911 cage under construction

[bbh03]

Hi All,

Here are some pictures of the cage being constructed in my 911SC. Most of the fitting is tack welded at this point (some are in permanent) and a few changes are being made, however I wanted to solicit some comments here as well. As of now, the following changes/additions are planned:

1) The knee bar will be move to above the steering column and the steering wheel angled down further for a better driving position.

2) a cross bar will be fit in front of the fuel cell with bars stretching between that bar and the strut tower bar.

3) The diagonal is broken rather than the harness bar - this is being changed.

3) Gussets are planned but have not been added yet.

Some other info:

1) the bars ar 1.75" x 0.120 wall, so over spec for the car weight at my direction.

2) Fuel cell is just sitting there - he hasn't fabed the mounts yet.

3) The gentleman fabricating it is an experienced NASCAR carge builder, however this is his first shot at a 911. The design is based upon examples found and study of the SCCA GCR, NASA rules and the PCA rules.

A couple of questions:

1) He ran the bars extending to the friont suspension through fresh air ventilation holes in the front firewall. Any idea what is the bast way to seal around those? The sheet is not flat there.

2) Should I ask him to gusset the a-pillar bars to the A-pillars?

Thanks in advance for any comments/advice!
Have at it:

[EFullerton]

You have my attention but......the pictures did not post.....

[bbh03]

[bbh03]

[hatpix]

Sweet. Who made the seat?

[MattAlpha]

Brian,
I can't answer you questions, but that looks awesome!
-Matt

[Vintage911Racer]

Seat looks like Kirky or Butler.....

Pretty serious cage...too.

[bbh03]

Yup, it's a Kirkey Deluxe Road Race seat.

[JMatta]

Wish I had the talent to weld up something like that..great job!

[jaydubya]

I apologize if this is a stupid question but since my cage is going in a few weeks I'd like to know the answer. Why not take the mount points for the front hoop forward to make ingress/egress easier? See below.



Also, what was your reason for choosing NASCAR style door bars over the x-bar that is common in a lot of cars?

Cheers,

Jeff

[bbh03]

Jeff, I don't know exactly why he did that but I suspect it was to allow a straight bar to go from that tube to the front strut tower bar. I'll ask him. I don't think it impedes getting in and out as much as it looks like. It was the door bars that get in the way when I climbed in and out!

I chose NASCAR bars because I believe them to be safer. They allow more clearance from your body and are less likely to intrude during side impact since they bow out. I'm sure someone with more knowledge will chime in, either for or against this style. Unfortunately, everything is a compromise. The sacrifice is decreased crumple zone on the side. These bars protrude into the door, but only about half way in. I suppose it is a little more weight too.

I wish I had that skill too!

[jaydubya]

You're probably right about the safety, and with those bars, moving the mount forward wouldn't help with ingress/egress. I was thinking about having something like this done in my car, and for this design having the mount forward would make access a little easier.

[Jack Olsen]

That thing looks strong as a tank, and I'm not a cage expert by any stretch -- but the part I get a little iffy on is the dramatic curve of those side bars. I'd rather see them straighter, even if they're closer to the driver. A Pelicanite made a smart observation while looking at a piece I had fabricated -- he said any metal you bend is going to have a tendency to bend again (either further or back to where it was) when it's under stress. I don't know if that would apply with your doors -- the whole thing looks comfortably over-built. And I don't think I'd even suggest it be changed. But it's the one thing that came to mind while looking at the pictures, and maybe the observation will help people who come up with new cage designs for their own cars.

[Cory M]

If you want to get a lot of feedback and opinions post your pics over on the Racing forum at Rennlist.

A few things I noticed, just creative criticism, I realize that every cage involves making compromises to fit the car and driver:

The "knee bar" ends are bent, probably to tuck it in closer to the dash, but it would be better if the bar was straight.

You already mentioned fixing the diagonal in the main hoop with an unbroken length of tube.

I prefer an X to Nascar bars, for more room you can go with a gusseted pyramid shaped X like the 996-997 cup cars use (on the drivers side) and a flat X on the passenger side for a little less weight. The one thing I don't really like about your Nascar bars is how the tubing is bent where it attaches to the main hoop - it has an S bend to it - it would be better if the bar was bent the same as the front tubing- a single bend rather than the 2 bend S. A few santioning bodies have altered their rules to allow you to cut the door jamb so you don't need the S bend for clearance.

Add a diagonal to the rear braces.

Sit in the car and make sure the footbars aren't in your way. I have a size 14 so sometimes those bars take up too much room and I can't use the deadpedal which can make your clutch foot tired after a while.

Regardless of what anyone says, make sure you read the appropriate rulebooks and verify that everything is legal before finish welding.

[jaydubya]

Here is the door bar design that I was thinking about having done. What do you guys think of this?

[Cdnone1]

I am certainly no cage expert or biginner for that matter, but I have seen people add a support between the insides of the two rear shock mounts for added strength and stiffness
Steve

[MichiganMat]

Those NASCAR bars will be really safe if you're putting in lightweight fiberglass doors. Go check out the Bushwacker racing crash that happened at Thunderhill and you'll want those door bars as burly as they can be made.

[bbh03]

...

[bbh03]

Jeff, I don't think there is anything wrong at all with x bars fundamentally. And, if you're looking for ease of ingress/egress, X bars are the way to go.

Jack/Cory, I'll ask my fabricator why he chose the double S configuration for the NASCAR bars. I am putty in his hands with the door bars as I rely on him as the expert for those as a NASCAR guy. I'll report his thinking on it when I find out!

I like the idea of Xbracing the rear supports - maybe I'll have him do that in 1.5" tubing. As jack mentions it looks like a tank, but I need to stop the bleeding at some point with respect to weight! I think he may do the fuel cell protection in 1.5 x .120 also.

Hmmm, good point on the knee bar, but I think it will have to stay because of the placements of those front vertical pieces.

We toyed with the idea of ankle protection for the driver - a short piece from the horizontal heading into the trunk to the floor pan crease. I need to fit the pedals first to make sure it doesn't get in the way.

[bbh03]

Yeah - I'm cross posted to Rennlist on this. I'm about to go over and see how it faired under their scrutiny right now!