Cunningham Sports Cars
1955 C-6R
Text by Kane Rogers

 
   
  The Cunningham team gathers for a group portrait, Le Mans 1955.  
             
 

Sticking with the existing fleet for the 1954 season, Cunningham prepared to introduce a new lightweight vehicle, designated C-6R, the following year. The new car was to answer the lessons learned in past campaigns: to begin with, it would be smaller, much lighter, and incorporate right-hand drive.

The person hired to design and build the C-6R race car was Herbert “Bud” Unger. Bud worked as a mechanic and metal worker on the C-4R and C-5R doing strictly bodywork. He spent about a winter working on the C-4R, then another winter working on the C-5R.

The cars Briggs had built were too heavy and too cumbersome, so in 1955 Briggs turned the whole design project over to Bud. Bud had a lot of design experience doing custom work so he told Bud that he wanted him to design a lightweight, low-slung, all-aluminum Sports Car. Briggs gave Bud complete liberty to do it the way he thought it was to be done.

Known as the Briggs Cunningham C-6R, Bud started the build by making a ¼ clay model. While designing the car, Bud was looking for an aerodynamic flow. Briggs wanted a lightweight, smooth-flowing car with a very low profile. Bud came up with the design for the car by combining the air intakes up front, the grille, the air inlets on each side of the grille, and the swept-in body. Briggs was experimenting with the brakes on the car, and he tried water-cooled brakes. The water-cooled brakes didn’t work very well, so while Bud was working on the body, Briggs told him to put some air scoops on the rear fenders and sweep the body in so he could pick up a lot of air.

After the clay model, Bud built a full-size wooden mock-up that he hammered and shaped aluminum over. They also had an English wheel, and a man from Europe that was an expert with the wheel. According to Bud, he rolled the top of the car so perfectly that they didn’t even have to grind or sand it. As Bud recalls, the car was less than 36” tall and the body shell weighed less than 200 lbs. From the clay model, to the mock-up, to the finished car, it took about 2 years. About 1956, Briggs Cunningham closed down, so Bud returned to Washington, D.C.

More information about Bud Unger can be located at the Collier Collection (www.revsinstitute.org).

(Credit for the information shared here about Bud Unger goes to Sondre Kvipt (sondre@kustomrama.com), who wrote an article about Bud and posted it on his website, www.kustomrama.com.)

That it was the first Cunningham racer built according to a full set of engineering drawings was reflected in its efficient packaging and elegant design. But the car also bore one glaring compromise, its use of a Mayer-Drake prepared Offenhauser four-cylinder engine rather than the Ferrari 375MM V-12 originally intended. The Offy was run first with Hilborn injection, then with Weber side-drafts which, with other changes, boosted output by 40HP to 260 at 6,000 rpm.

The chassis featured two triangular units extending from the front crossmember, reaching up to the cowl, then descending to meet the rear of the main frame. Front suspension consisted of unequal length A-arms and coil springs, and a Norden steering gear unit. The rear end once again used a De Dion layout incorporating inboard coil springs and brakes. Both tubular and Houdaille vane-type shock absorbers were used at all four corners.

Briggs and John Gordon Bennett first drove the unpainted car at Sebring in March 1955, dropping out when the flywheel disintegrated on the fifty-fourth lap.

The C-6R then appeared at Le Mans in June sporting a headrest/tailfin in the fashion of the D-Type Jaguars, and a smaller grille opening to aid the car’s aerodynamics. Cunningham and Sherwood Johnston drove the car to speeds of up to 141.32 mph, but were forced to go progressively more slowly until all but top gear in the transmission gave up. The extra load was too much for the Offy, which already had inherent overheating problems caused by the conversion from alcohol to gasoline; the engine eventually ate one of its pistons, and the car retired after eighteen hours in 13th place.

Certainly an even greater disappointment was that, as a consequence of witnessing the massive accident that took so many lives at Le Mans that weekend, the immensely talented Phil Walters decided on the spot that he was through with racing. Said Briggs years later, “I can’t say that I blame him.”

Briggs drove the car again at the Road America season-opener where the plucky Offy finally expired for good. The car sat dormant until 1957, when Alfred Momo installed a 3.8-litre Jaguar engine and transmission. Cunningham entered the car at Sebring and cracked a cylinder wall during practice. It later ran in a couple of SCCA events before being permanently retired, and is now in the Collier collection in Florida.

 
             
  SPECIFICATIONS  
 
             
Engine   Chassis
Cylinders   Offenhauser 4   Brakes   Hydraulic Drum
Bore   3.97 inches   Brake Dia. Front   13″
Stroke   3.63 inches   Rear   13″
Capacity   183 C.I.   Suspension: Front   Wishbone/Coil
Valves   Integral w/block   Rear   De Dion/Coil
Comp. Ratio   8:1   Shock Absorbers   Dual Hydraulic
Max. HP   270@6000 RPM   Wheel Type   Cast magnesium
Carburation   2 2-bbl Webers

      disc
Ignition   Lucas   Tire Size   7.00″x16″
Fuel Pump   Mechanical   Steering gear   Norden Racing
Fuel Capacity   50 Imp. Gal.   Steering Wheel   17″ Spring Spoke
Oil Filter   Full Flow        
Oil Capacity   7 Imp. Quarts   Dimensions
Water Capacity   25 Imp. Quarts   Wheelbase   100″
Electrical System   6 Volt   Track: Front/Rear   52″/52″
Battery Capacity   130 Amp/Hrs   Overall length   164″
        Overall Width   64″
Transmission   Overall Height   35″
Clutch   Single Dry Plate   Ground Clearance   4″
Gearbox   4 Spd synchro   Dry Weight   1900 Lbs.
Final Drive   3.36:1        
        Source:   Road Racing Specials, 2003
 
 
           
C-1 C-2R C-3 C-4R/C-4RK C-5R C-6R
           
 

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Credit to Kane Rogers for his important contributions to this website's creation.