Driver safety and component failures

[Miguel]

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?

I don't think they disagree with whiteblue, or at least not in this topic. Mr. Fugere is explicitly asking about the SAFER barrier and Jenson Button makes an excellent point: impact angles in F1 are much bigger than in oval racing. In ovals, the perfect barrier should be able to absorb all outward speed while slowly bleeding off forward speed and all that without putting the car back into the middle of the track. That's what the safer barrier was designed to do.

The Tecpro barrier that Whiteblue referenced is also a pretty new device, having debuted, IIRC,in the 2006 Italian GP. They are also present in Paul Ricard HTTT and, ironically, at the new chicane in Barcelona (the one that mutilated the New Holland corner). There is a link to a promotional pdf and a few other goodies in the 10th page of the Spanish GP thread.

[WhiteBlue]

absolutely correct. SAFER and TecPro are two completely different animals. it looks like tecpro is the safest they have done so far. rotationally molded cm thick polymer skin to deflect flat angle impacts, foam filled interior with 4 mm steel sheet inside against fast penetration and fiber belts to connect elements.

[Saribro]

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.

A denser packing may not be effective. The tires would have less area to flex while absorbing the impact energy, essentially making the wall harder.
The stacking method seems like a first thing they would have analysed, so I'm assuming the square packing is the one deemed most optimal to the situation.

[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?

McLaren's explanation to the wheel rim failure of the Nürburgring

I thought I bring this thread back to our memory because the communication about the similar wheel rim failures of Hamilton and Kovalainen are discussed in detail here.

The conclusion at the time by McLaren was human failure to apply a certain surface finish lacquer correctly. This supposedly caused the wheel nut to go loose and led to the rim failure.

I have been uneasy with this explanation for some time. It almost looks to me that McLaren wheels are not machined from one piece of alloy. I am guessing here but I think perhaps they shrink the rim on the wheel to save weight and this design is inferior to a solid wheel design in terms of structural integrity. The other explanation might be that they do it in one piece but debris gets into the system and grinds the outer rim away from the wheel so that the tyre comes off.



Here in the Kovalainen accident you see a circular broken ring fly away in the initial phase of the accident. We saw pretty much the same on Sunday in Spain again.



This is the Hamilton accident in it's initial phase. You see again the ring fly away but you can also see sparks flying from the wheel inside at the nine o clock position.

We could clearly see a ring shaped object had broken and flew away. A wheel completely machined from one solid piece of metal alloy or thicker to avoid grinding away would have more unsprung mass but would be very much safer.

I want the FiA to take action in this case because it has happened at least three times now and the next time a car goes out of control at 300 kpm it could crash into another car and cause much more damage. This could also cause wheels to bounce across tracks and cause Surtees type accidents.

[autogyro]

Nice post WB.
It points to a problem with the design of the wheel nuts and fitting also.
Why does the safety latch engage if the nut is not fully tight?
It might even give a clue to the RB6 front brake problem.
If the front wheel on the RB6 becomes loose in the same manner then the rocking motion will be in the vertical (not horizontal). On the RB6 this could mean contact of the rim with the bottom mounted calliper. This would not happen with a conventionaly mounted calliper like the McLaren, so instead the rim gets machined.

[WhiteBlue]

So autogyro, you are saying that all these problems could be related to wheel nuts coming loose. Unless I'm mistaken we had at least four cases then in five races. Vettel had two of the brake failures, Schumacher had a loose wheel nut and now Hamilton has a loose wheel nut.

On top we had several cases of wheel nut problems slowing down stops because the nuts had nor properly engaged or did not come loose.

We do know that all teams did look into much more progressive thread designs to make the wheel change quicker. That leads to the conclusion that we have a safety relevant component here that became a performance differentiator. I'm questioning if that makes sense! Should the FiA look into providing a spec design which is the same for all and has a much increased safety margin? They could specify the thickness of the wheel rim, the type of thread and the locking mechanism of the safety pin to force a more reliable locking mechanism.

What would it matter if wheel changes would take six or seven seconds instead of four if it is the same for all? The FiA has the duty to watch the safety of the competition. I'm a bit uneasy that teams are competing to deliver a design that works fastest but compromises safety here.

[xpensive]

If I'm not very much mistaken WB, we had a thread a year ago on the ridicilous optimization of wheel-nuts. Invested-cast titanium with machined trapetzoidal double-threads for speed of mounting. At a cost of a thousand EUR a pop, outrageous!

[WhiteBlue]

If I'm not very much mistaken WB, we had a thread a year ago on the ridicilous optimization of wheel-nuts. Invested-cast titanium with machined trapetzoidal double-threads for speed of mounting. At a cost of a thousand EUR a pop, outrageous!

I'm not so much concerned with the cost but with the driver safety. The cost was only a side effect where the FiA was showing teams how they could save cost without affecting the show.

This issue in my view ranks with flexible rear wings breaking off and tyres failing due to wrong dynamic load calculations. It is simply unacceptable when safety components systematically fail because their safety margins are reduced to gain competitive advantages. If such things are discovered the F1 Commission must act on safety grounds. Individual teams will never tell you that their design is unsafe. But if two or three teams who run at the front are all caught out something should be done.

[autogyro]

Well I think there is a good chance we caught them WB.
What opinion do others have?

[timbo]

Do you think Hamilton would last to 64th lap (when did he had his pit-stop? AFAIK not later than 20th lap) with loose wheelnut? In Kovalainen's case crash came within a couple of laps after he pitted.

I agree that FIA should made an inquiry over wheelnut/rim design @ McLaren.

[WhiteBlue]

Do you think Hamilton would last to 64th lap (when did he had his pit-stop? AFAIK not later than 20th lap) with loose wheelnut? In Kovalainen's case crash came within a couple of laps after he pitted.

The rim failure is being investigated. It could be debris-related, it could be that a lack of tightness of the wheelnut allowed some flexing.

He says lack of tightness. But how did that occur? I have a hunch here that the seating of the wheel nut deteriorated over the long stint. The thin aluminum alloy of the wheel body may have seen some plastic deformation (settled) under the forces. The nut lock relies on the wheel material supplying a certain compression force. If the material creeps under load the nut can come loose. Of course the cure would be having thicker wheel bodies which defeats the objective of lowest unsprung mass.

[xpensive]

If I'm not very much mistaken WB, we had a thread a year ago on the ridicilous optimization of wheel-nuts. Investment-cast titanium with machined trapetzoidal double-threads for speed of mounting. At a cost of a thousand EUR a pop, outrageous!

The thing is, these kind of steep threads will never ever give you the self locking effect of an old fahioned M- or UNF/UNC-thread.

[autogyro]

I had a similar problem some years ago with an aircraft propellor.
That had a one nut fixing to the engine crank and a split pin for locking.
It was fine under power but on idle the vibration loosened the fit but without altering the split pin and washer position.
I think this problem has to be because the wheel nuts are to small and there is not enough load area on the wheel and or the materials 'move' to much.

[autogyro]

If I'm not very much mistaken WB, we had a thread a year ago on the ridicilous optimization of wheel-nuts. Investment-cast titanium with machined trapetzoidal double-threads for speed of mounting. At a cost of a thousand EUR a pop, outrageous!

The thing is, these kind of steep threads will never ever give you the self locking effect of an old fahioned M- or UNF/UNC-thread.

Very good point.
Bring back BSF and Whitworth, I knew where I was with them.
Mind you it is a bit basic for F1 engineers to miss is it not?

[WhiteBlue]

AMuS report the same as we already concluded. Loose wheel nuts due to extreme nut and rim designs are causing the problems.

Report - wheel nuts to blame for Vettel, Hamilton failures
Racing series F1
Date 2010-05-13
By Motorsport.com/GMM


Extreme wheel nut and hub designs in 2010 are contributing to failures, according to Germany's Auto Motor und Sport.

The specialist magazine said technical solutions to speed up pistops this year are related to the most recent failures seen on the Red Bull and McLaren cars last week in Barcelona.

McLaren boss Martin Whitmarsh confirmed this week that a wheel rim failure due to "human error" caused Lewis Hamilton's deflation and crash on the penultimate lap.

Auto Motor und Sport claims that a mechanic had pulled his gun off the wheel too soon during the pitstop, with Whitmarsh now confirming that the nut subsequently "loosened slightly".

"The magnesium part heated up and eventually broke," added the Briton.

Meanwhile, Red Bull's Vettel finished the race at the Circuit de Catalunya third, but without touching the brakes in the last dozen laps.

Auto Motor und Sport said the left front brake disc was longitudinally broken, with the team reportedly believing vibrations caused the failure.

The magazine speculated that, as was also the cause of his Melbourne problem - and Michael Schumacher's retirement in Malaysia - a wheel nut not fitted tightly enough at the pitstop was at the heart of Vettel's failure.

Here we see how thin the wheel rims actually are. Kamui Kobayashi's damaged rear wheel after a shunt in FP1 today.
Even if the wheel nuts are perfectly tightened they can come loose if the seat is compromised. The thread and the rim seat should be spec designs with focus on safety and not on performance. It is irrelevant if a stop takes 4 or 7 seconds if it is the same for all.

How long will it take to sort this out?