McLaren Wheel Nuts

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myurr
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Joined: 20 Mar 2008, 21:58

Re: McLaren Wheel Nuts

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Trocola wrote:
myurr wrote:If that's the case, the problem should be in all pit stops, not just the last two races. I think it is more a human error than anything else.

Other idea: maybe the wheel nuts are new for this two races and haven't been tested properly in race conditions...


Trocola
Not if it only increases the probability of a fault, it doesn't have to be a 100% chance of failure to see two failures in four races and however many pit stops. So it could be a combination of a whole load of factors - temperature, angle of entry into the pit box, mileage on the parts, human error, etc.

marcush.
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Joined: 09 Mar 2004, 16:55

Re: McLaren Wheel Nuts

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Ferrari has stated in public that "hot" stops are slower by half a second due to inconsistencies in the race and mental pressure on the crew...so the pitstop process is more or less a random happening and you are flirting with disaster every time you bring in your guy.

Or to put things straight:you can optimise as long as you want ,a hot wheelchange stop is not a safe proceedure with the current technology in use.End of story.

I see a case for FIA to react and install a rule for the teams to provide a process description that takes all the risks involved into account and shows the possible results of process steps not completed ,e.g mishaps. and action to be taken to prevent further damage= unsafe release of the car.

Button did not finish the race last week ..he had some rearend defect after a tyre problem ....any comment from Mclaren side about the reasons or the underlying problems that led to the dnf?

GrizzleBoy
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Joined: 05 Mar 2012, 04:06

Re: McLaren Wheel Nuts

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marcush. wrote:Ferrari has stated in public that "hot" stops are slower by half a second due to inconsistencies in the race and mental pressure on the crew...so the pitstop process is more or less a random happening and you are flirting with disaster every time you bring in your guy.

Or to put things straight:you can optimise as long as you want ,a hot wheelchange stop is not a safe proceedure with the current technology in use.End of story.

I see a case for FIA to react and install a rule for the teams to provide a process description that takes all the risks involved into account and shows the possible results of process steps not completed ,e.g mishaps. and action to be taken to prevent further damage= unsafe release of the car.

Button did not finish the race last week ..he had some rearend defect after a tyre problem ....any comment from Mclaren side about the reasons or the underlying problems that led to the dnf?
Overly damaging their rear tyres, loss of pressure in his rear left. Stopped for a new tyre. Smoke is seen coming from the central cooling exhaust in front of the beam wing.

Cracked exhaust making the car sound like that annoying ford fiesta that sounds like it's going 100mph, but you look out the window and it's going about 20.

Kind of weird about the loss of pressure in the tyre. Wasn't a "blown" tyre like Maldonados. The air just "came out".

Wonder where the damage would have been? The tyre tread? Failure of the wall?

Wheel nut working its way loose, Jenson feeling his wheel coming off and shooting into the pits. Avoiding a fine from the FIA by calling it a puncture?

marcush.
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Joined: 09 Mar 2004, 16:55

Re: McLaren Wheel Nuts

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The tyre was almost flat when he entered the pits... but had enough life in it to make the last corner at racing speed...very suspicious..

we will never know but it could be their rear hub system is simply running on the very hot side due to some unexpected material combo mismatch.

Temperature wise you ´d expect no increase after a few laps ,so the system should run at stable temps -reducing loads should ease the life a bit towards the end of the race ..

A hot wheelchange will likely see a hot hub offered a already cooled down wheelnut ...in case of the Mercedes wheel integrated wheelnut the delta might be as high as 100degrees....you wil need to think about tolerances ...and expansion rates,don´t you think?

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PlatinumZealot
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Joined: 12 Jun 2008, 03:45

Re: McLaren Wheel Nuts

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richard_leeds wrote:Try to keep this technical please, conspiracy theories are a waste of forum space
You know - Conspiracy was the first thing that came to mind after that first stop in Bahrain! :lol:
But then Buttons car went to crap and I dropped the conspiracy accusations in regards to the wheel nut at least.
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PlatinumZealot
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Joined: 12 Jun 2008, 03:45

Re: McLaren Wheel Nuts

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marcush. wrote:The tyre was almost flat when he entered the pits... but had enough life in it to make the last corner at racing speed...very suspicious..

we will never know but it could be their rear hub system is simply running on the very hot side due to some unexpected material combo mismatch.

Temperature wise you ´d expect no increase after a few laps ,so the system should run at stable temps -reducing loads should ease the life a bit towards the end of the race ..

A hot wheelchange will likely see a hot hub offered a already cooled down wheelnut ...in case of the Mercedes wheel integrated wheelnut the delta might be as high as 100degrees....you wil need to think about tolerances ...and expansion rates,don´t you think?
I disagree about temperature mismatch. Not with Material so thick, threads so large, and on that part of the vehicle. That nut will never get as hot as 100*C just being on the wheel, and that temperature is nothing.

It is a mechanical mishap. Cross threads or plugging. McLaren needs to make a design to greatly minimise problems that can happen when fastening the wheels.

My suggestion to them, is to copy what Ferrari has.
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marcush.
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Joined: 09 Mar 2004, 16:55

Re: McLaren Wheel Nuts

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never say never...what makes you so sure the wheelnut is never at 100°C? the wheel comes off the blankets at 80°C ...the running temperature of the hub is definetely around 100°C + the brakes are 500°C + the brake fluid is definetely in the 200°C range as are the Calipers..
Thermodynamics will always allow the hot parts heat up the colder ones as soon as there is physical contact and of course radiation...

ferrari are admitting they have a HIGH RISK system ,so just copying what you see is a safe way to run into more trouble?

xpensive
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Joined: 22 Nov 2008, 18:06
Location: Somewhere in Scandinavia

Re: McLaren Wheel Nuts

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The components adjacent to the brakes can surely be far more than 100 C and titanium has a low thermal xpansion coefficient vs aluminium or steel, 8.6 vs 23 or 11, but I have no idea about the tolerances of that step trapezoidal thread?

Neither am I certain xactly which material are involved here?
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jamsbong
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Joined: 13 May 2007, 05:00

Re: McLaren Wheel Nuts

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Aluminium is a weak material. It gets sheared easily. I'm not surprised by the lack of reliability.
I wondered if the guy who did the right-rear nut is always the same guy? Perhaps his action is slightly different from others and may cause cross-threading. Otherwise, The right-rear titanium rod might have defect?

Weighing the time lost when a nut is not working, you'll loose about 5-10seconds per pitstop. Versus if you use reliable steel over 20laps? I wonder which one is better?

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PlatinumZealot
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Re: McLaren Wheel Nuts

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marcush. wrote:never say never...what makes you so sure the wheelnut is never at 100°C? the wheel comes off the blankets at 80°C ...the running temperature of the hub is definetely around 100°C + the brakes are 500°C + the brake fluid is definetely in the 200°C range as are the Calipers..
Thermodynamics will always allow the hot parts heat up the colder ones as soon as there is physical contact and of course radiation...

ferrari are admitting they have a HIGH RISK system ,so just copying what you see is a safe way to run into more trouble?

The brakes are floating disks. There is a metal hat that holds the disks. Then you have the wheel which is a huge heat sink,then finally you have the nut.

First you have to quantify all the factors like conduction, radiation, and most importantly convection. The wheel nut is cooled by convection while the car is moving. I have not quantified it myself but I am assuming that the tyres are hotter than the wheel and the wheel nut. And I know the tyres normally work at around 100*C.

The brake fluid is definitely hot and understandably so.
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QLDriver
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Joined: 24 Jul 2011, 00:02
Location: Orange County, CA, USA

Re: McLaren Wheel Nuts

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jamsbong wrote:Aluminium is a weak material. It gets sheared easily. I'm not surprised by the lack of reliability.
I'd guess most of the teams use a softer material for the nuts than for the studs. If you did them in the same material, then if they get cross threaded, you're likely to damage the stud as well as the nut, and if you do that, your race is DONE.

xpensive
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Joined: 22 Nov 2008, 18:06
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Re: McLaren Wheel Nuts

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QLDriver wrote:
jamsbong wrote:Aluminium is a weak material. It gets sheared easily. I'm not surprised by the lack of reliability.
I'd guess most of the teams use a softer material for the nuts than for the studs. If you did them in the same material, then if they get cross threaded, you're likely to damage the stud as well as the nut, and if you do that, your race is DONE.
Aluminium is definitely not a "weak material", with the 7000 series you can get a yield strength of more than 400 MPa,
if the nuts are aluminium that is. Also, I consider cross-threading that steep trapezoidal thread highly unlikely.

Image anyone?

I think the problem here is more likely down to galling or some funny temperature phenomena.
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marcush.
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Joined: 09 Mar 2004, 16:55

Re: McLaren Wheel Nuts

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-convection- free or forced ?
You are releasing a huge amount of energy when doing a hot pitstop -but your claim the brakes are relying on forced convection is simply not valid when the car is stationary.I would estimate the worst case scenario is the pit stop which is not working as planned ...eg the standstill is taking longer than planned and temperatures sore ...

and :Material mismatch is sometimes very surprising...but Ti is known for this .so you don´t even try without coating ,the coating will help the surface but local stress may still move the material beneath globally and expose uncoated base or dig into the other component.

As a sideline wheelnuts look just awful after a few mounting dismaounting actions ,and all teams use big gobs of monting compounds -with solid particles- to provide a non galling protection- It all is a bit fishy ,at least for me-

tok-tokkie
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Joined: 08 Jun 2009, 16:21
Location: Cape Town

Re: McLaren Wheel Nuts

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Kravitz on the Sky after race summary discussed this:
1. The first Hamilton pit stop the drive lugs on the wheel were not properly engaged so it had to be loosened so they could be properly engaged.
2. Hub is titanium. Nut is aluminium. Most other teams have steel hubs - I don't remember what the nuts are.
3. Second pit stop there was a problem with the nut. Crossthreaded?
4. Wheel gun man then asked to be replaced for the final pit stop. He was replaced.

I think the link to the YouTube of this report is in the ravce thread.
From an earlier picture of the hub I don't think it is a trapezoidal thread. Regular triangular thread I think.

EDIT: Video is on page 48 of the race thread. Posted by Raymonu999 on Sunday. Vid does not say anything about steel hubs on other cars - I must have read that elsewhere.

xpensive
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Joined: 22 Nov 2008, 18:06
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Re: McLaren Wheel Nuts

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tok-tokkie wrote:Kravitz on the Sky after race summary discussed this:
...
2. Hub is titanium. Nut is aluminium. Most other teams have steel hubs - I don't remember what the nuts are.
...
Alu against Ti, that's a new one, I would have called for surface coating and a lubricant to avoid galling?

Thermal xpansion of Alu is however three times Ti, why that should not be a problem.
tok-tokkie wrote: ...
3. Second pit stop there was a problem with the nut. Crossthreaded?
...
I think the link to the YouTube of this report is in the ravce thread.
From an earlier picture of the hub I don't think it is a trapezoidal thread. Regular triangular thread I think.
...
I seem to remember images of a very steep, perhaps even double entry, thread which at least looked trapezoidal?

I cannot see how you could possibly cross-thread such a thread?
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