woldson Posted November 2, 2008 Share Posted November 2, 2008 Subject: Math question Math Question A Backhoe weighing 8 tons is on top of a flatbed trailer and heading east on Interstate 70 near Hays, Kansas. The extended shovel arm is made of hardened refined steel and the approaching overpass is made of commercial-grade concrete, reinforced with 1 1/2 inch steel rebar spaced at 6 inch intervals in a criss-cross pattern layered at 1 foot vertical spacing. Solve: When the shovel arm hits the overpass, how fast do you have to be going to slice the bridge in half?? (Assume no effect for headwind and no braking by the driver...) Extra Credit: Solve for the time and distance required for the entire rig to come to a complete stop after hitting the overpass at the speed calculated above. Yes, you can neglect friction. I couldn't solve it either......but who cares; the pictures are great! Quote Link to comment Share on other sites More sharing options...
woldson Posted November 2, 2008 Author Share Posted November 2, 2008 Quote Link to comment Share on other sites More sharing options...
woldson Posted November 2, 2008 Author Share Posted November 2, 2008 Ya know looking at this more carefully, is it real? Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted November 2, 2008 Share Posted November 2, 2008 Looks like it's holding the bridge up! LOL! BTW that is a track hoe not a back hoe. Weight of that one is about 60,000+ lbs not 8 tons. That was a 50 ton lowboy hauling it before the wreck. Detachable neck model. Total weight would have been over 90,000lb. Quote Link to comment Share on other sites More sharing options...
woldson Posted November 2, 2008 Author Share Posted November 2, 2008 Good point! This came from my mom, figured I'd pass it along. Quote Link to comment Share on other sites More sharing options...
datsun79z Posted November 2, 2008 Share Posted November 2, 2008 I wonder if the driver was repremanded? Quote Link to comment Share on other sites More sharing options...
Lazeum Posted November 2, 2008 Share Posted November 2, 2008 I did not think a track hoe was that strong. I would expect the bridge to be in better shape... Good pics, btw Quote Link to comment Share on other sites More sharing options...
Chaparral2f Posted November 2, 2008 Share Posted November 2, 2008 Gawd, I hate when that happens! Quote Link to comment Share on other sites More sharing options...
xxjoeyxxeb Posted November 2, 2008 Share Posted November 2, 2008 It looks wierd, neither side of the bridge has a full slice (or entrance) that the arm would have cut into the bridge. Unless, the arm was low, then they raised it up post-F-up? Quote Link to comment Share on other sites More sharing options...
Globerunner513 Posted November 2, 2008 Share Posted November 2, 2008 Bill Engvall Then there was the guy with the 18-wheeler... Wouldn't ya know he misjudged the height of the overpass... The truck got stuck and he couldn't get it out no matter how he tried. He radioed in for help and eventually a local cop shows up to take the report. He went through his basic questioning.. ok.. no problem. The guy thought, "He can't say it, he's a paid official..." He thought sure he was clear of needing a sign... until the cop asked "So.. is your truck stuck?" The guy couldn't help himself! He looked at the cop, looked back at the rig and then back at the cop and said "No I was delivering this overpass and my truck stalled... here's your sign." Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted November 3, 2008 Share Posted November 3, 2008 It looks wierd, neither side of the bridge has a full slice (or entrance) that the arm would have cut into the bridge. Unless, the arm was low, then they raised it up post-F-up? no, it's a case of leaverage, looking at it, the arm was low, but hit the bridge below the side fence, you stick something into a 90* corner while running past and the leaverage means it will stick in the corner. In this case the body of the excavator has a hell of a lot of inertia and caused the arm to punch in, and since the arm stowed would form a trangle side and friction/drag pulled it up, that punched it up through the road base, you can see where the bucket slammed into the underside and rebounded in the next picture. An interesting illustration of leverage and inertia Ps: as to the strength of the material making up a excavator arm, they're typically a buttressed "I" section with side plates covering the open sides of the "I" beam. The 17 ton Samsung the local contractors had was made from Bisalloy plating between 26mm and 15mm. this is the same plating as is used on gun ranges as steel targets in 10 and 12mm thicknesses. The photo resizing screwed up and pixellated the engine bay door writing in the pic, but it look like it might be saying 220, which would make that a 22 tonner. so if it has thick plating making up the arm, of thicknesses 2 to 3 times the thickness of something which will survive years of being smashed with bullets, then I'm not surprised it bashed the bridge up Quote Link to comment Share on other sites More sharing options...
JSM Posted November 3, 2008 Share Posted November 3, 2008 I wonder if the driver was repremanded? I was wondering if he was fired! Ah... boss... I've got a little bit of a problem and may be late making it back to the shop.....Cough... Cough... Could you imagine the insurance claim on that! Wow! Quote Link to comment Share on other sites More sharing options...
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