Slit Beam Couplings (Helical Beam)

A helical or beam coupling is a one-piece coupling that uses multiple machined spiral cuts. Helical beam couplings are designed to transmit torque between two shafts while still compensating for misalignments. Helical flexible shaft couplings help to reduce residual stress in high-speed applications.
Slit beam couplings are frequently used for low torque applications but can also be used as universal joints in many applications. Because of their versatile design, helical flexible shaft couplings are used for a range of applications, depending on their size, material, and configuration.

Helical Beam Coupling Benefits

  • Zero backlash
  • High rigidity
  • High torque and torsional stiffness
  • Flexibility
  • Spiral and parallel cut designs
  • Misalignment and shaft endplay accommodations
  • Identical clockwise and counterclockwise rotational characteristics
  • Long fatigue life

Aluminum is an Ideal Material for Slit Beam Couplings

Aluminum is the most common material choice for beam couplings because it has the best mix of attributes for the most common beam coupling applications. Not only is aluminum lightweight, but it has an excellent strength to weight ration which makes it ideal for motion control applications.
Benefits of aluminum for helical beam couplings include:
  • Excellent strength-to-weight ratio
  • Lightweight for low inertia
  • High level of responsiveness
  • Fatigue Resistance
  • Long, service-free life
  • Electrolytic finish for added durability and corrosion resistance

Selecting the Right Coupling for Your Application

The size, material, and style of your helical flexible shaft coupling ultimately depends on what the coupling will be used for. When choosing a helical flexible shaft coupling, keep these criteria in mind:
Physical Space Requirements: Take into consideration basic information like shaft sizes, spacing between shafts, shaft geometry, and overall envelope size when specifying a coupling. Special consideration should be paid to designs that have large differences in shaft sizing between driving and driven components, large spacing between shafts and small windows to fit a coupling.
Misalignment:  Shaft misalignment is one of the most critical pieces of information needed to correctly specify a coupling. Misalignment can be angular, radial, axial or any combination of these. Often times, designers and engineers don’t give this proper consideration and fail to calculate tolerance stacks, as well as manufacturing inconsistencies adequately.
Environmental Considerations:  Most motion control applications exist in controlled climates without extremes in temperature, moisture, chemicals or other environmental factors that can affect the coupling performance.
Operating Conditions: Many factors exist here that designers need to be aware of when selecting a coupling. Conditions such as speed (RPM), accelerations/deceleration rates, and rotational cycling.

Performance Criteria: Finally, performance expectations from the system must be considered. Level of positioning accuracy and repeatability, amount of settling time that is tolerable when the system reaches position and overall responsiveness of the system should all be taken into account for coupling selection.

Coil Sizes for Helical Beam Couplings

The individual performance capability of each helical flexible shaft coupling is determined by:
  • Coil thickness
  • Inside diameter
  • Outside diameter
  • Number of coils
  • Number of starts
  • Material
The number of coils differ by how many starts a coupling has. A single start design has one continuous coil. A triple start 3 beam coupler has 3 parallel coils starting 120 degrees from the first. A 6 beam coupler has 2 sets of 3 beams, each beam spaced 120 degrees apart.
As the number of coils is changed, all of the characteristics of the coupling—including angular misalignment, parallel offset, and compression spring rate—are affected except the torque capacity.  As the number of starts in the slit beam coupling increase, the torsional stiffness increases, while the angular and parallel misalignment capabilities decrease.

Contact Ondrives for Your Helical Beam Shaft Couplings

No matter your application needs, Ondrives offers a high-performance helical beam coupling for you. If one of our standard 6 beam, 3 beam or single helical beam products does not work for you, we also offer our 4 slit and 8 slit beam couplings and our nylon Step-Beam couplings. We can also design and manufacture custom shaft couplings in a variety of materials, styles, and sizes.
Contact us today to learn more about our helical beam couplings or request a quote today.
Attach your precision helical beam coupler to an Ondrives.US Precision Ground Shaft, available from stock.
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