Consolidated 991RS thread
#1591
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Minor update fact: roof of the RS is definitely magnesium. Subcontracted out and being constructed currently. I got this from someone close to it who is credible to me.
#1594
Porsche uses magnesium for the roof of the Cabrio and Targa, I assume they have invested heavily in its production and thus decreases cost for them, making it more cost effective as a company. Also Magnesium not as brittle yet still very light, I think light as aluminum but still stronger more stiff without being brittle. There is currently a battle between Mg and Carbon wheels for motorcycles
#1595
Race, it's from my understanding from motorcycle wheels is that cf is much lighter (~50%) and stronger than magnesium. It's just that magnesium is more "flexible" hence more forgiving with potholes compared to cf. But in the case of a car's roof, I'd think that scenario is irrelevant and you'd want the lightest and strongest material, hence the use of cf. There's a reason why high performance cars use cf tubs and/or components and not moving towards magnesium. Maybe this is a cop out for Porsche to go after profit margins vice making the lightest possible RS.
#1596
Race, it's from my understanding from motorcycle wheels is that cf is much lighter (~50%) and stronger than magnesium. It's just that magnesium is more "flexible" hence more forgiving with potholes compared to cf. But in the case of a car's roof, I'd think that scenario is irrelevant and you'd want the lightest and strongest material, hence the use of cf. There's a reason why high performance cars use cf tubs and/or components and not moving towards magnesium. Maybe this is a cop out for Porsche to go after profit margins vice making the lightest possible RS.
#1597
Rennlist Member
Mg is typically alloyed with Au. Infact many alloy wheels have a small Mg component. I cant see any structural or weight benefits of a higher content Mg alloy for the roof over CF or alloy other than perhaps a benefit when producing the double bubble pressing and a margin weight benefit which may offset what I believe to be a higher roof line (for the bubble components) from what I have studied from the patent drawings which could be a measure to offset what would be a fractionally higher COG if in fact my observations are true. Of course there is also the marketing angle in using a "more exotic" manufacturing and material process. Infact too high Mg component will made for a more "brittle" and fracture prone end result so I guess they will be alloying with something clever to counter this....just my 0.2 on the subject.
#1598
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I suspect the choice was more engineering than cost driven given location as structural component of the tub/passenger cell (unlike bolt on hood and front fenders).
Magnesium is more expensive than aluminum but has well established advantages over the latter. See this comparison from bike building website: http://www.precisiontandems.com/cat_...amagnesium.htm)
The issues of connecting mg and steel - a factor in this location - also seem to have been solved. See: http://www1.eere.energy.gov/vehicles...eng_2011_o.pdf
Magnesium is more expensive than aluminum but has well established advantages over the latter. See this comparison from bike building website: http://www.precisiontandems.com/cat_...amagnesium.htm)
The issues of connecting mg and steel - a factor in this location - also seem to have been solved. See: http://www1.eere.energy.gov/vehicles...eng_2011_o.pdf
#1599
Is the seat belt mounting point not strong enough in case of a rollover? Reading through this thread make me think they are not. Has there been any instances were a car equipped with such roll cage rolled over and did not protect the cabin well? Is a plate mounted roll cage significantly better for a fact or just theoretical? I am debating whether to put a bolt on roll cage. I realize it providers anchor points for a harness.
Bottom line, if you are putting in harnesses then absolutely get one, but otherwise I'd probably skip it. Just extra weight and squeaks otherwise
#1600
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I tracked my RS for 3 seasons with just a harness bar. I'd seen first hand how well a 911 survived a nasty head-on and roll over without a roll bar. The fact that both driver and passenger walk away unscathed was quite comforting to me.
#1601
In all honesty I consider my "roll bar" to really just be a harness bar for this reason. It may provide some relief in a roll situation, but you can imagine the seat belt mounting points are probably pretty easy to shear. I'd say it has some benefit, but certainly nothing like a true welded-in cage. And it's certainly not providing much in the way of extra rigidity...
Bottom line, if you are putting in harnesses then absolutely get one, but otherwise I'd probably skip it. Just extra weight and squeaks otherwise
Bottom line, if you are putting in harnesses then absolutely get one, but otherwise I'd probably skip it. Just extra weight and squeaks otherwise
#1602
Wow, I just posted a similar scenario, just because I missed your post.
#1603
I suspect the choice was more engineering than cost driven given location as structural component of the tub/passenger cell (unlike bolt on hood and front fenders).
Magnesium is more expensive than aluminum but has well established advantages over the latter. See this comparison from bike building website: http://www.precisiontandems.com/cat_...amagnesium.htm)
The issues of connecting mg and steel - a factor in this location - also seem to have been solved. See: http://www1.eere.energy.gov/vehicles...eng_2011_o.pdf
Magnesium is more expensive than aluminum but has well established advantages over the latter. See this comparison from bike building website: http://www.precisiontandems.com/cat_...amagnesium.htm)
The issues of connecting mg and steel - a factor in this location - also seem to have been solved. See: http://www1.eere.energy.gov/vehicles...eng_2011_o.pdf
#1604
If you're going to track your car, and drive at your limit. You should set it up like a race car. Which means a roll bar. One guy walking away from a roll without a roll bar doesn't mean you'll be as lucky.
#1605
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at min., I put a rear roll bar in with hans