Basic Parameters and Designation of Roller Chains

1. Standard & Series Roller chains are standardized under GB/T 1243, with two main series: Series A: For heavy-duty, high-speed, and critical drives (widely used globally). Series B: For general light-to-medium duty drives. 2. Basic Parameters (1) Pitch (P) Distance between adjacent pin centers. Calculation: Chain number × 25.4 ÷ 16 (mm). Larger pitch = higher load capacity, but more vibration, shock, and noise. Selection rules: Use a small pitch for compact, long‑life drives. Use small‑pitch multistrand for high speed and high power. Use a large pitch for low speed, heavy load, and large center distance. (2) Sprocket Teeth (z₁, z₂) Small sprocket: v = 0.6–3 m/s → z₁ ≥ 17 v = 3–8 m/s → z₁ ≥ 21 v > 8 m/s → z₁ ≥ 25 High speed + shock → z₁ ≥ 25 (hardened tooth face) Large sprocket: z₂ = i × z₁ (max ≤ 114 teeth). Preferred odd teeth: 17, 19, 21, 23, 25, 38, 57, 76, 95. (3) Transmission Ratio (i) Normally i ≤ 6; recommended 2–3. 5. Up to 10 for very low speed (v < 2 m/s) and smooth load. (4) Center Distance Too small: small wrap angle, fast wear, short life. Too large: slack side flutters, unstable running. Design should be adjustable (adjustment range ≈ 2×pitch). (5) Strand Pitch (pt) Single, double, or multi‑strand. Load capacity is nearly proportional to the number of strands. (6) Number of Links (Lp) Even numbers are preferred to avoid offset links. (7) Chain Length (L) Formula: L = p × Lp ÷ 1000 (meters). 3. Chain Designation (Marking) Format: Chain number – number of strands × number of links Standard No. Example: Roller chain 08A–1×88 GB/T 1243 08A: chain size 1: single strand 88: number of links GB/T 1243: standard