Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Lead Block inside 52' US-type Trailer Experiement

  1. Aug 12, 2011 #1
    Can someone calculate the weight of the object and what would most likely happen in the following experiment that I have always been curious about:

    Imagine you have a brand new 52-foot standard refrigerated cargo trailer mounted on a brand new standard heavy duty sleep cab tractor (i.e., an "18-wheeler" or "tractor trailer). Assume a lead block that is 1" smaller in every dimension than the opening of the rear of the truck and also 1" shorter than the front to back length of the interior of the trailer. I use 1" inch less so no one says it would bind against the sides and it could not be inserted, but feel free to adjust that dimension slightly if it helps. Assume that this enormous lead block before being inserted into the trailer is laying on type of a hypothetical forklift's fork that is hypothetically long enough to be able to hold this long block of lead. And assume the forklift has enough counterbalance not to tip over from the weight of the block (I realize this probably doesn't exist). Also assume the forklift has a "pusher" behind its fork that can push this lead block off its fork. Also assume that the forks are not not thicker than one inch tall (so they will not bind against the truck opening when carrying this one inch lead block.

    Assume the truck is located on aircraft runway quality concrete that will support millions of pounds. Now here's the question:

    What would happen to the truck the instant this lead block is inserted into the truck and it begins to handle its load on its own? Would the tires instantly all burst? Would it crack the concrete? Would it not just instantly burst the tires but would crush the entire undercarriage of the truck's drive wheels and trailer wheels/axles and everything else in the undercarriage and just be flush with the ground? I'm really curious!
     
  2. jcsd
  3. Aug 12, 2011 #2

    Mech_Engineer

    User Avatar
    Science Advisor
    Gold Member

    A lead block the size you're describing (appromiately 100"x110"x52') would weigh around 2.81 million pounds. Considering a trailer of the 100"x110"x52' variety will have a load capacity of around 50,000lbs, that means your block weighs 52 times more than the trailer's carrying capacity.

    It would burst the tires and likely crush most of the undercarriage into the pavement.
     
  4. Aug 12, 2011 #3
    Thanks. It would be amazing to see that happen. Do you know for certain that the tires would burst instantly upon the bottom portion of the rims impacting the pavement (imagine freezeframing the entire downward motion of the trailer at that moment) or are you saying they would burst split seconds later as the entire trailer crushed the undercarriage into the pavement?

    Secondly, would there be any "pancake" left visible of the undercarriage, considering some of it is solid steel (like the axles) or do you think it would be pulverized or simply pushed upward into the soft lead that crushed it making it invisible? Also would the lead flatten out bursting the side of the trailer because of its softness and mass upon impact with the pavement, or would it be contained in the trailer box?
     
  5. Aug 12, 2011 #4

    Mech_Engineer

    User Avatar
    Science Advisor
    Gold Member

    Dude, who cares? The trailer would be history.
     
  6. Aug 12, 2011 #5
    I care. Other people probably are interested too. It's an interesting visual, especially because I think in industry people commonly way overload trailers. Even if this exact extreme example is never attempted, it's a relevant study to see what happens when users overburden mechanical devices.
     
    Last edited: Aug 12, 2011
  7. Aug 12, 2011 #6

    DaveC426913

    User Avatar
    Gold Member

    That would generate an average weight of 420lbs. per square inch - over every square inch of the trailer's floor and undercarriage...
     
  8. Aug 17, 2011 #7
    Interesting scenario.

    Realizing the high cost of osmium and uranium, (let alone other dense materials) 2.8 million pounds of lead (plus the weight of the trailer and tractor) would be the theoretical maximum overload even remotely feasible the Department of Transportation Vehicle Enforcement officers could ever hope to snag.

    As I recall, the fine rates in most states is $.10/lb, so the overweight fine would be approaching $300,000. Considering the damage this load would do to highways, bridges, and viaducts, this is actually a 'deal'.
     
  9. Aug 17, 2011 #8

    DaveC426913

    User Avatar
    Gold Member

    And the gas consumption!
     
  10. Aug 17, 2011 #9
    Mmyess, interesting indeed. Let's assume it didn't crush the trailer immediately as the previous gentleman predicted. And assume further that the driver of said tractor-trailer 18-wheeler combination put in a full 8-hour work day pulling this rig at highway speeds. How much damage in dollars ($) do you think he would cause in one day? $175 billion?
     
  11. Aug 18, 2011 #10

    Mech_Engineer

    User Avatar
    Science Advisor
    Gold Member

    No way. First of all, gigantic loads rarely travel more than about 50 mph, so if you say he was going 50mph the whole time (which of course would be impossible since the tires would explode and the trailer would crush) he would only travel about 400 miles assuming no stops. It might cost a couple million to repair that much road asuming it was badly damaged.
     
  12. Aug 18, 2011 #11

    DaveC426913

    User Avatar
    Gold Member

    I don't understand the purpose of imagining how much damage a trailer could do over its journey if there can be no journey.
    Q: "If it didn't crush the chassis, how much would it crush the road under the chassis?"
    A; "Well none, since you've invoked some sort of magic in your scenario but have not told us what the magic is."

    No, the amount of damage this trailer can do is limited to its initial parking spot - an area of ground approximately 52'x110". Full stop.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Lead Block inside 52' US-type Trailer Experiement
  1. Trailer design (Replies: 6)

Loading...