Tip: Planning and Fabricating a Rollcage for your Race Car

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Now sporting a rollcage, fabricated by Cruven Fariview and as of press time, painted in Prima Water Works blue, our Project Elantra has drawn much query from our competitors and friends in the races. Surely they have it in their minds that modifying an Elantra to such an extent is either a quixotic quest or an engineering marvel. So possibly, when people asked rollcage design advice from me, they may have the optimistic thought that I have some authority in the matter. I most certainly have very little.

But then again, I had my hand in doing one. Well, sort of. I researched what was needed to be done and had the wonderfully inventive folks at Cruven Fairview do the rest. Regardless, the same disclaimer applies to every Tip article we come up with. Caveat lector.

Anywho, here are my thoughts on the matter.

Image credit: http://www.autopowerindustries.com

1. Understand the true purpose of a rollcage

No, a rollcage is not a show car accessory. No, it’s not to strengthen the chassis – that is merely a secondary function. The rollcage is descended from the rollbar, the structure in the cockpit responsible for bracing the load of a rollover incident, preventing the roof collapsing on you. The rollcage extends the rollbar’s functionality with the addition of additional members to bolster the rollbar, side beams to protect the occupants from T-bone collisions, and so on. If you are not racing your car, you don’t need it, so don’t put one.

2. Know what your motorsport series requires in a rollcage

If you’re a participant in the higher echelons of Philippine production-car based motorsport, then you already know that you need an FIA-spec rollcage to be scrutinized by a qualified representative of the event organizer. And by extension, you should already know how to build such a cage (or can afford paying someone known in the industry for building quality cages like Dax Santiano to fabricate one for you), and thus not need to read this article any further.

If you are gunning for a specific amateur motorsport championship, then read the rules of that series and seek the advice of that series’ technical steward.

If you’re like me, an amateur motorsports participant with no distinct championship series to gun for, you have to meet the minimum requirements of the most stringent series you plan to participate. We envisioned Project Elantra to run in circuit races, so we thought that making a rollcage following FIA-recommended specifications was the least we had to do. But apparently Circuit Showdown only requires a minimum 4-pt cage and are silent on specifics on construction, materials, and so on. Plus, we had Mr. Oski Nuke of Race Motorsports Club check our handiwork. He noted that our cage was way, way overbuilt for slalom racing.

Like what my mother says, okay lang ang sobra, basta hindi kulang.

3. Find a design and specification that meets your needs

After doing your research (you did already bug Enzo Pastor/Danny Santiago/Bing-Bang Dulce, right?) now’s the time to plagiarize get inspiration from the multitude of people having their fabrications posted online and from the handful of locals determined enough to have some scaffolding installed inside.

We consulted the FIA Safety Equipment regulations (Article 253-2013) for internationally recommended specifications on rollcage construction, among other safety considerations. It’s great bathroom reading, fantastic when constipated.

In addition, we found a more legible guideline from an amateur endurance racing series in the US, the 24 Hours of LeMons (this is inspired and distinct from that other endurance race in France). The How Not to Fail LeMons Safety Inspection guide was very understandable and downright humorous.

These two made up the bulk of our resource material for our rollcage design. Insert disclaimer here.

4. Note these particulars in constructing a rollcage

Use Seamless Pipe – In other countries, this construction of pipe is called Drawn-over Mandrel (DOM). It took us a long time to figure out that it was called “seamless pipe” in the Philippines. Seamless pipe is made in such a way that the entire pipe is one solid piece, as compared to the typical Electric Resistance Welded (ERW) pipe where it starts out as a sheet of metal and just curved into a pipe shape. ERW pipe has a visible seam when you look at the inside, so you know that it didn’t start off as one piece of metal. We got some supply of seamless from Ambassador International in Cubao, Quezon City. Metal wholesalers usually require you to buy a butt-load of pipe, but Ambassador was able to supply us four 20-ft sections with free delivery to Cruven Fairview.

Bending seamless pipe will be a PITA, but Sch. 20-thick pipe will be much easier to bend than the super-thick Sch. 40 we used. 1½” piping is the diameter you want to go with for most purposes. We went 2” on the main hoop because that’s what the FIA said, but apparently that’s too much according to the technical stewards we’ve consulted. Our pipes are Sch. 40, which is 50% beyond FIA spec because we misread the thickness requirements. Don’t emulate, as we made an overweight car even heavier. Get Sch. 20 pipe.
If you don’t give two hoots about FIA, use exhaust pipe – We were given to understand from a wizened slalom racer that thin-gauge exhaust pipe will be strong enough to sustain one rollover event, be rigid enough to strengthen the chassis, and not be too heavy to diminish acceleration. Before you scoff at this, which I kind of did when first hearing about it, do note that due to its cylindrical construction  pipe is not much weaker on compressive loading than if it were one solid piece of steel. Insert another disclaimer here.

But this depends on the regulation applicable to you. Don’t use exhaust pipe if the rules dictate a minimum wall thickness for the rollcage.

Avoid fabricating these types of front hoops/stays. (Image credit: http://www.jdmrides.ca)

Don’t put extra bends on front hoop/front down bars – A common mistake by even established racing teams and tuning shops is to curve the front hoops in such a way that it artfully avoids the dashboard. That action weakens that section of the rollcage. Instead of the upper windshield portion being strong enough to sustain one or even several rollovers, that section may crush in, killing you dead.

Keeping the number of bends to a bare minimum in this segment of the cage is the optimum. As much as possible, let the front down bars follow the A-pillar down until the bottom of the glass, then bend it to vertical to the floor.

If you don’t want to molest the dash, rather don’t put a front hoop. Keep the rollcage to a four-point design. Or better yet, don’t put a rollcage.

Rollcages can be made so that they are easily disassembled – In a race car such as Project Elantra, ease of rollcage disassembly is not of importance. There are no removable members to speak of. In fact, in removing our dashboard we had to hack off one of the front hoops to facilitate its egress.

For a car with track aspirations but with required steetability, you may opt for some removable members so that you can still commute about without your significant other filling your ears with shrill vowels and consonants. The FIA Safety regs in page 14 lays down some schematics on the proper design of such removable members.

Note the front stay/hoop joined to the body via die-punched flat bars, providing extra rigidity. (Image credit: www.pistonheads.com)

Brace the rollcage to as many parts of the body as possible – FIA requires mounting the rollcage only where the cage’s posts meet the flooring. There is additional chassis rigidity to be gained when the rollcage is tied to other structural points of the unibody. Some designs tie the front hoops to the front shock tower and A-pillar, the main bar with the B-pillar, longitudinal member between the backstays to act as a rear strut tower bar, and so on. The more points you tie to the chassis, the stiffer the car is, complimenting full-effort suspension tuning. But again, if the car won’t be a dedicated race car, you wouldn’t be able to tie as much of the rollcage to the body as possible as you have to clear interior trim and the kawali that’s gonna fly towards your cranium.

5. Find a decent fabricator

I’m assuming that you can’t weld for the life of you. I sure can’t. This is why we were blessed to be in the good hands of Cruven Suspension Specialist – Fairview branch for the fabrication of our Project’s rollcage. More than just a suspension shop, speed freaks of the Novaliches area know where to flock when they need to have some control in their testosterone-filled rides. Got an SUV whose body you need to lift? Two words: Cruven Fairview. Need a rollcage? Cruven Fairview.

 

Contacts:

AMBASSADOR INTERNATIONAL
48 7th Avenue, Quezon City, Metro Manila
Phone: +63(2)9132701

Cruven Fairview (EVSI-IBA)
Blk 157 Lot 34 Commonwealth Ave. corner Mindanao Ave. Greater Lagro Fairview. QC
Tel No. 332-2998 & 377-3044
Mobile: 0922-8279041

 

Any problems with this tip?

If you wish to add to this article, or find info that is grossly incorrect, please do comment away.

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