Gearmotor Selector Guide

Conveyor torque is calculated per ISO 5048 and CEMA Standard 502, which define the total resistance torque as the sum of load torque (due to mass and incline), frictional torque (belt/pulley and bearing losses), and acceleration torque. Our Gearmotor Selector uses the fundamental equation: $\tau = \frac{F \cdot r}{\eta}$, where $F$ is the effective tractive force (N), $r$ is the drive pulley radius (m), and $\eta$ is system efficiency (e.g., 85% = 0.85). This aligns with ISO 14798 for mechanical power transmission safety margins and accounts for steady-state operation—acceleration torque must be added separately if start/stop frequency exceeds 5 cycles/hour per IEC 60034-1 duty classification.

A 100% duty cycle implies continuous operation without rest, requiring thermal derating per IEC 60034-1 (S1 rating). Real-world conveyors rarely sustain true 100% load; however, selecting for S1 ensures margin against thermal overload. If actual duty is intermittent (e.g., 60% on-time), an S3-rated motor may allow downsizing—but only if peak torque doesn’t exceed 1.5× continuous rating and thermal time constant is validated. Always cross-check manufacturer’s thermal curves: exceeding frame temperature limits (IEC 60034-1 Class F insulation = 155°C hotspot) accelerates winding degradation. For critical applications, add a 1.2–1.5 safety factor to calculated torque and power.

Pulley diameter directly scales torque via mechanical advantage: torque $\tau = F \cdot r$, where $r = d/2$. A smaller pulley increases required torque for the same tractive force (e.g., halving diameter doubles torque demand), while speed remains unchanged because belt linear velocity $v = \omega \cdot r$—so angular velocity $\omega$ must double to maintain $v$, further increasing power ($P = \tau \cdot \omega$). This lever effect dominates over speed in low-RPM, high-torque conveyor applications. Per DIN 8195, pulley diameter also affects belt wrap angle and slip risk—undersized pulleys (<80 mm for standard HTD belts) accelerate wear and reduce efficiency, invalidating the 85% default assumption.

The ‘System Efficiency’ (default 85%) aggregates typical losses across the full drivetrain: gear reducer (92–96% for helical, 75–85% for worm), belt/pulley slip (2–5%), bearing friction (1–2%), and chain or coupling losses (1–3%). It excludes motor electrical losses (handled separately in motor efficiency specs). Accuracy depends on component quality: precision-ground helical gears achieve >95%, while cast-iron worm gears drop to ~70% at 10:1 ratio. For rigorous sizing, use measured values per ISO/TR 11377 or manufacturer datasheets. If unknown, 85% is conservative for industrial-grade helical-gearmotors—but verify with actual test data if energy efficiency (ISO 50001) or thermal management is critical.

For food, pharmaceutical, or washdown environments, stainless steel (AISI 316) housings are mandated by FDA 21 CFR Part 110 and EHEDG Guideline Doc. 23 for corrosion resistance and cleanability. Aluminum housings—though lighter and cost-effective—are unsuitable unless fully encapsulated in IP69K-rated polymer coatings, as they corrode under alkaline cleaners (pH >10) and chlorine-based sanitizers. Note: Housing material doesn’t affect torque rating, but thermal conductivity differs (Al: 237 W/m·K vs. SS: 16 W/m·K), impacting cooling. Always specify IP69K ingress protection and NSF/ANSI 169 certification—not just ‘stainless’—to ensure compliance with sanitary design standards.

The current selector assumes horizontal conveyors only. Inclined applications require additional torque to overcome gravitational component: $\tau_{\text{incl}} = m \cdot g \cdot \sin(\theta) \cdot r / \eta$, where $\theta$ is incline angle. Since the tool lacks incline angle input, using it for inclines >5° risks severe undersizing—especially above 10°, where gravity torque dominates. Per CEMA Standard 502, incline corrections also increase effective load by 10–20% due to material slippage and belt tension rise. For accuracy, manually compute total torque including incline, then input the result as ‘conveyor_load’ adjusted via $m_{\text{eff}} = m \cdot (1 + 0.2 \cdot \sin\theta)$, or use dedicated incline calculators compliant with ISO 21872-1 for bulk material handling.

The recommended model provides nominal torque/power compliance—but mechanical integration requires verification against ISO 4762 (socket head cap screws), ISO 273 (shaft tolerances), and ISO 286-1 (H7/h6 fits for couplings). Check shaft extension length (per ISO 12100 for guarding clearance), flange type (e.g., IEC 60034-7 IM B5/B14), and brake/encoder options. Misalignment >0.05 mm/mm causes premature bearing failure (per DIN ISO 10816-3 vibration limits). Always overlay CAD models with vendor-provided STEP files and confirm thermal expansion compatibility—especially when mounting to aluminum frames (CTE ≈ 23 μm/m·K) versus cast iron gearmotor housings (CTE ≈ 10 μm/m·K).