Fabricating a roll bar for track racing
 

I'm about to start some low level club track racing with my '87. Because its a cab, I want a 4 point roll bar at least, to protect my thick head!

Given my location, I doubt I'll be able to find an off the rack type item, and getting one from overseas will just blow the $$.

Could I get a good welder to fabricate for me or am I kidding myself? Is it an art, or is it fairly straight forward? (eg show him some example of what I want and let him get to it).

Am I being a cheapskate about the value of my life and should I spend the cash to get a reputable o/s manufacturer of these items to freight me one ready to bolt in?

If you think getting a welder with some credentials to make one up for me is ok, what type of tube thickness should I be thinking of?

Thanks for advice.

Cheers
Mark

Mark, Making a cage is a major undertaking. being that your car is a cab., it makes the job a bit easier in regard to fabrication but more stringent when it comes to design. I would take a look at a Safety Devices cage. I believe they make one for Cabs. That would be a good starting point. As far as wall thickness goes, I would check with the sanctioning body with whom you plan to race with. They should have specs. that will help you decide what wall thickness you will need. I have put the link to the PCA Club Racing website below. There rulebook is downloadable and has a good section on what they require in regard to roll cages. I am a TIG welder and will be putting a cage in my car within the next few weeks. If you would like some pictures of the process let me know and I can send them along.

PCA Club Racing

Best of Luck!!!

Cheers, James

I don't know how much welders a paid where you live. It is much cheaper to buy a roll bar and install it than to pay someone to custom make one. But maybe with shipping that is not true. Get a rule book and they will tell you what you need for the gauge of the bar. I think it is right around .120"

James,

Thanks for the link. Yes I would like to see photos as you go. Good luck with it.

I'll find out more about what happens over here when some people I've emailed get back to me.

Expathk;

The one thing that I would stress is that your roll bar or cage is there to save you when things go wrong -- horribly wrong. You may (or may not) feel like skimping now, but there is nothing like the sinking feeling that you will feel in that split second before the car hits the wall and you remember that you didn't put as much into your safety gear as you could have. Believe it or not, you will have time to think about your wife, your children, your parents. etc.

So -- moving on...

Welding a roll cage is pretty straight forward if the welder knows his stuff. I wouldn't do it myself unless I was confident that I could weld a good seem.

Having purchased an Autopower bar in the past, and seen what a professional welder (Chris Foley at CFR Welding in Connecticut) can do at his shop rate, the make versus buy decision comes out about the same price wise. Given the labor rates in Asia, you might do better sourcing it locally then importing it.

The material is critical to the success of your bar. A well designed bar using poor material is nothing but a piece of junk. The material that you should use is 1.5 (dia) x .095 (thickness) inch mild steel (or metric equivelant) minimum. If your car is over 2500 pounds or you want a little extra strength, you should use 1.5 x .120 inch mild steel (Drawn over Mandrel and seamless). Since you are not building a cost is no object racer, stay away from alloys. They may be stronger pound for pound, but they tend to be more brittle and lack the toughness to withstand multiple impacts.

Once you have the right material, it needs to be mounted correctly. To avoid the bar punching through a body panel, you want the mounting plates to cover the largest area possible. At a minimum they should .080 inch thick (if welded in, 3/16 inch if bolted in). Whenever possible mounting plates should extend onto a vertical section of the car's frame.

In general the cage should be MIG or TIG welded. Avoid stick welding or brazing.

The welds should be inspected (most likely by you) to the following conditions:

1) The weld should have no cracks
2) Thorough fusion shall exist between weld metal and the base metal.
3) All craters should be filled to the cross section of the weld.
4) Undercut shall be no more then 0.01 inches deep.

If you are not sure what they mean, the welder should be able to explain them to you. If he can't -- find another welder.

Finally; here's a thread where I paraphrased the SCCA requirements for a roll cage. Since you only want to go with a roll bar, you can still get some good ideas from it. I would focus on the parts that define the main hoop and bracing.

And just remember -- Roll hoops and cages are like insurance. It will be too late to change your coverage when you really need it! Good Luck!
SmileWavy

James,

I'm thinking of installing a cage this winter. I'm a tig welder also but wouldn't have a clue in how to build a cage. Are you building one from scratch or buying a prebuilt one and welding it in? I would like to hear how your going about this project. BTW I have an 84 targa.

Thanks,

Tim

i don't know if its application is suitable for a cab, but TRE motorsports make a RSR type roll bar...one is being installed on Jack Olsens car...he has posted pics

http://forums.pelicanparts.com/porsche-911-technical-forum/90657-building-better-black-beauty-3-reinforcing-chassis.html

and TRE is here

http://www.tremotorsports.com/

MJ

Tim, I have a friend who has a body shop and has all the mandrels to bend the tubing. He has a pattern that he/we came up with from a 964 Cup car. This cage has lots of triangulation that makes it very strong and safe as well as stiffening the chassis. This cage also has good rear view visibility. i'll post pictures once I start getting it in the car.

Cheers, James

James,
When you make your cage I don't think you can bust through the rear firewall like on the Cup car, so you better check before you do it otherwise they'll bump you out of stock class.

Hey John, Good to hear from you!! I don't plan on going through the firewall. On the regular Cup Cars( Not Supercup), the rollcage mounted back by the rear seats, at least that's how it is in Cecil's Cup car. That's what I plan on doing. Thanks for the heads up though.

Cheers, James

Thanks James,

Does anyone make a good semi-custom cage that you can weld in yourself and custom fit to your car?

Tim

Tim, Most cages I have seen need a little massaging to fit in anyway. Safety devices sells one that will fit your car. I don't think our host sells them?! On the East Coast you can try Stable Energies. They are located in New Jersey.

Cheers, James

Try this:

http://www.stable-energies.com/safdev/porsche.htm

I want more information on this as well. I want to know what is included/ not included in the kit, tube size, etc. I'll probably send them an e-mail this week-end.

I have the stable energies cage in my car. It fits pretty well for a prefab cage. You can weld it to the floor or bolt it to plates that you have welded to the floor. I had the plates welded to the floor after prefitting it and then put it in myself. The cage comes with everything you need. The only thing I would do is weld an under dash brace bar to it and possible add extra door bracing depending on how you would be using your car. I am very satisfied with the product.

Thanks for the posts and links gentlemen.

I have printed off details you have supplied, emailed some vendors, and will see what local welders might be able to do this too.

Cheers
Mark

When you guys talk about bolt-in / pre-fabricated roll cages, how exactly do you get it through the door of the car?!? Or when you buy one from a manufacturer do you then have to go and weld it yourself?

Mark,

What you need to do is make a sketch of the roll bar cage along with the location of the contact points to the frame of the car. Next you have to have height/width dimensions to go with it.

You could do a bolt in cage with metal plate flanges with bolt holes seeing that you have a rag top. That way, you could remove it when you are not on the track.

Get in touch with a welding shop that does pipe welding. They would be more familiar with what you want and help you design it.

As far as structrual integrety, a good welding shop knows what needs to be done, all you have to do is give them the info.

A couple other choices would be a metal fab shop, machine shop, sheet metal shop or a shop that installs hand rails.

Be sure you spec what size and thickness of pipe you want to use. The more info you give them, the better off you will be and the less likely you will be turned away.

Steve

"A Porsche does more then just go fast in a straight line"

I'm also considering the OG racing cage...can anyone comment on the OG cage vs. the Safety Devices cage?

The Stable Energies cage(s) seemed to be pretty competent.
* They used large diameter tubing.
* They tied it into the suspension mounts

* That doesn't really look like "kit", and it certainly does not look like a home installation type of product. Note that they took the roof off at least one of the cars in order to properly install the roof bar.
* Note that the roof bars are run as close as possible to the root.
* The mounting points are not just horizontal plates but are actually also welded to verticle surfaces. This puts a lot of the forces into shear rather then compression/tension.
* They've welded gussets from the cage to the different frame elements of the car's tub, such as the A,B&C pillars.
* In general, everything is well trianglated. The only exception was this curious feature on the 944 cage.

http://forums.pelicanparts.com/uploads/p27d-25.jpg

That possible may be a "work in process" since that piece would make a lot more sense if there were a couple of bars in a V above it going back up to the corners of the main hoop inplace of the X which is there. In the absense of the V, that piece is worthless since it provides little support against horizontal movement. Being joined in the middle of the span for the rear cross-piece effectively creates a hinge point in the cross piece which is pretty silly there.

Note that it is a good idea to drill small (1/16) holes into each of the bars so that you can take measurements to confirm the guage of the steel. Some groups (SCCA) require these inspection holes.

Errrrrrrrr....guys....just to rescue my thread.......

I'm looking for pictures and advice on a roll bar, not a cage.

Appreciate any input, but I am in the market for a simple bolt in bar for the track (10% of the cars use - ha... that may change!) that I can remove when cruising with the family.

I've been to a race prep. shop here today to get a quote. Should have it back in the next few days.

Any guys in Aussie Goldie area who know of any suppliers for roll bars. I'll be up there next week.

Thanks
Mark