We have most recently receive an email about a pole breaking where the athlete was 150 lbs on a 12'4"-136 test pole.
They stated that based on the relative stiffness chart the pole holding at 10' should have been stiffer at the lower handgrip?
All manufacturers and the NFHS state that you must use a pole rated at or above your weight at all times especially in competition and in practice.
While it is correct on any brand pole holding lower does increase the stiffness of the pole.
A vaulting pole has several means of support of its fiberglass structure.
To keep it simple we will discuss two of them:
1. Stiffness of the axis (How stiff is the pole at a given handgrip)
a. How stiff the pole becomes from longitudinal strength of the liner axis of the glass.
b. This is affected by the body wrap , the hoop wrap and the sail wrap of the pole.
2. The hoop strength (how strong is the hoop at a given hand grip)
a. This part of the pole that helps it to maintain its hoop structure and keeps the pole from becoming elliptical.
b. A pole that becomes too elliptical has sidewall failure and will break if the hoop strength is not supportive of the amount of wraps and the diameter of the mandrel to support the weight it is intended to support.
c. Hoop strength keeps the pole circular for a given weight and design.
Yes by lowering your hand grip the pole gets stiffer as a rule of thumb about an est. 1.2 lbs per inch within the top 12" to 18"
Below that the pole gets stiffer at a rapid rate per inch (2.2 per inch first 3" and then a much larger number per inch there after)
The hoop however does not get stronger as you move the handgrip down, so a 136 lbs pole cannot support a 150lbs vaulter and the pole if loaded improperly will break.
I understand many of you have had vaulters go with the pole at the take-off and not break a pole rated below their weight. Proper vaulting technique is less stress on poles if the load does not over bend the pole.
If the pole has struck the crossbar, hit the standards, or has not been caught after each vault, a fatigue area may develop and will break when using the pole especially as a warm-up pole rated below your weight no matter the take-off angle.
The first break will occur in the top of the pole (24" to 36" from the top) at the weakest area of fatigue and then energy stored explodes to the rest of the pole and you get 3, 4, or 5 pieces with the tops being smaller and the centers longer.
If a flying spike has struck the pole, it has been stepped on, or not caught at take-off the pole can fail in the center of the pole or where the fatigue started and the amount of pieces will be two.
It is NOT impossible for a pole to be great for a week to 4 years and then break due to a defective pole.
It is possible for a pole to work great for 1 week to 4 years and break due to misuse, abuse, or nicks that fatigues the pole and results in breakage on subsequent jumps.
All Manufacturers test their poles before they ship them
In fact this test is inclusive and if the part is defective it will break on the manufacturers machine!!
No vaulting pole is guaranteed that it will not break. But if used properly, taken care of , and not abused a vaulting pole any brand should last!
