Driver safety and component failures

[Ciro Pabón]

Well, thanks, Mac. To be fair, I just want to add that WhiteBlue has a good couple of points:

- This is a "proper thread", analysis of accidents is entertaining and goes with the forum perfectly, thanks for starting it.
- McLaren and FIA should be worried.
- Mr. Surer and WhiteBlue can be perfectly right about the cause of the accident (probably they are, btw).

I just add that I assume they're worried. After all, we don't want an accident to happen to Hamilton for McLaren to lose the WDC position to BMW, do we? (that was a joke, that was a joke...)

[Carlos]

"Vodafone McLaren Mercedes and its Official Supplier of wheels have now conducted a thorough technical investigation to determine the exact cause of the failure.
"It has been established that, owing to a process fault during manufacture, the outer clamp surface of the wheel was given a clear lacquer coating. As a consequence of this fault, the clamp load that attached the wheel was not to specification.
"In running, the consequent loss of load caused the wheel to fret and distort, leading to its eventual failure.
"Vodafone McLaren Mercedes and the wheel supplier have now established new procedures designed to prevent a re-occurrence of this issue."
planetf1.com

Here's the article:
http://planetf1.com/story/0,18954,3213_3537465,00.html

Ciro - Do you have any other pictures of Wikipedia is accurate citation? That T-shirt certainly convinced me

[WhiteBlue]

All right, so Mr. Surer has an eagle eye. How did he noticed that the wheel nut came loose? I have not been able to get a video from the left side of the car, please, be kind to show it to us...

well he did not notice the wheel nut coming loose but he noticed the similarity of the accidents and had his studio cut the two recordings to show the accident simultaneously. I actually have the 3 hour mpeg of the race and isolated the 30 s sequence. I will try to cut it and put it on youtube. it will not be long there.

McLaren actually confirmed that in both cases the wheel nut came loose. At first they took the opportunity to speculate about the stone getting in there after the race. and now their report is using different names for the same thing. they are now calling it a clamp. but the fact remains that in both cases the wheel nut came loose. I conceede that it could have had different causes. but on the other hand I would be surprised to have two similar accidents with loose wheel nuts and subsequent rim failures caused by totally different causes. what is the probability of that?

[Ciro Pabón]

AFAIK, Carlos post settles it: it was the wheel nut, you don't have to post the video, thanks anyway (as you say, FIA will retire it in minutes...).

Just another question: was the first accident also caused by the lacque?

Note to Carlos: you can get the T-shirt at Busted Tees, here (the photo at their site is sad...) http://www.bustedtees.com/wikipedia

[WhiteBlue]

AFAIK, Carlos post settles it: it was the wheel nut, you don't have to post the video, thanks anyway (as you say, FIA will retire it in minutes...).

Just another question: was the first accident also caused by the lacque?

..More concerning is the fact that both wheel rim failures of McLaren were eventually caused by the wheel nut coming loose. So we cannot exclude at this time that they kidded themselves about the root cause of Hamilton's Nürburgring accident. It looks more and more that those were very similar failures indeed.

It has been established that, owing to a process fault during manufacture, the outer clamp surface of the wheel was given a clear lacquer coating. As a consequence of this fault, the clamp load that attached the wheel was not to specification. In running, the consequent loss of load caused the wheel to fret and distort, leading to its eventual failure.

so we have an incorrect coating causing the wheel to come loose and that led to over heating of the wheel and failure. why are they now calling the wheel nut a clamp? they said the nut came loose in the hamilton accident as well. why did that one come loose? same coating fault?

you see here that I earlier quoted the original McLaren press statement which Carlos reposted. and I asked the same question of the laquer or coating!

that would be interesting to know. if McLaren really attribute both events to different root causes it would be really freaky. I could imagine that they found it was the same thing but they would not like to publish that. what team would like to?

[puttenham]

McLaren wrote: It has been established that, owing to a process fault during manufacture, the outer clamp surface of the wheel was given a clear lacquer coating. As a consequence of this fault, the clamp load that attached the wheel was not to specification.

In running, the consequent loss of load caused the wheel to fret and distort, leading to its eventual failure.

Ok, who can interpret what this means? I think McLaren is probably accurate but
they talking in "race enginner" mode rather than "race fan mode".

I think what they are saying is the outer wheel surface, at the point where the tire bead contacts the wheel, had a very low coefficient of friction due to the surface treatment. Consequently, the tire bead did not have sufficient or constant grip with the mating wheel surface.

As the tire worked during the race, alternating the sidewalls between tension and compression in the turns, the tire bead had both alternating and relative motion between the tire bead and the rim. The relative motion reduced the ability of the tire bead to hold pressure with the wheel and created excessive localized heating. The relative motion and localized heat distorted the wheel further, reducing the ability of the tire to hold pressure. Eventually the wheel was unable to hold its shape and unable to hold pressure properly.

Comments?

At what tire pressures and temperatures do F1 tires typically operate?

I wonder how many other wheels had this defect but may have survived.

Thanks to Ron Dennis for acting on his verbal commitment to let the fans know the reason for the failure.

puttenham

[mx_tifoso]

Welcome to F1T,

As you may not know, there is a current discussion in the linked thread underneath for this topic, although the labeled thread topic does not give a hint as to whether it is discussing the McLaren wheel failure at the Spanish GP, but the thread discussion is mainly about such incident nonetheless. Feel free to direct your participation and to add your comments in that thread.

F1Technical- Driver safety and component failures

[zac510]

Clamp load sounds like wheel:hub interface to me.

[Ciro Pabón]

Puttenham: welcome by all means.

Following mxTifosi recommendation, I merged the topic you started with the one where the wheel failure was being discussed.

A typical tyre pressure in F1 is approximately 1.1 bars, whereas a normal road-going tyre pressure is in the region of 2.2 bars.

During races the tyre temperatures rise to some 100°C, and sometimes up to 120°C. If you put a drop of water in the tyre, it will boil.

I agree with Zac: I also believe that the clamp is the part of the wheel that is opposite to the wheel nut, that is, the surface of the rim which faces the wheel nut. If there is paint or lacquer on top of it, the paint or lacquer will desintegrate and the small void space left behind by the lacquer will be "used" by the wheel to move. Thus, the wheel vibrates, making the nut looser, until the tyre moves laterally, enough for the rim to make contact with part of the wheel that is fixed to the chassis and bang!

I also believe that the previous failure of a McLaren wheel was caused by a defective wheel nut gun, so, even if both failures seem to be the same, I think they had different causes.

Finally, this curious comment by Martin Whitmarsh, just a couple of months ago, which, if you do not take in account the previous paragraph, can be used to "crucify him" (but if you do take that in account, then it cannot):

Sunday, March 30, 2008

McLaren CEO Martin Whitmarsh is confident that the team have done all they can to prevent a repeat of the wheel-gun failure that cost Lewis Hamilton a podium finish in Malaysia.

A wheel-nut locking system problem scuppered Lewis Hamilton's chances of a podium at Sepang last week with the incident delaying the Briton by ten seconds and demoting him to eleventh behind a slower but resilient Mark Webber – he eventually wound up fifth.

McLaren, who fly out to Bahrain for the third race of the 2008 season this week have spent the last week ensuring that the problem does not reoccur for either driver.

http://www.crash.net/motorsport/f1/news ... oblem.html

[WhiteBlue]

Clamp load sounds like wheel:hub interface to me.

I still think that clamp in that context means wheel nut. Not knowing how the wheel nut works on a McLaren one can only speculate that the coating had different friction coefficient or different hardness compared to the surface that previously was used. It would explain why the wheel nut came loose. I would think that the wheel nut would have a locking mechanism and so friction isn't the most likely aspect to have caused this problem. If the wheel has different (lower) surface hardness and different elasticity the pre tensioning torque would not be held and the wheel could work loose. These changes to the wheels could be connected to the wheel fairings they are all developing.

[Ciro Pabón]

Well, I think you do not need to introduce different friction factors.

Lacquer (or paint) is about 4 mils thick.

A bolt works by stretching. Steel fails (that is, it breaks) by stretching just 0.7%, so, if the loaded part of the bolt measures, I don't know, one inch, it stretches just 7 mils before failure. Actually, you don't tighten the lug nuts that much, so, the whole amount of torque depends on a movement of a few mils.

If paint cracks and the bolt is "relaxed" just 4 mils, you lose most of the torque.

Btw, if you paint your wheels or change them for new ones, remember to retorque them after a few hundred miles or kilometers. Remember Kovalainen... Besides, don't tighten the lug nuts all the way: you did that before aluminum wheels and disc brakes. If you tighten the lug nuts too much you can warp the rotor or the wheel. Many cars have a decal that states the torque for the wheel nuts, check for it.

[DaveKillens]

As a side note, here's an old video of a similar accident. It was Burti at Spa, 2001. Due to Irvine and Burti coming together, Burti speared into a tire wall.
http://youtube.com/watch?v=iFMihMJaHrM

There are vast differences in the tire wall types, 2001 to now.

[WhiteBlue]

that was before they bolted them together and put the thick conveyor belt in front. still the TecPros are so much more effective.

back to the main programm: yes, it could have been the paint. if there isn't another rim failure I'm prepared to believe that they found it this time.

[guy_smiley]

that was before they bolted them together and put the thick conveyor belt in front. still the TecPros are so much more effective.

Someone disagrees with you...

Q: (Dominic Fugere – Le Journal de Montreal) To go back to the safety barrier, would you guys feel happier if you had a safety barrier which didn’t have bits and pieces flying off; that there was just foam behind a steel wall as is being used in America?

Jenson Button: I think the angles at which we hit the wall are far greater than what they do in America, on the ovals. I think if any of us had hit a safer barrier, it wouldn’t have been that safe, the speed and the angle at which we would have hit it. What do you think, Heikki?

Heikki Kovalainen: Yeah, I agree with that answer exactly. I think we probably should look more individually at the most dangerous corners. We can see ourselves which are the most critical places and probably make decisions accordingly and it’s not that straightforward, just adding some kind of wall here and everywhere. It’s not that simple. For myself, at Turn Nine in Barcelona, it worked very well this time and we’ve just got to see if we can do anything better and look at other corners as well.

What do they know, they're F1 drivers, they don't have brains

[Miguel]

I've just got a question, fellow posters.

If one looks at the Burti accident, you will se that, at one point, Irvine and another marshal move a cluster of bolted tires. These are packed in a "simple square" pattern. This arrangement is apparently still in use in every tire barrier in the F1 calendar.

If you want to put lots of circles in a defined area, a square arrangment is anything but effective. Do you think that a compact arrangement of tires would be more effective? I'm thinking in hexagonal layers (as seen in the fcc crystal structure), but I feel I'm not correctly explaining myself.