{"id":1049,"date":"2017-05-07T00:49:19","date_gmt":"2017-05-07T00:49:19","guid":{"rendered":"http:\/\/www.gregkuchyt.net\/?p=1049"},"modified":"2017-05-07T12:46:41","modified_gmt":"2017-05-07T12:46:41","slug":"analysis-of-raumer-wedge-bolts-in-schist","status":"publish","type":"post","link":"https:\/\/www.gregkuchyt.net\/?p=1049","title":{"rendered":"Analysis of Raumer wedge bolts in schist"},"content":{"rendered":"

Background<\/h3>\n

A report from a Vermont climber\u00a0about issues\u00a0on the route\u00a0War on Drugs<\/em> at the 82 crag prompted inspection of the route’s fixed protection. While dealing with a separate set of problems, the last bolt identified as needing replacement was a 10mm Raumer double wedge bolt. These bolts were thought to be bomber in Northern Vermont schist along with their Fixe counterparts. What was troubling was the way in which the bolt was removed, or more accurately the ease with which it was removed. The manner and ease of removal indicated that the expansion mechanism of the bolt was in no way actually engaging or functioning. It is very troubling for a wedge bolt to be exhibiting behavior like this. Wedge bolts are often thought of as “fool” proof in that once they are installed in the hole, any attempt to remove them or load them will further engage the mechanical expansion effect keeping the bolt in the hole. The exception to this is in soft rock which typically does not allow for proper engagement of the expansion sleeves to achieve proper expansion.<\/p>\n

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Raumer double wedge; vintage early 2000s<\/p><\/div>\n

Failure mode<\/h3>\n

These bolts can be quickly identified with a torque wrench. Attempting to tighten the bolt and hit the target torque value will yield a nut\u00a0that turns endlessly until the nut bottoms out on the threads of the stud. The corollary to this statement is that tightening the nut is backing the bolt out of the hole!<\/strong> Once the threads are bottomed out is it a simple matter to lightly funk the bolt out with a cable and hammer or sometimes even remove it by hand if the beginning of the hole is sloppy. Similarly one can remove the bolt simply by adding a spacer to allow the nut\u00a0to be repositioned to allow for additional displacement of the bolt body. The below video shows the state after the threads have been bottomed out and how easily the bolt is removed.<\/p>\n