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JimTitt
Apr 20, 2010, 6:53 AM
Post #26 of 28
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Registered: Aug 7, 2008
Posts: 1002
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It doesnīt matter whether the stud is 304 or 316 as the difference in strength is minimal.
The problem is knowing that the material really is 304 or 316 as some countries seem to be able to produce these grades with the strength of cheese!
The simple test is to get a piece of rod (and nuts) and torque it up with some washers between the two nuts (best done on a steel plate with a hole in it), for an M10 threaded rod the clamping force in kN is approximately half the applied torque in Nm with a dry joint. You should be able to pull something like 45kN on an M10 rod before it breaks. This is all a bit approximate as there are loads of variables but you would be well on the safe side with this.
The reason this system isnīt so popular is related to stopping the hanger spinning, spinners being a pain in the ass to clip and rightly unpopular (as will be the installer whose soul will be cursed forever by struggling leaders). One solution is to weld the nut and hanger onto the threaded bar but this is yet more work. The other solution is to install the threaded bar and then come back and fit the hanger to the correct torque another day, making sure you kept the glue off the threads when installing! This is another load of work for the installer.
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shu2kill
Apr 20, 2010, 1:33 PM
Post #27 of 28
(1305 views)
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Registered: Apr 9, 2008
Posts: 352
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JimTitt wrote: It doesnīt matter whether the stud is 304 or 316 as the difference in strength is minimal. The problem is knowing that the material really is 304 or 316 as some countries seem to be able to produce these grades with the strength of cheese! The simple test is to get a piece of rod (and nuts) and torque it up with some washers between the two nuts (best done on a steel plate with a hole in it), for an M10 threaded rod the clamping force in kN is approximately half the applied torque in Nm with a dry joint. You should be able to pull something like 45kN on an M10 rod before it breaks. This is all a bit approximate as there are loads of variables but you would be well on the safe side with this. The reason this system isnīt so popular is related to stopping the hanger spinning, spinners being a pain in the ass to clip and rightly unpopular (as will be the installer whose soul will be cursed forever by struggling leaders). One solution is to weld the nut and hanger onto the threaded bar but this is yet more work. The other solution is to install the threaded bar and then come back and fit the hanger to the correct torque another day, making sure you kept the glue off the threads when installing! This is another load of work for the installer.
well, since we dont have a dinamometer (yet), we did an empirical test. basically, we drilled a big rock (about 160 lbs) and glued a 100 mm piece of threaded rod to it, to which we later installed a hanger. then, we found a 10 feet boulder (not climbable), and, using a Hilti 3/8 mechanical wedge bolt, installed a hanger at about 6 feet from the ground.
then we took the big rock to the top of the boulder and tied the 2 hangers using big quicklinks and old static rappeling rope.
then, with 3 cameras rolling, we dropped the rock, applying a factor 2 fall to the system. the first time, the top hanger bend downwards a lot, but everything held fine. the second time, the rock chipped a bit, but the hangers held, and both the chemical and the mechanical anchor held just fine. when we edit all the videos and photos i will create a new thread to discuss that and listen to your opinions.
and, if we were to bolt using the threaded rod, we were thinking of doing it as you say. install the threaded rod, and then after it has cured go and install the hangers to the specified torque...
thanx!!
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dingus
Apr 20, 2010, 1:48 PM
Post #28 of 28
(1300 views)
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Registered: Dec 16, 2002
Posts: 17398
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Great thread.
DMT
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