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.
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.
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).
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."
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.
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.
"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.
The rear axle is not included in the '33 package; however, the chassis accepts either the Ford 8.8 rear axle from the Mustang or a 9-inch that's been modified for Mustang control arm mounts. Factory Five offers two rear suspensions systems: a standard four-link for the corner carvers or the race proven three-link derivative optional on the roadster. "It's the three-link from our racing series..." Dave noted, "...the geometry is the same."
As dramatic an improvement as the suspension systems may be, a key to the car's turn-in manners and ride quality is due in part to the gap between them. "The wheelbase is a little longer (than the Cobra roadster)," Dave noted. For the record, he's being conservative: "a little longer" translates to 22 inches, or about a quarter of the Cobra's wheelbase.
Remember the tangent about the body components bolting exclusively to the chassis? Though the comprehensive interior panels suggest otherwise, it's not a body in the conventional sense. "The body is just a shell," Dave said. "Nothing bolts to the fiberglass; the body's little more than a fairing. You can actually drive the car without the body."
But just because it's a shell doesn't mean it's crude. Factory Five Racing hand-lays every one of its body panels. "There's not a chopper-gun in the entire building," Dave proclaimed. "It's three layers of two-ounce mat and a layer of bi-directional cloth, a finishing cloth that has a tight weave that looks real nice. We're using vinylester (binding resin) with a deformation temperature of about 218 degrees. That's really high-a guy in Arizona can paint his car black, and it won't go all wavy. We're also doing between 12 to 20 mils of gel coat, so it'll be a sandable finish.
"Overall, it's about 3/16-inch thick when it's cured and rolled out," he observed. "I think it's thicker than it needs to be, but there's this perception that fiberglass has to be thick for it to be strong. It's frustrating because 1/8-inch is a lot stronger than people think-plenty strong even if the doors and trunk hinged on the body."
Though the doors are full height, it's only to preserve the body lines. Since the door openings are about 1/3 shallower on account of the taller side members, a vertical panel extends from the actual door jambs to where the rocker panel would be on a real '33 Ford.
Rather than part of the body, the floors are stiff aluminum panels that are bonded and riveted directly to the chassis. Once shrouded in carpet, they're indistinguishable from conventional body floors.
 By moving the springs inboard,...  By moving the springs inboard, Factory Five Racing's engineers 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.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. |  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 frame rail. 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. |  The base package includes...  The base package includes the four-link rear suspension, but a three-link setup (shown) is available as an option. Though the illustration doesn't show the Panhard bar, its chassis end mounts to the rearmost tip of the triangulated structure on the driver's side and connects to a bracket on the axle's passenger side. Like the front, the rear suspension features Koni coil-sprung dampers. While not touched upon earlier, the oversized piston in the mono-tube design offers greater working area for more sophisticated digressive-rate damping. The design can also withstand greater gas pressure than a conventional twin-tube design can handle, giving the units even greater ability to suppress heat-induced cavitation that otherwise diminish a damper's effectiveness. Though 60 years old, it's still the baseline design for contemporary dampers. |