DRIVE PULLEY
The drive pulley is the powered drum of a conveyor that transmits torque from the gearbox to the belt by friction, generating the effective belt tension Te that overcomes all resistances.
The drive pulley (sometimes called the head pulley when located at the discharge end) is the powered drum that converts motor torque into belt traction. It is connected through a gearbox and either a fluid coupling or a direct coupling to one or more electric motors. As the drum rotates, friction between the lagged drum surface and the belt drives the belt forward and develops the effective tension Te — the net force the belt must pull to move the entire system.
The relationship between the tight-side tension T1 (entering the drive pulley) and the slack-side tension T2 (leaving it) is governed by the Capstan / Eytelwein equation: T1 / T2 = e^(μθ). The wrap angle θ (typically 180° on a single drum, up to 480° on a dual-drive snub configuration) and the friction coefficient μ between belt and drum together cap how much Te a single drive can transmit before slip occurs. This is why almost all heavy-duty drive pulleys carry rubber, ceramic or polyurethane lagging — it raises μ from ~0.25 (bare steel) to 0.35–0.5.
Mechanical design of the drum follows DIN 22101 (minimum diameter as a function of belt rating and utilization) plus shaft-deflection and rim-flexure checks. Insufficient diameter causes carcass over-bending and shortens splice life; insufficient lagging causes drive slip and accelerated belt cover wear. For high-power overland systems, multiple drive pulleys at head, tail or intermediate locations are used to share Te across several wrap angles.
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Related terms
- Pulley Lagging
Pulley lagging is a rubber, ceramic or polyurethane layer bonded to the drum surface of a conveyor pulley to increase the belt-to-drum friction coefficient and protect the drum from wear.
- Capstan Equation (Eytelwein)
The Capstan or Eytelwein equation T1/T2 = e^(μθ) describes the maximum tension ratio a belt can sustain across a driven pulley before slipping, given the friction coefficient μ and the wrap angle θ in radians.
- Effective Tension (Te)(Te)
Effective tension (Te) is the net tangential force that the drive pulley must transmit to the belt to overcome all motion resistances; it is the fundamental input for motor power and belt selection.
- Motorized Drive Roller(MDR)
A motorized drive roller (MDR) is a conveyor pulley with the gear-motor integrated inside the drum shell, eliminating external gearboxes, couplings and exposed drives.
- DIN 22101
DIN 22101 is the German standard 'Continuous conveyors — Belt conveyors for bulk materials — Basis for calculation and design', the de facto international reference for belt conveyor engineering.