The Pumpkin Sharpshooters
2012-13 CAPSTONE Design Project Final Report
Second Generation Pumpkin Cannon
Jeff Reznicek | Amey Shigrekar | Michael Fujikawa
Project sponsors:
Dr. John Foltz, College of Agricultural and Life Sciences
Dr. Larry Stauffer, College of Engineering
Page |3
1 TABLE OF CONTENTS
2
Executive Summary ............................................................................................................................... 4
3
Background ........................................................................................................................................... 4
4
5
6
3.1
Math Model .................................................................................................................................. 5
3.2
Math Model Results ...................................................................................................................... 6
3.3
Test Firing ...................................................................................................................................... 7
Problem Definition ................................................................................................................................ 7
4.1
Areas for Improvement ................................................................................................................. 7
4.2
Deliverables................................................................................................................................... 9
Concepts Considered and Design Selection .......................................................................................... 9
5.1
Morphological Chart ..................................................................................................................... 9
5.2
Cannon Design ............................................................................................................................ 10
5.3
Tank Material .............................................................................................................................. 11
5.4
Support Structure and Movement .............................................................................................. 12
5.5
Trigger System............................................................................................................................. 14
5.6
Control System ............................................................................................................................ 14
5.7
Base Wad .................................................................................................................................... 15
Design Evaluation and Recommendations ......................................................................................... 16
Appendices ..................................................................................................................................................... i
Appendix A – Final Renderings and Pictures.............................................................................................. i
Appendix B—Project Budget.................................................................................................................... iii
Appendix C—Project Timeline ................................................................................................................. iv
Appendix D—Team Contract .................................................................................................................... v
Appendix E - Math Model ....................................................................................................................... vii
Appendix F – DFMEA ................................................................................................................................ ix
Appendix G – Owner’s Manual ............................................................................................................... xiv
Page |4
2 EXECUTIVE SUMMARY
The Pumpkin Sharpshooters is a team comprised of three Mechanical Engineering seniors collaborating
to construct a second generation pumpkin cannon for Dr. John Foltz, Interim Dean of the College of
Agricultural and Life Sciences. The cannon will be a showpiece at the Clearwater Corn Maze held
annually in Lewiston, Idaho and will be used to generate enthusiasm for the maze and to raise interest in
the subjects of science and engineering. The pumpkin cannon will be operable by the general public and
be able to launch pumpkins, ranging from five to eight inches in diameter, over a distance of 1000 feet.
3 BACKGROUND
In 2011, the College of Agricultural and Life Sciences funded a capstone design team to create a
pumpkin cannon to serve as a source of entertainment at the Clearwater Corn Maze, held every fall in
Lewiston, Idaho.
This team constructed a compressed-air cannon out of PVC-pipe components, incorporating manual
vertical/horizontal aiming controls and a butterfly valve to separate the pressure tank and barrel.
Barrel
Butterfly Valve
Air Tank
2012 First Generation Cannon
In 2012, a second design team was charged with improving upon the previous design in the areas of
safety for the public and operators; ease of use in aiming, charging and firing; and crowd interest and
interaction.
Firing Location
2012 Clearwater Corn Maze
The cannon’s long-term goal is generate interest in science and technology and eventually lead to a
multi-cannon public competition.
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3.1 MATH MODEL
The project math model relies on the isentropic expansion of the air. Air resistance is correlated from
experimental data. The model does not take into account barrel friction, air losses around the sabot, or
irregularities in the shape of the pumpkin.
Given:
Tank Pressure
Tank Volume
Barrel Volume
Outside Pressure
Mass of the
Pumpkin
Angle of the Barrel
Size of the pumpkin
Find:
The distance the pumpkin will travel
The time it will take to get there
How fast it will be going when it hits
Use the work done by the expanding gas to calculate the initial velocity.
Use the size and mass of the pumpkin to determine the effect of wind resistance. The C value is a
function of the shape of the pumpkin correlated from experimental data.
Use the initial velocity and the angle of the barrel to calculate vertical and horizontal displacement at
any given time.
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3.2 MATH MODEL RESULTS
This graph shows angle of the cannon affects the results of the model. It shows that with wind resistance, the optimum angle is
about 36 degrees.
This graph shows the model's predictions with, and without wind resistance. It demonstrates why correctly modeling the
resistance is key to predicting distance.
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3.3 TEST FIRING
Testing the old cannon at the Clearwater Corn Maze gave the team plenty of data that was used to
better predict input variables to hit our target. Unfortunately, after over a hundred firings, the accuracy
was still only 25%.
Some factors the math modeling did not take into account are:
-
Shape of the pumpkin and center of gravity
Moisture inside the barrel
Ambient temperature
Projectile spin
With these results the team concluded that it is not feasible to obtain accurate aiming with a pumpkin. It
is recommended to the client the cannon be used for distance shots, or aiming for larger targets.
4 PROBLEM DEFINITION
4.1 AREAS FOR IMPROVEMENT
4.1.1 Safety
Safety being the top priority of
any design, the cannon
needed to be safe enough to
be operated in public. The
primary safety concerns in the
old cannon were the integrity
of the pressure chamber and
the proximity of the operator.
Mesh sheath installed around the accumulator tank
Page |8
The accumulator tank of the cannon was made out of PVC, which degrades easily. To protect the
operators from any potential bursting due to material degradation or cyclic loading, we installed a mesh
sheath around the tank and the firing valve. This sheath was rated to contain any blast that would occur
in case of rupture, but it was bulky and hard to work around.
Also, if there were any cracks or leaks in the accumulator tank, they would be hard to detect as the
material of the sheath was very fine.
The original cannon connected to the frame at a single point with the help of a collar which was far from
the optimal location to absorb the recoil when the cannon launched the pumpkins. This can lead to
failure due to cyclic loadings. Also, the
accumulator tank rested on the steel bar of the
elevator, causing the plastic to wear.
The cannon was operated completely by manual
controls on the cannon itself. This meant an
operator had to stand next to pressure vessel at all
times. This made the original goal of public
operation impossible.
Unstable pivot point
4.1.2 Ease of Operation
To aim the cannon vertically, the operator was required to use a hand-crank car jack which regularly
slipped off its support. Horizontal aiming was accomplished by manually lifting and moving the barrel.
This movement was greatly reduced to only a few degrees after the original rotator plate was removed
to help stabilize the cannon.
To charge and fire the cannon, the operator
was required to stand directly behind it and
operate a manual air compressor. Controlling
the flow was accomplished by adjusting the
pressure regulator, but when it broke, the
operator would have to control the
compressor’s power to control the air pressure.
Other operational issued included moving the
cannon. This was incredibly difficult due to the
weight of the cannon and also because of the
front wheels on the chasse did not provide
enough maneuverability as they hardly touched Unsafe operating position (Directly behind the cannon)
the ground. Most of the weight of the cannon is
carried by the rear wheels and thus it is extremely difficult to turn the cannon in any direction.
4.1.3 Miscellaneous
The cannon needed a reliable sabot design. The original sabot did not accommodate various sizes of
pumpkins and did not produce consistent results upon firing.
Page |9
The client intended to operate the cannon in the field for one month every year during which, the
cannon will have to withstand a wide range of temperatures and significant moisture. The PVC material
used on the cannon might have degraded due to UV rays, and the steel structure was easily susceptible
to rust.
4.2 DELIVERABLES
The team will deliver by May 10, a working cannon including all necessary controls and accessories to
meet the following specifications.
-
Safe for public to view at a distance of 20 feet
Able to reside outside for the month of October without any evidence of rust
No observable defects/damage to the cannon or the sabot after 50 launches
Set-up in a new location in less than 20 minutes
Operating instructions that any college student can follow without asking for outside help
Minimum cycle time between launches of 2-3 minutes
Repositioning/aiming at a new target within 30 seconds
Intriguing design that will draw an audience from over 100 feet away and get them asking
questions about cannon design and performance
5 CONCEPTS CONSIDERED AND DESIGN SELECTION
5.1 MORPHOLOGICAL CHART
Major design decisions were organized into the following morphological chart.
Aspect
Safety
Cannon Design
Requirements
Option
Flipped
Cannon
Linear
Cannon
PVC /w
Fiberglass
ABS
Steel
Fiberglass
Composite
Aluminum
Wood
Carbon
Fiber
Cross bars
Gravity
Cannon must be securely deactivated
Valve locked
open
Remote firing
Option
No possibility of material rolling/falling back into valve
Screen
Safety lock
Option
Frame supports cannon and aiming mechanism (up to 400 lbs)
Steel
Foreign debris
Option
Pressure vessel material has to be strong (accommodate up to 125 psi)
PVC
Frame
Final Choice
The cannon must be assembled in shape that is aesthetically pleasing and
structurally sound
Neck
Reduction
Tank Material
Option
Additional valve locked
close
Key required to power control systems
Cannon can be fired from a distance of 20ft by remote actuation
Electronic
solenoid
Pneumatic solenoid
Homemade actuator
P a g e | 10
Operation
Automation of
charging
Tank can be charge remotely by operator
Automation of
aiming
Horizontal and vertical aiming can be controlled remotely by spectator
Control compressor
power source
Servo motors
Valve separating tank
from compressor
Release valve near the operator
Pneumatic cylinders
Electric winches
Aiming
Mechanism
Barrel can be aimed in both directions
Horizontal
Wheel
Threaded Shaft
Belt
Vertical
Triangle
Jack
Crane (frame over the cannon)
Control System
Operation of the cannon must be controlled from one spot
Digital
Analog
Manually
Mechanical
Miscellaneous
Base wad/sabot
Ability to shoot different size pumpkins, reliable and durable
Spool
Maneuverability
Styrofoam Base wad
Polyethylene cut-out
Spray foam cylinder
Cannon must be able maneuverable by two people
Better tires
Mounted on a trailer
Remove old drive-train parts
5.2 CANNON DESIGN
The concept behind the previous cannon (a large air reservoir behind a butterfly valve) proved
successful. The team focused design efforts on how to best position these basic components
5.2.1 Compact
Short and fat accumulator tank with connected to long barrel through a series of reduced pipe
components. These components would include the solenoid valve which can be remotely triggered in
order to fire the cannon
-
Pros
Shorter in length and smaller in size
Use of solenoid valves in trigger mechanism
-
Cons
Energy losses in the neck reduction
More expensive
5.2.2 Flipped
Suggested by a faculty member, we can simply flip the existing cannon and provide more stability. The
original design supported the cannon at one point on the accumulator tank. The barrel’s distance from
this point caused a significant lever moment on the PVC whenever the cannon fired. This design would
P a g e | 11
eliminate that and would reduce expenses on extra parts and would reduce labor. Aesthetically, there
would not be any changes.
-
Pros
Same cannon components
More stability due to firmly supported barrel
-
Cons
Still bulky and hard to work around with
Not aesthetically pleasing
5.2.3 Linear
Shorter and fatter accumulator tank, in line with the barrel reduces the number of parts required for the
overall design. Linear design would be easier to stabilize and aesthetically looks like a cannon.
Pros
Cons
- Reduced number of fittings
- Not compact due to its long length
- Easy to support and stable
- Would still add significant costs
- Aesthetically pleasing
Based on the three popular choices we had, the team decided with the more stable and aesthetically
pleasing design. Thus we chose the linear cannon design and proceeded with further design features.
5.3 TANK MATERIAL
The original cannon was constructed out of PVC components: Schedule 80 PVC for the accumulator tank
and Schedule 40 PVC for the barrel. To protect against possible ruptures, a sleeve made out of high
strength mesh was installed prior to firing at the corn maze. This mesh worked fine for the existing
design but was too bulky to work around and made the cannon nearly impossible to leak test.
In addition, the mesh reduced the aesthetic features of the cannon.
To increase the factor of safety for the cannon and to make it safe for public use, the team considered
several alternatives.
P a g e | 12
Steel: This would ensure that the cannon does not rupture, thus increasing
the safety of the cannon by a large factor. But working with steel would be
quite difficult and the whole cannon would be very heavy. Professional
pumpkin cannons usually use steel.
Carbon fiber: Carbon fiber is comparatively lighter and also provides high
strength, increasing the safety factor of the cannon. It is however very
expensive due to the heat treatment that would be required to mold the
cannon shape. Also, no private firm would take the liability of
manufacturing the cannon due to safety hazard issues in case of rupture.
Fiberglass-covered PVC: Unlike carbon fiber, fiberglass does not require
special equipment to set. This design would use standard PVC components
rated for the application. Several layers of fiberglass would be applied to
the outside to strengthen it further and retain any fragments in the event
of a failure.
5.3.1 Material Testing
To strengthen the PVC, and replace the mesh with a stronger, less obtrusive covering, we experimented
with fiberglass-coated PVC. Three tests were conducted with drainage gauge PVC pipe coated in
fiberglass under pressure, each with a control.
Drop Test: We dropped a five-pound weight from a height of nine feet. The samples were filled with 30
psi of air. The control burst on impact with debris flying several feet. The fiberglass-covered model
fractured and bled out, but there was no debris.
Shoot Test: We pressurized two more samples under 40 psi and shot them with a .17 caliber rifle. This
allowed us to simulate a failure of the PVC at our operating pressures. The control shattered into
countless pieces, the fiberglass sample held solid with a thru-and thru shot.
Over-pressure Test: We overpressure two
samples to 100psi. This caused a PVC
failure for both, but the fiberglass held and
contained the air pressure and all
fragments.
Based on these results, we constructed the
cannon out of Schedule 80 PVC
components covered in 4 to 12 layers of
fiberglass.
5.4 SUPPORT STRUCTURE AND MOVEMENT
Unlike the previous design, this cannon could not support its own weight. A rigid support structure was
needed that could also point the cannon in a wide range of directions.
The support structure needed to be light and durable while withstanding the elements of nature. The
team considered different materials like steel, aluminum, wood and carbon fiber.
P a g e | 13
-
Steel would make the frame sturdy and could be fabricated at a low cost, but it would be
susceptible to rust and would make the frame very heavy.
Wood on the other hand would make the frame lighter, but it would deteriorate over the years
of service and not be nearly as strong.
Carbon fiber is light and durable, but be too expensive for the scope of the project.
Aluminum is comparatively cheaper and is corrosion resistant. Aluminum is also lighter as
compared to steel. Its main drawback was the team’s lack of aluminum welding experience. All
welding would have to be outsourced.
The design of the structure was based off a
LEGO model constructed in brainstorming
session. Vertical movement is achieved by
and A-frame support with the forward leg
moving on a track. A rigid frame for the
cannon to rest pivots on top of this frame.
This frame is stabilized by a sliding plate at
the rear of the frame.
To control the movement of this structure,
several alternatives were considered.
-
-
Servo motors connected to threaded shafts: This would allow degree of rotation degree of
control, but would be very expensive and susceptible to the elements of nature.
Pneumatics: This would require air pressure to work under, which means that the compressor
would have to run for a longer time for the pistons to be used. This would drastically increase
the time between each firing.
Electric winches: These are comparatively cheap and can lift weights up to 2000lbs. They can be
controlled remotely with ease and most of them are out-door rated.
For their low price, and high durability and strength, electric winches were used on an aluminum frame.
These two electric winches control the cannon’s movements.
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5.5 TRIGGER SYSTEM
In the previous design of the
cannon the trigger mechanism
consisted of a lever arm that
rotated 90 degrees to fully
open the butterfly valve, it was
located right behind the cannon
and created safety issues. The
new trigger system needed to
allow the user to remotely
actuate the trigger valve from a
safe distance away; it would
have to be safe, durable, and
have a low turnover time. The
team considered different
systems including
electronic/pneumatic solenoids
and pneumatic actuated
cylinders.
Electronic solenoids: Would ensure simple and dependable operation, but with the speed and torque
needed to actuate the trigger it would drive the price up of the solenoid and would require a constant
power source.
Pneumatic solenoids: Like the electronic solenoid it would be easy to operate and install, but with the
speed and torque needed to actuate the trigger it would drive the price up of the solenoid.
Pneumatic piston: This option was comparatively cheaper than the others, though it would require
more installation modifications. They also are available in many different configurations which are able
to be incorporated into our design easily.
In the final design, a pneumatic solenoid pulls a cam-shaped plate which is connected to the valve. This
allows for the right balance of torque and speed throughout the process. The valve is manually closed to
add another layer of safety.
5.6 CONTROL SYSTEM
To control the multiple operations of the cannon a control system was needed to safely allow the
operator to manipulate the cannon from a set distance away. The team considered different systems
including a digital, analog, and mechanical.
Digital system (microcontroller): Would allow for precision operation of the many different controls. It
would send feedback information about the angle and pressure readings and be able to control the
cannon wirelessly. Though with this system come complications of programing and troubleshooting.
Mechanical system: Would include a system of ropes and pulleys to the cannon. It is simple, but has
limited operation control of the cannon and would increase the likelihood of a failure.
P a g e | 15
Analog system: This option is a balance between those two systems; it includes switches, relays, and
warning LED’s to control the cannon and inform the operator.
5.7 BASE WAD
The major design problem during the first phase of the project was to provide a durable and reliable
base wad/sabot for use at the corn maze. A base wad acts as a piston between the expanding air and
the pumpkin. It makes sure the air does not escape around the uneven surface. A sabot holds the
pumpkin in place while it is traveling down the barrel. It reduces the friction and the wear on the barrel.
5.7.1 Foam Cylinder
The team designed and tested two different concepts for the base wads. The first was a Styrofoam
cylinder wrapped in felt to reduce friction and create the seal. The felt extended beyond the wad to act
as a sabot. Three versions of this design were built. This design performed well, but quickly deteriorated.
In subsequent prototypes, we replaced the felt with high strength mesh, and added polyethylene
padding to the top and bottom.
The foam cylinder base wad is wrapped in black felt to
reduce friction.
5.7.2 Spool
To reduce friction, the team used old wire
spools with polyethylene glued to the ends.
However, the flat ends were not strong enough
to hold the air pressure.
The final base wad design is similar to the original foam cylinder,
but more durable.
P a g e | 16
6 DESIGN EVALUATION AND RECOMMENDATIONS
The team feels this final product is the best cannon possible for the allotted budget. Our safety and
reliability concerns are mentioned below.
6.1 AREAS OF CONCERN
The main area of concern with the finished product is air leaks. The air tank is under very high stresses
while charged and may leak over time. The team is confident in the event of a failure the fiberglass will
hold any debris, but it could leave the cannon unusable. The attached Owner’s Manual contains
instruction for periodic leak tests. Leaks could also occur in the pneumatic manifolds, but would be easy
to repair.
Electrical shorts and loose connections may also occur in the future. In this event, a technician with an
electrical background will be needed to repair the damage before the cannon is used again.
6.2 POSSIBLE IMPROVEMENTS
The electrical connector between the cannon and the control boxes is not rated for the kind of outdoor
use to which it will subjected. A suitable part was not able to be found, and it should be handled with
care.
A solenoid valve was originally installed in the pneumatics system to act a safety release valve. At the
end of the project, it was not functioning for unknown reasons. It was replaced with a manual valve for
the final product, but the wiring and controls for it remain. If the problem is ever corrected in the future,
it would be relatively easy to reinstall.
Early in the project, the team planned on installing a large decal on the cannon as seen in the rendering
below. The idea for a decal was scrapped, as it would not stand up the elements over time, but the team
does recommend some decoration be painted directly onto the cannon.
A possible decal location on the cannon
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APPENDICES
APPENDIX A – FINAL PRODUCT PICTURES
Final assembly and its components
Figure 1 – Components from left to right: compressor, user control box, operator control box, novelty firing box, and cannon
Figure 2- Cannon at max launching angle (30 degrees)
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Figure 3 (above) - User and operator control boxes
Figure 4 (right) - Trigger Mechanism (Cam shaped trigger
plate & pneumatic cylinder)
Figure
6 – VerticalAiming
AimingAssembly
Assembly
Figure
5- Horizontal
Figure 7 – Electronic Control Box
Figure 6 – Vertical Aiming Assembly
Figure 8- Pneumatic Control Box
P a g e | iii
APPENDIX B—PROJECT BUDGET
Project costs were split roughly in quarters
between the cannon itself, the support structure,
the control systems, and miscellaneous costs.
These numbers are significantly higher than
initial predictions. The increases came mainly
from the desire to use durable parts that will last
for the design life of the cannon. The increase in
the cost of the physical cannon components was
caused by fluctuations in the cost of high
strength plastics.
Corn Maze/Sabots
Firing Equipment
Measurement Equipment
Sabot Construction
Total
Material Testing
Cannon Assembly
Tank
End Cap
Reducer
Flanges
Fiberglass
Total
Support Frame
Material
Welding
Hardware
Total
Control Systems
Controls
Automation
Enclosures
Misc.
Total
Painting
ME Shop Fees
Project Total
Corn Maze/Sabots
Testing
Cannon Assembly
Support
Control Systems
Painting
Shop Fees
$ 142
$ 237
$ 90
$
$
$
$
$
$
$
469
94
484
198
275
85
265
$ 1,308
$ 684
$ 480
$ 288
$ 1,452
$ 550
$ 537
$ 244
$ 719
$ 2,050
$ 189
$ 438
$ 6,000
P a g e | iv
APPENDIX C—PROJECT TIMELINE
Sept.
The week beginning:
Team Organization
Sabot Fabrication
Sabot Testing
Cannon Preparation
Corn Maze
Usability Tests
Conceptual
Designing
Material Tests
Design Finalization
Cannon
Parts Acquisition
Fabrication
Testing
Support Fabrication
Control Systems
Designing
Parts Acquisition
Fabrication
Final Assembly
Painting
Test Firing
3
10
17
Oct.
24
1
8
15
Nov.
22
29
5
12
19
Dec.
26
3
10
17
Jan.
24
31
7
14
21
Feb.
28
4
11
18
March
25
4
11
18
April
25
1
8
15
May
22
29
6
Page |v
APPENDIX D—TEAM CONTRACT
Section 1: Team Name and Mission:
This team shall be named 'Pumpkin Sharpshooters' The mission of this team is to
• Collaborate with CALS to design safety measures for the use of the existing cannon and train its
operators
• Build a next generation cannon for use in future years.
Section 2: Membership:
Members of this team are Michael Fujikawa, Amey Shigrekar, and Jeff Reznicek.
Section 3: Roles and Responsibility:
Specific responsibilities of this person include overseeing other team members and keeping them on
task, assigning tasks to other members, and communicating with the sponsor.
• The team leader shall be Jeff Reznicek. Specific responsibilities of this person include calling
meetings, managing the budget, keeping the team on task, and managing meetings.
• The communicator shall be Amey Shigrekar. Specific responsibilities of this person include
keeping in contact with the sponsor, other teams working on the project, and the project
advisor.
• The documenter shall be Michael Fujikawa. Specific responsibilities of this person include
compiling and managing all documentation. This person also works as the photographer.
Section 4: Joint Work:
Team members will respect each other’s ideas, participate in group discussions, attend meetings,
encourage new ideas and each other, and offer assistance to team members falling behind.
Section 5: Individual Work:
Team members will strive to meet any deadlines assigned, and alert other members if a deadline will
not be reached. They will complete their assignments to defined expectations of quality.
Section 6: Documentation
Documentation
Team members will maintain the following records of their work: Individual notebooks for note
taking and brainstorming and a digital drop box for all emails, reports, and digital research.
Communication among members
Team members will keep one another informed about project developments, problems that
arise, and schedule changes by phone and e-mail.
Communication with outside stakeholders
Outside persons, including clients and lead instructors, will be kept informed about project
developments and questions by email.
Section 7: Conflict Resolution
This team will strive to resolve conflicts quickly and to the satisfaction and benefit of everyone involved.
To this end, the team members agree to bring any conflicts to the entire group where it can be resolved
by communication and rational discussion.
Section 9: Amendments
This contract may be amended by unanimous approval of the team members.
P a g e | vi
Section 10: Affirmation of Compliance
We, the members of this team, affirm that we have established this contract with input and consensus
of all members. By our signatures, we commit to compliance with the contract for the benefit of all
members and the whole team.
Michael Fujikawa
X____________________________
Date:____________
Amey Shigrekar
X____________________________
Date:____________
Jeff Reznicek
X____________________________
Date:____________
P a g e | vii
APPENDIX E - MATH MODEL
P a g e | viii
P a g e | ix
Support
Connections
become loose
Welds fail
RPN
Vertical and
Horizontal
Aiming
Bolts come
loose
Current Design
Controls
Wheels large enough
for most terrains
1
3
2
Locking washers
1
6
Cyclic loading/vibration
2
Locking washers
1
6
4
Cyclic loading/vibration
3
Locking washers
1
12
4
Cyclic loading/vibration/
rust
1
Layer of paint
3
12
3
Failure of track sensors
4
Safety track sensors
1
12
1
9
1
4
3
Potential Causes(s) of
Failure
Rough terrain
Occur
Frame
Symptom
Axle breaks
3
Cyclic loading/vibration
Cannon gets
loose from
frame and goes
un-noticed
Support fails
and cannon
falls apart
Support fails
and cannon
falls apart
Unable to
position the
cannon
3
SEV
Item and Function
Base
Wheels
Potential
Effect(s) of
Failure
Shrapnel,
unusable
cannon
Cannon visibly
falls apart
Detect
APPENDIX F – DFMEA
1
Wheels
Runs off track
Winches
Doesn’t
operate
Unable to
position the
cannon
3
Electrical problem
3
Cable breaks
Unable to
position the
cannon
4
Cyclic loading
1
Inspection before
operation
Recommende
d Actions
Check terrain
before moving
cannon
Tighten all
bolts before
operation
Tighten all
bolts before
operation
Tighten all
bolts before
operation
Routinely
examine for
cracks/rust
Safety stop
switches are
secure and
operational
Routinely
examine,
replace if
needed
Routinely
examine for
wear, replace
if needed
Page |x
Trigger
Mechanism
Breaks under
tension, injury
and damage to
cannon
5
Cyclic loading
1
Inspection before
operation
1
5
Bushing/
bearing
Wears down
Cannon
movements
unstable
2
Excess use
2
Inspection before
operation
3
12
Pivot
plates
(Teflon)
Wears down
1
Excess use
4
Inspection before
operation
2
8
Air cylinder
Shaft bends
Cannon runs
into increased
resistance
when
positioning
Unable to
actuate trigger
valve
3
Excess force
3
1
9
Cam plate
Bolts come
loose
Cam plate falls
apart, unable
to fire cannon
3
Cyclic loading
2
3
18
Steel cable
Cable breaks
4
Cyclic loading
1
Inspection before
operation
1
4
3
Fatigue/rust
3
Paint/inspection before
operation
3
27
Auxiliary
air tank
Leaks
Unable to fire
cannon
Pressure
doesn’t hold
Routinely
examine for
wear and tear,
replace if
needed
Routinely
examine for
wear and tear,
replace if
needed
Routinely
examine for
wear and tear,
replace if
needed
Routinely
examine,
replace if
needed
Routinely
examine,
tighten if
needed
Routinely
examine for
wear and tear,
replace if
needed
Check during
each soap test
P a g e | xi
Pneumatic
Control
Systems
Electronic
Control
Systems
Fails (explodes)
Shrapnel
5
Fatigue/rust/failure of
safety valve/over pressure
1
Paint/inspection before
operation/bleeder
valve/regulator
1
5
Solenoids
Doesn’t actuate
Unable to
actuate main
parts of the air
system
3
Frayed, no power
1
Enclosed in a weather
proof box
3
9
Regulators
Doesn't allow
through correct
pressure
Provides
over/under
pressure to
components
3
Excess use
2
3
18
Tubing
Leaks/
disconnecting
Air
leakage/doesn’
t hold pressure
3
Weathering, excess pressure
3
Hose clamps
2
18
Fittings
Leaks
Air
leakage/doesn’
t hold pressure
3
Excess pressure
1
Teflon tape
2
6
Battery
Doesn’t hold a
charge
Unable to
operate
electronic
controls
3
Cyclic loading
3
1
9
Check bleeder
valve for
correct
operation, and
correct
regulator
pressure
Routinely
examine for
correct
operation,
replace if
needed
Routinely
examine for
correct
operation,
replace if
needed
Routinely
examine for
leaks, replace
if needed
Routinely
examine for
leaks, replace
if needed
Routinely
examine for
correct
operation,
replace if
needed
P a g e | xii
Battery
charger
Doesn’t provide
charge
Unable to
charge battery
3
Electrical problem, excess
use
3
2
18
Switches
Non-responsive
Unable to
actuate control
system
3
Loose connection, excess
use
1
1
3
Wiring/
connection
s
Frayed
Sparking,
potential for
short circuit
4
Weathering
1
4
16
Loose
connection
Sparking,
potential for
short circuit
4
Vibration
3
4
48
LEDs
Don’t light up
Unable to
assure
operator of
cannon
operations
3
Loose connection, excess
use
1
1
3
Fuses
Blown
Unable to
operate
electronic
controls
2
Excess amperage
4
2
16
Routinely
examine for
correct
operation,
replace if
needed
Routinely
examine for
correct
operation,
replace if
needed
Routinely
examine,
replace if
needed
Routinely
examine,
tighten if
needed
Routinely
examine for
correct
operation,
replace if
needed
Routinely
examine for
correct
operation,
replace if
needed
P a g e | xiii
Cannon
Structure
Control
boxes
Leak
Moisture,
potential for
short circuit
4
Rough handling
3
Air fitting,
pressure
relief valve
and
pressure
gauge
Leaking
Pressure
doesn’t hold
3
Hairline fracture around
fittings
1
Falling out
Could shoot
out
5
Thread sheering
1
Air hose
Tearing,
disconnect
Air leakage
2
Weathering, excess pressure
1
Butterfly
valve
Valve won't
seal
Unable to
charge tank
3
Valve broken
1
Debris stuck in valve
2
Over pressurizing
1
Fatigue
1
Tank, end
cap
Burst
Shrapnel,
unusable
cannon
5
3
36
Routinely
examine for
leaks
1
3
Check during
each soap test
3
15
Material type, screw in
connection
1
2
Inspect before each
season
1
3
3
18
Stand clear
when tank is
charged
Inspect hose
regularly,
replace if
necessary
Read safety
manual
frequently,
especially
before each
season
Remove valve
and clean out
Safety valve, mesh
covering, steel
exoskeleton
3
15
Short design life
3
15
Sealed with tape
Set regulator
on air
compressor to
45 psi,
monitor
pressure
gauge
Use for one
season only
P a g e | xiv
Major leak
Miscellaneous
Accumulator
won't hold
charge
4
Over pressurizing
1
Safety valve, mesh
covering, steel
exoskeleton
3
12
Fatigue
1
Short design life
3
12
Minor leak
Accumulator
won't hold
charge for long
2
Improper cementing
1
All joints were properly
cemented
1
2
Fiber
glassing
Degradation of
material
Won’t be able
to hold
shrapnel in
case of failure
4
Weathering
2
Multiple layers, paint
2
16
Sabot
Degradation
Failure to
launch
1
Moisture, excess force
1
Material type
1
1
Stuck in barrel
Failure to
launch
3
Improper loading
1
Smooth barrel
2
6
Set regulator
on air
compressor to
45 psi,
monitor
pressure
gauge
Use for one
season only
Regularly
administer
soap test to
detect leaks
and seal them
Routinely
examine,
repair if
needed
Monitor the
condition of
the sabot and
replace when
needed
Use plunger to
load
APPENDIX G – OWNER’S MANUAL
The attached manual contains instructions for the safe operation of the cannon as well as maintenance instructions. At least one copy should be laminated and
kept with the cannon at all times.