The WGZ Drum Shape Gear Coupling with Brake Drum integrates a cylindrical brake drum for shoe brakes per JB/T7003-93, covering 14 sizes from 710 N·m to 160,000 N·m at up to 4000 RPM. With brake drum diameters D0 from 160–800 mm and Y, J1, Z1 bore options, it is the preferred brake coupling for heavy crane hoists, mine auxiliary drives, inclined conveyor emergency stops, and spring-applied brake systems requiring high braking torque.
Crowned-tooth gear coupling with an integral cylindrical brake drum for shoe brakes. High braking torque in a compact package — the preferred brake coupling for heavy hoisting, crane drives, and large conveyor emergency stops.
The WGZ drum shape gear coupling with brake drum is a heavy-duty power transmission component that integrates a crowned-tooth gear coupling with a machined cylindrical brake drum for shoe brake systems. Conforming to JB/T7003-93, the WGZ is the member of the WG coupling family selected when a shoe brake — rather than a disc caliper brake — is specified at the drive shaft. It is the preferred brake coupling for heavy hoisting drives, large crane travel and hoist systems, mine auxiliary drives, and industrial conveyor emergency stop applications where shoe brakes deliver the highest braking force per unit actuator size.
The WGZ's defining feature is its integral cylindrical brake drum. Unlike the WGP's flat disc, which generates braking force through caliper pad clamping, the WGZ drum provides a full-circumference cylindrical surface against which shoe brake pads press radially inward. This geometry allows shoe brakes to develop substantially higher braking torque from a given actuator force — a critical advantage on large crane hoists and conveyor emergency stops where the braking torque requirement may be several times the transmission torque.
RP manufactures and supplies factory-direct to global customers.
All specifications are from the WGZ catalogue per JB/T7003-93. Dimensions in millimetres. Weight and inertia are calculated at maximum shaft hole diameter, Y type bore, without the brake drum — add drum values from the brake drum table below. The C, C1, C2 axial clearance values in the following table are for the maximum D0 for each size; for smaller D0 options, add K/2 for the chosen drum to the base table values.
| Size | Torque (N·m) |
Speed (rpm) |
Bore d1,d2,dz (mm) |
Y bore length |
J1,Z1 length |
D0 Options (mm) |
D | D2 | D4 | B | F | Inertia (Kg·m²) |
Weight (Kg) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| WGZ1 | 710 | 4000 | 12 – 42 | 32–112 | –/44/84 | 160 / 200 / 250 | 122 | 98 | 60 | 58 | 30 | 0.0078 | 5.62 |
| WGZ2 | 1250 | 4000 | 22 – 56 | 52–112 | –/60/84 | 200 / 250 / 315 | 150 | 118 | 77 | 68 | 30 | 0.022 | 9.65 |
| WGZ3 | 2500 | 4000 | 22 – 63 | 52–142 | –/60/107 | 200 / 250 / 315 | 170 | 140 | 90 | 80 | 30 | 0.047 | 16.5 |
| WGZ4 | 4500 | 3000 | 30 – 80 | 82–172 | –/84/132 | 250 / 315 / 400 | 200 | 160 | 112 | 90 | 30 | 0.098 | 25.3 |
| WGZ5 | 7100 | 3000 | 30 – 90 | 82–172 | –/84/132 | 315 / 400 | 225 | 180 | 128 | 100 | 30 | 0.174 | 34.7 |
| WGZ6 | 10000 | 3000 | 32 – 100 | 82–212 | –/107/167 | 315 / 400 | 245 | 200 | 145 | 112 | 30 | 0.29 | 51.3 |
| WGZ7 | 14000 | 2500 | 32 – 110 | 82–212 | –/107/167 | 400 / 500 | 272 | 230 | 160 | 122 | 30 | 0.53 | 68 |
| WGZ8 | 20000 | 2500 | 55 – 125 | 112–212 | –/107/167 | 400 / 450 | 290 | 245 | 176 | 136 | 30 | 0.71 | 79 |
| WGZ9 | 25000 | 2000 | 65 – 140 | 142–252 | 107/202 | 400 / 500 / 630 | 315 | 265 | 190 | 140 | 30 | 1.05 | 106.5 |
| WGZ10 | 40000 | 2000 | 75 – 160 | 142–302 | 107/242 | 400 / 500 / 630 | 355 | 300 | 225 | 165 | 30 | 1.74 | 159 |
| WGZ11 | 56000 | 1700 | 85 – 180 | 172–302 | 132/242 | 500 / 630 / 710 | 412 | 345 | 256 | 180 | 40 | 3.67 | 215 |
| WGZ12 | 80000 | 1700 | 120 – 200 | 212–352 | 167/282 | 500 / 630 / 710 | 440 | 375 | 288 | 207 | 40 | 6.4 | 303 |
| WGZ13 | 112000 | 1700 | 140 – 220 | 252–352 | 202/282 | 630 / 710 | 490 | 425 | 320 | 235 | 50 | 10.45 | 391 |
| WGZ14 | 160000 | 1500 | 160 – 260 | 302–410 | 242/330 | 710 / 800 | 545 | 462 | 362 | 265 | 50 | 17.48 | 523 |
Notes: Weight and inertia do not include the brake drum — add drum values from the table below. Max Z1 taper bore diameter is 220 mm. C, C1, C2 values: add K/2 for the chosen D0 to base table values. Y bore length range shown; J1 and Z1 lengths differ — refer to dimensional drawing.
| D0 Brake Drum Diameter (mm) |
T — Drum Width (mm) |
K — Hub Height (mm) |
Drum Weight (Kg) |
Drum Inertia (Kg·m²) |
Compatible WGZ Sizes |
|---|---|---|---|---|---|
| 160 | 70 | 6 | 2.83 | 0.014 | WGZ1 |
| 200 | 85 | 8 | 5.20 | 0.043 | WGZ1, WGZ2, WGZ3 |
| 250 | 105 | 10 | 10.1 | 0.128 | WGZ1, WGZ2, WGZ3, WGZ4 |
| 315 | 135 | 12 | 17.2 | 0.354 | WGZ2, WGZ3, WGZ4, WGZ5, WGZ6 |
| 400 | 170 | 14 | 33.4 | 1.11 | WGZ4, WGZ5, WGZ6, WGZ7, WGZ8, WGZ9, WGZ10 |
| 500 | 210 | 18 | 56.3 | 3.07 | WGZ7, WGZ8 (450 only), WGZ9, WGZ10, WGZ11 |
| 630 | 265 | 22 | 101.3 | 8.55 | WGZ9, WGZ10, WGZ11, WGZ12, WGZ13 |
| 710 | 300 | 22 | 145.8 | 15.52 | WGZ11, WGZ12, WGZ13, WGZ14 |
| 800 | 340 | 26 | 203.0 | 26.76 | WGZ14 |
Note: Drum weights and inertia values are for the drum component only. C, C1, C2 clearance values in the main table are for maximum D0 per size; for other D0 options add K/2 from this table. Max taper bore dz (Z1 type) is 220 mm per JB/T7003-93.
Custom Bore, Non-Standard D0, and Special Drum Surface Treatments Available
Need a non-standard bore, a drum diameter or width outside the catalogue range, or a hardened drum surface for high-wear applications? RP accommodates custom specifications to drawing. Send your shoe brake model, required braking torque, and shaft drawing for an engineering assessment within 24 hours.
The WGZ consists of two elements working in combination: the WG-series crowned-tooth gear coupling body and an integral cylindrical brake drum. The coupling half carries the brake drum as an extended hub — the drum outer surface is the braking interface, and the same hub carries the external crowned gear teeth that mesh with the outer sleeve's internal straight teeth for torque transmission.
When the shoe brake actuator applies, the brake shoe pads press against the drum's outer cylindrical surface over an arc contact angle. The friction force between pads and drum generates a braking torque opposing shaft rotation. The braking torque developed is proportional to the drum radius (D0/2), the total pad normal force, and the friction coefficient between pad and drum — and because the cylindrical geometry allows a wide pad contact arc (typically 60–120 degrees per shoe), shoe brakes on large drums generate very high braking torque from modest actuator forces. This is the physical advantage of shoe brakes over caliper disc brakes for heavy-duty hoisting: the torque arm is the full drum radius, and the contact area per shoe is far larger than a disc brake pad.
The gear coupling element functions identically to the WG base series — two crowned tooth meshes provide angular, radial, and axial misalignment compensation. When the shoe brake engages, the braking reaction moment at the drum hub is transmitted into the shaft through the coupling bore. The WGZ's crowned teeth absorb any axial component of this braking reaction through the tooth mesh axial sliding clearance, preventing it from being transmitted to motor or gearbox bearings as an additional axial thrust event.
The selection between WGZ (shoe brake) and WGP (disc caliper brake) is one of the most practically significant decisions in the design of a braked drive system. The rule of thumb is straightforward: choose WGZ when maximum braking torque from minimum actuator size is the primary requirement; choose WGP when fast response, consistent braking in wet or hot conditions, and compatibility with VFD-controlled drives are the priorities. For heavy hoisting and conveyor emergency stops where the braking torque must be several times the drive torque, the WGZ's shoe drum geometry is technically superior.
Both WGZ and NGCL/NGCLZ carry cylindrical brake drums for shoe brakes per JB/T7003-93. The WGZ uses the WG coupling body — a compact, high-speed crowned-tooth design that supports Y, J1, and Z1 bores and speeds up to 4000 RPM. The NGCL and NGCLZ use a different, purpose-built coupling body with a different flange geometry, optimised specifically for mine hoist and crane hoist drives where the coupling must connect to a separate drum shaft. If your application requires an intermediate shaft (spacer) between the coupling and the driven machine — common on mine hoist layouts where the hoist drum is separated from the gearbox by several hundred millimetres — the NGCLZ is the correct choice. For standard close-coupled horizontal drives requiring a shoe brake, the WGZ is the more versatile option.
The WGZ gear coupling element accommodates angular misalignment of 1.0 to 1.5 degrees per mesh, radial parallel offset, and axial displacement through the axial sliding of crowned teeth within the outer sleeve. On braked drives, the additional stress of repeated brake application cycles is superimposed on the transmission torque loading. The WGZ's crowned tooth distributes peak loads from both transmission and braking as Hertzian contact ellipses rather than edge-concentrated line contacts, significantly extending tooth life compared to straight-tooth equivalents under the same combined loading conditions.
| Feature | WGZ (this product) | WGP (disc / caliper) | WG (no brake) | Jaw Coupling |
|---|---|---|---|---|
| Braking Component | Cylindrical drum — shoe brake | Flat disc — caliper brake | None | None |
| Braking Torque per Actuator Force | High — wide arc contact area | Moderate — pad contact area | N/A | N/A |
| Performance in Dusty Conditions | Good — drum rotation expels dust | Good | N/A | N/A |
| Brake Response Speed | Moderate — shoe pivot travel | Fast — caliper clamps instantly | N/A | N/A |
| Crowned Tooth Gear Mesh | Yes — 1.0–1.5 deg tolerance | Yes — 1.0–1.5 deg tolerance | Yes — 1.0–1.5 deg tolerance | Up to 1 deg (elastomer) |
| Preferred Application | Heavy hoisting, mine hoists, large cranes, emergency stop conveyors | VFD drives, crane travel, precise positioning | Standard horizontal drives | Light–medium duty |
The WGZ is one of five variants in the WG coupling family. The table below shows where the WGZ fits relative to its family members and when to choose it.
| Factor | WG | WGP | WGC | WGZ | WGT |
|---|---|---|---|---|---|
| Standard | JB/T8854.2 | JB/T7001 | JB/T7002-93 | JB/T7003-93 | JB/T7004 |
| Braking Feature | None | Flat disc — caliper | None | Cylindrical drum — shoe brake | None |
| Shaft Orientation | Horizontal | Horizontal | Vertical | Horizontal | Horizontal |
| Intermediate Shaft | No | No | No | No | Yes |
| Max Speed | 7500 rpm (WG1) | 4000 rpm | 7500 rpm (WGC1) | 4000 rpm (WGZ1–3) | 7500 rpm (WGT1) |
| Sizes Available | 24 | 14 | 14 | 14 | 24 |
| Choose When... | Standard horizontal, no brake | Caliper disc brake; VFD drives | Vertical shaft drives | Maximum braking torque; shoe brake system; heavy hoisting | Distant shafts; axle withdrawal needed |
Crane hoist drives are among the most demanding applications for gear couplings. Each lift cycle includes a startup torque peak (2–4× rated torque during hoist motor acceleration), a running torque, and a brake application torque reversal when the hoist stops and the brake holds the load. The WGZ's crowned teeth distribute all three of these torque events as Hertzian contact ellipses, with no edge stress concentration.
When a shoe brake applies to a WGZ drum coupling, the braking reaction torque at the drum hub produces a bending moment transmitted through the coupling body to the shaft bearings. The WGZ's crowned tooth mesh minimises the transmitted bending moment through its self-centring contact geometry, and absorbs the small axial component of the braking reaction through the mesh axial sliding clearance — significantly reducing bearing loading during brake events.
The WGZ gear coupling element includes the standard WG-series built-in lubrication port, allowing re-lubrication without disassembly at 6–12 month intervals. For crane and hoist drives accessed via elevated platforms with permit-to-work controls, the ability to re-lubricate without disassembly dramatically reduces maintenance access time and safety exposure per service interval.
WGZ1, WGZ2, and WGZ3 are rated to 4000 RPM, allowing connection to standard IEC 4-pole motors on 50 Hz supplies. The cylindrical drum geometry of the WGZ is well-balanced and generates minimal vibration contribution from the brake drum mass — provided the drum is machined to specified runout tolerances.
WGZ couplings and brake drums are manufactured from forged alloy steel blanks. The coupling body uses 42CrMo4 (WGZ8 and above) or 45# carbon steel for smaller sizes. The brake drum is separately forged from 45# carbon steel or nodular cast iron depending on size, and machined to a drum outer surface cylindricity of 0.05 mm or better, with surface roughness of Ra 3.2–6.3 micrometres for optimal shoe lining wear-in and long-term uniform wear. The drum outer surface is the critical braking interface and is machined last in the production sequence to ensure final dimension accuracy is not affected by upstream machining distortions.
The coupling crowned teeth are CNC hobbed to DIN Class 7 accuracy. Tooth flanks are carburised and quenched to HRC 58–62 surface hardness with HRC 30–35 core hardness. Each WGZ coupling body is dimensionally verified against the matched drum hub bore and bolt circle before dispatch to verify the coupling-drum interface concentricity — essential for keeping drum runout within limits that prevent vibration during brake engagement.
ISO 9001:2015 quality management certification covers the full WGZ manufacturing and inspection process. CE marking applies to applicable sizes. Products are manufactured to JB/T7003-93. Every shipment includes material mill certificates with heat traceability, heat treatment records, Rockwell hardness test certificates for gear teeth and drum surface, drum cylindricity measurement records, and dimensional inspection reports. For applications requiring documentation, our team provides full support.
Our engineers communicate in technical English, review crane hoist and conveyor drive drawings, verify D0 drum diameter selection against braking torque calculations, and verify bore specifications against your motor and gearbox shaft data sheets.
WGZ couplings are available from a single unit for emergency replacement through to full project quantities. Standard sizes ship within 15–20 working days ex-works. Custom bores or non-standard drum configurations add 5–15 working days depending on complexity.
As the manufacturer of WG, WGP, WGC, WGZ, and WGT, RP supplies all variants from a single source. Projects requiring WGZ on hoist drives and WG or WGT on travel drives are handled through one engineering team, one procurement process, and one documentation set.
Challenge: Existing straight-tooth gear couplings with welded-on brake drums were failing every 8–10 months due to tooth edge loading from crane bridge deflection misalignment. Each coupling failure required a 36-hour crane outage — a significant production impact where crane availability was directly linked to steel processing throughput.
Solution: We supplied 4× WGZ10 couplings (40,000 N·m, 130 mm bore, D0 = 500 mm) replacing the original straight-tooth drum couplings. The WGZ10's crowned tooth accommodates the 0.8-degree angular misalignment generated by bridge deflection without edge loading.
Result: In 28 months since installation, no coupling failures have occurred across all four cranes. Coupling inspection at 12 months showed negligible tooth wear on all four units. Estimated saving from four avoided 36-hour outages per year: USD $192,000 over the period.
Challenge: The conveyor's existing brake drum coupling was a straight-tooth design that had failed twice in 18 months during high-load emergency stop tests. Each failure occurred at the coupling tooth-to-drum hub junction, where combined transmission torque and emergency brake reaction torque exceeded the straight-tooth coupling's capacity under the misalignment conditions of the inclined conveyor structure.
Solution: We supplied a WGZ11 coupling (56,000 N·m, 150 mm bore, Z1 taper, D0 = 630 mm) with Z1 taper bore to eliminate fretting at the motor shaft connection under cyclic torque reversals. The D0 = 630 mm drum provided the required braking torque with the existing shoe brake actuator, confirmed by calculation against the conveyor's kinetic energy and stopping distance requirement.
Result: The WGZ11 has completed eight consecutive quarterly emergency stop tests over 24 months without any coupling-related failure. The mine's engineering team noted that the Z1 taper bore specification eliminated the micro-fretting wear at the shaft bore visible on the failed straight-tooth coupling after each emergency stop event.
Challenge: Crane travel drives were experiencing premature coupling wear that could not be explained by misalignment. Root cause analysis identified that the marine salt-air environment was causing corrosion of the straight-tooth coupling contact surfaces between re-lubrication intervals, and the corrosion-softened tooth surfaces were wearing more rapidly under torque reversals during emergency brake application tests.
Solution: We supplied 12× WGZ4 couplings (4,500 N·m, 70 mm bore, D0 = 315 mm) with marine-grade stainless steel hardware and a corrosion-inhibiting EP grease pre-fill suitable for continuous salt-air exposure. The WGZ's crowned tooth profile, with its larger contact ellipse area, is more tolerant of minor surface corrosion between lubrication intervals than the edge-concentrated contact of a straight-tooth coupling.
Result: The 12 replacement WGZ units have operated for 30 months in a marine environment with no tooth wear detected at the 12-month and 24-month inspections. The terminal extended the re-lubrication interval from 3 months to 8 months. Overall maintenance cost for travel drive couplings across the six-crane fleet reduced by an estimated USD $48,000 per year.
The WGZ (JB/T7003-93) is a crowned-tooth gear coupling with an integral cylindrical brake drum for shoe brakes. Available in 14 sizes from WGZ1 (710 N·m) to WGZ14 (160,000 N·m), with brake drum diameters D0 from 160 mm to 800 mm. Y, J1, and Z1 shaft bores are supported.
The WGZ has a cylindrical drum for shoe brakes, which provide high braking torque per unit actuator force and are preferred for heavy hoisting and emergency stop applications. The WGP has a flat disc for caliper disc brakes, which offer faster response, better heat dissipation, and compatibility with VFD-controlled drives. Choose WGZ when maximum braking torque is the priority; choose WGP when braking response speed and VFD compatibility matter more.
The braking torque = shoe clamping force × friction coefficient × D0/2 × contact arc factor. Each WGZ size accepts multiple D0 options. choose the WGZ size based on transmission torque first, then choose D0 to meet the required braking torque with your specific shoe brake actuator. Our engineering team can perform this calculation with your actuator force and friction coefficient data.
Both use cylindrical brake drums for shoe brakes. The WGZ uses the WG coupling body — higher speed, Y/J1/Z1 bores, more versatile for general industrial applications. NGCL and NGCLZ use a different coupling body specifically designed for mine hoist and crane hoist flange connections. For general industrial brake drum applications, WGZ is the standard choice; for mine hoist-specific layouts, NGCL or NGCLZ may be more appropriate.
Yes. The WGZ supports Z1 taper bores (1:10 taper) up to a maximum bore diameter of 220 mm per JB/T7003-93. The Z1 taper bore provides a keyless, self-centring shaft connection that eliminates fretting corrosion at the bore-to-shaft interface under cyclic torque reversal loading.
The base C, C1, and C2 values in the main specification table are for the maximum D0 available for each WGZ size. For a smaller D0 selection, add K/2 (where K is the drum hub height for the chosen D0 from the brake drum table) to the base C, C1, and C2 values. Our engineering team can provide complete dimensional drawings for any WGZ size and D0 combination on request.
Send us your transmission torque, required braking torque, shoe brake actuator model, shaft bore dimensions, and application description. Our engineering team confirms the right WGZ size and D0 drum diameter, and provides a factory-direct quotation within 24 hours — including drum weight and inertia for your system dynamics calculation.
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