THE HISTORY OF SHADOW MK1
by Harm Lagaaij
The 1966-1974 Canadian American Challenge (Can-Am) has gone into history as the only no-regulation racing series. Designers were invited to really push the limits of physics. This resulted in some of the most powerful and unusual racing cars ever constructed.
Due to some cars becoming technically highly complex, incredibly powerful and expensive, the governing body was, unfortunately, forced to introduce, step-by-step, restrictions onto aerodynamics and engine power towards the end of the series.
The seasons that really bristled with innovation were 1970 and 1971 with the introduction of the Chaparral 2J “Sucker Car”, the quadruple engined Hoare “Mac ‘it Special”, the Porsche 917/10+/30 and the Shadow Mk 1. This last car could very well be the most unusual race car to have been designed.
The story of the Shadow Mk 1 started in 1968, when Don Nichols moved to California and founded Advanced Vehicle Systems (AVS). The former military Intelligence officer had already worked in motorsport as a supplier of parts and tires and race promoter in Japan. The cars were named "Shadow", no doubt a reflection of the owner’s affinity to the character from the comic series “The Shadow” from the thirties. He himself however often said that the inspiration for the name was because it was so small that it was almost two-dimensional and therefore not bigger than its "Shadow".
That year he met freelance designer Trevor Harris, who had mastered the skill to think outside of the box. His latest idea was to install a big-block V8 engine into the smallest possible chassis imaginable.
Nichols was impressed by the idea and commissioned Harris to make a full size model.
With this idea Harris tried to reduce the frontal area by approximately 35% in comparison to normal Can-Am cars. This meant that the package had to be completely different to achieve this.
Through his connections with Firestone, Nichols had 10 inch front and 12 inch rear racing tires made, which were 11 inch wide in the front and 16 inch in the rear. They were designed to withstand well over the theoretical top speed of 250 mph.
Another unusual feature was the twin water/oil radiators placed behind the rear wheels to make everything as low as possible.
Because of these height limitations, there was no room for conventional springs and dampers so Harris fitted three small springs at each corner, operated by rocker arms and for damping he installed compact friction dampers.
Other innovations were:
- Airbrakes by means of movable flaps.
- Centrifugal brake cooling fans on the front wheels.
- Slimline Induction system.
- Extreme lay-down driver position.
- Two horizontal pedals: brake pedal left, throttle pedal right. Clutch by hand lever.
- Cable operated gear linkage.
- Modular chassis sections for easier dismantling.
The exceptionally low chassis was tightly wrapped in a fiberglass body painted in black.
The most conventional parts of the car were the aluminium monocoque (anodized black for additional strength), the big-block V8 engine and the Hewland gearbox.
The front brakes were, because of the 10 inch wheels, small, but the inboard rear brakes were as big as possible.
Initially, to increase braking performance, Harris designed 3 movable airbrake systems in the original concept. Two vertical flaps in the front, two flaps on each side on the rear (integrated into the side air scoops) and one horizontal in the rear section. These would have been activated by brake pedal pressure.
Unfortunately, shortly before the first car was being built, a change in the regulations outlawed all movable aerodynamic aids, so these airbrake systems were never finalized.
When the first prototype was finished it caused quite a stir when it appeared on the cover of Road and Track in August of 1969 (see photo below).
Despite not being able to integrate the movable airbrake flap system, Nichols pressed on and started making more additional identical cars! A later chassis was made in 1990 for a museum. See letter from Don Nichols from March 2011 shown on the home page.
FIRST TRACK TESTS :
Because first engine bench testing had shown that the "Slimline" Induction system was obstructing the necessary engine power, a normal Hilborn/Kinsler “constant flow” fuel injection system with conventional ramtubes was fitted.
In the end of 1969 and the beginning of 1970 the first track tests were made at Riverside and Laguna Seca with Parnelli Jones and George Follmer. Thereby the cockpit shrouding was changed, the horizontal steering wheel was made upright and in Laguna Seca a high mounted rear wing was fitted (see all photos below).
SUMMARY TRACK TESTS AND RACES :
Due to lack of time and aerodynamic experience, the team could not resolve the cooling problems which occured during the track tests. Some unusual and counterproductive modifications were made for the 3 races: Mosport Park (photo 1) and St.Jovite (photo 2),both with George Follmer driving and Mid-Ohio (photo 3) with Vic Elford.
Unfortunately these iterations deviated strongly from the original aerodynamic and technical configuration.
Even though the Shadow Mk 1 did quite well in practice, it still had to retire with overheating in these races.
The next chapter "THE SECOND CAREER" will however show that the original cooling lay-out and the brake cooling could have worked in period w/o changing the original bodywork and radiator position, if the team would have taken more care of the airflow ducting to and through the originally rear placed radiators and if they would have always closed the rear wheel openings with the original "spats" ! Also the front brake cooling could have been highly improved if the air-ducting to the ventilated discs would have been better.
Due to lack of time and aerodynamic experience, the team could not resolve the cooling problems which occured during the track tests. Some unusual and counterproductive modifications were made for the 3 races: Mosport Park (photo 1) and St.Jovite (photo 2),both with George Follmer driving and Mid-Ohio (photo 3) with Vic Elford.
Unfortunately these iterations deviated strongly from the original aerodynamic and technical configuration.
Even though the Shadow Mk 1 did quite well in practice, it still had to retire with overheating in these races.
The next chapter "THE SECOND CAREER" will however show that the original cooling lay-out and the brake cooling could have worked in period w/o changing the original bodywork and radiator position, if the team would have taken more care of the airflow ducting to and through the originally rear placed radiators and if they would have always closed the rear wheel openings with the original "spats" ! Also the front brake cooling could have been highly improved if the air-ducting to the ventilated discs would have been better.