Mousetrap Powered Elevator Device - Report Example

Mousetrap Powered Elevator Device Student University Abstract The main aim was to design mousetrap powered elevator that can lift payload of about 100gs from the ground through a pole of diameter 150mm to the shelf which is 450 mm tall. Two concepts were considered and evaluated based on the available constraints. The best option was selected and recommended for designing. The designed device was powered by the energy of a wound-up mousetrap spring. The design has been done at same time sketches made in solidWorks. The elementary design of the powered mousetrap is one where one side is tied to a string on the tip of the mousetrap snapper and the other end of the string has a loop that is developed to hold a hook which is firmly glued to the axle drive. The lever arm is pulled closer to the drive as the string is wounded around the axle by the turning wheels. This has the ability to help the mousetrap’s spring to wind up and store the required energy. The string is pulled off the axle drive when the driver wheels are released and this caused the wheels of the mousetrap to rotate. Table of Contents Abstract 2 Introduction 4 Product designed specification 4 Concepts and evaluation 6 Detailed Design 8 Failure analysis 15 Cost analysis 16 SolidWorks 3D models 18 References 25 Introduction This write-up presents the design of an elevator powered by mouse trap spring. The main objective is to carry a payload on the ground up the a vertical poll and drop this payload on a rack hanging up the pole a distance 450 mm from the ground. The pay load has the go through a 150 mm at the center of this rack as can be seen from the figure below. in this design it is desired that the system carry high amount of payload to utilize all available power and move it to the desired location. Two failure designs will also be presented which will outline the advantage of using this design instead of the two failure designs. Product designed specification No. Subject Details 1 Performance, quality and Reliability Energy release must be faster and quicker with a minimal applied force. Applied force must be sufficient to cause energy release without extra requirement or tools The system must withstand external disturbances other than the force applied to cause energy release. 2 Safety Must not have sharp points that might injure the operator in case of an accident Must transmit energy to the appropriate direction to avoid injuring either or both the operator and observers. Must transmit enough energy during the operation without excess to avoid making the payload move beyond the required point of the shelf where it should settle. 3 Service Life System must be long lasting under maintenance. System must transmit energy long enough during the time of operation. System must stay for long without failing, approximately 10 years and above. 4 Ergonomics Full energy must be transmitted to the driving of the elevator, no wastage of energy Must not interfere with the operator 5 Size and weight System must light enough The system must be compatible with the available and existing elevators. 6 Installation and Maintenance Should be easy to install The maintenance requirement should be minimal. 7 Materials Minimizing the use of expensive and exotic materials High strength and light-weight materials 8 Quantity Production must be high enough for economic production 9 Testing The system should be tested to ensure that the system is stable at certain diverse conditions such as vibrations. CONSTRAINTS Must be compatible with the existing elevators System must not need an additional tool in order to transmit power to the elevator Must transmit full torque to the load Must not need specialized steering wheel or column CRITERIA The designing concepts are rated between 1 and 5 based on the following criteria: Weight of the overall system: The overall weight should be light for better performance. Rate of energy release: The higher the rate of energy releases the reliable the system is. The manufacturing volumes: the higher the volume of production per year the better the concept Safety of the system: The system must be safe to operate and use without causing an harm to the operator or any observer. Cost: low cost in the production and maintenance, the better the system Concepts and evaluation Concept 1: Gear Drive The concept is based on the use of a chain of gears in transmission of energy and torque to the wheels of the elevator. Energy from the mousetrap is transfer to the wheel of the elevator by means of use of the gears that are coupled. These gears are arranged in a decreasing ratio of the number of teeth from the driving gear to the driven gears. This ensures that the increase in the speed of response of the elevator and the torque is reduced. This is because the payload is made up of a small lead weight material that does not require high torque (Job Service North Dakota, 2010). Concept 2: Belt Drive The concept describes the transmission of energy between the mousetrap energy and the elevator. The energy from the mousetrap is transmitted to the elevator’s moving parts by means of belts. The driving wheel of the mousetrap is smaller than that of the elevator in order to increase the torque and reduce the speed of the moving parts of the elevator (Job Service North Dakota, 2010). Evaluation The concepts were evaluated based on the criteria highlighted above by means of the following weightings: Weight of the overall system (20%) Rate of energy transmission (20%) The manufacturing volumes (15%) Safety of the system (30%) Cost (15%) Table 1: Summary of the Evaluation of the Concepts Weight of the overall system (20%) Rate of energy transmission (20%) The manufacturing volumes (15%) Safety of the system (30%) Cost (15%) Total score Concept 1 1 - big and heavy materials used in the manufacture of gears are used 4 -Low rate of energy release 1 - More time required in the manufacture and assembly of the components. 5 -Gears don’t rise high enough to cause injury to the users in case of accident 2 -Cheap due to use of locally available material in its production 2.6 Concept 2 5 -Low weight due to use of rubber as compared to metals 3 -Energy released faster due to elasticity and hence faster movement of the elevator 2 -Less time in the manufacturing the belts and assembling them 3 -Rises high during a facture 2 - High cost of purchasing the materials 4 Based on the above evaluation of the two concepts, I have chosen concept 1 because of the high standards of safety attached to it as compared to the overall rating of concept 2. In addition to that, the materials used in the production of the gears are readily available as compared to those used in making rubber and as a result is makes it cheaper than rubber. In addition, the energy transmitted using the gear transmission method is higher than that of belts. This is due to low energy loss during the energy transmission. The safety measure to the elevator system is important than the overall performance of the elevator in in terms of the all the constraints considered in the conceptual design (Job Service North Dakota, 2010). Detailed Design The design utilizes the mouse trap that is rigidly by two mounted on a two wheel car. The wheels are made by tightly held old DVD. Each wheel is made by 6 DVDs which are held together by two nuts. The entire assembly is mounted on a heavy bolt which serves as an assembly component and a weight. In this design a nut is used as the payload and it is pulled by a weightless thread which is attached on the car. It will use the mouse trap lever to pull the payload up the poll. The lever end is attached to a thread and this thread tied to the payload to (nut) on the other end. When the mouse lever is set free i.e. from the set point the potential energy of the spring set the lever in a rotation motion therefore pulling the pay load up the poll. At the end of the impact of the lever to the mouse trap base makes the entire assembly to roll over. This pulls the payload even further up the pole. The payload load to be loaded at the end of the string is such that the payload will finally settle on the rack therefore accomplishing the purpose of this design. The construction will begin as shown in the diagram below; This will be constructed as follows Figure 1: wheels and shelf sketches Wheels will be made from old CD’s though they have very little attraction. The stretch a wide rubber band on each and every wheel, the rubber band may be even glued in the place. Pull cord needs to be very strong enough to withstand the forces that exerted by the mousetrap spring. The friction is experienced in between the wheels causing the car performance to reduce. With increase in friction, there is need to increase energy to maximum the performance of the car. Fixing the wheel in the device- To fix the wheel after construction one will need axles, a fixing strip, a supporting strip and a strip that creates space when the wheel is moving. This means one of the axles from the created is movable and it is fitted with controlling cables which are supplied with power from mousetrap springs to act as brakes. Bolts are fixed to spacer strip which has a drilled 10mm diameter also the support strip will have a bolt of 10mm to enable it carry the front axle. A screw is used to fix the strips together and it also inserted to a hole that is drilled into the Pole. The following are the springs and bolts that will be used in the device; Figure 2: Bolts, nuts and springs for the design Bolt – The bolt used has a diameter 5mm and length of 27mm and this will help in decreasing stress of the payload. The mechanical advantage of the bolt is calculated as Mechanical Advantage = where r is radius and l is length Mechanical Advantage = = 1.16 Since there are 4 bolts in the car and will carry load of 100g and weight of the lift car is 500g , we need to calculate the load experienced, and allowable stress on bolt: There total mass is 600g Force = mass x acceleration where Acceleration is 10m/s2 Force = 0.6 x 10m/s2 = 6N Spring- mousetrap spring is the source of power Figure 3: structures of the other parts of device lever and linkage) lever and linkage) Wheels and Axles The height of the pole– 0.45 meters while gravitational acceleration is -10 m/s2. The angle at which load is lifted fro to the shelf is 50o. Linear motion analysis of the device We begin by calculating velocity for the device along (vsin60º)2 = mgh ½ (v sin60º)2 = (-10 m/s2)(0.045m) v=0.1.2m/s 1.2 m/s =1.2 m/s = 1.04 m/s and 1.04 m/s 0.45= t(1.04 +t) the payload goes up only dy=0.45m 0= (1.04 t +t2) -0.45 = 1.06s Conservation of momentum: Mousetrap spring potential energy ½mv2 = ½kx2 where m is mass to lift by spring V is velocity of spring, x is distance travelled and k is stiffness Stiffness, k = = = 3.2 k ≈ 3.2N/m Stress = Area of bolts is = 2 Area of bolts is = 2 Area of bolts is = 1.6m2 Stress = = 37,500N/m Young modulus selection of materials for spring Strain = stress/ Young's Modulus Strain = 37500/ 2 x10-9N/m2 Strain = 1.875x10-9MPa Elongation F is applied force is 6N, Young modulus elongation and L is length 3.84X10-7m Power of the spring Failure analysis Failure analysis defines as natural consequences of failure in the matter of the device. This reflect the “true “and “correct “principle was practice before formal in analyzing data collection and analyzing for failure thus usually be self evident and leads inevitably to design modifications. Some of the expected failures are; Loss of Stiffness loss of the spring Stiffness loss Elongation of the spring Buckling of the wheels Tensile strain concentration Fatigue Manufacturing Techniques of the Chosen Concept The process of manufacturing this device will need the use of precision pillar drill and grinder, PVC pole. Some other items that will be needed are Jigsaw, screwdriver, Router, circular saw, sander, drill bits of 10mm and 15mm, countersink, spanner, paper, pencils, rubber, sharpener, and metre stick. The drilling will help in creating holes on the wooden whereas the grinder will be used cutting or smoothing sharp areas of a metal. The hole will be bore at the bush to fit the front part with diameter of 10mm to ensure that the wheel is centred at the end of the shaft. The bush will be glued to base disc in the box which will have blanks that are cut to fit the system. Cut the circular part to make teeth at its edges at regular intervals to make gears and arrange the gears in a series starting from the largest to the smallest from the mousetrap power source. This is to ensure that the torque is compromised for the expense of speed of the power transmission from the mousetrap to the elevator. These gears will be arranged in such a manner to ensure that they firmly gripped In order to have a wheel that spins at a velocity of 6.93 rad/s we need 150mm diameter wheel that connected to a 10mm diameter shaft that which passes into the mousetrap via the 60o face. Once one has been manufactured then 100 pieces will be manufacture to test the market with. When demand increases then production will increase to 1000 units per year for the net two years. Cost analysis It is imperative that the we should have detailed understanding of the costs structures. The production/manufacturing stage ensures that the product that is made is cost effective, appropriate for the target group safe for consumption over a long period of time.The process costing summary is as shown below; Description Quantity Unit Per unit Total Value Wheel 2 100 2.5 500 Bolts 4 100 0.5 200 Nuts 8 100 0.25 200 Disposable Tools 100 100 0.025 250 PVC pole 1 100 5 500 Labour cost 100 10 1000 Mousetrap spring 1 100 12 1200 Total cost for 100 units 3,850 Cost per unit 38.50 From the above Process costing pricing summary, it is evident that the item will cost $35.50 per unit. This can better be illustrated by calculating the percentages that is represented by each process cost channel as shown in the table below:- The product will face competition from other players and in order to maximize profits, the we must ensure in future we to cut on costs by taking up on the appropriate costing system and forming a niche in the already competitive market. The costing model presented in this report is supposedly the most viable alternative that fully integrates a transparent costing system that is easy to implement. SolidWorks 3D models Mouse trap car assembly Lever Bolt and nut Spring References Job Service North Dakota. (2010). Manufacturing, Bismarck, N.D.: Job Service North Dakota (Job Service North Dakota, 2010) Smith, D J (2011), ‘Reliability Maintainability and Risk’ 8th Ed,Butterworth-Heinemann,UK L-B, Z., L-J, W., & Liu, X., (2001), ‘A mechanical model for predicting critical thrust forces in drilling composite laminates’ Proceedings of the Institution of Mechanical Engineers, 215(2),pp 135-135. Mihai-Bogdan Lazar, Paul Xirouchakis,(2011), ‘Experimental analysis of drilling fiber reinforced composites’, International Journal of Machine Tools and Manufacture, Volume 51, Issue 12, Pages 937-946, Read More