pop2tu
Active Member
And the Sierra Nevada Mountain range is considered to have some of the heaviest snow in the US.
Rubicon Winter Rescue
- Thread starter Strike Force Zebra
- Start date
And the Sierra Nevada Mountain range is considered to have some of the heaviest snow in the US.
pop2tu
Active Member
And this was a very high moisture content year too
NevadaZielmeister
Caught the Bug
You got me thinking, so I did some quick searching and rough estimates. A cubic foot of snow can weigh anywhere from 7lbs for light snow, heavy wet snow can weigh 15lbs, and if it has drifted and got wet it can weigh 20lbs. I guessed the roof of a XJ measures approximately 5' X 7' and the snow was 6' deep (really looks deeper) that equals 210 cubic feet. so a light (Dry) snow would weigh 1470lbs, a heavy (wet) snow would weigh 3150lbs, and a if it had got wet and weighed 20lbs that would be 4200lbs on that roof. No wonder A pillars are bowed out!
Yehhhh..... not really.
You forget that snow is pretty solid and lends itself to being supported by the other surrounding snow. Thus people can build snow caves. What you are doing wrong here is assuming that frozen water acts the same as water. The pressures are not linear at all and really, the weight of the snow will likely be more into 100-200 pounds range, if that. If you were dealing with actual water at depth, then you would be right, as the pressure is the weight of the column of water directly above the subject. A column of water at this depth would be substantial, but no where even near 4,200 pounds.
Nice try though.
NecessaryEvil
Caught the Bug
Well looking at the picture alone, you can tell the snow is pretty hard. If they used those winches, it does not appear the cables have dug in the snow too much. Plus the rigs on top don't seem to be either. I would like to see pictures of the vehicles after being pulled out of the snow pack.
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NecessaryEvil
Caught the Bug
That makes sense too. Definitely still a crushing force in some capacity, given the pictures I have seen.
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pop2tu
Active Member
Good point, I had not considered that aspect.
jesse3638
Hooked
I would have liked to see the face of the owner when he returned to find it months later. "Damn! I swear I left it right here!" You did under several feet of snow. I bet it looks totally different now than when they got stuck. I definitely want the rest of the story after they recover it. Wasn't there 1 or 2 more there with that one?
Sharkey
Word Ninja
Yehhh....not really.
As a general proposition (depending on the construction requirements in your area), the roof of a house should be able to support approximately 20lbs - 40lbs per square foot of snow before stress occurs. Two feet of packed snow on a roof can exceed the 20lb measurement and potentially collapse a roof.
In the case of this vehicle, I agree there is some support provided by the surrounding snow, but the weight of the snow on this vehicle far exceeded the 100-200 lbs range...and it absolutely exceeded 20lbs per square foot of roof space. The vehicle's roof and A-pillars collapsed...that doesn't just happen with 200 lbs. of dead weight sitting on top, even for five months.
Story has it that they had installed a roll bar before this happened and the roof was crushed down to the roll bar, the windshield was busted and they unintentionally broke the passenger window trying to get in. There was no snow inside of the Jeep.
They are going back this saturday and looking for help.
They are going back this saturday and looking for help.
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NevadaZielmeister
Caught the Bug
Yehhh....not really.
As a general proposition (depending on the construction requirements in your area), the roof of a house should be able to support approximately 20lbs - 40lbs per square foot of snow before stress occurs. Two feet of packed snow on a roof can exceed the 20lb measurement and potentially collapse a roof.
In the case of this vehicle, I agree there is some support provided by the surrounding snow, but the weight of the snow on this vehicle far exceeded the 100-200 lbs range...and it absolutely exceeded 20lbs per square foot of roof space. The vehicle's roof and A-pillars collapsed...that doesn't just happen with 200 lbs. of dead weight sitting on top, even for five months.
Yehhh.. still not really really.
You are correct, the weight of snow BY ITSELF is substantial, but this snow was in a hole. The caving in of a vehicle roof does not take much to begin with.
After reviewing this report from FEMA (https://www.fema.gov/media-library-data/7d8c55d1c4f815edf3d7e7d1c120383f/FEMA957_Snowload_508.pdf) we find the following statements: "One foot of snow on the ground does not necessarily equal 1 foot of snow on a roof." and "As noted earlier, roof snow loads vary from ground snow based on multiple factors. Therefore, attempting to measure ground snow weight and assuming that it is the same as the roof snow load is incorrect."
I think the load could be anything without actually measuring it. I wonder if there was some other force involved. Maybe when the guys were digging the snow out, they probably caved in the roof and the pillars just by standing on it?
NevadaZielmeister
Caught the Bug
I nominate Sharkey to head that up. Sharkey? You game this weekend my friend?
NevadaZielmeister
Caught the Bug
I would wager that we are talking more like middle of August, what do you think? Has the trail ever been closed all year? If this trail is not available, what other trail would you recommend that is similar?
The reason why I ask is because of my VERY limited Rubicon experience (one time) and my excitement to get out to that trail again.
notnalc68
That dude from Mississippi
Yehhh....not really.
As a general proposition (depending on the construction requirements in your area), the roof of a house should be able to support approximately 20lbs - 40lbs per square foot of snow before stress occurs. Two feet of packed snow on a roof can exceed the 20lb measurement and potentially collapse a roof.
In the case of this vehicle, I agree there is some support provided by the surrounding snow, but the weight of the snow on this vehicle far exceeded the 100-200 lbs range...and it absolutely exceeded 20lbs per square foot of roof space. The vehicle's roof and A-pillars collapsed...that doesn't just happen with 200 lbs. of dead weight sitting on top, even for five months.
Yeah. I'm not a math person, but it took more than 200 lbs to do that. Where are all the engineers, that chime in about winch cutoffs? Maybe they can figure it.
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jesse3638
Hooked
I'm gonna add this with regards to the vehicle standards for roof crush. If this holds true then the original estimated weight seems more accurate.
"The Federal Motor Carrier Safety Administration (FMCSA) determines roof crashworthiness standards for passenger vehicles. Standard 216 requires that a passenger vehicle pass a static test, during which a heavy flat device is pressed down on one side of the vehicle's roof at 13 millimeters per second until it reaches a force equal to 1.5 times the unloaded vehicle's weight. To pass the test, the vehicle's roof must be able to withstand the force of the weight without intruding more than 5 inches into the passenger compartment. For example, the roof of a passenger vehicle that weighs 3,000 pounds must be able to withstand 4,500 pounds of weight without caving in more than 5 inches."
I read it on the internet so it must be true. Neil and Sharkey maybe you can explain this a little better as it deals with both of your worlds...haha
Plus as mentioned if there was in fact a cage installed the roof could have possibly collapsed more.
"The Federal Motor Carrier Safety Administration (FMCSA) determines roof crashworthiness standards for passenger vehicles. Standard 216 requires that a passenger vehicle pass a static test, during which a heavy flat device is pressed down on one side of the vehicle's roof at 13 millimeters per second until it reaches a force equal to 1.5 times the unloaded vehicle's weight. To pass the test, the vehicle's roof must be able to withstand the force of the weight without intruding more than 5 inches into the passenger compartment. For example, the roof of a passenger vehicle that weighs 3,000 pounds must be able to withstand 4,500 pounds of weight without caving in more than 5 inches."
I read it on the internet so it must be true. Neil and Sharkey maybe you can explain this a little better as it deals with both of your worlds...haha
Plus as mentioned if there was in fact a cage installed the roof could have possibly collapsed more.
jeepbn
New member
Ok so I'm at the eye doctor in the waiting room. I just read this and laughed so hard out loud that people are now uncomfortable... Thanks. Lol
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Sharkey
Word Ninja
Yehhh.. still not really really.
You are correct, the weight of snow BY ITSELF is substantial, but this snow was in a hole. The caving in of a vehicle roof does not take much to begin with.
After reviewing this report from FEMA (https://www.fema.gov/media-library-data/7d8c55d1c4f815edf3d7e7d1c120383f/FEMA957_Snowload_508.pdf) we find the following statements: "One foot of snow on the ground does not necessarily equal 1 foot of snow on a roof." and "As noted earlier, roof snow loads vary from ground snow based on multiple factors. Therefore, attempting to measure ground snow weight and assuming that it is the same as the roof snow load is incorrect."
I think the load could be anything without actually measuring it. I wonder if there was some other force involved. Maybe when the guys were digging the snow out, they probably caved in the roof and the pillars just by standing on it?
Um, the Jeep didn't start in a hole. The Jeep was above ground and on top of some snow when it got stuck. So, when new snow fell, it fell directly onto the Jeep while also falling on the ground around the Jeep.
Consider the following. If five feet of snow fell, there would have been five feet of snow on the roof, five feet on the hood (which would not be level with the roof), and five feet on the ground (which would not be level yet with the roof either.) There was a lot of weight on top of that Jeep by the time the pre-stuck level of snow at the tires built up to be at roof level. Then it just got worse from there.
Snow didn't fall into a hole and onto the Jeep. Snow built up around and on top of this Jeep...probably in the nature of 40+ FEET of snow!!! I've seen metal carports in Reno collapse with 2-3' of wet snow. This poor Jeep didn't have a chance.
Sharkey
Word Ninja
If I knew these guys and had the right set up (a vehicle with tracks), I would absolutely be part of this recovery. It looks like an incredible learning experience, regardless of how dumb it was to end up in the situation to begin with.
2nd.gunman
Caught the Bug
Lol. The smart ones stick to what they know and the dumb ones have already run off to hide at JKO
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Brute
Hooked
Water weighs approximately 4.5 psi per foot of descent in the water column...this is why you cannot breathe through a straw laying on the bottom of your pool
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