Hypoid gear require special lubricant because, multiple choice question is given below:

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Explanation

Hypoid gears require special lubricants because of their unique design and operating conditions. Hypoid gears are a specific type of spiral bevel gears that have offset axes, resulting in a sliding action between the gear teeth during operation. This design characteristic introduces additional challenges and requirements for the lubrication system. Hereunder are some reasons why special lubricants are required for hypoid gears:

1. Extreme Pressure (EP) Performance: Hypoid gears operate under high loads and significant sliding contact, resulting in high pressure and shear forces. Special lubricants formulated with extreme pressure additives are needed to withstand these conditions and prevent metal-to-metal contact, which can lead to wear, pitting, and failure.
2. Anti-Wear Properties: The sliding action of hypoid gears makes them more prone to wear compared to other types of gears. Lubricants for hypoid gears are formulated with anti-wear additives that create a protective film on the gear surfaces, reducing friction and minimizing wear.
3. Surface Compatibility: Hypoid gears typically have different materials for the pinion and ring gear. For example, the pinion may be made of steel, while the ring gear is often made of softer materials like bronze or aluminum. Special lubricants are designed to provide effective lubrication and minimize wear between dissimilar materials, ensuring compatibility and longevity.
4. Thermal Stability: Hypoid gears generate significant heat due to the sliding action and high loads. Special lubricants are formulated to have excellent thermal stability, allowing them to maintain their lubricating properties and resist degradation at elevated temperatures.
5. Foam Control: Gears operating at high speeds can entrain air and generate foam in the lubricant. Foam can lead to lubrication issues, reduced efficiency, and inadequate film thickness. Special lubricants for hypoid gears contain anti-foaming additives to minimize foam formation and ensure proper lubrication.
6. Seal Compatibility: Hypoid gears are often used in enclosed gearboxes where seals are necessary to retain the lubricant. Special lubricants are formulated to be compatible with common seal materials, preventing leakage and maintaining a proper lubricant seal.

It is important to note that selecting the appropriate lubricant for hypoid gears depends on factors such as the gear design, operating conditions, manufacturer recommendations, and industry standards. Consulting the gear manufacturer or lubricant supplier is recommended to ensure the correct lubricant is chosen for optimal performance, longevity, and gear protection.