36 replies to this topic

[liftmech]

floridaskier, on Mar 15 2005, 06:42 PM, said:

Is there any benefit to having a single (or double) position grip?
John, which Doppelmayr grip are you referring to? The new coil spring one is a single position, and the new torsion bar one is a double, just like the DT-104
<{POST_SNAPBACK}>

There are benefits to both. Double-positions, as Barnstormer mentioned, open and close half as much as single-actions. This can be a benefit on a shorter lift that has more cycles (trips around the line) per carrier. Single-position grips have less parts and a simpler compression rail setup. You pays you money, you takes you chance.

I did mention the new coil spring grip being single position.

Some clarifications: DS-104 = Doppelmayr Spring (washer) quad carrier. DT-104 = Doppelmayr Torsion (bar) quad carrier. There are also -103, -106, and -108 grips. I forget what they call the new single-position coil-spring grip.

[highspeedquad]

What is the force difference between double and single position grips?

[floridaskier]

Is this the new Doppelmayr one you're talking about? They have an identical version of the torsion bar grip that looks the same, minus the springs, presumably so they can build the same type of terminal only changing the depression rail in each installation. I have a feeling they'll drop one type in the future

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•  ss_grip.jpg (32.87K)
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[barnstormer]

highspeedquad, on Mar 16 2005, 07:05 PM, said:

What is the force difference between double and single position grips?
<{POST_SNAPBACK}>

"Grip force" on a detachable is a funny thing. First of all, it's not really grip force that is messured, at least far as I know, it's spring force. On a Garaventa/CTEC, the grip springs are tested against a strain guage every revolution. It's value is compared to a relative number generated at load test and then annually after that. If a grip fails significantly above or below that relative number, the lift stops and the grip is inspected by a mechanic. Poma TB type grips use a similar scenario only they have a limit switch.

Every Garaventa AK 4 needs to be tested on a jig for actual grip slip on a tri-annual basis. That value is calculated based on the lift specs just like a fixed grip. Comparing one manufacturer' grip to the next for grip force would be like comparing apples to oranges.

[highspeedquad]

Alright, that is kind of what I meant.

For the Doppelmayr torsion bar I think that the grip you showed us floridaskier has something added, like a small box, to replace the springs to apply force. I also think that in newer Dopp torsion bars the closed position is as far down as it can go, and open is as far up.

[liftmech]

Not having any DT grips, I don't know how grip force is measured there. On the DS grips there is a black plastic dog that engages a brittle bar if enough washers fail. There is a secondary spring pack behind the primary that forces the dog into a different position when the primary washers fail. In this pic you can see the linkage above the dog; it's the white plastic with a notch cut into it.

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•  DS_104.jpg (59.64K)
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[highspeedquad]

How would the mechs know if the brittle bar had been broken?

[edmontonguy]

The lift shuts down automatically when a brittle bar is broken.

[highspeedquad]

So the grip just sends out a signal to the terminal if the bar breaks? It seems that the mechs would have a problem figuring out which grip tripped the system.

[Aussierob]

When the grip leaves the station it passes over the brittle bar which points vertically up. The brittle bar is mounted in the station in a holder right where the grip leaves. If the secondary spring pack on the grip engages it moves the swivel dog down and it hits the brittle bar instead of passing over it. The lift shuts down and the first carrier out of the station is the problem. Very simple, Very reliable.

[Aussierob]

DT grips use a deflection rail which is part of the compresssion rail. A linear proximity switch measures the deflection caused by the force of the operating arm acting in an upward direction. If the grip force is weak the deflection rail doesn't move far enough and the lift shuts down. Its pretty much the same as the Pomas. The newer Doppelmayrs use 2 proximitiy switches and the older ones use one.

[highspeedquad]

Oh, okay. I thought that from the first description it was in the grip itself. That makes a lot more sense. (I'm a little tired)

So the deflection rail and linear proximity switch test the grip force along with the brittle bar/plastic dog like the grip force detectors in the attach/detach rail on single-position grips?

[Doppeldork]

Break fork/Plastic dog Is the grip force indicator on a DS grip(cup spring grip)
A Deflection rail is used to measure the grip force on a DT grip(torsion bar grip)

[Aussierob]

Here's a couple of pics of the Doppelmayr DS grip force setup. In the terminal shot, the the brittle bar pointing up is what gets broken to trip the grip force. In the grip picture, the black "dog" just above the blue Doppelmayr sticker is rotated down if a spring or springs are broken, indicating low grip force. If a grip lands on a tuck in the haul rope, the grip will close too far and that will cause it to trip as well.

Hope thats clearer. :)

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•  Excel_grip.JPG (230.27K)
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•  Excel_switches.JPG (210.97K)
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[highspeedquad]

Yes, it is very helpful.

What is a tuck?

[Aussierob]

As this thread has morphed topics a couple of times already I'll start a new one. :D

[Aussierob]

Better idea, there are already a couple of topics on this. Try

http://www.skilifts....?showtopic=1881