When you have a really long fixed grip lift, does it usually rollback when the brakes are applied? This always happened on the Summit Local at Mount Snow. It was a Yan triple from 1978 that was 7,700 feet long with a rise of 1,600 feet. Is this a normal occurrence? Something with the tensioning system? Or is this just a Yan thing?
1
Brakes on Long Lifts
Started by ss20, Oct 18 2013 01:37 PM
5 replies to this topic
#2
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Posted 18 October 2013 - 03:42 PM
Since you use words like "happened" and "was" I take it that this lift is no longer in service.
Modern lifts, both fixed grip and detachable use regenerative drives which use the drive and electric motor to slow the lift to a stop. The Service Brake applies just before Zero Speed. Lifts built in 1978 did not have this feature, and as such when a Stop was activated the drive shut off and the Service Brake brought the lift to a stop. The service brake was hydraulically opened and closed and pressure was applied by spring packs or weights. The closing rate was controlled by a flow control valve and the "stopping distance" was usually set up with the lift empty (hard for a mechanic to run through multiple stops with a fully loaded lift trying to get it dialed in!) When a fully loaded lift stops the full load trying to go back down the hill brings the lift to a fairly quick stopping distance and the Service Brake may not be fully set when the lift reaches Zero Speed.
All of this being said, there is an addition brake system- The High Speed Rollback Brake or Drive Train Backstop Brake should be set up to stop the lift from rolling backwards if the Service Brake does not set in time. On 1978 Yans these were generally located inside the gearbox and were an automatic brake (Zero rollback).
What you may have been experiencing was line bounce or recoil- the lift was trying to equalize the uphill and downhill forces after the stop.
Hope this makes sense.
Dino
Modern lifts, both fixed grip and detachable use regenerative drives which use the drive and electric motor to slow the lift to a stop. The Service Brake applies just before Zero Speed. Lifts built in 1978 did not have this feature, and as such when a Stop was activated the drive shut off and the Service Brake brought the lift to a stop. The service brake was hydraulically opened and closed and pressure was applied by spring packs or weights. The closing rate was controlled by a flow control valve and the "stopping distance" was usually set up with the lift empty (hard for a mechanic to run through multiple stops with a fully loaded lift trying to get it dialed in!) When a fully loaded lift stops the full load trying to go back down the hill brings the lift to a fairly quick stopping distance and the Service Brake may not be fully set when the lift reaches Zero Speed.
All of this being said, there is an addition brake system- The High Speed Rollback Brake or Drive Train Backstop Brake should be set up to stop the lift from rolling backwards if the Service Brake does not set in time. On 1978 Yans these were generally located inside the gearbox and were an automatic brake (Zero rollback).
What you may have been experiencing was line bounce or recoil- the lift was trying to equalize the uphill and downhill forces after the stop.
Hope this makes sense.
Dino
"Things turn out best for the people that make the best of the way things turn out." A.L.
#3
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Posted 18 October 2013 - 04:06 PM
Thanks, that makes sense.
The lift was removed in 2011 and replaced by the Bluebird Express.
The lift was removed in 2011 and replaced by the Bluebird Express.
Ski Instructor at Thunder Ridge... 300 vertical feet 45 minutes north of New York City. 3 Borvig chairs from the 60s and early 70s.
#4
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Posted 18 October 2013 - 11:19 PM
Puma lift is a YAN at Sierra at Tahoe resort in California. The lift is a fixed triple, top drive bottom tension. When the lift stops, the carriage moves a lot more than you would expect normally from a fixed grip.
http://www.skilifts....a/puma/puma.htm
http://www.skilifts....a/puma/puma.htm
#5
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Posted 19 October 2013 - 10:06 AM
SkiLiftsRock, on 18 October 2013 - 11:19 PM, said:
Puma lift is a YAN at Sierra at Tahoe resort in California. The lift is a fixed triple, top drive bottom tension. When the lift stops, the carriage moves a lot more than you would expect normally from a fixed grip.
http://www.skilifts....a/puma/puma.htm
http://www.skilifts....a/puma/puma.htm
On long top drive bottom tension lifts, the heavy side seems to roll back slightly, especially when there is a load on the heavy side and it is most noticeable when you are a passenger on the lower part of the lift. During a start the bellies in the rope are pulled out of the light side of the lift and remain in that condition while the lift is pulling a load uphill. during a stop that slack that was in the rope bellies on the light side are re-established resulting in a reverse surge and is also seen in active carriage movement as well.
"Maybe there is no Heaven. Or maybe this is all pure gibberish—a product of the demented imagination of a lazy drunken hillbilly with a heart full of hate who has found a way to live out where the real winds blow—to sleep late, have fun, get wild, drink whisky, and drive fast on empty streets with nothing in mind except falling in love and not getting arrested . . . Res ipsa loquitur (it speaks for it self). Let the good times roll." HT
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