roller proved somewhat effective but still does not remove all
accumulated contaminants on the adhesive. It was noted that further test should require greater
caution in handling the adhesives. The adhesives could always be attached to a clean sheet of
polyethylene until tests are ready to be performed.
The use of epoxy in this experiment could have also impacted the results of this experiment. Due
to the small size of the adhesive samples, epoxy frequently overran the edges of the sample and
contaminated the edges of the adhesive samples. Therefore for future experiments, care must be taken
to ensure that any bonding agent used does not contaminate the sample.
Another problem noticed during the experiment was the roughness of the test surface. The acrylic
block was machined for surfaces of different orientations and this process left the test surfaces
extremely rough. Initial attempts revealed that the adhesives were not sticking to the rough surfaces at
all. These surfaces were ground down to a 0.5 micrometer surface roughness (native acrylic has aroughness of 0.3 micrometers). Even so, there was concern that constant roughness cannot be assured
for all surfaces which might lead to deviations between strengths obtained from different surfaces. It
was therefore suggested that glass slides should be acquired and attached to the test surfaces of the
acrylic block as a solution to this problem.
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Figure VI-5: Shear strength versus micro-scale feature size
0
20
40
60
80
100
120
140
16 24 32 40
FailureS
tress
(k
Pa)
Micro-scale Feature Size (m)
Average of Failure
StressStdDev of Failure Stress
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VII.8Calculations
VII.8.1Nomenclature
Cross sectional area of adhesive strip (2)
Failure shear load ()
Failure shear stress (kPa)
, Normal peeling force ()
, Tangential peeling force (kPa)
Total peeling force ()
Peel angle (degrees)
Mass of weight required for constant peeling (kg)
g gravitational acceleration (9.81
)
VII.8.2Sample Shear Test Calculations
For sample 1, the failure weight when the adhesives are loaded in pure shear was 1820g.
Failure shear stress, =
=1.820 9.81
(0.01 0.02)1
1
1
1000
= 89.27
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VII.8.3Results
Table VI-2: Raw shear test results
Sample
#