Carrier Body: Static Load Capacity 5-500 kN

Component Specifications

Definition

The carrier body, also known as the planet carrier, is a critical rotating component within a planetary gear set. It serves as the mounting structure for the planet gears (satellite gears), which are evenly spaced and rotate on their own axes while also orbiting around the sun gear. The carrier body's primary functions are to maintain precise alignment and center distance between the planet gears and the sun/ring gears, transmit torque from the planet gears to the output shaft (or vice-versa depending on configuration), and withstand significant radial and axial loads generated during operation. Its design directly influences the gear set's load distribution, efficiency, and noise-vibration-harshness (NVH) characteristics.

Working Principle

The carrier body rotates as a unit with the planet gears. In a typical planetary system, one of the three main elements (sun gear, ring gear, or carrier) is held stationary, another is used as the input, and the third serves as the output. The carrier body's rotation is determined by the motion of the planet gears as they mesh with both the sun gear (at the center) and the ring gear (on the outer perimeter). Its design ensures that all planet gears share the load equally, providing high torque density and compact power transmission.

Materials

Commonly forged or machined from medium-carbon alloy steels such as AISI 4140, 4340, or 8620 for high strength and toughness. For high-performance or weight-sensitive applications, materials may include case-hardened steels (e.g., 20MnCr5), ductile iron (e.g., GGG-40/50), or aluminum alloys (e.g., 7075-T6) with appropriate heat treatment (quenching and tempering, carburizing, or nitriding). Surface hardness typically ranges from 45-60 HRC for steel components to resist wear at gear bearing surfaces.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Weight	1-50 kg (varies with size and material)
Maximum RPM	500-10,000 rpm (depends on balance and lubrication)
Bore Diameter	20-200 mm (standard range)
Surface Finish	Ra 1.6-3.2 μm (critical bearing surfaces)
Flange Diameter	50-500 mm
Dynamic Load Rating	3-300 kN
Static Load Capacity	5-500 kN
Dimensional Tolerance	IT6-IT7
Number Of Planet Gears	3, 4, 5, or 6 (most common)
Planet Pin Hole Diameter	10-100 mm

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 6336, ISO 1328, DIN 3960, DIN 3961, AGMA 2001, AGMA 6110

Parent Products

This component is used in the following industrial products

Planet Carrier

A structural component in planetary gear systems that holds and supports the planet gears, allowing them to rotate around the sun gear while maintaining proper alignment and spacing.

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Engineering Analysis

Risks & Mitigation

Fatigue cracking due to cyclic torsional/bending loads
Wear at planet pin bore surfaces leading to misalignment
Bearing failure on planet pins causing seizure
Imbalance from manufacturing defects or damage inducing vibration
Corrosion in harsh environments weakening the structure

FMEA Triads

Trigger: Insufficient material strength or improper heat treatment
Failure: Crack propagation from stress concentrations (e.g., at pin holes)
Mitigation: Use certified alloy steels with Charpy impact testing; apply shot peening to compress surface layers; implement non-destructive testing (NDT) like magnetic particle inspection during manufacturing.

Trigger: Poor lubrication or contaminated lubricant
Failure: Accelerated adhesive wear at planet pin interfaces, leading to increased clearance and impact loads
Mitigation: Specify appropriate EP (extreme pressure) gear oils with filtration systems; design integrated oil passages for direct lubrication; use hardened and ground pins with suitable surface finish.

Trigger: Manufacturing errors in hole position or diameter
Failure: Uneven load distribution among planet gears, causing premature pitting or tooth breakage
Mitigation: Employ CNC machining with tool wear compensation; verify geometry with CMM (Coordinate Measuring Machine) inspection; implement statistical process control (SPC) for critical dimensions.

Trigger: Excessive operating loads beyond design limits
Failure: Plastic deformation or brittle fracture of the carrier arms
Mitigation: Incorporate torque limiters or overload protection in the drive system; conduct finite element analysis (FEA) during design to validate stress levels; define clear operational limits in manuals.

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Geometric tolerances per ISO 1101:2017; hole position tolerance typically within ±0.02 mm; concentricity of bore to flange within 0.03 mm TIR

Test Method

Dimensional verification via CMM; hardness testing per ISO 6508 (Rockwell); magnetic particle inspection per ASTM E1444 for surface cracks; dynamic balance testing to ISO 1940-1 G2.5 grade; functional testing under load in gearbox assembly

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

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Manufacturers of Carrier Body

Manufacturer profiles associated with Carrier Body.

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Frequently Asked Questions

What is the difference between a carrier body and a planet carrier?

These terms are generally synonymous in industrial contexts. 'Carrier body' often emphasizes the structural housing aspect, while 'planet carrier' refers to the complete assembly including pins/bearings for the planet gears. Both describe the central component that holds the planet gears.

Why are carrier bodies typically made of alloy steel?

Alloy steels like 4140 or 4340 provide an optimal balance of high tensile strength, fatigue resistance, and toughness required to withstand the cyclic bending and torsional stresses in planetary gear systems. They also respond well to heat treatment for enhanced surface hardness and core durability.

How does the number of planet gears affect carrier body design?

More planet gears (e.g., 5 vs. 3) allow higher torque capacity and better load sharing but require a larger, more rigid carrier body with precise hole spacing to maintain equal load distribution. This increases manufacturing complexity and weight.

Can a damaged carrier body be repaired?

Typically not recommended. Critical wear or cracks in the planet pin holes or mounting surfaces compromise structural integrity and precise geometry. Replacement is standard practice to ensure system reliability and prevent catastrophic gear failure.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Carrier Body