T1 (TIGHT SIDE TENSION) (T1)
T1 is the maximum belt tension at the drive pulley entry — the sum of slack-side tension T2 plus effective tension Te — and is the value used to size belt rating in kN per metre of belt width.
T1, the tight-side tension, is the belt tension at the point where the belt is just entering the drive pulley after travelling along the full carrying run. It is the highest steady-state tension anywhere in the belt loop, because the drive pulley adds the entire effective tension Te to the slack-side tension T2 over its wrap: T1 = T2 + Te. T1 (combined with the chosen [safety factor](/glossary/safety-factor-belt)) is what sizes the belt's breaking-strength rating; pick a belt rating SF × T1 / belt width, in N/mm.
T1 grows as the conveyor profile becomes more demanding: longer centre distance, steeper incline, denser cargo or higher belt speed all push T1 up. Per DIN 22101, Te (and therefore T1) is built from the main resistance (friction factor × length × mass), slope resistance (incline × mass), secondary resistance (chutes, cleaners, accelerated material) and any special resistances. T2 is then derived from the Eytelwein condition — T2 = Te / (e^(μθ) − 1) — and added to Te to give the full T1.
Transient operating cases can push T1 above its steady-state value. Full-load starting on a multi-drive overland conveyor, or emergency stop on a steep incline, generates dynamic tensions of 1.4–2.0× steady-state Te. For long high-power belts, dynamic analysis tools simulate these transients and check that T1_dynamic ÷ belt-width still leaves safe margin against the carcass rating; the [belt tension calculator](/tools/conveyor-belt-tension-calculator) handles the steady-state case directly.
Formula
T1 = T2 + Te (steady state at drive pulley entry)
| Symbol | Meaning | Unit |
|---|---|---|
| T1 | Tight-side tension entering the drive pulley | N |
| T2 | Slack-side tension leaving the drive pulley | N |
| Te | Effective tension across the drive | N |
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Related terms
- 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.
- T2 (Slack Side Tension)(T2)
T2 is the minimum belt tension on the slack side of the drive pulley; it must exceed Te / (e^(μθ) − 1) per Eytelwein to prevent drive slip, and it is set in the field by the take-up.
- 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.
- Safety Factor (SF)(SF)
Safety factor is the ratio of belt breaking strength to maximum working tension; DIN 22101 sets S₀ ≈ 8 for fabric belts and 6.7 for steel cord, with reductions allowed when splice quality is verified.