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    Stair climbing hand truck Stair climbing hand truck Document Transcript

    • By: Group 7Stephen McLoughlinShiyas BasheerConor TiernanDue Date: 30thOctober 2012Dublin Institute of Technology Bolton St.Faculty of EngineeringHead of Department Supervisor DetailsDr. David Kennedy Mr. Gerard Nagle
    • 1 | P a g eTable of ContentsIntroduction.......................................................................................................................................5Objective.........................................................................................................................................5History.............................................................................................................................................5Benefits and Problems ..............................................................................................................6Design Objectives.............................................................................................................................7Marketability .....................................................................................................................................8Literature review:............................................................................................................................9The Cargo Master:.......................................................................................................................9Ease-E-Load Stair Climber Trolley Truck Carrying Capacity 150kg.................... 11Stair Robot SR Express........................................................................................................... 12Motor Type Selection .................................................................................................................. 16DC motor...................................................................................................................................... 16Advantages............................................................................................................................. 16Disadvantages....................................................................................................................... 16Applications where a DC motor is used:..................................................................... 16AC motor...................................................................................................................................... 16Advantages............................................................................................................................. 16Disadvantages....................................................................................................................... 17Applications where an AC motor is used:.................................................................. 17Two main types of DC motors............................................................................................. 17Brush:....................................................................................................................................... 17Brushless:............................................................................................................................... 18The Design....................................................................................................................................... 19Considerations taken while designing............................................................................. 19Mechanism....................................................................................................................................... 20Mechanism free body diagrams ......................................................................................... 21The free body diagram below illustrates the point where the most force isneeded to lift the trolley ................................................................................................... 21The free body diagram below illustrates the point where the second mostforce is needed to lift the trolley.................................................................................... 21The free body diagram below illustrates the point where the force is at thepoint where the trolley is on the next step and force is not needed anymore.................................................................................................................................................... 21
    • Initial design ................................................................................................................................... 21Final Design..................................................................................................................................... 25Base of the Trolley:.................................................................................................................. 26Arm Frame.................................................................................................................................. 27Arm frame (x2) (female part) ............................................................................................. 27Arm frame (x2)(male part) .................................................................................................. 28Arm frame total height: ......................................................................................................... 28Wheel Attachments................................................................................................................. 29Handle........................................................................................................................................... 30Rotational shaft with key way (for the motor and rotational support).............. 31Crank (which is attached to the motor to the rotational shaft) ............................. 33Large Rotational Arm (attached to wheels that sit on step) ................................... 34Wheels that sit on step........................................................................................................... 35Mechanism.................................................................................................................................. 36Stage 1: .................................................................................................................................... 36Stage 2: .................................................................................................................................... 36Stage 3: .................................................................................................................................... 37Stage 4: .................................................................................................................................... 37Final design of the mechanism: .......................................................................................... 38Supports (which support the motor, mechanism and rotational shafts)........... 39Ansys: ................................................................................................................................................ 39Material............................................................................................................................................. 41Price ............................................................................................................................................... 42Calculation....................................................................................................................................... 42Selection of motor.................................................................................................................... 42Selection of battery.................................................................................................................. 43Torsion in the arm........................................................................................................................ 45Selected Motor............................................................................................................................... 45Design problems....................................................................................................................... 48Weight and Cost........................................................................................................................ 48Selection of battery ...................................................................................................................... 49Battery Life Cycle ..................................................................................................................... 50Battery Size................................................................................................................................. 51Battery capacity retention characteristics:.................................................................... 52A 10Ah battery...................................................................................................................... 53Varying the speed ......................................................................................................................... 53
    • 3 | P a g eThe initial reaction .................................................................................................................. 53Pulse Width Modulation........................................................................................................ 54Speed controller............................................................................................................................ 61Recommendation:......................................................................................................................... 62Conclusion ....................................................................................................................................... 63Roles of the group......................................................................................................................... 64Stephen McLoughlin: .............................................................................................................. 64Tasks done:............................................................................................................................ 64Shiyas Basheer .......................................................................................................................... 64Task done:.............................................................................................................................. 64Conor Tiernan............................................................................................................................ 65Tasks done:............................................................................................................................ 65Reference ......................................................................................................................................... 66Appendix:......................................................................................................................................... 68Electrical stair climber assembly 2D drawing.............................................................. 68Base 2D drawing....................................................................................................................... 68Female tube 2D drawing ....................................................................................................... 69Male tube 2D drawing............................................................................................................ 69Pin 2D drawing.......................................................................................................................... 70Handle component 1 2D drawing...................................................................................... 70Handle component 2 2D drawing...................................................................................... 71Handle Component 3 2D drawing ..................................................................................... 71Main support 2D drawing..................................................................................................... 72Selected battery 2D drawing ............................................................................................... 72Overhead battery support .................................................................................................... 73Bottom of battery support 2D drawing........................................................................... 73Rotational Support 2D drawing.......................................................................................... 74Support for motor and rotational support 2D drawing ............................................ 74Overhead support for rotational support 2D drawing.............................................. 75Shaft for rotational support and motor 2D drawing .................................................. 75Rotational Arm of Motor 2D drawing............................................................................... 76Rotational arm for rotational support 2D drawing .................................................... 76Crank 2D drawing.................................................................................................................... 77Mechanism and motor support component 1 2D drawing...................................... 77Mechanism and motor support component 2 2D drawing...................................... 78Mechanism component 1 2D drawing ............................................................................. 78
    • Mechanism component 2 2D drawing ............................................................................. 79Mechanism component 3 2D drawing ............................................................................. 79Mechanism component 4 2D drawing ............................................................................. 80Mechanism component 5 2D drawing ............................................................................. 80Mechanism component 6 2D drawing ............................................................................. 81Wheel attachment component 1 2D drawing ............................................................... 81Wheel attachment component 2 2D drawing ............................................................... 82Wheel attachment component 3 2D drawing ............................................................... 82Wheel 2D drawing ................................................................................................................... 83Description...................................................................................................................................... 84Assumptions ................................................................................................................................... 85Model Information........................................................................................................................ 85Material Properties...................................................................................................................... 86Loads and Fixtures ....................................................................................................................... 87Mesh Information ......................................................................................................................... 88Mesh Information - Details................................................................................................... 88Study Results .................................................................................................................................. 90Conclusion ....................................................................................................................................... 93Ergonomics................................................................................................................................. 96
    • 5 | P a g eIntroduction“By definition the mechanical process defines a device that will carry out a specifiedtask when appropriate inputs are given. In reality, however, this definition provides atunnel-visioned view into the world of design. Mechanical engineers who designconsumer products have a twofold responsibility. In addition to designing functionalmachines, successful product designers must create devices that consumers will wantto purchase and use. While there are many possible factors that can make a productappealing to a buyer, perhaps the most important factor is an ability to make the userslife easier in some small way. In this way, product design is a service profession. Inthis design project we are trying to do the same, by designing a stair climbing handtruck that will ease anyone’s workload.”ObjectiveEvery single year, thousands of adults worldwide, both at home and in workplaces,injure themselves while attempting to lift/move heavy objects. Devices such as handtrucks can be used to relieve the stress of heavy lifting on flat ground, however, canfail when it comes to negotiating a short flight of stairs.The objective of this design project is to design and test a consumer hand truckcapable of climbing stairs – for use in homes and small businesses. Havingbrainstormed a number of designs that could travel over stairs, curbs or uneventerrain, the authors decided on a variation on the motorised chair climber. As a result,several models were researched and the group came up with a tweaked design.HistoryA hand truck (also known as a two-wheeler, stack truck, dolly, trolley, trolley truck,sack barrow, sack truck, or bag barrow) is essentially an L-shaped box handcart thathas handles at one end, wheels at the base, with a small ledge to set objects on and sitsflat against the floor when it’s upright. Objects that require moving are tilted forwardwhile the ledge is inserted underneath, and then tilted back to rest on the ledge. The
    • truck and object(s) are then tilted backward until the weight is balanced over the largewheels, facilitating the movement of heavy or bulky objects. A motor mechanism isattached to this hand truck to lift it up the stairs.Benefits and ProblemsHand trucks can be made from many different types of materials – such as tube steel,aluminum tube, aluminum extrusion and high impact plastics. Most commercial handtrucks that are used for service deliveries are very light weight. A motorized handtruck can completely eliminate the hardships of carrying objects up stairs. Its lightweight means that it can be easily transported, moved around and lifted. It also has theability to reduce or even eliminate the health problems that can arise by usingconventional had trucks that still require a lot of manual labour. However, stairclimber wheels can sometimes be problematic when trying to turn on flat ground, asfour wheels in a fixed position will be in contact with the ground.
    • 7 | P a g eDesign ObjectivesThe functional requirements for this stair-climbing hand truck include: The device should be able to provide most or all of the upward force necessaryto ascend a flight of stairs The device should be able to bear a weight of up to 100kg The cost of the device should be comparable to that of a conventionalconsumer grade hand truck The product should be ergonomic and easy to use The weight of the product should be comparable to that of conventionalmodels The appearance of the product should be similar to that of conventionalmodels A lightweight design Focus on standard house stairs Interchangeable toe plates Interchangeable- rechargeable battery Adjustable handle.
    • MarketabilityBeing a consumer hand truck, this design is primarily targeted towards end consumerswho need to bring heavy or awkward items up and down stairs on a regular basis –whether in a domestic home environment or in a small business environment.For example, older people having to bring laundry, food trays, shopping or otheritems up and down the stairs, would find a solution like this very appealing. Stair liftsare quite a prominent feature in the homes of older people – however, they areexpensive and require an extensive amount of installation to work. With the Stair-Climber Trolley, older people who are still of nimble agility, who do not want a StairMaster ensemble in their homes but struggle to lift weighty items up and down stairscan simply install this solution into their homes. In this way, they and their familiescan have the extra peace of mind in knowing that they are not lugging heavy objectsup or down stairs, which can contribute to potentially dangerous or even fatal falls.Other target markets include: small businesses or people living in apartments withoutthe use of a lift.This product will be priced competitively against other solutions (as outlined here)with a view to making it as affordable as possible for a consumer segment, whilstensuring the highest price that can be tolerated by the market.If targeting a consumer segment, the main ways to promote this is through –advertising (TV, radio, publications targeting the older generation or familypublications (as many children of older parents may worry about them carryingexcessive weights up and down). Distribution can also be possible through authorizeddealers who also cater for the needs of older people. Additionally, research could alsobe conducted to determine if there are any grants available for older people to installthese motorised gadgets into their homes to prevent falls and serious injuries.However, there is another potential buyer for this type of product design – othercompanies in the market that provide Stair-Master type solutions, who already havethe target market, the market reach, an established customer base and the marketingand sales budgets required to market this to a mass consumer segment – worldwide.
    • 9 | P a g eLiterature review:During the research phase of this project, the authors have conducted a literaturereview of conventional industrial hand trucks that are used today.The Cargo Master:The Cargo Master essentially does the same job as the electrical stair-climbing trolleywhich is the focus of this project, with the exception of operating in a different waywith additional features. This particular stair-climbing trolley aims to reduce oreliminate health problems and accidents caused by lifting heavy goods up a set ofstairs. It also enables one person to lift heavy objects up stairs, eliminating the needfor a second person to help. This can be very cost-beneficial in environments such asservice delivery (delivery of beverage and food items), saving valuable time andresources for companies. The trolley’s mechanism for lifting objects up stairs couldfeasibly be used on the likes of winding stairs (which would be even more difficult tomanually lift heavy objects up that type of stairs compared to the traditional set ofstairs), which means that the trolley itself would be adaptable to most stairs. Thedesign of the mechanism ensures that the trolley can be used on practically all typesof surfaces and also that the edge of the step will not be damaged in the process.The Cargo Master has a built-in speed control system, ensuring that the trolley can beadjusted around the different types of users (e.g. users that prefer to be on the higher
    • speed setting compared to the lower). Also, a safety brake system is applied to thistrolley to ensure that when the trolley is close to the edge of the step that the safetybrakes can be activated to prevent the operator from moving any further and, as aresult, prevent a potential accident e.g. trolley falling down the stairs.The battery used on the trolley is a sealed vapour-proof battery which is capable ofbeing charged by any 240v supply current. This is an additional battery pack thatcomes with the product and a car charger so the trolley can be continuously used,eliminating the need to wait for the product to charge before using it again. The liftingwheels on the trolley are made of rubber.As seen in the pictures above, the trolley’s mechanism basically pushes the trolley upthe next step from the previous step so that the mechanism is vertically pushing thetrolley up to the next step with a very powerful motor.Key features of this product include: An adjustable handle The centre of gravity depends of the load applied The trolley weighs 27kg Its dimensions are 1060 x 450 x 300mm Toe plate has the ability to be folded The lift has the capability of lifting objects 100kg x 1200mm high.
    • 11 | P a g eEase-E-Load Stair Climber Trolley Truck Carrying Capacity150kgThis is a manual stair-climbing trolley. With the same objective of the electrical stairclimbing trolley, this trolley allows the carrying of objects up stairs easily, doablewith just one person. The difference between this mechanical trolley and the electricaltrolley is that the electrical one does all the hard lifting through the motor andmechanism, whereas this manual trolley, while facilitating the lifting of heavy andawkward objects up stairs, still requires the operator to put in significant effort andback-breaking work to get them up the stairs. As can be seen from the picture, themechanism of the manual trolley moves around the steps of the stairs when beingpulled up, making it possible for the trolley to lift heavy objects up the stairs. Thisparticular product fetches 222.62 euros.Key features of this product include: Free- running pyramid wheels which makes mounting kerbs easier toaccomplish. The trolley is durable Foot size: 225 x 330mm Carrying capacity = 150kg
    • Stair Robot SR ExpressThis is an electrical, battery-powered stair-climbing trolley that distributes power to apowerful motor, which enables the trolley to travel up the set of stairs with ease. Thiselectrical stair climber is designed for day-to-day distribution, so it can be used quitefrequently. This particular product was designed as a compact and lightweight stairclimber with the ability to lift a weight of up to 150kg.It contains two basic techniques that enables the trolley to move up and down a set ofstairs: Step-by-step The trolley being laid flat on the surface of the stairs and sitting on two ormore steps.
    • 13 | P a g eThis particular trolley was designed for single operators. The design of this trolleyis very similar to the wheels of a tank or digger with its teeth-shaped wheelscapable of gripping the edges of the stairs, enabling the trolley to climb the stairs.Key features of this product include: Fast removable battery pack Remote control functionality Height adjustable platform Adjustable handlesThe same concept underpinning this electrical stair climbing trolley is now beingadapted to wheelchairs (giving wheelchair-confined users more freedom). The abovepicture illustrates the electrical stair-climbing wheelchair in use. As the pictureillustrates, this wheelchair can descend and ascend steps easily, ensuring the safety ofthe person. This particular electrical wheelchair climber is fairly similar to theprevious electrical stair climbing trolley. The wheelchair uses its teeth like wheels thatenable the wheelchair to grip the edge of the steps and gives the wheelchair operatorthe manoeuvrability to negotiate a set of stairs with ease. This concept in now readyfor commercialisation, so it won’t be much longer till electrical wheelchairs that arecapable of climbing stairs are seen all around the world.
    • The above electrical stair climber trolley is specially designed for the transportation ofmanual wheelchair users up and down a set of stairs safely. This electrical stairclimbing trolley has a motorised electronic traction control that grips the edge of thesteps at a constant speed, which ensures safe travelling up and down the stairs everytime. This particular product goes for 3595 dollars.Key features of this product include: Battery with long-life span Manual emergency device so that if the battery fails, for whatever reason, thesafety of the wheelchair user is not jeopardised Mechanism operates smoothly and quietly ensuring that nobody will bedisturbed when the electrical stair climbing trolley is in use Key control
    • 15 | P a g e Compatible to be used with various stair types Travels at 16ft/min Can lift up to 250 pounds capacity.
    • Motor Type SelectionDC motorAdvantages Speed control: dedicated switches that can vary speed of rotation of the DCmotor from higher and lower speeds. At the same time, taking intoconsideration that it cannot be too fast or too slow on the ascending of the stepof stairs. High starting torque: DC motor has a high starting torque. This will beessential for a steady start for lifting a load of approx. 100kg of weight. Thestarting torque can reach up to 500% in comparison to normal operatingtorques, which is what we needed to get the heavy load up the stairs. When the speed drops the torque is constant: over a given speed range, thetorque of the DC motor will remain constant.Disadvantages Initial cost is high. DC motor uses commuter and brush kit which are known for wear and tear. Asa result, there will be a higher maintenance cost and will eventually needreplacing altogether. Wear and tear of the commuter and brush will result in production of dust. DC motor cannot be used in explosive or hazardous areas because of the DCmotor sparkling.(Hughes 2006)Applications where a DC motor is used:DC motors are generally used in steel mills, paper mills, cranes, elevators, and electrictrains etc. Electric trains are a perfect example for a starting torque, as a high level oftorque is needed which is provided by the DC motor.AC motorAdvantages The construction of an AC motor is simple. They are cheap to buy. An AC motor is reliable.
    • 17 | P a g eDisadvantages Normally only used at a fixed speed. To apply a variable speed function to anAC motor, it could be very complex compared to that of the DC motor. Anadditional expense would also result if it were to be carried out this way (e.g.multiple winding or gearbox).Applications where an AC motor is used:An AC motor is generally used in fans, washing machine compressors, audioturntables etc. From looking at both the advantages and disadvantages, it is clear thatthe DC motor is the best motor to be applied to the electrical stair climbing trolley.The next step is looking into the different types of DC motors available.Two main types of DC motorsBrush:The motor, as a result of DC power being supplied to the DC motor, produces torque.This is achieved with the internal commutation, stationary magnets (which can bepermanent or electromagnets) and also with the spinning electrical magnets. Torque isgenerated as a result of Lorentz force and this applies to all electrical motors andelectrical generators. Lorentz force states that any current-carrying conductor placedwithin an external magnetic field will, as a result, experience torque.Advantages: They are cheap to buy. They are highly reliable motors. The speed of the motor can be simple controlled.Disadvantages: High level of maintenance required (this would entail changing brushes andsprings which are the components that carry the electrical current. Also, thecommutator may require to be cleaned or, in some situations, changed.). If the motor is in continuous use, then this will result in the lifespan of themotor being very low.
    • Brushless:This is essentially an AC motor with an electronic controller built-in so it acts like aDC motor but is not a DC motor. It is referred to as a DC motor to avoid confusion.The brushless motor uses a spinning magnet or soft magnet core that is located in themotor, as well as a fixed electrical magnet that can be found on the motor’s housing inorder to rotate. A controller is applied to the motor that converts DC to AC.Compared to the brush motor, the design of the brushless motor is simple. This is as aresult of the disregard of the complexity of transferring power from the outside of themotor to the rotating rotor.Advantages: This motor has a long lifespan. Little or no maintenance is required for this motor. High efficiency.Disadvantages: They are expensive to buy. The speed control is a lot more complicated compared to the brush motor.From the two types of DC motors examined above, the motor that was decided to beadapted to this electrical stair-climbing trolley was the DC brush motor (with thepermanent magnet). This decision was taken based on how both motors work, theadvantages and disadvantages of both, with the permanent magnet was the bestchoice.
    • 19 | P a g eThe DesignConsiderations taken while designingWhen undertaking the design for the electric stair-climber, the first thing that had tobe taken into consideration was an actual set of stairs, as this is what it had to bedesigned around. With the help of the internet and a few books which can be found inthe references, the authors obtained a greater understanding of stair terminology and,most importantly, the origin of where the dimensions of stairs come from was alsofigured out. Stair dimensions must follow building regulations and codes of practicein an effort to keep hazards of tripping or falling to a minimum. Obviously, it is notthe case where every staircase in Ireland is exactly the same in dimension and just hasa different finish. The designers of stairs have a range of values for each differentcomponent of the staircase (which can be seen in the picture below). With theseregulations and codes of practice in place, it makes it easier to negotiate the designand dimensions being applied to the staircase.In different types of buildingse.g. (flats, shops etc.), rules arestricter. As seen from thediagram on the right, the pitch(the angle at which thestaircase rises) of a staircase isrestricted to a 42 degreeincline. Limitations are alsoapplied to the size of the risersand threads etc.A flight of stairs should not have more than sixteen rises. If this is the case, a landingshould be incorporated into the staircase. This ensures that if individuals get tiredfrom going up the 16 steps, then they have a resting place that will give them a chanceto catch their breath in safe manner. This also discourages individuals that areclimbing more than sixteen steps to keep going when they become exhausted, as thiscould result in a fall and injury. The minimum width of a stair case is 860mm.
    • MechanismThe above sketch (initial design of the lifting arm and mechanism) represents theoverall look of the arm that is going to be taking the weight of the trolley and lifting itup the stairs. By just looking at the sketch, there is an indication of how it works.Point A shows the bar that is connected (pivoted) to the crossbar of the actual trolley.This gives the mechanism the ability to move up and down the y-axis. Point Bconnects Point A with the large rotational arm (A is pivoted off B, which is pivotedoff the large rotational arm). Point B gives the overall lifting arm the ability to moveup and down the x-axis. The combination of points A and B (which are essentially themain parts to the mechanism) gives the overall lifting arm the ability to move up anddown the x- and y-axes, which is essential in order for the crank of the motor tocomplete a full 360-degree rotation and still provide stability to the overall liftingarm. Stability is important because if the electrical stair climbing trolley is to climb aset of stairs smoothly, it needs to have the appropriate supports to account for anyimbalances. This is achieved with the above diagram.AB
    • 21 | P a g eMechanism free body diagramsThe free body diagram below illustrates the point where the most forceis needed to lift the trolleyThe free body diagram below illustrates the point where the secondmost force is needed to lift the trolleyThe free body diagram below illustrates the point where the force is atthe point where the trolley is on the next step and force is not neededanymoreInitial designThis is the initial design of the electrical stair-climber housed two motors, whereas thefinal design has one motor applying the force needed to climb the stairs. The teaminitially wanted to design a stair-climbing trolley with two motors, as the force couldbe evenly distributed between the two motors and by two shafts. Of course, as a resultof using two motors, there would have been a need for a bigger battery to cope withthe extra load of the additional motor but since there was two motors doing work, the
    • additional force needed to lift the extra weight of the battery wasn’t much of a worryfor the team. There are a few reasons why this was not the final outcome of thedesign.1. The motor that was used was designed to come out one direction. So to havetwo of the same motor, their shafts would have to be in line with each otherand this wasn’t as simple as putting the two motors back-to-back to eachother. To achieve alignment of the shafts of the two motors, housing had to bedesigned to secure the two motors in place and align the shafts of the twomotors. The housing was designed and the two motors where secured in it. Butwhen the housing with the two motors was applied to the assembly, it wasclear that it was way too big to be put onto the electrical stair-climbing trolley.The main reason why it was so big was because aligning the two shaft motorsled to a lot of lost space in the housing in order to support the motors in theright position. Also, because the housing of the motors was so big, it wasclashing with the lifting arms (used to lift trolley up stairs). With thedimensions at the time applied to the lifting arms and mechanism, the liftingarms were cutting into the housing of the two motors. No matter how manytimes the dimensions of the lifting arm and mechanism were changed (tryingto get the right dimension that would allow the trolley to climb the stairs withease and not cut into the housing), it was not preventing the lifting arms fromcutting into the housing of the motors and it became clearer that a reviseddesign was going to have to be looked into just in case this problem couldn’tbe resolved. The smaller the dimensions were for the lifting arm andmechanism, the decreased risk of the lifting arm cutting into the housing.
    • 23 | P a g eHowever, the down side to this was that it had less chance for the electricalstair-climbing trolley to climb the stairs (which is what this project is allabout). An initial revised design of just the lifting arms was first looked intoand can be seen below with the initial design.The left-hand screenshot shows the initial design for the lifting arm, while the right-hand-side shows the revised design for the lifting arm (designed to prevent the armfrom cutting into the housing of the two motors). The revised design looked good onpaper and was thought to be the solution that was needed to solve this big problem.However, once the design was drawn into SolidWorks, it was clear that it only madethe problem worse. Because the arm dips downwards, this meant that when the liftingarm was rotated around, the lifting arm came nowhere near the housing of the twomotors – success. But when a standard set of stairs was put into the overall assembly,it was clear that this design was not going to work. This was because, while theredesign achieved what it set out to achieve (i.e. prevent it from hitting off thehousing of the two motors), it caused another problem. Because the redesign lift wasat an angle downward, it prevented the lifting arm from being able to reach the nextstep. No amount of change to the dimensions of the lifting arm could be made torectify the problem. The dimensions of the lifting arm are limited - as in the crank andlarge rotational have an overall limit of 200mm in order to continue using the motorthat was already selected. Anything bigger than the 200mm value would result in themotor being having to be changed for a bigger motor, which was not a feasible option– it was hard enough finding the chosen motor as there were very few motors that theteam came across that ticked all the boxes in terms of what was needed from it. Alsothe motor that is being used was hard to position on the trolley with its size and
    • orientation, therefore, to use a bigger motor for the trolley would make the designmore cumbersome.2. The housing that’s attached to the trolley is very bulky and is just a big lumpsticking out of the back of the back of the trolley. This means the trolleywould be at a tilt when climbing the stairs and could, potentially, come intocontact with the step of the stairs, preventing it from climbing the stairseffectively.3. The design would include the additional weight of using two motors and theincreased battery weight (as a result of using two motors a bigger batterywould have been selected) that will be present on the trolley. While the motorwould be able to handle the weight of the additional motor and bigger battery,it would make the trolley difficult to wheel and manoeuvre for the operator.At the end of this trial and error process with SolidWorks, it was decided that therevised design for the lifting arm would be scrapped and instead of having two motorshoused together, one motor would be sufficient to carry out the task of lifting thetrolley up a set of stairs. This was carried out below and can be seen in the finaldesign of the electrical stair-climber.Twomotorssupportedin thehousingSupports (
    • 25 | P a g eFinal DesignWhen designing what the trolley was going to look like, it was decided to go with abasic trolley to start off the initial design process, with a view to modifying it tocomplement the final design to achieve a fully working, ergonomic electrical stair-climber. So with the initial design in mind, the team applied the dimensions to thedesign. This was done with ergonomics in firmly in the forefront of mind.Ergonomics allowed the team to design a trolley, taking into account average heightof potential users to ensure ease of use, ensuring it was not too big or small, so thatpretty much everybody can use it comfortably and with ease.When designing the trolley, it was known that these stair-climbing trolleys werealready readily available in the commercial world. This provided the team with avaluable reference point in the face of encountering challenges with design, allowingthem to see how other electrical stair-climbers designed – and the benefits anddrawbacks of each. Design doesn’t necessarily mean a radically new design - it canalso mean taking an old design and trying to improve on it to benefit the users. Mostdesigns deployed by companies are of the improving variant – with companiescompeting against each other on the basis of having the best designs so they cancharge the highest prices for their products.………………..
    • Base of the Trolley:The width of the base is 600mm and the length is 200mm. When applying thesedimensions, a step of an average set of stairs was taken into consideration to avoid thebase being wider than a set of stairs, which would prevent the trolley from being ableto get up a set of stairs. As it turned out, the width of the trolley base was less thanthe minimum width of a set of stairs, which is 860mm, so the trolley can go up anddown the stairs with ease. When applying the length to the base, the going (min220mm) of the step was taken into account, so that the length (which is less than thegoing) isn’t bigger than the dimension of the going so that the trolley can sitcomfortably on the step. The dimensions for the base can also be seen in the 2Ddrawing which can be found in the appendix.Base of theTrolley
    • 27 | P a g eArm FrameArm frame (x2) (female part)When designing the female part to the frame arm, the team wanted to use a hollowcylinder design with an outer diameter of 40mm and an inner diameter of 30mm,giving it a thickness of 5mm. The length of the arm is 1200mm. This is becauseallowance had to be taken into account for the length of the male part of the arm (sothat the combined height of the arm frame’s male and female parts would result in adecent sized trolley), which sits in the female part and will add to the total height ofthe trolley. Therefore, the total height of the trolley was split between the two partsappropriately. The dimensions for the arm frame of the female part can be found inthe appendixArmFrame(Malepart)ArmFrame(Femalepart)
    • Arm frame (x2)(male part)The male part to the arm frame sits in the female part of the arm frame. This was doneto allow for the electrical stair-climber trolley to adjust its height depending on what itis carrying up or down the stairs. The outer diameter is 30mm and the inner diameteris 20mm, giving it a thickness of 5mm. The height of the arm frame’s male part is600mm. The dimensions for the arm frame of the male part can be found in theappendixArm frame total height:Combining the height of both the male and female part of the arm frame gives a totalheight of 1800mm (180cm), which is applied to the trolleyPinThe pin is used to lock the adjusted height in place. A clearance fit is applied to themale and female part of the arm frame, allowing the male part to move freely up anddown the female part, with the pin applying force to lock the male part in a set placealong the female part.Pin (that locksthe arm frameboth male andfemale parts inplace)
    • 29 | P a g eWheel AttachmentsThe wheel attachment comes in three parts (part A and B (x2)), which grips thefemale part of the tube. It is then bolted to the female part of the arm frame, which isoffset from the base by 100mm, with the wheel being positioned 50mm up from thatpoint so that it is positioned 150mm up from the bottom. When the 300mm wheel isattached, these three dimensions allow it to sit flush to the step and to be wheeled likeall other two wheeled trolleys are wheeled. The dimensions for the Component A andB can be found in the appendixB: Thesetwoindividualwheelattachmentparts lockthe mainwheelattachmentin placeA: Main partof wheelattachment
    • HandleThe handle is designed so that it is not sitting in line with the female and male framearms - it is offset by approximately 140mm to enable a long objects to be comfortablycarried up stairs (without the offset, it would be awkward to hold as it would be wherethe user places their hands when holding the trolley). So the handle is offset awayfrom the arm frame so that the trolley can be handled comfortably (i.e. fingers aren’tgetting crushed and good grip isn’t being sacrificed), which is key in designinganything. The dimensions for the handle can be found in the appendix.Extendedhandle bar
    • 31 | P a g eRotational shaft with key way (for the motor and rotationalsupport)The rotational shaft was designed with a key way so that power from the motor can beeffectively transmitted to the crank. The dimensions for the rotational shaft can befound in the appendix.For finding the size for the key way, the following table below is used to work out thedimensions of it. The dimensions that were selected for the key way were width 6mmand the height 3mm which can be seen in the 2D drawings in the appendix.Rotationalshaftattachedto themotorKey waytransmittingpower fromthe motor tothe smallrotationalArm
    • Relevantkey waydimensionsfor a 19.05mmdiametershaft
    • 33 | P a g eCrank (which is attached to the motor to the rotational shaft)This is the part that enables the trolley to climb the height of the stairs. But whendesigning it, the length was fairly awkward to pick. If the length is too small, thetrolley will not be able to climb the stairs. Also the length of the crank cannot be toobig, as the arm with the wheels that sit on the step moves in an out, it will end upcutting into the motor and the rotational support which is fixed onto the trolley. So thetrolley had to be modified to allow the overall arm to move freely and have anefficient and effective length on the shaft that would be able to lift the trolley up thestairs and not cut back into the motor. The dimensions for the crank can be found inthe appendix.SmallRotationalArm
    • Large Rotational Arm (attached to wheels that sit on step)The length of this arm also affected whether or not the arm would cut into the motorand rotational support. So the length (132.5mm) was chosen because it was longenough to reach the step of the stairs and, when rotated, doesn’t cut into the motor androtational shaft. The dimensions for the large rotational arm can be found in theappendixOverall length of the crank and large rotational armThe overall length of the two arms was restricted to an overall length with a range of180-200mm, which ended up being 200mm. This is because the greater the length ofthe arms, the more force that was needed to lift the trolley. From the calculations thatwas done for the motor, it worked out that the overall optimum length of the arms was180mm-200mm, which was applied for the overall length.LargeRotationalArmOverallLengthmeasuredfrom hereTohere
    • 35 | P a g eWheels that sit on stepThese are the two wheels that sit on the step which assume the weight of the trolley asit is being lifted up the stairs. The wheels have a 50mm diameter and thickness of15mm. The tube connecting the two wheels has a diameter of 40mm and the length ofthe tube is 360.292mm. The material that will be used for these two wheels will be asolid rubber material. This will ensure that the tyres will never have a flat and, mostimportantly, they will provide the grip necessary to lift the trolley up the stairswithout slipping (which could result in an injury or damage). The dimensions for thewheels that sit on step can be found in the appendix.Wheelsthat takethe weightof thetrolley andobjectsbeingcarried.
    • MechanismStage 1: The starting position of the lifting arm and mechanism.Stage 2: The lifting arm and mechanism are positioned on the stairs but are nottaking the weight of the trolley just yet.
    • 37 | P a g eStage 3: The lifting arm and mechanism has lifted the trolley halfway up the step.Stage 4: The lifting arm and mechanism has lifted the trolley up a step on the stairsand is going to start the whole cycle again until the top of the stairs is reached.
    • Final design of the mechanism:When designing the mechanism, the team got a little carried away with existingelectric chair-climbing mechanisms. This was both positive and negative. On thepositive side, it showed the team exactly how the arm works (lifting the trolley up aset of stairs), giving them confidence in going off to make their own design. However,the problem was that the team didn’t understand how the arm stayed parallel to thestep (when the machine was being illustrated in online videos, the actual mechanismwasn’t shown, preventing the team from seeing it in action). As a result of this, theteam wasted time trying to understand what was already done. In the end, it camedown to thinking outside the box to come up with a new design that had the sameprinciples (keeping the arm parallel to the step).The mechanism is attached to the support of the motor which can be seen above, withthe other end being attached to the arm that sits on the step of the stairs, which canalso be seen above. At that point, the mechanism is fixed to the arm that is sitting onthe step (allowing the arm to constantly be parallel to the going of the step of thestairs), while the rest of the mechanism (which is attached to the support of the motor)moves up and down the x- and y-axes to allow the fixed point to move along the x-and y-axes. This also prevents the large rotational arm from twisting so that the motorcan effectively transmit its power to the crank and large rotational arms. Thedimensions for the individual parts of the mechanism can be found in the appendix.
    • 39 | P a g eSupports (which support the motor, mechanism androtational shafts)The supports ensure the stability of all the components on the trolley. The dimensionsfor the supports can be found in the appendix.Ansys:Ansys could not be done on the SolidWorks 3D drawings (of the overall assembly), asno member of the team had the required skills to operate the software with anyproficiency. So the team decided to go down an alternative route and do aSolidWorks simulation instead. This was achieved successfully, however, the onlydownside was that it could not be applied to the overall assembly but to only onesingle part of the assembly. So it was decided that the whole mechanism would bemade up as one single part. Again, this was successfully achieved, however, when thesimulation was run on it, the component reacted weirdly and the results obtained fromthe simulation were useless – so in the end, that idea had to be scrapped. The nextoption was to perform it on the most important part of the mechanism, which was thelarge rotational arm (as it was the part that the motor transmits power to and that themechanism holds together and, most importantly, it is the key reason how the trolleySupport formotor andmechanismSupportsfor MotorandRotationalShaftBatterysupport
    • can get up the stairs). So the simulation was done on that part and the results andconclusions from this can be found in the appendix.
    • 41 | P a g eMaterialConsidering weight of the trolley and different types of users, the authors decided touse aluminium alloy 6061, which is a precipitation alloy containing magnesium andsilicon as its major alloying elements, as the material for our hand trolley. The high-strength aluminum alloys rely on age-hardening: a sequence of heat treatment stepsthat causes the precipitation of a nano-scale dispersion of intermetallics that impededislocation motion and impart strength. This can be as high as 700 MPa, giving thema strength-to-weight ratio exceeding even that of the strongest steels.It has good mechanical properties and exhibits good weld-ability. It is one of the mostcommon alloys of aluminium for general purpose use. It is commonly available inpre-tempered grades such as 6061-O (solutionized) and tempered grades such as6061-T6 (solutionized and artificially aged) and 6061-T651 (solutionized, stress-relieved stretched and artificially aged). 6061 is widely used for construction ofaircraft structures, such as wings and fuselages, more commonly in homebuilt aircraftthan commercial or military aircraft. 6061 can be easily worked and remains resistantto corrosion even when the surface is abraded. It is used for yacht construction,including small utility boats, in automotive parts, such as wheel spacers, in themanufacture of aluminium cans for the packaging of foodstuffs and drinks, in scubatanks (post 1995) and was the material used for the pioneer plaques.Consideration was also taken for another two types of materials -one of which wasaluminum. These composites are metals reinforced with ceramic particles. The mostwidely used are based on aluminum reinforced with particles of silicon carbide oralumina. The reinforcement increases the stiffness, strength and maximum servicetemperature without seriously increasing the weight. It has a cost of 2 - 5 €/kg. Theother one was stainless steel - Grade 304 is the standard "18/8" stainless; it is the mostversatile and most widely used. Even though it had a higher yield strength thanaluminium, it was decided to go with aluminium as it was widely available andprovided more ease with which to work, giving it a winning vote.General propertiesDensity 156 - 181 lb/ft^3Price * 1.07 - 1.17 USD/lbDate first used ("-" means BC) 1916Mechanical propertiesYoungs modulus 9.86 - 11.6 10^6 psi
    • Shear modulus 3.63 - 4.06 10^6 psiBulk modulus 9.28 - 10.2 10^6 psiPoissons ratio 0.32 - 0.36Yield strength (elastic limit) 13.8 - 88.5 ksiTensile strength 26.1 - 89.9 ksiCompressive strength 13.8 - 88.5 ksiElongation 1 - 20 % strainHardness - Vickers 60 - 160 HVFatigue strength at 10^7 cycles 8.27 - 30.5 ksiFracture toughness 19.1 - 31.9 ksi.in^0.5Mechanical loss coefficient (tan delta) 1e-4 - 0.001PriceAt the latest, according to the www.metalprices.com it is priced at 1.485 euro per Kg.CalculationSelection of motorTo select a motor, the team had to find the power it needed to lift a weight (100 kg)up the stairs. Due to its specific design, when the arms push the load up the weight,force acts through the small tires at the end of the arms down the body. The safetyfactor was taken to be 4, therefore, the minimum weight it needed to lift was found tobe 100kg. The first calculation was the work acting and then using the time (3sec) itneeded to push the weight the team found the power output. (Direct 2012)First the force was calculated using the rise height as 220mm:Then using the arm length to be 20cm, the team found the torque acting at the joint ofthe arm by the motor:
    • 43 | P a g eAssuming there are 40 steps to climb and taking one revolution to climb each step, itwas assumed that 40 RPM (revolutions per minute) would be needed for the motorand, in doing so, found the angular velocity. Then using angular velocity and torque,the power needed for the motor was calculated as follows:From above, it can be concluded that any motor with a power output higher than822W can be used.Selection of batteryUsing the power and voltage (24V), the team found the current needed to run themotor.The equation is as follows:
    • Using the current and voltage, kWh was calculated:Using the current and the minimum time needed for the battery to run, the charge wasfound:The above charge was converted to amp hours and was calculated using:It was found that to run the present motor of .024kWh for 20 minutes, a battery ofminimum 10.7 Ah was needed. Therefore, it was decided to get a two 12V 5Ah sealedlead acid battery which will give a time as follows:As it was a reasonable time, it was decided to proceed with this.
    • 45 | P a g eTorsion in the armThe arms had to be of adequate diameter to ensure that it didn’t cause failuredue to torsion. The diameter was calculated as follows:Using the previous calculations obtained, the torque was found to be 196.2Nm, that the shear strength of Aluminium 6061 is 190MPa and a safety factorof 4:Solving for d, gives a diameter of 27.5mm. This was rounded up to 30mm inour actual arm diameter.Selected MotorFor the selection of the motor, the team considered two different motors from twodifferent companies listed below:The first came from Prestolite motors. With the specifications outlined below, it wasconsidered first because of its size and the way it could be fitted onto this design.
    • The next one was from Dongyong motors:With 90:1 gear ratio, 40 RPM and 900W optional power, this was the best choice.With an inbuilt gearbox, this could be fitted straight on to this project’s productdesign without needing any tweaking.
    • 47 | P a g eOn the basis of price, reliability and the fact it had the exact specifications that wasneeded, the team selected the second motor option (Tarp gear motor) for its design.
    • Design problemsIn the beginning, the team focused on using two motors side-by-side to give morepower to the arms. However, in the later stages, it was found to be too difficult andwas making the design far more complicated than it needed to be, so it was decided togo with single motor which was enough to produce the required torque as statedbelow:Weight and CostWith DC motor, battery and complex design, the total weight of the product wasfound to be around 20kg (without battery). The rechargeable lead acid battery wouldweigh around 4kg.
    • 49 | P a g eSelection of batteryThe company that supplied the battery is called Battery Sharks and positionthemselves as the replacement battery specialists. As a result, they have a huge varietyof every battery in the market, making the process of finding the perfect battery eveneasier. The chosen model turned out to be the 12V-5AH NB12-5 battery. This wasperfect for what was needed, as it not only met the desired power requirements butwas also an ideal size at approx. 70mm deep, 90mm wide and 110mm high. It is verylight at approximately 1.65 kg. NB12-5 is a rechargeable, maintenance-free, non-spillable and a highly efficiently designed battery. This model has an expected life ofup to 5 years in standby use, with low self-discharge rate and lower than 3% capacityloss per month. However, national batteries can be stored for up to one year at 25oCbut then a freshening charge is recommended. This type of battery is commonly usedfor emergency light, mobility and alarm and securities, but can be used for almost allpurposes. As mentioned previously, the hand truck will require two of these batteriesas they have only a 5ah output.One might question the cost of using two batteries instead of just one 10ah battery,but these batteries are surprisingly cheap and actually work out cheaper than itsequivalent 10 ah battery.
    • Battery Life CycleThe battery has a lifecycle, as seen below. Assuming that the temperature is keptconstant at 25oC, the rates of discharge can be calculated easily. As the number ofcycles increases to 450, the discharge capacity drops by 50%. As the battery is usedmore, the discharge continues to decrease but at a slower rate. The battery can be usedover 600 times before it loses 20 percent. However, after these 1,150 uses, thedischarge will have dropped all the way to 30 percent and will need to be changed.
    • 51 | P a g eBattery SizeAbove you can see a drawing of theform of the battery. Its height is approx.107mm.Above is a drawing of the top of thebattery. The two terminals can be clearlyseen and the dimensions are approx. 70mmdeep by 90mm wide.This is a drawing showing clearly all thedimensions of the terminal of the battery.This is a basic side view of the batteryto give a finished idea of the size of thebattery. The dimensions are given in thedrawings above.
    • Battery capacity retention characteristics:When the battery was chosen, the team looked into all the information available andfound that the capacity characteristics depended on the temperature as follows. Thegraph shows that as the temperature increases, the capacity retention ratio of thebattery is less efficient. A simple example of this can be seen on the graph. It takes thebattery almost four months to reach a ratio of 50% at 30 degrees, but at 40 degrees ittakes only two months. This graph shows the user the importance of the temperatureat which the battery is kept. Fortunately for the specific use of this design, the batterywill not be kept at high temperatures like this so it is not a big concern.
    • 53 | P a g eA 10Ah batteryThe 10 ah battery that was selected was the same model as the 5ah battery that wasoriginally selected. Its specs were very similar. The only properties that changedwere, obviously, its weight and size.Varying the speedThe initial reactionThe initial idea was to insert a variable resister in the circuit to vary the speed,however, there were numerous reasons why this idea was not used. The initialthoughts were as follows. These figures have been completely made up and are purelyfor an explanation purpose. If the no-load motor current at 5V is 88 mA, the apparentresistance has to be 56 ohms (5V / 0.088 A). The question was - can the speed of themotor be lowered to 1/3 if a 112 ohm resistor was inserted to take up 2/3 of thepower?After a lot of research the following conclusions were made:If a 200ohm potentiometer (a variable resistor) between the motor and GND wasinserted, then this theory could be tested. The variable resistor was first powered upand set to 0 ohms. Then with the resistance set to 112 ohms, the motor was a littlesluggish, but seemed to work – albeit at a slower pace. The circuit was turned off, butthe pace continued, however, it was turned back on (still set to 112 ohms), the motordidn’t turn on at all.The problem was that a motor is a varying electrical load. A motor needs a lot morepower at start-up than it does when running. When the 112 ohm resistance is set, themotor turning power needed to start up is not met. Since the motor is going up stairsand will need to draw a lot of additional power, this solution wouldn’t work.There is another reason why a resistor is not a good choice for controlling the powerdelivered to a large load. As the power requirements increase, it will quickly exceedthe power rating on a resistor or potentiometer. The electronic component will getvery hot and then will likely fail permanently.
    • Furthermore, a resistor wastes excess power as heat. As with all projects, aninefficient methods must try be avoided.Pulse Width ModulationSo it is now known that using a resistor to change the speed is inefficient, as holdingback the power makes the resistor hot and energy is lost. Therefore, a better way tovary the voltage is needed and, by doing so, vary the speed. The best way to do this iswith a pulse width modulator (pwm). For the project, an understanding of exactlyhow pwm’s work is needed and how they are wired, as one will be added to thecircuit. Below is an outline of how pulse width modulation works and how its wired.When a circuit runs at 10v, an oscilloscope will show its voltage as shown below:This voltage is constant just like 0V shown below:
    • 55 | P a g eBut what happens when there is a 10v supply being turned on and off? The wave formis 10V half the time and 0v half the time. This is a 50% duty cycle, so called since it’son 50% of the time and off 50% of the time.The 10V is only there half the time so what is seen is an average voltage of 5 volts.Because the motor takes time to change between sudden changes in voltage, a steadyvoltage of 5 is achieved, which is unexpected at first.Now look at the screen show below. The 10v is only on 10% of the time so it is seenthat it has a 10% duty cycle and an average voltage of 1V is seen.So by changing the pulse width, the average voltage is changed seen by a circuit. Thisis where the name pulse width modulation comes from for this method.Building a pulse width modulation (pwm) generator circuit is reasonably easily andvery cheap, requiring only few parts.
    • The overall circuit looks as follows:The key component is the 555 chip shown below. It can buy one for approximately 2euro.The 555 chip has eight connection points - each one is described below. For theproject, there is no need to worry too much about the exact detail of how it works, asthe variable speed switch will be bought in and fitting it in the simple circuit.Pin Description Purpose1 Ground Dc ground2 Trigger The trigger pin triggers thebeginning of the timingsequence. When it goeslow, it causes the output
    • 57 | P a g epin to go HIGH. Thetrigger is activated whenthe voltage falls below 1/3of +V on pin 8.3 Output The output pin is used todrive external circuitry. Ithas a "totem pole"configuration, whichmeans that it can source orsink current. The outputpin is driven high when thetrigger pin is taken low.The output pin is drivenlow when the threshold pinis taken high, or the resetpin is taken low.4 Reset The reset pin is used todrive the output low,regardless of the state ofthe circuit. When not used,the reset pin should be tiedto +V.5 Control Voltage The control voltage pinallows the input ofexternal voltages to affectthe timing of the 555 chip.When not used, it shouldbe bypassed to groundthrough a capacitor.6 Threshold When the voltage risesabove 2/3 of the +V thethreshold pin causes theoutput to be driven low
    • 7 Discharge The discharge pin shorts tothe ground when theoutput pin goes high. Thisis normally used todischarge the timingcapacitor duringoscillation.8 +V DC power 12V hereWhen the chip is constructed in such a way, it gives out a square wave that is pulsewidth modulated.But how to change the duty cycle? By changing the potentiometer, the duty cyclechanges in proportion. So by twisting the potentiometer, this enables the varying ofthe average power.In order to get a wider speed range an ideal 100K pot will be used.The diodes in the circuit are used to stop current flowing in the wrong direction.Zener diodes are very poor voltage regulators and so the team will avoid using them.Thirty percent more gets the user a proper regulator. A basic 1N34 diodes will beused.
    • 59 | P a g eThe capacitors in the circuit are 10nF ceramic capacitors. The best way to identifythem is by the number 103 written on them.Another very important part of the circuit is the npn transistor. The transistor allowsthe user to deal with heavier loads than just the 555 chip can handle. A basic tip 31transmitter can be picked up easily. The only thing to watch is that the transistormight heat up with heavier loads. If the transistor heats up too easy all that is neededto be done is put a heat sink on it and our problem is solved.
    • The final diode is put in to make sure the inductive loading of the motor doesn’t blowsomething up.Applications where pwm circuits are used include dimming the lighting on yourlaptop or changing the speed on a remote control car.In general, a pwm supplies full power to the motor but only in short pulses. A motortakes a little bit of time to respond to abrupt changes. So by powering it with a pulsewave that varies between 0Va and 12V at a fast rate, the motor will behave as if it isgetting a steady voltage somewhere between 0 and 12 depending on the duty cycle.
    • 61 | P a g eSpeed controllerWith this understanding of how pwm works, it can now be applied to this project. Forthe design, two speeds are needed, however, it was decided that a variable speed ofgreater range will be applied because it is unknown where it will be used. Forexample, older people may want to use the trolley and want to work at a slower rate.There is a better understanding of the motor speed controller, but for building thedesign, the team would just buy a variable speed controller. The images belowillustrate how to wire the battery and motor into the side of the variable speedcontroller.
    • Recommendation:If more time was given to the project, then additional work would be done on thefollowing: Look into applying safety brakes onto the trolley that would prevent theelectrical stair climbing trolley from falling down the stairs, which wouldresult in an injury or damage. Make the base of the trolley with interchangeable bases so that it can copewith almost any situation. Look more into the design of the trolley and making sure that the objectsbeing lifted by the trolley is sitting evenly on the trolley so that objects won’tfall out of it (which could result in injury or damage). Look into adapting an interchangeable battery onto the design of the trolley sothat, while one battery is being charged, the trolley can still be used with theother battery which should be fully charged. The interchangeable battery willneed to be secured onto the trolley when in use, so that it doesn’t fall off andcause a potential accident. A breaking system should be applied to the mechanism that climbs the stairs,ensuring that if the battery goes flat or the motor just dies that the trolleywon’t simply just fall down the stairs as a result, but will be in a fixed positiontill somebody can come to help.
    • 63 | P a g eConclusionOverall, this project proved to be a great learning experience in terms of working in ateam. It showed the three members of the team what it is like working in a team ofpeople you don’t really know, ensuring there is sufficient scope to share the workevening among the team and to adhere to deadlines and timescales.The process of deciding as a team to design an electrical stair-trolley took a while toreach, as each member of the team had to agree to pursue this particular project. Theteam had its up and downs but, in the end, the team came together and designed theelectrical stair-climber in as most efficient and effective a manner as possible, andcompile the learnings, experiences rationale of it into a report.In terms of actually designing the stair-climber itself, the team believes it hasachieved a reasonably good design that can be manufactured quite cost competitivelyand marketed to the segments outlined in the marketability section (older people,people living in apartments with no lifts, small business owners). The team is of theopinion that a product like this could, and should, be more readily available for thissegment of the market and its design is specifically made to ensure excellentergonomics and ease of use.Overall, the team is happy with the outcome in terms of the final design of the electricstair-climber and that it has achieved what it set it out to achieve.
    • Roles of the groupStephen McLoughlin:Tasks done: Designed the overall trolley. Write up on the design of trolley. Solid Works: did all the solid works 3D and 2D drawing of the trolley. Solid Works simulation was done on mechanism arm. Did free body diagrams of the mechanism. Write up was done on simulation. Literature survey. Looked into the construction of Stairs (and incorporated it into the design). Looked into AC and DC motors (Advantages and Disadvantages and differenttypes of DC motors and chose best type of DC motor to use for the project). Looked into Calculations (Power, Torque, Back EMF, Speed etc). Looked into mechanism and came up mechanism design to use in the project. Marketability. Compiled report Proof read report Conclusion. Did presentation Sides for appropriate sections. Compiled presentation.Shiyas BasheerTask done: Introduction section (Introduction, History, Benefits and Problems). Material Selection. Looked into different types of mechanism already out there (this was done totry on deciding what the team wanted their electrical stair climber to looklike). Did initial and Finalized Calculations (Battery and Motor calculations). Motor selection. Torsion on arm calculations
    • 65 | P a g eConor TiernanTasks done: Looked into variable speed switches. Initial Calculations on motor selection Motor selection. Battery Calculations. Battery selection. Did presentation slides for appropriate section
    • ReferenceEncyclopedia, 2012. hand truck -- Britannica Online Encyclopedia. Britannica.Available at: http://www.britannica.com/EBchecked/topic/254117/hand-truck[Accessed October 20, 2012].Dongyang, Small AC/DC Motors & Gear Motors | DYD MOTOR. Available at:http://www.dongyangmotor.com/ [Accessed October 20, 2012a].Liftakar, Stairclimber Sales from Sano UK Powered Stairclimbers - Home. Availableat: http://www.liftkardirect.com/ [Accessed October 20, 2012b].Journal, stairclimber.pdf. Available at:http://courses.washington.edu/art483/site/images/stairclimber.pdf [Accessed October20, 2012c].Direct, L., 2012. Stairclimber Sales from Sano UK Powered Stairclimbers - Home.Liftkar Direct. Available at: http://www.liftkardirect.com/ [Accessed October 20,2012].Finney, D., 1991. Variable frequency AC motor Drive system,Hughes, A., 2006. Electric Motors and Drives Third.,Niku, S., 2010. Introduction to Robotics Second.,D Marshall & D Worthing (2006). The Construction of Houses. London:EG BooksA Engel(2007). For Pros by Pros, Building Stairs, United States: The TauntonPress.DC and AC Advantages &Disadvantages[Online].Available:http://electricalquestionsguide.blogspot.ie/2011/05/dc-motors-advantages-disadvantages-ac.html - Last Accessed 26th September 2012DC and AC Advantages and Disadvantages[Online].Available:http://www.wdtl.com/pdf/WT4706AdvantagesandDisadvantages.pdf - LastAccessed 26th September 2012
    • 67 | P a g eAC diagram [Online].Available:http://www.tt-itbu.com/technology/20090309/DC.html - Last Accessed 26thSeptember 2012Voltage current torque etc in a dc motor[Online]. Available:http://www.societyofrobots.com/actuators_dcmotors.shtml - Last Accessed27th September 2012Cargo Master [Online].Available:http://www.materialshandling.com.au/pc-2254-53-cargomaster-electric-stair-climbing-trolley.aspx -Last Accessed 27th October 2012Manual Stair Climbing Trolley[Online].Available:http://www.fileone.ie/Ease-E-Load-Stair-Climber-Trolley-Truck-Carrying-Capacity-150kg.html -Last Accessed 27th October 2012Stair Robots [Online]. Available:http://www.hercules.com.au/index.php?srexpress –Last Accessed 27th October2012Stair Climbing WheelChair [Online].Available:http://marketplace.sibaya.com/2007/05/18/topchair-stair-climbing-wheelchair-ready-for-commercialization/ -Last Accessed 27 October 2012Stair Climbing Trolley Designed around Wheel Chairs [Online]. Available:http://www.ameriglide.com/item/AmeriGlide-AG-CLIMBER.html -Last Accessed27th October 2012
    • Appendix:Electrical stair climber assembly 2D drawingBase 2D drawing
    • 69 | P a g eFemale tube 2D drawingMale tube 2D drawing
    • Pin 2D drawingHandle component 1 2D drawing
    • 71 | P a g eHandle component 2 2D drawingHandle Component 3 2D drawing
    • Main support 2D drawingSelected battery 2D drawing
    • 73 | P a g eOverhead battery supportBottom of battery support 2D drawing
    • Rotational Support 2D drawingSupport for motor and rotational support 2D drawing
    • 75 | P a g eOverhead support for rotational support 2D drawingShaft for rotational support and motor 2D drawing
    • Rotational Arm of Motor 2D drawingRotational arm for rotational support 2D drawing
    • 77 | P a g eCrank 2D drawingMechanism and motor support component 1 2D drawing
    • Mechanism and motor support component 2 2D drawingMechanism component 1 2D drawing
    • 79 | P a g eMechanism component 2 2D drawingMechanism component 3 2D drawing
    • Mechanism component 4 2D drawingMechanism component 5 2D drawing
    • 81 | P a g eMechanism component 6 2D drawingWheel attachment component 1 2D drawing
    • Wheel attachment component 2 2D drawingWheel attachment component 3 2D drawing
    • 83 | P a g eWheel 2D drawing
    • Simulation ofAlternative mechaniattached to motorDate: Tuesday, October 23, 2012Designer: SolidworksStudy name: SimulationXpress StudyAnalysis type: StaticTable of ContentsDescription 84Assumptions 85Model Information 85Material Properties 86Loads and Fixtures 87Mesh Information 88Study Results 90Conclusion 93DescriptionNo Data
    • 85 | P a g eAssumptionsModel InformationModel name: Alternative mechanism attached to motorCurrent Configuration: DefaultSolid Bodies
    • Document Name andReferenceTreated As Volumetric PropertiesDocument Path/DaModifiedCut-Extrude1Solid BodyMass:0.134618 kgVolume:4.98584e-005 m^3Density:2700 kg/m^3Weight:1.31925 NE:3rd year level8Engineering DesignWorks up to dateAltermechanism attachedmotor.SLDPRTOct 23 00:14:56 20Material PropertiesModel Reference Properties ComponentsName: 6061 AlloyModel type: Linear ElasticIsotropicDefault failurecriterion:Max von Mises StressYield strength: 5.51485e+007 N/m^2Tensile strength: 1.24084e+008 N/m^2SolidBody 1(Cut-Extrude1)(Alternativemechanism attached tmotor)
    • 87 | P a g eLoads and FixturesFixture name Fixture Image Fixture DetailsFixed-2Entities: 1 face(s)Type: Fixed GeometryLoad name Load Image Load DetailsForce-1Entities: 1 face(s)Type: Apply normal forceValue: 981 N
    • Mesh InformationMesh type Solid MeshMesher Used: Standard meshAutomatic Transition: OffInclude Mesh Auto Loops: OffJacobian points 4 PointsElement Size 3.68177 mmTolerance 0.184088 mmMesh Quality HighMesh Information - DetailsTotal Nodes 11501Total Elements 7166Maximum Aspect Ratio 8.2839% of elements with Aspect Ratio < 3 98.8% of elements with Aspect Ratio > 10 0% of distorted elements(Jacobian) 0Time to complete mesh(hh;mm;ss): 00:00:02Computer name: BST-390-G-02
    • 89 | P a g e
    • Study ResultsName Type Min MaxStress VON: von Mises Stress 3681.27 N/m^2Node: 92826.9433e+007 N/m^2Node: 11377Alternative mechanism attached to motor-SimulationXpress Study-Stress-StressName Type Min MaxDisplacement URES: ResultantDisplacement0 mmNode: 380.359234 mmNode: 1
    • 91 | P a g eAlternative mechanism attached to motor-SimulationXpress Study-Displacement-DisplacementName TypeDeformation Deformed Shape
    • Alternative mechanism attached to motor-SimulationXpress Study-Displacement-DeformationName Type Min MaxFactor of Safety Max von Mises Stress 0.794269Node: 1137714980.8Node: 9282
    • 93 | P a g eAlternative mechanism attached to motor-SimulationXpress Study-Factor of Safety-Factor of SafetyConclusionFrom the above report, the team generated SolidWorks simulations of the force beingapplied to the large rotational arm and the effects it has on the arm. The hole that isused to connect the large rotational arm to the crank is used as the fixed point in thissimulation. The force of 981N (100(kg) x 9.81(gravity) = Force applied) is applied allalong the large rotational arm and the results above were obtained. With the meshapplied to the large rotational arm, the simulation to find the yield strength is then
    • completed. The yield strength came out at 55148500 N/m^2, which is very strong.Also, starting with the color blue (least amount of stress) and working its way up tothe color red (most amount of stress), this illustration shows the different levels ofstress being applied to the large rotational arm. From the diagram above, it can beseen that the large rotational arm has a slight deformation. In the team’s opinion, it isdoubtfull that this will have any impact on the performance or safety of the electricalstair-climbing trolley. The report generated results that were, in some way, expectedand the team feels that the simulation was a success. This part has been recentlyupdated but when the simulation was initially run and the report generated, the reportcame out the way it was supposed to. There is no real difference between this reportand the updated part report, meaning so this report is sufficient in showing thesimulation of the large rotational arm. Screenshots can be seen of the updated partbelow.So as can be seen, the yield strength is the same as the previous simulation
    • 95 | P a g eDifferent displacement values have been obtained compared to the previous part
    • ErgonomicsCalculating the average height and reach of a person to help decide on theheight of our trolley.In order to calculate how big our trolley should be we need to decide what theaverage height of a person should be. Below are some of the interesting facts wefound.The tallest manThe tallest man living is Sultan Kösen (Turkey, b.10 December 1982) whomeasured 251 cm (8 ft 3 in) in Ankara, Turkey, on 08 February 2011.The part-time farmer was the first man over 8 ft. (2.43 m) to be measured byGuinness World Record in over 20 years.Indeed, GWR only knows of 10 confirmed or reliable cases in history of humansreaching 8 ft. or more.Sultan also holds the records for widest hand span and largest feet on a livingperson.From this we can take that since there have only been 10 men over 8 ft. in theworld ever that if the product we are carrying is of average size we will not needto exceed this limit of 8 foot when designing the height of our trolley. However,we want to accommodate for extra-long product so we have decide that we aregoing to make our arms extendible to a reasonable length anyway.Average height in different countriesGrowth and height have long been recognized as a measure of the health andwellness of individuals. In order to decide the average height of a man or womenusing the trolley we must consider this chart and where the product will be soldmost. This chart shows the average height of males and females in various worldcountriesChart showing the average height of males and females in various world countries.Country Average male height Average female heightArgentina 174.46 cm (5 ft. 8.6 in) 161.03 cm (5 ft. 3.4 in)Australia 178.4 cm (5 10.2") 163.9 cm (5 4.5")Bahrain 165.1 cm (5 5") 154.7 cm (5 1")Belgium 176.6 cm (5 9.5") 163.3 cm (5 4.3")Brazil 169.0 cm (5 6.5") 158.0 cm (5 2.2")Cameroon 170.6 cm (5 7.2") 161.3 cm (5 3.5")Canada 174 cm (5 8.5") 161.0 cm (5 3.4")China (PRC) 164.8 cm (5 4.9") 154.5 cm (5 0.8")China 169.4 cm (5 6.7") 158.6 cm (5 2.5")Colombia 170.64 cm (5 7.2") 158.65 cm (5 2.4")Cote dIvoire 170.1 cm (5 7") 159.1 cm (5 2.7")Czech Republic 180.3 cm (5 11") 167.3 cm (5 6.0")Denmark 180.6 cm (5 11.1")Dinaric Alps 185.6 cm (6 1.0") 171.0 cm (5 7.2")Estonia 179.1 cm (5 10.5")Finland 178.2 cm (5 10") 164.7 cm (5 4.7")
    • 97 | P a g eFrance 174.1 cm (5 8.5") 161.9 cm (5 3.7")Ghana 169.46 cm (5 6.7") 158.53 cm (5 2.4")Gambia 168.0 cm (5 6.1") 157.8 cm (5 2.2")Germany 178.1 cm (5 10") 165 cm (5 4.9")Guatemala (Maya people) 157.5 cm (5 2") 142.2 cm (4 6")Hong Kong 170 cm (5 7") 158.8 cm (5 2.6")Hungary, Debrecen 179.14 cm (5 10.4") 165.84 cm (5 5.2")Iceland 181.7 cm (5 11.5") 167.6 cm (5 6")India 165.3 cm (5 5") 165.3 cm (5 5")Indonesia 158.0 cm (5 2.2") 147.0 cm (4 10.0")Indonesia, East Bali 162.4 cm (5 3.9") 151.3 cm (4 11.5")Iran 174.24 cm (5 8.6") 160.0 cm (5 3")Iraq 165.4 cm (5 5.1") 155.8 cm (5 1.3")Israel 175.6 cm (5 9.2") 162.7 cm (5 4.1")Italy - Middle & North 176.9 cm (5 9.7") 163.2 cm (5 4.2")Italy - South 174.2 cm (5 8.0") 160.8 cm (5 3.3")Japan 171.2 cm (5 7.4") 158.8 cm (5 2.6")Korea, South 175.26 cm (5 9") 162.56 cm (5 4")Lithuania 176.3 cm (5 9.4")Malaysia 164.7 cm (5 4.8") 153.3 cm (5 0.4")Malta 169 cm (5 6.5") 159 cm (5 2.6")Malawi 166 cm (5 5.3") 155 cm (5 1.1")Mali 171.3 cm (5 7.4") 160.4 cm (5 3.2")Mexico, State of Morelos 167 cm (5 5.7") 155 cm (5 1.1")Netherlands 184.8 cm (6 0.8") 168.7 cm (5 6.4")New Zealand 177.0 cm (5 9.7") 165.0 cm (5 5")Nigeria 163.8 cm (5 4.5") 157.8 cm (5 2.1")Norway 179.9 cm (5 10.8") 167.2 cm (5 5.9")Philippines 163.5 cm (5 4.4") 151.8 cm (4 11.8")Portugal 172.8 cm (5 8")Singapore 170.6 cm (5 7.2") 160 cm (5 3")South Africa 169.0 cm (5 6.5") 159.0 cm (5 2.5")Spain 170 cm (5 7") 161 cm (5 3.3")Sweden 180 cm (5 10.9") 166.9 cm (5 5.7")Switzerland 175.5 cm (5 9") 164.0 cm (5 3.8")Taiwan 171.45 cm (5 7.5") 159.68 cm (5 2.75")Thailand 167.5 cm (5 5.9") 157.3 cm (5 1.9")Turkey 173.74 cm (5 8.4") 161.4 cm (5 3.5")United Kingdom 176.8 cm (5 9.6") 163.7 cm (5 4.4")U.S. 178.2 cm (5 10.2") 164.1 cm (5 4.6")Vietnam 167 cm 156 cmThe only gene so far attributed with normal height variation is HMGA2.Genetically speaking, the heights of mother and son and of father and daughter
    • correlate, suggesting that a short mother will more likely bear a shorter son, andtall fathers will have tall daughters.Today the tallest race of humans is the Nilotic peoples of Sudan such as the Dinkathey have been described as the tallest in the world, with the males in somecommunities having average heights of 1.9 m (6 ft. 3 in) and females at 1.8 m (5ft. 11 in).Disabled World - Disability News for all the Family: http://www.disabled-world.com/artman/publish/height-chart.shtml#ixzz27NbbvGJFAverage heightThe estimated average height of the human male in the overall worldwidepopulation currently stands at 1.72 m or 67.7 in. Economic advantages lead to anincrease in the average height, although genetic background does set higherstandards for some ethnic populations. American men 20 years and oldercurrently average 69.4 in. in height.In other words the average height of a man using are trolley we can presume tobe 5.75 foot or 175cmhttp://www.livestrong.com/article/289265-what-is-the-average-adult-male-height/#ixzz27NhzqAibArm lengthThe average male arm, from shoulder to finger, is about 75 cm or so, slightly less.Women come in at about 71 cm, not that much shorter than men. Therefore thetrolley does not need to vary a lot for it to be at ideal height for both men andwomen. Having said that, if a large object is being carried adjustable arms will bevery helpful. The final design chosen has arms of a considerable variation inlength.