To add to what liftmech mentioned…
There is no problem this is a planned event…and the 3’ foot stretch overnight is the marketing department artistic editing - read below.
Newer readers - For a better understanding of ropeway nomenclature go to this link (front page)
http://www.skilifts.org/old click on the Glossary tab. Scroll to counterweight, tension system and wirerope.
Most (but not all) ropeways have a carriage tension terminal – this is needed for applying rope tension - rope tension is needed for the bullwheel to have adequate traction when it drives the haul rope, prevent excessive sag between towers, adjustments for temperature, and to adjust for different load combinations.
The carriage rides on terminal rails. The red arrows in the image below point to the carriage wheels and you can see the tensioning device – in this case a block of concrete – in a pit in the snow.
Platter-double-rail.jpg (45.5K)
Number of downloads: 59
Some chairlifts have a single rail that the carriage rides on – improved, perhaps…cheaper to build yes.
Yan-single-rail.jpg (49.73K)
Number of downloads: 76
Some tension terminals have long rails, some short…short rails cost less.
Wirerope by the nature of the construction process is spun with small (very small) spaces between each wire. These spaces can be removed by various methods of “pre-tensioning” at the rope factory…this costs more, is hard to quantify, is not totally effective and because of those variables some ski resorts skip that option.
After tensioning and initial running (running is more effective than tension) these spaces almost disappear. The initial running may take 40 hours or 40 days and is dependent construction, temperature and length.
When the initial spaces are reduced, the diameter shrinks by a very small amount, and the rope gets longer due to its spiral construction.**
Some terms used by the industry are - construction stretch or reduction of construction stretch. The wires DO NOT STRETCH as they are quite resistant to tension stretching…somewhere around a factor of 10X the normal running tension they will stretch but this can only be done with special testing devices.
A further analogy
Remember that one Christmas when your aunt Nellie knitted you the sweater that had sleeves that were slightly shorter than your arms…you lengthened the arms by (pulling) applying tension that reduced the small spaces in the initial (knitting) construction…
So we have this very long wirerope that has run a few days, and it needs to be shortened due to the nature of its construction for the tension system to work correctly (as liftmech says above)…
this is a planned maintenance event and not a problem.
Down Time
The time to take to splice a rope of this size and get the lift in running order is approximately 250 man hours (think 10 guys @ 25 hours or an army of 25 guys @ 10 hours) of labor so the gondola will be closed for 2 to 3 days.*
Other links -
Ryer Rope (Ryer Family) as a few images, this one is from the gondola at Heavenly Valley (South Lake Tahoe) rope size is 56mm.
Ryer-splice.jpg (48.27K)
Number of downloads: 78
Link:
http://ryerrope.com/index.htm
Wire Rope life, stretch and splicing:
http://www.skilifts....?showtopic=7627
Early ropeway history:
http://www.skilifts....?showtopic=8342
Here is a splice on a smaller scale…you can try this at home with a piece of wirerope from the hardware store.
Small-splice.jpg (24.94K)
Number of downloads: 51
*Finding the rigging to final clean-up.
*Urban ropeways have specialized rigging and tensioning schemes so the splices can be done overnight with no delay of transportation services.
**If you have enough experience with the wirerope from the same
production run you can “fudge out” most of the known construction stretch during the initial splice.
1
Skier, on 10 December 2010 - 07:19 PM, said:
