Windshield rollcage cross brace

[rsportvolvo]

I can't seem to find any verbage in the GCR forbidding the use of tubes across the windshield area. These are quite common the Aussie V8 Supercar Fords and Holdens (see link below). FIA regulations have a area that must be kept clear. Any tech folks have some comments?

http://www.carsales.com.au/news/2006/large-passenger/holden/commodore/holden-ve-racer-%E2%80%98officially%E2%80%99-debuted-2136

[quadzjr]

from a structual standpoint I can see why you would. however idont' see how that wouldn't obstruct view. Maybe on larger cars it won't be as bad.

[Greg Amy]

There are no restrictions to this, however since it is not typical I would discuss this in advance with your local SCCA tech inspector to ensure they don't have a problem with it.

[joeg]

They act as big gussets...no problem

[MMiskoe]

I've seen cars w/ a horizontal bar across the top of the dash for lack of space under or in it.

[rsportvolvo]

I was referring to the diagonal tube, not the high knee tube.

[seckerich]

While it is legal it is not very useful when you can not tie the cage to the chassis above the floor. It will help cage cross strength but will do almost nothing to stiffen the car. Consider the weight up high for almost no gain. Sure looks cool!! :D

ps. I was looking through an old thread the other day and I was somewhat of a jerk in my response to you. I am sorry, was having a bad day.

[rsportvolvo]

Why can't I tie the roll cage into the uni-body above the floor? Only 6 of the 8 points allowed are near the floor. The other 2 are open. I will be tying into the firewall were the factory strut-to-firewall braces mount. This way I have a load path from the strut towers to the roll cage.

My car will be a bit on the light side so adding a few extra tubes isn't a problem. Since non-required tubes can be any size I can use a smaller diameter piece of tubing for the windshield diagonal. This way I get some added cage stiffness without as big a weight penalty.

You were a jerk to me? If so I don't recall when.

[Greg Amy]

I will be tying into the firewall were the factory strut-to-firewall braces mount. This way I have a load path from the strut towers to the roll cage.
Just ensure you're actually touching the FIREWALL PANEL itself; cars have been bounced and forced to mod their cages because they attached to brackets or braces that attach to the firewall... - GA

[markw]

I believe any additional tubes added are required to be the same diameter as the roll cage in IT. The view can be very obstructed. Here is my view and my windshield braces are smaller than the 1.5 roll cage tube.
http://www.youtube.com/watch?v=DT9gpNnoJTo

[rsportvolvo]

I believe any additional tubes added are required to be the same diameter as the roll cage in IT. The view can be very obstructed. Here is my view and my windshield braces are smaller than the 1.5 roll cage tube.
http://www.youtube.com/watch?v=DT9gpNnoJTo

The 2010 GCR states:

9.4.F.3 The required tubing elements must meet the material minimums set forth above. Optional tubing elements may be any size.

[markw]

Well, I guess I was wrong. Anyhow, my point was, racing my car is like looking through a jungle jim. You don't notice it once you start racing, but sitting on the Grid you wonder how you are going to drive it. Fortunately when racing, you are always looking far ahead. If it were my choice, I'd rather have a much a clear view as possible. Since my car is a GT car, there is some torsional stiffness that comes from these added braces.

[Speed Raycer]

A diagonal bar across the windshield would be one of the last bars I'd add. I can think of about 10 other bars that'd give better results.

From FEA that I've seen, you're better off making a diamond l<_>l

Problem is that pesky dashboard and steering column.

[Greg Amy]

I think it was Carrol Smith that said something like 'the only thing keeping me from making a perfect cage is that g-d driver!'

[rsportvolvo]

A diagonal bar across the windshield would be one of the last bars I'd add. I can think of about 10 other bars that'd give better results.

From FEA that I've seen, you're better off making a diamond l<_>l

Problem is that pesky dashboard and steering column.

I can't dispute your FEA results, but I know that the V8 Supercar teams spend a large amount of money developing their cages, specifically SBR. The diagonal is there for a reason (**They also put a diagonal in the floor). Now those cars have more tie-in points to the uni-body and that may be where the stiffness gains are had.

[Speed Raycer]

.... and I don't dispute that it's there for a reason. The problem is, you're falling into the trap of adding a cage bar for the simple reason that a completely different type of car uses it.. and you can't explain why. ;)

Let me clarify what I said before. In Improved Touring, with our restricted cage rules, I can think of several bars I'd rather add before I got to adding a diagonal across the windshield. If all of those bars were added, and I thought there was still some improvement possible, and it wasn't obstructive to the view, didn't push weight up substantially, was able to cleanly tie it into tube nodes as well as deal with the dash/driver/column/heater core etc issues, I'd consider something similar.

I've never actually looked at the SafeRacer cage to see what the bar ties into, but depending on the roof bar setup, this looks right up the alley (bottom pic)
http://grassrootsmotorsports.com/media/img/articles/IMG_2949__t240.jpg

[rsportvolvo]

I'm not randomly adding tubing. I'm reinforcing the largest open (unsupported) areas within the car. The windshield area is one of them. I don't have the software or surface plate setup to accurately model & measure the gains of each piece of tubing. I'm plagiarizing the designs of top programs running stock bodied cars (BMW Motorsport, Porsche Motorsport, Prodrive, TWR, SBR, etc.).

What other tubes do you recommend adding over the windshield diagonal brace? Here's a summary of my roll cage layout as I have it sketched up.

- standard 6 pts. with rear down tubes picking up the rear spring mount
- knee bar as req'd
- x-brace in both doors, main hoop, rear down tubes
- brace from main hoop shoulder bend to rear mounting point
- x-brace from front down tube to firewall to pick up strut tower braces (Factory braces)
- Petty bar from above driver head to pass. side down tube floor mount
- halo diagonal from pass. side main hoop to driver's side down tube
- windshield diagonal brace from driver's side top to pass. side knee bar.
- main hoop shoulder bend to top of a-pillar
- top of a-pillar to front down tube floor mount

* all points will be a single node as much as possible to reduce moments within the cage itself.
** only req'd tubing will be req'd size, all other sizes will be smaller.

It'll be a spider web, but I know I'll need some ballast so I might as well get some stiffness/safety out of it.

[Jonathan]

How come in all of this no one has mentioned safety as a factor for adding windshield bracing? The way SCCA cages are constructed, there is no true "halo" bar that is tied in behind the driver that encircles the entire head area. Instead it's a single tube cross-brace that is out there all on it's own and unsupported, leaving your life accountable to 2 welds on either end in the event of impacting a wall or another car with your roof. I added more of a NASCAR style downbar in the center as well as some corner bracing and gussets, as well as an extra roof bar from the center of the crossbar rearward. In-experienced drivers and safety workers as well as tracks that might have something to be desired for safety should make us all think about safety first, then the benefits of performance second. You can't race from the hospital bed.