Home : Technical : Detachable Lifts : Facts & Figures : Detachable Grips Gripping

Detachable grips gripping:
All grips have a spring as source of energy to grip the haul rope. The spring source could be rubber, cupped washers, coil springs from the front suspension of a Chevy truck, etc. On some grips you may not see the spring system because of an exterior housing that protects the springs from weather and dirt contamination.

A simple explanation is to imagine a pair of scissors; the pointy end grabbing the rope- and your hand acting as the spring force to pivot the blades to grab the rope.

Detailed explanation - As the grip enters the terminal they:

• Are captured by tapered guides
• Springs are compressed
• The grip jaws open away from the haul rope
• Grip is decelerating
• Grip is raised above or to the side of haul rope
• The spring is released
• Grip jaws close
• Grip is moving to position itself in conveying system guide track(s)
• Grip is matched to conveying system speed
• Grip is captured by conveying system
• Grip is conveyed to other side
• Springs are compressed
• Repeat as necessary

Needless to say detachable lifts are high maintenance items.
See other topics on detachables and YAN grips for added information.

Poma's Detachable grips:
Poma's grips have never locked open in the terminal as far as I know. Doppelmayr likes to have his grips lock open ('over-centre') for some reason, and CTEC does the same. All grips, regardless of manufacturer, have at least a few pounds of pressure in them even when they're not on the rope. Otherwise, they'd flop around a bit too much and not have any tolerance for rope shrinkage or grip wear. There is also the 'little metal rod' sticking out farther when the grip is on line. That's called the 'spring guide rod' (at least on Poma TB-41s) and it is attached to the top spring cap. Say the rope is 41mm (hence the 'TB-41') then the grip closes to 41mm online and less in the terminal- so the springs are extended more in the terminal than on line.

Doppelmayr's Detachable grips:
No, there is no spring keeping the grip open. Rather, the linkage between the mobile jaw (the part that moves) and the spring guide rod has a slot in it that allows the linkage to sit in one of two positions. The bottom of the mobile jaw has a spur that is pushed up and back by a plastic track in the terminal, and that locks the grip in the 'open' position. When the grip moves around to the other side, the track does the same thing only this time it is to the 'closed' position.