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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?

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.

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.

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

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

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

Barto wrote: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.

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

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

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