Industrial Chain Drives: Sizing, Selection and Maintenance: Taper Lock Bushes

Taper Lock Bushes

• Taper lock bushes are the quickest and simplest method of securing sprockets and couplings to shafts (both imperial and metric)
• The tapered surface of both bush and sprocket/coupling hub combine to create a load-bearing connection via the lock action of hardened high-tensile screws
• Taper bush ranges from different manufacturers are generally fully interchangeable
• When ordering, specify both the bush number and bore size required
• Available in metric bore sizes ranging from small (e.g., 9 mm) up to very large bores depending on bush series
• Standard bush series include: TB1008, TB1210, TB1215, TB1610, TB1615, TB2012, TB2017, TB2517, TB2525, TB3020, TB3030, TB3535, TB4040
• Each bush series accommodates a specific range of bore sizes and is matched to corresponding sprocket or coupling hub dimensions

Chain Drives — Introduction

• Two primary chain standards exist: national standard (metric) and imperial standard (inch-based)
• Chains manufactured to both standards are available; the metric standard is more commonly used in many regions
• There is no single unified national standard for roller chain in all countries — chains are made to comply with one or both international standards
• Chain size is specified by the chain pitch (distance between adjacent link pins)
• Both standards use imperial (inch) pitch sizes; metric pitch equivalents are listed in catalogues
• Chain may be specified by inch or mm pitch; all other catalogue dimensions are given in metric (mm) units

Types of Roller Chain

• Simple (Simplex) — single strand; most common for general power transmission
• Duplex — two parallel strands; higher load capacity
• Triplex — three parallel strands; highest standard load capacity
• Quadruplex — four parallel strands; for very heavy-duty applications
• Other varieties include: straight-sided chain, double pitch chain, cranked link chain, plastic bush chain, O-ring chain, hollow bearing pin chain, and sidebow chain
• The most common type for power transmission is the high-waisted precision steel roller chain
• Chains used for conveying rather than power transmission have different data and attachments

Roller Chain Construction

• A precision steel roller chain consists of a series of journal bearings held in precise relationship by constraining link plates
• Each bearing consists of a bearing pin and bush on which the chain roller revolves
• The bearing pin and bush are case-hardened to allow articulation under high pressures
• The design permits both load-carrying pressures and gearing action to be transmitted via the chain rollers
• Chains are classified according to pitch, roller diameter, and width between inner plates
• These dimensions collectively determine the form and width of the sprocket teeth

Chain Drive Expected Life

• When properly selected, installed, lubricated, and maintained with loads not exceeding design values, a quality roller chain is expected to have an operating life of 8 million cycles or 15,000 hours
• The rating charts in selection procedures assume a minimum life expectancy of 15,000 hours with proper installation and lubrication

Standards Reference Guide

Chain Drive Selection Method

Symbols, Terms, and Units

• Z₁ = Number of teeth on driver sprocket (pinion)
• Z₂ = Number of teeth on driven sprocket (wheel)
• C = Centre distance (mm)
• P = Chain pitch (mm)
• i = Drive ratio
• L = Chain length (pitches)

Selection Summary (Step-by-Step)

Step 1 — Select Drive Ratio and Sprockets

• Use standard sprocket sizes to choose a ratio based on available tooth counts
• Best practice: use an odd number of teeth combined with an even number of chain pitches
• Ideally, sprockets should have a minimum of 19 teeth
• If operating at high speed or subject to impulsive loads, the smaller sprocket should have at least 25 teeth and should be hardened
• Maximum recommended teeth on any sprocket: 114 teeth
• Drive ratio formula: i = Z₂ / Z₁
• For large ratio drives, check that the angle of lap on Z₁ is not less than 120°

Step 2 — Establish Application Factor (f₁)

• f₁ accounts for dynamic overloads depending on the characteristics of both the driver and driven machines
• Can be selected directly or by analogy using the application factor chart

Driver classifications:

• Smooth Running — electric motors, steam & gas turbines, internal combustion engines with hydraulic coupling
• Slight Shocks — internal combustion engines with 6+ cylinders, or engines with mechanical coupling, electric motors with frequent starts
• Moderate Shocks — internal combustion engines with fewer than 6 cylinders, with mechanical coupling

Step 3 — Tooth Factor (f₂)

• The tooth factor modifies the final power selection based on the size of the driver sprocket
• Formula: f₂ = 19 / Z₁
• The rating curves in standard charts are based on a 19-tooth sprocket; smaller sprockets increase the chain load per tooth

Step 4 — Calculate Selection Power

$$\text{Selection Power} = \text{Power (kW)} \times f_1 \times f_2$$

• This adjusted power value is then used with the rating charts

Step 5 — Select Chain Drive

• From the rating chart, select the smallest pitch of simple chain that can transmit the selection power at the speed of the driver sprocket Z₁
• This normally results in the most economical drive
• If the selection power exceeds the capacity of the simple chain, consider a multiplex chain (duplex or triplex) of the same pitch size

Step 6 — Calculate Chain Length

• Chain length in pitches (L) for a two-point drive at any centre distance:

$$L = \frac{Z_1 + Z_2}{2} + \frac{2C}{P} + \frac{\left(\frac{Z_2 - Z_1}{2\pi}\right)^2 \times P}{C}$$

• Round up the calculated number of pitches to a whole number of even pitches
• Odd numbers of pitches require a cranked link (offset link), which is not recommended
• If a jockey sprocket is used for adjustment, add two pitches to the chain length
• C is the contemplated centre distance in mm; should generally be between 30–50 pitches
• Example: For 1/2″ pitch chain, C = 1.5 × 25.4 × 40 = 1524 mm

Step 7 — Calculate Exact Centre Distance

• The actual centre distance for the chain length (L) calculated above will generally be greater than originally contemplated
• Revised centre distance formula:

$$C = \frac{P}{8} \left[ 2L - Z_1 - Z_2 + \sqrt{(2L - Z_2 - Z_1)^2 - \frac{\pi}{3.88}(Z_2 - Z_1)^2} \right]$$

Where:

• P = Chain pitch (mm)
• L = Chain length (pitches)
• Z₁ = Number of teeth in driver sprocket
• Z₂ = Number of teeth in driven sprocket

Step 8 — Choose Lubrication Method

• The recommended lubrication method is based on chain speed and power transmitted, found in the rating charts

Rating Chart Construction

• Rating charts appear complex but are constructed from three simple lines:
  • Link plate fatigue line — dominates at lower speeds (failure if maximum power recommendation is exceeded)
  • Pin galling line — occurs due to boundary lubrication breakdown at very high speeds
  • Bush and roller fatigue curve — at the intersection of the fatigue and galling lines, this curve dominates
• The rounded tops of each selection curve account for these intersections
• For driver sprocket speeds less than 10 rpm: multiply the transmitted power by 10/n and read from the 10 rpm column (where n = driver sprocket speed)
• 1 Kilowatt = 1.34 hp

Chain Suspension Force

• The force between one link and the next due to chain mass is small and is internally balanced within the chain
• This causes the chain to adopt a sagging catenary shape between the sprockets
• Allowance must be made in installation for slightly different postures adopted by the chain between zero and maximum load

Lubrication

• Chain drives must be protected against dirt and moisture
• Use good quality non-detergent mineral-based oil
• A periodic change of oil is desirable
• Heavy oils and greases are generally too stiff to enter chain working surfaces and should not be used
• The lubricant must reach the bearing areas of the chain by being directed between the inner and outer link plates, preferably at the point where the chain enters the sprocket on the bottom strand

Lubricant Viscosity by Temperature

• For the majority of applications, a multigrade oil (e.g., SAE 20/50) would be suitable

Use of Grease

• Grease lubrication is not recommended; if used, the following conditions apply:
  • Limit chain speed to 4 m/s
  • Normal greases applied to the outside surfaces only seal the bearing surfaces and will not work — causes premature failure
  • Grease must be heated until fluid and the chain immersed and allowed to soak until all air bubbles cease
  • Regular cleaning and regreasing at intervals is required depending on power and speed
  • Temperatures above 80°C will cause damage to many greases and reduce effectiveness

Abnormal Ambient Temperatures

• For elevated temperatures up to 250°C, use dry lubricants such as colloidal graphite, MoS₂ in white spirit, or poly-alkaline glycol carriers
• For low temperatures between −5°C and −40°C, special low-temperature initial greases and subsequent oil lubricants are necessary

Four Lubrication Methods

Effect of Temperature on Chain Drives

• Chain and chaincase temperatures during operation are an important control factor
• Depending on severity of use, special attention to lubrication method may be required
• Chain temperatures above 100°C should be avoided if possible
• Chain can generally give acceptable performance up to around 250°C in some circumstances
• Improving lubrication cooling effectiveness: increase oil volume to up to 4.5 litres per minute per chain strand and incorporate external cooling for the oil

Bearing Pressures

• When a chain has been correctly selected, the expected failure mode over a very long period is wear
• A key indicator of likely wear performance is bearing pressure — the magnitude of contact pressure between the key mating surfaces (pin and bush)
• Bearing pressure is calculated by dividing the working load by the bearing area
• Bearing areas for standard chains are quoted in manufacturer designer data

Bearing Pressure vs Chain Velocity (General Guidance)

• These values give an indication only and should not replace the standard chain selection methods

Transmission Sprockets — Data Summary

• Sprocket data is provided for various standard pitches
• Materials available: Steel (standard) and Heavy Duty Cast Iron
• Bore types: Plain bore and Taper bore (using taper lock bushes)
• Chain configurations: Simple, Duplex, and Triplex

Sprocket Data in the supplied reference

• Sprockets are available with welded hubs for certain larger sizes
• Rebore, keyway, and setscrew modification services are available from manufacturers

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

Mermaid Diagrams

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