|Front View: Closed||Rear View: Closed|
|Front View: Open for Rigging||Rear View: Open for Rigging|
I acquired this pair of ascenders from Mountain Gear in 2007. I acquired another pair in 2017 as part of Bob Thrun's collection.
The Black Diamond nForce is 194 mm. tall, 105 mm. wide, 33 mm. thick, and weighs 182 g.
The Black Diamond nForce ascender shell consists of a number of parts. The main piece is an anodized 4 mm. aluminum stamping which forms the rope channel, the upper portion of the ascender, and the front strap on the side of the hand hole opposite the hand grip. A reinforcing rib stamped into this piece reinforces the rope channel and front strap. A 16 by 19 mm. hole through the top part of the rope channel provides an upper sling attachment point.
The cam is mounted on the upper shell using a special 8 mm. shoulder bolt and special nut. The nut is center punched on the back side of the ascender to keep the bolt from unscrewing. A cam spring mounted on this bolt tends to close the cam. This spring is not visible without disassembling the ascender. The cam is a plated steel casting. The cam face is concave and has conical teeth in a (2.3)(4.3)^6 pattern. There is a large finger hole in the cam which allows one to pivot the cam safety, and an extension on the back of the cam finger hole provides a comfortable surface for fingering the cam. The cam extends past the pivot to a second pivot pin located about 18 mm. from the main pivot. A second "L" shaped 4 mm. aluminum frame piece extends downwards from this pivot, forming the hand grip side and bottom of the hand hole. A well rounded 19.8 mm. hole at the bottom of this piece forms the main sling attachment point. This piece has a rubberized hand grip molded onto it.
The bottom of the main shell and the bottom of the "L" shaped piece are connected by a short, curved piece of 4 mm. aluminum. This piece is connected to the other two by one rivet each. The rivets are set loosely so the connections are free to rotate.
The cam and three frame pieces form a quadrilateral where all four corners are free to rotate. As a result, raising the hand grip raises the end of the cam opposite the rope, thus lowering the end near the rope and pivoting the cam open. During this operation, the hand grip ("L" shaped piece) moves upwards with respect to the main frame piece. The cam spring opposes this motion, so it acts to raise the main shell. At first friction against the rope prevents this and the cam starts to open, but eventually the cam no longer has enough friction on the rope, and the ascender moves upwards. When weight is applied, the cam spring acts to close the cam, and this action coupled with the climber's weight moves the "L" shaped piece downwards. The climbers weight is transferred to the cam by the "L" shaped piece. The cam exerts enough normal force on the rope to prevent sliding, and the climbers weight is held.
The cam safety is a bent tab mounted on the cam with a 3 mm. solid rivet. A small coil spring pushes the safety downwards. A pin on the rear of the safety engages a zig-zag slot cut in the main frame piece. Under normal operation the cam safety pin follows the lower slot of the zig-zag, thus limiting the amount the cam can open. By pushing up on the thumb knob, the pin enters the upper slot of the zig-zag and the cam can open. A notch in the rear of the upper zig-zag provides a hold-open lock.
The front of the main shell piece is stamped with an up-pointing arrow, "ROPE 8≤Ø≤13," the UIAA and Black Diamond logos, and "Black Diamond" in raised letters. The rear is stamped "CE 0639" and "7038. The hand grip has the Black Diamond logo molded in each side.
Black diamond clearly copied some of the old Kong-Bonaiti ideas when they developed the nForce, and I'm not really sure why they chose to do so. Like the Kong-Bonaiti, the nForce operates on an entirely different set of principles than handled eccentric cam ascenders. The moving frame takes some time to get used to if you are accustomed to other handled ascenders. One disadvantage is that this ascender is more difficult to push up the rope, particularly if the rope is hanging against a wall with one's weight on it. This situation can often be avoided by proper pit rigging. This ascender gives a little more lost motion than normal handled eccentric cam ascenders. I see two main reasons for this. The first is the pivoting action of the handle. The other is that the sling attachment point is located farther from the main rope, so the ascender cants away from the vertical with each step.
On the other hand, the lever cam design is less sensitive to rope conditions than eccentric cam designs. In particular, the nForce can be expected to hold under some mud and ice conditions where the handled eccentric cam ascenders ascenders slip.
The workmanship on this ascender appears to be quite good, and the construction is solid. All frame edges are rounded. The sheet metal shell has the same potential bending problem as all other sheet metal shells discussed in this site, but at least the nForce used heavy 4 mm. for the frame and reinforced it well. The riveted joints are probably the weak point. The sling attachment holes could have the same safety problem described for the Clog Expedition ascenders.