Behind the Scenes of the Jackson Hole Tram

The tram's motor room under the bottom dock houses electric motors, a large generator, braking systems and evacuation drives.
A motor room under the bottom dock houses electric motors, two generators, three braking systems and two evacuation drives.

The $31 million Jackson Hole Aerial Tram is the most expensive lift ever built at a US ski area.  Constructed by Garaventa over 20 months, the new tram opened to great fanfare on December 20, 2008.  It can move a hundred people 4,083 vertical feet in under nine minutes.  Compared with a detachable lift, the tram is a relatively simple machine built on a massive scale.

The view from carriage level just above tower 2.
The view from carriage level just above tower 2.

Like most jig-back aerial tramways, there are four track ropes and a single haul rope that that drives both cabins.  All five wire ropes were manufactured by Fatzer in Switzerland.  Five towers support the line; towers 1 and 2 are the tallest and furthest apart.  Two CWA Kronos cabins move 650 passengers per hour per direction at a maximum speed of 10 m/s.  Slope length is 12,463 feet.

Track cables are wrapped around bollards at each end.
Track cables are wrapped around bollards at each station.  Every 12 years or so, the track cables will be slipped downhill to move the wear points on the towers.

Because the new, larger tram had to fit into the same footprint as the old tram building in Teton Village, a moving center loading platform takes the place of the upbound car during each trip.  The tram’s gauge gradually widens between towers 1 and 2.  At the top terminal, Garaventa designed four hydraulic gates that drop down and lock the cars into place after they dock.  This prevents cabins from swinging their way into the top dock on windy days.

The center loading platform moves during each trip to make way for the arriving car.
The center loading platform moves during each trip to make way for the arriving car.
There are four gates at the top dock that lower automatically once a trip completes.
There are four hydraulic gates at the top dock that lower automatically once a trip completes.

The tram is powered by twin 1,000 horsepower ABB AC electric motors at the bottom terminal.  The motors are coupled to a Flender gearbox and then the drive bullwheel, which the haul rope wraps around twice.  A 2,400 HP Cummins genset in the motor room and a smaller generator at the summit provide power to run the system normally during a power failure.  If the electric motor(s) fail, a diesel hydrostatic evacuation drive can be coupled to the drive bullwheel.  Another hydrostat with a different coupling system forms a fourth backup.  Each evacuation drive has a remote control that can be brought outside to operate the tram with a view of the line.  A third generator can power tram control in case the grid and primary generator both fail.  Even if none of the four propulsion systems work, each car also has a trained operator and equipment for a rope evacuation.  The original tram had to be rope evacuated twice, most recently in 1996.

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Twin electric motors form the prime mover.
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The gearbox is located between the electric motors and drive sheave.
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Evacuation drive 1 and coupling with evacuation drive 2 to the left.

The two service brakes and an emergency brake are each tested daily.  Unlike the original, the new tram has no track rope brakes on the carriages.  The haul rope is tensioned by a 220,000 pound counterweight in a pit underneath the top terminal.  Twenty-six slack carriers keep the track ropes and haul rope together over the longer spans from towers 1 through 4.  Every 400-500 hours, cabins 1 and 2 are re-positioned on the haul rope by 10 meters so that the wear points change.

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Service brake #1
220,000 lb. concrete counterweight suspended under the top terminal.
The 220,000 lb. concrete block suspended in a pit under the top terminal.

The tram’s electronic controls were designed by Frey AG of Switzerland with components from Siemens and Pilz.  There is no dedicated communications line; rather signals are transmitted through the haul rope including voice communication between the cars and stations.  The entire haul rope is supervised, meaning that if it hits metal at any point along its five mile length, the tram will stop.

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Siemens control console at the bottom.  The pod on the right controls travel speed.
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A Windows-based computer shows the positions of each car, wind history and fault logs.

The tramway can be operated directly from a console in tram control or remotely by operators in each car.  Tram operators have touch screen controls with the status of the other car and important information.  Each tower has an anemometer which transmits wind speed and direction to the cars and tram control.  During normal operation, acceleration and deceleration are handled automatically.  Tram operators start each trip and always have the authority to change speed for wind or wildlife.

Operator controls in Car 1.
Operator controls in Car 1.
Frey control cabinet located in the top terminal.  There is a larger cabinet in tram control and more in the motor room.
Frey control cabinet located in the top terminal. There is a larger cabinet in tram control and multiple cabinets in the motor room.

Each car has two batteries which power automatic doors, controls, lights and  the audio system with satellite radio, USB and Bluetooth.  The batteries charge whenever the cars are docked.

There are 16 wheels on each carriage.  The silver box provides charge to the two batteries in each car when docked.
There are 16 wheels and four on each car’s carriage. The silver box provides charge to the batteries in each car when docked.

The tram is staffed with four full-time mechanics and around a dozen operators each season.  It has accumulated almost 11,700 hours of run time in 67,000 trips to date. Hopefully it will last at least as long as the original tram, which ran from 1966 to 2006.  All five ropes are still original, with the haul rope having been spliced three times to date. The haul rope is expected to last about 15 years while the track ropes will last much longer.

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