Mechanical Design Data and Machine-Element Reference: Sprocket Modifications and Specials

Sprocket Modifications and Specials

• Standard sprockets are available for simple, duplex, and triplex configurations up to 2.00″ pitch
• Manufacturers also produce sprockets with intermediate numbers of teeth to suit single or multi-strand chains
• Special design sprockets can be manufactured to specific requirements using normal or special materials
• Sprockets to suit chain manufactured to imperial standards are available and are made to order

Rebore, Keyway, and Setscrew Modification

• Catalogued stock sprockets are supplied either taper bored or pilot bored (larger unfinished bore allowing machining to tolerance)
• Pilot bore allows standard tolerances to be machined; a bore to closer tolerance can also be supplied on request
• Keyways to imperial or metric specifications, and setscrews can be machined
• A rebore, keyway, and setscrew modification service is available from manufacturers

Couplings

Preamble

• Couplings connect the output shaft of a prime mover (motor, engine) to the input shaft of a driven machine (gearbox, pump, conveyor)
• Multiple types of coupling exist; the main variation is in cost, misalignment tolerance, and power capacity
• Six common coupling types are covered here: Spiderflex, Pinflex, Tyreflex, Discflex, Chainflex, and Rigid
• Additional specialised types include: high-misalignment gear types, brake drum gear types, disc brake types, shear pin gear types, buffer shear pin types, telescopic types, and hydraulic couplings
• Power ratings for flexible couplings are based on a reference speed of 100 rev/min
• To select a coupling, multiply the actual power at the actual operating speed by the factor 100/N (where N is operating speed in rpm)

Misalignment Types

• Rigid couplings are NOT designed to accept misalignment or movement between shafts — only suitable where no misalignment or movement will occur
• Flexible couplings are designed to meet four misalignment conditions and should always be used wherever a prime mover is directly coupled to a gearbox or machine shaft

• Flexible couplings are not designed to absorb excessive misalignment caused by careless assembly
• Shafts should still be aligned as accurately as possible in accordance with good engineering practice

Selection Method — Rigid Couplings

• Rigid couplings are rated to transmit the same torque and power as a mild steel shaft of the same diameter
• Misalignment is not a consideration in their selection
• Selection involves:
  1. Matching the coupling to the shaft size involved
  2. Ensuring the speed is within the maximum speed listed
• Rigid couplings are available with or without taper lock bushes

Selection Method — Flexible Couplings (11-Step Process)

Service Factors

Table 2 — Service Factor (f_D)

Table 3 — Start Factor (f_S)

Note: For applications with excessive vibration, contact the manufacturer's technical department.

Coupling Types Comparison

Coupling Type Details

Spiderflex Coupling

• Available in B type (plain bore) and F/H type (taper bore)
• Flexible element: Nitrile rubber — temperature range −40 to +100°C, oil resistant, low absorption of liquids, partially resistant to chemicals
• Shore hardness: A88
• Permissible misalignment varies with size (e.g., 0.3–0.5 mm radial, 0.5°–2.5° angular)
• End float range: +0.2 to +1.7 mm depending on coupling size
• Weight range: 1.0 to 63 kg

Pinflex Coupling

• Pin-based flexible coupling with varying pin counts (3 to 16 pins depending on size)
• Maximum angular misalignment: 0.25°
• Maximum axial misalignment: 0.13 mm
• Power range: 2.03 kW (3-pin, size 1/3) up to 258.80 kW (16-pin, size 8/16) at 100 RPM
• Steel half-bodies as standard
• Available with bore range from unbored up to very large bores depending on size

Tyreflex Coupling

• Provides the highest angular misalignment tolerance of all common flexible couplings (up to 4°)
• Also provides the highest radial misalignment tolerance (up to 1.6 mm)
• Best choice when significant misalignment must be accommodated

Discflex Coupling

• Moderate misalignment capability (1° angular, 0.5 mm radial)
• Compact design

Chainflex Coupling

• Uses a duplex roller chain wrapped around sprocket-like hubs
• Provides 1° angular and 0.25 mm radial misalignment capacity
• Maximum speed: 3,500 RPM
• Power up to 90 kW at 100 RPM

Rigid Coupling

• Available in plain bored and taper bored versions
• Rated to transmit the same torque as a mild steel shaft of the same diameter
• No misalignment tolerance — shafts must be perfectly aligned
• Selection is based on matching shaft diameter and checking maximum speed

Rigid Coupling Data

Worked Example — Flexible Coupling Selection

Given:

• Power: 7.5 kW at 1440 rev/min from an electric motor
• Driven machine: chain conveyor (non-uniformly fed)
• Operating: 18 hours per day, 15 starts per hour
• Shaft diameter: 38 mm (both motor and gearbox)
• Maximum angular misalignment: 2°
• Maximum axial misalignment: 0.2 mm
• Taper bushes to be installed from coupling faces

Solution:

1. Data — as given

2. Load classification — Medium Impulsive (M) (chain conveyor, non-uniformly fed)

3. Service factor — f_D = 1.5 (electric motor, over 10 h/day, medium impulsive)

4. Start factor — f_S = 1.2 (1–30 starts/hour)

5. Selection power — Ps = 7.5 × 1.5 × 1.2 = 13.5 kW

6. Equivalent selection power — Pe = (13.5 × 100) / 1440 = 0.9375 kW

7. Suitable coupling types identified:

   • Spiderflex: RSCT110
   • Pinflex: PFT1/3
   • Tyreflex: TY60
   • Discflex: DT52N
   • Chainflex: C33M

8. Check allowable misalignment (2° angular, 0.2 mm radial):

9. Check max bore — Tyreflex TY60: max bore = 42 mm → ✅ (shaft is 38 mm)
10. Check max speed — Tyreflex TY60: 4,000 rev/min → ✅ (operating at 1,440 rev/min)
11. Final selection — Tyreflex TY60/77 (F type) with taper bush TB1610. From taper bush table, 38 mm is a standard shaft size. Therefore: TB1610/38

Chain Drive Selection Process

flowchart TD
    A[Start: Known Power, Speed, Machine Characteristics, Centre Distance] --> B[Step 1: Select Drive Ratio & Sprockets\nZ₁ ≥ 19 teeth minimum\ni = Z₂ / Z₁]
    B --> C[Step 2: Establish Application Factor f₁\nUsing driver/driven characteristics chart]
    C --> D[Step 3: Determine Tooth Factor f₂\nf₂ = 19 / Z₁]
    D --> E[Step 4: Calculate Selection Power\nSelection Power = Power × f₁ × f₂ kW]
    E --> F[Step 5: Select Chain Drive\nUse rating chart — smallest pitch simple chain\nIf exceeded → consider multiplex]
    F --> G[Step 6: Calculate Chain Length\nUsing chain length formula\nRound to even number of pitches]
    G --> H[Step 7: Calculate Exact Centre Distance\nUsing revised centre distance formula]
    H --> I[Step 8: Choose Lubrication Method\nBased on chain speed & power from rating charts]
    I --> J[Selection Complete]

Flexible Coupling Selection Process

flowchart TD
    A[Start: Known Power, Speed, Prime Mover Type, Load Type, Misalignment Requirements] --> B[Step 1: Set Out All Relevant Data]
    B --> C[Step 2: Classify Load\nSteady / Medium Impulsive / Highly Impulsive]
    C --> D[Step 3: Obtain Service Factor f_D]
    D --> E[Step 4: Obtain Start Factor f_S]
    E --> F[Step 5: Calculate Selection Power\nPs = P × f_D × f_S]
    F --> G[Step 6: Calculate Equivalent Selection Power\nPe = Ps × 100 / N]
    G --> H[Step 7: Select Smallest Suitable Coupling\nfrom coupling tables]
    H --> I{Step 8: Design Misalignment\n≤ Allowable Misalignment?}
    I -- Yes --> J{Step 9: Max Bore\n≥ Actual Shaft Size?}
    I -- No --> H
    J -- Yes --> K{Step 10: Max Coupling Speed\n≥ Operating Speed?}
    J -- No --> H
    K -- Yes --> L[Step 11: Detail Selection\nCatalogue No. + Taper Bush No.]
    K -- No --> H

Roller Chain Construction

flowchart LR
    subgraph Chain Link Assembly
        A[Outer Plates] --- B[Bearing Pin]
        B --- C[Bush]
        C --- D[Roller]
        D --- E[Inner Plates]
    end
    subgraph Function
        F[Pin + Bush = Journal Bearing\nCase-hardened for high pressures]
        G[Roller = Engages Sprocket Teeth\nReduces wear on sprocket]
        H[Link Plates = Constrain Bearings\nTransmit tensile load]
    end

Coupling Types — Misalignment Capability Map

quadrantChart
    title Coupling Misalignment Capability
    x-axis "Low Angular" --> "High Angular"
    y-axis "Low Radial" --> "High Radial"
    Rigid: [0.01, 0.01]
    Pinflex: [0.08, 0.08]
    Chainflex: [0.25, 0.15]
    Discflex: [0.25, 0.30]
    Spiderflex: [0.35, 0.25]
    Tyreflex: [0.95, 0.95]

Lubrication Method Selection

flowchart TD
    A[Determine Chain Speed & Power] --> B{Low Speed / Low Power?}
    B -- Yes --> C[Type 1: Manual\nBrush or oil can every 8 hours]
    B -- No --> D{Moderate Speed / Power?}
    D -- Yes --> E[Type 2: Drip Lubrication\nOil drips between link plate edges]
    D -- No --> F{Medium-High Speed / Power?}
    F -- Yes --> G[Type 3: Bath or Disc\nChain runs through oil sump\nor disc picks up oil]
    F -- No --> H[Type 4: Stream Lubrication\nContinuous pump supply\nProvides cooling & impact damping]

Key Terms Glossary

Quick Revision

• Chain pitch is the primary classification dimension for roller chains — measured pin centre to pin centre
• Minimum 19 teeth on the driver sprocket for standard applications; 25+ teeth for high speed or impulsive loads
• Maximum recommended sprocket teeth: 114; use odd teeth + even pitches combination
• Selection Power = Power × f₁ × f₂ — always calculate before consulting rating charts
• f₁ depends on driver AND driven machine characteristics; f₂ = 19/Z₁ (baseline 19-tooth)
• Round chain length to even number of pitches — odd pitches require cranked links (not recommended)
• Centre distance typically 30–50 pitches; recalculate exact centre distance after determining chain length
• Angle of lap ≥ 120° on the smaller sprocket for large ratio drives
• Grease is NOT recommended for chain lubrication — use mineral oil; 4 types of lubrication methods based on speed/power
• Chain temperatures above 100°C should be avoided; acceptable up to 250°C with dry lubricants
• Expected chain life: 15,000 hours / 8 million cycles under proper conditions
• Flexible couplings accommodate four types of misalignment: angular, axial, end float, torsional
• Rigid couplings tolerate ZERO misalignment — selection based on shaft size and speed only
• Coupling selection power: Pₑ = (P × f_D × f_S × 100) / N — normalised to 100 RPM
• Tyreflex has the highest misalignment tolerance (4° angular, 1.6 mm radial) among common flexible types
• Gearflex provides the highest power capacity (50,000+ kW at 100 RPM) for extreme applications
• Taper lock bushes are interchangeable between manufacturers and provide secure, re-usable shaft mounting
• Always verify: misalignment within limits, bore ≥ shaft size, max speed ≥ operating speed when selecting couplings
• 1 kW = 1.34 hp for power conversion

Belt Drives — Power Ratings & Pulleys

Overview

• This reference covers wedge belt power ratings, taper lock pulley specifications, and pulley groove dimensions for standard V-belt drive systems
• Power ratings are provided per belt for SPB and SPC wedge belt profiles, as well as CRE-type wedge belts (SPZ, SPA, SPB cross-sections)
• Taper lock pulley catalogues cover SPZ & Z, SPA & A, SPB & B, and SPC & C belt profiles with full dimensional data
• Pulley groove dimensions define the face width, groove geometry, and tolerances for each belt section
• All data supports the selection, specification, and verification of belt drive components in mechanical power transmission systems

Key Concepts

• Rated Power per Belt: The power (in kW) a single belt can transmit at a given speed ratio and pulley pitch diameter — used to determine the number of belts required
• Additional Power per Belt for Speed Ratio: An incremental power value added to the base rating when the speed ratio between driver and driven shafts exceeds 1.0
• Small Pulley Pitch Diameter (PCD): The effective diameter at which the belt contacts the pulley — determines belt speed and power capacity
• Belt Speed: The linear velocity of the belt (m/s), directly related to pulley diameter and shaft RPM — higher belt speeds generally increase power capacity up to a limit
• Taper Lock Pulley: A pulley that uses a split taper bush (cone-shaped locking sleeve) to clamp onto the shaft — enables tool-free installation and removal without keyway damage
• Bush Number: Identifies the specific taper lock bush size — defines bore range, shaft compatibility, and mounting bolt pattern
• Number of Grooves: The number of V-grooves machined into the pulley — must match or exceed the number of belts in the drive
• Pulley Type: Refers to the physical construction style (e.g., solid, spoked, plate) — different types suit different speed, weight, and balance requirements
• Groove Dimensions: Standardised measurements (groove angle, depth, pitch, top width) that ensure correct belt seating and power transmission

Power Ratings — SPB Wedge Belts

• Application: SPB belts are a narrow-section wedge belt profile used in medium-to-heavy industrial drives
• Power ratings are tabulated for small pulley pitch diameters ranging from 140 mm to 315 mm
• Shaft speeds (Rev/min of faster shaft) range from 100 to 3000 RPM
• Belt speeds indicated on the right-hand column range from 2.33 m/s up to 40 m/s (depending on RPM and pulley diameter)
• As pulley diameter increases at a given RPM, the rated power per belt increases due to higher belt speed and better wrap angle
• An additional power table is provided per belt for speed ratios — this accounts for the extra load capacity gained when the driven pulley is larger than the driver (speed ratio > 1.0)
• The additional power values are tabulated for speed ratios from 1.00 to 1.05 up to 3.39 and over
• Note: Only pulleys of a specified manufacture standard should be used where belt speed falls between 30 and 40 m/s — confirm selection and supply with the belt manufacturer

Power Ratings — SPC Wedge Belts

• Application: SPC belts are the largest standard narrow-section wedge belt profile — used for high-power industrial drives
• Power ratings cover small pulley pitch diameters from 224 mm to 560 mm
• Shaft speeds range from 100 to 2000 RPM
• Belt speeds range up to 40 m/s
• The same additional power per speed ratio table structure applies as for SPB belts
• SPC belts transmit significantly higher power per belt than SPB — e.g., at 1440 RPM with a 450 mm pulley, a single SPC belt can transmit approximately 52–54 kW
• The same belt speed caution (30–40 m/s range) applies for pulley manufacturer confirmation

Power Ratings — CRE Wedge Belts (SPZ, SPA, SPB)

• CRE-type belts are a category of classical/conventional wedge belts with smaller cross-sections
• Three sub-profiles are covered:

SPZ Profile

• Smallest CRE profile — suited for light-duty drives
• Power ratings for small pulley pitch diameters from 56 mm to 97 mm
• Shaft speeds from 100 to 2800 RPM
• Maximum rated power per belt is modest (typically under 5 kW per belt)

SPA Profile

• Mid-range CRE profile — suited for moderate-duty drives
• Power ratings for small pulley pitch diameters from 80 mm to 132 mm
• Shaft speeds from 100 to 2800 RPM
• Rated power per belt ranges from approximately 0.23 kW (small pulley, low speed) up to approximately 9 kW at higher speeds and larger pulleys

SPB Profile (CRE Type)

• Largest CRE profile covered — suited for medium-duty drives
• Power ratings for small pulley pitch diameters from 112 mm to 132 mm
• Shaft speeds from 100 to 2800 RPM
• Rated power per belt is higher than SPA — up to approximately 13 kW per belt at optimal conditions

Taper Lock Pulleys — SPZ & Z Belts

• Pulleys are catalogued with pitch diameters from 56 mm to 200 mm
• Number of grooves: 1 to 5 depending on pitch diameter
• Bush numbers include 1008, 1108, 1210, 1610, and 2012
• Maximum bore sizes range from 25 mm (metric) / 1 inch up to 50 mm (metric) / 2 inches
• Pulley types include solid (Type 1), plate (Type 2), and spoked variants (Types 6NR, 6, etc.)
• Key dimensional parameters provided:
  • F — Pulley face width (mm)
  • J — Hub projection or mounting face dimension (mm)
  • K — Keyway or clearance dimension (mm)
  • L — Bush length or overall hub depth (mm)
  • M — Bolt circle or mounting feature dimension (mm)
  • N — Additional mounting or clearance dimension (mm)
  • Outside Diameter (O) — Overall outer diameter of the pulley (mm)
• Type 6NR pulleys are non-preferred sizes and should be avoided in new designs where possible

Taper Lock Pulleys — SPA & A Belts

• Pulleys are catalogued with pitch diameters from 80 mm to 800 mm
• Number of grooves: 1 to 6 depending on pitch diameter
• Bush numbers include 1210, 1610, 2012, 2517, 3020, 3525, 4030, 4535
• Maximum bore sizes range from 32 mm / 1¼ inch up to 115 mm / 4½ inches
• Larger pulleys (diameter ≥ 400 mm) support up to 6 grooves and use larger bush sizes (3525, 4030, 4535)
• Type 6NR pulleys appear throughout — these use a specific non-standard retaining method
• Pulleys with an asterisk (*) designation are non-preferred sizes
• Outside diameters range from 86 mm (smallest single-groove) to 806 mm (largest multi-groove)

Taper Lock Pulleys — SPB & B Belts

• Pulleys are catalogued with pitch diameters from 112 mm to 1000 mm
• Number of grooves: 2 to 8 depending on pitch diameter
• Bush numbers include 2012, 2517, 3020, 3525, 4030, 4535
• Maximum bore sizes range from 50 mm / 2 inches up to 125 mm / 5 inches
• SPB pulleys begin at 2 grooves minimum (no single-groove SPB taper lock pulleys listed)
• For the largest pulleys (≥ 630 mm PCD), up to 8 grooves are available
• Outside diameters range from 119 mm to 1007 mm
• Pulley types progress from solid/plate at smaller sizes to spoked at larger sizes

Taper Lock Pulleys — SPC & C Belts

• Pulleys are catalogued with pitch diameters from 200 mm to 1250 mm
• Number of grooves: 3 to 8 depending on pitch diameter
• Bush numbers include 2517, 3020, 3525, 4535, 5040
• Maximum bore sizes range from 60 mm / 2½ inches up to 125 mm / 5 inches
• SPC pulleys begin at 3 grooves minimum — reflecting the higher power capacity of this belt section
• For the largest pulleys (≥ 800 mm PCD), up to 8 grooves are available
• Outside diameters range from 210 mm to 1260 mm
• All pulleys use Type 7 construction (spoked) at larger sizes for weight reduction

Pulley Groove Dimensions

• Groove dimensions are standardised to ensure correct belt fit, seating depth, and power transmission
• Dimensions vary by belt section and pulley PCD range (single groove vs. dual groove)

Pulley Groove Dimension Standards

Note: The e* dimension tolerance is measured between any two grooves. All dimensions in millimetres.

Belt Profile Comparison — Power Capacity Range

Taper Lock Bush Size Summary

Minimum Groove Count in the supplied reference (Taper Lock Pulleys)

Belt Profile Selection Flowchart

flowchart TD
    A[Determine Required Power per Belt] --> B{Power Level?}
    B -->|< 5 kW| C[SPZ Profile]
    B -->|5–13 kW| D{Application Type?}
    B -->|13–31 kW| F[SPB Narrow Wedge]
    B -->|> 31 kW| G[SPC Narrow Wedge]
    D -->|Light/Moderate Duty| D1[SPA Profile]
    D -->|Medium Duty| D2[SPB CRE Profile]
    C --> H[Select Pulley PCD from Rating Tables]
    D1 --> H
    D2 --> H
    F --> H
    G --> H
    H --> I[Verify Belt Speed ≤ 40 m/s]
    I --> J{Belt Speed 30–40 m/s?}
    J -->|Yes| K[Confirm Pulley Suitability with Manufacturer]
    J -->|No| L[Proceed with Standard Selection]
    K --> L
    L --> M[Select Taper Lock Pulley from Catalogue]
    M --> N[Verify Bush Size and Bore Compatibility]
    N --> O[Check Groove Dimensions Match Belt Section]

Taper Lock Pulley Selection Process

flowchart TD
    A[Identify Belt Section] --> B[Determine Number of Belts Required]
    B --> C[Select Pulley Pitch Diameter from Power Rating Table]
    C --> D[Look Up Taper Lock Pulley Catalogue]
    D --> E{Check Number of Grooves Available}
    E -->|Sufficient| F[Identify Bush Number]
    E -->|Insufficient| G[Increase Pulley Diameter or Change Belt Section]
    G --> C
    F --> H[Verify Max Bore ≥ Shaft Diameter]
    H -->|Yes| I[Check Pulley Type Suitability]
    H -->|No| J[Select Next Larger Bush or Pulley]
    J --> F
    I --> K[Record Key Dimensions: F, J, K, L, M, N, O]
    K --> L[Confirm Outside Diameter Fits Available Space]
    L --> M[Specify Catalogue Code for Procurement]