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Sugarloaf Rollback 3/21/15


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#21 SkiDaBird

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Posted 22 March 2015 - 11:06 PM

King Pine was mentioned by someone on I think the 2013 thread as up for replacement. Would this prompt Sugarloaf to actually replace it?
I did see someone saying the lift will be fine and I don't doubt that. Just food for thought.

#22 Peter

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Posted 23 March 2015 - 05:16 AM

View PostRibStaThiok, on 22 March 2015 - 09:20 PM, said:

actually the Eskimo Riblet destruction testing used concrete blocks.. but still. Based upon what I could see on the videos, I'd guess they were rolling back at most.. maybe 200-300 FPM?


The videos only show the end. Look at the pictures of the damaged chairs that went around the bullwhweel. Chairs were swinging violently enough to hit towers. Seems to me it got going somewhere around detachable speed though not for very long.
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#23 machskier

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Posted 23 March 2015 - 05:23 AM

View PostPeter, on 23 March 2015 - 05:16 AM, said:


The videos only show the end. Look at the pictures of the damaged chairs that went around the bullwhweel. Also chairs were swinging violently enough to hit towers. Seems to me it got going somewhere around detachable speed.


I'm not buying that on line speed. My thought on the chair swing is that some may have been caused by the swing off bull wheel but I think most is from jumping riders from the end of the chair. Watch the video, the normal uphill line now downhill has chairs swinging pretty good and this was from jumpers. You can see one chair with a single rider at the end of the chair and it is severely canted out of center. If he were to jump, that chair would start swinging pretty good. Not seeing the chairs coming around the base bull wheel, I hate to elevate on cause of swing. Some of the chairs that went around were not even swinging.

#24 Peter

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Posted 23 March 2015 - 05:41 AM

You can see in this picture King Pine appears to have a hand brake pump. I would like to know where in the 9 chair lengths the operator hit the E-stop. I think lift operators sometimes get the impression from maintenance that they should never use the E-stop. Having to manually pump the brake back up might further discourage an operator from using it.

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#25 Peter Pitcher

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Posted 23 March 2015 - 05:56 AM

View PostPeter, on 23 March 2015 - 05:41 AM, said:

You can see in this picture King Pine appears to have a hand brake pump. I would like to know where in the 9 chair lengths the operator hit the E-stop. I think lift operators sometimes get the impression from maintenance that they should never use it. Having to manually pump the E-brake back up might further discourage an operator from using it.

Where I come from the E-brake, sometimes referred to as a bullwheel brake, applies automatically at the very beginning of reverse rotation regardless of whether the operator attendant pressed the e-stop button, sometimes called the emergency shutdown. We assume that the operator is incapacitated.

#26 Peter

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Posted 23 March 2015 - 06:07 AM

View PostPeter Pitcher, on 23 March 2015 - 05:56 AM, said:

Where I come from the E-brake, sometimes referred to as a bullwheel brake, applies automatically at the very beginning of reverse rotation regardless of whether the operator attendant pressed the e-stop button, sometimes called the emergency shutdown. We assume that the operator is incapacitated.


Same as where I come from but obviously that did not happen so the attendant's actions and timing mattered a whole lot.
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#27 Sotto

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Posted 23 March 2015 - 07:22 AM

View Postvons, on 22 March 2015 - 02:34 PM, said:

Its been mentioned that Borvig used a drop dog roll back device anyone know what kind of system was used to deploy it? I am only familiar with the Yan mousetrap setup.


Borvig uses an under speed switch with a wheel the rides under the brake ring on the bullwheel. If it detects the the bullwheel is moving under a set speed it removes power to a solenoid and drops a dog that rides around the inside of the bulwheel.

#28 RibStaThiok

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Posted 23 March 2015 - 08:53 AM

I'm just very grateful there were no fatalties.
Ryan

#29 aimbrig

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Posted 23 March 2015 - 09:13 AM

Here is another article. http://bangordailyne...-lift-accident/
If it has vertical, put a lift up it.

#30 liftmech

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Posted 23 March 2015 - 10:25 AM

View PostPeter, on 23 March 2015 - 05:41 AM, said:

You can see in this picture King Pine appears to have a hand brake pump. I would like to know where in the 9 chair lengths the operator hit the E-stop. I think lift operators sometimes get the impression from maintenance that they should never use the E-stop. Having to manually pump the brake back up might further discourage an operator from using it.

We train operators *when* to use the e-shutdown, not to never use it. We stress that it's unnecessary to use it for ramp crashes. I can't speak to how Sugarloaf trains but most of the places I know of are the same as us.
Member, Department of Ancient Technology, Colorado chapter.

#31 Peter

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Posted 23 March 2015 - 11:57 AM

The news articles are riddled with comments to the effect of "Sugarloaf's lifts are so old and scary."

I was curious so I ran the numbers. Of the 2,356 lifts operating in the US, the average age is 34.4 years (in other words built in 1981.) Sugarloaf's lifts are newer than average at 31.5 years.
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#32 SuperRat

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Posted 23 March 2015 - 02:32 PM

View Postmachskier, on 23 March 2015 - 05:23 AM, said:

I'm not buying that on line speed. My thought on the chair swing is that some may have been caused by the swing off bull wheel but I think most is from jumping riders from the end of the chair. Watch the video, the normal uphill line now downhill has chairs swinging pretty good and this was from jumpers. You can see one chair with a single rider at the end of the chair and it is severely canted out of center. If he were to jump, that chair would start swinging pretty good. Not seeing the chairs coming around the base bull wheel, I hate to (elevate?) on cause of swing. Some of the chairs that went around were not even swinging.


The sudden unloading of chair contributed to the instability of the chairs but the extreme line speed was the main cause of the violent chair swing on the "downhill" side. Look at the extreme swing of the chairs exiting the bull wheel in the Eskimo Destructive Rollback Test. Those chairs experienced no sudden unloading prior to entering the bull wheel. King Pine would've experienced the same chair swing as the speed exceeded 500 fpm, as the speed slowed the last chairs should've made it around without much swing.

This post has been edited by SuperRat: 23 March 2015 - 02:33 PM


#33 SuperRat

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Posted 23 March 2015 - 02:38 PM

View PostPeter, on 23 March 2015 - 05:41 AM, said:

You can see in this picture King Pine appears to have a hand brake pump. I would like to know where in the 9 chair lengths the operator hit the E-stop. I think lift operators sometimes get the impression from maintenance that they should never use the E-stop. Having to manually pump the brake back up might further discourage an operator from using it.


I hope the King Pine operator realized pumping up the e-brake was the least of his worries when he saw loaded chairs coming back at him at 1000fpm. ;)

#34 Conrad

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Posted 23 March 2015 - 06:24 PM

Here's an image showing the controls:

Posted Image

View PostSkiDaBird, on 22 March 2015 - 11:06 PM, said:

King Pine was mentioned by someone on I think the 2013 thread as up for replacement. Would this prompt Sugarloaf to actually replace it?
I did see someone saying the lift will be fine and I don't doubt that. Just food for thought.


There has been talk for years about replacing King Pine. They are basically just waiting for the for the financing from higher up.

For most of the time, the plan has been to replace King Pine with a Skyline-like lift that has a loading carpet and heavier chairs. The path would be realigned. Then the old lift would be moved to replace the Double Runner chairs.

Watch this video at the 52:49 mark to hear more about those plans:
https://youtu.be/E9up9NJdys8?t=52m49s

#35 barnstormer

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Posted 25 March 2015 - 05:33 AM

View PostJHappel, on 22 March 2015 - 04:44 AM, said:



Correct me if I'm wrong but for all intents and purposes Partek and Borvig are one in the same.

Though there are some engineering and familial connections, saying that a 1988 Borvig and a 2014 Partek are the same, would be like claiming a 1988 CTEC was the same as a 2014 Skytrac. There are engineering and personnel connections with those two companies as well.

Technology marches forward. Modern Partek drive terminals use a fully electrified, battery backed-up, brake system including redundant rollback sensing devices to automatically deploy the bullwheel brake within inches of detecting a rollback. The control system is a PLC over relay based system that provides self checking, actual rope movement, monitoring.

#36 william b

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Posted 25 March 2015 - 06:37 AM

View PostPeter, on 23 March 2015 - 11:57 AM, said:

The news articles are riddled with comments to the effect of "Sugarloaf's lifts are so old and scary."

I was curious so I ran the numbers. Of the 2,356 lifts operating in the US, the average age is 34.4 years (in other words built in 1981.) Sugarloaf's lifts are newer than average at 31.5 years.



Please check your pm.

wbl

#37 Peter

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Posted 25 March 2015 - 04:06 PM

Quote

MEDIA ADVISORY: Sugarloaf Rollback Investigation Reveals Apparent Lift Design Issue

MARCH 25, 2015
CARRABASSETT VALLEY, ME - A team of investigators, including Sugarloaf personnel, engineers from Boyne Resorts (Sugarloaf's parent company), and a licensed Maine lift inspector, have completed a preliminary review and investigation of the rollback of the King Pine Chairlift on Saturday , March 21, 2015.

Investigators determined that a fracture of the main drive shaft of the lift's secondary gearbox initiated the rollback, and that the lift's bullwheel brake engaged and operated properly.

Investigators also identified an apparent manufacturer design issue in one of the lift's components as contributory to the accident.

Sugarloaf and Boyne engineers have also identified a retrofit for the system that corrects the issue.

"Our first thoughts remain with those injured, and our sincere hope is for their speedy recovery," Sugarloaf General Manager John Diller said. "I'm grateful that we now have a clearer understanding of what occurred."

Gear Box Failure:

The incident on King Pine occurred at approximately 11:30 Saturday morning, when a shaft in one of the two gearboxes that transfer power from the lift's electric motor to its bullwheel fractured.

The gear boxes in the King Pine lift, along with every other lift at Sugarloaf, were subjected to a routine vibration assessment by an outside contractor the day before the incident, and no anomalies were detected that indicated such a fracture was imminent or likely.

The fracture of the shaft resulted in the loss of both the primary service brake and the anti-reverse brake, leaving two additional braking systems intended to prevent a rollback.

The failure of the shaft, in and of itself, should not have resulted in the rollback that occurred, if the lift's remaining systems had performed as intended.

Bullwheel Brake Activation:

Though further investigation is still needed, findings suggest that an automatic system to activate the lift's bullwheel brake (identified as "emergency brake" in previous statements) activated properly. Additionally, the lift's operator quickly activated a manual control to apply the bullwheel brake.

Bullwheel brake activation is, by design, not instantaneous, because an immediate stop of a moving lift can create sudden and dramatic movement along a lift's haul rope, potentially causing enough movement to cause skiers to fall out of chairs, a deropement of the lift, and other significant damage.

In the time between bullwheel brake activation and the actual stoppage of the lift, the lift traveled backwards for a total of nine chair lengths, or approximately 460 feet, due to the weight of skiers on the lift, which was full.

The investigators also found that a further system to prevent a rollback failed, due to an apparent design flaw.

The Drop Dog:

The final system intended to automatically engage to prevent a lift rollback is commonly referred to in the ski industry as a "drop dog." Lifts are required to have some form of device to prevent the lift from counter-rotating, and variants of the drop dog approach are generally used today.

The investigation revealed that one of the switches used in the safety circuit connected to the drop dog was an inappropriate switch for the intended application. This switch, which is designed to suspend the drop dog above the bullwheel when it senses forward rotation of the lift, can also suspend the drop dog when the lift rotates in reverse.

This switch was provided by the lift's original manufacturer, and is still provided by the company that manufactures components for this type of lift.

The investigation indicates that, had an appropriate switch been included in the system, the drop dog would have deployed and the rollback would have stopped immediately.

Sugarloaf personnel and Boyne Resorts engineers, along with a licensed Maine lift inspector, have designed circuitry to correct this situation. This modification has been reviewed and approved by the State of Maine, and is being installed on other lifts at Sugarloaf that employ the same type of switch.

There are six such lifts at Sugarloaf - Skidway, Sawduster, Snubber, Double Runner East, Double Runner West, and Bucksaw. Upon reaching the above conclusions regarding the drop dog switch this morning, and acting on an abundance of caution, Sugarloaf personnel made the decision to temporarily shut down the Skidway, Sawduster, Snubber, and Double Runner lifts until the modification was installed. The Bucksaw lift was not scheduled to operate today or tomorrow and will be modified before it is operated again on Friday.

Sugarloaf and Boyne Resorts have been in touch with the lift's parts manufacturer to share their findings.

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#38 cordury joe

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Posted 25 March 2015 - 05:16 PM

Nine chairs seems like a flow control adjustment issue if the brake applied automatically. The drop dog switch should lift the dog at 150' to 200' feet per minute. It seems unlikely the lift could accelerate to that speed in the distance between the blocks the dog acts upon. The speed switch is adjustable.
Corduroy Joe

#39 barnstormer

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Posted 25 March 2015 - 05:37 PM

Interesting, not all those lifts on that list are Borvigs...

#40 ceo

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Posted 25 March 2015 - 06:26 PM

I'd think the bullwheel brake ought to have stopped the rollback in less than 9 chair intervals. A normal stop takes less than one. Am I completely off base here?

The business with the drop dog retracting when it senses reverse movement would be hilarious if it weren't terrifying. Good on them for fixing that immediately on all lifts with the problem. Sawduster and Bucksaw are Stadelis, the rest are Borvigs. I conjecture that the requirements for the drop dog switch is one of those things that's highly variable by jurisdiction, so it's something that gets put in by the installers, meaning it's likely that lifts by different manufacturers will have the same part.

I'm surprised Timberline isn't on the list; it's identical to King Pine. Both were originally installed the same year, but Timberline was moved to its present location on the summit ridgeline a few years later.

This post has been edited by ceo: 25 March 2015 - 06:30 PM






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