32 replies to this topic

[SkiBachelor]

Here is a picture from the alpinforum that someone posted of a tower with sun spot deflectors so the towers don't expand and contract. Here in North America they just paint the towers white, while in Europe they have these white plates that act as shields from the Sun's rays.

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[Eric]

Why we don't have those ?

Nice towers

[SkiBachelor]

Probably because they just came out this season. I don't know. Maybe painting the tower white is cheaper?

[KZ]

I wonder how much of a difference those panels actually make. Interesting design though

[Allan]

Only one problem with painting a tower white... then it matches the snow! It would be the ideal solution though. I bet these reflectors would make a difference, as they would stop the heat-warp assosciated with the sun beating on the tower all day!

[liftmech]

Painting the towers white or light grey is easier, but putting on reflective panels is probably a more efficient fix. We in North America do have these; ride the Lenawee lift at A-basin and there are several towers with them attached.

[liftmechanic]

We had some white vinyl covers manufactured that go from the base to the bottom of the tip deflector, they attach with bungees. They look good and are inexpensive and effective.

[floridaskier]

So is that why, on some lifts in America, the last few towers of a lift (the ones that get exposed to the sun the most) are painted white?

[liftmech]

Correct. Bachelor in particular had problems with terminal misalignment on the Northwest in its first season. After investigation it was determined that the last breakover towers were bending and moving the rope out of position in the top terminal, causing I don't know what all kind of problems. So they painted the towers white to correct for solar bending.

[Kelly]

More information on heat bending of towers -

Heat bending is also called Expansion or Thermal Expansion.
Thermal Contraction is negative Thermal Contraction.
All materials have a "multiplier" or Coefficient of Expansion per degree of change.
Most "multipliers" are measured in the 32F to 212F heat range.
Water and wax are two common materials that don’t quite have the same thermal properties as most materials.

The Coefficient of Expansion for steel is -
.0000065 per degree F per inch

A flat bar of steel 50' will expand in length .0039" per degree.
Common differences in temperatures on a tower are 50F between the shady side and sunny side.
The same bar of steel will expand 0.195" per 50 degree change.
Math for above problem-
.0000065 x 50 x (50x12) = 0.195

I agree .195" is not much so why does the tower move?
One side helps the other side move – cold shrinking and hot expanding.
The two sides of the tower "couple" or reinforce each sides thermal movement.
A tower that is laying flat with no restraints will soon look like a banana if heated or cooled along its length.
A tower that is constrained at its base will move at the top.
The forces generated by thermal expansion are much greater than any haul rope induced load and will force the haul rope out of its natural plane.
In large changes in tower heights over short distances (breakover to top terminal) thermal change is more apparent.
Lifts with all towers the same height will bend equally and not be noticed except by a transit survey.

Railroad tracks, exhaust systems and bridges are common items that are designed for thermal change.
Long ski lift tension carriages have to accommodate thermal change of haul ropes, if the time of the splice is at a temperature extreme.

What would the thermal change of a haul rope 3000' long with a 120 degree difference between measurement times?
(answer to be given at a later date)

Ryan B

[liftmech]

I'm still working on the math for that problem, but I've got another example of thermal expansion/contraction. All other factors accounted for, the Flyer's haul rope has lengthened 2' in the last 4 days due to thermal expansion. The carriage position on Tuesday was 9'; today it was 8' (I measure from the back end of the carriage rails). Tuesday the air temperature ranged from -10 F to 0 F; today it reached +40 F. You can see what effect temperature has on steel.

[SkiBachelor]

Does anyone have any more info they would like to add to this page? I'm planning on turning it into a page for the Skilifts.org website in the near future.

P.S. Does anyone know if there is another topic like this? I've been trying to find it but the stupid Invision search is saying stupid stuff when I type certain keywords, even when they are longer than four characters.

[iceberg210]

Only on Snowbirds High Speed Quads are the towers either painted white or have vinyl strips attached to the towers.

[SkiBachelor]

So are you saying over at Alta they are not or that the fixed grip lifts don't have them?

[GravityAddict]

I have not seen them used at Alta, but it will be interesting to see what happens with the new Collins lift this spring when it starts to heat up rapidly. Thats when I have noticed the biggest problems at Snowbird.

[KZ]

The top breakovers on Cornice have extra coverings over them with about 4 inches between these metal coverings and the main tower. Northstar also puts vinyl covers over almost all of the towers on Lookout.

[floridaskier]

Snowbird enjoys putting those white tarps over their towers, they look like they forgot to paint part of the tower and are covering it up but if it works, whatever.
DV has the top tower or two white on two high speed quads from 1996 but no other lifts. These two are definetly not the two most exposed. No idea why, maybe they didn't think it made much difference

[edmontonguy]

Both the Top of the world and Paradise lifts @ lake louise have the white towers on top as they are well beyond the treeline.

This post has been edited by edmontonguy: 07 December 2004 - 05:50 PM

[iceberg210]

Only the HSQ's at Alta and Snowbird have tarps on the towers but Snowbird is the only one with white towers. None of the FG's at either resort have tarps or white towers.

[SkiBachelor]

Fixed grip lifts don't really need to have their towers painted white because they arn't detachable lifts. The reason why the towers on detachable lifts tend to have their towers white is because when a carrier enters or leaves a terminal, the grip can cause damage to the terminal's rails and/or the grip itself.