Skilifts.org / SORT Forum

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Would be an interesting download!

Does anyone know the maximum angle of turn in lift line that can be achieved with a single support-depression-support complex of towers?

Winterhighland, on May 31 2007, 07:25 AM, said:

The way the design engineers think today, It hasn't been designed yet.

the reason for the property lines is, in mineral basin is in american fork canyon, where as the front side is LCC. a guy i work with at alta now works at the bird. he was at baldy this winter and he said they never had any alingment issues. it's a good to chair to ride as there is never a line for it, and there is some pretty decent skiing off of it.

LiftTech, on May 30 2007, 02:10 PM, said:

Sounds like a test question
If you drop a support assembly down out of plumb it will try to push the rope inside. If you drop a depression assembly down out of plumb it will try and force the rope outside. Reverse the rope direction if you're raising the assemblies up out of plumb. Having just seen what a completely bare rope will do on a light tower (it won't stay in the groove, that's for sure) I imagine any angle change made with sheave alignment alone needs to have quite a bit of load on all sheaves in the area to ensure that the rope stays where it should be. A heavy rope is much less likely to wander and screw up alighnment in what must be a critical area. Do I pass?

skierdude9450, on May 30 2007, 03:33 PM, said:

AAre you kidding?! Why would Vail have POMA do Upgrades to a Dopelmayr lift...... That just doesn't make sense. I know that POMA guys are already there, but still. What might POMA do to the lift?

Winterhighland, on May 31 2007, 07:25 AM, said:

Its also an interesting upload!!! You have to hold on to the chair to keep from falling off over that turn. It makes the chair shake a lot!

Poma upgraded the Doppelmayr Peak chair and moved it to become Franz's.

Winterhighland, on May 31 2007, 06:25 AM, said:

Hell ya! Too bad they don't let you.

It really shakes you around on the deflectors. It's been a couple years since I've been on that lift, though.

Skier, on Jun 2 2007, 06:12 PM, said:

Wasn't it the other way around?

The original Peak chair was a POMA!

SkiBachelor, on Jun 2 2007, 09:46 PM, said:

I'm pretty sure it was Doppelmayr to Poma. The old Peak chair was a Doppelmayr bottom drive. Poma made that terminal a top drive, which looks really weird with the tri leg design. Then they added new towerheads, a new Poma return and chairs.

Lift Kid, on Jun 2 2007, 03:09 PM, said:

It may shake but its not as bad as you make it seem. If youre in the chair properly there is no chance of falling out as you go arround the turn due to the turing motion itself.
This post has been edited by poloxskier: 02 June 2007 - 11:41 PM

liftmech, on Jun 1 2007, 04:24 PM, said:

Sounds like a test question it was or is
if you drop a support assembly down out of plumb it will try to push the rope inside. Not for the purpose we have been talking about. If you drop a depression assembly down out of plumb it will try and force the rope outside. Not for the purpose we have been talking about. Reverse the rope direction if you're raising the assemblies up out of plumb. I’m not sure what you mean? Having just seen what a completely bare rope will do on a light tower (it won't stay in the groove, that's for sure) it will if it’s truly aligned and there are no other forces applied (wind, chair swing ect.) I imagine any angle change made with sheave alignment alone needs to have quite a bit of load on all sheaves in the area to ensure that the rope stays where it should be. It does help but only with the other forces. (Wind, swinging chairs, loaded vs. empty chairs and miner misalignment) A heavy rope is much less likely to wander and screw up alignment in what must be a critical area. Yes. Do I pass? No, sorry. Think about what I said. “The sheave(s) needs to support the rope in the direction of the load,” so where is the load? Rope under tension always wants to go in a straight line, change the direction of the line and you change the direction of the load, Change the angle of the load by 5 degrees and you must change the angle of the sheave 5 degrees into the load so that the load is projected straight thru the middle of the sheave. The angle of the sheave must always match the angle of the load or the rope will want to move to make a straight line. So I ask again, why is a support tower tilted one way and a compression the other to change the angle in the same direction?

The direction of the load is opposite? If you tilted either of the assemblies the other way, the rope would try to go to the inside (maybe to the outside on the compression assembly - I can't tell, whatever the case may be the rope would try and make a straight line between the two stations.

In non-lift terminology, if you want to make a turn where the line is on the inside of the turn towards the direction desired, you must angle the sheaves towards the outside of the turn and so that the rope follows the outside. If the direction change is from the outside of the turn, then the sheaves must be angled to the outside. So say a lift is on the left side drive (such as baldy express.) The setup for the uphill line is outside support, outside depression, outside support. That makes a small outside turn, large outside turn, and another small outside turn. (AKA small right turn, large right turn, small right turn.) If the sheaves went outside support, inside depression, outside tension, that would make a right-left-right turn.

Just to clear things up, since I don't know the correct terminology, inside=rope closer to the tower, and outside=rope farther away from the tower.

Quote

Here is my attempt to answer this question:
In the case of baldy at snowbird, and all other lifts that turn right, the haul rope is wanting to pull to the right on the angle change towers. Therefore, the sheaves need to be angled such to oppose this force. Or in other words, they all need to point somewhat to the left to go against the force of the rope wanting to go to the right.
I have attached an image illustrating the effect of moving an assembly 5 degrees out of plumb counterclockwise. Notice how the top side of the assembly is pointing 5 degrees to the left side of the vertical line. But the bottom is pointing 5 degrees to the right. Therefore if all the assemblies were angled the same way as in the image, the depression would be angled to the right since the rope rides on the bottom side of the sheaves in a depression. And since all of the assemblies need to be angled to force the rope to the left as previously stated, the rope would fall off of the sheaves since there is no opposing force.
Does this explanation make sense to anyone else other than me?

Does turning a lift line with angled sheaves like this have any effect on the wind stability of the haul rope? Does it make de-railments more likely, or affect the max operating cross wind speed?

The best way I could explain turning the rope using sheaves, is a picture, If I had it.
Does anyone have a picture of an old Mueller lift with a small bullwheel?

On some lifts Mueller used a bullwheel that was smaller than the line gauge; to do this right, on the first tower they canted the sheaves to keep them on the plane of the rope, or within the wrap angle of the rope.

I never experienced any problems with wind loading as long as the forces of the rope were directly down the center of the sheave, or properly in the plane.

chasl, on Jun 11 2007, 10:34 AM, said:

Here is a pic of what you speak of.

skiersage, on Jun 11 2007, 12:03 PM, said:

Excellent picture, you will note that the sheaves are canted into the plane of the rope and at the same time when doing this you can still rotate the sheave assembly on line if needed.

There are other instances that this drive arrangement will work for you.
One Mueller lift we had to deal with had 8 to 10 towers off line, up to 15 inches.
Some towers had horizontal sheaves mounted on the lead in and outgoing ends of the sheave frame to stop inside derailments.(home made, I found this before I had taken the position, I actually looked forward to the challenge)

Think about how a lift with a smaller bullwheel and a wider line gauge will work to your advantage in this type of situation.

Allan, on Jun 10 2007, 06:45 PM, said:

In its simplest form yes, the load is the opposite, the load change from vertical is the same so the sheave angle from vertical is the same, just in the opposite direction. To say a compression or a support will de-rope to the inside or outside matters which side of the turn you’re on, (inside or outside) however it will de-rope towards what would be a straight line.