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Thread: Wind Hold

  1. #1

    Wind Hold

    I was up in the middle of the night last night and was counting through the SB trails in my head (my version of counting sheep) and I started thinking about wind hold at LP/ME. I don't know much about wind hold so I thought it might be an interesting topic to discuss.

    What are the factors that put a lift into wind hold?



    Does it matter if it's a double/triple or quad?
    Does the age of the lift have anything to do with it?
    Does the exposure to a certain direction at either mountain determine the likelyhood of wind hold?

    What are the wind hold statistics on Super Bravo, Gatehouse, Heaven's Gate at LP?
    What are the statistics for Green Mountain, Inverness, Northridge and Summit at ME?

    Do most people know the way up top when Super Bravo is on wind hold? Valley Double across traverse to Heaven's Gate?
    Same over at ME - Inverness to Northridge Express trail to Northridge Quad

    What's the wind speed and direction that will put each lift on wind hold?

    Super Bravo
    Gatehouse Express
    Heaven's Gate
    Green Mountain
    Inverness
    Northridge
    Summit

    What other factors? Temperature, humidity have anything to do with it? Is there a certain time of day when wind hold is most likely? Are there more wind holds in a certain month?

    Appreciate an education from those in the know!

  2. #2

    Join Date
    Mar 2009
    Location
    In the woods, searchin for the perfect airplane turn
    Posts
    235
    Hi SVG,
    Lots of questions. I don't have many specific answers for you for many of your questions but I can give you some general info regarding wind effect on lifts, I having worked lifts for a while a K-mart.
    In general:
    Wind blowing across the lift line affects wind holds more than wind blowing up or down the lift line. Lift towers have sensors that trip when swinging chairs go by. This is an important safety feature of modern ski lifts. If chairs get close to crashing into the towers, the lifts need to be shut down. Think about a chair hitting a lift tower with skiers on it and possible getting hung up on the lift ladder!! Very dangerous, indeed.

    High volume quads like Bravo tend to be less affected by the wind since the chairs are much bigger and therefor heavier. It takes more wind to push those things around. Those quad chairs are a few hundred pounds each. Moreover, when fully weighted with skiers the chairs tend to swing less, again added weight and momentum of a full lift line keeps the chairs a little more stable.

    Wind blowing up or down the lift line can for single, double and occasionally triple chairs cause the line to "bounce". Especially when there is a long run between lift towers. Bouncing chairs also trips sensors as there becomes the danger of derailment. Very dangerous (See, 2010 Sugarloaf spillway double for derailment)

    I'm not sure of specifics for wind speed, but in general wind gusts over 30 mph tend to get the chairs swinging. Again, if there is a full liftline, they tend to not swing as much and likely avoid wind holds, but really it depends on the duration and speed of gusts. It doesn't take much to get a chair to swing enough to trip the tower sensor.

    In general things that help prevent wind holds:
    The sheaves are the round wheels on each tower that the lift line travels against. On "tension" towers the lift line rides on top of the sheave. At "compression" towers the lift runs below the sheave. Compression towers are usually found just before the slope changes from flat to steep, or from steep to very steep. Compression towers help reduce the swing of the lift line because there is tight pressure on the lift line there as opposed to "just riding on top" of the sheave.

    The length of the sheave train (the number of wheels at the top of the tower) also help reduce chair swing and bounce. Many towers have only two sheaves up hill and two sheaves down hill of the tower. They basically support the line. In areas where there tends to be cross winds (think the big open space on heaven's gate where paradise crosses ripcord) lift towers tend to have more sheaves to support the line. Also at the lift towers near the top end to have longer sheave trains since the wind tends to be stronger and more gusty at mountian tops (Duh). Lifts that tend to go on wind hold can be improved by adding to the length of sheave trains in the spots where chairs tend to swing.

    Wind breaks help reduce cross wind. Wind breaks are usually large billboard sized wooden panels that run parallel to the lift line in areas of open line that get exposed to cross winds. The panels block the cross wind and allow for more stable chair passage. Sugarloaf uses lots of these at higher elevations, especially along the quad that goes near Narrow gauge. There is a part of that trail where you actually pass under the wind block billboard. K-mart has some at the top of the Skye peak quad. The panels tend to not be a solid sheet but several 2"x12" or 2"x16" strung horizontally with small gaps to allow some wind to pass which keeps the tremendous gusts from taking out the wind block itself.

    Keeping tree lines near the lift lines, or having lift lines run through the trees tends to help prevent wind holds since the trees act as a natural barrier and wind goes up and over the lift line. Think about North Lynx. Most of that lift is protected by the trees.

    Surface lifts don't go on wind hold. Rope tows and Poma lifts can help get skiers to peaks when the lifts go down. Sugarloaf keeps a poma running near the spillway lifts for this reason. The magic carpet is, well magic. Tangent: wouldn't it be great if there was a magic carpet that ran along the side of claybrook between the building and the road from the bus stop up to the emergency health center by Timbers?

    Hope that helps gets you started on your wind hold education path.

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