Grease has to work in some pretty severe environments, and thosethat lubricate mountain transportation can face some of the mostdemanding conditions of all, like those brave souls who maintain them.Not convinced? Trevor Gauntlett says read on.

For a few months a year, the ski lift in the popular resort of Mount Rigi in the Swiss Alps is all but frozen. Rather than being unused, it operates in full swing, pulling thousands of skiers up the slopes every day. What stops it from breaking down is grease that can stand the extreme conditions up a snow-covered mountain.

But keeping mechanized transport on the mountains from freezing is not a modern problem. In the late 19th century, tourism emerged as a significant industry in mountainous regions with the invention of a means to transport people quickly and relatively cheaply to the upper slopes. Suddenly, mountain railways made rapid ascents that previously had taken many hours from home or hotel.

The two railways that began this revolution are now around 150 years old. Although incomplete, the Mount Washington Cog Railway in New Hampshire, U.S., carried its first fare-paying passengers in 1868. In Switzerland, the Vitznau-Rigi-Bahn on Mount Rigi near Lucerne opened in 1871. Both are still running and operate on similar systems patented by Sylvester Marsh in the U.S. and Niklaus Riggenbach in France.

Various types of rack railway followed, with Alpine countries in Europe particularly active. At first, these railways only operated in the summer months. But the growth in popularity of winter sports soon had railway owners seeking ways of operating all year round.

A rack railway involves a train with an inner pinion that engages with a central track, or rack, between a conventional track and wheels. The rack can have horizontal rungs like a ladder or vertical teeth. The rack and pinion transmit motion up the incline and braking on the way down. The pinion gears teeth always interact with the same side of each tooth or rung of the rack, so the lubrication challenges are the same no matter what the design.

Suspension Technology

Early in the 20th century, passenger-carrying aerial cable cars also began to appear on mountainsides and, upon the invention of the first ski lift, or chair lift, the technology of mountain transport begat a brand-new sport: Alpine skiing.

Cableways vary in their modes of operation, but many of the lubrication requirements are generic. A cable draws the cars, or gondolas, up the mountain, passing over a series of guide wheels at intermediate towers and looped around two large rotating bullwheels at either end.

The upper bullwheel provides the propulsion and the lower one provides tensioning. There are subtle differences between cableways, which are driven by desired capacity. In the simplest form, a single cable supports the passenger cabins and draws them up the mountain. For higher capacity systems, the cabin is supported by one or two cables that are independent of the propelling cable.

In most cases, the cabin is suspended below the support and drive cables, but with the CabriO cable car at Mount Stanserhorn in Switzerland, the support cables pass along the sides of each car. All running wheels – whether carrying a cable over a tower or on the cabin supports running along the support cables – contain bearings, and there are usually pivot bearings or rocker pins supporting the cabins and the drive systems are usually geared.

Common with all cable cars, the entire assembly is subject to vibrational shocks as each running wheel travels along the tower guides. The main bearing rotates about 40 degrees as the car passes over the tower. When travelling down, heavily loaded cable cars may rock back and forth for several oscillations, placing stresses not only on the main bearing of the cab, but also on the guide wheels supporting the propulsion cables and – via the cables – the gears and main bearing of the bullwheel.

There are a small number of funicular railways in mountainous environments, where two rail cars are connected by a cable, which draws one up a track while the other travels down. These are usually shorter than rack railways and cable cars, so do not face some of the operational challenges that the other two technologies face.

Misty Mountain Top

The principal challenge for maintenance engineers is usually the location. Everything is focused on ensuring that the system does not break down mid-journey, leaving passengers stranded on board in the cold for extended periods. Maintenance tasks at intermediate towers of a cableway require staff to work in extremely exposed environments, making simple lubricant replenishment a hazardous activity. Lubricants, especially greases, have to be easily applicable by staff in cold, windy and wet locations by brush, spatula or grease gun or by automated systems in sub-zero temperatures and where moving parts could become impeded by snow or ice.

Topography plays a significant role in the stresses placed on moving parts and lubricants. As well as the seasonal variations, a mountain railway may well experience significant temperature and humidity variations during not only one day but also one trip.

In summer, the ambient temperature at the low stations might be in the low to mid-20s Celsius with low humidity, while the mountain station (usually reached less than an hour later) is well below freezing and may be covered in thick fog or cloud, meaning that humidity is close to 100 percent. Many cable cars make this transition 20 or more times per day.

Most mountain railways also operate in environmentally sensitive areas, so total and partial-loss lubricants are constrained to have significant biodegradability, even at low temperatures, as well as low toxicity.

According to Antonino Martello, product application specialist for Europe and Africa with Shell, the main environmental causes of failure in ski-lift equipment are due to temperature, temperature variation and water contamination. These are in addition to the usual issues any lubricant engineer observes: use of the wrong lubricant, inconsistent lubrication intervals, grease forced out of the load zone, poor installation practices, abrasion due to dust and dirt attracted to exposed grease and oxidation.

Alpine Formulation

Low temperature is a big factor in the winter, and the standard, mineral oil-based product will not be applicable. Paraffinic oil has a pour point around minus 10 degrees Celsius, so at a temperature significantly lower than this it will be like a wax candle, Martello explained to LubesnGreases.

This can lead to premature wear of pivoting bearings, rocker pins or suspension bearings. The upper bullwheels that provide propulsion on mountain cableways have to operate for up to 10 hours per day during skiing season, usually in sub-zero temperatures and high humidity. This places stresses on the bearing greases and the gear lubricants for the drive systems.

While pour point depressants can mitigate some of the issues with mineral oil products, they are not a panacea, Martello warned.

One often ignored point … is that PPDs only slow down the rate of crystallization, they dont stop it completely. Therefore, if an oil spends a significant time at low temperature below the base oil pour point it will still crystallize [become wax] even if it has a standard, short-term pour point that is lower than the temperature its experiencing.

Naphthenic oil is one possible solution, as it has no crystallization pour point. However, Martello warns that, since its viscosity index is low, it becomes very viscous at low temperature, increasing the energy you need to run the machine. The only way to avoid this low-temperature problem is to use synthetic or semi-synthetic oils and greases.

Water from condensation and precipitation can penetrate housings, promoting corrosion and wear.

Attention to good sealing might help [but] the lubricants will have to be able to cope with water. This might limit, for example, the use of certain types of oils like for example polyglycols [which can form emulsions] for worm gears. It would also affect the choice of greases used, preferring thickeners with very good water resistance and anti-corrosive proprieties.

The wind can play its part, as it is often stronger on the upper slopes than at ground level. This can cause shock loads on equipment in cable cars and even trains. It would also mean that the lubricants in open applications (cables and gears for example) could be disturbed and even blown away.

They need to stick to the surfaces better than they do in calmer locations, said Martello, highlighting the use of tackifiers. They also usually need good EP additives to prevent impact load due to sudden gusts of wind on the equipment.

The shape of the mountain dictates where railway has to be built, explained Martello. Mountain railways are often narrow gauge (80 centimeters to 100 cm between tracks, rather than standard gauge 4 foot 8 1/2 inches, or 143.5 cm), so they are likely to have many, much sharper curves than normal, he said This could promote rail side and wheel flange wear, although the low speed will help a little in reducing this.

Ski Pole Position

The optimal lubricants for rack railways and cableways require excellent flow properties at sub-zero temperatures that do not become high flow at 20 to 30 C. They must be tacky, withstand water washout, have high corrosion resistance and demonstrate excellent extreme pressure performance, especially under shock loads. And they should be simple to apply, biodegradable and – probably the customers No. 1 requirement – universal and cheap. Simple. Now wheres my beaker, stirrer and thermals?