Welcome to Engineering Design!

In this chapter, we are going to look at the "invisible" things that engineers have to think about when they create a product. It’s not just about making something that looks cool! An engineer has to ask: Where does the power come from? How long will it last? How do we fix it when it breaks? and Can we even get the materials we need?

Don't worry if this seems like a lot to take in. We will break it down piece by piece so you can see exactly how these factors shape the world around us.

1. Energy Production Methods

Every engineered solution usually needs power. Engineers must choose the best way to get that energy while thinking about the environmental impact and cost.

Renewable Energy (The "Green" Methods)

Wind: Uses large turbines to turn wind into electricity.
Benefit: No pollution during use.
Drawback: It’s not always windy (unreliable) and some people think turbines look messy.

Solar: Uses panels to catch sunlight.
Benefit: Great for remote places; very low maintenance.
Drawback: Doesn't work at night and panels can be expensive to make.

Tidal: Uses the movement of the ocean tides.
Benefit: Very predictable (we always know when the tide comes in).
Drawback: Can damage local sea life and is expensive to build in the salty ocean.

Biomass: Burning natural things like wood or plant waste.
Benefit: Reduces waste going to landfills.
Drawback: Burning it still releases some CO2 into the atmosphere.

Non-Renewable and Nuclear Energy

Fossil Fuels: Burning coal, oil, or gas.
Benefit: Cheap and provides a lot of energy quickly.
Drawback: Major cause of global warming and will eventually run out.

Nuclear: Splitting atoms to create heat.
Benefit: Produces massive amounts of energy without CO2 emissions.
Drawback: Produces radioactive waste that is very hard to get rid of safely.

Quick Review: The Energy Choice

Engineers have to balance reliability (does it work all the time?) against sustainability (is it good for the planet?).

Key Takeaway: Choosing an energy source depends on the location of the product and its impact on the environment.

2. Engineered Lifespans

Have you ever noticed that some things are built to last forever, while others seem to break just after the warranty ends? This is a design choice!

Planned Obsolescence: This is when a product is designed to become "out of date" or break after a certain time.
Example: A smartphone that slows down after three years so you buy the new model.

Sealed Parts: Some products are "sealed for life." This means the user cannot open them to fix them. While this keeps the product safe and compact, it means if one tiny bit breaks, the whole thing usually has to be recycled or thrown away.

Maintenance Requirements: Some products are designed to be "heavy duty" and easy to fix. An engineer must decide if the user will be able to perform maintenance (fixing/cleaning) or if the product is "disposable."

Did you know? Some lightbulbs from 100 years ago are still burning today because they weren't designed with planned obsolescence in mind!

Key Takeaway: Engineers decide how long a product should last based on cost, technology changes, and user needs.

3. Keeping Things Running: Maintenance

Maintenance is like giving a car a "check-up." Engineers design products with maintenance in mind for two main reasons:
1. Ensure safety: To make sure the product doesn't become dangerous.
2. Enable efficiency: To make sure it uses as little energy as possible.

Types of Maintenance Work

To keep a machine happy, engineers plan for:

  • Lubrication: Adding oil or grease to moving parts to stop friction. (Think of oiling a squeaky bike chain!)
  • Avoiding Corrosion: Using coatings or paints to stop metal from rusting.
  • Compensating for Wear: Designing parts that can be tightened or replaced as they rub together and get smaller over time.
  • End of Life (EOL) Disposal: Planning for how the product will be taken apart and recycled at the end of its life.

Using Statistics

Engineers use statistics to predict when a part might break. If they know a part usually lasts 1,000 hours, they will schedule a service at 900 hours to be safe.
\( \text{Expected Lifetime} = \text{Reliability Data} \times \text{Usage Time} \)

Memory Aid: The L.A.C.E. Trick

To remember maintenance types, think of L.A.C.E.:
Lubrication
Avoiding Corrosion
Compensating for wear
End of Life disposal

Key Takeaway: Maintenance keeps products safe and efficient, and it must be planned from the very start of the design.

4. Material Availability and User Requirements

Sometimes, the "perfect" design is impossible because of availability or cost.

Availability and Forms

Materials usually come in standard stock sizes (like a 2-meter long wooden plank). If a designer wants a 2.1-meter plank, it becomes much more expensive because it is "non-standard."
Analogy: It’s like buying clothes. Buying a "Medium" shirt is cheap, but getting one custom-made to your exact measurements costs a lot more!

User Requirements

What the customer wants changes the design. If a user needs something high strength but low weight (like a racing bike or a prosthetic limb), the engineer must choose specialist materials like:
- Titanium
- Carbon Fibre

These materials are amazing, but they require specialist manufacturing processes, which makes the final solution more expensive.

Common Mistake to Avoid: Don't assume the most expensive material is always the best. A good engineer chooses the material that fits the budget and the task.

Key Takeaway: Designing is a balance. Engineers must match what the user wants with what materials are actually available and affordable.

Quick Review Box:
- Energy: Balance environment vs. reliability.
- Lifespan: Decide between "built to last" or "planned obsolescence."
- Maintenance: Use L.A.C.E. to keep things safe.
- Materials: Use standard sizes to save money unless the user needs specialist performance.