Audible noise is evidence to investigate, but fault location depends on whether the sound tracks speed, torque or the machine structure.
Helical Gearbox Noise Diagnosis by Speed and Load
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EP-H4 Four-Stage Helical Inline Gearbox
EP-H4 is a four-stage helical inline gearbox providing the deepest ratios (up to 500:1) and the highest torques (up to 500 kNm) in the HB helical series. Sizes 7–26 serve the most demanding ultra-slow heavy industrial drives where simpler solutions are inadequate.
MOQ: Flexible. Minimum order value USD 1,500; mixed orders and trial quantities welcome.
EP-H4 Four-Stage Helical Inline Gearbox
The highest-ratio, highest-torque member of the HB helical series — four stages delivering up to 500:1 and 500 kNm for the most demanding ultra-slow industrial drives. Sizes 7–26.
Product Overview: Ultimate Helical Ratio Depth
The EP-H4 represents the pinnacle of the Ever Power HB series helical inline gearbox range. Four carburised and ground helical gear stages are integrated into a single housing to achieve overall speed ratios of 50:1 to 500:1 — delivering output shaft speeds as low as 3 rpm from a standard 1500 rpm four-pole induction motor. At the largest available frame (Size 26), the EP-H4 delivers a nominal output torque of 500 kNm on a continuous-duty basis.
Available in sizes 7 through 26 across three dimensional groups, the EP-H4 addresses the most challenging end of the industrial drive spectrum: the applications where very high reduction ratios and very high torques must coexist without the mechanical complexity of tandem gearboxes, hydraulic drives, or complex coupling arrangements.
Representative applications include large ball mill drives, thickener rake systems with extremely slow rotation, heavy ship-unloader drives, large rotary drum drives in cement and chemicals, and slow horizontal mixer drives in the food and pharmaceutical industries.
Four-Stage Architecture: Engineering Justification
Adding a fourth stage beyond the three-stage H3 serves a specific engineering purpose: it extends the achievable ratio ceiling without requiring helical gear tooth proportions that would compromise strength or manufacturability. At very high single-stage ratios (above ~6.3:1 per stage), the small pinion tooth count drops to a level where undercutting or thin-tooth geometry reduces the load capacity. Four moderate-ratio stages maintain all gear pairs within the optimal tooth-count range.
The four-stage architecture also provides an engineering path to very high torques at very low speeds that cannot be achieved with fewer stages without resort to extremely large gear diameters. At 500:1 ratio, 100 kW of motor power at 1500 rpm translates to approximately 300 kNm at 3 rpm output — a torque level that would require an enormous drum or worm gearbox in an alternative design, with correspondingly poor efficiency and reliability.
Efficiency of the EP-H4 is approximately 94–95% at rated load (four stages at ~98–99% each). At high reduction ratios, the motor power drawn is far lower than it would be at the output shaft speed with fewer stages, so the absolute power loss remains modest even at 500 kNm output.
Size, Torque & Ratio Range
EP-H4 is available in sizes 7 to 26, covering the highest torque and ratio demands within the HB helical series:
| Size | Nom. Output Torque (kNm) | Max Input Speed (rpm) | Ratio Range (i) | Representative Applications |
|---|---|---|---|---|
| 7 | 1.50 | ≤1500 | 50–350 | High-ratio auxiliary drives |
| 10 | 4.00 | ≤1500 | 50–400 | Heavy agitators, feeders |
| 13 | 12.0 | ≤1000 | 50–450 | Slow conveyor drives |
| 16 | 30.0 | ≤750 | 50–450 | Drum drives, kiln auxiliaries |
| 19 | 80.0 | ≤600 | 50–500 | Ball mill auxiliary, thickeners |
| 22 | 220. | ≤500 | 50–500 | Large industrial drives |
| 26 | 500. | ≤400 | 50–500 | Ship unloaders, large mills |
EP-H4 Horizontal Dimension Drawing — Sizes 7–12
EP-H4 Horizontal Dimension Drawing — Sizes 13–22
EP-H4 Vertical Dimension Drawing — Sizes 7–12
At very high ratios and torques, thermal management and lubrication system selection are critical. Consult our technical team before specifying sizes 19 and above.
Technical Features
Four Carburised & Ground Helical Stages
Each of the four gear pairs is independently carburised to achieve 58–62 HRC surface hardness, then precision-ground to DIN 5. Four stages provide the ratio depth of worm or planetary alternatives with far superior efficiency.
Optimised Housing for Four-Stage Geometry
The housing is dimensioned to accommodate four intermediate bearing positions with adequate wall thickness between gear chambers. Oil passages are designed to deliver lubricant to all four meshes under splash or forced-circulation conditions.
Forced Lubrication for Large Frames
For sizes 19–26 under continuous duty, a gear-pump lubrication circuit is strongly recommended. This delivers filtered, temperature-controlled oil to all four gear meshes and bearing positions, extending service life significantly in heavy-duty installations.
Three Size Groups, Six Frame Classes
Dimensional groups for sizes 7–12, 13–22, and 23–26 maintain optimal housing proportions across the full range. Each group has independent horizontal and vertical drawing sets reflecting the different internal lubrication configurations.
Ultra-Low Output Speeds
At the 500:1 maximum ratio, a 1450 rpm motor produces 2.9 rpm output — enabling drives that would otherwise require fluid couplings, torque converters, or hydraulic circuits. The H4 delivers this mechanically, with the reliability and efficiency advantages of precision gear contact.
Compatible with All H-Series Accessories
Cooling fan kits, oil temperature monitoring sensors, vibration monitoring studs, and torque arm reaction systems available from the H2/H3 series are compatible with H4 where applicable. Contact us to specify accessories for your installation.
Industry Applications — Where EP-H4 Is Specified
EP-H4 is not a general-purpose unit — it is selected for the specific class of drives where ratio depth and torque magnitude eliminate all simpler alternatives:
| Industry | Application | Primary Requirement |
|---|---|---|
| Cement | Kiln main drive (auxiliary), raw mill | 500:1 ratio, 500 kNm |
| Mining | Thickener rake, ball mill auxiliary | Continuous 24/7, shock tolerance |
| Port & Shipping | Ship unloaders, stacker-reclaimer slew | Very high torque, intermittent peaks |
| Chemical | Large polymer reactor agitators | Sealed housing, low contamination |
| Steel | Coiler pinch roll, slow roll line | Reversing loads, heavy shock |
| Renewable Energy | Wave energy capture, tidal drives | High ratio, corrosion-resistant seals |
Selection & Sizing Guidance
When to Choose H4 Over H3. If the required ratio exceeds approximately 250:1, or if both high ratio (above 100:1) and high torque (above 150 kNm) are required simultaneously, the EP-H4 is the correct helical series unit. Below these thresholds, the three-stage H3 will deliver a lighter, lower-cost solution.
Thermal Management is Critical. At four stages and high continuous power, internal heat generation is significant. Always provide ambient temperature and ventilation conditions when specifying a large H4 unit. For ambient temperatures above 35°C or enclosed installations, forced lubrication with an oil cooler circuit is mandatory for sizes 16 and above.
Foundation Loading. At 500 kNm output torque, reaction forces on the mounting feet and torque arm are substantial. Provide foundation design data including static torque reaction and dynamic load factor to the structural engineer. Torque arm reaction brackets are available for retrofit installations with inadequate base rigidity.
Contact our engineering team with your complete drive specification for a detailed recommendation covering unit size, lubrication system, accessories, and foundation loads.
Frequently Asked Questions
Explore the Full HB Series
Enquire About EP-H4
Four-stage helical drives require careful application review. Share your ratio, torque, ambient conditions, and duty cycle — our engineers will recommend the correct size, lubrication system, and accessories.
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