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  1. #276
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    Aug 2014
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    Quote Originally Posted by Dhelihiker View Post
    I've seen decent sized cables snap in construction. Albeit not the size of those but they snap pretty damn clean and really fast.
    Whomever did that was either really dumb and lucky or really smart and lucky. I'd be more concerned with cable on the other side of the riblet that I didn't cut. I think the doing it at the very top would be the safest.
    Would you mind deleting safe terrorist technique please?
    Let them make the ultimate sacrifice, eh?
    Whoops... well I'll delete if you will...
    Time spent skiing cannot be deducted from one's life.

  2. #277
    Join Date
    Jun 2009
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    South of 49
    Posts
    749
    I've always wondered how the wear of ski lift cables changes in different temperatures, -20c some days at Whistler and +40 on other days in the hot summer sun in the alpine.

    Is anyone familiar with how haul ropes used in ropeways, ski lifts etc., are engineered to prevent issues from the ductile-to-brittle transition temperature of steel where they are used in climates with wide variations in temperature?

    Is that even an issue in modern systems?

    As per https://www.researchgate.net/publica...iled_Wire_Rope

    Results indicate that considerations have to be given to the occurrence of corrosion, notches, low temperatures, and dynamic loading conditions when replacing wire ropes and this may necessitate the replacement of wire rope earlier than the time dictated by the criterion of 10% loss in breaking strength.
    and as per https://www.quora.com/What-is-the-du...on-temperature

    But in the process, when these ships were sent into very cold North Atlantic waters, some failed. Some literally split in half. They fractured catastrophically. At first it was thought that perhaps there were bad weld nuts to explain the failure. But when the materials themselves were sent back to Cambridge University in England for analysis, is when metalers then discovered this ductile to brittle transition concept. And it's a case in which a material that performed just fine in a room temperature, ambient, atmosphere of the laboratory, in a very cold environment became brittle, like a piece of glass.

  3. #278
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    Jun 2009
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    South of 49
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    I guess there's two new topics on inquiry I'm introducing
    ... since the fatigue issue is one and then the actual mechanism and prevention of fatigue is another.

    Take for instance the storage regiment:

    Does the company (any ski or gondola operator) store cabins during extreme winds? Or just let them fly?

    As an inquiry, there is this paper, Analysis of Oscillations in a Cableway: Wind Load Effects, which comes to the conclusion that:

    However, this model shows that with huge wind loads cabins are supposed to be detached and put into the storehouse. This is what actually is done in real conditions. Normally cabins are detached and stored in the storehouse for wind speeds above 90 km/h.
    In another study of wind and cable effects, there is this research summary How Windproof Are Cable Cars? which says:

    Observations by operating personnel of certain cable car systems have shown that a lateral vibration of the pendulum with large tilt angles can occur not only when the crosswind is blowing gustily but also when the wind is calm.
    The actual research paper, Oscillation Effects of Ropeways Caused by Cross-Wind and Other Influences has in the abstract:

    Not only strong crosswinds result in unacceptable cross-inclination of the gondola; there are also observations that substantial cross-oscillations of cabins are discernible during very different wind conditions and wind directions – even in calm weather conditions without strong crosswinds. These effects have been observed on ropeways as well as on chairlifts.
    and

    The maximum swing amplitudes measured in conditions of virtually zero wind speed and for different travelling speeds and thus different horizontal relative airflow speeds which are caused by the airstream reach distinct peak values at approximately 2.5 m/s (see Figure 22). However, this is also the area in which the theoretically determined vortex caused excitation frequency and the measured characteristic frequency of oscillations perpendicular to the longitudinal axis of the ropeway cabin correspond.

    By means of these measurements performed on a bicable ropeway and a comparison with theoretical results, it was possible to prove that the observed oscillations are indeed caused by vortex excitation. A remedy to reduce or largely prevent these crossoscillations which build up slowly can only be created by avoiding travelling in the critical speed zone for longer periods of time or by influencing the break-off frequency, e.g. by equipping the cabins with suitable spoilers.

  4. #279
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    Jun 2009
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    Sorry for all the nerdy info ... I just thought that someone might find that stuff enlightening or maybe even entertaining. Or give you all more fodder to mock my Dunning Kruger syndromes...

    edit: Oh gosh. Too much excitement for me tonight ...

    Jul 22 2019
    Australia - Thredbo - Chair falls of lift with patron on board:
    https://www.facebook.com/Thredbo.Res...type=3&theater

    ... Given safety is our top priority, we’ve been working with our expert team, SafeWork NSW and an independent engineer to investigate the incident thoroughly in an effort to provide you with the most accurate information as quickly as possible.

    Following the investigation, Thredbo can confirm that this was indeed an isolated incident caused by a freak gust of wind, and Gunbarrel Chairlift will resume operations tomorrow, Wednesday.
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    I wonder if the chair was swinging and the chair grip assembly contacted the ....
    OH never mind

  5. #280
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    Jun 2009
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    South of 49
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    I'm on a roll. One last thought ...

    A lot of lifts slow to less-than-or-equal 2.5 m/s in windy conditions. However, according to cabin vortex research, this is the exact range of forward speed that corresponds with the greatest vortex effects creating oscillations perpendicular to the longitudinal axis of the ropeway cabin.

    See https://www.tetongravity.com/forums/...78#post5734278

    I wonder what speed the Sea To Sky gondola was operating in when the first incident occurred in Feb 2019? Let's check the report.

    It says the speed selector switch was set to slow and the speed motor set point was 1.5 m/s ... and the actual speed according to the system data logger was 2.5 m/s.

    Now, back to page 16 of the report:

    The winds observed at tower 7 during the investigation were of greater intensity than those observed at tower 8. The wind meter installed at tower 8 was placed there to evaluate the wind down to tower 7, but due to the location of tower 7 at the top of steep terrain with a lack of natural protection, this location is exposed to increased wind speeds and possible vortex effects.
    "possible vortex effects"

    OK. Too much coffee. Time to catch up on Jeopardy episodes
    Last edited by puregravity; 08-15-2019 at 05:31 AM.

  6. #281
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    Feb 2008
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    here and there
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    14,835
    Dont ever cut that fabulous hair PG.

    And Nerd on!
    watch out for snakes

  7. #282
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    Feb 2014
    Posts
    1,194
    They updated/scrubbed the original article dropping any talk of recent maintenance and the healthy, thick rope quote from the GM.

  8. #283
    Join Date
    Dec 2012
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    9,269
    Quote Originally Posted by SB View Post
    And Nerd on!
    Holy crap. Imagine getting stuck talking to him at a party?
    "timberridge is terminally vapid" -- a fortune cookie in Yueyang

  9. #284
    Join Date
    Jan 2010
    Location
    Walpole NH
    Posts
    7,860
    You go to party’s?
    Smell my Mule
    crab in my shoe mouth

  10. #285
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    Dec 2012
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    9,269
    Quote Originally Posted by buttahflake View Post
    You go to party’s?
    Smell my Mule
    It's "parties."

    Click image for larger version. 

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    "timberridge is terminally vapid" -- a fortune cookie in Yueyang

  11. #286
    Join Date
    Aug 2011
    Location
    Der Town
    Posts
    6,428
    Click image for larger version. 

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    puregravity cracking the wind derailment code.

  12. #287
    Join Date
    Feb 2012
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    4,861
    Quote Originally Posted by puregravity View Post
    I'm on a roll. One last thought ...

    A lot of lifts slow to less-than-or-equal 2.5 m/s in windy conditions. However, according to cabin vortex research, this is the exact range of forward speed that corresponds with the greatest vortex effects creating oscillations perpendicular to the longitudinal axis of the ropeway cabin.

    See https://www.tetongravity.com/forums/...78#post5734278

    I wonder what speed the Sea To Sky gondola was operating in when the first incident occurred in Feb 2019? Let's check the report.

    It says the speed selector switch was set to slow and the speed motor set point was 1.5 m/s ... and the actual speed according to the system data logger was 2.5 m/s.

    Now, back to page 16 of the report:



    "possible vortex effects"

    OK. Too much coffee. Time to catch up on Jeopardy episodes
    Adderall is one helluva drug.


    Sent from my iPhone using TGR Forums

  13. #288
    Join Date
    Dec 2012
    Posts
    9,269
    Be careful with that stuff PG. I know a chick who went to rehab because of Adderall.
    "timberridge is terminally vapid" -- a fortune cookie in Yueyang

  14. #289
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    Feb 2012
    Posts
    4,861
    I read PG’s posts and envision the over caffeinated cheerleader in a room with the walls covered in pictures of gondola cables with colored yarn connecting them, furiously typing into his keyboard but nobody will listen.

    Could he be on to something here?


    Sent from my iPhone using TGR Forums

  15. #290
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    Dec 2012
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    9,269
    I envision a 1:32 scale Jeagerndrofer Gipfelbahn set up in his mom's living room with fans blowing at it from various angles and a half empty Adderall bottle laying on the side table.

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    "timberridge is terminally vapid" -- a fortune cookie in Yueyang

  16. #291
    Join Date
    Feb 2008
    Location
    Alpental
    Posts
    3,467
    You know you could just get a job as a liftie and learn everything
    “I have a responsibility to not be intimidated and bullied by low life losers who abuse what little power is granted to them as ski patrollers.”

  17. #292
    Join Date
    Oct 2003
    Location
    Seattle
    Posts
    18,004
    Yes, I think we can say with confidence that gondola cabins swing in strong winds. I'm still not sure what this has to do with the haul rope being completely severed.

  18. #293
    Join Date
    Oct 2017
    Posts
    147
    Quote Originally Posted by puregravity View Post
    The only other notable incident where a vandal tried to sabotage a ski lift was in Val Nord. The culprits were unable to cut through the main cableway.

    https://www.facebook.com/meteopyrene...type=3&theater

    Attachment 291197

    I think the image on the bottom right is the main cable and it is clear that the cords came apart under tension. The nice clean cut on the left was probably not cut under tension.

    Although there was multiple cables cut at the resort in this incident, indicating that they had lots of time, they were unable to cut the main cable with a rotary saw.
    Quote Originally Posted by puregravity View Post
    Global News
    https://globalnews.ca/news/5761722/r...ola-vandalism/

    "The company, which has never known of any threats or disgruntled employees remains baffled."

    Also shown on video is the same cable type and size, looks like a used rope sample on a picnic table nearby, but is not rope that was in use:

    Attachment 291198

    Attachment 291199

    Attachment 291200
    Quote Originally Posted by puregravity View Post
    I've always wondered how the wear of ski lift cables changes in different temperatures, -20c some days at Whistler and +40 on other days in the hot summer sun in the alpine.

    Is anyone familiar with how haul ropes used in ropeways, ski lifts etc., are engineered to prevent issues from the ductile-to-brittle transition temperature of steel where they are used in climates with wide variations in temperature?

    Is that even an issue in modern systems?

    As per https://www.researchgate.net/publica...iled_Wire_Rope



    and as per https://www.quora.com/What-is-the-du...on-temperature
    Quote Originally Posted by puregravity View Post
    I guess there's two new topics on inquiry I'm introducing
    ... since the fatigue issue is one and then the actual mechanism and prevention of fatigue is another.

    Take for instance the storage regiment:

    Does the company (any ski or gondola operator) store cabins during extreme winds? Or just let them fly?

    As an inquiry, there is this paper, Analysis of Oscillations in a Cableway: Wind Load Effects, which comes to the conclusion that:



    In another study of wind and cable effects, there is this research summary How Windproof Are Cable Cars? which says:



    The actual research paper, Oscillation Effects of Ropeways Caused by Cross-Wind and Other Influences has in the abstract:



    and
    What do the sharks have on you?

  19. #294
    Join Date
    Nov 2012
    Location
    Vancouver, BC
    Posts
    854
    "Asperger syndrome is an autism spectrum disorder (ASD) considered to be on the “high functioning” end of the spectrum. Affected children and adults have difficulty with social interactions and exhibit a restricted range of interests and/or repetitive behaviors."

    Between this dumpster fire and the bitcoin thread... pretty sure this is an accurate diagnosis for PG

  20. #295
    Join Date
    Oct 2017
    Posts
    147
    Quote Originally Posted by Gcooker View Post
    "Asperger syndrome is an autism spectrum disorder (ASD) considered to be on the “high functioning” end of the spectrum. Affected children and adults have difficulty with social interactions and exhibit a restricted range of interests and/or repetitive behaviors."

    Between this dumpster fire and the bitcoin thread... pretty sure this is an accurate diagnosis for PG
    Well, we all suspected he was a retardo, now we have proof.

    When does the short bus come for him?

  21. #296
    Join Date
    Sep 2014
    Posts
    1,513
    I for one am enjoying the geeking out on gondi/ski lift/haul rope stuff, P.G.

    Learning stuff and this of course leads to new questions...

    For example, dunno if it's been covered, but is haul rope examination performed manually by a human or is there a tech device that checks the rope for imperfections, fatigue, compromised integrity? Can imagine a sensor/scanner unit that would/could scan the running cable in real time 24/7 if money was no object? Don't they use such units for scanning oil/gas pipeline metal and welding integrity?

    Also, reading over that post incident report of the 2014 gondi cabin drop...just a layman here but could there be a coupla design issues in the torsion tube/cable catcher area? The clearance of both the torsion tube/rope catcher gap and the wheels of the gondi car carriage/tower sheave pulley wheels just seem insufficient for accommodating extreme event, large lateral swings of the cabin towards the tower. Could be in the context of low probability/high consequence event....but just like large deep slab avalanches being skier triggered on a deep persistent weak layer in low avalanche hazard time periods; they may not happen often, but they do happen.

    And with the tower design...why don't they have gondi car swing limiting appendages like i've seen on other gondolas? We had a detachable four person Mueller Lifts gondola further up the coast on Mt. Hays in Prince Rupert back in the day. The lift was exposed to the full brunt of storms rollin' in from the Pacific Ocean and there was more than one occasion where the swing of the car would result in a pretty good 'thud' of contact with the bumper thingy...no cabins fell off in the years of operation, AFAIK...but of course time may have erased memory; that's going back a good 30 years.

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    The great wide open of the Pacific Ocean. Next stop...Japan.

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    Master of mediocrity.

  22. #297
    Join Date
    Jan 2009
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    Park City
    Posts
    3,031
    I have an engineer friend whose job it is to eval lift failures. He’s not involved but thinks no way this was a “failure”.


    Sent from my iPhone using TGR Forums
    I rip the groomed on tele gear

  23. #298
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    Dec 2012
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    9,269
    These gondola things can swing pretty good without coming off the tracks.

    "timberridge is terminally vapid" -- a fortune cookie in Yueyang

  24. #299
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    Mar 2008
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    the ham
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    Quote Originally Posted by swissiphic View Post
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    7 minutes is 420 seconds.

    Coincidence? I think not.

  25. #300
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    Jun 2009
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    Quote Originally Posted by Leavenworth Skier View Post
    Click image for larger version. 

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    puregravity cracking the wind derailment code.
    Actually, that's the face I use when passing wind.

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