EGB111 Design Report 7D PDF

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Summary

This is an EGB111 example from 2020 for this unit....

Description

contribution to the conduct of the design project and the generation of this document. Each signed author also attests that they acknowledge the fair contribution of all other listed authors, and that if a team member is not included in the signed authorship list, the team has discussed this with the unit coordinator and this course of action is supported by the unit coordinator.”

EGB111 PROJECT REPORT 2021 Group Number 7D

Davin Do: n10809058 Dheemant Kripal: n11045108 Hamish Robson: n11029072 James Martin: n11052066 Jayden Poh: n11039655 Kevin Mathew: n11039671

DD DK HR JM JP KM

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I. STATEMENT OF CONTRIBUTIONS (ONE PAGE) A statement of contributions must be included as part of the report. This needs to indicate what section of the report each team member wrote. It also needs to indicate what technical component(s) of the report each group member worked on. Technical components are: Structural Design, Mechanical Design and Circuit Design. If the group believes that one or more members have made insufficient contributions to the project, then a percentage contribution should be provided for each team member. Group marks can be modified for individuals with insufficient contributions given that evidence is provided (documentation and meetings with project managers and tutors). *The percentage contributions should total to 100% Team Member

Report Written

Davin Do

Final Design Recommendations and Conclusions

Structural Design

Design Performance Evaluation,

Structural Design

Dheemant Kripal

Sections Technical Contributions

Percentage Contribution 16.67%

Mechanical Design 16.67%

Mechanical Design Circuit Design

Hamish Robson

Structural Design

Structural Design

16.67%

Mechanical Design James Martin

Mechanical Design, Circuit Design

Structural Design

16.67%

Mechanical Design Circuit Design

Jayden Poh

Conceptual Design

Structural Design

16.67%

Mechanical Design Kevin Mathew

Introduction, Executive Summary

Structural Design

16.67%

Mechanical Design

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II. EXECUTIVE SUMMARY (ONE PAGE) Throughout this report, various components of the design such as the structural, mechanical, and electrical were built in order to meet the standards of the criterion. For the structural design of the crane, it was decided that the top supporting truss would be built out of 5x5mm balsa wood, with a truss design similar to a howe and pratt truss. This was decided so the diagonal members of the truss would be in tension while the vertical members would be in compression. This proved to be very effective when constructing the truss and proved to be very strong and able to lift the desired weight of the 500g mass. The type of crane design that was chosen for this particular project was a similar to a tower crane design. When constructing the base of the crane it was decided that HDF wood would be laser cut to develop the tower crane. Once the base was made, it was then bolted to the top supporting truss, which provided a stronger overall structure within the crane. With the mechanical component of the crane, it was decided that two main gears along with a lazy susan bearing would be used to rotate the crane from one location A to B. With the lifting system for the crane it, a strong piece of string would be used to lift the object that would be fitted across the whole truss, thus distributing the load of the object evenly to the top members of the truss. As for the electrical component of the crane design, two motors would be used: one for the lifting system and the other for the rotating system. In the lifting system a gearmotor that is able to be stepped down up to six times was used, which would allow the torque to be adjusted to the right power when lifting the object. For the rotating system, a 12V motor that was attached to a gear would be placed on the truss, which was on the lazy susan bearing, which allowed the truss to be able to rotate up to 360 degrees. Once the crane was built, there were however some issues with the gears which ended up having small amounts of sawdust in between the motor and the gear. This issue was resolved by laser cutting new set of acrylic gears instead of using the wooden gears which provided a much smoother rotation for the crane. Another issue that arose was that the speed of the motor was too fast however, this problem was resolved by using a potentiometer, essentially known as a voltage divider which would allow the resistance to be manually varied to control the flow of current. Which would allow the speed of the motor of the rotating system to be controlled.

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Table of Contents I. Statement of Contributions (one page)...........................................................................................1 II. Executive Summary (one page)....................................................................................................2 1.0 Introduction (one to two paragraphs)...........................................................................................4 2.0 Conceptual Design (two to three pages including diagrams and figures).....................................5 3.0 Detailed Design (five to ten pages including diagrams and figures)............................................5 3.1 Structural Design.....................................................................................................................7 3.2 Mechanical Design..................................................................................................................7 3.2.1 Mechanical System Components..........................................................................................8 3.3 Torque Analysis.......................................................................................................................9 3.4 Speed Analysis.........................................................................................................................9 3.5 Power Analysis......................................................................................................................10 3.6 Circuit Design........................................................................................................................12 4.0 Final Design (two to three pages including diagrams and figures)............................................14 4.1 Design Peformance Evaluation (About Half One Page)............................................................16 4.2 Recommendations and Conclusions (about Half One Page)......................................................16 5.0 References.................................................................................................................................17 6.0 Appendices................................................................................................................................17

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1.0 INTRODUCTION (ONE TO TWO PARAGRAPHS) The primary objective of this design project is to design and construct a model lifting device to relocate an object from location A to location B. The object that will be relocated would have a mass of 0.5kg with a height of 50mm from location A to a pedestal with a height of 100mm at location B. The testing of this design will be conducted on a testing board on a scaled down version of Queens Park in Brisbane City.

A

B FIGURE 1: TESTING BOARD OF DESIGN PROJECT

As per the clients’ objectives for this project include the following:   

Complete the motion of moving the mass of 0.5kg from location A to B in under 1.5 minutes. For the design/model lifting device to weigh less than 4kgs Have a peak running power of under 10 watts with a max input voltage of 24V

Other factors that were considered that would influence the ability to build this design, are cost and constructability. As well as whether design the device to be fixed to the testing board or to be a nonfixed design. Also outlined by the client, was to design the device for optimal performance, but however isn’t mandatory. The device should:    

Complete the motion to relocate the object within 45 seconds Weigh under 1.5kg Have factors of safety between 1 and 2 for the electromechanical system to fail at 1kg Have factors of safety between 2 and 3 for the main truss to fail at a load of 1.5kg

Throughout the report various contents of design process will be outlined. Within the report conceptual design ideas will be outlined as well as the decision of a final detailed design, with the structural, mechanical, and electrical systems of the design to be considered. This involves relevant graphs, tables, diagrams and supporting mathematical calculations. To conclude, recommendations were also suggested in order to improve the final design if under some circumstances the task was decided to be redone.

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2.0 CONCEPTUAL DESIGN (TWO TO THREE PAGES INCLUDING DIAGRAMS AND FIGURES) Figure 2: Gantry crane design Gantry cranes are an overhead design, supported by two unfixed supports and are connected by a beam either in a single or double girder configuration. They typically have two motors, one responsible for moving the object vertically, the other for horizontal movement. Due to the requirements of the task, the beam would be replaced with a truss. This design is only capable of moving objects in a straight line unless the supports are capable of moving while the crane is in operation.

Figure 3: Tower Crane (Hammerhead) The hammerhead tower crane is widely adopted in industrial worksites. This simple design requires two motors, one for lifting the object vertically, the other for the rotation. This further adds to its simplicity as it requires fewer moving parts compared to other crane designs such as the luffing crane.

Figure 4: Luffing Crane Luffing cranes are widely used throughout the world due to its ability to work in congested areas due to their reduced slewing radius. They also have higher lifting capacities than tower (hammerhead) canes. They operate similar to a hoisting system, with a broom with cables connected to the top and the bottom being pinned. This cable is responsible for the moving the object horizontally, the other cable is responsible for lifting the object.

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Figure 5: Initial Design Concept Three types of cranes were initially considered: gantry, tower (hammerhead) and luffing crane. The gantry crane was dismissed due to the complexity of designing a truss spanning the two pedestals on the board and creating a system of moving the statue horizontally on said truss. The luffing crane was also dismissed as to required complex multiple moving parts to function correctly. The tower (hammerhead) crane was thus chosen for the final design due to its simplistic design and its ability to be easily built.

Finial Design: A modified version of the tower (hammerhead) crane was chosen for the final design. Due to the base where the crane will be bolted down not being equidistant, the decision was made to extend the crane to the centre of the board to ensure the truss can reach both pedestals without creating a system to extend the reach of the truss. The base supporting the crane was decided to be a 10cm x 10cm x 30cm made out of HDF. For the truss to be rotating in the centre of the testing site an extension/extrusion of 56cm x 10cm x 10cm added to the top of the base would be required. The centre of rotation would ideally be located in the centre of the board and would be powered by a motor. An additional motor will be located at the black of the truss and would be responsible for lifting the object. The main truss is to be made of balsa wood as the material testing revealed that the 5mm x 5mm balsa wood would yield the best results compared to the 3mm x 3mm balsa wood and the acrylic.

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3.0 DETAILED DESIGN (FIVE TO TEN PAGES INCLUDING DIAGRAMS AND FIGURES) 3.1 Structural Design The main structure of the crane body consists of two main pieces, these being the supporting base and truss. Detailed in the design brief the structure must meet a set of criteria to be fit for use. The main truss must be able to uphold a weight off 500g with an upper threshold of 1kg and be designed to structurally fail at a load of 1.5kg for maximum marks. This is to ensure that the projects built are not engineered for this design brief but still being able to safely lift the payload (statue) at a FoS of between 2-3. Since this project is primarily focused on the construction of the truss, the bass was able to be done in a much faster less calculated manner. In this specific design the base has been laser cut from a single piece of plywood and therefore acts as a beam rather than a truss as the pieces did not have any parts taken out from them and remained solid. The base is also bolted to the plate, all this makes any calculations regarding the reaction forces of the base come out as unrealistic and unusable.

The highest force forces of both tension and compression have been found using method of joints, these calculations can be viewed in Appendix 1. The forces in this system were calculated using a Pictured above are dimensioned CAD drawings load of 500g, however since the main crane truss consist of two individual trusses, they have of the laser cut base pieces. The vertical base each only been analysed for half the base load or 250g. The highest forces of both tension and (left) and the horizontal arm (right) compression are 20.79N and 9.8N respectively.

Figure 6: Base design in Autocad

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The failure load of this truss is tested to be above 500g with no exact value found as there was not enough time to test the truss to failure and rebuild.

Figure 7: Calculations for the balance and bolt reactions of the crane

The reaction at each of the bolts has been calculated in the figure above. The turning moment at the centre of the base has been calculated to be -4.63 Nm and the moment force created by the weight of the main truss has been calculated to be -1.23 Nm. The total turning moment around the base has been calculated to be -5.61 Nm. These numbers indicate that if the base of the crane were not bolted to a fixed plate that it would tip over from its own weight and also when a load is applied unless it is counter balanced with weights. The turning moment forces at the main joints of the project between the supporting truss and the base range from -5.10 Nm to -3.01 Nm. To ensure this does not cause catastrophic failure of the crane the base will remain bolted to the testing plate at all times.

3.2 Mechanical Design In order to allow this crane to do anything useful, an effective mechanical and electrical system was extremely crucial. This crane featured two major mechanical systems in its design.  

The first mechanical system was the lifting system. This system is responsible for being able to raise the statue from the first pedestal and lower it onto the second pedestal. The second mechanical system was the rotational system. This system is responsible for being able to rotate the truss of the crane from one pedestal to the other.

In order to design an effective mechanical system, calculations needed to be performed to ensure the correct mechanical components were chosen. There were many components that needed to be considered. This included the lifting motor, the gearbox, the drum and the pulley system. The chosen components were a 4.5V DC motor, 269:1 gearbox and a 1cm drum to lift the 0.5kg mass.

3.2.1 Mechanical System Components: Figure 7:Mechanical system

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Power Supply Voltage: 24V Current: 3A Power: 10W

Motor

Gearbox

Drum

Mass

Nominal Voltage: 12V Stall Torque: 0.0098Nm No Load Speed: 1256.6rad/s No Load Current: 0.25A Stall Current: 3.37A

Ratio: 269:1

Radius: 0.01m Efficiency: 100%

Mass: 0.5kg

3.3 Torque Analysis: Drum Torque:

τ drum =F∗r

−2 ¿ ( 0.5 kg∗9.8 m s )∗0.01m

¿ 0.049 Nm

Motor Torque:

τ motor =

τ drum GR∗η

¿

0.049 Nm 269∗0.25

¿ 0.000729 Nm

As the torque on the motor when lifting the 0.5kg mass is less than the stall torque of the motor, the chosen motor is sufficient to lift the 0.5kg load

3.4 Speed Analysis:

Speed (rad/s)

Torque vs Speed 1400 1200 f(x) = − 128228.27 x + 1256.64 1000 800 600 400 200 0 0 0 0 0.01 0.01

Values

0.01

0.01

No load speed

1256.63706 rad/s

Stall torque

0.0098 Nm

Gear Ratio

269:1

Drum Radius

0.01m

Torque (Nm) FIGURE 8: TORQUE-SPEED CURVE

From the Toque Analysis section, the torque of the motor while lifting the 0.5kg weight was calculated to be 0.001457Nm. Angular Speed of Motor:

0−Noload speed ∗τ motor +Noload speed Stall Torque−0 ¿ 1069.777 rad / s ω motor=

¿

0−1256.637 ∗0.001457 + 1256.637 0.0098−0

Angular Speed of Drum:

ω drum=

ω motor GR

¿

1069.777 269

¿ 3.977

rad s

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Linear Speed of Mass:

v mass =ω drum∗r drum

¿ 3.977∗0.01

¿ 0.0432 ms

−1

¿ 4.324 cm s

−1

3.4.1 Is it fast enough? Due to the time limit imposed on completing the move, the object needs to be moved fast enough to meet this limit. For top marks the move needs to be completed in less than 45 seconds. At the calculated linear speed, it would take 2.313 seconds for the mass to be lifted up 10cm from Point A. It would also take 1.156 seconds for it to be lowered down 5cm onto Point B. This comes to a total of 3.469 seconds of lifting and lowering time for the complete move. This leaves 41.531 seconds to complete the move which is a sufficient amount of time.

3.4.2 Is it slow enough? While it is important to move the mass fast enough, having it move too fast may introduce unwanted dynamic loading on the structure. Dynamic loading occurs when loads change in either size, position or direction. To prevent this from occurring in the truss, the load should not be lifted too quickly. This is directly linked with the radius of the drum, where we had to decide between a 1cm or 2cm radius. Calculations showed that the 2cm radius would results in lifting speeds of 7.954cm/s, which was determined to be too fast. Taking it down to a radius of 1cm resulted in the lifting speed being greatly reduced to 4.324cm/s, which has a major impact on making the dynamic loading much more insignificant, while only increasing the lifting time by a fraction of a second. It was determined that the 1cm radius was the most suitable.

3.5 Power Analysis The two main considerations for the electromechanical system are that the power drawn does not go over 10W, and that it must not exceed 24V or 3A. To determine if this motor is suitable a power analysis will be performed. For the lifting system, the no-load current of the motor is 0.25A and the stall current of the motor is 3.37A. 3.5.1

Operating Current

istall−i no load ∗τ motor +ino load τ stall ¿ 0.48197 A imotor=

¿

3.37 A−0.25 A ∗0.000728625 Nm+0.25 A 0.0098 Nm

The operating current for this motor while lifting 0.5kg is under the 3A limit.

3.5.2

Electrical Power

Pelec=V ∗imotor

¿ 3 V∗0.48197 A
...