Version A	Version B

Overview

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Version A
(#55, 2958)

Front View: Closed	Rear View: Closed
Front View: Open for Rigging	Rear View: Open for Rigging

Technical Details

I acquired this pair of ascenders from Speleoshoppe in 1982. I acquired an additional left ascender from Jasmine Mikulecky in 2020.

Version A is 206 mm. tall, 94 mm. wide, 30 mm. thick, and weighs 237 g.

The Kong-Bonaiti ascender shell consists of a number of parts. The main piece is a black anodized 2.7 mm. aluminum stamping which forms the rope channel, the upper portion of the ascender, and the side of the hand hole opposite the hand grip. Two reinforcing ribs are stamped into the upper part of this piece and reinforce the rope channel. A 13.5 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 convex, not concave, and has 8 cast teeth. The top tooth has a "Z" profile, but the lower teeth become progressively more rounded until the lowest tooth has an almost semicircular profile.

The cam extends past the pivot and downwards at a 40° angle to a second pivot pin located about 29 mm. from the main pivot. A second "L" shaped 2.7 mm. aluminum frame piece extends downwards from this pivot, forming the hand grip side and bottom of the hand hole. A well rounded 13.9 mm. hole at the bottom of this piece forms the main sling attachment point. This piece has a phosphorescent plastic hand grip with four finger grooves molded onto it. It also has a small metal tab riveted in place above the hand grip. This tab engages the cam safety to hold the cam open.

The bottom of the main shell and the bottom of the "L" shaped piece are connected by a short, curved piece of 2.7 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 parallelogram 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 small lever mounted on the bottom of the cam with a 3 mm. solid rivet. A small coil spring connects a second pin in the cam with a hole in the cam safety and pulls the safety upwards. This arrangement is opposite that used in the Petzl where the cam safety spring is in compression. A small cylinder mounted on the safety acts as a thumb knob. Under normal operation the cam safety hits the tab on the "L" shaped piece when the cam opens, thus limiting the amount the cam can open. By pulling down on the thumb knob, the safety can clear the tab. If desired a hook on the top of the safety can be latched around the tab to keep the cam open.

The main shell piece is stamped "<-> KG. 650" with the double arrow aligned vertically. The hand grip has "PHOSPHORESCENT" molded in one side and "BONAITI-KONG-ITALY" molded in the other.

Comments

This is an unusual ascender which 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. The two lower rivets appear rather small to the uninitiated, but they do not carry any weight so there is little cause for concern. The sheet metal shell has the same potential bending problem as all other sheet metal shells discussed in this site. The sling attachment holes could have the same safety problem described for the Clog Expedition ascenders. Like the Petzl Ascension, a carabiner through the top hole prevents putting the ascender on or off rope.

The workmanship on this ascender appears to be quite good. All frame edges are rounded. The two lower rivets have some sharp edges, but they are on the side opposite the rope so there is little chance for rope damage here. I like the phosphorescent handle, even if it really doesn't offer any substantial practical advantage.

This ascender gives a little more lost motion than the other handled ascenders for two reasons. 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 Kong-Bonaiti ascenders can be expected to hold under some mud and ice conditions where the handled eccentric cam ascenders ascenders slip.

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Version B
(#56, 1556, 2107)

Front View: Closed	Front View: Open for Rigging
Front View: Closed, with extension	Front View: Open, with extension
Rear View: Closed	Rear View: Open for Rigging

Technical Details

I acquired this pair of ascenders from Speleoshoppe in 1985. I acquired a third (right-hand) ascender from Robert Blake in 2011. I acquired another pair in 2017 as part of Bob Thrun’s collection.

Version B is 206 mm. tall, 95 mm. wide, 30 mm. thick, and weighs 263 g.

This ascender is very similar to the previous version; only the cam assembly has changed. The cam now uses a combination tooth design. The top 60% of the cam face is a concave surface with some poorly formed conical teeth oriented parallel to the top of the cam. Below these are four convex "Z" shaped teeth. The resulting tooth pattern is (4.3)^2(2.1)(Z)^4. The conical teeth are in contact with the rope, even for excessively small (e.g., 6 mm. ) main lines.

The cam safety has been modified slightly. The tension spring has been replaced by a compression spring located below the safety. The thumb knob is now drilled and tapped, and an auxiliary pin extension is available to screw into this hole. This extends the thumb knob by 12.2 mm.

The ascender shell markings are different. "STATIC ROPE Ø 12 KG ↔ 650" and "UIAA ROPE Ø 9 KG↔ 650" are stamped on the open side of the shell, and "BONAITI-KONG-ITALY’ is stamped on the back. The hand grip markings are unchanged.

Comments

This is an improved ascender compared to Version A. The conical teeth help improve holding ability when the ropes are not too muddy or icy. The compression spring is stronger than the old cam safety spring, and does its job a little better. The optional pin extension is nice. I consider it to be better than the knurled one on the Petzl Ascension. I prefer not to use the extension since it tends to catch on things, but the extension is helpful when wearing winter gloves. If you choose to use it, I recommend using a little epoxy to make the pin a permanent addition to the ascender.

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