Just because the replica Cobra market was already well-established when Dave and Mark Smith entered it in 1995 didn't necessarily mean it couldn't be better.
It's not to say that Cobra replicas at the time were duds-they weren't. Though fiberglass bodied, most were actually pretty faithful to the original concept. In fact, their performance was largely on par with their forebearers.
And that's exactly what the brothers took issue with.Once the production-car world caught up with the roadster's performance-and by 1995 it certainly had-the Cobra's selling points were its prestige and its ability to accelerate the blood to the back of its occupants' heads. Since they didn't have the former, the garden-variety Cobra replica looked pretty one-dimensional to a sports-car enthusiast. Dave and Mark were sports-car enthusiasts. To make their mark on the performance Cobra world, they had to do things differently.
Even though the chassis narrows...
Even though the chassis narrows to accommodate the doors, note how great the chassis cross section is in comparison to a conventional box-section framerail. Also note how low the design places the floor. Hallmarks of good design include single components that serve multiple functions. The pedal assembly, for example, locates the steering column. Materials use is critical, too: while fiberglass is very strong, steel is more capable of bearing the hinge and latch loads without fatiguing. All of these objectives make a car both stronger and lighter.
Released under the Factory Five Racing banner, their Cobra replica entry was more than just a clone of an existing copy. A stiff, hybridized space frame distinguished it from its Cobra replica peers, but it was the suspension and drivetrain components that the brothers designed the chassis to accept that made it truly exceptional. By that point the '87-93 Ford Mustang populated boneyards enough to make it affordable. And even though the garden-variety Five-Oh was no slouch around a track in stock form, when its components were reconfigured in a package that had a lower center of gravity and weighed a thousand pounds less, they made things that resembled Cobras accelerate laterally just as well as they did in a straight line.
Banking on their new car's performance, the brothers' car found immediate success among both street enthusiasts and racers who competed in various vintage and replica sports-car events. Inspired by Tim Suddard's comment in Grassroots Motorsport magazine that the car would make a great vintage-style spec racer, the brothers established the Factory Five Challenge Series, a group of regional points-driven events where the company's customers could pit their cars against one another in legitimate race action on legendary racetracks.
And race they did. Even though Factory Five has produced more than 200 racing-specific spec cars in the meantime, more than 250 out of the 7,000-plus garden-variety and race-spec Cobra replicas that the company has delivered participated last year alone. In light of that, the fact that a Factory Five car is a fully roadworthy car easily within reach of the average enthusiast in both cost and construction almost seems insignificant.
But it's not. The Brothers Smith recently leveled their sights on the hot rod and street rod market. Needless to say, they saw room for improvements.
First, Make It Perform
"I didn't originally want to do this car," Dave Smith admitted. "I'd put under the definition of hot rod the clause 'a car that goes really fast...mostly in a straight line.' But for me if it ends there, I'm not interested in it. I need more than going straight."
The '33's chassis is more...
The '33's chassis is more than just a frame; it's basically a truss as long, wide, and high as the car. Note how the tubes meet headlong at junctions. It's because a tube is considerably stronger in tension or compression than it is in shear. Also note how each tube meets more than one other. Arranging them that way causes force applied to any single tube to dissipate among many others. The design has an incredible amount of structural integrity, and while it looks massive, it is very light on account of relatively thin tubing walls.
In fact, neither he nor his brother Mark would have even indulged the thought if it hadn't been for one person: Jim Schenck, head of Factory Five Racing's R&D department. "Jim came to me and said, 'Dave, I can make (a hot rod) handle better than the spec car,'" he said. "That was the charter," Dave added. "I told him 'Don't waste your time if you can't make the car perform better than what we're making right now.'"
In development, the project earned the '33 Hot Rod moniker. Thirty-three since it resembles Ford's first-year Model 40; Hot Rod since it's a car that can trace its performance heritage all the way back to legendary sport car/hot rod hybrids like Max Balchowsky's Buick-powered Deuce, Ak Miller's Caballo, and Duffy Livingstone's Eliminator, just to name an esteemed few.
Since chassis design is the backbone of the company's philosophy, development started there. Though identical in theory to the Cobra replica, the chassis Jim and the R&D crew developed is unique to the hot rod program. "Remember, with the Cobra you're a slave to the original design," Dave observed, a reference to the hallmark 4-inch-diameter tubes in the ladder frame that define a Cobra as the real deal-even if it's a copy. "That's what those customers want." Instead, Factory Five Racing engineers dispensed with any existing chassis design entirely and fabricated for the '33 a true space frame.
The front suspension cannot...
The front suspension cannot trace its lineage to anything; it's a clean-sheet design with roll centers optimized specifically for the '33's center of gravity. Relocating the engine rearward improved the car's balance primarily, but it gave the engineers greater packaging latitude. For example, the upper control arms are actually cantilevers that link to coil-sprung Koni mono-tube dampers between the radiator and engine. Adjustments on the lower arms determine camber and caster since the upper arms rotate upon fixed pivots. Though not visible here, the design employs a rack-and-pinion steering gear (an electric-assist system is available as an option).
Rather than simple girth and heft, a space frame employs materials in their most efficient ways. For example, doubling the cross section of a frame section doesn't just double its capacity in that direction; it quadruples it. For context, the original Ford frame measures about 5 inches tall. In the Factory Five Racing design, it measures 10.5 inches tall at its least cross section under the doors.
What's more, instead of making the side 'rails from a simple piece of heavy-walled box tubing, the Factory Five engineers employed smaller, thin-wall tubing and arranged them by girder design principles. In a nutshell, the triangulated arrangement stresses the individual tubes in their strongest direction: in tension or compression. Even though the walls aren't as thick, the horizontal cross section isn't as great, and the design isn't solid-walled, the truss design is fantastically stronger and lighter than a conventional piece of boxed tubing of similar dimensions.
And those design principles go beyond the side 'rails, too. In fact, from the leading control arm pivot to the rear spring mount, the entire '33 chassis is a space frame design not unlike a skyscraper crane. By testing the design in Finite Element Analysis applications, the Factory Five engineers were able to arrange the individual tubes so a load applied to it dissipates consistently throughout the chassis. While the Cobra's shorter length would technically make it stronger, by virtue of this uncompromised design the Hot Rod's chassis is both stronger and lighter.
Unobstructed by conventional crossmembers, Factory Five engineers designed the car to accommodate any drivetrain package, whether Flathead, pushrod, or overhead-cam Ford, early or late Mopar Hemi-even a Chevrolet. Furthermore, it let the designers slide the engine rearward to improve the car's balance without overly compromising the cockpit. Similar transmission accommodations exist, but we suggest installing one that requires three pedals. To use one that requires any less would be to miss the point of this car.
By moving the springs inboard,...
By moving the springs inboard, Factory Five Racing's engineers were able to keep the car's mass as close to its centerline as possible. While this improves handling marginally, it does wonders for the suspension's looks. The '33 includes brand-new spindles, hubs, front brakes, and brake lines as standard equipment.
More than just a structure for the chassis and engine, the chassis serves as the pickup point for every body component in the car. "One of the features that I like is that our doors, our hood, and our trunk are frame-mounted," Dave revealed. "So when you're slamming the door, you're slamming against striker plates that are mounted to the frame. The hinges are hinging on the frame." But more on that later-we're getting ahead of ourselves.
"With the hot rod, we decided instead of going Mustang II or some original style frontend, we went full-on modern," Dave enthused. It's a clean-sheet design with optimized roll centers and enough adjustment in its lower control arms to suit any type of surface condition or driving style, whether on the road or at the track. Due to the car's overachieving handling properties, most of us will naturally pick one and never miss the other options.
Moving the engine rearward to improve weight bias had a fortunate consequence: it created a cavity behind the grille that the engineers graciously filled with springs and high-pressure Koni mono-tube coilover dampers. More than merely spindle-locating devices, the upper control arms serve double duty as cantilevers.