M758

The biggest issue with custom cages I see is that workmanship is seperate from design. I guess to some degree I don't know why we would ever assume one guy can do both. When car companies build cars one guy designs and the other fabricates. Most engineerers like me can design good stuff, but I know I can't weld two pieces of scrap metal together.

A good cage will consist of 3 elements. 1) good materials 2) good fabrication 3) good design.

Now which is the worst... probably bad fabrication... As it can make it look ok, but perform poorly when called. Bad design can happen, but very rarely are cages so poorly designed to be dangerious. Some are, but most may not be optimal and have the best strength / weight ratio.

claykos

Exactly the point I was trying to make.

There are a lot of guys who can weld up a BEAUTIFUL cage (and the cage in this thread looks very nicely put together). There are fewer guys who can design a really nice cage, and even fewer yet who can do both!

And I have seen plenty of cages in "pro built" cars for "professional" series that were almost laughable...

RedlineMan

Hey;

No wolves here. Just some good advice, and also the usual internet chatter. Filters on. Take it for what it is worth. For my part, I just don't want to see a Brother get burned. You can have a builder with a sterling reputation, tons of expereince, big skills, a great client list, and a box of chocolates too. But if his stuff doesn't make sense... if it strays in too many places from concrete convention, where are we going with it? A Rolex is a great watch, but it loses some of its luster if it runs backwards, eh?

I doubt the cage is unsafe. It is certainly sturdy in many respects. My exceptions are logical, as that seems lacking in some areas. More than a matter of opinion or style, my thoughts are more toward sense and sensibility.

Whether you are a fan of NASCAR bars or not (I'm not, for structural reasons), if you want to build them in a sedan, you have to put the main hoop near the door opening (that is true for most any outward projecting door bar). I start to wonder when I look at the bent belt bar. Certainly for someone 5'6", the bar could easily be straight across between the hoop. Strike 1. One caveat to that might be resale to someone of taller stature.

That notwithstanding, he still could have made the diagonal straight, even center-tieing it to a bent belt bar as he did. Strike 2. Not only does that diagonal have a bend that it should not, but it does not terminate at the base of the passenger side of the main hoop. Strike 3. Next batter.

He adds a second diagonal, but it does not terminate at the frame sill either. It terminates on a cross tube between the rear stays; a tube which is utterly redundant. Strike 1. Yes... two diagonals may make it super strong regardless of where they terminate, but doing the job with one correctly rendered tube weighs less. Strike 2. Said rear stays should really terminate closer and create a node with the front side hoops. Strike 3. Two batters out.

The center roof tube is indeed not placed effectively, since it is relying for help from two areas that are unsupported. In fact, it may lead to the failure of those tubes if activated. You gotta deal in nodes!!! Strike 1. The belt retaining loops are indeed much too far apart. For someone of your stature, likely wearing a small HANS (and assuming short belt lengths), they should probably place the belts no more than 3" apart. Strike 2.

I'll get picky and combine a couple of nits. I think because he put header tube so far down away from the bend in the main hoop, he should have corner braced that area. I also think the bottom tube of the door bars should have been a low as possible, near the base plate node. Strike 3, Side Retired.

Sounds like a big rant, I know, but it's not. I've had people pick my stuff apart too, right here in public. A few of their words had merit, more of it was pure preference, and a lot was just plain ignorrance. The bottom line is that cages are critical items, and if this makes you think CRITICALLY, it is all good!

daigo

I too agree. I know its tough to post here and get bombarded as you have. But there are actually many good points in these responses. In my humble opinion and experience this cage is very well fabricated, but very poorly designed. Sorry. This is a very good example of poor efficiency in design. A great example in efficiency is the GT3 cage. These cages are designed and refined after many incidents in racing. Do you see massive Nascar bars? Matter of fact, the door bars don't even have a bend in them. This is by design. Anyway, I apologize for the negative feed back but you did ask for opinions.

Good luck with your car.

RedlineMan

Some items others have mentioned;

Corner braced head tube.




Corner braced side hoops.



Uninterupted straight diagonal to node areas.



Simple but HIGHLY effective corner gussets.

disasterman

I have absolutely learned a ton working on (and posting on) this project and I think the discussions should be lively. This is my first track car, let alone race build and I am constantly second guessing myself on everything from spring rates to wheel sizes.

There are gussets at the main hoop to A hoop connection.

joseph mitro

i'm not a big fan of those corner gussets. my cage builder put those on my cage, and i think they could have been better substituted with taco sheet metal gussets.

i do like the halo/A pillar bracing you showed, which I later added to my own cage.

DanR

dumb question as I look at your seat on the bench, but does your halo seat still fit in through the door bars (they seem high leaving little room to fit a blucky seat through)

Could always go throughthe empty windscreen if not i guess.

disasterman

Funny that you should ask. The seat on the bench belongs in the Cup car, my seat is a Recaro Pro Hans, so basically the same thing. It goes through the windshield, plexi that is held in with screw fasteners (easily removed).

J richard

I hope you haven't taken comments too harshly, I will say that if I had listened to some of the comments I got about cage construction on this forum I would have saved myself considerable time and money with retrofitting components and had a cleaner solution in the long run. I still think you've got a nice setup, just getting the details worked out...god is in the details...

disasterman

It's cool, I checked every thread I could find and reviewed all of the photos before I had it built. I am very satisfied with the safety aspect. It is helpful to check approvals from NASA though and I will measure and confirm the belt threading loops. It is my understanding that the bend went into the diagonal to allow a larger driver, I expect to endurance race the car and other driver may be as much as 6'4".

I have to sort this out quickly, time to get it on the track.

Greg Smith

I agree. IMO, gussets aren't really needed there(what looks to be between the main hoop and rear down tube), there are many other places I would put them before there.

RedlineMan

Well...

Tacos only fit close to 90* corners well. I end up spending more time trying to make them fit than just cutting my own piece. Besides... anyone can use someone elses part. Where's the art in that?

The idea is to spread load away from the weld joint - the most vulnerable spot - and into the surrounding tubing where it will dissipate instead of focussing. This is a good idea no matter WHICH joint you are talking about and these little doodads add a LOT of stability and strength to any node with virtually no weight penalty.

THAT is how you make a cage strong and light; a few well placed tubes, and details.

Julian Allen

John,

Would you care to show the entire mounting system for a window net you are using?

I like the idea of a "funnel" to direct the rod into the receiver.

Thanks.

RedlineMan

Other than the artful install, it's just your basic net system. It works stoopid easy. Almost effortlessly!