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Slewing Bearings in Beam Transport Vehicles
Created on 08.03
Slewing Bearings in Beam Transport Vehicles
How a 700 mm slewing ring keeps 1,000-tonne girders moving
Application case from Anhui Yuanfeng
What is a beam transport vehicle? A beam transport vehicle (also called a girder transporter) is a special-purpose machine used in bridge construction to carry precast concrete box girders from the casting yard to the erection site. A single girder can weigh 800 to 1,200 tonnes, and the vehicle that carries it may have 40 or more wheels arranged on multiple independently-steered axles.
Every steering axle group pivots on a slewing bearing. The bearing must transmit the full axle load to the chassis while allowing precise steering rotation - often under extreme load, shock, and dirty construction-site conditions. This makes beam transporters one of the most demanding applications for a rotation bearing of this size.
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The Application: Multi-Axle Steering Under Heavy Load
Why this vehicle demands more from a bearing than a crane
A beam transporter does not rotate quickly. Its steering motion is slow - typically a few degrees per second - but the forces involved are enormous. Each axle group carries a share of the total payload, and every steering movement is performed at full load, on uneven ground, often at low speed with high torque.
Load characteristics
Unlike a crane slewing ring, which handles large moment loads from an offset boom, a beam transporter bearing works with a different load profile:
Load Type | Magnitude | Source |
Axial Load | Dominant | Girder weight through each axle |
Radial Load | Moderate | Lateral forces when steering |
Moment Load | Moderate-High | Off-center loads on uneven ground |
Design implication: The bearing must be selected primarily on axial load capacity, with enough moment capacity to survive uneven terrain. Oversizing is common in this application because the cost of a field failure - a stalled transporter blocking a bridge construction site - far exceeds the cost of a larger bearing.
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The 700 mm Slewing Ring We Build for This Application
A compact diameter with heavy-duty specifications
The steering pivot bearing for this beam transporter has a 700 mm outer diameter - compact by slewing ring standards, but engineered for serious duty. Our production run for this application used 42CrMo steel with raceway induction hardening, ground raceways, and a bolted mounting pattern to match the customer axle module.
At this diameter, the manufacturing challenges are different from larger rings. Tolerances that scale with diameter are tighter in absolute terms, and the raceway hardness pattern must be verified carefully because the hardened zone is a larger fraction of the total section.
Key specifications
Parameter | Specification |
Outer diameter | 700 mm |
Material | 42CrMo, quenched and tempered |
Raceway treatment | Induction hardened, HRC 55-62 |
Raceway finish | Ground |
Mounting | Bolted pattern per customer drawing |
Inspection | Zeiss CMM, full report with each unit |
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From Forging to Finished Ring
The photos above show the 700 mm rings at the semi-finished stage - after turning, with the raceway geometry already cut. The next steps in our Hefei facility are induction hardening of the raceway, grinding to final tolerance, drilling the bolt holes, and a full CMM inspection before assembly of the rolling elements.
For a beam transporter application, we pay special attention to two things during manufacturing:
Hardened layer depth verification
The raceway of a 700 mm ring carries a higher contact stress per unit area than a larger ring under the same axial load. Hardened layer depth must be verified by hardness-gradient testing, not just a surface reading - typically 2-4 mm for this section size, confirmed against a third-party test report on request.
Mounting bolt precision
The bearing bolts directly to the axle module with no housing adjustment. Bolt hole position tolerance must be tight enough that the bearing drops into place without reaming on site. We verify the full bolt pattern with CMM measurement before shipment.
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Why the Steering Pivot Is the Right Place for a Slewing Ring
Each axle module of a beam transporter needs to steer independently so the vehicle can negotiate tight radii on construction sites. The slewing bearing in the pivot does three jobs at once: it carries the vertical load of the girder, it allows smooth rotation for steering, and it keeps the steering axis stable under lateral forces.
Alternative designs - kingpins or bushings - wear quickly under this combination of heavy axial load and slow, high-torque rotation. A hardened, ground raceway with rolling elements handles millions of steering cycles with minimal wear and predictable maintenance intervals.
Why customers choose Yuanfeng for this application: We manufacture the ring in-house from raw steel - no outsourcing of machining or heat treatment. Every unit ships with a CMM inspection report and full production traceability. For a component buried deep in a 1,000-tonne machine, that documentation is what makes field maintenance predictable.
Custom Slewing Bearings for Special-Purpose Vehicles
Beam transporters, tunnel boring machines, drill rigs, and other special-purpose vehicles all rely on slewing bearings engineered to their specific load case. At Anhui Yuanfeng, we produce slewing rings from 200 mm to 6,000 mm in single-row ball, double-row ball, cross roller, and three-row roller configurations - custom-designed to your bolt pattern, load requirements, and gear specification.
Send us your application details or a drawing, and we will recommend the right configuration for your vehicle.
Frequently Asked Questions
Quick answers for buyers sourcing slewing rings for special-purpose vehicles
Q: What size slewing bearings do beam transport vehicles use?
Steering pivot bearings on beam transporters typically range from 500 mm to 1,200 mm in outer diameter, depending on axle load. The 700 mm ring in this article is a common size for medium-capacity transporters carrying 600-900 tonne girders.
Q: Which bearing type is best for a vehicle steering pivot?
Single-row four-point contact ball bearings are the most common choice for steering pivots, balancing load capacity, cost, and compact height. Three-row roller types are used only on the heaviest transporters where moment loads from uneven terrain are extreme.
Q: What steel grade is recommended for heavy-duty slewing rings?
42CrMo is preferred for vehicle applications because of its toughness under shock loads and its excellent response to raceway induction hardening (HRC 55-62 surface). 50Mn is a cost-effective alternative for moderate, predictable load cases.
Q: Can you manufacture a custom slewing ring from our drawing?
Yes. Yuanfeng produces custom slewing rings from 200 mm to 6,000 mm to customer bolt patterns, load cases, and gear specifications. Custom orders start from a single piece - no minimum batch size.
Q: Do you provide inspection reports with each bearing?
Every bearing ships with a CMM inspection report covering raceway roundness, bolt hole positions, and gear accuracy, plus a hardness-gradient test report on request. Full production traceability is documented per unit.
Have a different question? Send your application details and our engineers will reply within 24 hours.
Anhui Yuanfeng Slewing Rings Co., Ltd.
CE & ISO 9001 Certified Manufacturer
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