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Strmeň Žiara

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

Technical Details

I acquired my Strmeň Žiara from Ondřej Belica in 2020.

Cam faceThe Strmeň Žiara is 192 mm. tall, 74 mm. wide, 30 mm. thick, and weighs 211 g. The shell is made from 3.75 mm. aluminum alloy sheet metal. A 14 mm. wide rope channel is formed in the upper portion of one side. The cam is bolted to the opposite side with a 10 mm shoulder bolt that acts as the cam pivot. The pivot is centered 58 mm. from the inside of the rope channel. A safety is bolted to the frame below the cam pivot with a 6 mm. shoulder bolt. this serves as the safety pivot. A 9.4 mm. tall, 6 mm. diameter pin is pressed into the frame between the cam and safety pivots. The cam spring is made from 1.6 mm. wire. It wraps around the cam pivot 1-1/3 times and terminates on the pin. The safety pivot is made from 1.0 mm wire, and wraps around the safety pivot 2-3/4 times and then terminates on the pin. Two soft handgrips are glued to the lower outside portion of the frame. A 13 mm. hole on the lower inside of the shell serves as the main sling attachment point. A second 13 mm. hole provides an attachment point just above the cam.

The cam is milled from plate aluminum alloy. The cam radius, measured from the pivot, increases from 44 to 59 mm. over an angle of 42°, giving a 22° cam angle. The tooth pattern is (2.1)^4(2). Each tooth is a round-tip hardened steel pin pressed into a hole drilled in the cam face. The inner cam face radius is constant from top to bottom.

There are no markings on this ascender.


Ondřej sent me the following information:

The last ascender I've seen few years ago. I had no clue what it was, but I wanted to get it and find some more information about it. And I've succeeded.

It is Strmeň Žiara (or just Strmeň). It used to be produced by Žiara (Výrobné družstvo invalidov Žiara - Worker/manufacturing of the disabled Žiara) in Slovak town in former Czechoslovakia.

It was invented by Petr Hipman (Czech guy who loved caves so much that he moved to Slovakia to be closer to the amazing caves there) in 1973. Produced by Žiara, in the end of 70’s and the beginning of 80’s, it is the most common ascender in Slovakia. Unfortunately it was made by low quality 4 mm sheet metal so it used to open loaded by 2.5 kN. It was replaced by bogibbs (produced by Žiara).

Petr’s described the Strmeň Žiara in Spravodaj Slovenská speleologická spoločnosť (Slovak Speleological Society News) v. 1 in 1975. Judging from the illustrations in the article, I assume that the Strmeň Žiara was only made in a left-handed version.

The teeth are unique. The construction is similar to that of the Spent Ruční, but the teeth are rounded rather than sharpened. As a result, the ascender does not grip well.

The attachment points are simple holes in the shell and are not rounded. The user should blunt the corners with a file or similar tool. I consider their small radius too sharp for directly attaching sling ropes. They are probably acceptably rounded for webbing, but considering the proximity of the attachment points to the main rope, I would recommend using a small maillon for most attachments in order to reduce the risk of sling abrasion. The lower attachment hole could theoretically have the same safety problems as the one on Clog Version A. The upper rope attachment hole is located very close to the main rope. A carabiner through the upper attachment hole may drag on the main line. Both attachment holes are too small for some standard carabiners.

This ascender has the same pit lip disadvantage as the Clog.

The cam and safety springs on my Strmeň Žiara are far too strong. I find it impossible to open the ascender with one hand, and I struggle to do so with two - and I have very strong hands. Placing the ascender on rope requires a major struggle. The maximum opening between the cam and the rope channel is only 8.7 mm. Normal caving ropes are 9 mm to 11 mm., and so they do not fit easily though the opening. The overly-strong springs and narrow opening render this ascender effectively unusable under field conditions, and so I give it a Lemon Award .

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