cargo pod design kyle bergen ejvin berry cody candler mike gavanda
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Cargo Pod Design
Kyle BergenEjvin Berry
Cody CandlerMike Gavanda
Individual Report
• Ejvin Berry• 68 hours• Tasks
– Initial Aerodynamics Optimization– Quick Prototype Modeling– Final Concept Modeling
Cirrus SR22 Cargo Pod
Cargo Pod Guidelines
With 2 passengers (including pilot), 4 hours of fuel, carry one of the following:
• 2 sets of skis with equipment– Required volume of 12in x 6in x 79 in
• 2 sets of golf clubs (with drivers)– Required volume of 35in x 11in x 50in
• Minimum 8” offset from firewall
Pod on Fuselage
Clearance/ Tail Strike Envelope
Bottom View
Attachment View
Front Fairing (2)
Rear Fairing
Conclusions
• Demonstrates – Practicality
• Meets required tasks, loads
– Ease of Operation• Location specific
– Aesthetic Quality– Aerodynamics
Recommendations
• Study feasibility of manufacturing contoured pod surfaces to mesh with fuselage.– Increased capacity – Fit CG envelope better– Aerodynamics Improved
Attachment Methods
Individual Report by Kyle Bergen80 hours worked
Attachment to Longerons
• Three points of attachment for stability and ease of attachment
• Use longerons as hard points to anchor mounting brackets which extend to belly.
• One piece assembly screwed to belly attachment.
• Bolts secure attachment pieces together from embedded pieces in pod fiberglass
Front Mounting Brackets (Two)
Rear Mounting Bracket (one)
Under belly attachment from bracket to Pod (three)
Embedded in Top of PodSlides into underbelly attachment
Belly Plugs when Pod is not attached
General Analysis
• Cosmos Express in Solid Works was used to diagnose the stresses on parts
• Maximum forces were used with total weight of Pod with load (120 lbs), with 4 G’s applied and safety factor of 1.5. Total force of 720 lbs.
• C.G. of front loaded pod (two golf bags) calculated
General Analysis Cont.
• 216 lbs on each front attachment and 288 lbs on rear attachment.
• All bolts to the longerons and to the pod/belly attachments are ¼ in.
• Screws to the belly bracket attachments are in. 8
3
Allowable Loads• Allowable Load=(Allowable Stress/Safety Factor)(Area)• For Bolts and Screws of 304 Stainless Steel, Tensile Strength
Yield is used as 31200 psi, a shear strength of half the yield is used, 15600 psi, though online sources show it much higher, I will use a low number.
• Bolts through under belly attachments are in double shear so we see an allowable load of 2297 lbs.
• Screws in Tension see the yield strength of 31200 psi, we see allowable load of 2297 lbs as well. (since in double shear we use twice the area and Yield strength is twice the shear strength we see the same result.)
• These allowable loads are well above what the pod would see.
Stresses in bolts to longerons
• Since there are two bolts into the longerons on each front attachment we take the Total force on each bolt to be 216/2 on the front for a force of 108 lbs. For the rear bracket each bolt sees 72 lbs.
• These bolts have a smaller area so we see an allowable load of 510.5 lbs in shear for each bolt.
• These requirements are met by the 304 Stainless Steel bolts of ¼ inch diameter.
Deformation Picture of front attachment
• Multiplied many times for show• Safety factor of 2.47
Statistics
• Piece was run with both 304 S.S. and Alloy 2018.
• 2018 is chosen because of lower weight and higher yield
• Weight of Piece is .22 lbs• Max Stress in Piece 18560 psi• Max Displacement is .005 inches at base.
Deformation Picture of Rear Attachment
• Lowest Factor of Safety in design is 4.82
Statistics
• Piece was run with both 304 S.S. and Alloy 2018.
• 2018 is chosen because of low weight (3 times less) and higher yield
• Weight of piece is 1.4 lbs• Max Stress in piece is 13880 psi• Max Displacement is .005 inches
Deformation in Under belly attachment to pod piece
• Safety Factor of 1.95
Statistics
• Piece was run with both 304 S.S. and Alloy 2018.• 2018 is demonstrated here• Data taken was for 288 lbs, so pieces are not
exclusive to one attach point, three identical pieces.• Weight of piece is .31 lbs• Max Stress in piece is 1798 psi• Max Displacement in piece is .00005 inches
Displacement of Embedded Pod Piece
• Safety Factor 25.48
Statistics
• The piece was run testing both 304 Stainless and Alloy 2018.
• 2018 is recommended because of its slightly higher yield strength and much less weight
• Weight of piece is .32 lbs• Max Stress in piece is 1804 psi• Max displacement is .00005 inches.
Final Statistics
• Total weight of the attachment method is 3.73 lbs• 304 SS would have worked for all pieces as well, and even
reduced some of the displacement, however, the weight would have been significantly increase.
• 304 SS is used for bolts since that is a primary use of 304 SS.• Alloy 2018 is chosen because it is a high strength alloy. It is
very easily machined and is a tough alloy that can be used for heavy duty structural parts.
Conclusions• The attachment methods as designed work for the support of the cargo
pod.• Front attachments are placed on the inside of the longerons at 19 inches
behind firewall and rear attachment is placed between longerons at 69 inches behind firewall. Inspection of longerons looked to be good placement.
• Would have liked to do further analysis on the Longerons and get more accurate dimensions.
• Wish we would have nailed down a design sooner since a lot of the semester was spent on investigation of workable/do-able pod designs.
• Further work would include optimization of current design pieces and trying different designs.
• I would like to thank my team and Steve Hampton for all the support throughout the project!
Individual Report
• Mike Gavanda• 70 hours• Worked on
– Ground clearance– Tail strike clearance– Pod access
Solid works attached Pod model
01:29 PM
Clearance
01:29 PM
Solid Works model
01:29 PM
Clearance/ Tail Strike Envelope
Pod wheel Clearance
01:29 PM
Golf Bag
Width 10 in
Height Bag 34 in
Height with clubs 50 in
Average Golf Bag Size
01:29 PM
Golf Bag Clearance
01:29 PM
SkisLength (cm) 173 180
Side cut tip(mm) 130 135
Waist (mm) 96 99
Tail (mm) 124 125
Weight (g for one ski) 1970 2210
http://www.salomonski.com/us/products/XW-Sandstorm-1-1-1-788918.html01:29 PM
Skis and pod
Access
Access Seal
*www.aircraftspruce.com/catalog/hapages/camloc4002.php**www.trimlok.com/detail.aspx?ID=933
Camloc 4002 Studs*2600 and 2700 series made of steel Shear: 1050 lbs. (ultimate)Tensile strength: 700 lbs. (rated)Rated to 450° F
Example of watertight hatch seal**
Conclusion
• Meets clearance and size goals– Clears fully loaded landing– Clears tail strike– Safe distance from exhaust– Fits a pair of golf bags or 2 pairs of skis
• Easy access
Recommendations
• Find more on how the exhaust affects pod• See if clearance can be increased for landing
and tail strike• More study of water tight seal on access door
Individual Report
• Cody Candler• 70 Hours• Tasks
– Location of the center of gravity• Ensure it meets ground requirements
– Aerodynamics Analysis– Range Optimization
Reference points of the front and back of the cargo pod while attached(Figure 6-1 out of the Cirrus Manual)
C.G. of the aircraft with the pod attachedSample Loading• Pilot – 200 lbs• Passenger – 200 lbs• Fuel – 486 lbs (full tank)• Cargo Pod – 100 lbs
Center of Gravity Limits
• No Luggage
• Luggage – 25 lbs
• Luggage – 50 lbs
C.G. of pod located at FS 148.0
Moment Limits
Used Component Buildup Method out of Aircraft Design: A Conceptual Approach by Raymer
Approach used:Find flat-plate skin-friction drag coefficient (Cf)
– Assumed complete turbulent flow
Find the component “form factor” (FF)– estimates the pressure drag due to viscous separation– assumed the pod to be a fuselage
where
– Amax is the maximum cross-sectional area of the pod which is 3.224 ft2
– l is the length of the cargo pod (6.583 ft)
Estimate CD for cargo pod
65.0258.210 144.01log
455.0
MRC f
600
601
3
f
fFF
max/4 A
l
d
lf
CD Estimate cont…
Determine interference effects on the component drag (Q)– Raymer says if the component is mounted less than one diameter away from the
fuselage then the Q factor is 1.3
Find the wetted area (Swet)
– Total exposed surface area
2674.292
4.3~ ftAA
S sidetopwet
Calculate total component drag
Sref of SR-22 wing is 144.9 ft2
Result:CD = 0.002577
ref
wetf
subsonicD S
SQFFCC
0
Extra power needed with pod attached• Use general power required equation
PR = TRV∞
• In steady, unaccelerated flightTR = Drag (in our case, drag is increased drag from pod)
• For each altitude, I used the cruise performance data from the Cirrus manual – I only used data where engine was operating at 2700 RPM since the engine has a rating of 310 hp at 2700
RPM– This gives a conservative estimation of the additional power needed to travel at the same velocity with
the pod attached as when it isn’t attached
0
5
10
15
20
25
0 2000 4000 6000 8000 10000 12000 14000 16000 18000
Altitude (ft)
Ad
dit
ion
al
Po
we
r (h
p)
Effects on Velocity• Calculate an approximate CD of the SR-22 using the cruise performance data out of the Cirrus manual
• Add the cargo pod component drag coefficient to the total aircraft drag coefficient
• At 2700 RPM and same power, calculate velocity of aircraft with the pod attached and without the pod attached
Result• 7% decrease in velocity with the pod attached
270
275
280
285
290
295
300
305
310
315
320
0 5000 10000 15000 20000
Altitude (ft)
Vel
oci
ty (
ft/s
)
Velocity with Pod Attached
Velocity w/o Pod
Sample streamlines around the cargo pod
Sample Pressure Distribution on Pod
Sample Pressure Distribution on the pod with a crosswind
Crosswind
Crosswind
Maximum Speed with Cargo Pod Attached
Conditions:•Get to a location as fast as possible•4 hours endurance•81 gallons of usable fuel•Weight: 3400 lbs•Take off from sea-level•No wind
Results w/o Pod:Optimal Cruise Altitude: 12000 ft• Fuel to taxi: 1.5 gal• Fuel to climb: 4.4 gal• Fuel to cruise: 59.8 gal @ 15.4 GPH• 45 min IFR fuel reserve: 9.8 gal• Airspeed: 178 KTAS• Range: 785 nautical miles
Adjusted results for attached cargo pod:• Airspeed: 166.4 KTAS (7% reduction)
• Range: 730 nautical miles• Endurance of 4.3 hours
Maximum Range with Cargo Pod Attached
Conditions:• Maximum range• 81 gallons of useable fuel• Weight: 3400 lbs• Takeoff from sea level• No wind
Results w/o Pod:Optimal Cruise Altitude: 14000 ft• Fuel to taxi: 1.5 gal• Fuel to climb: 5.3 gal• Fuel to cruise: 57.8 gal @ 11.3 GPH• 45 min IFR fuel reserve: 9.8 gal• Airspeed: 169 KTAS• Range: 1006 nautical miles
Adjusted results for attached cargo pod:• Airspeed: 143.7 KTAS (7% reduction)
• Range: 935 nautical miles •Endurance of 5.8 hours
Conclusions
• Due to the restriction of the center of gravity of the cargo pod (FS 148.0) a weight of at least 25 lbs must be added to the luggage compartment for the SR-22 to be safe to fly
• A 4 – 8% increase in power is needed to travel at the same speed with the cargo pod attached as it would without the pod attached
• The cargo pod decreases the velocity of the SR-22 by approximately 7% when attached
• The maximum range of the SR-22 with a full tank of fuel and the cargo pod attached is 935 miles
• The customer would need to sacrifice range or use more fuel when operating with the cargo pod attached
Recommendations• Mesh top of pod to the bottom of the fuselage to
reduce the drag area and increase performance– Free up room to move the pod further back on the
fuselage, which would move the C.G. aft and maybe eliminate the need for a requirement of 25 lbs of luggage
• Spend more time studying pressure hot spots– Contour the front of the pod more to further reduce drag– Revise the back half of the pod to prevent flow separation
and reduce drag
Individual Report
• Dan Poniatowski• 75 hours of work• Accomplishments
– Documented and managed schedule and Gantt Chart– Documented requirements– Facilitated communication between the team and the
sponsors– Coordinated trips to the Cirrus factory in Duluth – Facilitated FMEA and Environmental/Societal Impact
analysis– Produced a Design Summary for the belly pod consistent
with Cirrus’ method of documentation
Problem Probability Severity Mitigation
High Lift Device Flutter due to failure Low High Pull Parachute.
High Lift Device Flutter due to aerodynamics Medium High
Test for natural frequencies. Avoid frequencies of prop and install dampening.
Cable/Mechanical Failure Low High Pull Parachute.
High Lift Device Extension/Retraction Failure Low Low Install mechanical indicator to inform pilot.
Spin Entry Medium Medium Install warning placards and mandate anti-spin pilot training.
High Lift Device Detachment Low High Design fasteners to release when a partial failure occurs. Pull Parachute.
Icing High Varies Incorporate existing deicing equipment into new design.
Collision Damage Medium Medium Reinforce leading edge. Pull Parachute.
Wing Detachment Low Very High Pull Parachute.
Internal Fuel Leak Low MediumInstall fluid detector and warning device. Instruct pilot to deactivate electronics and land immediately.
External Fuel Leak Low Low Instruct pilot to land immediately.
Lightning Strike Medium Medium Install dissipating mesh in the wing and high lift devices.
Heat Damage Medium Low List warnings in Pilot's Operating Handbook.
Problem Probability Severity Mitigation
Pod hits the ground Medium Low Fasteners designed to shear off and release pod.
Partial Attachment Failure Low High Remaining attach points designed to shear off.
Foreign Object Collision Medium Low Reinforce the nose of the pod.
Front End Overheating High Medium Attach a metal heat sheild to the nose.
High G Failure Medium High Designed to withstand a 3G manuever.
CG Out of Balance Due to Loading High High Warn the pilot in the Pilot's Operating Handbook and install placards.
Failure Modes and Effects Analysis
Problem Category Severity Mitigation
High performance wing causes society to distrust general aviation as a result of accidents. Society Low Press releases on the advantages of the new wing design.
Wing performs well enough to edge competitors out of the market. Global Low Sharing of new wing technology.
Complexity of high lift device design deters new pilots. Society Low Simplification of pilot interface.
Problem Category Severity Mitigation
Pod is used for smuggling drugs. Society Low
Pod is used by terrorists to deliver weapons. Society High
Pod is used as a chemical distribution tank. Environment Medium
Additional power required for use of pod consumes more fuel. Environment Very Low Make pod easy to remove when not in use.
Environmental, Societal, and Global Impacts
Pod Design Summary
• Follows Cirrus’ Method of Documentation• Documents design requirements and goals.• Documents the design concepts along with
pros, cons, risks and mitigation. • Documents the design process to provide
insight to further investigation.
Pod Design SummaryDesign Summary
ATA : Add ATA 4 Digit CodeAdd ATA 4 Digit Code
Project : SR24
Title : SR-22 Cargo Pod
Author : Daniel Poniatowski
Created : Nov. 4, 07
Modified : Dec. 12, 07
Pod Design Summary
Concept 2: Streamlined Closed Pod.
Sketch
Pros
Excellent aerodynamic performance
Holds goal cargo in one pod
Excellent Aesthetics
Cons
Sealing the pod to the fuselage is high risk.
Pod has poor utility.
Pod is not optimized for user friendliness.
Risks & TBD & New Items
1. Sealing the pod to the fuselage is expensive and prone to major failure during use.
2. Pod will not be a success with consumers because it is difficult to use.
Risk Mitigation
1. Change design to a closed pod to remove the need for a seal system.
2. Closed pod design will increase user friendliness and accessibility. Aerodynamics has become secondary to utility, safety and user friendliness.
Key Characteristics
1. Pod satisfies design requirements.
2. Pod satisfies design goals.
3. Pod has acceptable aerodynamic performance while optimizing user friendliness and utility.
4. Pod is optimized for ease of production and profit.
5. Pod is optimized for ease of removal to give the consumer flexibility and increase satisfaction.
Compromises
1. Less than optimal aerodynamic performance.
2. Pod is less stylish than previous designs.
Design Review: Comments & Sign Off. Text.
Design CE: ____________________ Date: ________________
Tool Lead: ____________________ Date: ________________
Production Lead: ___________________ Date: ________________
3 Detail Design / Model
Drawing File
File Names:
Conclusions and Recommendations
• Gantt chart was useful for planning purposes• Wiki was useful for common file sharing• Requirements were recorded in a common location,
a more stringent process would be useful. • Schedule more time for risk mitigation• Schedule more reviews during the design process• Be more aggressive in achieving results and ensuring
metrics are being met.
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