Aerial Technologies, Lesson 3: BDG - The Gondola Project (original) (raw)

Note: This post was updated on May 30, 2011. These revisions reflect the most current and available knowledge we have but do not guarantee the validity of the claims made. As always, it’s best to use the information contained herein as a guide.

Bicable Detachable Gondolas (BDG) are a less common form of gondola than Monocables (MDG). Originally, BDGs were a superior technology to the MDG, but advancements in MDG technology have rendered the BDG obsolete in all but the most specific of situations.

The difference between MDG and BDG is straightforward. Whereas Monocable systems are both propelled and suspended by the same cable, Bicable systems provide those two separate functions with two separate cables.

One cable is stationary and doesn’t move. It’s this cable that gives the gondola support. This cable acts much like a rail would for a traditional transit vehicle. A wheeled bogey attached to the gripping mechanism of the gondola runs along this cable much as train’s wheels would run along rails.

The second cable is not stationary. It runs in a loop and is powered by bullwheels at the terminals. The gondola grips attach and detach from this moving cable, thereby providing propulsion.

BDG Stats:

• Maximum Speed: 27 km/hr (revised upwards from 24 km/hr).
• Maximum Capacity: ~4,000 pphpd (revised downwards from 6,000 pphpd).
• Vehicle Capacity: Up to 17.
• Wind Stability: Operational in winds up to 70 km/hr.
• Maximum Span Between Towers: Up to 1,000 meters (conditional on capacity).
• Cost: $15 – 25 million (US) / kilometre. (estimate).

While Bicable systems are more expensive than Monocable systems, this added cost is not really justified. The only two real advantages of a Bicable as compared to an MDG are as follows:

• Bicables can travel at greater maximum speeds than the MDG. This speed premium, however, amounts to only 5.4 km/hr.
• Longer spans without need of intermediary stations. Like above, this premium is modest. Whereas an MDG can span 700 meters without need of an intermediary tower, the BDG can span 1,000 meters.

These modest advantages are offset by the following:

• Higher capital cost
• Larger station size
• Larger tower profile.

Because of their higher capital costs as compared to an MDG, with little real advantage, Bicables are increasingly becoming an abandoned technology in the cable transit world.

The Teleferico Madrid is an old but strong example of bicable technology.

Proceed to Aerial Technologies, Lesson 4: Funitels

Return to Aerial Technologies, Lesson 2: MDG

Creative Commons images by jaaron and Shadowgate.