Hanging by a thread?

For those of you who are familiar with skiing, there are two types of chairlifts. The older design, called “fixed grip” and the modern, much faster system known as “detachable.” We're going to talk about the former and in particular a singular, very odd model that still operates at The Canyons resort. First, let me explain what a “fixed grip” attachment is. It's a clam design that literally grips the cable by means of a strong bolt, enabling it to hold a chair with its passengers and carry them up the hill. It's simple, safe and it works.

At The Canyons, where I ski most of the time, there is rickety chairlift from yesteryear called Golden Eagle. It serves a beautiful bowl, but is painfully slow and I take it once a day, if at all. The interesting aspect of that lift is while the chair is attached to the cable, like other fixed grip lift, its attachment is quite different. There's no clam and instead, a tongue that extend from the top of frame of each chair is directly inserted into the strands of the cable in a streamlined manner. From a mechanical standpoint, this doesn't seem as elegant as it appears since around most attachments frayed cable or even a cable bulge is visible. Since I'm naturally fearless, I don't care much about the safety of the system, but I don't think this is the best way to hold a chair to a cable. Could some expert voice his opinion on the matter.

Alain Lazard's Answer
The chair in question is a Riblet; the company closed down in 2003. There are still quite a few around; from the three that originally were at The Canyons, only the Golden Eagle chair survives today. Riblet built some 500 lifts. The particularities of the Riblet chair are their grips, which are called insert clips. It is a very ingenious device and it is very safe too. Since a picture is worth a thousand words, You'll see a sketch below showing the detail of the clip.

The only accident I ever heard about happened at Wildcat, NH, a long time ago. I have no details about it and it might not have been caused by the insert clip.
One big benefit of the clip is that it provides a very smooth ride over the sheave trains, particularly under the compression sheaves, something that traditional clam/jaw grips cannot match. The drawback is that the clip cannot be visually inspected at it is the case with other grips. Also, the code required to move the grip every 2 years or 2,000 hours, whichever comes first. This is the same with traditional grips.


This is a labor-intensive job and a special tool has been developed: The Riblet "Grip Detensioner" . It's showed on a second picture representing the tool in action. You can see the cable in the middle with the strands separated, which allows the insertion of the clip. Also, the fiber or plastic core of the wire rope has to be cut where the clip is inserted. When the clip is moved to another location of the cable, a plastic part has to be placed into the cable to replace the missing piece of the core. Finally, the Riblet clip cannot be placed on the spliced section of the rope.


You've correctly noted on your blog that a few wires are broken next to the clip. This is not a problem because chairlift wire ropes have a safety factor of five. This means that 80% of the wire would have to be broken within a few feet for the cable to fail. The broken wires are likely the result of the increased stress and bending of the cable near the clip. It shows how important the regular displacement of the chair is on the cable. Proper maintenance is the key to keep a Riblet and all other chairlifts running smoothly and safely.