DrJupeman

I see that Heigo sells both Aluminum and Steel rollbars. Obviously I want to add as little weight as possible to my car. Further I know that by weight aluminum is stronger than steel. So the question, are the aluminum rollbars strong enough to be effective? Are they legal in racing (not that I'm a racer, but adhering to safety standards in general seems like a good idea). Anyone know what the weight difference is between the aluminum and steel bars?

Jeff Curtis

I don't know the weight difference between a steel and an aluminum Heigo rollbar, but I can tell you that the steel version would be the only legal choice for PCA Club Racing.

The weight difference wouldn't be noticeable for acceleration/handling purposes, maybe 15lbs?? ...just a guess.

BrokeAss

Ask yourself this, if you roll your car which one do you want saving your life?

I bought the steel Heigo bar for my Cabriolet.

DrJupeman

I would want aluminum if it weighs the same as steel (and even some portion less than steel). Without knowing the weight, I guess none of us can accurately answer the question.

Maybe a ME can chime in, as I don't pretend to know any of the critical load characteristics of either metal. We don't know what kind of steel or aluminum is used, etc...

My understanding in layman's terms is that built to the same standards, AL will be 35-45% lighter than steel. Therefore build the aluminum to the same weight and it will be considerably stronger.

I have a friend with some nice advanced software that could predict failure of these designs with either metal. If/when I can find more details on the Heigo bar I'll see if we can model them up and post results.

BrokeAss

I'm no mechanical engineer Dr. J, but you've got me baffled here

If I understand your post correctly, then if I have two pieces of metal tubing - each one pound weight, you believe they would offer the same resistance to bending, fracturing, etc regardless of the metal used? ...and hence when used in the construction of a rollbar offer equivilant levels of protection.

I don't buy that. I write software for living and admittedly know "squat" about metallurgy, but I've got to believe that pound for pound, steel is stronger than aluminum and when used in the construction of a roll cage, offer more protection. Aluminum is a much softer metal than steel and I think offers the driver less protection.

Anyway - let's just hope that neither of us finds ourselves in a situation where we NEED our rollbars to save our hides!

DrJupeman

Pound for poind aluminum is stronger. That said, the two metals have different characteristics.

Utilizing an identical design, aluminum has a smaller "deflection range" than steel, which means it would bend less before failing. Say nothing more and we would both agree that steel would be the choice for a rollbar application. But if you design the bar with the properties of aluminum in mind, you could make a stronger and lighter bar than steel.

A lot of this disussion depends on what kind of aluminum alloy is used vs. what kind of steel is used, but my understanding (from doing a little reading - always dangerous!) is that you should be able to design an aluminum structure that is basically as strong as steel but weighs 1/3 as much. In the case of a rollbar that might only be 15-20 lbs, but I'd pay $100 more to save those lbs (hell, I search high and low for easy weight savings elsewhere). I'm assuming Heigo would have had to increase the thickness of the aluminum pipes in their design to ensure it has similar strength to the steel bar. I don't know if they did that. I will try to find out.

Some good quotes from an article I read (I'm quoting some guy named Dave Gerr):

"for columns that are designed to an equivalent stiffness an aluminum column will weigh 57% of the equivalent column in steel._ For beams and panels (frames and plating) designed to the same stiffness, an aluminum structure will weigh 48% of the equivalent structure in steel."

Irishdriver

You can't get FIA approval for an aluminum roll cage for many years.

They are really only for fast road cars where the owner wants a bit more security or to look serious.

I can't really undertsand why anyone would opt for "half-safety" when the steel equivalents are probably cheaper.

speedster 94

hallo
There was a accident at the Ring ,years ago , the Driver was killed by the Alu Cage because it broke and speared him . I have been told that Steel would bend insted of break ,that is the reason why the PCA and FIA rules
forbid Alu.
harald

CarreraCup03

Were the original Matter cages in the carrera cup cars alluminum or steel. If they are allum .... there are quite a few guys who run them in PCA Club racing .. thus they must be legal. Maybe this is because they are factory cages. Anybody have any info on this.

944turbo

Jeff Curtis

Original Porsche Matter cages in the 964 Cupcars were STEEL.

I think there may be a difference in wall thickness in some of them??

...like .090 compared to .120 which is the required thickness for most racing organizations now.

Personally, while weight, or shall I say the lack of weight has it's benefits, I would NOT go with the aluminum bar. Think resale (of the bar), your safety and the fact that everyone else has STEEL.

Aluminum is brittle, it will break under much less deflection, as you mentioned...that alone would concern me. Also, you mention that pound for pound, Aluminum is stronger...who world manufacture a THICK aluminum rollbar that weighs the same as their identical design in STEEL??

They would ruin the whole point of making an aluminum rollbar if they did that - only because 99.9% of the market interest would be for weight savings, not because it is stronger.

Just my two cents.

martinreinhardt

I found this from the Porsche Motorsport site and it appears that the early (1990) cup car did have an aluminum roll bar.

I did see a 90's cup car flying across the gravel flipping in the air and land on the roof on top of the wall (between tire wall and spectators) in the Sachs Kurve (Hockenheim). The driver wasn't hurt, but the roll bar had a 90 degree angle in it.


GET A STEEL ROLL BAR !!!!


911 Carrera 2 Cup
----------------------

The first Cup Carrera appeared in 1989, built by Porsche Motorsport on the basis of the Carrera 2. This 911 Carrera 2 Cup had, for the 1990 racing season, a 3.6-liter air-cooled six-cylinder boxer with dual ignition, which produced 265 horsepower (195 kW) at 6,100 rpm. The highest rpm achieved was 6,800. With only 15 horsepower more than the standard model, the increase in performance proved very moderate. As with all Cup Carreras, the engine used normal commercially available fuels and contained regulated exhaust catalytic converters.

Power was transferred to the rear wheels via a five-speed transmission with abbreviated third, fourth, and fifth gears, and a limited-slip differential.

The modified chassis kinematics, more rigid and shorter springs, and adjustable anti-sway bars guaranteed racing-class precision. The Cup Carrera was also 2.2 inches lower than its standard series equivalent.

Steering was translated more directly and managed without servo assistance, as was the case for all its successors until the 911 Cup 3.8.

Large-proportioned, internally ventilated and perforated brake disks guaranteed typical Porsche braking performance, working in coordination with a standard ABS modified for racing.

An aluminum safety cage, replaced by a welded steel cage in 1992, protected the driver and worked together with a front dome strut to increase rigidity. Porsche published the weight of the first Cup Carrera at 2,464 pounds.

ltc

My 92 Euro Cup factory (Matter) cage is steel (unless I have discovered magnetic aluminum).

Although 0.090 is below PCA Club Racing minimums today, they are allowed/considered PCA legal since they are classified as factory installed items.
(this is from a previous thread from the DE forum I believe...can't find it now)

springer3

This is a confusing thread. Are we talking about the relataive merits of steel and aluminum alloys, or are we talking about commercially available roll cages constructed from lower grades of steel or aluminum? On merit, an exotic in either steel or aluminum alloy will outperform cheap grades of the other. Steel is a great material - strong, ductile, easy to fabricate, and, most importantly, CHEAP!. Since aluminum is inherently more expensive on a per pound or per unit strength basis, and strength to weight is not too different if we use a better steel alloy, it is no surprise that steel seems to be the material of choice.

tonytaylor

Steel

I have never met a racer who recomends an aluminium cage.

I agree with the point that if you want safety then go all the way and do it properly.

Mark in Baltimore

No question: steel.