Benton

Hey guys, I'm pretty much done with the roll cage. All that is left is to notch a tube for the a-pillar diagonal. Let me know what you think!

Geo

Mark, that is some seriously nice work. One of the best cages I've seen in a long time. Too many people try to get clever with cages.

Only two things I'd probably change. I don't care for the kneecappers and would (did actually) conncet that tube between the upper connections of the door Xs. Purely a personal decision.

The other, and you still can do this, is to redo the tube from the top of the a-pillar to the floor so it's a straight line to the bottom of the X and the front support node. From the photo it looks like it will have a bend.

Otherwise, bravo! Great job. And it bears saying again, I see so many poorly designed and/or executed cages that it's great to see one done so well. Prosit!

Benton

George,
That means a lot coming from you! Thanks! Do you think the kneecapper will be an issue? It actually hits the steering column support, so it's only 1.75" away from something else my knees could hit. It fits under the bottom of the dash, as seen in the pictures. I'm thinking it will be OK... a 928 has a fair bit more room than a 944; it looks closer to the legs in the pictures than it really is.

About the A-pillar... I may revise it, but I have a BIG issue with making it perfectly straight... the dash won't go in the car! I may just leave it as-is and have a small angle in it, because I can't figure out any way to install the dash without removing the steering column if I make it a perfectly straight line. I might try to straighten it out today.

Again, thanks!

Geo

Hmmm.....

As for the kneecapper, I did notice it fits behind the dash. Not knowing the 928 well enough I'd say for sure you know better than I. But before you finish, think of the films of crash test sleds and the movement of the crash dummies and let that be your guide. If you don't think there is enough movement to be of serious concern, I wouldn't worry about it, especially if you can get padding between the tube and the dash. Heck, if there isn't room, I'd probably even consider cutting out a bit of the dash where the padding needs to be and then install the padding.

I see know what the issue is on the tube. Let me ponder that a bit. Cages often require some compromise, but let me think about it. You may want to eliminate the tube entirely also since a bent tube is very weak.

chrisp

How is ingress/egress with that bar in the doorway?

Benton

Right now, I'm running a Recaro SPG without a halo. If I change to a halo seat in the future, I'll probably eliminate the bar. I felt that the a-pillar area was weak since the 928 has such a large door opening unlike any other Porsche. Here are some pictures of the notched tube tacked in... I think that in this configuration it should be pretty strong. The angle between the tubes is like 5 degrees. Thanks for the comments. I also attached a picture of the a-pillar fit. I'm pretty proud of that

BTW, George, I've taken a lot of cues and ideas from what you have said and from looking at your cage. So thanks for all of the help you have given me!

Geo

Hey Mark, I like it. I had actually thought about putting such a tube in my cage, but it would have made it impossible to get my fat butt in and out of the car. I agree that the angle isn't so bad. Not ideal of course (but cages usually have a compromise or two), but not bad at all.

Now that I see the tube behind the dash that the steering column hangs off of, I think I would have eliminated it and put a cage tube in it's place and weld the various brackets from it to the cage tube. Something to think about and/or recommend to the next person building a 928 cage.

All in all I think it looks great and the execution is great as well. Thanks for the kind comments BTW.

M758

That kind of looks like dash bar from the factory already in the 928.

The more and more I look at the 928 apprecite how overbuilt that car is in general. Sure its heavy, but my 944 does not have triangulated bar like that.

Geo

It is. I'd remove it and replace it with a cage bar. Then I would remove the brackets attached to it and attach them to the cage bar.

The Sentra SE-R has a similar tube running behind the dash from which a myriad of things are hung or attached. When we build the cage for my partner's SE-R we are going to remove that tube and do exactly what I described above.

That said, please double check any rules you may be bound by before trying this.

RedlineMan

Hmmm...

I simply can't imagine how anyone could get in or out of a car with a tube placed there. While I do understand why you did it, it would never even occur to me to try and solve this "problem" that way.

Instead, I'd go for the rear of the side hoop. This has two benefits. 1) it substantially stiffens the largest unsupported expanse of tubing (your goal) without effecting ingress/egress. 2) it offers very solid protection for you head, both for intrusion and also offers a halo effect to not allow extreme head travel to the side.

If your belt bar is in the right position for proper belt lengths, then you are closer to it and the main hoop than the windshield header. Since I would be more concerned with supporting the roof over may head than over my knees, I'd look to rear bracing, not the front.




Nice job, that notwithstanding!

Benton

John,
Thanks for the tip, and you definitely have a good point. I may look into revising the setup tomorrow and doing what you suggested instead. I took the cue from Mark Anderson (928 racer, Speed GT, etc.), but he said today that when he added a seat with a larger halo, he had trouble getting out. I'll definitely look at revising the setup tomorrow, and I'll post back with results. I really appreciate the help!

(glad I only tacked it in!)

38D

Now imagine trying to get out while being upside down, slightly dazed from hitting the wall at 60mph, with gas and oil dripping out of your car. I'd move that bar for sure.

Jack667

Is the cross also too high for emergency egress? Hard for me to tell...

38D

I would think that's ok. You basically just want to be able to crawl out the window without issue.

Adam Richman

Red, I want to say that the Lambos that ran ALMS last year had a very similar angle/plane for that additional door support bar. I don't recall it being an X door configuration but at the same time, I think the height of the door opening was half of what normal cars are. I notice a lot of folks going w/ flush door bar protection and am curious if you have determined how far away your upper body will be when seated and padded? Looks good and best of luck wrapping it up.

It is probably a body size issue. I am 5'7" and have a bar a bit akin to the one shown above and rather high door bar height and two rear braces (one a gusset panel, the other a gusset tube like the one you have shown). Maybe its my size or maybe its 12 years of martial arts but its actually not any harder to exit than my old car was. And I honestly don't think I have been removing the wheel to get out which would certainly buy a larger person more room to manoeuver. Another aspect is that because many of us have door bars that move considerably out from the plane of the a-pillar bar/main hoop, the opening, despite how confined it appears in a 2D photo, is more bucket-like opening both upward and outward.

You forgot a third value to that rear tube; a place to relocate fuel and trunk releases that you want available to your crew