Chapman the Circuit Judge sets out his bylaws

Chapman the Circuit Judge sets out his bylaws


Colin Chapman was a sophisticated and very creative engineer, inventor, and scientist.

His cars were both aesthetically and functional. The racing cars at various stages dominated F1.

It’s easy to forget the very first scientific principles that governed his design code.

Behind the complexity are the elementary laws of motion set out by Sir Isaac Newton over 300 years ago.

Many of Newton’s laws are adopted in aviation. Chapman borrowed these we know.

This article sets out in simple terms what Newton’s laws were and how Chapman rather obsessively and rigorously incorporated them in his car and racing car designs. This he did achieving considerable success at the highest level of motor sport.

Subscribers might like to see the directly relevant and integrated A&R pieces that complement and help structure this article:-

  • Lotus chassis design
  • Aerodynamics and drag
  • Lotus by Type numbers particularly Mk’s.III, Seven, VIII, 25, 79, Elise
  • May the force go with you

Newton’s laws of motion [edit] from wiki:-

“Main article: Newton’s laws of motion

The most important natural laws for structural engineering are Newton’s Laws of Motion

Newton’s first law states that everybody perseveres in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed.

Newton’s second law states that the rate of change of momentum of a body is proportional to the resultant force acting on the body and is in the same direction. Mathematically, F=ma (force = mass x acceleration).

Newton’s third law states that all forces occur in pairs, and these two forces are equal in magnitude and opposite in direction.

With these laws it is possible to understand the forces on a structure and how that structure will resist them. The Third Law requires that for a structure to be stable all the internal and external forces must be in equilibrium. This means that the sum of all internal and external forces on a free-body diagram must be zero:

Like the rest of Newton’s physics, the second law of motion holds up for a staggering array of everyday situations and is a workhorse in modern science and engineering. The way almost anything moves can be worked out using his laws of motion – how much force it will take to accelerate a train, whether a cannon ball will reach its target, how air and ocean currents move or whether a plane will fly are all applications of Newton’s second law. He even used the laws of motion, combined with his universal law of gravitation, to explain why planets move the

Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).”

Forces make things move or change e.g. concept of acceleration –going faster and as in:-

  • Speeding up
  • Slowing down
  • Changing direction

As applied by Chapman basically the bigger the force, the lighter the object, the greater the acceleration etc. also the lighter the object the easier the maneuverability.

Lightweight things need less force to move than heavy things.

“The second law: When a force is applied to a car, the change in motion is proportional to the force divided by the mass of the car. This law is expressed by the famous equation F = ma, where F is a force, m is the mass of the car, and a is the acceleration, or change in motion, of the car. A larger force causes quicker changes in motion, and a heavier car reacts more slowly to forces. Newton’s second law explains why quick cars are powerful and lightweight. The more F and the less m you have, the more a you can get.”

Figure 1.Mk.V111, Basic chassis, light by structural reductionism

Figure 2. Editor’s sketch of Lotus Mk.VIII -relate to power to weight ratio and aerodynamics to maximise opportunity

As Chapman might explain and use Newton’s Second Law:-

Forces make things move or change e.g. acceleration, going faster, speeding up, changing direction ……

The bigger the force [engine for example] the lighter the object [chassis/car] the greater the acceleration.

Lightweight things need less force to move than heavy things.

Which links to Chapman’s beneficial mantra of weight saving and the spiral or reducing weight downwards.

Small cars:-

  • Decelerate and stop quickly
  • Corner more easily
  • Use less fuel
  • Cheaper maintenance costs
  • Less polluting

Power to weight

Singh Reyat:-

“the performance of an automobile much depends upon its power to weight .By keeping the weight of the vechicle down to the minimum and installing engines of high bhp , the best performance can be achieved .the higher the effective bhp of the engine and the lower the total weigh of the vechicle , the better will be its hill climbing abilities , the higher maximum speed and better its acceleration .a well designed streamlined car having a high power to weight ratio registers a low fuel consumption at any given speed ………………….

In view of maximum speed, there should be the minimum of body resistance in addition to high power to weight ratio because the air resistance of an automobile body and chassis increases as the square of the speed whereas the power varies as the cube of speed ……………………”[see A&R Drag]

Power to weight is a very significant aspect of Chapman design philosophy and economics of car production.

Newtons 3rd law as applied aerodynamics

Singh Reyat:-

“wind or air resistance .This resistance depends upon the shape and size of the vechicle body , air velocity and speed of the vechicle .it increases as the square of vechicle speed owing to which much importance is given to streamlining and frontal area of the modern automobile .in calculating ……..

For the best streamlined cars coefficient of air resistance is 0.00235 for average cars 0.0032 and or buses and trucks 0.0046”

The third law: Every force on a car by another object, such as the ground, is matched by an equal and opposite force on the object by the car. When you apply the brakes, you cause the tyres to push forward against the ground, and the ground pushes back. As long as the tyres stay on the car, the ground pushing on them slows the car down.”

A car has to punch a hole through the air [that is providing resistance] as it goes forward. Resistance increases with speed .Its known as drag.

It can be appreciated drag saps energy slowing a car down. [Or a cyclist; note improvement with drop handle bars]

Streamlining of the car body shape helps reduce the drag.

Shape of the car body determines turbulence .Better design is one that overcomes or reduces drag and turbulence.

One of the early answers were body shapes that tended towards being tear dropped and often long, low and smooth.

In the modern era of FI [an of course studied and applied by Chapman] downforce and stability are the primary requirements of aerodynamics applications. Speed increases downforce.

A plane wing is used to push up; a F1 car wing aerofoil upside down bends air upwards;

Newton’s Third law identifies equal and opposite forces, pushing downwards which include suction and downforce.

Air is also channeled under the car ;as – Chapman discovered in ground effect –again applying an established scientific law , which due to air speed and differing pressures creates suction further increasing downforce.

Estimated downforce in modern F1 car:

35% rear wing

40% ground effect

25% front wing


All Chapman’s designs were driven by Newton’s laws including the microlights and boats. Chapman’s application of Newton’s Laws is maximisation and minimisation.

The earliest trials cars and Mk.III were incorporating both weight saving measures and elementary aerodynamics. Chapman and the Allen brothers adopted the discipline of the spring balance to weigh, control, reject and modify.

The Mk.VIII demonstrates how Chapman tried to push these principles to extreme.

Forced to adopt an engine less powerful [budget constraint, availability] than his competitors – [Porsche, OSAC and Maserati] he sought to maximise the advantage he could implement – through the chassis and body – even at a cost of practicality and servicing. These represented one of his purest if less practical designs.

The Seven demonstrates the incorporation of increasingly powerful engines as the accentuation of the maximisation end of the force equation.

Chapman moved away from the tube chassis to the monocoque. This was done in the interests of weight saving and rigidity. Our dedicated article on the types 25 and 33 provides the math’s of the rigidity.

Through the facilitation of the Cosworth DFV Chapman sought again to improve the power to weigh aspect of his cars within the Newton framework.

The Type 79 demonstrates Chapman and his team exploring the benefits of ground effect and related aerodynamic forces some of which are derived from Newton.

The Lotus Elise once again through its chassis proves conclusively the application of theoretical principles and the advantages of a lightweight car.

Chapman’s application of principles is practiced within the brand, the model sector and parameters. Ie form and function appropriate for defined purpose /role/customer requirements / expectation.

Learning Opportunities

Our learning /educational opportunities are intended to be challenging thought provoking and requiring additional research and/or analysis.

These opportunities are particularly designed for a museum/education centre location where visitors would be able to enjoy access to all the structured resources available in conjunction with any concurrent exhibition.

In this instance we suggest the following might be appropriate:-

Marque Model Engine BHP Weight cwt Power to Weight
AC Ace 2L 6 85 15
Aston Martin DB3S 6 180 18
Aston Martin DB2/4 6 140 23.5
Bentley Continental 6 n/a 33
Buckler 90 4 36 8.75
Bristol 405 6 105 23.75
Connaught 1.5L 4 110 11
Cooper Bristol 6 135 11.25
Cooper Jaguar 6 225 appx n/a
Dellow Mk.II 4 31 11.5
Frazer Nash 6 140 15.5
HWM-Jaguar 6 250 18.5
Kieft “1100” 4 72 18.5
Jaguar XK140 6 190 22
Jaguar D Type 6 250 n/a
Loenard MG 4 85 appx 10.5
Lister-Bristol 6 135 12
Lotus Mk.VIII MG 4 85 appx 8.5
Lotus Mk.VI. Ford 4 40 appx 8.5
Morgan Plus 4 4 90 16
Triumph TR2 4 90 17.34
  • Using above tabulation calculate power to weight ratio for each car?
  • What pattern emerges if any?
  • Identify scientific laws or principles, which are used in automobile design?
  • What calculations are used to measure air resistance?
  • Which of Newton’s laws apply most to automobile or F1 design?
  • What are G forces
  • How is Newton’s law applied to car /driver /passenger safety?

Figure 3. Basic conception of monocoque chassis: essentially aluminium tube with steel bulkheads at critical location points

Exhibitions, Education, Economics and Entertainment

In the museum context the editors believe that commercial considerations are both necessary and complementary with its educational objectives.

For these reasons our suggested outline Business Plan includes provision for promoting products and services which share Chapman’s ideals of mechanical efficiency and sustainability. In addition we propose merchandising that explain and interprets the social and cultural context of Chapman’s designs in period. It’s suggested there will be catalogue for on line purchasing.

In this instance we suggest the following might be appropriate:-

  • Rule of Law: Measurement
  • Chapman’s Maxims
  • Newton’s Laws and Chapman’s Enforcement
  • Rules and Regulations :Chapman Interpreting the F1 rules
  • Scientific Laws

Figure 4.EDITORS sketch of type 79- note aerod’ principles; see dedicated article for fuller explanations

Conclusion: Bound by the Law

Chapman was an engineer/scientist.

He accepted the discipline of Newton’s laws of motion.

These were also adopted in structural thought and aviation principles.

He applied Newton’s laws to great effect through the course of his career.

He applied them in road/ racing cars, boats and microlights.

However, when it comes to the governing rules of the sport Chapman’s mind was sharp and incisive. He examined and interpreted the law to provide advantage. Some might have thought he stepped outside the spirit of the law but with a judicial diligence he explored avenues that were available. He possibly believed the responsibility was with those that wrote the laws and they were subject to his creative interpretation. Which is possibly what the legal system is about.

We need not expand at length; possibly the one quotation from Chapman that encompasses the science discussed is:-

“Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere.”


Sports Cars.Douglas.Ian Allan.

The Automobile. Singh Reyat.Chand.2011.

ISBN: 8121902142

Please note the editors of the A&R attempt to give the broadest spectrum of references but not all are available for consultation in an article. However by noting their existence it may assist students in their research.

*Items in italics non A&R library books.