This document serves to identify the steps taken to complete the final design of Jonathon’s stroller. The project began in the fall of 2018 and was completed in the spring of 2019. First, the team conducted customer research where Mrs. Aguayo was interviewed to gain an understanding of her needs, and the team visited Jonathon’s home to explore the current products that he uses.
Current products were also researched that met certain needs of Mrs. Aguayo. From this
research, the scope of work was clearly identified and the team began ideation. It is important at this stage to keep possibilities broad in case they end up sparking solutions that are feasible.
Ideation came to an end as the team found an initial design direction by focusing in on a handful of the most promising solutions.
At first, the design direction focused on reclinability along with the sponsor’s other needs. After ideation and creating a prototype for reclining the stroller, the team realized that creating a safe, reclinable stroller better than the donated stroller already implements might be outside of our expertise. Therefore, reevaluated with Mrs. Aguayo and came to a consensus that the reclining aspect of the stroller is outside of our scope of work. That was the major change to our scope of work, everything else remained fairly consistent.
Once the team refocused the design direction, the project was split up into three subsystems;
wheels, seat, and safety constraints. The safety constraints are the leg abductor and harness that keep Jonathon in the stroller. For the wheels, Braeden designed a four wheel-base with caster
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wheels to improve maneuverability and shorten the length of the wheel base. The chosen design for the wheel subsystem includes the wheel system ordered from eBay, as touched on in the final design section. For the seat, Reid and Juan chose to have mesh side walls implemented and slots for the leg abductor to slide into on the bottom of the seat. As for the safety subsystem, Morley designed a leg abductor that consists of a wood block covered with neoprene foam and fabric.
The fabric has Velcro on the flaps, shown in the final design section, so that it can be attached to the bottom of the seat. The harness is the donated butterfly harness from the Aguayo family and will be outsourced to be stitched onto the straps of the donated Axiom stroller.
During manufacturing, there was a mixture of team member completion and outsourcing. The manufacturing that the team took care of was cutting and mitering the wheel base and building the leg abductor. The initial plan for the leg abductor was to cut foam with a hot knife. The hot knife turned out to be toxic and inaccurate. After attempting this manufacturing step, Morley redesigned the leg abductor to be covered with neoprene foam that could be cut with hand scissors. After completing the leg abductor and alterations to the wheel base, the frame was outsourced to Gentry Welding and the seat and leg abductor were outsourced to Mitch’s Stitches.
The welding went great and was free of charge. However, the leg abductor fabric was stitched inside out so we outsourced the leg abductor once more to Mitch’s Stitches and the second time around came out just like the team wanted. After manufacturing, the team moved on to testing.
The team conducted nine tests to verify the design. The tests are explained in greater detail in the design verification section of this document. All of the tests passed the first round with the exception of the sizing test. This test verified that the seat accessories (i.e. harness and leg abductor) fit Jonathon but were improperly positioned. Morley and Reid visited Jonathon at school and realized the harness needed to be repositioned. Instead of outsourcing, Morley and Reid elected to give the seat to Poli Maya for stitching the second time around. Mr. Maya did a great job and the final harness is with thanks to his upholstery. After outsourcing to Mr. Maya, every design verification test was a pass. Some aspects that stood out during testing were the weight of the stroller and the tipping force. The weight of the stroller is now 30.5 lb while Jonathon’s old stroller is around 50 lb. The tipping force required to tip the stroller over with Morley sitting in it is 46 lb. Before alterations to the Axiom stroller, it took around 15 lb to tip the stroller over with Morley in it. Therefore, the team significantly improved the weight of the stroller and tipping force in comparison to Jonathon’s old stroller and the initial condition of the Axiom stroller, in addition to meeting the rest of Mrs. Aguayo’s needs.
There is only one concern about the final product of the stroller. That is the maneuverability of the wheels. Without anyone sitting in the stroller, one of the wheels is free to spin. This could be a result from a handful of causes. The wheel constructions might be different heights or the cross bar on the wheel base could be welded slightly crooked. It could even be caused by
When Morley is sitting in the stroller the problem is less apparent and the team is confident it will not be an issue for Mrs. Aguayo and Jonathon. However, this is a design concern.
If the team were to conduct this project again, a major change would be the manufacturing on the wheelbase. The difficulty of making all the components square without a naturally flat datum on the stroller to reference was immense. To combat this a more comprehensive set of jigs to both drill and weld would be designed. Likely this would mimic a bike frame jig by using a large
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machined surface and tubing blocks to positively locate and secure the critical aspects of the stroller frame. Utilizing softer wheels would also provide some forgiveness in the wheel alignment and make any discrepancy practically unnoticeable. Other than that, the project ran pretty smoothly. Organization tactics could have been more consistent, but the tools used for organization were great.
Next steps could include personalizing the seat fabric to something related to Marvel,
considering Jonathon’s love for Marvel. Also, the basket in the stroller is not completely rigid so stitching in sidewalls on that could be something to do by Mr. Maya. Mrs. Aguayo also
mentioned that Jonathon may not need the leg abductor in the near future so another alteration that could be made is removing the leg abductor and stitching the seat slots back together. The team is aware that Mrs. Aguayo has added personalized accessories to Jonathon’s current stroller so of course those same accessories may be attached to the new stroller.
Morley, Reid, Braeden, and Juan can’t wait to see Jonathon using his new stroller and are excited to see any alterations that Mrs. Aguayo may choose to make to the stroller. It was a pleasure working with the Aguayo family and the team wishes them all the best.
Figure 37. That’s a wrap!
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References
[1] “Convaid Trekker.” ESpecial Needs, www.especialneeds.com/convaid-trekker.html.
“Freedom Pushchair Stroller.” ESpecial Needs, www.especialneeds.com/shop/special-needs-strollers-wheelchairs/special-needs-strollers/baby-jogger-freedom-stroller.html., Accessed 10 Oct 2018
[2] “Convaid Cruiser Stroller.” ESpecial Needs, www.especialneeds.com/shop/special-needs- strollers-wheelchairs/special-needs-strollers/convaid-cruiser.html., Accessed 10 Oct 2018 [3] “Adaptive Star Axiom Endeavour 3 Special Needs Stroller.” ESpecial Needs,
www.especialneeds.com/shop/special-needs-strollers-wheelchairs/special-needs-strollers/adaptive-star-axiom-endeavour-3-special-needs-stroller.html., Accessed 10 Oct 2018
[4] “Special Tomato Jogger All Terrain Stroller.” ESpecial Needs,
www.especialneeds.com/shop/special-needs-strollers-wheelchairs/special-needs-strollers/special-tomato-jogger-all-terrain-stroller.html., Accessed 10 Oct 2018
[5] “Freedom Pushchair Stroller.” ESpecial Needs, www.especialneeds.com/shop/special-needs strollers-wheelchairs/baby-jogger-freedom-stroller.html., Accessed 10 Oct 2018
[6] “Maclaren Major Special Needs Stroller.” ESpecial Needs,
www.especialneeds.com/shop/special-needs-strollers-wheelchairs/special-needs- strollers/maclaren-major-special-needs-stroller.html., Accessed 10 Oct 2018
[7] Trujillo, Robert, et al. Joseph's Jogger. Mechanical Engineering Department, 2017, pp. 1 128, Joseph's Jogger.
[8] A. deCsesznak, et al. Nathan’s Mobility Device. Mechanical Engineering Department, 2018, pp. 1-174, Nathan’s Mobility Device.
[9] Richard, Everett. Foldable Jogging Stroller. 2004.
[10] Liu Dong Shuei. Adjustable mechanism for a seat back of a stroller. 2014
[11] Shun-Min Chen, Ru-Yi Li. Single-Hand-Operated Actuating Mechanism for a Foldable Stroller. 19 July 2007.
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[12] Tsui, Leslie, and Christopher Tsui. Head Rest And Restraint Assembly. No. US5806933A, 1996.
[13] Knasbauch, Charles T, et al. Wheeled Health Care Chair. 2 Feb. 1999.
[14] “Mechanics.” Collapsible: the Genius of Space-Saving Design, by Per Mollerup, Chronicle Books, 2001, pp. 30–168.
[15] Vandermark, Robert. "Opportunities For The Titanium Industry In Bicycles And Wheelchairs". Vol 49, no. 6, 1997, pp. 24-27. Materials Science And Engineering Database, Accessed 17 Oct 2018.
[16] "Online Materials Information Resource - Matweb". Matweb.Com, 2018, http://www.matweb.com/. Accessed 26 Oct 2018.
[17] Parent, Frederic et al. "EVALUATION OF THE NEW FLEXIBLE CONTOUR
BACKREST FOR WHEELCHAIRS". Rehabilitation Research & Development, vol 37, no. 3, 2000, pp. 325-334. Ebscohost, Accessed 17 Oct 2018.
[18] Nagatama, Arga. “AMEVSC-03-03e.” Academia.edu, www.academia.edu/13477979/AMEVSC-03-03e
[19] ASTM International. F833-15 Standard Consumer Safety Performance Specification for Carriages and Strollers. West Conshohocken, PA, 2015. Web. 24 Oct 2018.
[20] Tzeren, Aydin. Human Body Dynamics: Classical Mechanics And Human Movement.
Springer, 2013.
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HOW: Engineering Specifications (Tests)
WHAT:
Front Wheel Degrees of Rotation
11 12 Fit in the trunk of her car
Static Friction Test (brakes) Jonathon's Reaction Weight (lbs) # of Steps to Fold Folded Dims (in) Angle Range from Seat to Backrest (°) Load Capacity (lbs) Product Lifetime # of Pinch Points
Direction of Improvement Column #
Less than 40 lbs 5 folding steps Trunk Dimensions 90 - 180 degrees 150 lbs 3 years 0
▼1 2 3
○
14 15 16
▼ ◇ ◇ ▲ ◇
44.32 112 199.8 94.65 79.55 146.3 82.35 52.25 96.57
150 lbs on 15% incline Happy 45°
80.12
4% 11% 8%
20% 10% 8% 15% 8% 5% 10%
1 2 3 4 5 6 7
Technical Importance Rating HOW MUCH: Target Values
Our Current Product Nina's Convaid Stroller Competitor #2: Product Name
5 0 5 5 5 2
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Appendix B - Benchmarks for Current Products
Product Weight
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Appendix C – Final Design Supporting Calculations and Analyses
Hand Calculations completed to verify the strength of the welds, bar stock on the horizontal bar used in the front wheel assembly, and uncertainty analysis for test procedure 1:
Bending Failure and Deflection Analysis:
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Weld Strength Analysis
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Uncertainty analysis conducted on test procedure 1
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Appendix D-1 – Design Hazard Checklist
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Appendix D-2 – Design Hazard Checklist
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Appendix E– Failure Modes and Effects Analysis
FMEA NO.:1Prepared by: Page 1 of 1Device Name:Jonathon's StrollerProduct/Service ApplicationDesign Responsibility:Review Date:
Function andPerformanceRequirement Potential Failure Mode Potential Effects of Failure
Severity
Potential Causes of Failure
Occurrence %
Criticality
Leg AbductordetachmentJon slides out3force13breaksJon slides out, user injury10impact110HarnessdetachmentJon falls out8force18breaksJon falls out8force18Seatdetachmentuser injury10weight110breaksuser injury10weight110Framebreaksstroller is out of use10impact110Wheels punctureunable to maneuver2sharp terrain48 High StrollersJonathon's Stroller2/6/2019
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Appendix F – Operator’s Manual
Jonathon’s Lightweight Stroller
Operator’s Manual
Contributors:
Morley Perrin Braeden Hammond
Reid Bartels Juan Rodriguez
A - 13 Wheels
There are two topics regarding the usage of the wheels on the stroller. These include filling the back wheels with air and protecting the structural integrity of the front wheel assembly.
How to re-pressurize the back wheels:
Tools/Equipment necessary: Standard bike pump with Schrader valve
1. Unscrew the cap from the valve on the tire. See Figure 1 to aid in locating the valve cap.
Figure 1. Location of the valve cap on the pneumatic back wheels.
2. With the lever on the bike pump down, press the head of the bike pump onto the valve on the wheel (Figure 2). With the head of the pump secured, lift the lever on the head of the pump
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Figure 2. Pictured is placing the head of the pump on the valve.
3. Lifting and pushing down on the handles of the pump, pressurize the tire to 30 psi.
4. Press down on the lever on the head of the pump, remove the head, and reinstall the valve cap.
Note: If you get to step 3 and air does not seem to be entering the tire, then repeat step 2 in order to properly locate and secure the pump onto the valve.
A - 15 Engaging the brake on the rear wheels:
1. With the stroller at a complete stop, with your foot, press down on the bar shown in Figure 3 to engage the brake.
Figure 3. Location of the bar that engages the rear wheel brake.
Note: If the bar does not initially engage into the brake, then rock the stroller forward and back while pressing down on the bar.
Protection of the front wheel assembly:
The front wheel assembly was designed to sustain loadings of 200 lbs. To avoid damage to the front wheel assembly, no weight exceeding this should be placed on the horizontal bar that the front wheels are attached to.
Warning! Do not step on, or place heavy objects on, the horizontal bar that the front wheels are attached to.
A - 16 Handling for Transportation
Transportation of the stroller has been streamlined by its ability to collapse. This section outlines the steps to safely collapse the stroller and how to maneuver it once it has been folded up.
Folding and Unfolding the stroller:
Prior to folding the stroller, make sure you are on relatively level ground and everything / everyone has been removed from the seat and basket. There are many pinch points during this process so make sure to keep your hands and other appendages only at the engagement points identified in the instructions.
1. Engage rear wheel brake.
2. Steady the stroller with your right hand on the handlebar and squeeze the lever on the left side of the stroller.
3. As you push forward with your right hand and allow the stroller to fold forward into its collapsed position release the lever, moving your left hand out of the way.
4. Locate the buckle and strap on the right side of the stroller as shown in Figure 4 5. Loop the strap under the bar that is directly beneath the buckle as shown in Figure 4 6. Connect the buckle to the strap this will allow transportation of the stroller. This will
prevent the stroller from reverting back to its unfolded position
Figure 4. Buckle and strap location on the stroller (shown left) and buckle strap when engaged (shown right)
Loading and Unloading the Stroller:
Loading and unloading the stroller into a car trunk should be done with caution to avoid injury.
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1. Bend at the knees to grab the stroller with both hands. Place one hand on either side of the stroller to keep it balanced.
2. Keeping your core tight, lift the stroller 3. Carefully place it in the trunk
Leg Abductor Adjustment and Replacement
The leg abductor was manufactured so that it can be adjusted forwards and backwards along the seat to best fit Jonathon. To do this, use two hands to detach the Velcro underneath the seat of the stroller, as shown in Figure 5.
Figure 5. Detaching Velcro to aid in leg abductor adjustment.
Once the Velcro is detached, the leg abductor is free to move forwards and backwards. Move the leg abductor to the preferred position and then reapply the Velcro in the same manner it was detached. If the leg abductor deforms at any point from natural causes such as water damage or breaks for any other reason, detach the Velcro, lift the leg abductor off the seat, and take out the foam-covered wood block, as shown in Figure 6.
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Figure 6. Foam covered wood replacement for leg abductor.
When the leg abductor is removed, it can be easily replaced with a same size leg abductor.
Follow the manufacturing steps found in the final design report (Pgs. 46-47) to build a new leg abductor and then insert back in the pouch, place sleeves through the slots in the bottom of the seat and re-attach the Velcro.
Warning! Do not insert an item that is not the leg abductor into the sleeve. This cause discomfort for the rider and can potentially damage the sleeve.
General Use
The rider of the stroller shall not exceed 150 lbs. Any riders over 150 lbs. will cause excessive wear, and stress on the stroller and could create unstable conditions.
Stroller is to be used only at walking speeds. Stroller is not intended for use while jogging, skating, etc.
Never allow the stroller to be used as a toy. Avoid any jerk, shake, or erratic movements while pushing.
Avoid serious injury from falling or sliding out. Always secure the rider with the harness.
To prevent a hazardous, unstable condition do no place more than 15 lbs. on the handlebar.
The parking should be engaged when the stroller is stopped and for placing and removing the rider.
Never use stroller on stairs or escalators. One may lose control of the stroller or the rider may fall out. Use extra care when moving over a step or a curb.
Discontinue use of the stroller if parts have become damaged or broken.
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Appendix G – Bill of Materials
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Appendix H-1 – Drawing Package
Full Stroller Assembly
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Appendix H-2 – Front Wheel Assembly
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Appendix H-3 – Front Wheel Assembly (Exploded View)
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Appendix H-4 – Front Wheel Mount
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Appendix H-5 – Leg Abductor Assembly
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Appendix H-6 – Wood Block
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Appendix H-7 – Foam Core
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Appendix I – Design Verification Plan
Des ign Ver ific atio n R epo rt
Quantity TypeStartCompletion 1Tipping TestMeasure load on the handle bars that it takes to tip the stroller. Over 15 poundsPV3T4/1/20194/1/2019Braeden 2Lean TestUsing various inclines, measure max inlcline until stroller tips backwards on its own. Over 10 degreesPV3T4/1/20194/1/2019Braeden 3Volume Test See if the stroller while fully folded fits in the trunk of Nina's Chrysler 300PassPV1T5/1/20195/1/2019Juan 4Weight TestMeasure weight of stroller on a scaleUnder 40 pounds PV1T5/1/20195/1/2019Juan 5Folding Test
Ensure that any stroller modifications does not interfere with the collapsing mechanism of the stroller PassPV1T5/1/20195/1/2019Reid 6Sizing TestMake sure the harness/seat/leg abductor fit JonathonPassDV1T3/20/20193/20/2019Reid/JuanPass20 7Push Test
Test to insure the leg abductor can withstand Jonathon's planking force and he will not slide over the top of itpass at 3" and belowDV3T3/13/20193/13/2019MorleyPass10 8Velcro Test
Test to insure velcro connecting the leg abductor to the seat is strong enough to withstand Jonathon's planking forcePass with team memberDV3T3/1/20193/1/2019Reid/JuanPass30 9Overall Seat Test
Make sure the seat fabric, mesh, harness, and leg abductor can withstand bodily forces such as planking Pass with team memberPV2T5/1/20195/1/2019Morley/Reid
Tes t Pl an Tes t Re por t
Test StageSpecification & Test MethodTest NoTest ResponsibilityTest ResultSamplesTiming Quanity PassQuantity FailNotesAcceptance CriteriaTest DescriptionA - 28
Appendix J – Gantt Chart
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Appendix K-1 – Product Pages
Phifertex Mesh for the Seat’s Sidewalls
Picture taken at the vendor of the mesh, Quality Fabrics in San Luis Obispo, CA
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Appendix K-2 – Aluminum Stock for Front Wheel Mount
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Appendix K-3 – Caster Wheels
Quickie caster wheel with horizontal bar mount purchased off of eBay. Typical use is for Quickie wheelchairs.
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Appendix K-4 – Neoprene Foam
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