Arntz roll bar

[Cobra13]

I'd like to ask the opinion of Arntz/Butler owners on a roll bar scenario. Appreciate candid response! I'm thinking to change from the offset type roll bar Arntz used. I'm leaning toward a full width bar, but no flat in appearance, rather follow the curve of body deck below it. I would connect up the forward brace. Main reason is to protect my 13 year old Son, the other I guess is just to be a little different. Thoughts? Please. David

[jr289]

I would consider a 289 forward style bar, like on the fia.

[mickmate]

Some thoughts from me.
With the low center of gravity on these things you'd be hard pressed to roll it over, especially on the street.
I don't think you should have a rollbar unless you're wearing a helmet to protect yourself from it.
I don't let passengers wear shoulder harnesses if they don't have a rollbar as it holds you up in harms way.
It's your car and your kid, you can decide what's best for all of you.
It is a great family interest/hobby but nobody wants to be hurt by it.
I think when, where, and most importantly how you drive it are the considerations.

[750hp]

Originally Posted by mickmate

I don't let passengers wear shoulder harnesses if they don't have a rollbar as it holds you up in harms way.

Nick, that's an interesting idea. The main reason why I like the idea of a shoulder belt is that would hopefully make it harder for you to eat the steering wheel if things get ugly.

I guess this is only of benefit in a direct frontal impact.

[Cobra13]

Great points and ideas, thank you all. I guess the other consideration is authenticity of original roll bar...does it really matter? Thoughts? Thank you

[Donunder]

I tend to agree with Mick in that the chances of your being involved in a situation where a rollbar's safety properties are called into play are fairly remote. That said, if you are insistent on having one then you have to consider safety, appearance, and if it means a lot to you, originality.

1. Safety: An unbraced hoop or full width bar is a waste of time. Even more ridiculous are those bars that have one solid chassis mounting and the other mounted to the fibreglass body with a fancy surround and tiny bolts/rivets.

2. Appearance: One hoop, two hoops, full width, forward or rear bracing? One rear braced hoop looks fine. Sometimes two hoops can look a bit fussy especially if they're chromed. A full width bar looks the goods in my eyes but some may think it's overkill for a street driven car. For ultimate safety a full width bar of appropriate height, not some low-slung thing with two rear facing braces together with a triangular cross brace, is the answer. But David, I think you'd regret going for a curved bar over a flat one. Have you actually seen one? They're not nice...

3.Originality: My car has the original Arntz single hoop with a forward bracing bar going down into the passenger footwell. It was there when I bought the car and I like the look a lot. The fact that it's "factory" adds to its desirability, and as a bonus, that brace bar is a huge help when getting in and out of the car!!

Summing up? Anything that makes you happy as long as it's well made, is of effective height and is properly braced should be just fine ---as long as if you decide on a full width bar, it hasn't got a curved cross bar. Sorry.

[BAsque1]

Nick:
I agree with you wholeheartedly, my car has the full with roll bar and I love the look and naturally, its functionality. I guess that back when the Cobras were thoughout were only considering the driver, times have changed since. See my rool bar picture below.
Cheers
Lou

[joyridin']

So if you own any type of convertible..be it a Mustang or Miata, what happens in a rollover situation in one of those vehicles? Most do not have rollbars from what I see. Is the windshield support supposedly strong enough to support the weight of the car and stop anybody from getting partially crushed?

[Donunder]

It's a vexed question.

I drove an Austin Healey 3000 for many years without a roll bar -- never gave it a thought. We were able to drive with just lap belts back then, and even today I'd rather a lap belt than a lap/sash belt in an open car without a roll bar. It may be fanciful but I think that if the car were to roll, I'd like to be able to throw myself down and sideways into the centre of the car and not be pinned upright by the shoulder strap. Whether you'd have time to react, I don't know, and there'd doubtless be any number of experts who would argue against my point, but -- just my two cents...

With Cobras you have the choice of going from nothing to a full race type cage with bracing everywhere, but even then, without arm restraints your arm could flop out and be injured by the rolling car. So without building something grotesque, you have to accept that an open car carries an inherent risk of greater injury that a tin-top should things go pear shaped.
Some choose a full width bar with two rear braces and I think that's as far as you want to go. It's a bit like riding a motorcycle. You ride as carefully as you can, you become a little paranoid and treat other road users as dangers, you accept that what you're doing is dangerous to an extent -- but if all this becomes too much and you become fearful of riding, then you're better off just getting a car. Same with open sports cars -- accept their safety limitations, enjoy the good days, put up with the bad weather, but if it all becomes too much, go buy an SUV.

If you go hoop style with your roll bars you have to decide one or two. Wives and girlfriends rightly think they deserve a bar too so you see more twin setups than singles. Personally I like just the one. For safety/ club racing purposes the accepted dimensions are that the top of the bar must be at the upper end of an imaginary line drawn from the front of the body at its highest point above the radiator opening clearing the driver's head, then on to the top of the roll bar. This invariably means that, while the bar should then protect the driver in the event of a rollover (assuming of course that it is sturdily made, mounted and braced) it ends up being too high and looks odd or a case of overkill for normal road use. And then it should be padded!

The upshot of all this is that most guys sensibly avoid the cosmetic approach where a bar is not braced, or worse one leg of the hoop is mounted down onto the frame while the other is simply rivetted onto the fibreglass of the body. Total waste of time! Similarly any bar that does not rise higher than the driver's head not only looks faintly ridiculous but is next to worthless and is only adding unnecessary weight to the car for no discernible purpose.
So, a full width bar, made of suitably strong material, and braced, either two rearward facing with a diagonal, one forward facing, or both, is about as far as you want to go for normal road use. Two hoops, to keep your passenger happy are fine.

My Arntz is fitted with the original single hoop, with the unusual slightly stretched inner leg and forward facing brace down to the passenger's footwell. It's very strongly built, as seems to be the case with all aspects of the Arntz cars, and importantly the bar forms a frame well clear of the top of my head. Any roll bar where, from a following car, you cannot see daylight between the driver's head and the inside of the bar, is simply too low.

I have an old Mercedes Benz 500SL which has a recessed roll bar that would pop up in a fraction of a second should the computer decide that we're going over! The windscreen frame is also built to withstand the force of landing upside down. I don't know if Miatas are similarly constructed.

However, having said all that, if some kind soul offered me my great old Healey back to drive for the rest of my days, I'd happily do so. Similarly, if I ever build another Cobra, it would be a locally manufactured one, the Absolute Pace - Kit Car Manufacturer of Cobra & GT40 Replica's and other modern Sportscar kits (formally Race Car Replicas Australia) and it would be built in "road" style, without scoop, side pipes or roll bar.

If you want a roll bar, fit one that looks the part but is also going to go some way to saving your noggin if called upon to do so. Cosmetic add ons are clearly silly.

[Cobra13]

Thanks Don. With your great points and everyone else's, I'm going to stay with the original Arntz roll bar with forward brace. It seems to be a strong design and keeps the car original.

[Donunder]

Originally Posted by Cobra13

Thanks Don. With your great points and everyone else's, I'm going to stay with the original Arntz roll bar with forward brace. It seems to be a strong design and keeps the car original.

Great choice -- it's a distinctive roll bar and I certainly agree with you that for the sake of originality and authenticity it's what your Arntz deserves. And also as I mentioned before that forward brace sure comes in handy when getting in and out of the car!

Don't forget to post a photo of the finished article.