Roll cage advice...

Porsche Technical related discussions.

Roll cage advice...

Postby 4est on Thu Jul 23, 2009 2:28 pm

SCCA specs call for 1.5", 0.95 tubing in a car in my weight class (less than 2500 lbs). I keep hearing that most people like to do the main hoop in .120 wall. Why?
User avatar
4est
Time Trialer
 
Posts: 225
Joined: Sun Jan 15, 2006 9:38 pm

Re: Roll cage advice...

Postby Dan Chambers on Fri Jul 24, 2009 10:10 am

Forrest:

Not sure why anyone would want to go thinner in the top-hoop of a rollbar. Weight of the car is definitely a factor ... then try to calculate the amount of stress placed on the bar when the vehicle is travelling at 100+ MPH, hits an obsticle, and lands squarely on the roof before commencing to roll over and over until it stops.. :roll: Let's see:

T=vC(2)/~%risk factor
(Oh sh%^$t/Dumb-@$$)

Okay, so those are my calc's.

I used a standard Autopower roll-hoop and drops, and had two additoinal bars added (both made by Autopower): a rear brace that travels behind the seats, and a diagonal that goes from "just left-of-center" (near driver's head) to behind the passenger seat for additional strength.

I had the "pitch" adusted slightly to the rear to compensate for our (Monica and my) height and seat positions, and a custom mounting system that involves both welded and bolt-in application. The total cost wasn't really more than a standard weld-in system that Autopower offers here in town. As far as I'm concerned, a little extra weight/metal is worth the safety factor. I tend to bend less and break more these days. :oops:

You should call the folks at Autopower and discuss all this stuff. They can be helpful, depending on who you talk to.

Hope that helps.
Dan'o
User avatar
Dan Chambers
Pro Racer
 
Posts: 1761
Joined: Wed Jun 30, 2004 3:57 pm
Location: San Diego

Re: Roll cage advice...

Postby Steve Grosekemper on Fri Jul 24, 2009 3:43 pm

Because everything ties to the main hoop and it acts as the foundation for your roll over protection.
Here are Z-8 and CR requirements.

PCA Z-8 roll bar/cage requirements
When roll bars/cages are required, all occupants helmets must clear a straightedge placed between the top of the windshield frame, directly in front of the occupant’s head and the top of the roll over protection directly behind the occupant’s head when seated in a normal driving position and restrained by belts and harnesses. Roll bar minimum dimensions are: Wall thickness .120", diameter 1¾". Full roll cage dimension is 1½" diameter. A 3/16" diameter hole shall be drilled in a non-critical area to allow verification of the wall thickness. Roll bars must be braced. The roll bar hoop and all braces must be seamless, ERW or DOM mild steel tubing or chrome molybdenum alloy steel such as SAE 4125 or SAE 4130. It is recommended that mild steel tubing be used as chromium alloys present difficulties in welding and must be normalized to relieve stress. Proof of the use of alloy steel will be the responsibility of the entrant. No aluminum roll bars or cages allowed. Forward braces (roll cage) and the main hoop subject to contact with an occupant’s helmet, should be padded with a non-resilient material such as Ensolite, Ethafoam, or similar material to a thickness of ½ inch. A car equipped with a roll bar or roll cage that meets the technical requirements for that car to participate in PCA Club Racing is adequate for PCA Zone 8 Driving Event use. Evidence of meeting these requirements shall be provided by the driver, if necessary.

PCA Club race roll bar/cage requirements-
Minimum Roll Bar Tubing Sizes Car Weight without Driver
Under 1500 lbs Over 1500 lbs
Mild Steel 1.5” x .120” 1.75” x .120”
Alloy Steel 1.375” x .090” 1.625” x .095”
Minimum Roll Cage Tubing Sizes
All required tubing must have the following minimum diameters and wall thicknesses:
Car Weight without Driver
Under 2500 lbs Over 2500 lbs
Mild Steel 1.50” x .095” 1.75” x .095” or 1.50” x .120”
Alloy Steel 1.375 x .095” 1.50” x .095”
Steve Grosekemper #97
http://www.911SG.com
https://www.facebook.com/911steveg/
https://www.instagram.com/steve911sg/
PCA-SDR Tech Advisor/Scrutineer/Forum-Admin
1997 993S & 986S street cars & 911SC track car.
User avatar
Steve Grosekemper
Admin
 
Posts: 1379
Joined: Thu Jul 01, 2004 6:15 pm
Location: San Diego

Re: Roll cage advice...

Postby davidsq on Sat Jul 25, 2009 7:41 pm

RUN 4EST, RUN 4EST, (you knew it was commin')
you got a street car, bolt it in...other than that...u know what to do.
or, you goin' to cut bait or fish ? :)
steve is good, don't tell him i said that. :twisted: use the rules and reg's...
where u goin' w/ this thing :?: think ahead.
User avatar
davidsq
Time Trialer
 
Posts: 271
Joined: Sun Dec 10, 2006 2:52 pm
Location: hiding from the 912 registry

Re: Roll cage advice...

Postby 4est on Sun Jul 26, 2009 10:17 am

Not nearly a street car anymore! Thanks, Steve, for the specs; I went with the .095 and the main hoop is in. It looks great: very tight, fitting the B-pillar all the way up and welded front and rear. Doors still open and close as designed. Odd (very slight) deformation of top of rear fenders?! Noticed the one on the driver's side, and thought it looked like one of the boys had climbed up on the car and left a little kid's footprint indentation. Popped right out (found one on the passenger side, too). On to the back stays and etc. I will wait to do the forward stays; they look to be complicated... maybe even more so than the main hoop. I want to make some real progress with straight tubes that just need to be shaped and welded in; I am tired of precise measuring and carefull bending just to be 2mm off. Don't ask how many atempts for the main hoop... just keep in mind how much of a perfectionist I am and you will know.

I have seen a million configurations for the rear part of the cage. If anyone has any advice on the best one, let me know. I want stiffness, but don't want to use any tubes that aren't absolutely neccessary. I am copying Albert's RSR, mostly, but would appreciate any thoughts. Gonna do an X for the doors for chassis stiffness and NASCAR bars for side-impact protection. Also, I am thinking about using smaller diameter tubing to span/reinforce important angles instead of gussets (saw it on the Duncan 996). Any thoughts on this?
User avatar
4est
Time Trialer
 
Posts: 225
Joined: Sun Jan 15, 2006 9:38 pm

Re: Roll cage advice...

Postby 4est on Mon Aug 17, 2009 9:21 pm

It's in and looks great. Prepping it for paint- tough to get to some areas. Time consuming (to say the very least) but a custom cage that would cost somewhere in the vicinity of $4,000 for around $300. Tough to beat, if you have the time.

Check it out at Coronado...
User avatar
4est
Time Trialer
 
Posts: 225
Joined: Sun Jan 15, 2006 9:38 pm

Re: Roll cage advice...

Postby kleggo on Thu Aug 20, 2009 9:10 pm

4est wrote:It's in and looks great. Prepping it for paint- tough to get to some areas. Time consuming (to say the very least) but a custom cage that would cost somewhere in the vicinity of $4,000 for around $300. Tough to beat, if you have the time.

Check it out at Coronado...


WOW
You should take Forrest's advice and "Check it out at Coronado"
His cage workmanship is pretty amazing.
i gave up counting at tube # 30+.

The only drawback? I told him that his Noise / Vibrations / Harshness will most likely increase :shock:

be safe

Craig
User avatar
kleggo
Time Trialer
 
Posts: 399
Joined: Wed Jul 25, 2007 4:43 pm

Re: Roll cage advice...

Postby pdy on Fri Sep 25, 2009 10:15 am

kleggo wrote:
4est wrote:It's in and looks great. Prepping it for paint- tough to get to some areas. Time consuming (to say the very least) but a custom cage that would cost somewhere in the vicinity of $4,000 for around $300. Tough to beat, if you have the time.

Check it out at Coronado...


WOW
You should take Forrest's advice and "Check it out at Coronado"
His cage workmanship is pretty amazing.
i gave up counting at tube # 30+.


Craig


+1 on Forrest's cage - it is art. Quite apparent he spent a LOT of time planning, engineering, and "measuring twice".

Very impressive work!
Paul D. Young http://www.deadpetsracing.com/
PCA Nat'l Club Race Advocate
Now: '78 911SC, '79 911SC, '04 955-S, '06 997-S, '88 924-S, '16 92A
Past: '74 914, '78 911SC, '78 928, '80 924-S, '82 931, '86 930, '03 996-4S
User avatar
pdy
Time Trialer
 
Posts: 466
Joined: Thu Aug 05, 2004 2:32 pm
Location: 2nd Place - Usually

Re: Roll cage advice...

Postby Dan Chambers on Sat Sep 26, 2009 9:55 am

Absolutely perfect. I checked the tolerances of the door fit, the seats, the angles, the weld-seams and pick-up points to the body ... awesome!

Nice work, Forrest. I remember when that car was a pristine C4S at your first AX's. That car has come a long ... and beautiful way. Great work, man. 8)
Dan Chambers
"It's just a "well prepared" street car ... or a very, very well-mannered track car." :burnout:
1983 SC #91 3.6L, "Black Pearl" Livery
1987 944 (gone but not forgotten)
User avatar
Dan Chambers
Pro Racer
 
Posts: 1761
Joined: Wed Jun 30, 2004 3:57 pm
Location: San Diego


Return to Technical

Who is online

Users browsing this forum: No registered users and 29 guests