25 replies to this topic

[oceanwanderlust]

At most resorts, their website displays the lift status. At Whistler, I believe the on mountain signs even display the line length. Is this information gathered automatically or is it manually radioed to a central data entry person?

If this information were to be gathered automatically from the PLCs of each lift, what other information could be available/useful? Speed, Chair spacing, temperatures, haul rope position?

Speaking of haul rope position, I see sensors on most towers... is this information usually fed back to a central control panel or are these just trip sensors that stop the lift if the chairs start swinging?

thanks for whatever info you can provide on this vague topic

joe

[Lift Kid]

Hmm, well lets see if I can answer some of these questions for you...

At most resorts, their website displays the lift status. At Whistler, I believe the on mountain signs even display the line length. Is this information gathered automatically or is it manually radioed to a central data entry person?

Now I'm not sure how all of this works. I do know how Vail's system works though. Basically, the status signs are all at the tops of lifts. Each lift name on the board has three lights- Red (closed) - Yellow (long wait) - Green (open, shorter line). There is a box on the back with light switches for each bulb. The ski patrollers stop by and change them as needed. I believe the ski patrol at Vail monitor the lines and radio it to PHQ. So, Vail's system is very simple, and I rather like it. However, Places like Breckenridge, Keystone, etc. with Digital boards, I have absolutely no idea how that is done, but I would assume the statuses are radioed in by ski patrol or lift ops to an office with the computer.


If this information were to be gathered automatically from the PLCs of each lift, what other information could be available/useful? Speed, Chair spacing, temperatures, haul rope position?

I'm not really sure what you mean by this. Do you mean that the status boards could use that info? or what?

Speaking of haul rope position, I see sensors on most towers... is this information usually fed back to a central control panel or are these just trip sensors that stop the lift if the chairs start swinging?

The sensors you are seeing on towers are RPD's (a.k.a. Rope Position Detectors). Basically, an RPD is either on electric sensor which, if I remember correctly, uses a magnet with the metal haul rope like a switch, or a brittle bar/fork. A brittle bar or brittle fork is a piece of metal that snaps when it comes in contact with the cable. These RPD's disconnects the electric circuit, therefore tripping what is called a "fault". The electric drive and PLC process faults. The PLC can detect exactly what kind of fault it is (i.e. RPD fault, Stop button fault, carriage travel fault, tension system fault, and many, many more!), and where. Some faults can be bypassed (i.e. on detachable lifts the anti-collision detectors can be temporarily bypassed, along with others) and others, such as RPD's, must be fixed and the circuit re-connected before the lift will reset.

I hope that helps! Let me know if you would like more clarification on any of this. Also, you can PM me and I can send you some pictures of lift control systems, along with labels and descriptions.

[SuperRat]

Percent load can be estimated by the amps the electric motor is drawing. I work on a '85 CTEC triple chair that has a meter that reads this way. But once every chair is loaded how do you determine how long the wait in line is? Most of the information you mention would only be of interest to the non skier in the lodge who forgot his book and doesn't drink. Some lifts have PLCs with modems but they aren't designed to transmit info when the lift is running, too much electrical interference from the D.C. drives.

I think info about the wait times is helpful at large areas with many lift options. Where I work we occasionally post estimated waits based on timing one person's wait. Lifties wait for someone with an obnoxious ski outfit (unforgettable) to enter the line and you time them. The info is then phoned around to other lifts to be posted. An experienced operator can tell how long their line is at a glance.

Towers have simple derail switches that stop the lift if the rope jumps the sheaves. Others (detachables) also have proximity switches to monitor rope position. These will stop the lift if the rope moves out of center but before it jumps the sheaves.

This post has been edited by SuperRat: 23 October 2008 - 02:33 PM

[Peter]

Considering that Whistler's sign boards also have status lights for things like the Tube Park and each lodge, I think it is all done manually by a person.

[Aussierob]

All the Whistler Blackcomb signs are controlled from the dispatch office. Staff on the hill with radios call in the status every now and then it is updated on the board by the dispatcher. We used to have a system on some of the Blackcomb lifts that recorded a lot of lift data and put it on the computer network. Unfortunately the 2 guys who knew how it woked moved on to other things and we have removed it all from the lifts. Sorry Mitch.

[liftmech]

Copper used to have a switch on the bottom control panel that the liftie would turn to the approproate line wait, i.e. 0-10 minutes, 10-20, and 20-30. That was sent over the mountain phone system to all sign boards we had. The system was by all accounts finicky and has been gone for quite a while.

[mthornton]

Aussierob, on Oct 25 2008, 10:54 AM, said:

All the Whistler Blackcomb signs are controlled from the dispatch office. Staff on the hill with radios call in the status every now and then it is updated on the board by the dispatcher. We used to have a system on some of the Blackcomb lifts that recorded a lot of lift data and put it on the computer network. Unfortunately the 2 guys who knew how it woked moved on to other things and we have removed it all from the lifts. Sorry Mitch.

Hey, I left Whistler 11 years ago, and I understand nobody knew what happened to all the documentation when Jer left. So I can't imagine that any of it was still happening to do the basic file house-keeping. By the time I left, the skidac system boiled down to automated machinery temperature monitoring.
At Pano things are simpler, and have a portable setup for load-tests. Still very interrested in temp & vibration monitoring.

Rob, you blew it when you told the guy the lift-line status is controlled from dispatch. I was going to say that automatic pressure sensors were installed beneath the mazes, automatically compensating for snow/rain etc. Amazing!

Does anybody else out there also use sheep for load-tests? Each sheep weighs exactly 77kG! When it's done we stab em' with ski-poles and let em' drain as they go around. Big BBQ afterwards you know ;-)
M

[oceanwanderlust]

Hi All! Thanks for the helpful information so far!

The data I'm looking to gather is targeted at Resort and Lift Operations Managers, but some of it will probably be of interest to the general skier.

I'm mostly interested to figure out what data can be collected automatically from existing systems, so it sounds like lift line length is not possible for the moment.

I've generically pondered monitoring the temperatures, but what is interesting besides the air and maybe motor temperatures?

The fact that amperage can be used to infer lift utilization is very interesting! Do you think this information can be used to set a maintenance schedule?

Where would you be interested in measuring vibrations? Are there usually already multiple vibration sensors on a lift or is the vibration sensor only brought in for testing?

Is haul rope tension usually monitored, is this just set once and left?

How interesting would chair spacing be? I'm imagining that the lift's PLC knows exactly where each chair is when it reattaches to the haul rope.
If the position of the chair were then tracked historically, it should be possible to determine if a particular grip is weak. Am I on the right track?

I can't find any hits on skidac but would be extremely interested to know more about what it did and why it faded.

Right now, I've found some products by Rio Tech and by Irdam. Anyone have comments on these or pointers/comments on other ski lift data acquisition systems?


thanks

joe

[Kicking Horse]

Quote

Is haul rope tension usually monitored, is this just set once and left?

Far as I know the Haul rope tension changes depending on operation conditions. It's not just set and forgotten about.

[Lift Kid]

Umm, haul rope is constantly monitored and changed throughout operation. Have you have ever ridden a lift that has stopped, then when it was starting again, the chair dipped down and came back up? That is the tension system. The computer monitors the tension and adjusts it as needed. (i.e. more people on the lift means more tension needed)

[Allan]

Ok... I'm a bit tired and have a cold but...

The tension system on a lift is used to keep a constant tension on the lift - not to increase or decrease it. The lift responds to increased load by the carriage moving forward - which brings the lift back to its normal tension value. On a counterweighted system; there is no input from anything. On hydraulic tensioning - it's a series of pressure switches. That dip you feel on a start is most likely the lift equalizing itself with the tension system doing very little.

Sound right?

[mthornton]

Mitch Thornton (Panorama) comments below in blue

oceanwanderlust, on Oct 27 2008, 02:01 PM, said:

Hi All! Thanks for the helpful information so far!

The data I'm looking to gather is targeted at Resort and Lift Operations Managers, but some of it will probably be of interest to the general skier.

I'm mostly interested to figure out what data can be collected automatically from existing systems, so it sounds like lift line length is not possible for the moment.

The most useful quick-look is a graph showing rope-speed & load torque vs time. Both rope-speed and load tourque signals are generally very easy to pick off of any lift.
If logged with sufficient resolution, it's real easy to see every stop & slow. Skidac was a ski-lift data acquisition system that did this, with the info viewable at any PC connected to the companies network. You can use any data-logger to do this (like the Campbell Scientific CR1000), just make sure you know 100% what you are doing in terms of isolation from the signal source.

You can log stops, but I discovered that the lift-ops managers just don't want to know about this stuff. I've got a smart hour-meter that records every stop-start event including date/time.

I've generically pondered monitoring the temperatures, but what is interesting besides the air and maybe motor temperatures?
Motor bearings, Gearbox Oil, Machine-Room air, Control Cabinet Air
Motor bearings heat up real sudden when they fail, and an external temperature sensor very slow in responding. Gearbox Oil monitoring lets you know if your oil-cooler is working OK. A pre-meltdown hi-temp alarm is a nice idea, but pointless if it's not fast enough, or properly ennunciated.

The fact that amperage can be used to infer lift utilization is very interesting! Do you think this information can be used to set a maintenance schedule?
No. Better off with hours, start-count, laps, grip-cycles, are all much more relavent. If you put a power meter on each lift (any lift), kWh is directly proportional to people carried. (minus an offset, easilly figured on a very slow day)

Where would you be interested in measuring vibrations? Are there usually already multiple vibration sensors on a lift or is the vibration sensor only brought in for testing?
Usually vibration sensors are not permanently mounted on ski-lift equipment. (Our 3 800HP air-compressors have vibration monitoring as standard & essential machine-safety equipment.) I'm considering putting accelerometers on our largest lift ( a 800hp quad ) motor(2), gearbox & trending the data. More as an academic excercise. The motor is one of those 1200HP GE frames that I simply don't want to pull out. Getting the data will easy because I have a network connection in the drive-room. Logging vibration data requires very large amounts of memory, so I'll log it with a PC with a big disk-drive, located at the base.

Is haul rope tension usually monitored, is this just set once and left?

How interesting would chair spacing be? I'm imagining that the lift's PLC knows exactly where each chair is when it reattaches to the haul rope.
If the position of the chair were then tracked historically, it should be possible to determine if a particular grip is weak. Am I on the right track?
I built a little box to perform some simple statistical analysis on spacing. It located to bad rollers & loose belt, soft-tires. But that was when we were using 3rd party roller-wheels, and since we've reverted back to Doppelmayr roller wheels... there is rarely a broblem. The box eventually got blown up by lightning. Oh well.

Far more interesting is logging grip-force values (Off a Dopp Uni-G). I built a box that serial-spits out the grip-force value for each chair. It's really usefull as poor grips stick out like a sore-thumb, and then quickly get rebuilt. I import the data into excel and greate a graphic showing varience. It works very well. It has provided very useful feedback for the mechanics. I can provide more info if there is any interest. Too bad Doppelmayr doesn't do this in their PLC. The info available on their touch-screen is very minimal.

If you want to keep your lifts turning, don't neglect battery monitoring. Log the normal max/min (range increases as the batteries get old & weak). Also battery balance is very important (monitor both batteries in a 24V stack). I've got a smart voltmeter that does all this. mounts in a standard 1110 or FS electrical box. An audible alarm goes of if any single battery drops below 10V.

I can't find any hits on skidac but would be extremely interested to know more about what it did and why it faded.
I worked at Blackcomb & built Skidac per the wishes of Sr. management at tat time. When I left W/B development stopped, and that's not a bad thing. It was too complex & didn't maintain itself. It's present evolution is under development as a small portable system, much like an engine diagnostics computer that an auto-garage uses. Plugs into a standard connector for each lift. Good for load-testing, brake set-up, etc.

Right now, I've found some products by Rio Tech and by Irdam. Anyone have comments on these or pointers/comments on other ski lift data acquisition systems?


thanks

joe

[Jonni]

Lift Kid, on Oct 27 2008, 09:07 PM, said:

Umm, haul rope is constantly monitored and changed throughout operation. Have you have ever ridden a lift that has stopped, then when it was starting again, the chair dipped down and came back up? That is the tension system. The computer monitors the tension and adjusts it as needed. (i.e. more people on the lift means more tension needed)

Kind of, but not quite.

Allan, on Oct 28 2008, 12:14 AM, said:

Ok... I'm a bit tired and have a cold but...

The tension system on a lift is used to keep a constant tension on the lift - not to increase or decrease it. The lift responds to increased load by the carriage moving forward - which brings the lift back to its normal tension value. On a counterweighted system; there is no input from anything. On hydraulic tensioning - it's a series of pressure switches. That dip you feel on a start is most likely the lift equalizing itself with the tension system doing very little.

Sound right?

Yes.

IIRC (and others correct me if I'm wrong) I believe the dip that you experience on a lift when it starts is the result of the force of the motor pushing and pulling it's load up the hill through the cable. The reason this happens, (and usually only happens on a bottom drive lift), is that with a bottom drive the lift drive sheave (the bullwheel) is pulling the load up the hill by way of pulling on the down line against the top bullwheel. As the bottom bullwheel is pulling the down line, the up line goes a little bit slack momentarily causing the dip because the up side has not yet caught up to the force of being pulled up against the top bullwheel. Usually when this happens you'll notice that the downhill chairs tend to rise up a little bit while the up line dips down.

The reason you don't experience this dip with a top drive is that you have essentially removed one portion of that cause and effect out of the equation by putting the pulling force at the top rather than at the bottom. The top bullwheel is pulling its load up the hill directly, so it in turn doesn't have to pull its load against the opposite bullwheel like a bottom drive does.

Hope this helps.

[oceanwanderlust]

Wow, this is interesting!

Why do you discount logging stops? I think the highest initial value for a system like this would be to enunciate lift downtime and analyze response time.

Is there a difference (besides proportion + constant) between load torque, and kWh?

What could you learn from a rope-speed & load torque vs time graph? If you are just looking for starts and stops, a discrete measurement would be easier to analyze, IMO.

Is kWh really sufficient to calculate load? I'd imagine that a lift would use disproportionately more power at high speed than at low.

Do most lifts run off the grid and switch to diesel-generated electric when necessary?

Is there a common terminology used to describe states of a lift such as "beginner skier stop", "weather related (automatic) stop", "mechanical stop", "turning but not loading", "powered off", "weather related (manual) hold", etc?

What wireless networks work well on a snow covered mountain? I'm thinking a 900mhz mesh network from the back lifts or maybe even just standard WiFi on the ones closest to the lodge. From your experience, how bad does a major snow storm affect wireless networking?

thanks for the continued enlightenment!
joe

[oceanwanderlust]

liftmech, on Oct 26 2008, 08:16 AM, said:

Copper used to have a switch on the bottom control panel that the liftie would turn to the approproate line wait, i.e. 0-10 minutes, 10-20, and 20-30. That was sent over the mountain phone system to all sign boards we had. The system was by all accounts finicky and has been gone for quite a while.

How did this system utilize the phone system? Was the data simply voice or was it sent via a modem, or did it utilize the second unused pair of copper wires that most phone systems have? What was finicky / wrong with it?

joe

[mthornton]

oceanwanderlust, on Oct 30 2008, 12:20 PM, said:

Wow, this is interesting!

Why do you discount logging stops? I think the highest initial value for a system like this would be to enunciate lift downtime and analyze response time.
You might think so, but the lift managers were not interrested to learn that 98% of the stops were either operator stops, or else secondary stops (ie mis-starts due to operator error). Only 1 lift was monitored this way (Wizard), and then only for 1 year, as the tabulated results were met with outright hostility. A good lesson in human nature though... don't install an info system that provides information that people don't want to hear.

Is there a difference (besides proportion + constant) between load torque, and kWh?
Sure there is a difference.
Load tourque (measured in kNm) is calculated from the DC motor Arm-VoltsDC, Arm-CurrentDC (applied power), the rope-speed, and a constant (the radius of the drive bull-wheel). A bit of algebra on the horsepower-equasion, and you derive load-torque. An empy lift pulls 20-35% torque just overcoming friction, and varies somewhat with temperature. Emperical experience (data) will tell you how much torque a given lift is pulling at 100% load on a peak day (likely higher than during a load-test). The difference (30-100%) is directly related to how many people are sitting on the lift... regardless of rope-speed. Torque is torque.

AC Power (measured by a power meter in kWh)
The days accumulated kWh will be directly affected by rope-speed, but so is the number of people you move. So the end result is very similar to the more complicated method of using load-torque. It depends on the instruments you have available. Careful as your station heat & out-building loads may skew results.

At Pano we had a very accurate photo-eye people-counter setup (Mile-1 quad), and it's trend-data was exactly mirrored in both load-torque & power measurement.

Lesson : you likely only need to monitor via 1 method (if at all). The info is usefull for deciding if a lift is running at capacity & needs more (like adding carriers, other upgrade), or not.

What could you learn from a rope-speed & load torque vs time graph? If you are just looking for starts and stops, a discrete measurement would be easier to analyze, IMO.
You can see, at a glance, how well a lift is running (or not). You can immediately tell if the lifties were on the ball (letting the lift run full-speed & actually helping the skiers load/unload), or constantly stopping & slowing the lift (poor lifties sitting in the lift-hut, watching the skiers fall & just hitting buttons). Some lifties will not run a lift at 5.0m/s when it gets busy, because they actually have to hustle. The ops manager is interrested to know that the new high-speed quad (the one with the line-up) was only running at 4.2m/s when lifty-A was at the drive, and 5.0m/s when lifty-B. But often it's not the lifties fault, as it is really hard for a single lifty to load/unload some lifts at 100% capacity. The problem may be a staffing issue (need more/don't have).

Is kWh really sufficient to calculate load? I'd imagine that a lift would use disproportionately more power at high speed than at low.
Yes, a faster lift uses more power, and moves more people. We run our quads at 4.2 when it is not busy, and speed them up to 5.0 when it gets hoppin'

Do most lifts run off the grid and switch to diesel-generated electric when necessary?
In much of N.A., grid supplied electricity is generally much cheaper that diesel. Some places have limited available electrical demand, or else pay an extremely high demand penalty. In BC, electric power is very cheap wrt diesel, so diesel is only for evac drives. Some hills have a diesel standby drive, for normal operation via diesel. Nice for power-outages. Wires are a really cheap way to deliver bulk energy. Some ski areas have excellent & reliable Epower, other have very terrible Epower.

Is there a common terminology used to describe states of a lift such as "beginner skier stop", "weather related (automatic) stop", "mechanical stop", "turning but not loading", "powered off", "weather related (manual) hold", etc?
only 2 categories : Operator-generated-stop - skier load/unload error (includes secondary stops (anti-collision due to op-error on startup)), or non-operator stop (maintenance attention due). ratio = 98% / 2%

What wireless networks work well on a snow covered mountain? I'm thinking a 900mhz mesh network from the back lifts or maybe even just standard WiFi on the ones closest to the lodge. From your experience, how bad does a major snow storm affect wireless networking?

thanks for the continued enlightenment!
joe

Final comment
By the time you go through the procedure of designing & installing a monitoring system on a ski-lift, you have had to perform a very detailed analysis of that lift's control & drive systems, you gain a deep understanding of the workings of the machine... and in the process have likely resolved numerous questons/issues/problems directly relavent to the smooth, reliable & safe operation of a lift. An elegant design appears very simple in the end. Avoid unnecesarry complexity.

[Lift Dinosaur]

mthornton-
Thank you for following this thread. Your input is very insiteful to us mechanics and Dinosaurs!!

Dino

[Aussierob]

Nice work Mitch, this is right up your alley. I could further this topic by moving on to the definifition of a Mitchism, but maybe thats for another thread.

[liftmech]

oceanwanderlust, on Oct 30 2008, 12:19 PM, said:

How did this system utilize the phone system? Was the data simply voice or was it sent via a modem, or did it utilize the second unused pair of copper wires that most phone systems have? What was finicky / wrong with it?

joe

We have many unused pairs in the mountain phone system; thus there were dedicated pairs from each lift. I'm not exactly familiar with the system as it was removed from service before I started here. It was neither voice nor modem, simply a signal sent down the wires. One pair was for the 'no-wait' light, one more for the medium, and so on.

We don't log what Mitch refers to as 'operator-generated' stops. Some lifts have none in a day, others may have up to a hundred. We have a detailed log sheet, however, for lift breakdowns. It logs time dispatch is notified, time maintenance is notified, time maintenance is on scene, and time lift is back up and running. It also notes what sort of problem it is, whether it's mechanical or electrical, what subsystem, and so forth. Every month one of our supervisors distills all these sheets into a 'downtime report' which we use to try and eliminate our stops and maintenance issues. It's great to identify trends and such.

[oceanwanderlust]

mthornton and all, thankyou for your help! My project got approved!!!!

Some notes, so I can start contributing back to this community:

1) Wet bulb sensors will be very useful; where can I make snow?

2) Operator generated stops are of interest for now.

3) Communication over existing copper can be done with DSL