There is a debate in the servo gearbox industry over whether gearboxes should be benchmarked against rated input speed or max input speed. Apex Dynamics has been looking closely at both, and making sure customers know the difference when it comes to torque specifications.
Having always based its R&D testing and catalogue information on max. input speed, the global leader in servo gearbox technologies has announced it is switching to rated input speed, in order to benchmark according to the new industry standard. Apex Dynamics is also keen to make sure customers are aware of what the new standard means and that they understand the industry debate surrounding the two calculations.
Max input speed refers to the maximum speed a gearbox can reach on a temporary basis, while rated speed refers to the highest speed that gearboxes can reliably run at continuously. Some leading companies in the gearbox industry have been benchmarking according to rated input speed rather than max. input speed in their marketing documentation for a while. Calculations based on the new rated input speed standard generally result in higher torque ratings, as max input speed gives a much more critical loading to gears and results in an overall lower torque.
There are pros and cons to both approaches. Rated input speed gives a good indication of what the torque limits are, but customers need to pay more attention to gearbox selection, particularly if they need to run them at high speeds. Max input speed offers information about what a gearbox is capable of and demonstrates its full potential application. However, while most gearboxes go above nominal speed during a cycle, not all applications require gearboxes to run at max. speed.
Often customers are not aware of what they are looking at when it comes to the data provided and this can cause misunderstandings and confusion. New products benchmarked against rated input speed without context may look as though they have had significant improvements in torque compared with older products or competitors’ products that have been benchmarked against max input speed. It can also make small alterations to product ranges appear to be completely new high-performance products. Apex wants customers to be clear about what they are getting and so has taken the decision to switch its benchmarking for all newer products to rated input speed in order to provide greater clarity about the performance of its gearboxes.
Apex Dynamics’ engineers recently carried out extensive research examining the performance of its AF series of planetary gearboxes compared with its leading global competitors based on both rated and max. input speed. It found very favourable performance ratings, with Apex Dynamics easily outstripping many competitor products no matter which standard is used, and the picture is similar for other Apex planetary products.
Andrew Parsons, UK sales manager for Apex Dynamics, explains: “When it comes to comparing brochures with different benchmarking data for torque, it really is comparing apples and oranges. We have made the decision to bring our new product data in line with the new industry norms in order to meet customers’ expectations. However, we think it is important when people are comparing data that they are aware there are two ways in which it could be presented.
“For example, the rated torque of Apex’s AP110 ratio 5.5:1 product is 435 Nm, compared to 243 Nm for a leading competitor’s product, when measured according to rated input speed. If the same comparison is done using max input speed, then the Apex figure is 370 Nm, but the leading competitor figure is unpublished. Where the problem can arise is if a potential customer compares rated against max input speed without realising. If that happens, the customer has an incorrect picture about performance and cannot make an informed decision.”
Mike Gulliford, managing director of Apex Dynamics UK, adds: “We found most global companies are now benchmarking their gearboxes by rated input speed and, in a major global change to our product specs, we have made the decision to do the same in the best interests of our customers. In doing so we have carried out extensive research showing our products perform favourably against leading competitors’ no matter which standard is being used. And we will continue to innovate, pushing the limits of planetary gearbox performance.”