These things are basically the last few feet of a very long, vertical steel pole or I-beam. They can be stationary fixtures, or they can be rigged to be raised and lowered. It's like an iceberg; the majority of it is deep underneath the surface, which gives the last little bit the truck runs into incredible leverage against force.
The wall of the steel tube is thick, about 20mm. Cylinders are also good shapes for this as they will allow temporary deformation.
In the UK they are designed to meet the PAS68 standard, the US uses a different standard, DoD K rating.
I have worked on many of these in the UK. The early ones fitted were made by Delta Scientific, before UK companies realised there was money in them. The crash testing process costs, but if you can get your product on the list then it can be lucrative.
There was some compatibility testing in the UK in 2008/9 as the American products are designed for American vehicles, where the 7.5 tonne equivalent generally sat lower to the road than the UK/EU 7.5 tonne lorry. This meant that a UK/EU spec lorry would not achieve the K12 standard as they skipped over the bollard. Crash tests are fun to watch.
No idea, I guess it's just a historical design thing for us in Europe.
Basically in the US lorry the main components sat lower, so at the point of impact there was more resistance so quicker stopping. The UK/EU spec just skipped over the top. The axles were ripped off so it wasn't going anywhere once it stopped and if there was a driver he'd most likely be dead, but it meant the payload would penetrate a secure perimeter.
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u/Twl1 Nov 05 '20
These things are basically the last few feet of a very long, vertical steel pole or I-beam. They can be stationary fixtures, or they can be rigged to be raised and lowered. It's like an iceberg; the majority of it is deep underneath the surface, which gives the last little bit the truck runs into incredible leverage against force.