The freewheels of RINGSPANN GmbH in Bad Homburg are used worldwide in the drive systems of ships, harbor cranes and in hydro, offshore and mining engineering systems, among other things. Specifically tailored to the strict environmental requirements in these application areas near to seawater and groundwater, the company now supplies all freewheel series with biodegradable lubricants at the customer's request. This should give design engineers even more leeway when it comes to realizing sustainable drive, running and hoisting gear.

Comprehensive test series to improve the ecological footprint

Minimizing the ecological footprint of technical systems and improving the life cycle assessments of complex drive systems: This has long been one of the requirements that designers and development engineers have to keep in mind when realizing competitive drives, running gears and hoists. In particular in shipbuilding, in the manufacture of harbor cranes, as well as in offshore, hydro and mining technology, the use of environmentally friendly and sustainable drive units is becoming increasingly important. RINGSPANN has therefore conducted extensive test series in recent months, focusing on the use of biocompatible lubricants for freewheels. The result is now clear: with immediate effect, the company is able to provide its customers with any freewheel type from its one-stop shop that goes beyond the standard design and is also available as a variant with a biodegradable lubricant. “This allows us to significantly expand the leeway of designers of drive trains with sea and groundwater contact – regardless of whether they use our freewheels for feed or overhaul functions or as backstops,” says Manuel Assmann, freewheel specialist at RINGSPANN.

Same price for the same performance

It is noteworthy that RINGSPANN freewheels with environmentally friendly lubricants are absolutely identical in construction to conventionally lubricated designs, that they have the same performance and that they are no more expensive than standard types. “Since all parameters remain identical except for the use of biocompatible lubricants, a straightforward 1:1 replacement of the freewheel clutches can also be performed during re-engineering, retrofitting or maintenance – without compromising on performance and with full cost transparency,” Manuel Assmann emphasizes.

Long-term test as a basis

To arrive at this result, the freewheel experts at RINGSPANN tested various biolubricants in a specially constructed test stand and compared their performance data with those of conventional oils and greases. To do so, several ball bearing and sealed sprag complete freewheels from the globally used series FB/FBE were filled in different ways and subjected to an endurance test. It is important to know that in the freewheeling direction, the inner ring of these freewheels can turn relative to the outer ring. In the opposite direction, however, the inner ring forms a force-locked connection with the outer ring through the clamping elements. This results in high radial forces between the raceways and clamping elements – and the lubricants. Subjected to a nominal torque of 200 newton metres, the complete freewheels had to permanently manage a switching frequency of 4.5 strokes per second on RINGSPANN's test stand. “In this typical scenario, the wheat was quickly separated from the chaff and we were able to clearly see which biocompatible lubricants met our quality standards”, reports Manuel Assmann.

“Contemporary alternative”

With the option of providing all free-wheel clutches in its extensive portfolio with biodegradable lubricants with immediate effect, RINGSPANN is making a valuable contribution to the implementation of the sustainability concepts that are being pursued in many areas of drive technology. As mentioned, in addition to designers in boat and yacht building and crane construction, manufacturers of drive systems for hydroelectric power plants, offshore and mining technology should particularly benefit from this. Furthermore, RINGSPANN freewheels with environmentally friendly lubricants should also prove to be the ideal solution for the realization of marine and submarine facilities - such as tidal power plants or lock systems. “Wherever drive trains can come into contact with seawater or groundwater and legislators prohibit or restrict the use of conventional lubricants, our biocompatible freewheel technology is a contemporary alternative in the sense of sustainability,” says Manuel Assmann. The only question that remains is why the new lubricants are only described as an “alternative in terms of sustainability”, instead of using the somewhat forgotten adjective “without alternative” – thanks to the significant progress that has been made?

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