{"id":1125,"date":"2026-06-24T06:25:22","date_gmt":"2026-06-24T06:25:22","guid":{"rendered":"https:\/\/planetary-gearboxes.com\/?p=1125"},"modified":"2026-06-24T06:25:22","modified_gmt":"2026-06-24T06:25:22","slug":"slewing-drive-planetary-gearbox-for-truck-mounted-cranes","status":"publish","type":"post","link":"https:\/\/planetary-gearboxes.com\/ja\/slewing-drive-planetary-gearbox-for-truck-mounted-cranes\/","title":{"rendered":"Slewing Drive Planetary Gearbox for Truck-Mounted Cranes"},"content":{"rendered":"
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\"Slewing<\/p>\n
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Korea Ever-Power \u00b7 Application Engineering \u00b7 Truck-Mounted Cranes<\/p>\n

Slewing Drive Planetary Gearbox for Truck-Mounted Cranes \u2014 Highway Vehicle at 08:00, Heavy-Lift Crane by 08:15<\/h1>\n

The truck-mounted crane is the most versatile lifting machine in the world \u2014 it drives itself to the job, sets up in minutes, and lifts loads that would require days of assembly for a crawler or tower crane. The slewing drive must survive two completely different duty environments in the same machine: 80 km\/h highway vibration and precision heavy-lift placement.<\/p>\n

Browse Slewing Drive Planetary Gearboxes \u2192<\/a><\/p>\n<\/div>\n<\/div>\n<\/section>\n

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Two Operating Environments in One Machine \u2014 Highway and Crane Site<\/h2>\n

Every other crane type operates exclusively as a crane. The truck-mounted crane also operates as a road vehicle \u2014 subject to highway speed limits, road surface vibration, bridge weight limits, and traffic regulations. The slewing drive planetary gearbox<\/a> must be designed for both environments:<\/p>\n

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Transport Mode (Highway)<\/div>\n

The upper structure is locked at 0 degrees (boom over the rear). The slewing brake is engaged and the pinion remains in mesh with the ring gear. At 80 km\/h on a rough road, the entire truck vibrates at 5 to 25 Hz \u2014 transmitted through the chassis to the slewing ring and drive. The pinion teeth are loaded by vibration against the ring gear at a single locked contact zone, producing fretting wear identical to the wind turbine yaw fretting problem but at higher frequency and with the additional vibration energy of a multi-axle truck at highway speed.<\/p>\n<\/div>\n

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Crane Mode (On Outriggers)<\/div>\n

The outriggers are extended and the upper structure is unlocked. The slewing drive rotates the boom, cab, and suspended load through 360 degrees. The duty cycle is moderate (5 to 20 lifts per hour) but the loads can be heavy (25 to 500 tonnes) at radii of 3 to 60 metres. Smooth, proportional speed control is essential for precision placement on congested construction sites.<\/p>\n<\/div>\n<\/div>\n

A truck-mounted crane may travel 20,000 to 50,000 km per year at highway speed. At 15 Hz average road vibration, this produces approximately 10 to 25 million fretting micro-cycles per year at the locked pinion-ring tooth contact. Over 10 to 15 years, this transport-mode fretting can consume more tooth surface material than the crane-mode slewing operations \u2014 a counter-intuitive finding that was not recognised in early slewing drive specifications and led to premature pinion replacement on high-mileage cranes.<\/p>\n

The practical mitigation for transport fretting is surprisingly simple: rotate the upper structure by 10 to 15 degrees at every refuelling stop \u2014 shifting the locked contact position to a fresh tooth pair. This distributes the fretting across multiple tooth positions instead of concentrating it on a single pair. Crane operators who follow this practice consistently report 30 to 50% longer pinion life compared to operators who park at the same locked position for every road transfer. Some modern crane models include a transport pinion lock that lifts the pinion out of mesh with the ring gear during road travel \u2014 eliminating transport fretting entirely.<\/p>\n

The fretting damage mechanism is distinct from conventional gear tooth wear. In normal slewing, the teeth roll and slide under hydrodynamic lubrication \u2014 producing gradual, distributed surface wear. In transport fretting, the teeth oscillate \u00b10.01 to 0.05 mm under boundary-contact conditions \u2014 producing oxide debris that acts as an abrasive between the contact surfaces. This oxidative fretting removes surface material at 5 to 20 times the rate of equivalent rolling-sliding contact at the same load. The visual signature is a reddish-brown patch on the tooth flanks at the locked contact position \u2014 often mistaken for surface rust but actually a combination of iron oxide fretting debris and micro-cracking. Once the fretting patch reaches a depth of 0.05 to 0.10 mm, the surface hardness at that zone is compromised and macro-pitting can initiate under subsequent crane-mode loading \u2014 converting a superficial fretting mark into a structural gear failure.<\/p>\n<\/section>\n

\"Slewing<\/p>\n

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Outrigger Configurations \u2014 Why the Stability Envelope Changes at Every Setup<\/h2>\n

A crawler crane has a fixed stability footprint. A tower crane has a fixed footprint. A truck-mounted crane has a variable footprint \u2014 the outriggers can be set in different configurations depending on available space. Each configuration produces a different stability envelope \u2014 and the slewing drive must operate within whichever configuration is set.<\/p>\n

\n\n\n\n\n\n\n\n\n
Outrigger Setup<\/th>\nFootprint<\/th>\nCapacity<\/th>\nSlewing<\/th>\n<\/tr>\n<\/thead>\n
Fully extended (all 4)<\/td>\nMax (7×7 m)<\/td>\n100%<\/td>\n360\u00b0 unrestricted<\/td>\n<\/tr>\n
Partially extended (50%)<\/td>\n5×5 m<\/td>\n50\u201370%<\/td>\n360\u00b0 reduced<\/td>\n<\/tr>\n
Asymmetric (2+2)<\/td>\n7×5 m<\/td>\nVariable<\/td>\nVaries by angle<\/td>\n<\/tr>\n
On wheels (no outriggers)<\/td>\nTyre contact<\/td>\n10\u201325%<\/td>\n\u00b110\u201330\u00b0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
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The asymmetric setup is the most dangerous for the slewing drive. When outriggers are set asymmetrically (common on narrow streets, beside buildings, or near excavations), the tipping line distance varies with the slewing angle. The crane has full capacity over the fully-extended side and significantly reduced capacity over the partially-extended side. The load moment indicator (LMI) must be correctly programmed for the actual outrigger configuration \u2014 and the slewing drive must interface with the LMI to restrict slewing speed or range in the reduced-capacity sector.<\/p>\n

If the LMI is incorrectly configured (or if the operator overrides the warning), slewing a load from the strong side to the weak side can exceed the tipping limit. The slewing drive does not directly cause this failure \u2014 but the slewing drive interface with the LMI is the last mechanical line of defence. A properly integrated system stops or slows the slewing drive before the boom enters the restricted sector. Modern truck cranes have automatic outrigger-position sensors that restrict the LMI and slewing drive to the correct capacity and range for the actual setup \u2014 eliminating the risk of manual configuration error.<\/p>\n

The on-wheels (no outrigger) operating mode requires the most restrictive slewing drive constraints. With only the tyre contact patches providing the stability footprint, the stability margin is extremely narrow \u2014 a 25-tonne crane on wheels may be rated for only 2.5 to 6 tonnes of lifting capacity at short radius, with slewing limited to a \u00b110 to 30 degree sector behind the truck centreline. The slewing drive must enforce these limits through hard mechanical stops or electronically locked angular range \u2014 because exceeding the on-wheels sector limit can overturn the machine within 1 to 2 degrees of additional rotation. There is no recovery margin: once the tipping line is crossed, the crane overturns in less than 2 seconds. This is the most safety-critical slewing drive function on any truck-mounted crane.<\/p>\n<\/div>\n

\"ZR45<\/div>\n<\/div>\n<\/section>\n
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Telescopic Boom Oscillation \u2014 Why Truck Cranes Need Softer Speed Ramps Than Lattice Cranes<\/h2>\n
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A fully extended telescopic boom (40 to 60+ metres) is more flexible than a lattice boom of the same length \u2014 the nested tube sections have lower moment of inertia than an open lattice structure. When the slewing drive accelerates or decelerates aggressively, the boom tip oscillates laterally at its natural frequency (typically 0.3 to 1.0 Hz). On long-reach configurations, this oscillation can produce tip displacements of 200 to 500 mm \u2014 making precision load placement impossible until the oscillation damps out (3 to 10 seconds).<\/p>\n

Operators who attempt to correct the oscillation by counter-slewing often amplify it instead \u2014 because the human reaction time (0.3 to 0.5 seconds) is too slow to match the 0.3 to 1.0 Hz oscillation frequency, and the corrective input arrives out of phase. The most effective oscillation control is prevention: soft slewing speed ramps that limit angular acceleration to values below the boom natural frequency excitation threshold.<\/p>\n

Most modern truck cranes include electronically controlled slewing speed ramps that automatically reduce the maximum acceleration on long boom configurations. The crane control system reads the boom extension sensor, calculates the boom natural frequency, and limits the slewing acceleration to a value that will not excite oscillation \u2014 typically 0.1 to 0.3 rad\/s2 for fully extended booms versus 0.5 to 1.0 rad\/s2 for short configurations. The slewing drive must respond to these variable speed ramp commands with proportional, jerk-free torque delivery across the full range of ramp settings.<\/p>\n

The gear mesh quality directly affects the boom oscillation behaviour. A slewing drive with DIN Class 8 gears produces torque pulsation at the tooth mesh frequency that can excite the boom at harmonic multiples of the mesh frequency \u2014 even when the fundamental acceleration ramp is below the excitation threshold. DIN Class 6 gears reduce this mesh-induced excitation by 60 to 80%, making them the minimum standard for modern truck cranes with telescopic booms exceeding 40 metres. For cranes with electronic anti-oscillation systems (active boom damping), the gear quality requirement is even more stringent \u2014 the system cannot distinguish between mesh-induced vibration and wind-induced oscillation, and will waste energy attempting to cancel the gear noise.<\/p>\n<\/div>\n

\"Compact<\/div>\n<\/div>\n<\/section>\n

\"CNC<\/p>\n

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Three Failure Modes Specific to Truck-Mounted Crane Slewing Drives<\/h2>\n
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1<\/div>\n
Transport-mode fretting from highway vibration at the locked pinion position<\/div>\n<\/div>\n

Over 20,000 to 50,000 km of annual road travel, the accumulated fretting at the locked contact position produces a visible wear mark on both the pinion and ring gear teeth \u2014 a wear pattern that does not exist on stationary crane types. On high-mileage rental fleet cranes, the transport fretting can consume more tooth material than the crane-mode slewing. The damage is concentrated on a single tooth pair and progressively deepens \u2014 reducing the effective tooth contact area and increasing the contact stress, which accelerates further wear in a self-reinforcing cycle. On rental fleet cranes that travel 40,000 to 60,000 km per year between jobs, the transport fretting can reduce pinion life from the crane-mode expectation of 12,000 hours to as little as 5,000 hours \u2014 a 60% reduction that is entirely attributable to the road travel environment rather than the crane lifting operations. The economic impact on a rental fleet of 20 to 50 truck cranes can reach USD 50,000 to 200,000 per year in accelerated pinion replacements \u2014 making transport fretting management one of the most cost-effective maintenance practices for mobile crane fleet operators.<\/p>\n

Prevention: Rotate upper structure 10\u201315\u00b0 at every refuelling stop. Grease pinion-ring mesh before and after every road transfer. Consider transport pinion locks on high-mileage machines.<\/div>\n<\/div>\n
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2<\/div>\n
Overturning from slewing into the reduced-capacity sector on asymmetric outriggers<\/div>\n<\/div>\n

When outriggers are set asymmetrically, the crane capacity varies by slewing angle. If the LMI is incorrectly configured (or overridden), slewing a load from the strong sector into the weak sector can exceed the tipping limit. The slewing drive does not cause this failure directly \u2014 but the drive interface with the LMI is the last line of defence. The most dangerous scenario is when an operator lifts a load on the fully-extended side and then slews 180 degrees to the partially-extended side \u2014 experiencing a progressive capacity reduction that may not trigger the LMI warning until the tipping point has already been passed. The accident investigation records from regulatory authorities show that asymmetric outrigger overturning is the single most common cause of truck crane tipping events \u2014 accounting for 25 to 40% of all mobile crane overturning incidents in mature markets. The slewing drive encoder and LMI integration are therefore safety-critical systems, not convenience features \u2014 and the encoder reliability, calibration frequency, and LMI software validation must meet the functional safety requirements of the applicable crane standard (EN 13000 in Europe, ASME B30.5 in North America).<\/p>\n

Prevention: Mandatory LMI configuration for actual outrigger setup. Automatic slewing-range restriction linked to outrigger sensors. Encoder output from slewing drive<\/a> to LMI for real-time position monitoring.<\/div>\n<\/div>\n
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3<\/div>\n
Telescopic boom oscillation from aggressive slewing on long boom configurations<\/div>\n<\/div>\n

At 50-metre extension, a telescopic boom has 3 to 5 times less lateral stiffness than a lattice boom of the same length. Lower stiffness means a lower natural frequency (0.3 to 1.0 Hz versus 0.8 to 2.0 Hz for lattice) and larger oscillation amplitude for the same slewing input. The oscillation is self-sustaining if the operator attempts counter-slewing corrections \u2014 because the human reaction time exceeds the oscillation period. On cranes without electronic speed-ramp control, the oscillation can only be stopped by releasing the slewing joystick and waiting 3 to 10 seconds for natural damping \u2014 reducing effective throughput by 15 to 25% on long-reach configurations.<\/p>\n

Prevention: Electronically controlled slewing ramps with boom-extension-dependent acceleration limiting. Jerk-free proportional torque delivery from the slewing drive.<\/div>\n<\/div>\n<\/div>\n<\/section>\n
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Slewing Drive Planetary Gearbox for Truck-Mounted Cranes \u2014 Frequently Asked Questions<\/h2>\n
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How does a truck crane slewing drive differ from a crawler crane drive?<\/h3>\n

Three key differences: (1) transport vibration fretting \u2014 10 to 25 million micro-cycles per year from highway driving that crawler cranes never experience; (2) variable stability \u2014 outrigger configurations change the envelope at every setup, requiring LMI integration; and (3) telescopic boom flexibility \u2014 the nested-tube boom oscillates more than a lattice boom, requiring softer slewing ramps. A crawler crane drive does not need fretting resistance, LMI integration for variable outriggers, or the ultra-soft acceleration profiles that flexible telescopic booms demand.<\/p>\n<\/div>\n

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What is the typical service life?<\/h3>\n

8,000 to 15,000 hours for the gearbox. Pinion life is more variable than on stationary cranes \u2014 it depends on the ratio of highway km to crane hours. A crane traveling 40,000 km\/year may need pinion replacement at 6,000 to 8,000 hours due to transport fretting, even though crane-mode wear would permit 12,000+ hours. Rotating the upper structure at refuelling stops extends pinion life by 30 to 50%. For rental fleet operators who track maintenance cost per machine-hour, the pinion replacement cost per hour should be calculated including the road-travel contribution \u2014 a crane that travels 40,000 km per year should have its pinion life estimated at 60 to 70% of the manufacturer specification for stationary-only cranes.<\/p>\n<\/div>\n

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Can the truck crane slew with no outriggers?<\/h3>\n

Some truck cranes are rated for limited on-wheels lifting at 10 to 25% of full capacity with slewing restricted to \u00b110 to 30 degrees. The slewing drive must enforce this restriction through hard stops or electronically limited range. Most modern cranes have automatic outrigger sensors that restrict the LMI and drive to on-wheels capacity and range when outriggers are retracted.<\/p>\n<\/div>\n

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Why does the telescopic boom oscillate more than a lattice boom?<\/h3>\n

At 50-metre extension, a telescopic boom has 3 to 5 times less lateral stiffness than a lattice of the same length \u2014 lower moment of inertia from the nested-tube cross-section versus the wide, deep lattice truss. Lower stiffness produces a lower natural frequency (0.3 to 1.0 Hz vs 0.8 to 2.0 Hz) and larger amplitude for the same slewing acceleration. The slewing speed ramp must be softer (longer acceleration time) on long telescopic configurations.<\/p>\n<\/div>\n

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Does Korea Ever-Power supply slewing drives for truck-mounted cranes?<\/h3>\n

Yes. 15,000 to 120,000 Nm covering 25-tonne city cranes through 500-tonne all-terrain machines. Transport-mode fretting-resistant tooth profiles, LMI encoder interface provisions, and variable-ramp speed control compatibility are standard. Provide the crane manufacturer, model, maximum boom length, and typical annual road mileage for a specification that accounts for both crane-mode torque and transport-mode vibration environment.<\/p>\n<\/div>\n<\/div>\n<\/section>\n

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Truck-Mounted Crane Slewing Drives \u2014 Highway-Proven, Outrigger-Adaptive, Oscillation-Controlled<\/div>\n

Korea Ever-Power provides truck crane slewing drives from 15,000 to 120,000 Nm with dual-environment durability, LMI integration, and telescopic-boom speed ramp control.<\/p>\n<\/div>\n

View Slewing Drive Range \u2192<\/a><\/p>\n
sales@planetary-gearboxes.com<\/div>\n<\/div>\n<\/div>\n<\/section>\n

\u7de8\u96c6\u8005: Cxm<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

Korea Ever-Power \u00b7 Application Engineering \u00b7 Truck-Mounted Cranes Slewing Drive Planetary Gearbox for Truck-Mounted Cranes \u2014 Highway Vehicle at 08:00, Heavy-Lift Crane by 08:15 The truck-mounted crane is the most versatile lifting machine in the world \u2014 it drives itself to the job, sets up in minutes, and lifts loads that would require days of assembly for a crawler or tower crane. The slewing drive must survive two completely different duty environments in the same machine: 80 km\/h highway vibration and precision heavy-lift placement. Browse Slewing Drive Planetary Gearboxes \u2192 Two Operating Environments in One Machine \u2014 Highway and Crane Site Every other crane type operates exclusively as a crane. […]<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[965],"tags":[],"class_list":["post-1125","post","type-post","status-publish","format-standard","hentry","category-application-and-technical-guid"],"_links":{"self":[{"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/posts\/1125","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/comments?post=1125"}],"version-history":[{"count":2,"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/posts\/1125\/revisions"}],"predecessor-version":[{"id":1127,"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/posts\/1125\/revisions\/1127"}],"wp:attachment":[{"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/media?parent=1125"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/categories?post=1125"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/tags?post=1125"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}