FAW Armrest Assembly: The 4 Critical Components for a Safe and Secure Cab Entry

Welcome to this critical safety and ergonomic analysis of the FAW Armrest Assembly. This is the complete, 4-component-type, heavy-duty “assist handle” system for the cab of the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor. This is not a “comfort” armrest; it is a primary structural component. Its core “logic” is to provide a secure, load-bearing hand-hold, enabling a driver to safely maintain “3-point contact” when climbing into or out of the high cab-over-engine.

The FAW Armrest Assembly is an integral part of the vehicle’s safety and access “logic,” working in conjunction with the ‘Wing Panel Logic Assembly’ (Assembly 622) steps. This system is comprised of two mirror-image ‘Armrest Assemblies’ (Left: 5302115-D03, Right: 5302120-D03) and a robust 14-piece fastener kit. The “logic” of its design is to provide an unyielding anchor point capable of supporting the full body weight of a driver, in all weather conditions.

This in-depth guide is an essential resource for body shop technicians, collision specialists, and fleet safety managers. We will deconstruct the entire FAW Armrest Assembly into its 4 distinct Minimum Serviceable Unit (MSU) types. We will analyze the “structural core” logic of the main handles, their ergonomic and material design, and the critical, dual-type “anti-vibration” fastener system that secures them directly to the cab’s structural A-pillars.

Core 1: The “Safety & Ergonomic” Logic (MSUs 1 & 2) (The “Longer” Module)

The primary components of the FAW Armrest Assembly are the ‘Left armrest assy’ (5302115-D03) and ‘Right armrest assy’ (5302120-D03). These are the main structural MSUs. As “left” and “right” parts, they are mirror images, but their “logic” is identical: to provide a safe, ergonomic “assist handle” for cab ingress and egress.

1. The “3-Point Contact” Safety Logic:

This is the #1 “logic” of this assembly. Slips and falls from heavy equipment are a leading cause of driver injury. Occupational safety regulations mandate a “3-point contact” rule, meaning the driver must always have two hands and one foot, or two feet and one hand, in contact with the vehicle when climbing or descending.

The FAW Armrest Assembly is the “hand” part of this equation. It is precisely positioned on the cab’s A-pillar to work in concert with the ‘3-stage step panel’ (Assembly 622). Its “logic” is to be at the perfect height to allow a driver to pull their entire body weight up, transitioning their grip from the lower handle to the upper handle as they ascend into the cab.

2. The “Ergonomic” Logic (Design):

The design of the FAW Armrest Assembly is not arbitrary. Its “logic” is based on ergonomics.

• Diameter & Shape: The handle is molded to a specific diameter that allows for a full, powerful “power grip” even when the driver is wearing thick, insulated, or wet work gloves.
• Texture & Material: The surface is a non-slip, “pebbled” or “stippled” texture. This “logic” provides maximum friction, even when the handle is covered in rain, snow, or diesel fuel.
• Angle & Clearance: The handle is mounted at a comfortable angle and provides several inches of “clearance” from the cab’s body, ensuring the driver’s knuckles do not get scraped or pinched.

Core 2: The “Structural Core” Material Logic

A common misconception is that the FAW Armrest Assembly is just a piece of plastic. This is incorrect. The “logic” of its construction is a “steel-in-polymer” design, similar to a modern steering wheel.

The Steel “Armature”: The true “logic” of this MSU is a hidden internal structure. Inside the polymer molding is a heavy-duty, fabricated steel “armature” or “core.” This steel core provides the actual structural strength. This core has the mounting plates with the 7 bolt holes, and it is this steel that is fastened directly to the cab’s structural ‘Welded Cab Assembly’ (Assembly 617) A-pillar.

The Polymer “Over-Mold”: The plastic that the driver touches is an “over-mold.” This “logic” is what provides all the ergonomic and comfort benefits:

• Thermal Break: The polymer is a “thermal break.” It prevents the driver from grabbing bare, freezing-cold steel in a -30°C winter or a painfully hot, sun-baked steel bar in a +50°C summer.
• Corrosion Proofing: The over-mold provides a 100% waterproof and airtight seal *around* the steel core, making the FAW Armrest Assembly completely immune to rust.
• Vibration Damping: The softer polymer helps to damp high-frequency “buzz” from the engine, making it more comfortable to hold.

As MSUs, these are high-wear items. They are replaced when the outer polymer is cracked (exposing the steel core), or if the unit is bent or broken in a collision.

Core 3: The “Anti-Vibration” Fastener Logic (MSUs 3 & 4)

This final group of MSUs is the “logic” that ensures the FAW Armrest Assembly stays “rock solid” for the life of the truck. This system is subjected to the constant “pulling” force of drivers *and* the constant, high-frequency “buzz” of the diesel engine.

The “fastener logic” is to use 14 total “Combination Bolts,” split into two different grip-lengths.

MSU 3: ‘Combination bolt’ (CQ1460816F6) – Qty 6

MSU 4: ‘Combination bolt’ (CQ1460825F6) – Qty 8

The “logic” of 14 total bolts means each armrest (Left and Right) is secured by **seven** bolts. This is a massively over-engineered, high-strength connection, proving this is a structural, load-bearing component.

The “Combination” (组合) logic is the most critical feature. These are not simple bolts. They have a *captive, pre-attached lock washer* (e.g., a serrated or spring washer) under the head. This “logic” is 100% about anti-vibration.

The lock washer bites into the steel armature of the handle and the steel A-pillar of the cab, creating constant tension. This makes it physically impossible for the bolt to back out or loosen from vibration. This is what prevents the FAW Armrest Assembly from developing a “wiggle” or “rattle” over time, which would lead to a catastrophic shear failure. The two different part numbers (CQ1460816F6 and CQ1460825F6) simply refer to different lengths, as the bolts must pass through different thicknesses of the A-pillar’s reinforced structure.

FAW Armrest Assembly Parts List & Specifications

The following table provides the complete, detailed breakdown of all 4 component types identified in the FAW Armrest Assembly system for the FAW CA4251P66K24T1A3E5 tractor.

Specifications

The specifications for the FAW Armrest Assembly are defined by its function as a safety-critical, structural grab handle for cab access.