flex numbers

[starkey480]

why is it that the flex to pole weight ratio is different among pacer carbons and spirits? my 14'7 17.4 pacer is a 170 whereas my friends spirit 14'7 17.4 is a 180? i have seen this on multiple occasions and it seems like in the 14'7 to 15'7 range spirits are 10 pounds heavier for the same flex?

[Barto]

Gill decided that their 17.4 was going to be called a 170. UCS decided that their 17.4 was going to be called a 180. Understand that the weight rating of the pole is just a name given to a particular pole. The 170 could just as well be called a Pacer Camero and the 180 be called a UCS Mustang. They might both have 5.0 liter engines, but that doesn't mean that they are the exact same car.

[rainbowgirl28]

UCS and GIll flex their '6/'7 (like 13'7, 14'7, 15'7) poles on totally different spans, so you REALLY can't compare the flexes. Their 13'/14'/15'/16' poles are on similar spans, so the flex numbers are usually somewhat comparable at those lengths, but it's not an exact science for a variety of reasons.

[Decamouse]

Becca hit it pretty close to the head -- Gill changes span at every length change (6") up to 490 than 10 cm -- Spirit was as every foot - so the 6" poles do not match between Spirit and Gill -- do the math - use the beam equation and you will get close to what the difference in flex would be -- the bigger the flex and shorter the pole the less accurate -- been a bit written about this subject already

[starkey480]

so in that case how would you tell what pole is stiffer? or is it just not possible to tell

[Barto]

My experience is that the weight ratings between Pacers and Spirits are pretty close to the same. I'm betting the Spirit is bigger.

[rainbowgirl28]

My experience is that the weight ratings between Pacers and Spirits are pretty close to the same. I'm betting the Spirit is bigger.

I've found they vary a little more between the two brands in 12' and shorter, but for the longer poles they are usually pretty close. +/- 5lbs max generally, so generally any 180lb pole of either brand will be stiffer than a 170lb pole of the same length.

You can build your own flex machine to get a rough idea of how poles compare as well. Dig through the posts here, it's been discussed before.

[ClintonMagus]

It's not really this complicated, but here is a reference:

http://polevaultpower.com/forum/viewtop ... ne#p138069

[Decamouse]

It is not difficult - the reference above gives the correct overall picture - some inaccuracy in talking about Gill --

now regarding a good estimate -- 15.7 for the flex -- without testing that will be ball park

Did I pull it out of the air -- no this number would be based on Engineering formulas - take the beam deflection formula - cancel out like terms (ok "I" does vary throughout the length of a pole) - result is Deflection (flex number) = 17.4(given flex) x (length cubed)/(length cubed)

The length for simiplicty was 14.5 and 15

Note that number would also translate to a 180 lb rating for Gill 14'6" pole

It is explained in detail on see: viewtopic.php?f=8&t=20107&p=143700&hilit=Engineer#p143700

More info if you are real bored at http://www.decamouse.com on the "Ramblings on pole vault poles" page