Photo by Tom Ross
R.J. Knight, left, of Bowling Green, Mo., supervises in December 2007 as a crew weaves wire strands into the core of the Steamboat gondola haul rope. Their work splicing what was then a new gondola rope is unrelated to vibration issues that led the ski area to install a new rope this month.
Thursday, October 29, 2009
Steamboat Springs Steamboat Ski Area executive Doug Allen was hoping for an end to the winds that battered the base of Mount Werner on Wednesday so crews could get back to the chore of making the Steamboat gondola ready for opening day Nov. 25.
For the second time in two years, contractors are hustling to install a new 60-ton gondola haul rope at the ski area.
"They just finished splicing it," Allen said. "It arrived in Galveston (from Switzerland) on Oct. 4 and here on Oct. 15. We're waiting for the wind to stop" so the 3.4-mile cable can be strung from the final two towers and tensioned. Weather permitting, the work could be completed today.
Allen, vice president of mountain operations for Steamboat Ski and Resort Corp., did not expect to supervise installation of a new gondola rope for another 15 years or more. Crews at the ski area went through the process in November and December 2007 when they replaced the original rope after 20 years of service.
However, Allen said, problems with the new rope were apparent from the beginning.
"We've had vibration issues ever since it was replaced," he said. "The passengers in the cabins would not notice these vibrations because they were not transmitted into the cabins but into the tower and terminal machinery. Besides, each cabin is equipped with a spring-dampened suspension that is designed to isolate the passenger from strand-induced vibrations."
The vibrations were not creating safety issues, Allen added. The Colorado Tramway Passenger Safety Board has been kept apprised of the situation but has not inspected the rope that was installed in 2007, he said.
After two years of consultation with independent experts and negotiations with the manufacturer, Allen said, it has been determined that a subtle variation in the shape of the 2007 braided steel rope contributed to the vibration problems.
"We didn't see rapid sheave liner wear, but long term, you could expect it would add to fatigue," Allen said. "We need to take care of this wonderful lift."
The term sheave (pronounced 'shiv') refers to pairs of wheels on the gondola towers that the haul rope and gondola cars travel over.
The rope was manufactured by the Fatzer AG in Romanshorn, Switzerland. It is really six steel ropes in one. The haul rope comprises six strands of 37 wires wound in a tight spiral around a plastic core.
If a person visualized the peaks and valleys created by the six strands twisted around the core, and the width of the valleys, that pattern comprises the lay of the rope, Allen said.
In consultation with an independent gondola-rope expert in Zurich and a Boulder engineer who worked on the design of the Steamboat gondola, it was concluded that the difference between the lay of the 2007 rope and the original rope accounted for the undesirable vibration.
"The rope isn't a cylinder, so there's some vibration," Allen said.
The variation in the lay of the 2007 rope didn't allow the pairs of sheaves, or wheels, at each gondola tower to absorb the energy that can cause vibration.
When functioning properly, Allen said, the pairs of sheaves alternate in an up-and-down motion to absorb the shock of passing gondola cars.
"The lay of the (2007) rope was such that it pushed the sheaves down simultaneously," Allen said. "All that energy was going right into the axle."
Allen noted that to the untrained eye, the new gondola haul rope doesn't appear that different from the 2007 rope. He was eagerly awaiting a change in the weather that would allow the success of the new rope to be confirmed.
"We could have the gondola running" today, Allen said.
Fatzer AG, which also manufactured multiple ropes for Intrawest's new Peak 2 Peak gondola in Whistler Blackcomb, B.C., reached a settlement with Steamboat about the replacement of the haul rope here, Allen said.