28 replies to this topic

[Andy1962]

Tramway Guy, on 02 March 2015 - 11:50 AM, said:

The tower and footing are designed to withstand normally imposed loads with normal factors of safety. Once loads that exceed those amounts are imposed, failure will happen in unpredictable manners and degrees.

chopped off the rest of the paragraph to focus on the first sentence. Agreed that all chair lifts are designed to withstand normally imposed loads and the safety factor is increased by several factors above that by design decisions made by engineers. However one would think that if a ski lift designer has not already done a test of dropping VERY BIG live trees on a similarly designed lift line, then the VERY BIG trees need to be cut back from the liftline of any new lift, at the time of the installation of the lift, or the skilift needs to be installed farther away from the treeline, so that the tops of the trees cannot hit the ski lift cable. (simply looking at already established practice in the ski lift building industry over the past 60 years. People learned stuff from seeing others build ski lifts and from seeing those lifts exposed to different weather conditions. ) If the decision is made to leave the trees in place so that the mid section of live trees (or even dead but not rotten) can make contact with the ski lift cable, then really one can say that the lift has NOT been designed and tested for normally imposed loads and conditions.Someone did not do designing, they did hoping. Because in real life trees do fall down. I think that most people would consider trees falling across the path of a ski lift liftline to be a normally foreseeable event over the course of the 30 to 40 year life of a chairlift. One would normally expect that the towers would be made taller so that the tops of trees cannot hit the cable on the way down, or the tops of the trees would be cut off enough so that the remaining part of the tree cannot damage the chairlift on the way down. Since looking at the pictures, of the damaged lift in question, it looks like the trees are softwood trees that do not take well to having the top half lopped off, the only option would be to make the liftline right of way wider. Thats the way it has been at every ski area I have ever ridden a ski lift at. Shame

This post has been edited by Andy1962: 02 March 2015 - 07:03 PM

[Tramway Guy]

Well! If I read you correctly, every lift tower must be designed for a 24" diameter tree landing on it or the design is inadequate? Or the clearing must be, say 100 feet from the center of the lift?
You need to propose it to the ANSI B77.1 committee.

[liftmech]

The Forest Service probably won't go for a 200' wide liftline. Just sayin'.

[DonaldMReif]

liftmech, on 04 March 2015 - 01:59 PM, said:

The Forest Service probably won't go for a 200' wide liftline. Just sayin'.

Most lifts I know of only have lift lines that wide if they are entirely above timberline where no trees grow (think Imperial Express SuperChair, or the Kensho SuperChair above tower 14). I mean, I think the width of the right of way in this part of the Rocky Mountain SuperChair is probably well under 60 feet:

This post has been edited by DonaldMReif: 04 March 2015 - 02:20 PM

[Andy1962]

Tramway Guy, on 04 March 2015 - 01:33 PM, said:

Well! If I read you correctly, every lift tower must be designed for a 24" diameter tree landing on it or the design is inadequate? Or the clearing must be, say 100 feet from the center of the lift?
You need to propose it to the ANSI B77.1 committee.

I get it. I was being a little harsh. But I do see that on most ski lift right of ways, the biggest trees are trimmed back, once the new lift line has been set. When a new lift is installed up an already open corridor, the trees are usually cut back somewhat. Usually its because over the course of thirty years of the previous lift being in place, the trees have got bigger and the edge of the forest has crept towards the old ski lift. Its does not have to cost lots of money. The forest could have been harvested / thinned prior to the lift being installed and the ski area could have made money from this harvesting. I also know that somewhere between my position of "should not have happened" and others's position of ' it does happen, we will rebuild" is the truth. The human race learns collectively by voicing our concerns /mistakes. Sure glad nobody builds high speed lifts today like YAN used to build them. Had some great features, and some bad ones. Please tell me that the concrete foundations of the failed Rampart lift at Snowqualmie meet current ANSI standards. I think that all that some people are suggesting is that the rest of those fountains on the Rampart lift should be checked to make sure they DO meet code. And if the answer to that statement is MYOB, then don't ever expect me to spend my ski dollars at that ski hill.

But step back a minute and accept that the previous statement that the lift was built with a lot of "hope" has a grain of truth to it, because choices were made to build the ski lift with short lift towers, to keep it low to the ground and out of the wind. Those were design choices. And since the threat (the biggest trees ) was not removed, one cannot be surprised by the fact that a big tree fell down over the course of the lifetime of the lift. Maybe in this case the lift corridor DOES need to be 100 feet wide, or 150 feet wide. Or taller towers. Whatever it takes to make sure that the lift can still stand up, in foreseeable circumstances, with people on it. A tree falling across the corridor of a ski lift during the 30 year life of the lift is forseeable. It scares me that people could have been on it.

This post has been edited by Andy1962: 04 March 2015 - 09:49 PM

[Andy1962]

liftmech, on 04 March 2015 - 01:59 PM, said:

The Forest Service probably won't go for a 200' wide liftline. Just sayin'.

and having read all of you, I see your point too. . however the towers can be built taller so that when a tall tree comes down, and the top part (say ten to twenty feet of the tree) hits the ski lift cable, it has the potential of bouncing off or of the tree top breaking off. If the trees are big enough that the bottom half of the tree can hit the ski lift, remove them. leave the rest of the trees. It called thinning. In a few years, other trees will fill in and no one will notice the gaps in the forest canopy.. This was not an accident. It was an inevitable result of DESIGN decisions and choices made by people.

[liftmech]

Agreed. I had a tree hit my lift last fall, and as it was at the tallest (65') tower all it did was break the top of the tree out.

[Phalanger]

Slightly different result in Europe: http://m.bbc.com/new...europe-31760605

[Peter]

Repairs are complete although it never did snow.

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