09

 
Built entirely in-house, the roll-cage shows that COBB has grown quite a bit in the last decade.  The cage is very well constructed, with care and time taken to ensure proper mitering on all joints.  The small details that often set the men from the boys when constructing a rollcage are apparent everywhere in the car.  Tubes all meet near each other to prevent failure of the main hoop, despite the added complexity of notching for multiple tubes.


COBB Tuning 2012 Ford Focus Roll Cage Tube junction


The door opening areas have been reinforced to protect against rollover and vehicle intrusion with triangulating bars reinforcing the front and back sections of each forward leg.

 

COBB Tuning 2012 Ford Focus Roll Cage reinforcement



COBB Tuning 2012 Ford Focus Roll Cage Details


Again, the devil is in the details with roll-cage fabrication.  When contracting out a rollcage, it's always best to stop by the fabrication shop often to ensure things are going as planned, as well as make sure the driver will fit with proper clearance in the seat before everything becomes permanent.  Small things like cleaning up tube ends where welding will occur is also a good thing to check on.


COBB Tuning 2012 Ford Focus TIG Welding cleanup x-brace


Since mild steel is coated in oil to prevent corrosion, each tube must be cleaned and any corrosion must be ground off to ensure the strongest weld.  This is especially true with TIG welding, since it is extremely difficult to weld dirty metal without contaminating the tungsten rod in the welding torch.

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Comments
Lester
Lesterlink
Tuesday, April 10, 2012 8:47 AM
This is cool on many fronts and nice to see both Ford and Cobb branching out.
bigBcraig
bigBcraiglink
Tuesday, April 10, 2012 11:37 AM
I have been working suspension and chassis on the GT FSAE team pretty seriously for a year... I know I'm very far from an expert but that cage doesn't look great to me.

There are many parts where it looks like, with a little more planning, there could be distinct nodes and clean load paths instead of putting tubes into bending in the case of collision or rollover.

Can someone more knowledgeable chime in on this Clearly the welds are beautiful and the main hoops fit the body very well, but the design still looks off.
Rockwood
Rockwoodlink
Tuesday, April 10, 2012 12:19 PM
There are a lot of constraints that don't pan out well in the photos. For example, the cross bar and x-brace can't meet at the same point because you need the cross bar at a certain elevation to properly locate the should harnesses. The x-brace itself can't be too high to meet it, or you run the risk of intrusion from a side impact and impede on driver egress. The forward legs can't go as far forward to mitigate this because of the way the Ford chassis is designed (you'll see cutout structures in the firewall that don't allow the legs to meet the firewall). Moving the triangulating brace in the rear would put that bar in the driver's shoulder.

They also had to maintain room for some of the interior panels, and I'm sure they needed to make it all present well.

Is it a perfect cage when you punch it into FEA? Nope. However, it's pretty good considering the design constraints. All of the tubes that had a lot of choice in locations were located perfectly, those that don't were compromised in their location. The rules for the series it will run in, and the design of the mass-produced chassis make limitations in design. Making room for the driver is often the overriding consideration, not pure strength. A cage that is designed so that the driver's head or limbs smack into it in relatively minor collisions doesn't do much for his safety. Keep in mind that this is not a blank slate FSAE car, this is a production car turned racer.

In the end, the method of construction, attention to detail during assembly, choice in materials, and overkill number of supporting bars would make this a very survivable cage, as well as improve chassis rigidity enough to easily handle the expected loads it will see. If this cage were to fail, I'd question the driver's chances of survivability anyway.
Wes Dumalski
Wes Dumalskilink
Tuesday, April 10, 2012 1:02 PM
If all cages were structurally perfect all cars would be tube chassis'. While I cannot say ANY cage is perfect whether or not it is perfect is decided by the need to use it. Let us all hope it does what it is supposed to do in the event it is called upon.
bigBcraig
bigBcraiglink
Tuesday, April 10, 2012 1:13 PM
Thanks for the explanation.

I definitely didn't mean to insult anyone, but was looking for insight as to what constraints affected the geometry. Specifically the x-brace / harness bar makes a lot of sense.

Mike Kojima
Mike Kojimalink
Tuesday, April 10, 2012 2:09 PM
The design is not that off, for sedans the cage is built around the car not vice versa.
Der Bruce
Der Brucelink
Tuesday, April 10, 2012 8:24 PM
Nice scoop Steve! It'd be weird to see someone other than Clint driving a Time Attack Focus...
Rockwood
Rockwoodlink
Wednesday, April 11, 2012 9:32 AM
@ bigBcraig: No offense taken... At least, once I re-read your post... ;-p
Discotea
Discotealink
Friday, April 13, 2012 4:33 AM
What is the difference between "1.75" x 0.120" DOM mild steel tubing, thicker than the required 1.75" x 0.120" DOM"
Am i missing something or is DOM Mild steel different than DOM?
Rockwood
Rockwoodlink
Friday, April 13, 2012 8:11 AM
Dammit! :)

Required is 1.75" x 0.090" wall. I'll edit that, thanks for pointing it out!
91z
91zlink
Friday, April 13, 2012 10:07 AM
OO, looks like they kept the cup holders too! Good thing, I like my Big Gulp during a race.

Great article as always!
Clint Boisdeau
Clint Boisdeaulink
Friday, April 13, 2012 1:19 PM
nice wing placement :D
Mark F
Mark Flink
Thursday, February 05, 2015 11:06 AM
Its a Cosworth Omega series dash. The EC Pro is the PnP ECUs for certain EVO and Subarus based on the SQ ECU platform.

The reference to the MFD is correct. Just wanted to let ya know.

Nice article and nice Focus COBB.

Cheers.
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