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Facts & Features : Eskimo
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.
- Manufacturer: Riblet
- Installed: 1963
- Type: Center pole fixed grip double chair
- Slope Length: 4,320 feet
- Vertical Rise: 1,212 feet
- Speed: 500 FPM
- Capacity: 1000 PPH
- Chair Spacing: 160 FT
- Number of Chairs: 155
- Line Guage: 1,0' 1"
- Drive Equipment:
- Power: 150 HP/ Vault Drive
- Cable Backstop: TRB
- E-Brake: Yan 1500 Cal.
- Service Brake: Spring APPL. and Hydraulic Release.
- Oily Rope
- Tree on Line
- Tower Pull
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.
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
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.
Tower "Constructive Destruction" Table
*A Towers indicate shallow block footing design.
||FAILURE LOAD #
||BASE MOMENT K-FT
|4 @ YIELD
All pictures belong to Jenlynn Inc. Content gathered
from SAM Magazine ©
Nordstrom of Jenlynn sits behind a chair with computer measuring
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.
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.
Riblet carrier is seen here lodged upside down into tower 2
causing the haul rope to derail off of the sheave assembly.
carrier is lodged into the lower station's guidage rails causing
damage to them.
a shot looking up the lift line after several carriers were
destroyed after they passed around the lower bullwheel during
the rollback test.
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.
sheave axle lays on the ground after it failed catastrophically
during the rollback test.
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.
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.
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.
strand of wire on the left is the result of the fire which resulted
in the ductile failure of the individual wires.
crews were ready incase the staged fire got out of hand.
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
is the result of tower 5 with a deep block footing. Even though
it showed little movement during the pull, it failed because
All pictures belong to Jenlynn Inc. Contenet gathered
from SAM Magazine ©