Seeking roll bar advice

[heavy85]

I sold my old L6 engine and trans today so have the cash to build a roll bar for the Z. As much as I desperately want to put a cam in it or A6's or other go-fast stuff it's time for some safety improvements. The car is under 2600 lb wet w/ me, runs a stock LS1, and full slicks. I run time trial type of competitive events mostly and any more only on the street to get to the track and home. It's a fast car so I need some safety improvements and think a roll bar is probably the first place to start. I've already built sub frame connectors, engine mounts, etc so I have the tools and ability to fabricate but no bender. I tend to buy tools when I need them so I have them for future use but am struggling spending the $$ on a tube bender that's not going to be used very often at all. So that leads me to how to go about this and I'm looking for advice from others who've been there.

 

Options:

 

1.) Autopower - dont like because it attaches to the fenders, want to better tie the chassis together

2.) Kirk - I like this much better but the back legs still attach to the fender wells and shipping is expensive

3.) Modified Kirk - if they would be willing to leave off the back legs I could add them myself to connect back to the strut towers. This way the bending is all done but shipping could almost cover a cheap bender.

4.) Find someone (?) to bend the bars for me and fabricate myself. Spend the saved money from not buying tools to buy a cam .

5.) Buy the cheap ebay etc bottle jack benders and fabricate myself.

6.) Buy a 'nicer' ratcheting pro-tools or JD2 bender and fabricate myself.

 

Next question is I keep seeing and even a relatively local (2 hours drive) SCCA cage builder recommends 1.75 x 0.095. SCCA says 0.095 but NASA says 0.120 wall thickness. 0.120 seems awfully thick but I run NASA and other's who have similar requirements. NASA also says that roll bars are for roll-over protection in open top cars so the assumption is the bar is the only protection. Since my car still has the factory roof structure would 0.095 still pass tech since that's the requirement for roll cages? For TT there is no requirement at all for a roll bar, I'm only adding one for additional safety and the extra weight is killing me especially if I need to go all the way to 0.120.

 

Thanks

Cameron

[JMortensen]

If you're just doing a roll bar I'd have someone bend the hoop, use Dan's gif that is posted here, and the rest of the bars will be straight and just notched. A Harbor Freight tubing notcher works for the roll bar notches because you don't have two bars coming in at weird angles and things like that. Once you start doing a cage the notcher becomes less and less useful.

 

I did my bar in 1.75 x .120 because of the discrepancy you pointed out in the rulebook. Too bad, seeing as how they now allow 1.5 x .095 for a cage in a Z. Stupid rules, unlucky me to build the cage just before they reduced the wall thickness.

 

I'd probably go 1.5 x .095 because I've never EVER seen anyone check roll cage tube thickness at an autox. If you've seen it maybe the tech inspectors in your neck of the woods are a little more fastidious, but I sure haven't. That way if you do a cage later you don't have an extra 30 or 40 lbs of tubing you don't need to have.

[rxsleeper]

Next question is I keep seeing and even a relatively local (2 hours drive) SCCA cage builder recommends 1.75 x 0.095. SCCA says 0.095 but NASA says 0.120 wall thickness. 0.120 seems awfully thick but I run NASA and other's who have similar requirements. NASA also says that roll bars are for roll-over protection in open top cars so the assumption is the bar is the only protection. Since my car still has the factory roof structure would 0.095 still pass tech since that's the requirement for roll cages? For TT there is no requirement at all for a roll bar, I'm only adding one for additional safety and the extra weight is killing me especially if I need to go all the way to 0.120.

 

Thanks

Cameron

 

Just something to think about, a roll bar will not have the same support structure as a roll cage and maybe you should consider a thicker tube wall if running only a bar. I am not familiar with the NASA requirments but does the tubing size change if you run a roll cage vs. just a bar? I know that SCCA TT has some different specs if only running a bar vs. a cage. I guess I need to go read the GCR again.

 

FWIW, I think you are headed the right direction with tying the bar into the rear strut towers whichever way you go.

[johnc]

The SCCA Solo1 and Solo2 rules regarding safety items are at least a generation behind the SCCA's GCR. The weight difference in a roll bar from 1.5" x .120" wall and .095" wall is not that significant.

 

IMHO, a roll bar made from the thicker stuff will pass a quick HPDE/Solo check and won't impede your performance much (if at all). Also, keep in mind that roll bars are not stamped with a serial number so if anyone asks just say its been in the car since 1995.

[heavy85]

The weight difference in a roll bar from 1.5" x .120" wall and .095" wall is not that significant.

 

IMHO, a roll bar made from the thicker stuff will pass a quick HPDE/Solo check and won't impede your performance much (if at all).

 

Did you mean thinner stuff would pass tech? NASA requires 1.75x0.12 vs 1.5x0.95 which is fairly significant difference. There is a difference in specs between cages and bars and bars are suppose to be thicker. Here's the excerpt from NASA:

 

11.4.7 Roll Bars

All open cars should have a roll bar installed to help protect the occupant(s) from injury

during a roll-over. The roll bar should be able to withstand the compressional forces

involved in supporting the full weight of the car. The roll bar’s main hoop should extend

the full width of the car (except certain cars that have been approved by NASA). The

main hoop shall be one continuous piece with smooth bends and no evidence of

crimping or wall failure shall be present (i.e. should be Mandrel bends). All welds should

be of the highest possible quality, with full penetration [Ref:(15.6.15)]. All cars with roll

bars are required to have adequate roll bar padding per CCR section #15.6.4. In cases

where the driver’s head may come in contact with the roll bar should the seatback fail, a

seatback brace is required in conformance with section #15.6.22. The material and

minimums are as follows: (All cars with full roll cages should conform to the applicable

sections found in section #15.0.)

Vehicle weight DOM or ERW

Under 2000 lbs. 1.50" x .120â€

2001 - 3500 lbs. 1.75" x .120"

Over 3500 lbs. 2.00" x .120"

 

 

Again I just want to add a safety measure to my 38 year old tin but at the same time dont want to be sent home for technical rules. I also am not building to a specific club since I run with multiple groups. I really think 1.5 or 1.75 x 0.095 would be more than sufficient since I have a roof structure in addition to the bar.

 

Cameron

[johnc]

Your car is not an open top car so that rule does not apply. You don't need to run a roll bar at all to compete in NASA TT. But, it really depends on your attitude and the attitude of the tech inspector when you show up at the event.

 

For SCCA Solo competition here's the pertinent section of Appendix C:

 

The size of tubing to be used shall be determined on the

basis of the weight and speed potential of the car. The following

minimum sizes are required required and are based

upon the weight of the car without the driver.

 

a) Over 1500 lbs.-min. of 1-1/2" o.d. x .120" wall or 1-3/4"

o.d. x .095" wall

Over 1000 lbs.-min. of 1-1/4" o.d. x .090" wall

c) Under 1000 lbs.-min. of 1" o.d. x .060" wall

Dimensions are nominal. 0.005” variation in wall thickness is

allowed.

 

In practice at NASA events they accept roll bars built to SCCA Solo specs.

[heavy85]

Well then since SCCA is 1.75x0.095 for rollbar and NASA is the same for roll cage I think I'll go with that.

 

Now to decide how best to go about this. Where do you find local shops that bend tubing. I'm in basically in nowheresville for racing other than dirt roundy round and their cages are SCARY in general to say the least. Or maybe buy a bender ...

 

Cameron

[JMortensen]

I looked on the local autox forum and asked if there was a cage builder local. I then emailed him Dan's gif and asked how much, he gave me a price and I paid him by cc and went and picked up the bent hoop and the tubing needed to do the whole roll bar.