Gemini Rescue Equipment

Gemlok (a.k.a. J-Lock)

Closed For Use

Opened For Rigging

Technical details:

The Gemlok has four fixed bollards and one moving bollard. The fixed bollards are bolted to an aluminum back plate and pinned so that they cannot rotate. A face plate pivots on the lower bollard. Three notches in the face plate engage grooves in the remaining three fixed bollards when the face plate is closed The top notch has a milled cutout on the inside that is engaged by a spring-loaded catch mounted in the upper bollard. This keeps the face plate from opening in use. A button in the upper bollard activates the catch. The top, second and bottom fixed bollards are grooved to keep the rope centered, while the third one is cylindrical. The top bollard is polished stainless steel, the others appear to be parkerized.

The moving bollard is mounted (with two machine screws) on a lever that pivots on a bolt through the back plate, beside the third fixed bollard. A slot in the lever provides clearance for that bollard. Raising the lever causes the moving bollard to move away from the middle two fixed bollards. The moving bollard is grooved, but the groove is eccentric, i.e., it is not concentric with the bollard. The deepest portion of the groove is on the side toward the lever, where the rope does not contact the bollard.

The lever has a soft plastic handgrip.

Comments:

At first glance the Gemlok looks like it is a stop bobbin, but it isn't. The rigging is different and the lever does not work the same way.

The rope is rigged by snaking it from right to left between the top two bollards, to the left of the second one, around the moving bollard, and then out between the two bottom bollards, leaving the device on the side opposite the lever. As simple as this is, an illustration stamped on the device helps remind the uncertain. Optionally, one can skip using the top bollard if less friction is desired.

I find that raising the lever to go and squeezing it to stop takes a bit of getting used to, since almost everything else (cf. stop bobbins) works the other way, but it makes some sense. If the user panics (a foolish thing to do, by the way, and not recommended) and squeezes the handle, the moving bollard will act as a brake to stop the descent. Similarly, if the mindless user lets go of the lever, the brake is also activated.