Level 2 Report
29 / 2 / 2024
Level 2 Report
Mechanical Assembly and Simulation:
This task consisted of a clear understanding of different features of Fusion360 like bodies and components. It was built upon the basics of sketching and use of various features like extrude, cut, hollow, loft etc.
The design of the individual components was challenging as certain dimensions were missing and it was a learning curve where I learnt about features like fillet and punch.
The assembly part of the project was complicated at first but after several trial-and-error attempts I was able to piece it together.
Computational Fluid Dynamics
This was the most interesting task and was visually very exciting. I learnt to use Autodesk CFD environment for various fluid related simulations. The software enables us to choose the simulating material in detail may it be compressible or incompressible, consideration of heat transfer etc.
I made used of a plugin know as DAT to Spline to execute this task. From an online aerofoil co-ordinates index website, I downloaded the co-ordinates for a NACA 63-412 aerofoil. By changing the scale, camber and offset value of the profile I created a model of a wing in Fusion360 and then imported it into CFD in step format.
I created a contraption around the model and assigned material data for the model, which in this case is aluminium. The fluid used here is air. Velocity of wind is 25 m/s. The simulation was run for 50 iterations to plot a graph for various parameters and to calculate Drag co-efficient and lift produced by the aerofoil.
At 25 m/s the lift produced is Fz=Lift=-0.0424 newtons and Drag produced is Fy=Drag=0.107 newtons.
Topology Optimisation
It seemed easier at first but turned out to be a bit confusing. I went through the concept of topology optimization from various videos on YouTube and articles on the Autodesk official website.
It works on the basis of cloud-computing to generate various iterations of design while satisfying all the constraints and generates the most suitable option. I generated a wheel Which can withstand a uniform pressure of 10 Mpa. It generated a mesh which I used as a template to trace it out and create the final wheel. The geometry of the wheel isn’t perfect and I need to tinker around more to be thorough with environment.
Generative Design
It was a very challenging but interesting tasks. I created a rover type design to encounter various forms of harsh terrains. I used generative design to conduct study about minimizing mass and maximizing the structural rigidity. I used a study to see how using different materials we can achieve different properties. Here the factor of safety of all structures has been set to 2.0. All the joints can easily handle upto 80 Newtons of load. I learnt about various terms in generative design like Preserve Geometry, Obstacle Geometry and Basic shape.It was a challenging and a very useful task.
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Sourcing & Materials Selection
An electric Bicycle has to be designed using several factors in mind like durability, size etc.
Material Selection:
Frame: Primary Material: 6061-T6 Aluminium Alloy: This high-strength, lightweight alloy offers an excellent balance of stiffness, fatigue resistance, and corrosion resistance, crucial for frame integrity and handling. Joining Technology: TIG Welding: This precision welding technique minimizes heat impact, prevents material embrittlement, and ensures robust frame welds. Carbon fibre can be used to build a lightweight frame but would prove extremely costly and would be a hassle to manufacture.
Alloy Wheels: Material: Aluminium Alloy 7075: This high-strength, low-weight alloy provides stiffness for efficient power transfer and rotational inertia, while its durability withstands rough terrain and impacts.
Spokes: Double-butted Stainless Steel: Lighter at the ends and thicker at the hub and rim, these spokes optimize weight distribution for spoke tension and fatigue resistance.
Brake Callipers: Material: Forged Aluminum: Offers robust stopping power without excessive weight. Hydraulic Disc Brakes: High-performance braking system with excellent modulation and weather resistance.
Bearings: Sealed Cartridge Bearings: High-quality sealed bearings minimize friction and maintenance needs, ensuring smooth operation and longevity in varied environments. Brand to be used Schaeffler.
Gearing System: A wide-range cassette/derailleur combination allows efficient pedalling at varying speeds and inclines, catering to diverse terrains and rider preferences.
Suspension System: An adjustable fork suspension provides comfort and control on uneven surfaces, enhancing adaptability.
Tire Selection: Puncture-resistant tires offer durability and minimize downtime. Different tread patterns can be chosen for specific environments (e.g., knobby for off-road, slick for urban commutes).
Design: Generative design can be used to reduce the mass of cycle while keeping the strength of the cycle intact.
Fasteners: Use of titanium bolts and nuts with nylon washers can ensure durability and can withstand a wide range of vibrations.
Design
Motor specifications: Motor Specifications: For an urban electric bicycle with a target weight of 45 kg and a payload capacity of 100 kgType: Brushless DC (BLDC) motor Power: 500-750W (continuous rating) Peak Power: 1000-1500W Voltage: 48V Motor Weight: 3-5 kg (depending on the specific motor model) Winding Type: Delta or Wye winding (both are common for BLDC motors) Reasons for selection: •\tBLDC motors are efficient, lightweight, and provide good power density, making them ideal for electric bicycles. •\t500-750W continuous power is sufficient for urban commuting with a rider weight up to 100 kg, while the higher peak power allows for good acceleration and hill-climbing ability. •\t48V systems are common in electric bicycles, providing a good balance between power and battery size/weight. •\tDelta or Wye windings are standard for BLDC motors and offer reliable performance.
Battery specifications Li-ion batteries 24 Volts 15AH.It' s a fully ready made battery back with plug and play.It is detachable from the main body by a simple mechanism and can be used to recharge at home.At 2.5 kg it' s light and compact.
Dimensioning The bicycle has to be compact and lightweight to enable easy carrying around and extended range of the bicycle.It' s designed to be used over short distances and is not comfortable over long commutes.
Gear system Bikes Brisbane Electronic shifting is the next wave in gearing systems b largely focused on the road bike market. Except for Roh with its Speed Hub is the best gearing system on offer. It is a highly sophisticated auto shift system that boasts the largest range of gears (14 total) possible on an ebike and a 526% gear ratio. It also offers the fastest gear shifting on the market
Total Weight of the Bike Total vehicle weight=Frame(6kg)+tyre(0.4kg)+alloy(2.5*2=5kg)+all fastners(1kg max)+seat(0.4kg)+battery(2.5kg)+carrier&mudguard(0.8kg)+gear and sprocket system(3 kg)=19.1 kg with errors 20 kg
Battery Management System I have attached the below mentioned site for reference.The BMS system should not weigh more than 2.5 kg
Tyre Specifications Refer the images attached
Electronics Task:
Creating a Voltage Multiplier:
I learned what a capacitor does. A capacitor acts like a dam holding excess current and voltage which it can discharge at once. To multiply voltage here we use capacitors in a pattern so that they provide the effect of a series circuit delivering around 25 voltage of input. The voltage is lost in diodes which prevent the backflow of the current. I took help from IOT coordinator Akanksh to understand the circuit and obtain resources for this particular task.
Creating a Circuit that Provides Short-circuit Protection:
This was a task to be done offline. I used a relay available in the lab and soldered the connections. I couldn’t find a charged battery and an LED strip. So with the help of my batchmate Chirag, I simulated the entire circuit on TinkerCad.
Participation
Design of a Meccanum wheeled robot
M kanks uvraj and Nalin participated at Christ University.We designed a meccanum wheeled robot.The assembly of the wheel and chassis was extremely challenging. After assembly of the chassis the controls of the robot via ESP32 was another ballgame altogether.We spent a lot of time till late nights at MARVEL working on this project.It was a very fun experience and I got to apply my knowledge gained through the D&P syllabus.