Popular Mechanics (South Africa)
Cableway turns 90: A closer look at the history and genius of Table Mountain’s aerial gateway.
and still swinging
Table Mountain has an almost magnetic appeal, drawing people in and compelling them to reach its summit. But getting to the top was not always the effortless trip it is today.
IMAGINE BEING suspended high above the Cape Peninsula in an open wooden box relying solely on a primitive temporary ropeway system to transport building materials and workmen to the summit of Table Mountain, all while battling a brutal south-easterly wind. In the late 1920s, a group of skilled engineers and builders experienced the thrill (and at times, terror) of being suspended in mid-air while performing a feat of engineering that would result in the construction of one of the world’s most famous tourist attractions, the Table Mountain Aerial Cableway.
Ninety years have passed since those brave men played a key role in catapulting Cape Town on to the global tourist stage. Thankfully, modern technology meant I did not have to muster the same courage during my recent ascent to the top of the mountain, and instead could stand comfortably enjoying the gorgeous 360° views of the peninsula as the floor rotated beneath my feet.
I’d made the trip to the cableway to join in on the 90th birthday celebrations. First opened to the public on 4 October 1929, the cableway has seen more than 28 million people visit it during its existence. Having commenced on 4 October 2019, a year-long celebration is planned for the old girl’s special birthday.
If you’re afraid of heights, then floating in the air does give a good sense of one’s mortality, but Operational Manager Mike Williams is quick to point out that in nine decades there has never been an accident at the cableway.
Each cabin is suspended from the track cables via a carriage and hanger. The carriages each have 24 wheels, and are designed to carry 65 passengers and one cabin master for a total payload of 5.2 tons. ‘The hanger and carriage swing forwards, backwards and sideways via special shafts, and are equipped with dampers to stop excessive swing,’ explains Mike. ‘This swing ensures perfect contact between the wheels and track cables, similar to a car’s suspension, allowing constant contact between tyres and road.’
Ascending the 704 m from the lower station to the upper station at the summit is a breeze, at just under five minutes of travel time. Once you reach the top, you’re standing a little more than 1 000 m above sea level with the perfect window to the natural world in front of you.
At the lower station, each cabin has a docking bay, while they share a bay at the top station. This is made possible via a moving platform and docking rails at the upper station.
Holding all the weight requires some serious lifting power and the cables used on the cableway system are no slouches. The cabins are suspended from the track cables, while the heel and haul cables pull the cabins up and down. The track cables have an impressive breaking strength of 238 tons while the heel and haul cables have a breaking strength of 75 tons. These are attached to the cabins via a special socket arrangement.
The cableway shares its South African ingenuity with Swiss engineering. ‘The technicians who assemble the socket have been trained and certified in
Switzerland. The cables are manufactured by FATZER AG, a Swiss company that specialises in this type of equipment,’ says Mike.
Coming in at 1 200 m in length, the heel and haul cables weigh a whopping 10 tons combined. Mike explains that the cables are made from high-tensile steel that is galvanised for corrosion protection, which also eliminates the need for oil.
‘The cable has a fibre core, which allows the necessary flexibility.
The wires are wound in a pattern known as Lang’s Lay – where the strands and final cable are wound in the same direction. This gives it greater flexibility, contact area and resistance to wear than with a regular lay steel wire rope used for cranes and winches.’
The annual maintenance shutdown period varies from year to year depending on what needs to be done. The general period is two weeks and can stretch as long as five weeks when major maintenance needs to take place. The maintenance team completed 400 hours of work during the last maintenance period, which included replacing the heel and haul cables, testing and replacing the load-bearing components on the cabins, doing a mechanical overhaul of the rotating floors and cabin-door mechanisms, and servicing the hydraulicand brake systems.
The engineering and ingenuity behind the cableway system are an intricate masterpiece of elegant simplicity, designed to keep the cable cars moving at optimal speed with safety at the forefront. The modern advancements are a far cry from what was first unveiled to the public nearly a century ago.
THE FIRST CABLE CAR COULD CARRY 19 PASSENGERS.
Originally designed by Norwegian engineer Trygve Stromsoe in 1926, the idea for the cableway was picked up by Stromsoe after plans to build a cable railway system were abandoned following the outbreak of the First World War. He created a scaled model and presented it to investor Sir Alfred Hennessy, who in turn roped in fellow investors Sir David Graaff and Sir Ernest Oppenheimer, and they formed the Table Mountain Aerial Cableway Company (TMACC), which is still in operation today.
Taking two years to be built, the cableway had an upper- and lower station, and a tea room. The first cable car was made using steel and wood, and could carry up to 19 passengers and one conductor, reaching the summit around 10 minutes later. The cost of construction totalled £60 000 (about R1.1 million).
Cape Town-based architecture firm Walgate & Ellsworth were enlisted to design the cableway and it was constructed by Adolf Bleichert from Germany. During the 90th birthday celebration, Helmut Bleichert visited the cableway to represent the Bleichert family who has been involved with the design and construction of many cableway systems all over the world.
The original design team had an immense challenge on their hands – how to deal with the roaring winds that swirled and blew diagonally across the cable wires causing the cabins to swing. The answer was to build the cable cars with them lying in-line to combat the high winds.
This got me wondering how this is achieved today with the technological advancements that have been made over the years. Turns out the mechanical team had to think out of the box to come up with a workable solution. By fitting each cabin with 3 000 litre water tanks, which carry fresh water for the public to the upper station, they also serve as substantial ballast that resists strong winds. Killing two birds with one stone seems to be a good engineering approach to me, and this bit of ingenuity enables the cable car to operate in winds of up to 40 km/h depending on the direction. If the wind is blowing directly down the cables, the cabins can operate in stronger winds, up to 60 km/h.
‘The only time the cableway closes is due to excessively strong winds,’ says Mike, adding that, in the summer, it’s the notorious southeaster that causes most of the mischief, while in the winter, the northwester is the biggest problem. ‘Both winds blow diagonally across the cables, and when they’re too strong they cause the cable cars to swing too much.’
In 1997, the cableway received its largest upgrade to date when it was closed for nine months.
This is when the rotating floor and resulting 360° views were introduced to the cabins, at a cost of R90 million.
Other upgrades to the cableway in 1958, 1965 and 1974 included the introduction of sophisticated safety features, a diesel-powered generator and an automatic braking system. Radio communication was also installed so that the upper and lower stations could remain in contact with each other, and the load capacity increased from 23 to 28 passengers, and finally 65 in total.
The cableway is currently powered by a 540 kW alternating current induction motor, which was installed in 2013 to replace the previous direct current technology. ‘The AC motor’s speed is controlled by four variable frequency drives,’ explains Mike. ‘The electrical control circuit monitors many conditions on the system to ensure the safety of the visitors and equipment. During electricity outages, a Volvo engine hydraulic system can also be used to power the cableway. A second back-up system, a Deutz engine driving a separate hydraulic system, yields triple redundancy.’
Upon reflection, my automated mountain-climbing excursion had brought about new-found respect for the workers who risked their lives to bring us something that’s truly special. In her 90th year, I think it’s only fitting that we ascend Cape Town’s famed mountain as often as we can, soaking up not only the breathtaking views, but also to pay homage to the foresight the cableway’s founding fathers had when they designed a true engineering masterclass.