Windshield rollcage cross brace

[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)

[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.