Design Principles and Practice - Coursework Example

This report is aimed at designing a jogging stroller for parents wishing to run while taking care of their infants. The product design willensure compliance with aesthetic, economic, statutory requirements as well as best design practices. Contents Introduction Jogging strollers are a handy running accessory especially for parents and baby sitters who do not wish to be restricted by caring for little children. The infant is placed inside a jogging stroller and the runner can then push or pull the stroller to carry the weight of the infant. Other than running, the jogging stroller can also be used to transport infants over commutes because the strollers are safe by design and requirement. This report examines all major design principles and practices required to create an innovative jogging stroller. Pahl and Beitz model Market Research on Existing Devices Market research indicated that myriad companies are already manufacturing jogging strollers. The current models that are available are able to satisfy most customer requirements. Generally jogging strollers are three wheeled, vary in weight from manufacturer to manufacturer and could be foldable or fixed. (Jogging Stroller, 2011) Safety is mandatory. Seating capacity could be for one or two infants who are placed either inline or abreast on the jogging stroller as per design. Moreover, the wheels on jogging strollers are roughly 18 inches in diameter. Harnesses are also included so that the runner may tie themselves into the jogging stroller. (Luff, 2011) However, other models are available that can be pushed around. The handle bars are adjustable and storage bins have been provided to store infant accessories. (Running Advisor, 2011) Standard bare bones jogging strollers (one seat version on left and two seat version on right) Market Research from Potential Users In order to ascertain the requirements of potential users, I went to parks around the campus and interviewed parents using jogging strollers. This helped to precipitate both the good points and bad points in the jogging strollers. Most users related that the three wheel design was stable enough to prevent overturning. Wheel size is also acceptable at around 18 inches. In my survey I found only a very few jogging strollers with harnesses. Those who were using harnesses were not happy with their performance as the claimed that harnesses restricted use and caused unwanted strain. Others who did not use harnesses said that they preferred to push jogging strollers around than become cart horses. This implies that as per aesthetics people prefer jogging strollers that can be pushed around. Moreover, when people were inquired about the appearance of the jogging stroller most people believed that the bare bones jogging strollers looked ugly. Most expressed a desire to purchase better looking models. Therefore, there exists a potential to sell a slightly expensive jogging stroller if it is made beautiful enough. The desire to have more aesthetically pleasing jogging strollers was most common amongst younger mothers (20 to 30 years old). The older mothers (30 and above) were mostly indifferent to how the jogging stroller looked. Market Research (British and European Union Standards) Under British regulations both new and used prams and push chairs must adhere to BS 7409:1996 or equivalently to BS EN 1888:2003 (equivalent European standard). This standard is largely concerned with safety of infants in the prams and push chairs category and sets guidelines for rollover and other similar incident prevention. Another applicable standard is BS 1877-10 which specifies the various kinds of mattresses and bumpers that are used in perambulators for children. The mattresses must allow for a certain degree of softness as well as ensure circulation of air to ensure that the child is comfortable even during long walks and runs under the sun. Another important device is the safety harness in use on push chairs which is covered by BS 6684. (BSI, 2005) Furthermore, the material used to construct children’s strollers and carriages must comply with ASTM F833-11. This standard ensures that only a specified kind of metal is used to construct things such as prams, push chairs, bicycles and tricycles for kids. This metallic composition is not harmful to children even if they tend to put it in their mouth. (ASTM, 2011) Also BS 1717-88 will have to be used for wheel specifications for wheels used on the stroller. (BSI, 1988) Ergonomic Constraints There are two potential users of the jogging stroller. One is the infant inside the stroller and the second is the person pushing the stroller. Ergonomics for both must be considered separately. The infant inside the stroller must be harnessed inside the stroller. The depth of the stroller should be such that when the stroller overturns, the infant is not impacted on the road or on the structure of the stroller. This can be ensured by providing large clearances between the infant’s seating area and the edges of the stroller. Moreover, the child should also be comfortably seated and the stroller’s sitting pad must be reclined to admit the child’s body posture. The fabric used must be washable so that if the infant excretes, the fabric could be washed. In case the fabric is not washed then the infant may be susceptible to disease the next time the infant is seated in the stroller. The other concern is for the person pushing the stroller. For one thing, the dimensions of the stroller must conform to the body height and width of the person. Secondly, the stroller’s push bar ought to be adjustable. The use of harnesses could be looked into as well. The normal load exerted by an average adult on a cylindrical bar (Government Consumer Safety Research, 2011) would be used to ascertain design. Furthermore, the manufacturing process should not leave behind jagged ends that may cause either infant or adult any harm. Key Areas of Research The research will have to focus largely upon the safety and ergonomic concerns. Moreover, the overall market appeal must be investigated too. Similarly, design considerations will also have to be researched to ensure that the final product can enter the market feasibly. Product Design Specification 1.0 Foreword A jogging stroller is used by people who are running or jogging while caring for infants. The stroller must be sturdy enough to carry one infant in comfort. The design should be adjustable so that different sized people can use it. The device must be ergonomically optimised for both the child and the runner. As the stroller would be used on roads and paths alike, it should have sufficient ground clearance to aid navigation. 2.0 Scope of Specification This specification is meant to cover the following aspects of the jogging stroller’s design: 1. Number of infants carried; 2. Product attributes; 3. Ergonomic concerns. 3.0 Definitions 3.1 Terminology Jogging stroller: any device of capable of carrying one or two infants during a jogging or running routine Harness: any device used to limit human movement that has been designed to enhance safety Mattress: any kind or brand of foam used to construct seating devices 3.2 Symbols and Abbreviations BS: British Standard ASTM: American Society for Testing of Materials DF: Degrees of Freedom FOS: Factor of Safety 4.0 Functional Requirements The jogging stroller must be able to transport one infant up to the age of 4 years; Only one adult would be able to push the jogging stroller; Should be as light as possible; Wheels should be large enough to navigate kerbs. 5.0 Safety The jogging stroller must be stable enough to avoid over turning; In case of overturning, the infant must be protected using: Harnesses; Judicious clearance from edges of jogging stroller. 6.0 Ergonomics The maximum weight of the unloaded stroller should be no more than 20 kg; Harnesses for adults should not be used as their long term affects are not known; The push bar of the stroller should be adjustable for various sized persons; The seating area for the infant must be comfortable and well ventilated; All fabric used must be washable; The push bar should be capable of resisting horizontal and vertical DF of 20 for each hand on the push bar. (See Standard 8.6, page 31); The elbow height for the push bar should be around 42 inches (See Standard 8.6, page 31); Paint used should be indigestible and not flammable. 7.0 Design 7.1 Aesthetics The product should be pleasing to look at and should incorporate any design other than a bare bones structure with visible structural members. 7.2 Overall Unloaded Weight The jogging stroller must not possess an unloaded weight of more than 20 kg with all components installed. 7.3 Carried Load The jogging stroller will carry the weight of a typical 4 year old child at most which is taken as 20 kg as per Standard 8.6 listed below. 7.4 Dimensions The jogging stroller must not exceed the following dimensions: Height 42 inches (as per Standard 8.6 listed below) Length 24 inches Breadth 18 inches Wheel 18 inches 7.5 Mechanical Design Considerations The FOS need not be more than 2.5 at best as there are no vibrating loads present. Weight has to be kept as low as possible. 7.6 Manufacturing Processes Considerations Use of structural members must be minimised; All structural members must conform to ASTM F833-11 (listed as Standard 8.5 below); Structural members will be welded as per the satisfaction levels of ASME Section IX; Fibreglass may be used to cover the body of the jogging stroller for visual appeal; Exposure to harmful substances that must be used must be minimised such as grease. 8.0 Standards 8.1 BS 7409:1996 or EN 1888:2003 8.2 BS 1877-10 8.3 BS 6684 8.4 BS 1717-88 8.5 ASTM F833-11 8.6 Strength Data for Design Safety (Phase I) 8.7 Strength Data for Design Safety (Phase II) 9.0 Cost Cost may be minimised through optimisation but cost cutting should not compromise safety in any possible manner. Overall cost of product should not exceed 150 GBP and should not be lower than 100 GBP. 10.0 References BS 7409: 1996 Guidelines on carriers and perambulators for children BS 1877-10 Mattresses and bumpers for children BS 6684: Safety harnesses BS 1717-88 Cycle and motorcycle tyre guidelines ASTM F833-11 Structural member for use in children products Strength Data for Design Safety (Phase I), Department of Trade and Industry Strength Data for Design Safety (Phase II), Department of Trade and Industry Brainstorming Concepts Brainstorming was done to elucidate various design ideas for the jogging stroller. These ideas are listed below: Two concepts existed as per drive train Three wheelers Four wheelers Aesthetic design Bare bones (structural members visible) Bare bones and fibre glass Fibre glass only Suspension Shock absorbers or springs (or a combination in the drive train) Shocks absorbed through the mattress employed Safety Use of harness Placement of child in middle such that if the jogging stroller turns over then the child would be protected best Ergonomic considerations Height of adult Ability to adjust push bar versus fixed push bar Push bar versus harness Final Concept Selection using Selection Matrix Aspect Choices Chosen Option Reason Drive Train 3 wheeler 4 wheeler 3 wheeler Just as stable as a 4 wheeler on low speeds. Aesthetics bare bones bare bones and fibre glass mix fibre glass only Fibre glass only increases aesthetic appeal covers up structural members so reduces risk to infants Suspension shocks and springs in drive train mattress shock absorption Mattress shock absorption Springs and shocks too complicated and expensive to implement. Safety use of harness child placed in middle Both Safety must be maximised. Ergonomics push bar harness Push bar Aesthetic as well as ergonomic concerns. The use of a harness to pull around 40 kg of weight by an adult may have consequences for the spine. Drawing Package as per BS8888 Attached Cost Breakdown The cost for the jogging stroller is listed below: structural members cost 20 GBP structural members welding 15 GBP mattress 5 GBP wheels and axle assembly 15 GBP fibre glass covering 30 GBP nuts and bolts 5 GBP harness 10 GBP fabric 10 GBP Total 110 GBP A fibre glass guide made out of wood for creating the fibre glass shell will also be required. Consultation with a few fibre glass workers revealed that such a guide would cost around 1000 to 1100 GBP. This would be a onetime cost and would serve the entire manufacturing life of this product. Therefore, the initial high cost would be offset by production. Discussion of Final Design The final design is visually appealing. This will ensure that it will have a good chance at selling in the market as indicated by research above. Moreover, the cost of this product is 110 GBP and it can easily be sold within the 150 GBP bracket. Other existing devices are similarly priced with prices beginning at 105 GBP for bare bones models although cheaper models and used models can be bought for as low as 40 GBP. (Austin, 2011) However, the visual appeal is reason enough for this design of the jogging stroller to make headway into the current market. The materials in use are both safe and conform to standards (ASTM F833-11). Plus other relevant British and international standards are satisfied by this product design. These standards are listed above in the standards section as well as in the Section 8.0 of the product design specifications. Ergonomically the jogging stroller has been configured to suit both the infant and the adult using it. Therefore, the jogging stroller has a good chance at satisfying core customer needs. Consultation with potential customers has further helped to clarify concepts that will work and are preferred. Bibliography ASTM, 2011. ASTM F833 - 11 Standard Consumer Safety Performance Specification for Carriages and Strollers. [Online] Available at: HYPERLINK "http://www.astm.org/Standards/F833.htm" http://www.astm.org/Standards/F833.htm [Accessed 20 July 2011]. Austin, P.D., 2011. Strollers. [Online] Available at: HYPERLINK "http://www.autism-pdd.net/testdump/test8028.htm" http://www.autism-pdd.net/testdump/test8028.htm [Accessed 22 July 2011]. BSI, 1988. BS 1717-88 for Steel Tubes for Cycle and Motorcycle Purposes. [Online] Available at: HYPERLINK "http://www.ukrtop.info/standard/BS/BS_1717.pdf" http://www.ukrtop.info/standard/BS/BS_1717.pdf [Accessed 20 July 2011]. BSI, 2005. Children’s transport Standards. [Online] Available at: HYPERLINK "http://www.bsieducation.org/Education/14-19/topic-areas/childrens-transport/childrens-transport-standards.shtml" http://www.bsieducation.org/Education/14-19/topic-areas/childrens-transport/childrens-transport-standards.shtml [Accessed 20 July 2011]. Government Consumer Safety Research, 2011. Strength Data for Design Safety - Phase I. [Online] Department of Trade and Industry Available at: HYPERLINK "http://webarchive.nationalarchives.gov.uk/+/http://www.berr.gov.uk/files/file21830.pdf" http://webarchive.nationalarchives.gov.uk/+/http://www.berr.gov.uk/files/file21830.pdf [Accessed 20 July 2011]. Jogging Stroller, 2011. Stroller Reviews. [Online] Available at: HYPERLINK "http://www.joggingstroller.com/home.jsp" http://www.joggingstroller.com/home.jsp [Accessed 23 July 2011]. Luff, C., 2011. Top Jogging Strollers. [Online] Available at: HYPERLINK "http://running.about.com/od/shoesapparelandgear/tp/bestjoggingstrollers.htm" http://running.about.com/od/shoesapparelandgear/tp/bestjoggingstrollers.htm [Accessed 23 July 2011]. Running Advisor, 2011. Running Accesories | Running Gear. [Online] Available at: HYPERLINK "http://www.therunningadvisor.com/Running_Accessories.html" \l "strollers" http://www.therunningadvisor.com/Running_Accessories.html#strollers [Accessed 19 July 2011]. Read More