Capstone Design ME 4182
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Date Created: 11/02/15
ME4182 Capstone Design KayaKaddy December 151 2004 Instructor Harvey Lipkin Teaching Assistant Temsin Sapsaman Team Members Richard Dn39ftmeier Jennifer Duchac Stefanie Freeman Bryan Lawler Matthew Wooten Executive Summary Launching and recovering a large kayak from a dock can be a daunting task for a smaller person Not only does the typical kayak weigh 601bs but it is also roughly 12 feet in length With this in mind the purpose of this project was to design and fabricate a caddy capable of launching and recovering a kayak from a dock in a safe and easy manner There were siX main design criteria that had to be met and are outlined as follows The caddy had to be mobile Dock use typically varies with the seasons and because of this the caddy should be mobile allowing for changes in dock use The caddy must not damage the dock Docks are expensive to build and also to repair The final design must require minimal user strength The purpose is to aid a smaller person in launching and recovering a kayak from a dock The caddy must be able to deal with a 601b 12 kayak The design must be easy to use The procedure should be relatively short Most importantly the final caddy design must be safe to use Having met each of the design criteria outlined a final design was selected and a prototype was built The purpose of the prototype was to quickly prove the validity of the final design while minimizing time and material inputs Due to this there were some minor changes in the prototype that are not re ected in the final design The design process selected final design the prototype built and continuing suggestions will be covered with greater detail in later sections of this paper Table of Contents r J 1 Design 39 J quot 2 Component Subsystem Description 3 Frame 4 Mobility 6 Boat Attachment 8 Aomminn 10 Design Selection and Method 12 Alternative Subsystem r and r 39 Designs 12 Design Selection Method 17 0 39 39 quot 19 Material Selection Analysis 19 Weight of Design 20 Stress 39 39 quot 21 Spring nlonlminn 21 Prototype Testing 22 24 Design Conclusions Introduction The purpose of this project was to design a caddy capable of relocating launching and recovering a kayak from a dock in a safe and easy manner Additionally a prototype was to be built to act as a proof of concept There were several problems that had to be dealt with in order to arrive at an acceptable nal design One of the most basic requirements was that the nal caddy design be mobile The use of a dock often varies with the season From summer picnics and boat outings to dry storage in the winter the caddy must allow for changes in dock use Many options were considered meeting that would meet the given task including a rail system wheels or even a hovering ability Additionally docks are expensive to build as well as repair Because of this it was necessary that the caddy not damage the dock in any way No portion of the nal design should bolt to or cut into the dock During the initial design phase it was mandated that the caddy should be easily operated by a 100 lb female Thus the nal design should require minimal user strength in operation Any concepts that fell short of this requirement were discarded and attempts were made to maximize mechanical advantage in the remaining options Also it was determined that the caddy should be robust and capable of launching and recovering a 12 60 lb kayak which is the typical size of arecreational kayak The nal design also must be easy to use and during the design process the steps necessary to use the product were kept in mind If the use of the product were too complex a customer would probably prefer to launch and recover the kayak by hand Most importantly the nal caddy design must be safe to operate In an aquatic environment user safety must be given more thought than if the device was to be used in the absence of water A wet kayak caddy or dock could lead to hazardous operating conditions The moment arm of the design must be minimized to reduce the likelihood of the caddy ipping off the dock and into the water Material choices that lent themselves to durability and good weathering characteristics were also valuable Also many moving parts could increase the chances of user injury Design Introduction A CAD representation of the nal caddy design the KayaKaddy is shown below in Figure l The nal design incorporates ve subsystems which enables it to reposition launch and recover a kayak from a oating dock The subsystems consist of frame mobility boat attachment positioninglifting and actuation Figure l 7 The KayaKaddy 2 In addition to the final design a picture of the built prototype of the KayaKaddy is shown below in Figure 2 Figure 2 7 Final KayaKaddy Prototype with Kayak The prototype serves as a proof of concept for the KayaKaddy To do this not all design cues had to be followed exactly Some changes were made to save time and money in the prototype construction These changes will be discussed further in the ComponentSubsystem Description Component Subsystem Description As mentioned previously five subsystems are integrated to form the KayaKaddy frame mobility boat attachment positioninglifting and actuation Each of the subsystems tackles a portion of the design criteria outlined in the introduction and each will be discussed in detail below m The largest subsystem of the KayaKaddy design is the frame The frame acts as a base to which the other subsystems either connect to or function from as well as to provide a stable foundation for the moving launching and recovering of a kayak Figure 3 displays the nal KayaKaddy frame plus attached mobility subsystem Frame Subsystem Attached Roaming Subsystem Figure 3 7 Frame and Attached Roaming Subsystem One of the rst problems encountered in the frame design was material selection and subsequent weight issues The frame should be heavy enough to provide a stable base yet light enough to allow for easy mobility In addition the consumer should be able to easily assemble the KayaKaddy The end result was a 4 X5 angle iron frame The frame is built from two 48 bars of angle iron ve 60 bars four comer brackets one Plexiglas sheet two handlebars and their associated brackets The angle iron bolts into the comer brackets as shown below in Figure 4 to create the lower portion of the frame Figure 4 7 Comer Bracket Usage Additionally the comer brackets provide a mounting surface for the Plexiglas cover as well as the casters from the mobility subsystem Two types of handlebars are used in the frame The rear handlebar is mainly used for steering of the caddy while relocating the KayaKaddy while forward handlebars support the actuation subsystem and give support to the user Both handlebars are mounted using the triangular mounting bracket shown in Figure 5 Figure 5 7 Triangular Handlebar Mounting Bracket To address the issue of ipping the caddy while in use it was desired that the moment arm created in carrying a kayak be minimized This was accomplished in keeping the kayak as close to the dock as possible Both the material selection and the arne construction were in uenced by this consideration The surface of the frame of the caddy is 6 from the dock Also requiring the user to stand on the rear of the KayaKaddy provides a counterbalance to the kayak s weight and further prevents ipping The prototype uses similar principles However since it only functions as a proof of concept and does not require the same durability changes were made to reduce building time and cost As shown in Figure 2 the nal prototype uses only one handle bar and has a arne of 2 x2 wood To save additional costs medium density berboard replaced Plexiglas as the ramp covering material Mobilig The mobility subsystem is designed to meet the mobility requirements of the nal caddy design This subsystem includes four commercially available casters two of which are rotating casters A picture of the two types of roaming subsystem components offered by Castercitycom is shown below in Figure 5 The combination of rigid and rotating casters allows for higher mobility and control of the KayaKaddy Additionally a wheelbased system assures a lesser chance of damage to the dock Swivel Locking Caster Unlocked Rigid Caster Figure 5 rRoaming Subsystem Components When using a wheel based mobility system preventing the caddy from moving while in use was imperative To address this rotating casters with wheel locks were used These casters can be turned perpendicular to potential motion as well as locked to prevent rolling The casters uin r r i e rather than the ngidrotating combination This selection was due to availability and pricing provided by a local Home Depot W The prirnary iunetion of the boat attaehrnent suhsystern is to serve as a eonneetion between the kayak and the KayaKaddy during launehing and recovery The boat attaehnent suhsystern eonsists oftwo rnetal clips which are attached to the end of two 25 nylon ropes nu i i tit urri u the aetuation and the positioninglining suhsysterns the boat attaehrnent suhsystern works to Figure 7 a Boat Attaehrnent Subsystem showing Nylon Rope Running to wineh and Metal Clip Attached to Kayak one ofthe largest problems in using separate lines to guide the hawk during launehing and recovering is the possibility ofline entanglement The nal design ealls for eyehooks to he rnounted to the forward handlehar of the frame to guide the two nylon ropes The eyehooks prevent the two lines from heeorning snared as well as guide thern together to the actuation suhsystem PositioningLifting A method was designed to provide a guide to and from the water This is accomplished by the positioninglifting subsystem which employs a 2 X2 berglass frame with Plexiglas cover to act as a ramp The subsystem is attached to the frame subsystem by two hinges and is assisted in motion by a torsion spring The positioninglifting subsystem is shown below in Figure 8 Figure 8 7 PositioningLi ing Subsystem Interference between the positioninglifting subsystem s berglass frame and the frame subsystem could be a signi cant problem if the gap between the frame and ramp is not large enough A ttype gate hinge shown below in Figure 9 allows for a larger gap between the ramp frame and the body frame than other hinge types Figure 9 e Ttype Gate Hinge The weight of the positioninglilting subsysta39n must be minimized In retrieving the ramp the usequot is limited in the distance at which a force can be applied to lift the ramp and thus a C 39 394 39 39 39 quot 39 thedesigncallsfora torsion 39 39 39 h 39 39 39 and frame W 0mm pins for the gate hinges would replaced with one 36 long pin on the new pin a 30 torsion spring would mounted The spring applies mough force to aid the usequot in lifting the in i i i r y The positioninglilting subsysta39n of the prototype is Va39y similar to the nal design Howevm t r r Actuation The artuatinn quot amechanical 4 39 in supplying the required force to bring the kayak up the ramp The Kayamddy design speci es the use of a ratcheting 6001b 41 Fulton Marine winch shown below in Figure 10 Figure 10 Fulton Marine Winch The winch is the smallest offered on the market and is available from many suppliers A similar winch offered by Bass Pro Shop with a gear ratio of 31 was used for the prototype The actuation subsystem works in conjunction with the boat attachment and positioninglifting subsystems The winch reels in the nylon line that is connected to the kayak and in doing this the kayak is pulled up the ramp onto the body frame Two main concerns when using a winch are the possibility of bunching of the line or of the line jumping the winch To deal with this problem a third eyehook was placed directly in front of the line spool to guide the lines to a point as close as possible to the winch The same setup is used in the prototype and a picture is shown below in Figure 11 Figure l l 7 Eyehook Feed to Winch Design Selection and Method Several 39 design selection The nal KayaKaddy design is a combination of the best and most feasible of these altematives These individually selected components were then compiled to result in the nal design selection The following sections will cover altematives to the selected subsystems conceptual designs the selection method and its possible errors Alternative Sub stem Components and Concgptual Designs Each of the five subsystems has its own unique function and set of needs and in order to perform each function several methods or were explored For each ofthe subsystems there were Figure 12 the conceptual altematjves to the boat attachment subsystem are shown in Figure 13 Figure 14 displays the ve alternatives to the positioningiining subsystem and Figure 15 gives wheels and feet fuur Casters xed Wheels and casiers g wheels on a track hover Cra Figure 12 Mobility Subsystem Concepts 0 pla orm claws rope with Chps Figure 13 7 Boat Attachment Subsystem Concepts 13 I III telescoping Imam x ever mm ruHers frame sllde Wlm wlnch gure 14 r PostuontngLtmng Subsystem Concepts 1 pump gravity WW fan etecmc motor gure 15 rAcmauon Subsystem Concepts the KayaKaddy was created These designs are shown below n thures 16720 Fxgure 17 7 Elecm m Desxgn HAND LE FOLDING FRAME Figure 18 7 Rigid Caddy Design LOCKING M WHEELS ifquot DOCK WATE R Figure 19 7 Telescoping Lift Design HANDLE BARS WATER Frgure 20 eRolhhg on the Rrver Desrgh Preeursor to the KayaKaddy Hatmg eomprled many possrble ehorees for each subsystem rhto the ve altemauve desrghs huh F Desrgh Seleeuoh Method The method of seleetroh used for thrs project was a seleeuoh matnx shown below m Table 1 Table 17 Selecuon Mamx Catanat tm Swmgmg Arms Eteeme tm mam Caddy Tetesenpmg tm h was rated on a scale ofl w 3 3 bemg best for a mulmude of functlons Each of the functlons was wexghted usmg the pair wxse method Fuheuons of the hxghest Importance t 1 taken for h A A score t H was the best choice The resulting selected design was Rolling on the River the foundation for the KayaKaddy design After taking into account many factors such as ease of manufacture and price of raw materials Rolling on the River slowly began to take shape as the KayaKaddy Calculations In addition to designing building and testing the KayaKaddy s prototype calculations were run to verify or provide alternatives to concepts during the design process Material selection analysis was used to provide suggestions for what both the ramp and the caddy frame should be made from commercially Calculations of the KayaKaddy weight were run and used in further calculations of stresses that the caddy may encounter in typical use With calculated stresses a torsion spring was sized These calculations are outlined in more detail as follows Material Selection Analysis A material selection process was conducted to determine what materials the caddy should be constructed from It was determined that the body of the caddy should be cheap and strong It is not desirable for the body of the caddy to be excessively light since extra counterweight may be needed to avoid tipping of the caddy The material index for a cheap strong beam is given by Equation 1 1 where M is the material index 039 f is the strength of the material and C R p is a relative cost term The materials which yielded the highest value forM were wood and cast irons Wood was dismissed because of environmental effects The material selection for the body of the caddy is a 19 coated cast iron which will reduce the risk of rusting Angle iron because of its availability was a good choice The ramp of the caddy should be strong and light to assist the user in pulling the ramp out of the water The material index for a light strong beam is given by Equation 2 y 039 f3 M 2 p where M is the material index 039 f is the strength of the material and p is density The materials which yielded the highest material index were wood carbonfiber reinforced polymer and glassfiber reinforced polymer berglass Wood was again dismissed due to environmental effects and carbonfiber reinforced polymer was rejected due to high cost approximately 40 times more expensive than fiberglass The material choice for the ramp became fiberglass Weight of Design The ramp is to be manufactured using 2 inch square tube fiberglass with 18 inch wall thickness The ramp will be covered with a strip of Plexiglas with 18 inch thickness Given a fiberglass density of 0061 lbin3 a Plexiglas density of 0043 lbin3 approximately 5 lbs of otation and 2 lbs of fasteners the total weight of the ramp is 399 lbs The body of the caddy is to be manufactured using 1 inch angle iron with a thickness of 18 inch Given a density of 489 lbft3 the total weight of the body is 80 lbs Therefore the total weight ofthe design will be approximately 120 lbs 20 Stress Calculations Calculations were performed to ensure that the selected materials and crosssectional sizes were sufficient to prevent failure of the caddy The maximum moment in the body of the caddy was determined to be located in the center of the frame of the body and was calculated to be 895 ftlb The maximum stress in the frame can then be calculated using Equation 3 M y max max 3 where arm is the maximum stress found in the beam M max is the maximum bending moment in the beam ymax is the maximum distance in the cross section from the neutral axis and I is the moment of inertia for the cross section Given the angled cross section of the cast iron beams ymax is 1 inch and I was calculated using the parallel axis theorem to be 00808 in4 These values produce a maximum bending stress of 133 kpsi which is considerably below the maximum tensile strength of cast iron of 22 kpsi The maximum bending moment in the ramp was determined to be located at the hinge connecting the ramp to the body of the caddy and was calculated to be 887 ftlb Given the square tube cross section of the fiberglass ramp ymax is 1 inch and I was calculated to be 2503 in4 This yields a maximum bending stress of 1595 kpsi well below the maximum tensile stress of fiberglass which is in the range of 7 kpsi Materials chosen for both the caddy and ramp frame were shown to be sufficient Spring Calculations A torsion spring was sized to assist the user in lifting the ramp out of the water and returning it to the resting position The ramp has a full range of rotation of 180 degrees from the 21 water to the resting position against the handlebars It is not desirable for the torsion spring to be active throughout this full range of motion since the user will not need the spring for assistance once the ramp has been lifted perpendicular to the body of the caddy Therefore the spring was sized such that it would be active through 140 degrees of rotation As calculated previously the ramp weighs 40 lbs which produces a moment of 100 ftlb about the ramp It was assumed the user would be easily capable of applying a 10 lb force at a distance of 15 ft from the edge of the dock This force creates a moment of 15 ftlb about the hinge A moment balance is necessary to determine the moment needed from the spring to bring the ramp out of the water Equation 4 gives the moment balance M MS MR 4 where M h is the moment applied by the human operator 15 ftlb M S is the moment supplied by the spring and M R is the required moment to lift the ramp out of the water 100 ftlb This leaves 85 ftlb of torque unaccounted for in the moment balance Equation 5 was used to determine the required spring rate in order to produce the moment desired k 5 where k is the required spring rate M is the required moment and GM is the range of motion of the spring 140 degrees Solution of the equation yields a desired spring rate of 0606 9 Prototype Testing In addition to calculation a prototype of the KayaKaddy was built to be tested as a proof of concept Cheaper materials were substituted for the angle iron and fiberglass suggested for 22 the nal commercial product and a rear set of handlebars were left off of the model The completed prototype with kayak is shown in Figure 2 It needed to be known of the KayaKaddy design would be capable of launching and recovering a full size kayak In particular there was a concern that if the kayak was not lined up perfectly with the KayaKaddy ramp that the design would fail to recover the boat from the water With the KayaKaddy mockup built the next step was testing The prototype and specified kayak were taken to a public dock on Lake Lanier in Buford Georgia The launching and recovering of the kayak was repeated several times with the use of the model Each test was successful Tests were run to note if an off center boat would result in recovery failure for the KayaKaddy All tests demonstrated that this would not be an issue In the water the boat was easily pulled into an in line position with the ramp using only the tension in the lines Tests showed the KayaKaddy prototype to be a robust and fairly easy to use design It became slightly more difficult to reel the boat onto the caddy frame once it was entirely out of the water However this difficulty could be compensated for with the selection of a higher gear ratio From the testing a complete set of instructions was made to guide a consumer through the process of launching and recovering a kayak The instructions are as follows Launching a Kayak from the KayaKaddy 1 Move the KayaKaddy and boat to a dock side 2 Step onto the KayaKaddy user platform disengage the winch clip so the winch may turn in any direction This will allow for slack in the lines 3 Using the forward handlebars as support push the Kayak off of the caddy frame and down the ramp 23 4 Use the oar to guide the kayak to a location on the dock adjacent to the KayaKaddy 5 Get in the boat as usual and unclip the lines Paddle away from the dock Recovering a Kayak from the Water 1 While in the water attach the lines to the kayak 2 Paddle the boat to a side of the dock adjacent to the KayaKaddy and get out of the boat 3 Using the oar gently push the kayak directly out from the dock not towards the KayaKaddy ramp 4 Step onto the KayaKaddy user platform and engage the winch clip to pull the boat in 5 Turn the winch and slowly reel in the kayak Stop turning the winch only when the kayak rests securely on the caddy frame 6 Step of the KayaKaddy user platform and move to the dock s edge Lift the ramp so that it covers the kayak This will secure the kayak 7 Move the KayaKaddy and boat to the desired storage location on the dock Design Conclusions Having gone through the design process the end result is the KayaKaddy consisting of 5 I L J t Each L J t or aids in the completion of a specific function as discussed previously The subsystems as a whole work to relocate launch and recover a recreational kayak Having defined the needs that each subsystem must meet 20 possible subsystem components were created From these ideas five conceptual designs were created The selection process graded each of the designs on their perceived success in a multitude of functions This selection process supports the eventual selection of the KayaKaddy design 24