Conveyor motor and gearbox check
Check a conveyor drive: drum speed, required gearbox ratio, motor torque against rated torque, starting-torque margin, actual belt speed and gearbox service factor.
Result
How it works
A drive that is fine on paper can still trip, overheat or fail to start loaded. This check follows the motor-sizing chain: from belt speed and drum diameter to drum speed and the gearbox ratio needed, from effective tension to drum torque and motor-shaft torque, and then compares the result with the motor nameplate.
It also checks the starting-torque reserve (the motor datasheet’s starting torque against the running torque, with Oriental Motor’s ×2 margin for supply voltage dips), the belt speed the nameplate ratio really gives, and — if you enter the gearbox rating — the service factor achieved.
Formula
Drum speed: NG = 60 · v / (π · D); required ratio i = n / NG Drum torque: TL = Te · D / (2 η); motor torque: TM = TL / (i · ηG) Rated torque: Tr = 9549.3 · P / n (from P = T · ω); load = TM / Tr Start-up: motor starting torque / TM ≥ margin (Oriental Motor: 2) Belt speed with ratio i: v = n · π · D / (60 · i); gearbox service factor = rated output torque / TL
| Symbol | Meaning | Unit |
|---|---|---|
| Te | Effective tension at the drive drum | kN |
| v | Belt speed | m/s |
| D | Drive drum diameter over lagging | m |
| n | Motor rated speed | rpm |
| P | Motor rated power | kW |
| i | Gearbox ratio | — |
| ηG | Gearbox and coupling efficiency | — |
| η | Drum/transmission efficiency (1 if Te already includes it) | — |
Worked example
Inputs: Effective tension Te = 18 kN; Belt speed = 1.3 m/s; Drum diameter over lagging = 524 mm; Motor rated power = 30 kW; Motor rated speed = 1440 rpm; Gearbox ratio (blank = required) = 31.5 ; Gearbox + coupling efficiency = 0.94 ; Drum efficiency η = ; Motor starting torque (datasheet) = 200 % of rated; Start-up margin = 2 ×; Gearbox rated output torque = kN·m; Required service factor = .
- 30 kW, 1440 rpm motor; gearbox i = 31.5, ηG = 0.94; drum 500 mm + 2 × 12 mm lagging = 524 mm; Te = 18 kN; v = 1.3 m/s
- NG = 47.38 rpm; required ratio = 30.39
- TL = 4716 N·m; TM = 159.3 N·m; rated torque 198.9 N·m → 80 % load
- Starting torque 200 % = 398 N·m → margin 2.50 (≥ 2 OK)
- Belt speed with i = 31.5: 1.254 m/s (-3.5 %) — recheck capacity
- Method check: Oriental Motor’s own p.7 example re-run in SI gives 33.4 r/min, 320 oz-in and 9.7 oz-in.
Assumptions and limits
- Te must include all resistances; take it from the effective tension calculator.
- Starting torque, gearbox rated torque and the required service factor come from the motor and gearbox makers — never assumed.
- Oriental Motor’s ×2 starting margin is a small-motor rule for supply voltage variation; large drives with soft starters, VFDs or fluid couplings need the supplier’s starting analysis (acceleration time, thermal limits).
- Oriental Motor’s product tables (permitted inertia, series safety factors) are not used.
- Screening only; not a drive design approval.
Screening estimate, not a design approval. Verify measured inputs, current standards, manufacturer limits and site procedures before purchasing, cutting or installation. Isolate and lock out equipment before any hands-on measurement.
Questions
How much torque reserve should a conveyor motor have?
Oriental Motor uses twice the running torque at start to allow for supply voltage dips and says a margin of 1.5–2 or more is usual. Check the actual starting torque on your motor datasheet.
Why does my belt run slower than design?
The nameplate gearbox ratio seldom matches the required ratio exactly, and the drum diameter grows with lagging. The calculator shows the actual speed and the change in percent.
Source notes
- Oriental Motor, “Motor Sizing Calculations”, technical reference (edition not stated), belt-conveyor examples pp.7–8 — drum speed, ratio, load and motor torque, ×2 starting margin and speed verification. Method used with credit; tests re-run its example in SI.
- Rated torque from the definition of power P = T · ω (9549.3 = 60 000 / 2π).
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The full app adds saved conveyor profiles, material and temperature assessment, result reports, offline use and English/Hindi field guidance.