Friction drive design for ultimate reliability

The world of rotary test stands is full of R+W couplings – playing their part in achieving smooth running, precision, and maximum reliability. We would like to share with you one recent example of our work in this field: a high torque disc coupling with friction drive principle for the aerospace testing industry. 

Made with performance and durability in mind

Testing transmissions used in aerospace applications is serious business. Production engineers need to guarantee performance across a wide range of extreme loading conditions – and failure is not an option. 

Recently R+W was involved in developing a high torque line shaft coupling to flange mount between two custom gearboxes and provide mechanical power to multiple different rotational axes for various test articles. These individual branch axes, each of which is equipped with its own TORQSET-ST series safety coupling to protect the high value test articles from overload, are most efficiently driven in this way. The different combinations of mechanical power which could be summoned require that one single high torque coupling handle the brunt of the work. In order to help guarantee smooth and consistent transmission the individual disc pack bolts are fitted with multi-jack tensioning nuts, which put the disc packs under the extreme pressure necessary to drive in pure face friction, without placing the assembly bolts under a shear load.
The result is true fatigue resistance!

Technical specifications for the coupling:

- Continuous operating torque: 35,000 Nm
- Rotational speed: 2,818 rpm
- Overall length: 1,558 mm
- Customer-designed flange each end
- Multi-jack bolt tensioners for extreme bolting

Over time and through various starts, stops, shock, and vibratory loads, traditional disc pack assembly bolts can become fatigued when they are driven in shear.

One of the favorite principles at R+W is the possibility of eliminating the fatigue stress placed on these bolts by driving the disc packs through pure face friction, where sufficient pressure is applied to completely prevent micro movements and shifting around the assembly hardware. 

For larger coupling sizes the associated bolt tightening torque can be cumbersome as the requisite level can reach into the thousands of Nm. A great alternative in this case was to fit the M42 assembly bolts with multi-jack bolt tensioners, which allow the installer to create the same tension through tightening multiple smaller screws against the nut flange that would be created by applying a very large torque directly to the bolt. 

A solution to suit engineers and installers alike!