High jump equipment: bending of bar
This discussion has an associated proposal. View Proposal Details here.Comments about this discussion:
Started
experience at unicon17:
bars must be extended to 2m, but the bar material was not very stable. Consequence was huge bending of the bar, the defined height only exist in middle of the bar,
Maximum bending must be defined: proposal Maximum 5mm
Comment
5mm is really small and not always realistic. Perhaps you could give some examples for how much different materials bend under gravity.
Comment
When the bar bends there will be a difference of 1 to at most 2cm. While it would be awesome to always have a very straight bar, the measurement is always taken from the lowest point, and as Scott mentioned, we have to remain realistic.
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I think the purpose of Reiner's proposal was to keep a relatively flat bar. If it has a lot of curve, it makes a bigger difference between the official height of the jump and the actual height that must be reached to clear a saggy bar.
It will be good to have a number, so builders of jumping apparatus have a standard to work toward. I suspect some of the nerds in here may want to propose something that's in proportion to the length of the span; but I'd like to just say that's overkill. Just give people a number. Figure out a jumping stick that won't bend more than x millimeters when supported at points 2.2 meters apart. Something like that. I think 2 cm sounds like a safe, workable number but I'm guessing. Maybe we have someone here with actual track & field experience?
Comment
Situation at unicon17:
the bar was a easy PVC pipe used in eletric Installation, correct the height was measured in the lowest point in the middle, near to the apparatus the height would be 2 -3 cm higher (estimation).
Current we have no Limit for bending of the bar, my proposal to define a Maximum bending.
If the organizer uses bars from the athletics a Maximum bending of 5 mm is no Problem, if we see a problem for 5 mm then we should allow a bending up to 1 cm
Comment
I don't know how much normal materials bend. Until I do, I'm very uncomfortable voting on a number here.
Comment
'The Sports Rules Book' (found it on google) says on p. 266
"The high jump standards (the upright and posts) are rigid. The crossbar may be wood, metal, or another approved material; its cross-section is circular and may be up to 3 cm in diameter. The bar may sag a maximum of 2 cm."
Other googling of US Track & Field documents didn't specify a maximum sag distance, but they did take care to note that measurements of the height should always be taken at the lowest point, even going as far to mark the bar to be sure they measure the correct position.