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Thread: math help ...

  1. #31
    the really sad thing is that you have to worry about the irresponsible people harming your house / family in the first place
    and even worse that protecting it/ them even has the possibility of landing you in legal trouble

    just illustrates very graphically how screwed up things have gotten

  2. #32
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    You could try several concrete barriers like you see on highway projects. They pin together, and are designed to deflect vehicles as long as they hit the barriers at a shallow angle. While not perfect, it might be helpful, and you might contact a road contractor about buying some of their older barriers. Maybe the damaged condition of them would get people to slow down.
    Where's the beef.

  3. #33
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    5 accidents on one street over a year period is hardly an epidemic. Amazingly enough there are around 290 thousand accidents per year in Michigan alone. The vast majority are single motor vehicle accidents.

    I would certainly run your scenario of a vehicle catch by an attorney or homeowners agent first, especially since the intent of said object is now public.

    To answer your question, there isn't an easy answer. As part of my job duties I investigate serious and fatal accidents. There are way to many factors to count to figure what will work. Because the vehicle is moving it will always want to "glance" off and continue unless it hits at a 90 degree impact. Because an object at rest wants to stay that way it won't take as much weight as you may think to completely stop a vehicle. Any object big enough to reliably keep a vehicle from deflecting off will be plenty heavy.

    You don't mention the speeds involved and that is the primary factor to consider. When speed increases the stopping distance increases at a much greater rate. So stopping an object, in this case a vehicle is largely weighted towards speed.

    Joe
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  4. #34
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    Chritz,
    Charlie mentioned in his first post the speeds of the vehicles:

    Quote Originally Posted by Charlie Stone
    How heavy of a rock would we need to stop a 5000 lb vehicle (average idiot not paying attention) traveling at 35 mph?
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  5. #35
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    Quote Originally Posted by Joe Chritz View Post
    5 accidents on one street over a year period is hardly an epidemic.
    Joe, on one block, an approximately 200 foot distance. 3 houses out of 9 were hit by cars in 1 year. That is pretty bad. 5 accidents isn't the grand total for the year, that is just the ones where stationary objects were hit on a single block.

    This is a straightaway. There is no curve, there is no dead end, nothing special about the area. No visibility issues, the road going north/south, so sunrise/sunset isn't the issue. There is a college on one side and bars on the other. The only odd factor is the block in question is at the bottom of a 1000' long hill.
    Last edited by Charlie Stone; 11-09-2010 at 11:05 AM.
    Please tell me that was scrap ...

  6. #36
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    Also consider creating an earth berm which incorporates a few large boulders, a couple of nice trees and an evergreen ground cover and some seasonal color. Couple of feet high, 2:1 slope on the edge and a nice natural undulating shape might fit into your yard and look more natural than just slapping down boulders. Can't tell without seeing your yard. Heck...go crazy and incorporate a water feature..your local landscapers will thank you.

  7. #37
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    Make it a shrubbery... with a path down the middle, giving it a two-level effect
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  8. #38
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    Quote Originally Posted by Dan Hintz View Post
    Make it a shrubbery... with a path down the middle, giving it a two-level effect
    hmm .. now I need to find a shrubber or they will say Ni again.
    Please tell me that was scrap ...

  9. #39
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    Charlie, the unfortunate truth about this forum is that (while I absolutely LOVE it, and it is the best thing since sliced bread) you are generally barking up the wrong tree when it comes to sympathy for situations like yours. I do not just sympathize with you, I empathize with you as well. But there are many here that don't. Unfortunately, you asked a direct question about math (or maybe it was more about physics, but what is physics but higher math?...) and got answers that were not digital, analog, computed or calculated. You got opinions as to whether or not you SHOULD put up a rock, what other bariers you could put up, what other methods you could use to stop vehicles, and the ever present total dismissal of your situation being a problem at all.

    Personally, I love the rock idea. I love the idea of a bunch of them. Use them as hardscaping. Plant around them...or at least on the back side of them so when someone plows into them, it doesn't mess up your plants.

    But again, as I said in my previous post in response to your question, I would imagine that anything in the two ton range AS LONG AS IT IS TALL ENOUGH TO NOT LAUCH THE CAR OVER THE ROCK, would/ought to do a decent job. Of course, I don't know how far the rock(s) would be placed from the house and just how quickly they need to be stopped. But 2 tons, with the friction of the ground, and enough space between the rock and your house ought to keep them out of your living room. A line of large rocks would also make a nice sort of "fence"....
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  10. #40
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    Classic, Dan! And kudos to you Charlie for catching it...
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  11. #41
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    Mike, you are 100% correct. I knew of the "moral" issues around something like this, however, It was the math (in my mind, physics is math) I was after. If I were a less complicated person I would have simply thought, well, a parked car seems to do a pretty good job stopping most other vehicles when they are hit or when a car is broadsided. So, roughly the weight of a large car. Silly me for over thinking it.
    Please tell me that was scrap ...

  12. #42
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    I posted something about replacing the boulder with a metal spike, but it appears to have been removed... shades of a conversation started on one of my engineering forums discussing how to deal with bad drivers.
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  13. #43
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    a 5000lb vehicle traveling at 51.3333 fps (35mph) will have a impact of 204843.836 ft pounds of energy..
    You need a bigger Rock
    Last edited by Bill Cunningham; 11-09-2010 at 10:51 PM.
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  14. #44
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    And just remember, you don't need to stop the vehicle dead in its tracks, you simply have to stop it within 10-15'... objects like a large rock take a lot of energy to keep moving...
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  15. #45
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    we picked out a 1.25 ton boulder. about 2 feet tall and 3 wide and set it on top of a slight incline. It makes a wonder decoration and my wife will be looking for a shrubbery to plant near it.
    Please tell me that was scrap ...

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