19 replies to this topic

[liftmech]

Somewhere in the vast morass that is this board, there was a discussion of how lift computers 'know' speed and distance travelled of the haul rope. Here are a couple photos of the speed sensors on the Flyer.
First one is of the cable tach; as you can see there are two sensors for a more accurate reading and redundancy.
Second is the same photo but with a flash so I could 'stop' the tach sheave. Notice the discs on the sheave hub; these are what the sensors key off of.
Third photo is the PTO tach. The computer constantly compares this with the cable tach and stops the lift if the two don't agree. This is to prevent a massive pileup of chairs if the triple chain were to break and stop driving the conveyor PTO shafts.
I didn't take a photo of the motor tach because it's hard to tell what it is no matter how good the photo. The computer also compares this with the cable tach, both to adjust the SCR firing for drive speed and to shut the lift down if the two don't agree. This could be because of a gearbox or driveshaft failure or drive/motor problem.

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•  cable_tach_in_motion.jpg (90.87K)
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•  cable_tach_caught_with_flash.jpg (111.15K)
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•  O_1_cadence_tach.jpg (97.55K)
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[Aussierob]

liftmech, on Mar 27 2005, 06:00 AM, said:

First one is of the cable tach; as you can see there are two sensors for a more accurate reading and redundancy.
<{POST_SNAPBACK}>

Doppelmayrs have two sensors arranged in quadrature to sense direction. The lift will shutdown on a fault if either fail. They install a "bullwheel" tach on the bullwheel to measure cable speed and compare this to the motor tach and the impulse prox's.

[Duck]

That'll be the reason for the two prox switches with single target in liftmech's photos - to get direction as well as speed.

-Iain

[Mike]

budfischer, on Mar 27 2005, 02:08 PM, said:

...no-contact laser type sensors ... able to look directly at the rope...<{POST_SNAPBACK}>

These can be nice to use if they work 100% of the time (They have to work with ice/snow on the rope, oil, etc on the rope). The proxy sensors that are shown in Liftmech picture are also used for the anti-collision system and (if tire turnaround) spacing system. If the measurement isn't 100%, the chair spacing will be screwed up. One problem with the current way poma and dopp measures haulrope length (which is used for spacing) is the sheave changes diameter with temperature. This screws up the haul rope length measurement and screws up the chair spacing. If you had some accurate linear measurement device, you can get rid of these issues. I know poma has looked into similar technologies but hasn't found anything that worked reliability.

[Allan]

Motor Tach: The little tube like object coming off the back of the electric motor.

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•  MotherLode___Electric_Prime_Mover_400hp.JPG (198.86K)
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[Aussierob]

The change in impulse sheave diameter is not usually a problem unless there is something else in the system thats causing a problem as well. On our lifts, if you look at the spacing error first thing in the morning you notice that most chairs are quite "late". One the lift has done a revolution or two they are all back in place as the sheave liner has come to it's "running" diameter.

[liftmech]

Any lift that has a fixed terminal versus a moving carriage will do that first thing in the morning, since the haul rope has shrunk in the cold overnight temps and pulled the carriage forward. This makes the distance from the bullwheel to the end of the terminal larger. Our Omegas don't do that as the whole terminal moves as the carriage.

[Mike]

Aussierob, on Mar 27 2005, 09:02 PM, said:

The change in impulse sheave diameter is not usually a problem unless there is something else in the system thats causing a problem as well. On our lifts, if you look at the spacing error first thing in the morning you notice that most chairs are quite "late". One the lift has done a revolution or two they are all back in place as the sheave liner has come to it's "running" diameter.
<{POST_SNAPBACK}>

I do agree that the sheave diameter change doesn't screw the lifts up too much (except our quicksilver). Dopps have a space at the end of the line to compensate for the sheave diameter difference. Most lifts don't care if there is a slight difference but it does change slightly. Poma was looking into a linear encoder for quicksilver because the spacing is so critical with that lift.

[liftmech]

Is that space what's called the 'end gap'? The one time I skiied Vail chair 3 (CTEC detach) was closed becase the end gap was too big, and my counterparts were just having the lift do laps to close it up. It was about 0 degrees Fahrenheit that day, too.

[Mike]

liftmech, on Mar 29 2005, 05:42 AM, said:

Is that space what's called the 'end gap'?...<{POST_SNAPBACK}>

Yep. The end gap is required for (older...don't know about new) dopps spacing system because they space chair-chair. What that means is there is a number that is set via thumbwheels that tells the "computer" how far apart the chairs need to be. The "computer" tries to make the gap between the chairs whatever the number is set to. It doesn't have provisions for haulrope length changes or sheave changes. The system has to be set up so there was a gap at the end to allow the chairs to be spaced under the worst case scenario. Poma's system measures the haul rope length each lap and divides it by the number of chairs online. This calculated distance is what the system tries to space the chairs.

[barnstormer]

liftmech, on Mar 29 2005, 08:42 AM, said:

Is that space what's called the 'end gap'? The one time I skiied Vail chair 3 (CTEC detach) was closed becase the end gap was too big, and my counterparts were just having the lift do laps to close it up. It was about 0 degrees Fahrenheit that day, too.
<{POST_SNAPBACK}>

CTEC's fine spacing is all set off of chair number 1. This chair has a special target that is seen by the spacing prox. All the rest of the chairs are spaced a certain distance behind chair 1. The end gap is a somewhat variable sized space between the last chair and chair 1. It is usually at least 1/3 longer than a normal space. This is where any variation for rope stretch goes.

Not sure how the end gap being too big would be a problem. And as far as the temperature goes, that should have made the end gap smaller.

[Mike]

barnstormer, on Mar 29 2005, 10:58 AM, said:

Not sure how the end gap being too big would be a problem.  And as far as the temperature goes, that should have made the end gap smaller.
<{POST_SNAPBACK}>

I agree...big gap shouldn't be a problem...I would think they could just run a lap w/ bottom spacing at slow speed to fix spacing.

[liftmech]

Just telling you what I remember. That was the first year I had ever worked on detachables so I pretty much took anything I was told as gospel Cold should make the end gap smaller, true, but that's what they told me.

[Aussierob]

Mike, on Mar 29 2005, 07:40 AM, said:

Yep.  The end gap is required for (older...don't know about new) dopps spacing system because they space chair-chair.  What that means is there is a number that is set via thumbwheels that tells the "computer" how far apart the chairs need to be.  The "computer" tries to make the gap between the chairs whatever the number is set to.  It doesn't have provisions for haulrope length changes or sheave changes.  The system has to be set up so there was a gap at the end to allow the chairs to be spaced under the worst case scenario.  Poma's system measures the haul rope length each lap and divides it by the number of chairs online.  This calculated distance is what the system tries to space the chairs.
<{POST_SNAPBACK}>

Ummm..No.. Our oldest Doppelmayr (with clutch spacing) is an '89 and it does not space chair to chair. It does space chair to chair if you are doing a rough space from the return station. The precision spacing system has a haul rope length inputted via jumpers. The system then runs a "stroke" counter and spaces every chair relative to the "stroke" counter. This allows you to remove a chair and still operate the lift. The gap at the end is just the left over space on the line to allow for a little fudge factor. The distance between chairs is set by the thumbwheels, but the spacing is not chair to chair. Read Doppelmayrs "electrical description" that comes with the lift for the full explanation. :)

[Aussierob]

Hey Mike,
Following on from our discussion abot grip force checks, you will be interested to learn that the Canadian code has just been changed so that now "The ability of each grip to produce the required grippping force shall be checked before each coupling." I guess that means Doppelmayr will have to change their system to check on the incoming side.

[Mike]

Aussierob, on Mar 30 2005, 11:44 AM, said:

...The distance between chairs is set by the thumbwheels, but the spacing is not chair to chair...<{POST_SNAPBACK}>

Ok, I guess I didn't say what I meant correctly...sorry. The space between each chair is a fixed number set via thumbwheels. It is a fixed number that is the same no matter what the haul rope does. The spacing is calculated by measuring the distance from chair 1 and comparing it to the number set by the thumbwheels. Everytime a chair (or gap if a chair is offline) goes through, it adds whatever the thumbwheel number is and compares it to the distance from chair 1. It uses the calculated number to determine how much to adjust the chair. Since the chair space is a fixed number, it doesn't care what the haul rope does (as far as expanding or contracting) and the gap at the end is to compensate for these changes in haulrope length.

[Mike]

Aussierob, on Mar 30 2005, 11:51 AM, said:

I guess that means Doppelmayr will have to change their system to check on the incoming side.
<{POST_SNAPBACK}>

Can you check the dopps grip that lock open while they're in the terminal? Since the grip is open the whole time it's in the terminal, grip force can't be measured the same way poma does it. The only way to properly measure it is while closing the grip and that is done on the outgoing side. I guess they could measure how much force it takes to open but I don't see that being very accurate.

[liftmech]

On the DS grips with the grip guage it shouldn't be too dificult to move the brittle bar and associated mounting brackets to the arrival side since the guage only moves if you lose washers. It doesn't matter if the grip is open or closed.

[Mike]

liftmech, on Apr 1 2005, 05:48 AM, said:

On the DS grips with the grip guage it shouldn't be too dificult to move the brittle bar and associated mounting brackets to the arrival side since the guage only moves if you lose washers. It doesn't matter if the grip is open or closed.
<{POST_SNAPBACK}>

How about the dopp grips that actually measure force (I think they use torsion bars instead of washers). The DS grips shouldn't be a problem like you said.

[Aussierob]

Fortunately none of the lifts with DS grips will need to be changed. Only new installations will need to comply with the code change. It may be possible to interpret the rule so that the grip check on the outgoing side of one station functions as the incoming grip check at the other.