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Eskimo Lift Destruction

Performed on June 18-19 in 1990 at the Winter Park Ski Resort in Colorado, W.P.R.A & Jenlynn Inc. performed several test on a 1963 Riblet center pole fixed grip double chair to see what would happen if any of the tests performed would happen in a real life scenario.

For more information about the Eskimo lift destruction test, you can order the SAM Magazine issue of September of 1990 (SAMinfo.com) and/or check out the Eskimo lift destruction video which is available on NSAA website (NSAA.org) for $500. If $500 is too much for you, there are some libraries in the United States and maybe Canada that actually have this video which you can check out by going to your local library and ordering it that way.

Tests Performed:

• Brakes
• Rollback
• Oily Rope
• Tree on Line
• Fire
• Tower Pull

Day One:
The first set of tests that were performed were those concerning the lift's braking system. The service, emergency and traction rope brakes had already been torqued tested to the standard prescribed values before the test was started. The chairlift was loaded with concrete discs that weigh 57 pounds each and were placed equally on 72 of the 155 chairs to bring the total weight of 29,000 pounds. The weight represented 110 percent of the lift's full uphill design load. When the first brake test started, both the service and emergency brakes were applied individually with the lift traveling in a reverse direction with a line speed that reached a maximum speed of 550 feet per minute (FPM), 50 feet faster than its designed speed.

When the lift was operating in reverse at a speed of 400 FPM, it failed to stop when the service brake was applied which became inoperable due to the heat that was being generated in the brake shoes. However, in order to stop the the lift, the bullwheel brake had to be applied. The bullwheel brake was a Yan 1500 acting directly on the flange of the bullwheel.

The test was performed again with the lift reaching a maximum reverse speed of 550 FPM and only the bullwheel brake being applied to stop the lift. The lift stopped adequately with a maximum deceleration of 1.52 ft./s2, although at the haul rope derailed at the top station when a chair got lodged into the guidage.

For the last test that was performed in this series, the main drive shaft that was connecting the gear reducer to the bullwheel was disconnected at the coupling adjacent to the gear reducer. The lift was allowed to travel in reverse with a couple of loaded chairs passing around the bullwheel. It was then instructed that the chairlift be stopped using the bullwheel brake, but since this lift has two stop buttons, the normal stop button was depressed inadvertently instead of the one for the bullwheel brake. Because of this, the lift gained a tremendous amount of speed in the reverse direction, reaching speeds up to 1500 FPM. The 57 pound concrete disk that were placed on the chairs were thrown 120 feet into the air from the center of the bullwheel. Chairs were dislodged from the haul rope and flung in different directions causing them to become tubular steel pretzels after going around the bullwheels. During this rollback, the chairlift traveled 1440 feet or 24 chair lengths resulting in total destruction of the carriers that went around the top and bottom bullwheels. The guidage rails for the top and bottom stations were damaged beyond repair and one carrier managed to get lodged into the lower stations guidage rails. The track rope brake was quickly applied, but because of the speed the lift was traveling and the chairs that were attached to the haul rope, the chairs moved the haul rope out of the track brake. The chairlift eventually slowed down and came to a stop because of the forces of destruction.

Day Two:
After a tremendous amount of work from the Winter Park crew to get the lift operational again after destructive rollback, testing resumed on schedule on June 19th. There were no chairs on the haul rope from 51 to 72 since they all had been piled to scrap from the severe rollback. Also, there were no sheave assemblies on the upgoing side on towers #18 and #20 because they were damaged during the same test too.

The third test that was performed was the oily rope test, to simulate what would happen if there was an oil leak with oil getting on the haul rope and bullwheel. To perform this test, crews lathered the haul rope and bullwheel oil and used the bullwheel brake to try and stop the lift. While the lift was being driven uphill, the haul rope would slip relative to the drive linear/sheave generating a considerable amount of heat, reaching around 250 degrees fahrenheit (The bullwheel brake wasn't applied in this test and heat was generated from the bullwheel still in motion while the haul rope wasn't in motion). The process was repeated again, but this time the lift was running in reverse at a line speed of 750 per minute. When the bullwheel brake was applied, the haul rope continued to slip on the bullwheel linear/sheave.

The fourth test that was performed was to see what would happen to a lift if a tree fell on the haul rope if it was in motion. With the lift operating uphill again, a tree 35 feet from tower #4 was cut and allowed to fall on the downgoing side of the haul rope. There was no carriage movement upper terminal, at tower #4A the haul rope was off the sheaves, while the cable catches on towers #2, #3, #4 suporrted the downgoing haul rope. This test was performed again at towers #16 #19, but the effects wern't as major as the first tree on line test. However, unlike the first test, in both the second and third test, the haul rope didn't derail from the haul rope when a tree fell on the upgoing line.

The fifth test that was performed was the most dramatic of them all. The fire test was carefully planned, including the fire department ready incase another fire broke out that wasn't planned. Trees and nearby foilage were soaked prior to the start of the burn.

The Eskimo's motor room was located in a concrete vault below the lower bullwheel and had a structural wood roof covered with asphalt-based materials. The only piece of equipment that was removed from the motor room prior to the fire was the auxiliary power unit. The fire was started by using some oily rags and placing them near a work bench. About 27 seconds after the fire was set, it was evident to the people around the lower station. About a minute and thirty five seconds after the fire was started, the lift came to a stop from the bullwheel brake hydraulic pressure line being severed by the fire. After 14 minutes after the fire became evident, the haul rope finally seperated causing the chairs to drop to the ground. The temperature at the bottom station from the fire reached as high as 1,800 degrees F only 6 minutes after the fire was evident. The fire was eventually put out by the fire fighters after 21 minutes into the burn.

The final test that was performed was to test out the lateral loads on towers to attempt to pull them out of the ground. Even though this was the least exciting test of the 6 tests that were performed, there was a lot of knowledge gained from this test. There was a total of four tower foundations that were tested during this test, two deep footed foundations by Riblet and two shallow tower foundations by Lift Engineering/ Yan. During this test, there were forces that were applied to both the top and bottom of the towers. Both the Riblet tower foundation footings failed having structural tubing issues, one by failure of the collar weld while the other failed do to the tower tube bending. Both of the Lift Engineering towers also failed because of uprooting from the ground.

All pictures belong to Jenlynn Inc. Content gathered from SAM Magazine ©

Tad Nordstrom of Jenlynn sits behind a chair with computer measuring equipment.

Rosette strain gauges were placed on some of the chairs hanger arms to measure the activity at various locations on the lift, along with chairs passing around the bullwheels.

A Riblet carrier still hangs from the haul rope after its hanger arm was severely bent after it passed around the bullwheel during the rollback test. Workers of Winter Park and Jenlynn survey the damage of the Eskimo lift after the rollback test was performed.

A Riblet carrier is seen here lodged upside down into tower 2 causing the haul rope to derail off of the sheave assembly.

Another carrier is lodged into the lower station's guidage rails causing damage to them.

Here's a shot looking up the lift line after several carriers were destroyed after they passed around the lower bullwheel during the rollback test.

The hanger arm of chair #74 is snapped in half after it was broken during the rollback, but the safety rode (wire) kept the chair intacked after the test.

A sheave axle lays on the ground after it failed catastrophically during the rollback test.

A chair's clip is still attached to a severed section of the haul rope after the carrier got caught on an object, but eventually the chair broke free from the clip.

The tree on line test was performed just above tower #4 on the down going rope side. This test was performed 3 times while the lift was running. 2 times near the top station, while 1 time near the bottom station. The tree that fell near the bottom station did the most damage to the lift do to its size and weight.

One of the last and most dramatic test that was performed was the fire test. The test was designed to see what would happen if a fire were to break out in a lift's motor room. The picture on the left was taken about 14 minutes after the fire was started and the entire station is engulfed in flames. The lift's haul rope snapped right before this picture was taken.

The strand of wire on the left is the result of the fire which resulted in the ductile failure of the individual wires.

Fire crews were ready incase the staged fire got out of hand.

The last and final test that was performed on the Eskimo lift was the tower pull. There were four tower foundations tested, consisting of shallow and deep tower foundations. The tower on the left is of tower 5A with a shallow block tower footing design and it was easily pulled over with the foundation coming out of the ground.

This is the result of tower 5 with a deep block footing. Even though it showed little movement during the pull, it failed because of bending.

All pictures belong to Jenlynn Inc. Contenet gathered from SAM Magazine ©