Roll bar vs. cage

[BipDBo]

One thing that has bothered me from the start of this contest is the roll bar. Many race cars feature full cages for added security. I do not race, but would love to get into it. The cost of this kit may enable me to do so. If I ever do get into racing, I would greatly prefer the added security and potentially stiffness of a full cage rather than just a roll bar. The Factory 5 challenge car does not have a full cage but it does have tube steel running from each top corner of the roll bar diagonally down toward the frame. Xabier drew this "semi cage" design on his track version. The challenge car also has the benefit of its long hood with the heavy engine in front of the driver acting as a crumple zone. Since the 818 is mid engine, the need for protection of the cockpit is much greater. For the 818 in a frontal collision, the momentum of the engine, transmission and fuel tank will push through the cockpit, effectively turning the cockpit into the crumple zone. The way the 818 frame is currently designed, it seems to me that it would tend to fold like a jackknife right about at the driver's legs.

Here are some examples of some nice cages.
Lotus 7.jpg
Lotus 211.jpg

It seems to me that a cage would also be more adaptable and therefore lend itself better to the single frame, many bodies concept. The added stiffness provided with a cage may allow for the framing along the side to be opened up a bit for a larger, more user friendly door. A cage would also be very good for those who want to install a windshield. For a version with a roof, a cage could be designed with a "T-top" roof and gull-wing doors like the Ultima GTR. I like this design because it has fixed rather than roll-up windows, eliminating some weight and rain proofing issues.
Ultima GTR doors.jpg

The downside to a cage may be added weight, but it might actually decrease the total weight of the frame by eliminating some of the steel down low. After all, convertibles are typically heavier than their coupe counterparts because of the extra heft needed under the floorboards for rigidity.

I'd like to hear opinions, especially from active racers and automotive engineers.

[Niburu]

I'm pretty sure FFR has already taken all this into consideration.

[Texan_GTM]

Roll bar... Cage, is just.... no...

[16g-95gsx]

A true roll cage is absolutely necessary for safety....on a track car. You need to realize that FFR is also designing this car to be streetable. The issue with cages, such as a 10pt cage is that while they are safe when wearing a helmet, they KILL safety when not wearing one. You have bars running near your head, which only cause major safety concerns when not wearing proper track PPE. Anyone who intends to run these cars as dedicated track cars can easily adapt what they have to full cages, otherwise I would not even think about it. Dave and the FFR crew seem to be seasoned performance veterans who understand this and therefore would likely NOT do something like this.

[GUNS]

A true roll cage is absolutely necessary for safety....on a track car. You need to realize that FFR is also designing this car to be streetable. The issue with cages, such as a 10pt cage is that while they are safe when wearing a helmet, they KILL safety when not wearing one. You have bars running near your head, which only cause major safety concerns when not wearing proper track PPE. Anyone who intends to run these cars as dedicated track cars can easily adapt what they have to full cages, otherwise I would not even think about it. Dave and the FFR crew seem to be seasoned performance veterans who understand this and therefore would likely NOT do something like this.

well said

[Gollum]

Someone ask Dave about rolling a roadster.... :-D

[BipDBo]

A true roll cage is absolutely necessary for safety....on a track car. You need to realize that FFR is also designing this car to be streetable. The issue with cages, such as a 10pt cage is that while they are safe when wearing a helmet, they KILL safety when not wearing one. You have bars running near your head, which only cause major safety concerns when not wearing proper track PPE. Anyone who intends to run these cars as dedicated track cars can easily adapt what they have to full cages, otherwise I would not even think about it. Dave and the FFR crew seem to be seasoned performance veterans who understand this and therefore would likely NOT do something like this.

If a cage is neccessary for a track car, wouldn't it be a good idea for factory five to build their track version with the car already welded on? Compared to having each builder weld a custom cage, that would make for a more cheaper, higher quality, more consistant end product.

I disagree that a cage would make the car more dangerous when a helmet is not used. That only applies when the cage is too small and could therefore collide with the head. Dune buggys have a cage for good reason. The Factory Five hot rod, coupe and GTM each have a tube steel cage under a fiberglass roof. In fact, every car except an open roadster; Coupe, sedan, wagon, minivan, suv has a metal cage above a head liner that makes it safer for the occupants. Recent changes to crash testing rules have led manufacturers to build the roof and pillars much stronger than ever because of it's importance to safety.

[Niburu]

If a cage is neccessary for a track car, wouldn't it be a good idea for factory five to build their track version with the car already welded on? Compared to having each builder weld a custom cage, that would make for a more cheaper, higher quality, more consistant end product.

Who says they're not going to have a cage for the track version?
Nothing has been said either way by FFR.
No doubt the regular street version will be available first, I'm sure when it proves to be a sucess they can move on to the track version.
If they do a fixed roof vehicle (like the GTM) the cage starts to make more sense.

I disagree that a cage would make the car more dangerous when a helmet is not used. That only applies when the cage is too small and could therefore collide with the head. Dune buggys have a cage for good reason. The Factory Five hot rod, coupe and GTM each have a tube steel cage under a fiberglass roof.

a racing rollcage and one used on the street are very different, and for those of us over 6 feet tall both are dangerous without padding.

In fact, every car except an open roadster; Coupe, sedan, wagon, minivan, suv has a metal cage above a head liner that makes it safer for the occupants. Recent changes to crash testing rules have led manufacturers to build the roof and pillars much stronger than ever because of it's importance to safety.

your comparing a monocoque chassis to a space frame chassis with a body bolted to it
these vehicles are worlds apart

[riptide motorsport]

You want a cage, put one in. A caveman can do it.

[2KWIK4U]

You want a cage, put one in. A caveman can do it.

I think you hit the nail on the head, if you need a full cage for racing then install one but maybe FFR could put one on the track version but also the price starts to go up.

[jimgood]

You want a cage, put one in. A caveman can do it.

Right. A caveman with welding skills, tube bending equipment and a whole lot of other knowledge that most of us lack.

Or money to pay someone like you.

[BipDBo]

@Niburu:
"your comparing a monocoque chassis to a space frame chassis with a body bolted to it
these vehicles are worlds apart"
Not really. A unibody doesn't come from tube steel, but rather forged and welded from sheet metal. The end result, though is remarkably similar; a space frame, or "cage" with a sheet metal skin bolted and welded on.
unibody.jpg

If they are going to have a windshield for the base design, they will need to support it, probably with tube steel. There is a roll bar about 24" behind the top edge of the windshield. I say, connect the windshiedld to the roll bar for a stiffer, safer car.

@riptide motorsport:
"You want a cage, put one in. A caveman can do it."
I guess I was hoping for an entry level track car. They want to get a product that is as easy and cheap to assemble as possible. It isn't even going to require paint. A factory welded cage would greatly abbreviate the route to the track. Also, even I know enough about racing to know that each cage varies in weight and quality. A factory supplied cage would be consistent, lending itself well to a 818 one design race series.

[thebeerbaron]

I guess I was hoping for an entry level track car. They want to get a product that is as easy and cheap to assemble as possible. It isn't even going to require paint. A factory welded cage would greatly abbreviate the route to the track. Also, even I know enough about racing to know that each cage varies in weight and quality. A factory supplied cage would be consistent, lending itself well to a 818 one design race series.

It sounds like we need to define "track" before we go much further. Are you talking about wheel-to-wheel racing, or track days, HPDE, and the lower echelons of Time Trials? Wheel-to-wheel will require a cage. The others will not, generally speaking, and are a great way to get "entry level" experience on the track. Each sanctioning body has their own rules for the level of protection required, but for both NASA and SCCA open vehicles require a roll bar which spans the entire cockpit. Dual hoop, "cobra-style" roll bars are not acceptable. I'm very glad to see the initial chassis includes a proper roll bar, I hope it stays that way.

Summary: this thing should be a great "entry level track car" out of the box, without a cage.

[thebeerbaron]

On further reflection, I wonder if kit cars like the 818 are treated as "street" cars under these rules. If they are not, the above may not apply.

[BipDBo]

@thebeerbaron
"Dual hoop, "cobra-style" roll bars are not acceptable."

Like those shown on the winning design?

"Summary: this thing should be a great "entry level track car" out of the box, without a cage."

This is good to know. Time trial racing is probably all I'll ever have balls for. I would most likely not get into wheel to wheel, at least while I still have 3 kids at home. By the time they grow and leave the nest, I'll probably be too old, tired, and broke from paying for college. Carpe Diem!

[thebeerbaron]

Like those shown on the winning design?

Yes, and those on the S2000, the 2006+ MX-5/Miata, the Z4 'vert, etc etc.

Pretty does not mean safe.

[Cooluser23]

The big issue I have with a cage is that when driving while not wearing a helmet, the cage can be deadly if designed wrong.

[BipDBo]

@thebeerbaron
I'm curious, if that picture is of you driving what looks to be a Miata (excellent car), do you feel that your rollbar offers adequate protection? It looks to me that the top of your helmet is far above the top of the rollbar. How much would it protect you in the event of a rollover?

@Cooluser23:
"The big issue I have with a cage is that when driving while not wearing a helmet, the cage can be deadly if designed wrong."
I would think that this is all the more reason for it to be designed and built by Factory5 rather than by the builder. Is making it safe for use without a helmet just a matter of making it large enough so that your head cannot swing into it, or is there more? I would think that most of the problems come from installations within the body of an existing car, which would make the dimensions of the cage smaller. I know that the larger the cage, the safer, and that this is why NASCAR cars just recently grew in size.

[PhyrraM]

Cages = Harnesses. Simple as that. Three point seatbelts will not work. They will allow enough freedom of movement to eventually allow your head to contact a very hard steel tube.

I do not want a harness requirement (or cage, by association) on my street car. Oddly, I don't think I'd mind a helmet as much as a harness.

IMHO, competition and street kits need different frames. FFR has already recognized this as evidenced in the Roadster line. I don't see the 818 being any different.




Before the acusations start....I wear my seatbelt, I'm not one of those '70s throwbacks who feels safer if 'thrown from the car'.

[thebeerbaron]

Whenever I drop the race seats into the Miata, I have to use harnesses on the street. It is significantly less than ideal and only happens as I drive to/from the track. Sure, some of the blind-spot issues can be eliminated with proper mirror adjustment, but there are lots of little instances where not being able to move one shoulder really makes life difficult.

One of the features of 3-pt belts is the ability of the torso to have some motion during a crash. If the body is rigidly affixed in a 6-pt harness situation, the only thing that moves is your head, possibly resulting in basilar skull fracture. Not pretty. This is why I run head-and-neck protection on the track. No way am I doing that on the street though!

On the other side of the coin, an airbag is a great thing to have around to prevent your body from impacting the steering wheel as it pivots around the 3-pt belt...

So yeah, not sure what sort of restraint system I'd like in the 818. But a cage is an awfully hard thing to hit your head on...

[crackedcornish]

Whenever I drop the race seats into the Miata, I have to use harnesses on the street. It is significantly less than ideal and only happens as I drive to/from the track. Sure, some of the blind-spot issues can be eliminated with proper mirror adjustment, but there are lots of little instances where not being able to move one shoulder really makes life difficult.

One of the features of 3-pt belts is the ability of the torso to have some motion during a crash. If the body is rigidly affixed in a 6-pt harness situation, the only thing that moves is your head, possibly resulting in basilar skull fracture. Not pretty. This is why I run head-and-neck protection on the track. No way am I doing that on the street though!

On the other side of the coin, an airbag is a great thing to have around to prevent your body from impacting the steering wheel as it pivots around the 3-pt belt...

So yeah, not sure what sort of restraint system I'd like in the 818. But a cage is an awfully hard thing to hit your head on...

I run a 5 point harness set up on the street in my caged Jeep...you don't have to use all of the belts of the harness on the street if you don't want too, I have driven lots of times without the anti submarine belt and one of the shoulder belts connected (just for comfort) on a short trip

[Steve91T]

I run a 5 point harness set up on the street in my caged Jeep...you don't have to use all of the belts of the harness on the street if you don't want too, I have driven lots of times without the anti submarine belt and one of the shoulder belts connected (just for comfort) on a short trip

That's dangerous.

[crackedcornish]

That's dangerous.

so is taking a shower...but I do that almost every day

[PhyrraM]

so is taking a shower...but I do that almost every day

That made me recall a movie called "The Darwin Awards". It's main character was obsessed with folks who offed themselves to the point he wore a harness in the shower to keep from slipping. That scene is hilarious.

Thanks for the flashback.....

[Gollum]

My "toy" Z car has no dash, no interior other than seats, is pretty much stripped of EVERYTHING mechanical and electrical I don't need, including HVAC, and is probably the scariest thing I've ever driven. It's not scary fast, only around 220 wheel hp and weighs around 2300 pounds, but just the overall affect the car has on you is... ...interesting. Every time I have someone in my car that hasn't been in it before they usually say something about being in fear for their life... and then I remember what I felt the first time I drove it and I fall in love all over again.

I wouldn't have it any other way. Isn't the "danger" you feel part of the reason we all love to drive cars? I don't mean to say that we're masochistic and drive cars instead of slitting our wrists. I'm just saying that we all understand the dangers involved to a degree, and despite all the safety gear in the world you're still putting yourself at risk every time you go out on the streets. I'm all for saefty gear, and as soon as I put a cage in my Z I'll be running a harness all the time, even on the street. That being said, I like to LIVE which usually involves temping fate from time to time.

[FFRSpec72]

The Factory 5 challenge car does not have a full cage but it does have tube steel running from each top corner of the roll bar diagonally down toward the frame.

Not true, the Challenge car has a full cage as part of that cage there is a front loop (there is even a rear loop to protect the fuel cell), this cage meets SCCA, NASA and other wheel-to-wheel racing organization protection requirements (as mine has passed in NASA, SCCA and ICSCC). I also disagree that this is unsafe on the street when not wearing race apparel. My seat protects me from any direct contact with the cage (above and side to side) along with the SFI padding I have. I feel far safer in the challenge car on the street than I do a normal roadster. I have been t-boned @ 60+ mph so I know what a cage can do for you. Many tracks are now not allowing the roadsters (any type) to run on HPDE days w/o a full roll cage as insurance has been cracking down on the events.

I'm not a fan of add it yourself latter so I hope that a full cage will be in a track version much like what has been done for the challenge car or this car may have issues if you want to take it to HPDE events (if it turns out to be a true roadster) or want to run the car in wheel-to-wheel racing.

[Mike N]

FFR can and does do 'full cages'. Take a look at a coupe or GTM without the body installed. A 'full cage' no? So they know how to do it and do it in a way that it is not dangerous. They would have to consider where a full cage might structurally interface with the basic chassis and make allowances for a retrofit either as a factory option or an add on later, doesn't seem like it is difficult or out of the question.