9.1 What is the main purpose of maintenance? 9.2 Briefly explain how basic preventative maintenance should be performed on the following systems: 9.2.1 Chain drive systems: 9.2.2 Belt drive systems: 9.3 State TWO properties of EACH of the following nylon products: 9.3.1 Polyethylene (PET): 9.3.2 Polypropylene (PP): 9.3.3 Polystyrene (PS): 9.4 State THREE factors that influence the coefficient of friction - NSC Mechanical Technology Fitting and Machining - Question 9 - 2022 - Paper 1

To perform basic preventative maintenance on chain drive systems, one should:

• Clean uncovered drives regularly to prevent debris buildup.
• Check the wear on the sprocket teeth and link plate to ensure proper functioning.
• Apply appropriate lubricants to reduce friction and wear.
• Inspect the functioning of tensioning devices to maintain chain tension.
• Inspect chains for elongation, replacing them as needed.

For belt drive systems, preventative maintenance should include:

• Checking the wear and tear on the belt to identify any damage.
• Verifying belt alignment to ensure smooth operation.
• Checking the tension setting of the belt to maintain optimal performance.
• Inspecting tensioning devices to ensure they function correctly.

Polyethylene (PET) has the following properties:

• Stiff, which helps maintain shape under load.
• Strong, providing good structural integrity even in thin sections.

Polypropylene (PP) has these properties:

• Good fatigue resistance, allowing it to withstand repeated stress without failure.
• Heat resistance, making it suitable for a variety of applications that involve temperature changes.

Polystyrene (PS) possesses the following properties:

• Good insulation properties, beneficial for thermal insulation applications.
• Water resistant, making it suitable for use in moist environments.

The coefficient of friction is influenced by:

• Surface roughness/texture, which affects the interlocking between surfaces.
• Temperature, as warmer conditions may alter the material properties.
• Type of lubricant used, which can either increase or reduce friction.

Thermo-hardened composites undergo a chemical change during moulding, which makes them rigid and unable to be re-heated to revert to a soft state. Once cured, these materials maintain their shape and cannot be reshaped without compromising their integrity.

Types of belts used in belt drive systems include:

• V-belt
• Wedge belt / Cog belt
• Flat belt