5 replies to this topic

[Peter]

A couple questions I have about the process:

1. How do engineers go from a topographical map to a lift profile? For example, How do they decide where to place the towers and how tall the towers should be? I know there are obvious factors such as winds and ski runs with tower placement, but there must be more to it than just guessing.

2. How are the actual components designed on the computer? What programs are used?

3. When the liftline has been cut, how do surveyors know exactly where a tower should be placed? How exact does the tower plavement need to be? That is, how much room for error is there that can be corrected by adjusting sheaves?

In Washington State, a graduation requirement for high school is to do an 80 hour culminating project, and I am doing mine on the construction/engineering of the new Northway lift at Crystal Mountain. Hopefully I will be up there a lot taking pictures of the process. More questions to come...

[mikest2]

Skier, on Apr 23 2007, 07:06 PM, said:

A couple questions I have about the process:

1. How do engineers go from a topographical map to a lift profile? For example, How do they decide where to place the towers and how tall the towers should be? I know there are obvious factors such as winds and ski runs with tower placement, but there must be more to it than just guessing.

2. How are the actual components designed on the computer? What programs are used?

3. When the liftline has been cut, how do surveyors know exactly where a tower should be placed? How exact does the tower plavement need to be? That is, how much room for error is there that can be corrected by adjusting sheaves?

In Washington State, a graduation requirement for high school is to do an 80 hour culminating project, and I am doing mine on the construction/engineering of the new Northway lift at Crystal Mountain. Hopefully I will be up there a lot taking pictures of the process. More questions to come...

1. Survey the line and place hubs along it. Historical data on snow depth and obvious things such as run crossings help determine the rope height.

2. Autocad and good old engineering

3.The hubs you placed on the original profile survey are used to plot the tower sites. You want to be bang on in construction, it's no harder to be exact than to be off by an inch. The last lift I built (1992) we were allowed 2" up/down the line and 1" across it.

You should make friends with the crew at Crystal this summer !!

[Peter]

What are hubs? How do they decide where to put the hubs?

[mikest2]

Skier, on Apr 23 2007, 07:59 PM, said:

What are hubs? How do they decide where to put the hubs?

To survey a line, you start with a top and bottom point. Then you shoot (sight) points in between them on the same line. These are hubs, hubs are a specific point on the line (chainage/horiz distance) and they have a height (elevation) above datum (the elevation of the bottom point of the line). generally a profile will start from the point at the bottom expressed as 0/0; 0 elevation and 0 chainage.

[spunkyskier01]

interesting as i am doing this right now as project. the way were doing it, and this is the old school way, is you measure the distance between each topo line then you plot that point onto the large lift profile graph. Then we place both terminals and string a weighted chain between both terminals on the map. then we add pins to certain points on the map to make sure the whole chain is off the the represented ground. each pin represents a tower. . I am sure computers can do this many times faster, but this still works.

[FSJ]

Skier, on Apr 23 2007, 07:06 PM, said:

A couple questions I have about the process:

1. How do engineers go from a topographical map to a lift profile? For example, How do they decide where to place the towers and how tall the towers should be? I know there are obvious factors such as winds and ski runs with tower placement, but there must be more to it than just guessing.

2. How are the actual components designed on the computer? What programs are used?

3. When the liftline has been cut, how do surveyors know exactly where a tower should be placed? How exact does the tower plavement need to be? That is, how much room for error is there that can be corrected by adjusting sheaves?

In Washington State, a graduation requirement for high school is to do an 80 hour culminating project, and I am doing mine on the construction/engineering of the new Northway lift at Crystal Mountain. Hopefully I will be up there a lot taking pictures of the process. More questions to come...

This response is somewhat simplified. Should give you a basic idea.

1. Generally we use profile data provided by a surveyor. General topo maps are too inacurate, except for estimates. The surveyor will pick a location along the axis of the lift and use it as a reference point. This point is usually a location that will not be disturbed during construction. Major geographic features of the lift line will be recorded by horizontal distance from the reference point and their elevation. Placement of towers is both science and art. There will be areas towers can't be placed (cliffs, roads, etc). A constant pitch slope is the easiest to place towers on. We know the rope weight and passenger load from the lift specs and the loading capabilitiy of 4/6/8 sheave assemblies. Basically, your going to have a sheave per 800lbs of supported load. The complications come in when terrain is varied. Towers must be place to maintain a minimum clearance and at times, a maximum. If there is a concave section, hold down towers may be used and keeping these properly loaded can be tricky. It is a balancing act.

2. Most component are already designed. Maximum loadings for tower assemblies and terminals will be known. Horsepower is calculated from capacity, vertical rise and friction. Minimum rope tension comes from preventing rope slip on the drive sheave. Rope tension will add to tower loads. Most lift companies will have proprietary programs they use for speciallized lift calculations. Some of these programs may be as simples as excel spreadsheets. Structural designs can be done with any structural program such as Risa or can be done with Autocad or Solidworks, either manually calculating required sections, or with computer modeling of the stresses.

3. A construction profile will be provide which will have the tower base coordinates. The surveyor will mark these positions. To keep from loosing these positions during construction, reference points are usually placed near the tower location so a string line can be run to find the center later.