Recent Question/Assignment

Advanced Mechanical Design
Major Assignment
Mining Drill Head Gearbox Design
Due Date: 5:00pm 18th April 2019 (Design Report and load calculations)
Due Date: 9:00am 27th May 2019 (Overall report)

The overall drill string consists of numerous drill rods, a drill hammer and drill bit. Each drill rod is 6m long and inserted into drill string once the gearbox and hydraulic motor have traversed down the mast, allowing the hole to drilled a further 6m and the process is repeated until the desired drill depth Is achieved. The mast drives the drill string into the ground with a pull down (red arrow) load of 15kN. To assist with cutting, a hammer is located above the drill bit and increases the drill bit load. The hammer consists of a 15kg mass that oscillates in a sinusoidal pattern with a frequency of 15Hz and an amplitude of 100mm. The drill bit (which has equivalent diameter to the drill rods) consists of small cutting teeth that are situated on the drill bit perimeter and has an average coefficient of friction of 0.5 with the ground being cut.
The 6m long drill rods are tubular steel with an outside diameter of 120mm and an inside diameter of 110mm and it is expected that the drill rig can drill a hole up to 500m deep. Whilst drilling, the walls of the hole drags against the side of the rotating drill string, providing a 25N friction force per unit area (m2) of drill string surface. It is assumed that the hammer and drill bit are negligible weight, however their combined length is 2m. To improve drill productivity, the drill bit speed should be as high as possible.
Hydraulic motor (TB0390) and gearbox are attached to one another, where the gearbox is then mounted to the mast (as illustrated in Figure 1). As a result, the gearbox and hydraulic motor should be designed as one single device that is then attached to the mast, where the gearbox is a structural member that ensures attachment of both the drill string and hydraulic motor to the mast. No details of the mast are provided, hence you can specific where you would like to mount the gearbox to the mast with provisions to do so and sized attachment fasteners accordingly. Rotating motion between components should be isolated with rolling element bearings that are adequately sized. There is no requirement for coaxial alignment between the hydraulic motor and drill string.
The drill rig has a hydraulic power supply that offers a maximum of 100 Bar oil pressure and a maximum of 57 L/min oil flow rate. Along with the gearbox design, please provide any operating conditions (such as hydraulic performance) in order for the operator to maximise productivity. The drill rig is designed to operate as reliably as possible to avoid any downtime, however, this must be within reason to avoid unnecessarily expensive components and the entire gearbox should not need servicing for a minimum of 10,000 hours.
The assignment deliverables for the design are as follows:
1. A complete set of design documents for the assembly:
• A design report that details (15%):
? Product design specification
? Manufacturing details (including processes, off-the-shelf components, required treatments, etc.)
• An analysis report that covers (45%):
? Load calculations (prior to further analysis)
? Stress and fatigue calculations
? Failure analysis calculations of component(s)/assembly where applicable ? Finite Element Analysis of structural components
• A complete set of manufacturing drawings – fully dimensioned of all parts ready for manufacture (Note: this excludes the motor, gear tooth profiles and bearings) (10%)
• SolidWorks 3D model (or equivalent CAD model that can be opened within SolidWorks) of the complete actuator assembly and components. Printed (hardcopy) images of all the components in your design are required along with electronic files of the parts and assemblies (15%)
2. Presentation: A 5 minute presentation of your group’s design to the class during the final lecture (5%).
3. Teamwork: Cooperate as an effective team with suitable load sharing (5%)
4. Report: All aspects for a quality report, such as grammar, referencing, presentation, etc. (5%)
Note: The design report and load calculations are due 9am 19 April 2019. The overall report is then due 9am 27 May 2019. The written component (excl. drawings) of the design report should not exceed 10 pages, any content beyond 10 pages will not be considered in the mark. The analysis report should not exceed 30 pages, any content beyond 30 pages will not be considered in the mark.
Notes and Assumptions:
I. The gearbox should be serviceable
II. The gearbox should include oil fill and drain locations
III. This gearbox should be designed for a mining application
IV. The final design should be a complete ready-for-manufacture design

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