Howdy All,

Thanks a ton for everyone coming out for the snow anchor testing session this past Saturday.  Members that attended were Todd, Nate, Melissa, Ellen, Tim, Jonathan, Mike, Aaron, Jerry and visitor Kerri.


Special thanks to Todd for helping with so much of the setup work for the weekend!

We got to Hoodoo and everyone was pretty much ready to go by 9AM.  Bob was kind enough to offer a SPSP snow machine to haul Randy and all the gear out to the training site.  That really saved us a lot of time and let us focus on the training objectives.

Thanks Bob!

We got to the training area which was the large open slope on the east side of Hayrick Butte where the snow machines go for high marking.  Really helps the whole atmosphere thing, tell you what.

Since we were focusing on the strengths of three different type of snow anchors, we spent a fair amount of time picking a uniform snow slope and creating as uniform as possible of a work hardened area that was 110 feet long by 6 feet wide.  That took some effort, but everyone was totally gung ho about it.

We set up a 5:1 MA system with the dynomometer built into the system so that we could test the force that each anchor could hold.  I set an upper limit of 1,500 pounds since the Coyote picket eyes start to fail at around 2,000 pounds.  We also set up two safety ropes.  One ran to the dynomometer and one to the picket being tested.  These would catch everything if an anchor really blew out and help keep anyone from getting speared by a picket.

We tested three different snow anchor styles five times each for a total of 15 anchors.  We set up a mid-clip vertical anchor (Sierra), then a top-clip vertical picket, then a mid-clip horizontal picket (deadman).  All of the pickets had six feet of space between them.  This pattern was repeated across the work hardened area in an attempt to account for any differences in the snow.  Each picket was connected by a carabiner to a four foot dyneema sling.  All of the vertical pickets were buried to the top of the picket and the horizontal pickets were buried to one foot in depth.  Ellen set up all of the deadman pickets, Aaron all of the Sierra pickets, and Melissa all the top-clip vertical pickets.  They were really careful about duplicating picket depth, orientation to the load, setting slings in to the correct depth, and all of that.  I think it would have been pretty much impossible to set in more correctly placed pickets.

The snow was very similar to spring corn snow.  You could make a snow ball, but it did not hold together really well.  On top of that, the snow really would not work harden very well.  It would some, but even an hour after stomping the heck out of the snow, it was still not hardened that much.  But, that was what we had and we went with it.

I had Todd and Kerri watching the pickets and making notes about how the picket failed (if it did) and Jonathan created short videos of all of the tests.  Tim worked with the dyno and recorded the peak forces.  Nate, Mike, Melissa, Aaron, and Ellen ran the haul team.

We started testing at 12:15 and finished the testing at 13:28.

Here are the test results.  MCV is mid-clip vertical, TCV is top-clip vertical, and MCH is mid-clip horizontal.

Test Number Anchor Style Test Time Peak Force (lbs) Pass / Fail Failure Type Picket Behavior Horizontal Travel (in)
1 MCV 12:15 490 Fail Compression Rock forward, then pop up N/A
2 TCV 12:22 510 Fail Compression Rock forward, then pop up N/A
3 MCH 12:25 1,560 Fail Compression & Shear Sudden, explosive failure N/A
4 MCV 12:31 940 Fail Compression Rock forward, then pop up N/A
5 TCV 12:34 640 Fail Compression Rock forward, then pop up N/A
6 MCH 12:37 1,550 Pass N/A Compressed towards load N/A
7 MCV 12:57 1,000 Fail Compression Rock forward, then pop up N/A
8 TCV 13:00 600 Fail Compression Rock forward, then pop up N/A
9 MCH 13:01 1,570 Pass N/A Compressed towards load 13
10 MCV 13:05 480 Fail Compression Rock forward, then pop up N/A
11 TCV 13:07 430 Fail Compression Rock forward, then pop up N/A
12 MCH 13:09 1,450 Fail Compression Rock forward, then pop up N/A
13 MCV 13:23 460 Fail Compression Rock forward, then pop up N/A
14 TCV 13:26 450 Fail Compression Rock forward, then pop up N/A
15 MCH 13:28 1,700 Pass N/A Compressed towards load 38










MCV Average 647





TCV Average 526





MCH Average 1,566




Given the snow conditions, the only picket style that could be used to create a rescue load anchor system (without using a huge number of pickets) was the horizontal picket.  Most everyone was surprised at the low force required to pull the Sierra style pickets.  The trench that was dug for the leash just could not be refilled and work hardened enough to equal the hardness in the surrounding snow pack.  This left a slot that the top half of the picket could rotate through to the point that the entire picket would pop out.

After a short break, we set up a compound 10:1 MA system and a anchor system using three horizontal pickets buried 14 inches down and equalized with lots of slings and webbing so that the sling angles were all below around 30 degrees.  The slings were not tied into a fixed power point, but could shift to accommodate a shifting load.  This was made in the same work hardened area we used for earlier testing.  The dyno recorded a peak force of 2,000 pounds, which is the force that was going into a 2:1 MA system.  So, theoretically, the force on the anchor system was 4,000 pounds.  But, assuming a pulley efficiency of 90 percent, this anchor system held a peak force of about 3,600 pounds.

After digging up the pickets, we saw that one of the pickets had hit an area that allowed the picket to rotate at least 60 degree from perpendicular to the load position that is was placed in.  This was seen at the power point since it moved forward 22 inches and the equalizing webbing allowed for this movement.  In other words, it was like a really slow and gentle anchor point failure with about 22 inches of extension.  But, is still held around 3,600 pounds of slow pull force.

After the testing was completed, we dug some quick pits in the front of the work hardened area to test for snow hardness.  The general results were 3 fingers down to 8-10 inches and fist down to 2 feet.  Not very hard snow after lots of work hardening and sitting for almost 4 hours.

Bob came back out for us and hauled everything back to the truck and we were back to the parking lot around 1600.

The common comments from the debrief were that people liked the testing and would like to do more in the future.  Most people were interested in starting to do some type of dynamic testing of anchor systems as well as slow pull testing of anchor systems.

Aaron then lead us to a great pizza place in Sweet Home for a fantabulous dinner.

Thanks everyone for making this a great training.

Jerry

PS.  As a side note, we got new batteries for the portable radios and used them as much as possible during the day.  Todd reported that the batteries still showed a full charge at the end of the day.  Quite a change from the 2 -3 hours we had been getting on the old batteries.