RX-Ben

Dumb/lazy question- what are the 100" and 12"x2" rules?

thanks
Ben

cagedruss

SCCA rule allows 100" maximum area, with no side longer than than 12", and no less than 2" narrow (I think, go from memory, always refer to the GCR). Plate can be multiple angle, but if measured flat must meet the rules.

RX-Ben

Thanks

Ben

Carl Byck

100 square inches. Does this apply to SPO? I do not think so since most are tube frame. My car is SPO/ NASA Super Unlimited.

Carl Byck

I'll let you know on the gussets, Thanks, Carl

Speed Raycer

AFAIK, the 100 sq in. rule is only in SCCA SS, SM & IT ... I'd have to look at the Prod. and Touring rules again

I'd check on the NASA rules to be sure. They were obviously based on the SCCA's rules, but they've had enough time to evolve a little.

cagedruss

100" rule only referes to cars with the 8pt rule for the cage. Classes like Sp and GT would not be affected unless you are building a tub style car ( Porsche, Rx7 ). And if the car you are building has a full steel frame with a factory body bolted to it (aka; Chevelle) would be required to have the cage welded directly to the rail.

As to the question about using the top diag. bar, yes, use it. It only weighs 6-10lbs, but would help the a-pillar and cross bar from collapsing in on a freak accident and does make the chassis stiffer. Having additional weight up high is bad for handling, but the weight is minimal. I doubt that the majority of Racers would never feel the difference. The advantages of the tube out weigh the negatives. It is also one more thing between you and the track surface if you are up side down.

maxpesce

Because (irrc) IT rules don't allow the cage to extend in front of the fire wall, or take suspension loads. oth, Production class cages can tie directly to suspension pickup points.

designfreak

but most cages run legally with the downbars going to the wheel arches next to the strut towers.....including even the bolt in cages. In actuallity its much more common to see cages going to the wheel aches than not.

Even considering that the downbars tie into the frame rails what would be the benefit of passing the loads from the towers to the frame rails to the cage, when you can go directlly from the towers to the cage? If its a rules issue, I havent seen it enforced, if its a structural thing I must still be in the dark here.

The entire point of the frame rails is to counteract stress from the towers, why not just go to the source?

Carl Byck

In my case, I am going from the frame rails to the cage, and seperately going from tower to tower, and from tower to main hoop. Make sense? Basically a Ginormous strut bar tied into the cage, not the frame rail directly. The rear towers are a weak point in the FC do to the factory set-up. Thus my earlier question RE how people are reinforcing the top of the rear tower, and if there is a bolt in part?

Speed Raycer

Again, I know little of the design of the FC and I'll defer to Russ on this one as he's done quite a few more cages than I have.

MY reason for the rear downbars going to the frame rail would be that it's a much stronger place to connect to. Obviously the design of the FC's rear strut towers is lacking... You want your life depending on the strut towers in an off-angel rear collision with a concrete wall?? I'd give up a little suspension flex to know that my rear cage braces weren't going to let the cage get compromised.

If you're concerned about the suspension movement, come up with a pad design with the pads tied into the framerails as well as the strut towers that allows you to add a crossbar between the struts, and place the rear hoop braces on, or very near the frame rails.

Be conscious of the placement of the rear crossbar. As someone referred to higher up, it is possible to form a protest on a bar that is installed in a way that its primary function is suspension related and not safety ( for example: a crossbar all by itself between the struts that doesn't touch any other bar).

Also, rear hoop braces that are mounted on the crossbar as opposed to the pad- in my opinion, not a good design and not legal per the SCCA IT rules.

On Carl's question... Wasn't the top of the strut tower a speaker cabinet and the strut mount actually down in the hole quite a bit?

As far as basing things on where bolt in cages mount... They mount in the easiest place to get to with a drill.

cagedruss

Mounting the rear bars on a second gen 7 is really easy. Take a pad that is no bigger than the 100" rule. I seam to stick to 6"x10". Form the pad (brake) so it is approx 4-5" tall with the remaining material is at a right angle. Weld it to the top of the uni-body rail and the side of the shock tower. I have never seen anyone protest a cage for having the rear bars mounted to the shock towers in any class. I try to attach the bar to the flat of the floor with the side touching the side of the plate and welded to the side. That gives more surfacing weld to the structure. Then add a bar from side to side. Looks a little funny in a 7, because it is so low and it has to be the same size material as the cage to be legal with the rule.

You also have the option of a rear X or Diag. to stiffen the rear. I read a comment earlier about attaching bars to the towers to keep the shocks/stuts from hammering the back side of your head, if a wreck was bad enough to do that, you are already dead. The rear bars are there to keep the main hoop structure rigid, gaining rear suspension rigitity is a bonus. Unless your car is a Coil over car, the stress from shocks alone are minimal. Focus on keeping the main hoop from moving.

Suspension/roll cage tie in is more critical at the crossmember mounting area on the chassis or spring pocket area on the chassis. That is the real load. Examples of that would be a Rally or stock car. IT and show room stock doesn't really gain much advantage.

Above statement about attaching down tubes to the wheels arches, I have never seen that. All down tubes must be attached to sill/rocker/floor in front and to frame/towers in the rear. Wheel arches offer no structural rigitity. I will take part of that back. I have seen some bolt in cages that do attach the rear support tubes to get around the rear seat. Mostly in Street bars that have been converted or a SS cage, same there also. That is another reason why a fabricated cage is better than a bolt in.

Alot of this is getting really over analalyzed, keep the cage basic with in the parameters, use as much material for floor plating to help distribute as much load and stress as possible. Keep bends to a mininum, keep the cage as close as possible to the body/chassis for strength and allow as much room for crush away from the driver.

designfreak

Thanks guys, youve been real helpfull!

EProdRx7

f some one could host them 'll send pcs of my EP FC. Also anyone know how I can fix the "i" on my fu**ing keyboard!

ddewhurst

John, to fix the "i" on the keyboard take it to Matt. ; ) Opps, the fu**ing keyboard.

What's with the Miata ? F ? or are ya down sizing to the new National class ?

Sprints ?

Runoffs ?

What ever Have Fun ; )
David

ps: Bring Bill & beer. Naw, bring beer & Bill.

88GTU

A few pictures of my NASA SU car's cage:

http://www.bfimotorsports.com/matt/c...s/DSCN0571.JPG

http://www.bfimotorsports.com/matt/c...s/DSCN0570.JPG

http://www.bfimotorsports.com/images.../DSCN1154.html

http://www.bfimotorsports.com/images.../DSCN1153.html

My favorite part about the cage is how it ties the lower nascar bar to the rocker panel and triangulates it through the floor to the frame rail. I've seen an RX-7 t-boned and its not pretty.

-Matt

PS: Its for sale!

christaylor

Hey Matt, is that 1.75" tubing?

EProdRx7

Dave, Maybe SM, SSB or SRF. Undecided as of now. All four (SRF x2) are rentals for now. I still have the EP chassis too! He who dies with the most race cars wins!

BDC

I've got a few older pictures of my 6-pt rollbar from about 2 1/2 years ago when it was freshly done. Kirk Prewitt at PrewittRacing in Austin, TX did the steel gussets and the welding; SUPERB job. http://www.prewittracing.com

http://bdc.genxracing.com/Rollbar/

B

designfreak

Does anybody have any pictures I could take a look at of the "L" bracket setup suggested above ( rear bars welded both to the frame rails and the sides of the strut towers)? This would be a big help to show my fabricator.

Thanks

cagedruss

I would normally post a pic of what I discussing but my computer losts it power supply and mother board. All my pics are on that hard drive. It is really easy to do. Your fabricator can do it. Probably already has done it. Just a flat plate, 8x6 or what ever size you decide, broke at a 90 degrees. Lay half on the floor/frame and the other rests on the side of the tower. Rules recommend plating as many angles as possible.

designfreak

got it, thanks!