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avalanche gun

post #1 of 14
Thread Starter 
How exactly does an avalanche gun work? What propells the shell and what causes the explosion which causes the avalanche?
Thank you
post #2 of 14
There are many different kinds.

Ryan did all kinds of research on this awhile back. I would bet he'll drop in with some answers.
post #3 of 14
Ditto, some are actual ex-US military artillary cannons!
post #4 of 14
Since Ryan hasn't chimed in yet, I'll tell you about the ones I know about. All of these are in use in the Jackson Hole area:

Avalauncher: a compressed-air gun that fires (I think) a one or two-pound charge and has a range of probably up to about a mile. Very good for short-range shots and smaller charges. http://www.avalanche-center.org/Education/glossary/ At the Jackson Hole Mountain Resort, one of these is mounted permanently near the top station of the Thunder Chair. It's used to do control work in the Cirque, Tensleep Bowl, and the Headwall. The avalauncher fired this unexploded projectile that I found on a hike in Tensleep Bowl last summer:



Recoilless Rifle: a semi-portable artillery piece that fires either 75mm or 105mm artillery shells. These are sometimes used for temporary control work and sometimes mounted permanently. At JH, they used to use a 75mm rifle to shoot the shoulder of Cody Bowl for the Powder 8 National Championships. I don't know if they still have that gun or not. Here's a set of photos (from the Bridger-Teton National Forest Avalanche Forecast website) of an avalanche that was triggered in Cody by a shot from that rifle:



105mm Howitzer: This is a not-very-portable-in-the-mountains artillery piece that fires larger shells. These are used when a BIG explosion is called for. There is a permanently-positioned one at the base of the ski area in Teton Village. The patrollers have recorded all of the coordinates of the trigger points of all the main slide paths inside the ski area so that the gun can be fired in periods of low or no visibility. It was this gun that triggered the infamous Headwall Slide in 1986 that ran nearly top to bottom inside the Jackson Hole ski area (and I was an eyewitness : ).

Cable Slides: This is just a rope-and-pulley arrangement that allows a patroller to run a hand charge out over a trigger point and detonate the explosive at a distance that is further away than a patroller could safely throw the charge. There are several of these constructed over chutes and cliff bands around the ski area.

Propane Cannon: This is a very interesting device that allows remote detonation of a large slide area. I don't have a good photo of one but there are four of them located on Glory Bowl above Teton Pass. Basically, it's a large steel pipe that is angled up about 20 feet and then curved back down toward the snow surface. A large chamber inside the pipe is filled with a mixture of propane and air and then ignited remotely. The explosion is directed out the end of the pipe and downward toward the snow surface. During the fall, the Wyoming Highway Department hauls huge propane tanks up the mountain and connects all the plumbing so that these cannons can be completely operated by remote control during snowstorms. No one has to drive on the pass or hike up the mountain during high avalanche hazard.

Charge Slinger: I actually have no idea what this gizmo is actually called, but that's the name I'll use. This is almost a brand-new idea, again being used on Teton Pass. Again, the idea is to be able to deliver explosions remotely. It's kind of hard to describe, but think of a Coke machine that's loaded with explosive charges instead of cans of soda. Also think of a trap machine that flings out clay pidgeons. This device can arm and throw explosive charges out onto the snow service and it can be operated completely by remote control. It seems like kind of a Rube Goldberg contraption to me, but the Highway Department seems to like it.

Those are the main ones that I know about, but I'm sure there are many, many more. The possibilities are practically endless.
post #5 of 14
The Washington State Dept. of Transportation has put a military surplus tank along the old Stevens Pass Highway to shoot the chutes above Highway 2 West of the pass.

The Cascadia Lodge at the ski area has some interesting lighting in the bar that if you look closer is made up of old 105mm and 75mm shell casings. They are perforated to make them recoilless and make dandy chandeliers when hooked togeter artfully. They are from the old lodge that was torn down several years ago.
post #6 of 14
Bob, the propane device you are talking about is a Gazex. Snowbasin has some on no-name.

And I forget this stuff in the off season, but I believe the avalauncher rounds are 2.2kgs. Working on a gun tower is a cold, cold job.
post #7 of 14
After further thought, I think that the hand charges are 2.2 kgs, the avalauncher rounds are lighter. Bunion would know.
post #8 of 14
Quote:
Originally Posted by Bob Peters View Post
105mm Howitzer: This is a not-very-portable-in-the-mountains artillery piece that fires larger shells. These are used when a BIG explosion is called for. There is a permanently-positioned one at the base of the ski area in Teton Village. The patrollers have recorded all of the coordinates of the trigger points of all the main slide paths inside the ski area so that the gun can be fired in periods of low or no visibility. It was this gun that triggered the infamous Headwall Slide in 1986 that ran nearly top to bottom inside the Jackson Hole ski area (and I was an eyewitness : ).
I know these things (Howitzer's and such) save lives (kind of ironic, eh?), but I'm still a little surprised to hear they're firing military artillery in periods of low or no visibility. I'm not familiar with Jackson Hole, but from what I do know, I assume a situation similar to what happened in Utah would not be possible? In other words, there's only OB/backcountry beyond the targeted slide areas?

For those that might have missed it or don't remember, last year the Utah Department of Transportation's Avalanche Control guys overshot their intended target by nearly three miles with a 105mm Howitzer. The shell landed in a homeowner's shed in Pleasant Grove. Although no one was hurt, the incident obviously caused quite a stir. DOT officials said that they were using long-time fixed coordinates, and attributed the mis-fire to "too much gunpowder." :

http://deseretnews.com/dn/view/0,1249,600121107,00.html
post #9 of 14
Most, not all PETN hand charges used for A/C are 1 K (2.2 lb). I also buy some 2 kg units and some larger charges for special work.

The Gelatin Dynamite used at many areas (JHMR) is 2.75 lb.

A lot of CA and WA. areas are using an Emulsion product that come in a variety of weights.

The current incarnation of avalauncher rounds is 2 lbs, the older 1000 LO was 2.2 lbs.

The gunner who was in charge at the Provo Canyon overshoot is no longer employed by UDOT.
post #10 of 14
post #11 of 14

Missed target

Bridger Bowl missed the ridge in the mid to late 60's. The shell went over the ridge and landed in a barn or field towards Belgrade. OOOps
post #12 of 14
Quote:
Originally Posted by iskitoofast4u View Post
last year the Utah Department of Transportation's Avalanche Control guys overshot their intended target by nearly three miles with a 105mm Howitzer.
I know 3 miles sounds like a lot, but given the trajectory of the shell, they only missed by a little bit. The shell then travled down the very steep west face of mount timpanagos. The steepness of the slope allowed the extra travel.

I've heard stories (which I cannot confirm) of the Alta and Snowbird patrol trading shots over wildcat ridge in "the good old days"
post #13 of 14
One season in New Zealand, they were just getting going with fixed firing devices for A/C work, and while test firing the first one, they shot it over the mtn.

On the other side of the mtn was an Army base at Waiorou. We half expected them to start shooting back!
post #14 of 14
I believe this is the fixed gun(Avalauncher) and shell Bob is referring to at JH. I got a plum photo assignment spending the morning photographing the JH Ski Patrol doing their thing. They even let me photgraph them putting together the hand charges in the "boom-boom room" but since they were abit nervous about the public seeing this I decided to not include it. BTW it was -40F that morning but with the sun it felt alot warmer....:lol:



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