HOW DOES A CHAIRLIFT WORK?
BY, DEE DEE TOMATOS AND ANDY JAMESON
Wait your turn, lower the bar, quickly judge if the people next to you are friendly enough to converse with, and that’s it, nothing to it. The chair magically sends you to the top of your run. Easier than hiking, cheaper than a helicopter, and a lot more quiet than a snowmobile, it’s no wonder chairlifts are the most popular uphill people mover. But how do they work? Below we walk through the basic mechanics of the two most popular types of chairlifts: the classic fixed grip, and the high speed detachable. Most other lifts are variations of these two technologies. Special thanks to Chairlift.org for technical knowledge and pictures.
The Classic Fixed Grip
If you’re old enough to (legally) drink a beer, you’ve spent a good amount of time ridding the classic fixed grip chair. Save Magic was kind enough to supply us with some background on Magic Mountain’s 1971 Heron-Poma fixed grip double chair, which we’ve used as an example. We are going to really simplify the process for those who never think about what they are riding.
A chairlift is basically a looping steel cable with a large pulley at each end (the bullwheels). Carriers (the chairs) are hung from the cable and held in place with a mechanical grip. The grip functions similarly to a vice and is tightened around the cable to keep the chair from sliding back. A chair gradually slides back a bit each season, which is why lines are often painted on the cable. The paint mark provides the lift mechanic with a visual indicator of how far the chair has moved. Don’t worry if the paint mark is far away, chairs are often moved every few seasons to ensure even wear on the cable.
Positive Jaw Grip The Red Chair’s Summit Bullwheel
A series of towers form the line and keep the cable from dropping to the ground below. Towers are installed with either a crane or a helicopter depending on the budget, terrain, and weather. The towers are topped with cross-arms that hold sets of wheels called sheaves. The cable can go either above or below the sheave assemblies. On the vast majority of towers the cable travels over the sheaves, exceptions are when the lift is about to climb a steeper section, traveling under adds tension to the cable allowing it to achieve a more drastic angle.
Cable Traveling Under Sheaves Helicopter Installing a Tower
So what makes the bullwheel turn? Today most lifts are driven by electric motors but have secondary diesel backup drives. Mad River’s single chair ran exclusively on diesel until 2007, when it was completely refurbished. Today’s electric motors are cleaner and less expensive than their diesel ancestors. Chances are if you hear an engine running, the lift is operating on its back-up diesel for one reason or another. The engine can be located at either the summit or the base of the lift depending on the engineer’s recommendations.
What keeps the cable from getting too loose? On older lifts a large counter weight provides tension to one of the bullwheels, ensuring that the cable remains taught. Newer lifts use hydraulic tensioning (giant shock absorbers) for easier adjustability and improved ride quality.
Red’s Counter Weight Sits on Railroad Tracks Modern Hydraulic Cable Tension System
Magic’s Black Chair has a highly visible summit counterweight.
The High-Speed Detachable
We all know that high-speed detachable chairs are much faster, and as the name implies, the chair “detaches” from the cable. In fact, high-speed chairs are 2.4x the speed of their fixed grip brethren. These detachable chairs typically travel at speeds of 1,200 feet per minute (14 mph, 22 km/h, 6 m/s) versus a typical fix-grip speed of 500 ft/min (6 mph, 9 km/h, 2.5 m/s). Theoretically, a fixed grip chair could move just as quickly; however, getting off and on a chair traveling 14mph could be very painfull and embarasing.
High-speed detachables work in a very similar manner to fixed grip chairs, with one key exception. The high-speed detachable has a grip mechanism that allows the chair to release from the cable at the loading and unloading stations. The cable continues to run at the faster speed while passengers load and unload at easy slow speeds reducing the number of stops the lift must take.
To detach or not to detach? Traditionalists favor the fixed grip for many reasons. Fixed grip lifts are well suited to service tougher terrain where the capacity of a high speed lift is not necessary. They provide more time for recovery and plenty of time to chat with your neighboor, enjoy a beverage or whatever else suits your fancy. Most importantly, powder is not tracked out as quickly.
In the West detachables are a treat as there is much more acreage over which to dispense skiers. Resort designers in the East must carefully consider where to place detachables and and how they affect skier traffic. Detachables also help get new skiers using lifts quicker as loading and unloading is almost at a standstill.