Self-Lubricated Bronze Bearings (CuZn25Al5 with Graphite + Additive)Material OverviewSelf-lubricated bronze bearings made from CuZn25Al5 (high-strength brass, also known as C86300 in ASTM standards) are engineered for heavy loads at low sliding speeds. The graphite with additives embedded in the bronze matrix acts as a solid lubricant, forming a low-friction film during operation. This eliminates the need for external lubrication, making these bearings ideal for applications like rocker arms where maintenance is challenging or oil contamination is a concern.

• Base Material: CuZn25Al5 (Copper: ~65%, Zinc: ~25%, Aluminum: ~5%, with trace elements like manganese for strength).
  • Properties: High tensile strength (~750 MPa), excellent corrosion resistance, and good thermal conductivity.
  • Suitable for loads up to 120 N/mm² (static) and 50 N/mm² (dynamic).
• Lubricant: Graphite plugs (typically 20-30% surface coverage) with additives (e.g., PTFE or MoS₂) to enhance lubricity and wear resistance.
  • Coefficient of friction: ~0.05-0.15 (dry).
  • Operating temperature: -40°C to +300°C (depending on additive).

Available Forms

• Cylindrical Bushings: Standard for rocker arm pivots; IDs range from 6mm to 100mm (e.g., 20mm ID for automotive rockers).
• Flanged Bushings: For axial load support; flange thickness typically 2-5mm.
• Washers: For thrust applications; common sizes 10-50mm diameter.
• Strips: For custom machining or linear sliding surfaces.
• Custom Parts: Tailored to customer drawings (e.g., non-standard bores for specific rocker arm designs).

Applications in Rocker Arms

• Automotive: Used in valve train systems (e.g., OHV or OHC engines) to handle high valve spring pressures (200-800 lbs) at low oscillation speeds (0.1-1 m/s).
  • Example: Replaces needle bearings in high-mileage engines (e.g., GM LS or Chrysler 3.6L V6) to prevent spillage and wear.
• Industrial: Lever arms, robotic joints, or presses in dusty or clean-room environments.
• Advantages:
  • No Maintenance: Eliminates oil/grease, reducing downtime.
  • High Load Capacity: Supports heavy loads without deformation.
  • Durability: Lifespan of 10,000+ hours in low-speed, high-load conditions.
  • Environmentally Friendly: No oil leakage; suitable for eco-sensitive applications.

Technical Specifications

• Load Capacity: Static: ≤120 N/mm²; Dynamic: ≤50 N/mm².
• Sliding Speed: Optimal at <0.5 m/s (low-speed oscillations typical in rocker arms).
• Friction Coefficient: 0.05-0.15 (dry); lower with additives like PTFE.
• Temperature Range: -40°C to +300°C (graphite stable; additives may limit upper range).
• Standards: Conforms to DIN 1850/ISO 3547 for plain bearings.

Installation for Rocker Arms

• Fit: Press-fit into rocker arm bore (H7 tolerance recommended for housing, h8 for shaft).
• Alignment: Ensure shaft misalignment <0.05mm to avoid edge loading.
• No Oil Holes: Graphite plugs provide lubrication; oil/grease is unnecessary and may attract contaminants.
• Sizing Example: For a rocker arm with a 20mm shaft and 600 lbs valve spring load:
  • Select a 20mm ID x 24mm OD x 15mm length bushing.
  • Verify load: 600 lbs ≈ 2.7 kN; bearing area (20mm x 15mm) supports ~100 N/mm², within limits

• VIIPLUS: Offers CuZn25Al5 oilless bushings with graphite plugs; custom sizes available.

Comparison to Alternatives

If you have a specific rocker arm setup (e.g., engine type, load, or dimensions), I can refine sizing or supplier recommendations. Let me know!