Mechanical Elevator Device - Report Example

Running Head: Mechanical elevator device Mechanical elevator device Your full name Your ID no. Unit code and name Lecturer name Assignment October 28, 2015 Executive summary The project aims at utilizing mousetrap power to design an elevator for small payload and also making use of free stand pole. This project has been selected after comparison with other three available options based on different features. Most important customer requirements have been selected by conducting a customer questionnaire. This is followed by selecting project aim and objectives and development of project plan so as to meet them. Design criteria, requirement and constraints are listed in a tabular format which is led by Product design specification, functional decomposition and concept generation. The generated concepts are rated using Pugh’s matrix and finally the concept is selected based on the ratings. The selected concept would be designed, developed, critically analysed in the next phase of the project. Table of Contents Executive summary 2 Product designed specification 4 Concepts and evaluation 7 Option 1 - A pulley system 7 Option 2: Catapult elevator 10 Option 3: Scissor lift 12 2.3 Evaluation 16 Detailed Design Stage 20 Failure mode and effect analysis 20 
Manufacturing details 22 Cost analysis 
 22 SolidWorks 3D models 23 Conclusion 26 References 27 Product designed specification The aim is to design the device that will travel through the hole in the self which has a pole. The device should have the ability to carry a small weight of 50 grams specifically as spherical shaped load. The device should have the ability to drop the small load onto the self. The device should be powered using the spring of the mouse trap and should be measured 150mm by 150mm by 150mm. The device will be able to lift the payload through a hollow a free-standing pole before dropping it onto a shelf as shown in the diagram below; Figure 1: sketch of free standing pole The elevator will be able to lift the load to shelf as shown above and payload will pass through PVC pole. The device will be mousetrap powered elevator without changing the spring of the mousetrap. The device will be able to lift the payload one way that is from the ground to shelf. The following specification constraints and criteria is will guide the design of the device; No. Subject Details 1 Performance Lift a small light weight of 50grams or less Powered by an unmodified mousetrap spring. Will be within PVC pole all the time Drops payload safely without affecting the users. Is likely to show very high performance and efficiency. Their performance would also depend upon the material used for their construction and the amount of rate of lifting payload. Stable thus will not fall Their efficiency is predicted to range from 80 % to 90 %. 2 Installation & maintenance Easier to installed and maintain and does not technical know how. Maintenance cost incurred during their service life would also be very low Requires annual maintenance for efficiency service. The servicing will include the inspection of container, mousetrap spring, shelf and lifting structure. 3 Materials The materials for the device should have light weight Moderate shear strength, moderate modulus elasticity, corrosion resistance, 8% elongation, damage tolerance, moderate yield strength and ultimate tensile strength. 4 Safety The product will have sharp edges that can cause injury The payload will remain the PVC free standing and therefore will fall and injure any user For better performance there is need for regular checks of its safety. If the changes are required to meet the safety standards then they would be performed. 5 Production the production will be 100 units to test the market before annual production of 1000 units 6 Life span The device a life span of 6 years It dose not have ability to working 8 hours continuously but can work 30 minutes continuously. Spare parts easily available 7 Size and weight the device will be 150mm by 150mm by 150mm Weigh 500 grams thus will fit within PVC pole. Weight would also depend on the material used for manufacture of these products 8 Competition These products have not been implemented widely thus they are unlikely to face tough competition in market 9 Environment Produces less noise Can operate in normal room temperature across the world No emission of gas in the spirit of sustainable development. improve the ecological environment and maintain the ecological balance Corrosion resistance materials 10 Target product cost Costs $80 Packaging costs is 15% of cost of production The actual cost would be calculated after design and development phase 11 Packing The cost of packing is estimated to be low as the size of products would be small. 12 Testing After design and development phase, their prototype would be developed and tested in real conditions. This would be followed by their implementation in real life. 13 Time-scale Time-scale for project is set as 6 months within which design and development phase should be completed. 14 Quality and Reliability It is expected to improve quality and reliability of shelf. They themselves are expected to possess high quality and reliability 15 Customer Customer of these products would be libraries and homes and through them they will be utilized by other users 16 Ergonomics These devices would require maintenance after a certain period of time. So these should be designed in such a way that they are easily accessible during maintenance Can operated by an individual 17 Standards and specifications Standards and specifications would be defined during design and development phase. 18 Aesthetic, appearance and finish Aesthetic and appearance are estimated to be good but would depend on the material selected by designer Concepts and evaluation Option 1 - A pulley system The pulley system is the first designs related to motion which uses a cable being looped between pulleys that can are operated in the opposite directions. The mechanism is situated at centre while the other also rotates to make it work. The operation is controlled and moderated by adjusting the cable with the pulleys. What must be stated here is the level of accuracy necessary in order to achieve this, due to the dowels and holes created in the drums having to match identically to each other. It does not have motor but powered by mousetrap spring thus the rate of movement is to be controlled by hand and the lifting jib can also be moved to work in confined spaces without having to dismantle it. Mild steel was selected for the frame and consists of a small percentage of carbon ranging from 0.15 to 0.30 and has a density of 7870 kg/m3. The tensile strength has a maximum value of 50 MPa and a young’s modulus of 210,000 MPa. In order to select the appropriate cable, it is important to analyze the breaking limit of the rope to measure its strength. Hence, the team has decided to go with the stainless steel cable numbers 6X37 Class which provides extra flexibility and corrosion resistant properties. Moreover, the larger the number of wires used, the more the flexibility leading to lower resistance to pressure and abrasion. Even though this cable is a bit expensive compared to others found in the market, it is found to be the most suitable and safest material one can use. Figure 2 Breaking Limit for the cable Pulley Sizing- A pulley system is a circular wheel consisting of a single groove between two flanges found around the circumference. For our case, a cable is placed inside this PVC pole allowing to change the direction of the force being applied either rotational or linear movement. The pulleys being used are of the same diameter which gives the advantage of maintaining the same force while the direction changes. Figure 3 Pulley system If the cable is strong enough the pulley system is very reasonable in terms of price, construction and operation. Its maintenance cost is less as well due to the inexpensive spare parts. Container internal volume V=h x b x l = (150) x 150 x (150) =3,375,000 mm3 Stress = Proposed load to carry is 50g and load value of container is 500grams. The total load is 550grams or 0.55kg Area is 150mm by 150mm = 22500mm2 or 0.0225m2 Stress = = 24.44kg/m2 Mousetrap force Force = mass x acceleration (gravitational acceleration) Force = 0.55 x9.8m/s2 = 5.39N Option 2: Catapult elevator This option will look as follows Figure 4: construction of device Linear motion of catapult The height of the payload arm– 0.025 meters The gravitational -10 m/s2 The angle of cantilever with mousetrap spring 50o (vsin50º)2 = mgh ½ (vsin50º)2 = (-10 m/s2)(0.025m) (vsin50º)2 =.50 m2/s2 vsin50º = 0.707m/s v=0.92m/s 0.92 m/s =0.92.0 m/s = 0.705 m/s and 0.59 m/s 5= t(0.705 +t) the payload goes up only dy=5 0= (0.705 t +t2) -5 = 6.2s Conservation of momentum: Payload weight 0.05 kg and container weight 0.5 mv1 = mv2 0.55kg (0.92 m/s) = m2 (0.92 m/s) M2 = 0.55 Mousetrap spring potential energy ½mv2 = ½kx2 ½(0.55)(0.92)2 = ½k(0.025 m) 2 k ≈ 74.5N/m Stress = Area is 150mm by 150mm = 22500mm2 or 0.0225m2 Stress = = 24.44kg/m2 Strain = stress/ Young's Modulus Strain = 24.44kg/m2/ 24.4 x106N/m2 Strain = 239.674526N/m2/ 24.4 x106N/m2 Strain = 9.8x10-6 Elongation F is applied force, S Stress, Young modulus elongation and L is length Force = mass x acceleration (gravitational acceleration) Force = 0.55 x9.8m/s2 = 5.39N Elongation 2.67X10-9m Stiffness Where T is tension of spring force is 40 N, k is stiffness and is 2.67X10-9m Thus k = = Stiffness, k = 1.5X10-10N/M Option 3: Scissor lift This is another design for a elevator device that will lift up the pay load and powered by mousetrap string as shown in figure below. For the container for load to come down, the lower portion should be free from force exerted by mousetrap spring which turns out to be a disadvantage as well. Moreover, this type of support experiences a lot of stresses due to the load on top causing deflection and over a long period of time could result in failure if not made from a strong tough material. This system will require a large space beating the logic of free standing pole and it is costly. The following design will also be considered in our design; Figure 5: Scissor lift Movement calculations- It is important to know how slow or how fast the still should move from down to up or vice versa. I have decided that the time taken for the container to reach the beginning of the shelf should last 20 seconds in order to maintain high safety factors. Once it reaches this shelf, the descending motion should approximately move at a speed of 0.060 m/s giving us a calculated time of 15 seconds. Structural Analysis- It is extremely important to conduct a structural analysis on every design where safety is a huge factor needed to be considered because it helps to identify the stress points and how to make it stronger in order to withstand the load. The solution usually ends up by increasing the dimension or by using another material. The load applied was 0.550 kg including the load and platform and the material selected was mild steel which has a relatively high tensile strength of approximately 50 MPa. Figure 6 Analysis conducted As shown from the above figure, higher stressed points are the joint. However, the stress is at an acceptable level because it is part of the blue region rather than red. The safety factor calculated is: Figure 7 Connection Stresses Stress Calculations- This is very important in ensuring material used are not strained beyond capacity. We begin with bolts and pins helping to attach the various components together. The triangular beam supports are fixed onto the frame hence not exhibiting and shear stresses when the payload is lifted. However, once movement begins shear stress is present in the structure because it resists the entire weight of the car from the beginning till it descends completely. Stress = Proposed load to carry is 50g and load value of container is 500grams. The total load is 550grams or 0.55kg Area is 150mm by 150mm = 22500mm2 or 0.0225m2 Stress = = 24.44kg/m2 elongation = Elongation = = 0.582mm E = stress / strain Strain = = 0.000116m Bolt Calculations - To decrease this stress, it is advised to use a bolt to distribute the stresses. To know which bolt would be most reasonable for this application, certain calculations are needed as shown below: A specification sheet card is available as shown below from which the bolt will be selected. For this case for safety reasons M10 is chosen which has an allowable load of 429kgf. Figure 8 Specification Sheet Card Pin Calculations- The scissor lift consists of a movable pin which allows the movement of the container carrying the payload. The diameter of this pin is necessary and is calculated as follows: Where F = N and  = 27.5 MPa 2.3 Evaluation Design requirements and criteria need to be focused upon while developing the concept for resolving the problems recognized from the customer feedback. Using the details collected in the initial concepts, background research and ideas generated earlier, for further developing a complete design keeping in mind the primary requirements of customers. The creativity and skill of group members would be utilised to find solution to identified requirements of the customer. Thus each group member will work autonomously, so as to fully exploit his skills, ability and intelligence to develop the initial ideas. Detailed research would be conducted on each idea so as to fully develop them. This would be followed analysis and discussion on the efficacy of each concept using Pugh’s Matrix. The options elucidated above would be compared using Pugh’s Matrix. Each option would be evaluated for all the set of design criteria and their total scores have been compared. The method with the highest score would be opted for the final design. This would be led by the comprehensive design and development of the final method using various design software which would be followed by failure mode and effect analysis (FMEA) would be done. This would be followed by reliability study for the final design so as to make it safer, reliable and sustainable. Lastly the conclusion would be assessed; the impact of the developed product on various features selected from customer feedback in the earlier chapters would be made. Pugh’s Matrix for selection of options  Selection Criteria   Option 3: Catapult elevator Option 2: Scissor lift Option 1: Pulley system Cost 15% 4 Less materials 3 Wide PVC pole which will be costly 3.5 Costly gears Reliable 10% 5 Carries payload for 3 hours continuous 3.5 Carries payload for 2 hours continuous 4 Carries payload for 3 hours continuous Sustainable 5% 4 Emits no ozone gas 3 Environmental friendly materials 3 Environmental friendly materials Safety 20% 5 Very simple loading with high weight 3 Hanging payload container 4 High safety Space Required 10% 4 Fits in 6” PVC pole 4 Requires PVC of more than 6” 4.5 Fits in less 6” PVC pole Manufacturing 5% 5 Simple 2 Requires pins and bolts and no gear 4 Requires two gears Maintenance 10% 3.5 Easier 2.5 Requires extra tools 4 Easier and no skills Durability 5% 4.5 Last 8 years 4 Last 6 years 4 Last 6 years Efficiency 20% 5 Delivers payload at 0.9 m/s 3.8 Delivers payload at 0.78 m/s 5 Delivers payload at 0.9 m/s Total score  100% 3.925 2.935 3.6 From the above Pugh’s matrix option 3 has highest score of 3.925. Thus the option 3 concept is selected as final concept. When looking at the differences between the options, the catapult is best but the main areas of real innovation have been our understanding of use mousetrap. The movement resembles a pulley and pinion system where the members move in order to place the payload in or outside the free standing pole. The payload comes on the upper flat shelf of the pole and will move alongside till it returns to the ground. In order to withstand the weight of the payload, a supporter is attached helping to strengthen the belt as well performing the operation more safely. The belt is further attached via a chain or a cable which will help the payload descend or ascend smoothly. This cable is connected to the wheel selected along with the pulley system helping to allow easy movement of the system as a whole. In future stages of the project the idea of option 1 would go forward for product design and development phase. This would be followed by generalization of these products. The basic features which have led to the selection of options are: cost, efficiency and maintenance cost. This can be built at very low cost and requires very low maintenance. The other advantage is that it is highly efficient and can effectively increase the lifting efficiency of the payload. Comprehensive Design would be made using Auto-Cad software in the next stage which would be followed by design validation and design verification. Primary Sub system Flowchart The following is a flowchart for the small payload elevator device system. A flowchart is important in getting an overall view of the small payload elevator device system and the various components it is comprised of as shown below where the dotted line represent connection between the components: Figure 9: Primary sub-system flowcharts Detailed Design Stage Designing is very important in small payload elevator device system as it allows components to assembled using proper dimensions. It will be designed in a manner that will take a shorter time to lift payload safely. This is a multi-task activity because, the small payload elevator device system will not only required to carry out one activity but many. However in order for payload to be lift easily, the system capability and characteristics of the materials plays. In designing the small payload elevator device system three variables are involved weight, material straight and speed. Structure- There are completely four components the entire structure is divided into as shown below which are further described separately and they are Support frame, Top plate, Triangle support beams, Rollers and Rubber stand for scratch prevention Failure mode and effect analysis As is referred in references, the delamination in structures subjected to in a plane loading is a subcritical failure mode whose effect may be: 1) Stiffness loss that is begins in terms of the structural failure. 2) A local tensile strain concentration in the load bearing piles that cause tensile failure. 3) A local instability that causes the delamination leads to redistribution of structural load paths, in turn, precipitates structural failure. The mechanism of failure mode is given by quantitative measure using strain energy releases. The strain energy release rate given as by [ Gic= -dU/ Bda =-du/da Where; U= total energy of the system B= Uniform thickness of the body da = small change in crack propagation dU = proportional energy change due to da dA= corresponding variation of the crack area for the respective infinitesimal crack propagation (dA=Bda) However; the strain energy release rate depends on the great number of parameters. Among those parameters on may include matrix structures, reinforcement volume fraction, existence of matrix-rich and matrix-poor region, specimen lay-up, loading rate, environmental, time and temperature to study the effect on break out. 
Manufacturing details The product will be manufactured using the existing facilities among small scale manufacturers where by 100 units will be produced in the first case then will be increased when the demand is increased. The cost of manufacture will reduce when production increases due to economies of scale. Production will also be outsourced because the designers are students who may not have the capacity to finance large scale production. When we began this project, it appeared there would be many avenues for innovative design elements. However, as time went on we began to realize that e-bikes are currently widely available commercially particularly in the overseas market. Since their initial appearance, several decades ago the design has evolved fairly standard solutions to this problem. Out project, by and large follows on one of these standard approaches simply to make use of the commercially available that fit this application perfectly. Hence we have not deviated much in the way of innovative designs from the methods that have currently proven successful. This was necessary to minimize the overall cost of the product. Cost analysis 
 Cost is an important element that has to be taken into account when one designing with an aim of attaining high safety standards Description Quantity Unit Per unit Total Value Wheel 2 100 7.65 1,530 Rods 8 100 8.5 6,800 Container 1 100 4.75 475 Labour cost 52 5200 Mousetrap spring 1 100 25 2500 Total cost for 100 units 16,505 Cost per unit 165.05 However benefits can not be evaluated as Cost-Benefit Analysis enables the estimation of money value of the project. But this is taken into account when risk is reduced since human life can not be valued. Risk is managed so as to achieve project objectives in terms of cost and safety but safety can not be sacrificed at expense of Cost-Benefit Analysis. Of most importance is the human life since it is difficult to find a project whose safety equals the Cost-Benefit Analysis. The risks affecting costs include politico-economic factors and legal problems, inflation and technical problems. SolidWorks 3D models The final design drawing of the elevator device has been made and screen shots of the drawing are shown below. Simulation was done for duration of 0.6 seconds where the time interval was 0.003 seconds. The force which was applied on the lift of the system was 0.55N. Figure 10: Catapult systems Figure 11: lifting arm Figure 12: PVC Pole There have been accurate analyses meant to figure out very well the internal structure of a bearing so as to provide frequencies that is the appropriate one for each catapult. This is meant to reduce the various problems that do arise from the catapult especially if they have been in use for a long time. During the calculation of the various frequencies used in the bearings, the calculations do require one to know some basic information that is typically known. For example, the typical information includes the diameter: inner and outer size, particular number of wheels and their sizes. However, there are some manufacturers that do change particular internal designs so as to complicate the specifications. Consequently, the specified bearings sizes are not changed. What the manufactures guarantee is that the typical information concerning parameters: size, speed or load deployed: is not easily known. As such, the vibration analysis to monitor the lifting speed of the catapult is dependant on such factors. Consequently, there is still a need to develop a particular universal monitoring device that does utilize a particular common as well as a statistical based algorithm which is not limited to a particular type of catapult. The machine must be able to generally use the properties regarding the vibration analysis especially when during the concept of proactive maintenance when it comes to catapult. Conclusion In the production, design, modelling and simulation of elevator device various methods and testing are done to ensure that it works at the minimum without any effect. The designed elevator device was a simple model and was done successfully. The pictorial representation of the model parts has been made. The designed elevator device has the capacity to withstand modulus of elasticity of 21000MPa has yield strength of 500MPa. The density of aluminium was 27000kilograms/m3 and elongation of 0.08%. References Eisner, H., 2008. Essentials of Project and Systems Engineering Management. Hoboken, N.J.: John Wiley & Sons. Hyman, B., 1999. Fundamental of Engineering Design. New Jersey: Prentice Hall, Lumsdaine, E., Lumsdaine, M. & Shelnutt, J. W., 2008 Creative Problem Solving and Engineering Design. New York: McGraw-Hill, Inc.. Read More