The stiffness of a pole increases exponentially

Got something for sale? Looking to buy something? Post it here, but make sure to read the rules first!

Moderator: rainbowgirl28

User avatar
kcvault
PV Pro
Posts: 333
Joined: Tue Sep 08, 2009 11:41 pm
Expertise: College vaulter, post collegiate vaulter, BA kinesiology,
Lifetime Best: 5.40m
World Record Holder?: Renaud Lavillenie
Favorite Vaulter: Annie Burlingham
Location: Turlock Ca

Re: The stiffness of a pole increases exponentially

Unread postby kcvault » Mon Dec 07, 2009 2:44 pm

FEA Finite Element Analysis allows one to build computer model of a pole and calculate the strands needed every 0.001mm one could if you had the time measure in nanometer.


Does this mean the weight of the pole is determined before the pole is made based on the material and amount of it that is used? If so with ESSX would that mean if you had two poles with a 182lb rating regardless of flex number the exact same amount of material was used on both poles?

---Kasey

User avatar
rainbowgirl28
I'm in Charge
Posts: 30435
Joined: Sat Aug 31, 2002 1:59 pm
Expertise: Former College Vaulter, I coach and officiate as life allows
Lifetime Best: 11'6"
Gender: Female
World Record Holder?: Renaud Lavillenie
Favorite Vaulter: Casey Carrigan
Location: A Temperate Island
Contact:

Re: The stiffness of a pole increases exponentially

Unread postby rainbowgirl28 » Mon Dec 07, 2009 4:34 pm

kcvault wrote:
FEA Finite Element Analysis allows one to build computer model of a pole and calculate the strands needed every 0.001mm one could if you had the time measure in nanometer.


Does this mean the weight of the pole is determined before the pole is made based on the material and amount of it that is used? If so with ESSX would that mean if you had two poles with a 182lb rating regardless of flex number the exact same amount of material was used on both poles?

---Kasey


Even if you use computer models of the patterns and use machines to cut them, each pole is still assembled by hand, and each batch of fiberglass has a slight amount of variation regarding the resin and such. Remember poles are baked, it's kind of like assembling a clay pot and firing it in the kiln. You can't perfectly control every little detail every single time, this is why manufacturers still flex the poles after they make them, even thought they know in advance what it should turn out to be. If there is any variation from the intended flex it is usually minor.

In a theoretical world/on the computer you probably could design a pole to within a precise nanometer of flex, but it's not possible to reproduce that in the real world.

User avatar
Capt Caveman
PV Fan
Posts: 47
Joined: Fri Sep 11, 2009 10:59 am
Expertise: Coach, Masters Vaulter, Parent
Lifetime Best: 5.05
World Record Holder?: Renaud Lavillenie
Favorite Vaulter: Scott Huffman
Location: North America....for now.

Re: The stiffness of a pole increases exponentially

Unread postby Capt Caveman » Mon Dec 07, 2009 5:03 pm

I thought i posted this on another topic, somewhere but i cannot locate it. I was speaking to an engineer friend of mine over a beer on evening and i turned the topic to vaulting (as i am sure we are all prone to doing). I was telling him about the poles and started talking about what length and wt pole i was using. He asked how the weight was determined and I explained the flex system to the best of my ability. He laughed and asked if i was sure that was how it was done. I asked why and he explained that since a pole is round, it is a colum, not a beam. Flex is a tool used in beam theory (think "I" beams, wood etc) and he was surprised that it was being used with a colum. Of course I am not an engineer so now I am confused. I can only assume that the accuracy is good but i cannot imagine that using the wrong test could ever be called accurate. It is as accurate as it can be based on years and years of doing it wrong and making it work. I guess.

I also noticed as i looked at the Essx pole sales page that they reserve the right to ship you a stiffer pole than you ordered to "increase delivery times". If this is true how often does it happen? The last time I needed a pole the dealer i was working with called the factroy and I got exactly the pole I wanted. It was in stock so I did not get something as a surprise.
Those who know WHY will always be victorious over those who only know HOW.

gtc
PV Whiz
Posts: 214
Joined: Fri Feb 04, 2005 2:41 pm

Re: The stiffness of a pole increases exponentially

Unread postby gtc » Mon Dec 07, 2009 6:22 pm

Todd,
Your 14'-3" Altius is about 5# stiffer than a 14'-0" let's say "pacer"
ie: If you had a 13'-9" 150 Altius, a 14'-0" 150 Pacer and a 14'-3" 150 Altius
The 13-9 would be about 5# smaller than the pacer and the 14-3 would be about 5# bigger.

User avatar
KirkB
PV Rock Star
Posts: 3550
Joined: Mon May 19, 2008 6:05 pm
Expertise: Former College Vaulter; Former Elite Vaulter; Former Coach; Fan
Lifetime Best: 5.34
Favorite Vaulter: Thiago da Silva
Location: Vancouver, BC, Canada

Re: The stiffness of a pole increases exponentially

Unread postby KirkB » Mon Dec 07, 2009 8:17 pm

Capt Caveman wrote: ... I was speaking to an engineer friend of mine over a beer ... and I explained the flex system ... and he explained that since a pole is round, it is a column, not a beam. Flex is a tool used in beam theory (think "I" beams, wood etc) and he was surprised that it was being used with a colum. Of course I am not an engineer so now I am confused. I can only assume that the accuracy is good ...

Yes, the accuracy is good ... or at least good enough for its purpose. Your engineer friend is partly correct ... a pole is a column, not a beam. To be even more correct, the pole is a tubular column ... it's hollow. This is what makes it so strong. Now compare that to a beam of wood ... which is NOT hollow, and is NOT a column. It's no fluke that Mother Nature made trees columnar ... but if they were tubular, they'd be even stronger. In a way, tree trunks ARE tubular! Each ring provides columnar, tubular strength to the tree trunk. By contrast, the beam's rectangular cross-sectional shape is sub-optimal. It's just shaped that way for ease of cutting. But if you can imagine a tubular column within the beam (or log), then the shapes are close enough that you can do a flex test on a tube.

One more thing ... the flex is always measured with the pre-bend down. So measuring the flex of a pole this way isn't much different than measuring the flex of a beam (which is usually measured with a flat surface ... usually the shorter side of the rectangle ... down).

If your friend is arguing that it's a crude measurement, then he has a point. The range of flexes ... to the nearest one-tenth of a flex ... gives only about a 100 points on a continuum ... not necessarily equi-distant points. So there's essentially only 100 different poles in the world that can be differentiated by flex alone. Not many, really ...

Your engineer should agree with this ... once you explain the rest of this to him.

BTW, I think the pole manufacturers have the precision to measure flexes to one-hundreth of a flex. However, that would provide more precision than what's necessary, and it would create an inventory nightmare. As you know, they'd prefer to just stock poles to the nearest 5 pounds, and sell you what they have in stock. This might be fine for HS vaulters, but when you approach elite levels, you need to be more precise than that.

Kirk
Run. Plant. Jump. Stretch. Whip. Extend. Fly. Clear. There is no tuck! THERE IS NO DELAY!

RamboRich
PV Newbie
Posts: 12
Joined: Sun Apr 12, 2009 5:25 pm
Expertise: HS Coach and Club Vaulter
Lifetime Best: 15'1"
Favorite Vaulter: Dutch Warmerdam
Location: Everett, WA
Contact:

Re: The stiffness of a pole increases exponentially

Unread postby RamboRich » Tue Dec 08, 2009 7:00 pm

I am a structural engineer for an aircraft company. I use FEA and hand analysis methods for the design of wing structure. Here are my thoughts: The flex rating is a measure of the linear stiffness of the pole (beam). It is calculated by the use of classical beam bending theory (Mc/I). It is a very simplified approximation of a beam. This method is only valid for linear behavior, or in other words it assumes linear behavior. The method will be very good provided that the deflections of the pole are very small. This is not the case with a pole vault pole. This is one reason why poles of the same flex rating can feel different. The large pole deformations experienced coupled with a time dependant loading function cause pole dynamics to be very difficult to simulate with any analysis method including FEA.
I would argue that the best and most economic solution for rating the stiffness of poles is test data. I belive that some of the pole manufacturers bend each pole tip-to-tip dynamically. These large deformation tests provide the most realistic and useful data. Now provided that test data is collected, it is possible to establish an analysis method that correlates to the test data. Once this correlation model is made, all subsequent pole stiffnesses could be predicted very accurately. However, if the composite layup is modified (sail pattern changed, or ply angle changed) then the model is no longer valid. This is why it is very difficult to compare the pole performance between two manufacturers. One could get a great comparison if a manufacturer wanted to spend the time and money to purchase and test other brands. This would provide a common standard for comparison. Some reverse engineering may also have to be used to determine the layup of the tested poles. Testing is also very good because it will include any variation in the manufacturing process which is very important with composite materials.

"FEA Finite Element Analysis allows one to build computer model of a pole and calculate the strands needed every 0.001mm one could if you had the time measure in nanometer. This finite structure can be built for function and performance without failure and best when you have the program model made by an engineer who understand the pole vault , and a World record holder and myself who has studied the pole vault for many years all calculating the needs for the vaulters."

In my opinion FEA (no matter who the user is) will not solve the issues of designing poles and assigning flex ratings that compare with different manufacturers. This is because an analysis is only as good as its assumptions. In my mind the only way to see how 'stiff' a pole really is.. is to jump on it. IMO

User avatar
Bruce Caldwell
PV Enthusiast
Posts: 1783
Joined: Thu Feb 27, 2003 3:19 pm
Expertise: It is all about Pole Vaulting. I even catch the competitors poles!
Lifetime Best: 15'8"
Favorite Vaulter: Kjell Issakson, Jan Johnson
Location: DFW TEXAS
Contact:

Providing the info you think you need will further confuse

Unread postby Bruce Caldwell » Wed Dec 09, 2009 10:03 am

I assure you providing a chart will make all poles go up in price due to every one trying to order a flex number that will not read on their system compared to the factory.
I moved my apparatus around from cat-pole to Mexico to California to Texas then to the other side of the building and each time I did it was very difficult to rest exactly. due to so many variable the unit has to measure.
One company uses a different weight ? another uses a light bulb to cast a shadow for the measure not realizing that when the pole deflects down and the light is stationary the shadow is not more above the pole giving a .2-3 difference and then they measure in inches which is less accurate. But it is so minute of a difference that there is no a concern for safety just a little lack of consistency! They make it all up with the very best lamination and visual consistency of their pole over all others. SO when once asked if flex number inconsistency was a danger between brands the findings were so minor it was not a danger!

But keeping it simple one can just set the frictionless supports 12" in on each side and use a 50 lbs weight!
This will give you a very close measure that will work for all poles. IT will not be exact and the difference between a 16.0 and 16.5 is very little like 2 lbs!!!!
SO one could set up and get a relative stiffness between their own poles but lets not try to align it up for every brand it would be very tough.
I did come up with a mathematical calculation to estimate other brand flexes in relation ship to mine and you will find this on the smart label that should be all you will need to compare!
I really believe far too many put too much faith in the flex system and we need to just go to system that measures 145, 146, 147, 148, 150, 151, etc.
The problem is when one orders a 147 and they get a 148 their hair stands up and they complain, when in reality they ordered today in other brands a 145 and got a 148 they just did not know it!!
http://www.officialessx.com
Last edited by Bruce Caldwell on Sun Dec 13, 2009 6:03 pm, edited 1 time in total.

Divalent
PV Whiz
Posts: 149
Joined: Tue Oct 27, 2009 11:31 am
Expertise: Parent
Lifetime Best: 0-00.00
World Record Holder?: Renaud Lavillenie
Contact:

Re: The stiffness of a pole increases exponentially

Unread postby Divalent » Wed Dec 09, 2009 2:02 pm

What determines the particular weight rating that is assigned to a particular pole? I know each MFG has a table that does this based on length and flex, but what is the method or rationale for constructing *that* table?

What I'm getting at is, what determines that a particular pole is only safe for vaulters weighing less than (say) 150 lbs, as opposed to (say) 175 lbs?

And a related question: if a pole from one MFG was tested by another MFG, would both MFGs assign the same weight limit?

User avatar
Bruce Caldwell
PV Enthusiast
Posts: 1783
Joined: Thu Feb 27, 2003 3:19 pm
Expertise: It is all about Pole Vaulting. I even catch the competitors poles!
Lifetime Best: 15'8"
Favorite Vaulter: Kjell Issakson, Jan Johnson
Location: DFW TEXAS
Contact:

Re: The stiffness of a pole increases exponentially

Unread postby Bruce Caldwell » Sun Dec 13, 2009 6:16 pm

Capt Caveman wrote:
I also noticed as i looked at the Essx pole sales page that they reserve the right to ship you a stiffer pole than you ordered to "increase delivery times". If this is true how often does it happen? The last time I needed a pole the dealer i was working with called the factory and I got exactly the pole I wanted. It was in stock so I did not get something as a surprise.

Answer to your question rarely however if you ordered a 147 weight and got a 149 I think that is better than ordering from another company a 145 and getting a 147 or a 149 but it is marked 145!
There have been a few times one wanted a 17.7 flex and I sent a 17.6 flex My point here is in the past I have seen companies ship 149 marked 145 and I have also seen a 143 shipped out as 140. And with the way they make their sail piece you will take days to move to the next pole as a pose to moving fluently t from one ESSX to another.

I always was concerned when the international market ordered a 54 kilo and got a 120 test pole????? 54 x 2.2 K= 118.8
IS it a 118.8 or is it a 120lbs? the size on the poles says 54 kilo
. What happens when you move to a 125 or 130 if they do not go in 5 lbs increments you only choice is a 130? Are you moving from a 118 to a 125 or 130? can you tell by the flex? NO!
A 2.2 lbs increase in the size you order is so much finite over a 10-12 lbs increase?
Bruce Caldwell

User avatar
Bruce Caldwell
PV Enthusiast
Posts: 1783
Joined: Thu Feb 27, 2003 3:19 pm
Expertise: It is all about Pole Vaulting. I even catch the competitors poles!
Lifetime Best: 15'8"
Favorite Vaulter: Kjell Issakson, Jan Johnson
Location: DFW TEXAS
Contact:

FEA works if U know fiberglass, vaulting & the software!

Unread postby Bruce Caldwell » Sun Dec 13, 2009 6:29 pm

RamboRich wrote:I am a structural engineer for an aircraft company. I use FEA and hand analysis methods for the design of wing structure. Here are my thoughts: The flex rating is a measure of the linear stiffness of the pole (beam). It is calculated by the use of classical beam bending theory (Mc/I). It is a very simplified approximation of a beam. This method is only valid for linear behavior, or in other words it assumes linear behavior. The method will be very good provided that the deflections of the pole are very small. This is not the case with a pole vault pole. This is one reason why poles of the same flex rating can feel different. The large pole deformations experienced coupled with a time dependent loading function cause pole dynamics to be very difficult to simulate with any analysis method including FEA.
I would argue that the best and most economic solution for rating the stiffness of poles is test data. I believe that some of the pole manufacturers bend each pole tip-to-tip dynamically.

Analysis of a bending pole tip to tip would not emulate the bending of the pole by a vaulter! So you are correct the info you get here is really worthless. see this page for how we bend and test poles! http://www.xlogicsports.com/home/ Then select sport staff
RamboRich wrote: These large deformation tests provide the most realistic and useful data. Now provided that test data is collected, it is possible to establish an analysis method that correlates to the test data. Once this correlation model is made, all subsequent pole stiffness could be predicted very accurately. However, if the composite layup is modified (sail pattern changed, or ply angle changed) then the model is no longer valid. This is why it is very difficult to compare the pole performance between two manufacturers. One could get a great comparison if a manufacturer wanted to spend the time and money to purchase and test other brands. This would provide a common standard for comparison. Some reverse engineering may also have to be used to determine the layup of the tested poles. Testing is also very good because it will include any variation in the manufacturing process which is very important with composite materials.

You are correct again and frankly I was never interested in reverse engineering others poles and spend over $200,000 to copy others ideas that for years seem to hold athletes back! For years one company led you to believe that their pole came back faster than any other pole out there! They had a machine to show you in demos and company tours their device lifted a 100lbs weight and threw it hight in the aaaaaaaair faster than my pole! They were telling the truth their pole did come back fast, too fast, and for years you saw vaulters clear heights by 2-3 feet over the bar and they come down on the bar! As a result you opened the door to cheating with vol-zing and moving the bar out of the way and steadying it to clear the bar til it was banned.
You will feel the ESSX pole lift you over the bar with penetration to clear the bar and you will not get the action of too much return common in improperly made CARBON POLES! Using Carbon to stiffen the pole and reduce some weight is wonderful but to use the CARBON to make the pole return fast destroys the concept of the double Pendulum needed to jump very high!
If one maintains consistency in the formulas such as distance between short side of sail and butt is correlated throughout the line as a comparable and relative to the length of the pole. Your response confirms what I am trying to say all perimeters must be mathmatically consistant and changing the process will change the line unless it is part of the structure of the line's concept!
And that the sail wraps are set to be the same wraps of hoop and body wraps combined, then you will have a line that has been formulated and the vaulting process has been maintained throughout the whole line (10'8" the exception) Then adding a carbon stiffness that has specific width and gaps measured mathematically and determined by the diameter of the manderel and the relative to the poles stiffness position, wraps, types of glass, then again you have knowledge input and knowledge of the vaulting process, the pole making process, the stiffness of the pole relativity process, and engineering! FEA software if used properly, not just a tool to find stiffness but properties up and down the pole inside the pole and its reaction to stress, tensile strength, and modular compression.
Other words something no one else has, a properly engineered pole!
RamboRich wrote:"FEA Finite Element Analysis allows one to build computer model of a pole and calculate the strands needed every 0.001mm one could if you had the time measure in nanometer. This finite structure can be built for function and performance without failure and best when you have the program model made by an engineer who understand the pole vault , and a World record holder and myself who has studied the pole vault for many years all calculating the needs for the vaulters."

In my opinion FEA (no matter who the user is) will not solve the issues of designing poles and assigning flex ratings that compare with different manufacturers. This is because an analysis is only as good as its assumptions. In my mind the only way to see how 'stiff' a pole really is.. is to jump on it. IMO


Yes you are correct if you do not know anything about pole making, carbon, or vaulting! But I had two engineers one in carbon composites the other from NASA, Earl Bell, and myself all establishing the input properties and formulas needed to form a complete line starting over not using any thing I had seen or learned in pole patterns before. (nanometers can be established within math equations, that is why it is called finite and often rounded up grin)
So for the third time in the post I will again agree with you
the only way to see how 'stiff' a pole really is.. is to jump on it.


Call it radical, call me the RENEGADE POLE DESIGNER but this system works really well and you will never know unless you try the poles.

Bruce Caldwell

User avatar
Bruce Caldwell
PV Enthusiast
Posts: 1783
Joined: Thu Feb 27, 2003 3:19 pm
Expertise: It is all about Pole Vaulting. I even catch the competitors poles!
Lifetime Best: 15'8"
Favorite Vaulter: Kjell Issakson, Jan Johnson
Location: DFW TEXAS
Contact:

Re: The stiffness of a pole increases exponentially

Unread postby Bruce Caldwell » Sun Dec 13, 2009 7:18 pm

Divalent wrote:What determines the particular weight rating that is assigned to a particular pole? I know each MFG has a table that does this based on length and flex, but what is the method or rationale for constructing *that* table?

What I'm getting at is, what determines that a particular pole is only safe for vaulters weighing less than (say) 150 lbs, as opposed to (say) 175 lbs?

And a related question: if a pole from one MFG was tested by another MFG, would both MFGs assign the same weight limit?

Let me answer your question this way and you may see the light!
(Wall thickness and hoop strength!)
If you took a 15'-135 and you cut 6" off the butt and you cut 12" off the top you would have 13-6-154 if you only considered its stiffness by the flex number only!
However if you were to look at the amount of wraps a 15-135 has and the amount a 136"-154 has you will see the 13-6"-154 has 1 more wrap than the 15" pole. So even though the flex is correct the amount of wall or hoop structure is not enough to hold a 154 lbs person safely!
You would also have to hold at the very top to roll the pole over if you could and if you rolled it over too much the pole would break!
The reaction of this pole would also return to vertical prematurely and the angle of return would be towards the pit and not upwards. But you would, based on the flex have a 13'6"-154 but it would not be safe nor could you vault properly on it!
Just like I could cut you a 2" PVC pipe out of PVC and it would flex like a 125lbs vault pole at 12'4" in length but is not safe to vault with!

Bruce Caldwell

Divalent
PV Whiz
Posts: 149
Joined: Tue Oct 27, 2009 11:31 am
Expertise: Parent
Lifetime Best: 0-00.00
World Record Holder?: Renaud Lavillenie
Contact:

Re: The stiffness of a pole increases exponentially

Unread postby Divalent » Sun Dec 13, 2009 11:09 pm

ESSX wrote:
Divalent wrote:What determines the particular weight rating that is assigned to a particular pole? I know each MFG has a table that does this based on length and flex, but what is the method or rationale for constructing *that* table?

What I'm getting at is, what determines that a particular pole is only safe for vaulters weighing less than (say) 150 lbs, as opposed to (say) 175 lbs?

And a related question: if a pole from one MFG was tested by another MFG, would both MFGs assign the same weight limit?

Let me answer your question this way and you may see the light! ...


That was interesting (really!) but I think you misunderstood my question. It was really a lot simpler (I think). Let me try to reframe it based on your example. Forget the cut downs, or wraps or anything else. You have a pole that you label a 15'-135, because after you made it, you tested the flex, and found that's what it was. My question is, given the flex you measure, why do *you* call it a 135 lb pole, and not a 130, or 140 or 150?

What I'm trying to get at is the basis for the requirement in HS that a vaulter vault on a pole rated at or above their weight. Why, in your opinion, is that 15-135 pole unsafe for anyone over 135? (I say "in your opinion" because you label it, and with a 135 label, a 140lb athlete would be DQ'd if they used it in a HS meet, but if you labeled it 145, that *same* pole would be legal. So whatever *you* (and only you) say about the pole determines whether it is legal for a particular athlete).

I presume at this point that you have a table of pole lengths and flex numbers that allows you to assign a weight rating for whatever you make based on those measurments. But how did you decide that (made up example ---> ) a 15' pole with a 17.3 flex is a 135 (or whatever) as opposed to some other maximum weight? IOW, what's the rationale behind the table you use?


Return to “Sales Forum”

Who is online

Users browsing this forum: No registered users and 5 guests