{"id":2017,"date":"2026-04-10T06:45:41","date_gmt":"2026-04-10T06:45:41","guid":{"rendered":"https:\/\/helicalcutgears.top\/?post_type=product&p=2017"},"modified":"2026-04-10T06:50:32","modified_gmt":"2026-04-10T06:50:32","slug":"double-helical-gear-zero-axial-thrust-for-high-torque-parallel-shaft-drives","status":"publish","type":"product","link":"https:\/\/helicalcutgears.top\/cs\/product\/double-helical-gear-zero-axial-thrust-for-high-torque-parallel-shaft-drives\/","title":{"rendered":"Dvojit\u00e9 \u0161ikm\u00e9 ozuben\u00ed \u2013 nulov\u00e1 axi\u00e1ln\u00ed s\u00edla pro pohony s paraleln\u00edmi h\u0159\u00eddeli a vysok\u00fdm to\u010div\u00fdm momentem"},"content":{"rendered":"
\n

What Is a Double Helical Gear<\/h2>\n

A dvojit\u00e9 spir\u00e1lov\u00e9 ozuben\u00e9 kolo<\/strong> consists of two opposing helical sections \u2014 one left-hand helix and one right-hand helix \u2014 machined onto the same gear blank at identical twist angles. The arrangement is sometimes called a herringbone gear, though strictly speaking a herringbone has no central groove while a dvojit\u00e9 spir\u00e1lov\u00e9 ozuben\u00e9 kolo<\/strong> has a relief groove separating the two helix halves. Both transmit rotational motion between parallel shafts. The fundamental advantage is that the axial thrust generated by the left-hand section and the right-hand section act in exactly opposite directions, canceling one another within the gear body. Supporting bearings therefore carry radial force only, which significantly extends bearing service life and reduces shaft deflection under heavy torque.<\/p>\n

\"Dvojit\u00e9<\/p>\n

Because axial thrust is no longer a constraint, dvojit\u00e1 \u0161ikm\u00e1 ozuben\u00e1 kola<\/strong> can operate with helix angles between 20\u00b0 and 45\u00b0. Single ozuben\u00e1 kola se \u0161roubovicov\u00fdm \u0159ezem<\/strong> are generally limited to 15\u00b0\u201320\u00b0 before bearing thrust loads become problematic. A wider helix angle increases the overlap ratio \u2014 more tooth pairs share the load at any instant \u2014 which raises the power capacity of a given gear size and smooths vibration at high speeds. These properties make them the standard choice for crane gearboxes, marine reduction drives, industrial turbines, and rolling mill drives where both torque density and quiet operation matter. Korea Ever-Power Worm Gear Co.,Ltd supplies dvojit\u00e1 \u0161ikm\u00e1 ozuben\u00e1 kola<\/strong> in alloy steel, carbon steel, and nodular cast iron, with hobbed or ground tooth finishes to match the required ISO accuracy class.<\/p>\n

Technical Specifications: Double vs Single Helical Gear<\/h2>\n

The comparison below covers the principal engineering differences between single and dvojit\u00e1 \u0161ikm\u00e1 ozuben\u00e1 kola<\/strong>. Understanding these distinctions is essential when evaluating which type suits a specific power transmission requirement.<\/p>\n

\"single<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n\n\n
Jednoduch\u00e9 \u0161ikm\u00e9 ozuben\u00e9 kolo<\/th>\nDvojit\u00e9 \u0161ikm\u00e9 ozuben\u00e9 kolo<\/th>\n<\/tr>\n
A single helical gear has teeth inclined in any one direction (either left-hand helix or right-hand helix).<\/td>\nThe double-helical gear consists of two identical gears jointed on the same axis and teeth in opposite directions (one has a left-hand helix, and the other has a right-hand helix).<\/td>\n<\/tr>\n
Single helical gears develop axial thrust force and exert the same on corresponding bearings. It also generates radial force.<\/td>\nThe resultant thrust force developed in double helical gear is zero. Thus it exerts no axial load on bearings. But radial force exists as usual.<\/td>\n<\/tr>\n
The power transmission capacity of a single helical gear is comparatively low.<\/td>\nDouble helical gears can transmit more significant power for exact size and module.<\/td>\n<\/tr>\n
Single helical gears are cheaper.<\/td>\nDouble helical gears are costlier as design and fabrication are complex and time-consuming.<\/td>\n<\/tr>\n
High precision is usually not desired during the alignment of the gears.<\/td>\nTwo helical gears must be aligned precisely; otherwise, thrust force will not balance properly, resulting in negative vibration.<\/td>\n<\/tr>\n
Because of thrust load, a high helix angle cannot be used. Helix angle for single helical gear usually varies from 15\u00b0 to 20\u00b0.<\/td>\nDue to the canceled thrust load, a high helix angle (20\u00b0\u201345\u00b0) can be advantageously used in double helical gears.<\/td>\n<\/tr>\n
The efficiency of single helical gear is comparatively low.<\/td>\nDouble helical gears can provide higher efficiency.<\/td>\n<\/tr>\n
The bearing span (distance between two bearings) is short.<\/td>\nThe bearing span is longer due to a central relief groove in between two gears.<\/td>\n<\/tr>\n
Single helical gears are suitable for mechanical drives or power transmission requirements, where each application usually requires a unique design for powers, speeds, and configuration.<\/td>\nDouble helical gears are suitable for high power transmission requirements in cranes, marine drives, or turbines.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

How Double Helical Gears Work<\/h2>\n

Gradual Tooth Engagement<\/h3>\n

Unlike straight-cut spur gears where the full tooth width contacts simultaneously and creates a sharp load spike, a spir\u00e1lov\u00e9 ozuben\u00e9 kolo<\/strong> tooth makes contact at one edge first, then the contact line travels diagonally across the tooth face as the gear rotates. This progressive engagement distributes the impact energy over a measurable arc of rotation, producing significantly lower noise and vibration. In the double-helix format, both tooth sets remain continuously engaged through each revolution, which essentially doubles the active contact length compared to a single-helical gear of the same face width. The practical result is a smoother output torque curve and less dynamic load amplification at the mesh frequency \u2014 a property valued in turbine gearboxes and high-speed reduction stages.<\/p>\n

Thrust Cancellation Inside the Gear Body<\/h3>\n

Ka\u017ed\u00fd ozuben\u00e9 kolo se spir\u00e1lov\u00fdm \u0159ezem<\/strong> produces an axial thrust component equal to the tangential force multiplied by the tangent of the helix angle. In a standard single-helical gear at 20\u00b0 helix angle, this thrust can reach 36% of the tangential load \u2014 a significant bearing load at high torque. The double-helix design routes equal and opposite thrust forces through the gear body itself. The central relief groove provides the clearance required to cut both sets of teeth independently without interference and ensures the thrust from one half does not simply transfer to the groove wall. The net axial force reaching the shaft and bearings is effectively zero, allowing the use of simpler and less expensive radial bearings rather than thrust-capable angular-contact or tapered-roller assemblies.<\/p>\n

\"parts<\/p>\n

Double Helical Gear vs Spur Gear \u2014 Side-by-Side Comparison<\/h2>\n

A common question when specifying a gearbox is whether a dvojit\u00e9 spir\u00e1lov\u00e9 ozuben\u00e9 kolo<\/strong> or a \u010deln\u00ed ozuben\u00e9 kolo<\/strong> is the better fit. The answer depends on speed, noise tolerance, axial space, and load requirements. The table below compares the two on the parameters that typically drive the decision.<\/p>\n

\"spur<\/p>\n

\n\n\n\n\n\n\n\n\n\n
Parametr<\/th>\n\u010celn\u00ed ozuben\u00e9 kolo<\/th>\nDvojit\u00e9 \u0161ikm\u00e9 ozuben\u00e9 kolo<\/th>\n<\/tr>\n
Noise level<\/td>\nHigher \u2014 full tooth contact occurs at once<\/td>\nLow \u2014 gradual diagonal contact on both helix halves<\/td>\n<\/tr>\n
Axi\u00e1ln\u00ed tah<\/td>\n\u017d\u00e1dn\u00fd<\/td>\nNone (internally canceled)<\/td>\n<\/tr>\n
Load capacity (same size)<\/td>\nM\u00edrn\u00fd<\/td>\nHigh \u2014 higher contact ratio distributes load<\/td>\n<\/tr>\n
\u00da\u010dinnost p\u0159enosu<\/td>\n98%\u201399%<\/td>\n97%\u201399% (slight friction from helix sliding)<\/td>\n<\/tr>\n
Slo\u017eitost v\u00fdroby<\/td>\nN\u00edzk\u00fd<\/td>\nHigh \u2014 dual helix requires precise alignment and special tooling<\/td>\n<\/tr>\n
Speed range<\/td>\nLow to moderate<\/td>\nLow to high \u2014 well suited for high-speed heavy-load applications<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

For moderate speeds and simpler gearboxes, a standard spur gear may be the economical choice. Where noise matters, loads are heavy, or shaft and bearing configurations need simplification, dvojit\u00e1 \u0161ikm\u00e1 ozuben\u00e1 kola<\/strong> provide clear technical advantages at a higher but justifiable cost. For a precise selection recommendation based on your torque, speed, and duty cycle, contact Korea Ever-Power directly.<\/p>\n

Core Performance Advantages<\/h2>\n
\n
\n

\u2699 Zero Axial Bearing Load<\/strong><\/p>\n

Paired helices cancel axial thrust internally. Bearings handle radial force only, which lowers operating temperature and extends service intervals.<\/p>\n<\/div>\n

\n

\u2699 Higher Helix Angle Range<\/strong><\/p>\n

Helix angles of 20\u00b0\u201345\u00b0 are practical, compared to 15\u00b0\u201320\u00b0 for single-helical types. A larger angle raises the overlap ratio and load capacity for the same gear diameter.<\/p>\n<\/div>\n

\n

\u2699 Low Noise and Vibration<\/strong><\/p>\n

Continuous diagonal tooth engagement on both helix halves suppresses mesh-frequency noise \u2014 a critical factor in marine cabins, turbine halls, and industrial facilities with noise regulations.<\/p>\n<\/div>\n

\n

\u2699 High Power Density<\/strong><\/p>\n

For identical module and center distance, a double helical gear transmits more torque than its single-helical equivalent, allowing more compact gearbox designs without sacrificing capacity.<\/p>\n<\/div>\n

\n

\u2699 Extended Tooth Life<\/strong><\/p>\n

Load shared across a larger number of simultaneously engaged teeth reduces individual tooth root stress and Hertzian contact pressure, slowing pitting and fatigue progression.<\/p>\n<\/div>\n

\n

\u2699 Bearing and Shaft Simplification<\/strong><\/p>\n

With axial loads eliminated, standard deep-groove or cylindrical roller bearings are often sufficient. This reduces procurement complexity and lowers the cost of spare bearing inventory.<\/p>\n<\/div>\n<\/div>\n

\"d\u00edlna<\/p>\n

Typical Applications<\/h2>\n

\"application<\/p>\n

Marine Reduction Gearboxes<\/h3>\n

Shipboard gearboxes must reduce diesel or gas-turbine output speed to propeller shaft speed \u2014 often a ratio of 5:1 to 15:1 \u2014 while transmitting several thousand kilowatts. Dvojit\u00e1 \u0161ikm\u00e1 ozuben\u00e1 kola<\/strong> are standard in this duty because the zero-thrust characteristic allows the gearbox to be built without the heavy thrust collars required in single-helical arrangements. The low noise level also matters: noise transmitted from the gearbox through the hull structure affects crew comfort and, in naval vessels, acoustic signature.<\/p>\n

Power Generation Turbines<\/h3>\n

Steam and gas turbines spin at 3,000\u201315,000 rpm and must be geared down to 1,500 rpm or 1,800 rpm for standard generator coupling. At these speeds, even small unbalanced forces cause significant vibration and noise. Dvojit\u00e1 \u0161ikm\u00e1 ozuben\u00e1 kola<\/strong> are the industry default for turbine step-down gearboxes because the self-balancing helix arrangement accommodates the high speeds and continuous full-load duty cycles typical of utility-scale generators. Carburized and ground tooth finishes in ISO accuracy class 5 or better are common specifications for this duty.<\/p>\n

Heavy-Lift Cranes and Industrial Hoists<\/h3>\n

In gantry cranes, ship-loader drives, and large industrial hoists, the gearbox experiences frequent load reversals as the load is raised, held, and lowered. Reversing load direction in a gear mesh can excite backlash-related noise and impact stresses. The continuous tooth engagement of dvojit\u00e1 \u0161ikm\u00e1 ozuben\u00e1 kola<\/strong> reduces these transient impact loads by keeping more teeth in mesh at all times, and the zero-thrust characteristic means that load reversals do not flip the direction of axial force at the bearings. The result is reduced gearbox maintenance costs over the operating life of the crane.<\/p>\n

Selection Parameters for Double Helical Gears<\/h2>\n

Specifying a dvojit\u00e9 spir\u00e1lov\u00e9 ozuben\u00e9 kolo<\/strong> correctly requires confirming the following parameters before placing an order. Providing complete data upfront avoids design iterations and delays.<\/p>\n

    \n
  1. Power and torque:<\/strong> Rated power (kW) and peak torque (Nm) at the gear mesh, including service factor for load type (smooth, moderate shock, heavy shock).<\/li>\n
  2. Speed:<\/strong> Input and output shaft speeds (rpm); this determines the pitch line velocity and influences the required accuracy grade.<\/li>\n
  3. Module and tooth count:<\/strong> Confirm the normal module (Mn), helix angle (typically 20\u00b0\u201335\u00b0 for standard double-helical applications), and number of teeth on pinion and gear.<\/li>\n
  4. Center distance and bore:<\/strong> Fixed center distance if retrofitting; bore diameter, keyway, and shaft fit tolerance for both gear and pinion.<\/li>\n
  5. Material and hardness:<\/strong> Carbon steel (45# or 40Cr), alloy steel (20CrMnTi for carburized applications), or nodular cast iron (QT600-3). Specify surface hardness (HRC) or core hardness (HB) as required by the duty cycle.<\/li>\n
  6. Accuracy class:<\/strong> ISO 1328 or AGMA class. ISO 6\u20138 for general industrial; ISO 4\u20136 for high-speed or precision drives. This determines whether hobbing or grinding is required for the tooth finish.<\/li>\n<\/ol>\n

    Related Gear Products and Drive Components<\/h2>\n