High Loads and Unpredictable Misalignment? MULTICROWN Is the Answer

In this article, it’s all about connections – the mechanical kind. We’re focusing on high-torque transmission between gearboxes and driven machinery in demanding industrial applications. Our attention turns to ESCOGEAR gear couplings with patented MULTICROWN technology from ESCO, Belgian specialists in shaft couplings with an eighty-year tradition.

• No Oversizing, but Robust: ESCOGEAR Couplings
• MULTICROWN – Misalignment without Penalty
• Gear Tooth Accuracy
• Flange Connection
• Product Range + Manufacturing Flexibility

No Oversizing, but Robust: ESCOGEAR Couplings

ESCOGEAR couplings are the right choice wherever thermal expansion, dynamic forces, or bearing wear lead to unpredictable shaft displacement during operation.

Typical applications for the ESCOGEAR F series include rolling mills, cranes, mixers, and crushers, while the ESCOGEAR C & C-M series targets applications with limited installation space – such as heavy conveyors, machine tools, compressors, and pumps.

The key function of shaft couplings – beyond transmitting the required torque – is to maintain torque capacity under misalignment, whether caused by radial or angular misalignment, axial displacement, or a combination of these.

In gear couplings, torque is transmitted through the external teeth of the hubs engaging with the internal teeth of the sleeve. Early straight-tooth designs could only accommodate misalignment within a few angular minutes – any larger deflection resulted in point contact and rapid wear. Standard crowned gear teeth improved on this: the crowned tooth profile allows angular misalignment typically up to 0.5° to 1°. However, the contact area shifts toward the tooth edge, local stresses increase, and transmittable torque drops accordingly.

MULTICROWN – Radial and Angular Misalignment without Penalty

Torque capacity therefore remains practically independent of misalignment – unlike standard tooth profiles, where torque capacity always has to be derated to account for uncertain operating misalignment that can only be estimated approximately.

The advantages are clear:

• Smaller Coupling for the Same Torque
  Less installation space, lower weight, and lower purchase cost

• Simplified Coupling Selection
  No additional safety factors needed for uncertain operating misalignment

• Longer Service Life
  Teeth are not overstressed under combined torque and misalignment loading

ESCO backs this up with concrete figures:

Comparison of ESCOGEAR and three anonymized competitor models: nominal torque T_n with derating at misalignment 2 × 0.5°

While competitor couplings continue to lose torque capacity at higher misalignment angles, ESCOGEAR with the MULTICROWN profile holds its full rated value up to angular misalignment of 2 × 0.75°. The following graph illustrates this clearly.

At 0.75° misalignment, a competitor coupling with standard crowned gear teeth transmits only 73% of its torque capacity, compared to 100% with MULTICROWN tooth geometry.

Together, the MULTICROWN tooth profile and double engagement design address both radial and angular misalignment. Axial displacement is accommodated by the length of the sleeve’s internal gear teeth.

Gear Tooth Accuracy → Minimal Backlash, Precise Sleeve Centering…

ESCOGEAR couplings are manufactured to AGMA 8–10 quality classes, ensuring uniform load distribution across all teeth. In extreme cases, pitch errors can cause actual tooth loads to reach twice the calculated value – inevitably leading to a significant reduction in coupling service life.

F Series Flange Connection – Exceptional Bolt Durability

Product Range + Manufacturing Flexibility

Standard catalog models of the ESCOGEAR F series with a flange-split sleeve cover torque ranges up to 5,040,000 Nm with shaft diameters up to 1,130 mm – handling the vast majority of industrial applications without requiring a custom-engineered solution.

The significantly lighter and more compact ESCOGEAR C & C-M series with a one-piece sleeve complements the range for space- and weight-constrained applications, with maximum torque up to 560,000 Nm and bore diameters up to 470 mm.

Our long-term experience with leading global manufacturers gives us a real appreciation for ESCO’s responsive, customer-first approach – whether that means engineering support for non-standard designs or specific requirements for component surface treatments. Their stock of standard catalog sizes also helps cut lead times even for applications that would otherwise require custom-made solutions.

The material for ESCOGEAR couplings is C45 carbon steel. For applications requiring higher torque capacity within the same installation envelope, couplings can be custom-manufactured in quenched and tempered 42CrMo4 alloy steel. The uprated nominal torque reaches twice the standard value – up to 10,080,000 Nm for the ESCOGEAR FST type in FSUST design.

For extremely demanding operating conditions and further improvement in fatigue strength, tooth nitriding is also available on request.

A low-temperature design is available on request (vs. the standard operating range of −20 °C to +100 °C). For potentially explosive environments, a special ATEX version is available. Feel free to contact us regarding any additional or custom requirements.

ESCOGEAR Gear Couplings in the TYMA CZ Online Store