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blown axles and wheel nuts


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#1 jimjimjeroo

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Posted 26 September 2015 - 11:11

Generally saying we don't see wheels flying off these day due to these tethers. After kvyatts accident today he lost 2 wheels. You could see the remains of his rear disk and axle on the floor behind him.

Could the blown axles compromise safety? After all if you put holes in something you're likely to make it weaker. ..

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#2 Chubby_Deuce

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Posted 26 September 2015 - 20:55

The uprights and suspension were also missing. You'd be onto something if the uprights and tethers survived sans wheels.



#3 jimjimjeroo

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Posted 26 September 2015 - 21:28

would be interesting to see the construction of the assembly, my understanding they attach to the pin stub hub assembly through the wish bones to the chassis.  and the wheel is attached onto the hub with the single bolt... which you see in pit stops... so for the wheel to detach the hub would have to fail, or the tether, going by what Brundle said is that after the initial impact the tethers can fail...


Edited by jimjimjeroo, 26 September 2015 - 21:31.


#4 Lee Nicolle

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Posted 27 September 2015 - 22:17

The way I understand it is that the upright is supposed to be retained. IF the wheel is done up [which they miss on occasion] the upright and wheel  and whatever suspension components attached should stay with the car. Clearly time after time it does not.

Sometimes you wonder about these cars, Massa,s accident he was hit by a spring. A coilover unit attached to the tub that should not get loose if attached properly. Often with undersize lightweight bolts. eg 3/8 ti bolts where I would use a 1/2" grade 8 steel bolt!

Like many categories ban all these fragile fasteners, they fail under stress and occasionally fail under service too.

Personally I feel these cars are built way too frgile for a accident, everything falls off!



#5 bigleagueslider

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Posted 28 September 2015 - 00:53

Here's the 2015 technical regs regarding tethers:

 

"10.3.6 In order to help prevent a wheel becoming separated in the event of all suspension members connecting it to the car failing, flexible tethers each with a cross sectional area greater than 110mm² must be fitted. The sole purpose of the tethers is to prevent a wheel becoming separated from the car, they should perform no other function. The tethers and their attachments must also be designed in order to help prevent a wheel making contact with the driver's head during an accident. Each wheel must be fitted with two tethers each of which comply with FIA standard 8864-2013 and each of which has a minimum energy absorption of 6kJ.

Each tether must have its own separate attachments at both ends which :
a) Are able to withstand a tensile force of 70kN in any direction within a cone of 45° (included angle) measured from the load line of the relevant suspension member.
b) On the survival cell or gearbox are separated by at least 100mm measured between the centres of the two attachment points.
c) On each wheel/upright assembly are separated by at least 90° radially with respect to the axis of the wheel and 100mm measured between the centres of the two attachment points.
d) Are able to accommodate tether end fittings with a minimum inside diameter of 15mm.
Furthermore, no suspension member may contain more than one tether. Each tether must exceed 450mm in length and must utilise end fittings which result in a tether bend radius greater than 7.5mm"



#6 Wuzak

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Posted 28 September 2015 - 05:31

The way I understand it is that the upright is supposed to be retained. IF the wheel is done up [which they miss on occasion] the upright and wheel  and whatever suspension components attached should stay with the car. Clearly time after time it does not.


You could do a comparison to see how many times the wheels come off and how many times the tethers work. IMO the latter will outweigh the former substantially.

When the wheels aren't done up correctly they will tend topart company with the car quite soon after leaving the pits, or the driver will detect a problem - such as Kimi in Australia.

 

Sometimes you wonder about these cars, Massa,s accident he was hit by a spring. A coilover unit attached to the tub that should not get loose if attached properly. Often with undersize lightweight bolts. eg 3/8 ti bolts where I would use a 1/2" grade 8 steel bolt!


The spring would have come off the third element spring/damper. Whether that was a bolt or some other failure, I do not know.

Things falling off cars is quite rare....unless you count front wings, or improperly secured bodywork.

 

Personally I feel these cars are built way too frgile for a accident, everything falls off!


Mostly what you see coming off is light weight bodywork.

 

Not sure if making it so nothing falls off is possible or desirable. 



#7 bigleagueslider

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Posted 30 September 2015 - 04:55

The regs are not written very well. The tethers are not attached to the wheels. They connect the upright to the chassis to limit movement of the flailing upright/wheel/tire in the event of failure of the suspension arms.



#8 Chubby_Deuce

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Posted 30 September 2015 - 05:51

Yeah, the upright is kind of the closest you can get to the actual wheel. That still leaves the axle, the bearing and wheel that can fail and send debris flying.

 

Anecdotally speaking it seems like the current tethers work pretty well. Wheels rarely leave the wreck with much pace, as even failed tethers will at least sacrifice themselves to dissipate some of the crash energy. Hopefully they update the regs as materials allow but it sure seems like they're already better than they were, say, 10 years ago when they only had one tether per wheel.



#9 bigleagueslider

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Posted 02 October 2015 - 02:30

Yeah, the upright is kind of the closest you can get to the actual wheel. That still leaves the axle, the bearing and wheel that can fail and send debris flying.

 

Anecdotally speaking it seems like the current tethers work pretty well. Wheels rarely leave the wreck with much pace, as even failed tethers will at least sacrifice themselves to dissipate some of the crash energy. Hopefully they update the regs as materials allow but it sure seems like they're already better than they were, say, 10 years ago when they only had one tether per wheel.

The intent of the tethers is to prevent the driver from being struck by the relatively heavy upright/wheel/tire/brake assembly. As for the danger posed by a wheel/tire coming loose, this has caused injury/death of spectators during some Indy Car speedway races.



#10 Chubby_Deuce

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Posted 02 October 2015 - 04:21

Yes...?



#11 bigleagueslider

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Posted 03 October 2015 - 02:52

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#12 Chubby_Deuce

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Posted 03 October 2015 - 03:29

Okay....