Selecting the best power transmission gearbox

With a variety of gearboxes on the market that can fulfill diverse requirements, selecting the best power transmission gearbox can be a challenge.  Avoid making a wrong decision and wasting money on a more expensive gearbox that isn’t necessary.

While some aspects of gearbox selection are universal, there are some elements that are industry-specific.  For the power transmission industry, application calculations can be impacted by output RPM, motor horsepower and frame size, as well as overhung load.

• Output RPM The standard ratio for a gearbox to operate is a 1750 input RPM at 60 Hz.  Failure to account for any differences to this ratio will result in a gearbox that does not match the application’s requirements.

• Motor HP and frame size The gearbox size and input option must be determined before calculating the service factor. Once the gearbox is sized, the required HP can be used to compute the actual service factor.

• Large HP motors generate heat that can adversely affect the reducer’s mechanical ratings. This reduced rating, based on the increased heat, is known as the Thermal Capacity of a reducer, and must be considered when using large motors.

• General shaft load The force, measured in pounds, that the output shaft is capable of sustaining is known as the Overhung Load rating. If the rating is less than the application’s requirements, the speed reducer will be damaged.

Ultimately, customers should size from the load to ensure they receive a cost-effective solution that fits the application’s needs.  The service factor, environment, ambient temperatures, shock load, output style, and hours of service are all important aspects of sizing. The more information provided about the application, the more accurate the sizing process.

Key gearbox types for power transmission applications 

There is a variety of different gearbox types most commonly used for mechanical power transmission applications, and it’s helpful to know what each are best at before making a decision for your specific needs. The most frequently used gearboxes for power transmission include:  

• Right-angle gearboxes: These compact and versatile gearboxes are perfect for equipment layouts that demand a 90-degree transmission of power. Depending on your torque and smoothness needs, you can choose between helical gearbox, bevel gear and planetary gearbox configurations.  

• Inline servo gearboxes: Known for the high degrees of precision and speed consistency they offer, these gearboxes are best-suited for motion-centric applications including automation and packaging lines.  

• Rack & Pinion systems: Because they convert rotary motion to linear motion, these are ideal for gantries or heavy-load positioning systems.  

• NEMA gearboxes: The food and beverage and pharmaceutical sectors depend on these because they are compatible with standard motor frames and offer full washdown capabilities for hygienic purposes.  

• Stainless steel systems: Also suitable for washdown applications, these also offer exceptional resistance to chemical exposure.  

Environmental & duty cycle considerations in gearbox selection 

Along with the application and torque requirements, it’s also important to think about how your gearboxes may be affected by environmental conditions and duty cycles within power transmission systems. Some necessary gearbox selection factors to consider include:  

• Ambient temperature: This can impact material expansion, lubrication lifecycles and the overall lifespan of your gearbox. Be sure the gearbox you choose is rated for extreme conditions if you work in outdoor or hot-process environments. 

• Shock and stop-start loading: Certain processes introduce sudden forces that require elevated service factors to prevent internal damages.  

• Contaminants and ingress protection: You should have IP-rated enclosures for applications involving dust, fluids and washdowns. Depending on the exposure level, you may need IP65+ or IP69K.  

• Mounting orientation: Choosing between vertical or horizontal orientation affects internal oil flow and may require specific design accommodations.  

• Duty cycle: Whether your gearbox needs to run continuously, intermittently or under variable load conditions determines the thermal capacity you need and the gearbox’s long-term suitability.  

Common Mistakes in Gearbox Selection 

• Oversizing for peace of mind: This common pitfall often leads to unnecessary costs, inefficient performance and integration challenges. 

• Underestimating operational demands: Selecting based on catalog specs alone without analyzing your duty cycle or real-world torque/load demands can result in early failure.  

• Disregarding environmental factors: Gearboxes exposed to washdowns, dust and/or temperature extremes must be made of appropriate materials with proper sales and IP ratings.  

• Assuming plug-and-play integration: It’s important to consider physical mounting requirements, shaft orientation and compatibility with the motor or automation system.  

• Choosing based on price: The total lifecycle cost including maintenance, downtime and replacement matters more than the sticker price.  

With the largest breadth of product, industry-leading warranty, and lightning-fast shipping times, STOBER is ready to configure your next solution. 

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