[OverandOnward]

A lot of thoughts and opinions, technical factors and suggestions ... this thread could be for all that - re the 2012 Rolex x-country #9a frangible pin that broke and dropped the rail. The horse dragged over it, but was not falling.

It's been said that Clark caught some misfortune when his horse did advance through flags at 9a
http://www.rk3de.org/virtual_fence.php?id=9

... but the pins broke and brought down the log, costing Clark 21 penalties.

Of course the pins that allow the log to fall are intended to save rotational falls. Would Clark & Glen have fallen without the pin break? Perhaps an engineer can suss that out definitely.

My editorial comments:

I don't know that it matters if the pin saved Clark & Glen, or if they would have been fine without it. There is no way to precisely engineer for every unknown future passage with a horse dragging itself over. Eventing has to accept that pins or any other technology won't be so precise that no one ever gets a bad break (no pun intended.)

Eventing safety has to stick to principals and to lessons so painfully learned. Perhaps that particular pin needs some re-engineering to break differently. But, although it may cost a few competitors unfairly, it is right to do something at that type of jump. The log rail of that type has figured statistically in falls and rotational falls. It absolutely must be targeted as a safety collapsible. And any jump at the top of a drop is going to be more dangerous if a horse tips over.

I am so very sorry for Clark's penalties as I think he & his horse have much promise for future teams. But in the larger context I can live with some major disappointments if it will save someone or some horse from a dreadful fate.

Don't step back from the primary focus on preventing the worst falls, just because sometimes a rider gets penalties they would not have before the frangible pins.

Other thoughts?
Suggestions for jump & pin design standards?
Opinions on principals and policy?

[Lord Helpus]

I read a post yesterday in which the poster thought/questioned that the pin broke because it was weaken by prior horses hitting the log.

I disagree ---- There was a 25 minute hold on course right before Karen went because the pin had been broken by the prior horse (I forget who now). The officials were making 100% sure that the jumps were the same for everyone.

I jump judge quite often and even at smaller competitions, it is our responsibility to make sure the footing, flags, jumps are the same for each competitor. Should anything change beyond our ability to fix (i.e. a flag down) we call for course maintenance immediately and they are there within several minutes.

I believe that the pins would have been checked by an official after any horse hit the jump. When the pins broke as Clark jumped, they would not have been weakened by prior horses. If they had been, they would have been changed out immediately.

The chances of a pin breaking is directly attributable to the angle at which the jump is hit.

Just as in show jumping. The comment has been made that a certain horse "knows how to rub a rail" because the angle of the contact is such that the jump often stays up, even if hit hard. While other horses may catch a rail with a wiff of air or a tic of a toe and the jump comes down.

Good luck for the former, bad luck for the latter, but a rule is a rule.

[riderboy]

Vineyridge was there and I hope she responds here. She had an excellent post on this on another Rolex thread.

[Plumcreek]

Nice post, LH

[faybe]

Lord Helpus, I understand what you're saying but my point is that you can't see with your naked eye the compromised integrity of the pin. It can look level and in place, but the material the pin is made of will have microfractures from being repeatedly hit, which weakens the integrity of the pin and lowers the threshold load the pin needs to break completely. Maybe that interpretation is completely off base (Reed or any other physics-minded folks can chime in any time...) but that's my understanding of it.

[SimplyRed]

I was at jump 9 for awhile. They would check the pins after any horse that touched the jump. I didn't ever see it break, and it did break for I believe, the first or second rider on course. They did their job, in my opinion. 400 pounds of weight on them and they would break.

[RAyers]

...

I believe that the pins would have been checked by an official after any horse hit the jump. When the pins broke as Clark jumped, they would not have been weakened by prior horses. If they had been, they would have been changed out immediately.

The chances of a pin breaking is directly attributable to the angle at which the jump is hit...

And I would say you are mistaken. Faybe is SPOT on. There is NO way to determine the fatigue state of ANY material by visual inspection other than AFTER it failed. I can assure you that there are parts on your car, in your house, in you (if you have any medical implant), that are about to fail and you will NEVER know until it actually breaks.

The pins CAN and ARE weakened by prior hits, regardless of force. That is a fundamental aspect of metallurgy/materials science (specifically what is called the endurance limit).

I could break one of those pins with a light hammer tap if I do it enough times. Hell, I worked a case last year where 4 hits shattered part of a 60lb heavy gauge steel pin causing injury. There was no way to predict it.

My suggestion is that a failure analysis should be done for EVERY failed pin for an extended period to determine the causes and mechanisms of the failure at the material level. Then the pins can be designed accordingly.

Reed

[2ndyrgal]

Right next to it. I watched the crew replace EVERYTHING. It was amazing.

From where I sat, it worked exactly as it was supposed to, ie, it sort of slowly collapsed. Had that horse, or another, tried to "climb" over, it might have gone terribly wrong.

And as for someone complaining that the fence cost them points, well, jump clean and you'll not have a problem.

[faybe]

Right next to it. I watched the crew replace EVERYTHING. It was amazing.

Unless they replaced the pin after every rub the fence received, regardless of whether or not they thought the pin "moved" from looking at it grossly, they did not replace "everything". See Reed's post, above.

And as for someone complaining that the fence cost them points, well, jump clean and you'll not have a problem.

But do we really WANT cross country horses that will show jump everything? I want an xc horse that's economical, that is smart with its body and that won't be punished for taking a feel of a fence that we've trained them won't fall down. It's all a moot point since the rule is the rule, but I find the above statement to be a bit ridiculous (unless you have jumped around a 4* with nary a rub yourself? In which case I guess you're entitled to that opinion).

[Janet]

My suggestion is that a failure analysis should be done for EVERY failed pin for an extended period to determine the causes and mechanisms of the failure at the material level. Then the pins can be designed accordingly.

Reed

Reed,

I know that when there are large time spans involved, failure analysis can determine if there was (micro) structural damage before the incident that caused a failure (e.g., oxidation on the surfaces).

Can you do the same thing when the time span is only minutes?

[pegasusmom]

My suggestion is that a failure analysis should be done for EVERY failed pin for an extended period to determine the causes and mechanisms of the failure at the material level. Then the pins can be designed accordingly.

Reed

I am sure if I am wrong someone will correct me, but I believe there is a cooperative study in place with the British Horse Trial society and University of Kentucky to do just that.

Pin stress not withstanding, the repair crews were terrific, and checked fences with pins anytime a horse hit them. Certainly in the area I was placed as area steward our repair guy was johnny on the spot 100% of the time.

No system is 100% perfect.

[Holly Jeanne]

I disagree ---- There was a 25 minute hold on course right before Karen went because the pin had been broken by the prior horse (I forget who now). The officials were making 100% sure that the jumps were the same for everyone.

I can't comment on what was taking place on course but, there was a 17 minute hold on course after the first rider (Andrew Nicholson)(Karen followed him as the second rider), another four minute hold a little later in the morning, and another hold after James and Parker fell in the afternoon. I didn't hear what led up to the holds but I'm very glad to hear that the officials were so careful in looking into the safety of the jumps!

[bambam]

Unless they replaced the pin after every rub the fence received, regardless of whether or not they thought the pin "moved" from looking at it grossly, they did not replace "everything". See Reed's post, above.

But wasn't the first horse who brought it down with people questioning whether it should have come down, the 4th or 5th person on course? At least 1 if not more of the horses before him did not make it to fence 9 at all (Karen and Veronica only made it to 5). So, assuming they started with a new pin (which I will assume since it was Rolex), that pin had taken maybe a couple of hits at that point. While there could have been enough damage to the pin to affect whether the rail dropped (whether from the type of hit it took from one of the earlier horses or an issue with the materials in the pin), it seems unlikely.
I know the stress on those pins after many hits is a question and I think it should be looked into, but I just think that is the less likely answer for it coming down here.
And, while the 21 points were unfortunate for Clark, since he fell off later, they were ultimately irrelevant to his score.

[RAyers]

Reed,

I know that when there are large time spans involved, failure analysis can determine if there was (micro) structural damage before the incident that caused a failure (e.g., oxidation on the surfaces).

Can you do the same thing when the time span is only minutes?

Yes, you can. I have done failure analysis on kinetic energy penetrators where the failure time is <10^-6 seconds. Additionally there are indicators on the fracture surfaces that show exactly how something failed, including the presence of corrosion, e.g. stress corrosion cracking, pitting corrosion. How a material fails is always evident in the surfaces left over after failure. Even handeling and storage of the pins can cause the metal to fail prematurely.

Pegasusmom, does UK have a metallurgist involved? I thought it was only a mechanical engineering effort? Mechanical engineers are taught to look at materials as black boxes and generally are not really good at root cause failure in a material. And yes, it is good that the crews were there.

Yes, the pin prevented a possible bad situation. However, the use of pins opens up a whole new area of questions. The competition analogy would be wind blowing a lightly set rail down during a jumper round. Should the rider get 4 faults even if the horse did not touch the rail?

The immediate answer is to replace a pin after EVERY hit, regardless of severity. Never leave the pins in place after a competition (reduce metal CREEP). Store the pins out of the weather.

As for me personally, I want my horse to be willing to hit the fences. There are times where I want them to scrape over to help them balance for the next effort. I don't want a horse, nor do I want to try, that never touches the fences.

I am not questioning the use of pins. They are an advancement of the safety technology. However, one can begin to address the OP's questions and other's assumptions by following the bolded ideas.

[S A McKee]

.

Yes, the pin prevented a possible bad situation. However, the use of pins opens up a whole new area of questions. The competition analogy would be wind blowing a lightly set rail down during a jumper round. Should the rider get 4 faults even if the horse did not touch the rail?

[B]The immediate answer is to replace a pin after EVERY hit, regardless of severity. Never leave the pins in place after a competition (reduce metal CREEP). Store the pins out of the weather.

.

Poor anology. The judge will signal the rider to stop if jumps blow down.
Show jumpers use pins/cups to hang rails. Nobody is complaining that the device be replaced every time a rail is hit. It doesn't need to be done.
Seems cheaper to get 21 faults than to have a horse or rider maimed,crippled or killed. Or don't you think preventitive measures are a good idea?

[fooler]

Yes, you can. I have done failure analysis on kinetic energy penetrators where the failure time is <10^-6 seconds. Additionally there are indicators on the fracture surfaces that show exactly how something failed, including the presence of corrosion, e.g. stress corrosion cracking, pitting corrosion. How a material fails is always evident in the surfaces left over after failure. Even handeling and storage of the pins can cause the metal to fail prematurely.

Pegasusmom, does UK have a metallurgist involved? I thought it was only a mechanical engineering effort? Mechanical engineers are taught to look at materials as black boxes and generally are not really good at root cause failure in a material. And yes, it is good that the crews were there.

Yes, the pin prevented a possible bad situation. However, the use of pins opens up a whole new area of questions. The competition analogy would be wind blowing a lightly set rail down during a jumper round. Should the rider get 4 faults even if the horse did not touch the rail?

The immediate answer is to replace a pin after EVERY hit, regardless of severity. Never leave the pins in place after a competition (reduce metal CREEP). Store the pins out of the weather.

As for me personally, I want my horse to be willing to hit the fences. There are times where I want them to scrape over to help them balance for the next effort. I don't want a horse, nor do I want to try, that never touches the fences.

I am not questioning the use of pins. They are an advancement of the safety technology. However, one can begin to address the OP's questions and other's assumptions by following the bolded ideas.

Reed thanks for a clear,concise commentary about these pins. I agree that the pins are a good idea for safety, BUT it is not the only answer. Plus the use of pins is not as clear and simple as many would like us to think.

[Janet]

The immediate answer is to replace a pin after EVERY hit, regardless of severity.

It seems to me that, if you are going to do that, you should also ANALYZE each pin that has been replaced after a hit. Over a large smaple size, it should then be able to get a better picture on what (if any) damage is done by each hit.

[fooler]

Poor anology. The judge will signal the rider to stop if jumps blow down.
Show jumpers use pins/cups to hang rails. Nobody is complaining that the device be replaced every time a rail is hit. It doesn't need to be done.
Seems cheaper to get 21 faults than to have a horse or rider maimed,crippled or killed. Or don't you think preventitive measures are a good idea?

Not if the fence has already been jumped. Then the judge has to determine if the horse touched the rail,causing the rail to fall or if the horse jumped the fence with room and the rail fell because of wind or another issue. And yes I judged at an event where the winds were heavy enough that it was necessary to stop SJ long enough to totally rebuild two fences that keep being blown down.

[2ndyrgal]

What force exactly, is required for the pin to break/disconnect, etc? Because, as Reed said, (and I should have said better) it is reasonable to expect horses to slide/crawl/hang a leg, whatever, over that type of jump. So what is the criteria for the use of either a frangible pin or one of those styrofoam type logs? A certain height,width,drop?

And on obstacles like the flower box or a big table or produce stand, you only have skill and luck, there's no real way to make every jump in a manner that prevents rotational falls.

[RAyers]

Poor anology. The judge will signal the rider to stop if jumps blow down.
Show jumpers use pins/cups to hang rails. Nobody is complaining that the device be replaced every time a rail is hit. It doesn't need to be done.
Seems cheaper to get 21 faults than to have a horse or rider maimed,crippled or killed. Or don't you think preventitive measures are a good idea?

In my jumper days, I had it happen several times. I would jump a fence and even after a few strides, the rail would come down. It was the judge's discretion to award the penalties. Did the horse actually touch the rail or not? Was the drop the result of the horse even if the horse has already galloped off? Did the rub as the result of the previous horse roll the rail sufficiently to barely be supported?

That is why in those days I made the jump crew go and reset any rails I had questions about. I would do the same on XC if it came to that.

I think the analogy is spot on.

Janet, that is exactly what I propose. Only in that way will we have some assurance to the lifespan and capability of the pins.

Reed