“What a drag it is ………..”*
Drag forms part of the vocabulary that relates to aerodynamics.
We know that Chapman took a holistic view of aerodynamics and adopted it extensively where it counted in his cars that could easily exceed 110mph.
In this article we examine drag and its related dimensions briefly using published data to reinforce the decisions that Chapman took and designs /body shapes derived.
Comparable statistics are useful in the Chapman context.
Aerodynamic package can also be seen in the horses for courses performance, cost effective parameters of product. It ought to be remembered too that customers have needs and preferences and hence why the Caterham remains perennial.
There is also an opportunity to comprehend aerodynamics in aesthetic context and that of sustainability.
The math’s of this piece sits readily with that explained in our piece devoted to Chapman and Newton’s Laws.
In future articles we will take a more in-depth analysis and introduce some experiments that can be undertaken that help interpret the complex subject of aerodynamics. In the meanwhile, cycle into the wind in upright position!!
Subscribers might like to see the directly relevant and integrated A&R pieces that complement and help structure this article:-
- Lotus Mk.V111
- Lotus 79 and Ground effect
- Lotus Seven series including Mk.4
- Chapman and Newton’s Laws
- Chapman and Aviation
“Chapman’s influence, or Chapman inspired influence, as far as aerodynamics is concerned is extensive and varied.He was, as he was in any other field, a follower and improver on the ideas of others, as well as the creator of new ones .He turned his attention to such major matters as the overall airflow round a car and the development of ground effect vehicles as well as relatively minor points such as radiator ducting. As with all things, Chapman’s attitude was to pay attention to detail.He never let go a point of design until it was as perfect as he was able to make it.
With his earlier cars, because their speed capabilities was low, the importance of drag reduction of the body was also low.
Chapman, with his aerodynamic background and engineers training understood very clearly the effects of airflow on his creations: for any car, the total resistance that has to be overcome by the engine consists of two main parts-the air resistance and the rolling resistance.
The air resistance [the force with which the air resists the cars passage] increases with the square of the speed………..
The table gives some values for a typical vehicle.notice that at low speed the power needed to overcome friction is the major force, whereas at higher speeds it is air resistance that dominates ….”
|power absorbed by||power absorbed by||total power|
|Speed||rolling resistance||air resistance||required|
The above statistics help explain the facts below. The Lotus models used as essential dual use and that: –
- Were relatively low powered
- Were inexpensive to construct and maintain
- Competed at Clubman level
- Constructed to formula directions
- Placed emphasis on handling that gave an added value to compensate for lower powered engines
For these reasons the Mk.VI, and Seven were open wheel cars with a higher drag factor. Subsequent machines entering at International level and racing at higher speeds towards 120mph and above adopted the more expensive, heavier and complex all-embracing streamlined bodies where advantages outweighed disadvantage.
|Marque||Model||Est ‘front’||Max.power||max speed||Est ‘drag|
|Aston Martin||DBS V8||20.8||1.93||345||155||0.41|
|Chev’ Corvette||Sting Ray||18.2||1.69||340||146||0.5|
|Ferrari 308||GT4 2+2||17.5||1.63||255||152||0.38|
|Lotus||Seven S4 SE||11.7||1.09||84||100||0.74|
Statistics from Campbell. [With qualifications].Note comparison with mid engine wedge shaped Esprit.
“For the older sports car and particularly for cars with separate wings like the Lotus Seven and the Morgan the constant should be reduce to 0.8.to help the reader in his choice of value for Cd when estimating the probable performance of a new design of car Table 12.3 has been compiled from published road test data .from this we see that a typical modern sports car has a drag coefficient of about 0.4 …………a typical design of pre-war sports car, with flared wings, a slab fuel tank at the rear, a flat windscreen with only about 20 degrees of rake but with the hood errect and side screens in place would have a value for Cd of 0.7 to 0.75……………..
Figure 1.EDITORS sketch, reflecting features mentioned by Campbell.
…………..The Lotus Seven is in many respects a replica of this older design, but with modern materials and design techniques the weight is almost halved. Where the object is sheer acceleration good handling and modest to speed the Lotus seven makes sense .If only we could persuade Colin Chapman there is still a market for an updated Lotus Seven perhaps he would design one, still a kerb weight of about 1700 lb., but this time with a drag coefficient of 0.4 to 0.5″
In fact Chapman did with the Elan
In order to have context and comparison subscribers are directed to our article on the Mk.VIII. Chapman was at a severe disadvantage of budget and availability of engines. His quest for ultra aerodynamic body shape was a means to overcome this restriction.
The Mk.VIII was quite extraordinary for its time and a relatively small capacity car.
Rather than repeat we direct subscribers to Ludvigsen whose chapter and details of the Mk.VIII are excellent technically and conceptually for the rationale for this car.
The Esprit was a Supercar.Its total package reinforced this.
There is no need to expand here. Subscribers are directed to our dedicated article.
What we invite is that subscribers examine critically the interrelationship between performance, effectiveness, sustainability [ including fuel efficiency], price.
Cars and brands tend to fall into brackets and Chapman and Lotus were heavily into added value.
They used creativity to overcome technical restrictions and exceed performance expectations within a budget.
Subscribers are invited to examine facts /data provided to run a comparison across the Seven, the Esprit and Elise.
We note that Lotus might be developing a new generation of Esprit
Figure 2.Editors sketch- compare and contrast Seven S4 with Esprit and Campbell’s data above
The study of aerodynamics is complex and can often seem contradictory, hence the enormous amounts of time, money, wind tunnel time and computers used in modern F1.F1 cars require both speed and downforce. There is the risk that they can be polarised.
Chapman’s search was to minimize one whilst maximizing the other. This was achieved in the main with the Type 79.
Subscribers are directed to our dedicated articles on this late F1 car.
What we invite is that subscribers see the holistic total interaction of aerodynamics.
For Chapman his equations and outcomes were driven by considerations of cost effectiveness and the appropriate level of provision within the desired performance parameters.
The type 79 expresses the inspired conceptualization that drove and motivated the team.
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:-
- Compare and contrast “organic” aerodynamic shape with scientific .in aesthetic terms what is lost and gained?
- Compare and contrast Lotus Seven S1 with Caterham what aero details have been introduced in small sports car?
- What are the aerodynamic advantages of mid engine layout, how does this format impact on form, function and aesthetics?
- Do city cars need to be aerodynamic? What are the holistic / cost effectiveness considerations , priorities and hierarchy
- Has road and driver safety been given priority over sustainability –suggest agendas
- Compare and contrast the aerodynamics of glider and powered areoplane
- Why of late have F1 cars become so similar in appearance
- In microlights chapman was looking at personal commuter transport – how does it compare with today and drones?
- Estimate respective costs of Mk.VI and Mk.VIII bodies [ is relatively easily done via retail prices] but the exercise is better performed by forensically itemizing materials, labour time and plant requirements with skill level
- Examine Haskell’s figures –how do they relate to engine choice for the Mk.VIII and reinforce comments made by Ludvigsen?
- Use data to specify an ultra -fuel efficient city car – what would be the result?
- What is the hidden agenda behind car legislation and fuel taxation?
- What do you expect the cost of electricity to be for automobile use? Within which what will be tax?
- Lotus is possibly developing a new generation of Esprit –using data provided how do you think it might be specified? And into which auto bracket will it compete?
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 exhibitions might be appropriate: –
- Airborn:Chapman adopts the aerodynamic form in sports racing cars
- Chapman joins the Airforce:Understanding and applying the science of aerodynamics
- Chapman , Costin and Aerodynamic engineers at Lotus create an Airline
- Airs and Graces: The Aesthetics of Lotus aerodynamic cars
- Spirit in the Wind: Performance of Lotus aerodynamic cars
- Drag On
- Get Wind of: Chapman applies aerodynamic theory
- DragStar:The most refined Lotus aerodynamic cars
- Windfall: Chapman’s performance gains from aerodynamic bodywork
- Windswept:Williams&Pritchard-Artists,Artesians and Aluminium
- Windward :Driving forward Aerodynamic bodywork
- Inspired by nature :How form ,function and evolution perfected shapes and survival
- Wings: How Chapman gained his wings Flying on Four Wheels
- Drag Artist:Frank Costin-Aerodynamicist
- Feather and Fins: Natural law,examples in aerodynamics
- Plastic Arts: Materials and sculptural forms in Aerodynamics
- Brave New World:Aerodynamic Science
- Reach for the Sky: How Aviation determined Automobiles
Using published statistics and data we hope to have explained Chapman and Lotus use of aerodynamics in a cost /parameter package.
The Lotus Mk.VI and Seven offered exceptional driving pleasure and performance. The look of these cars was traditional .This was part of their appeal. They were both traditional and modern.
They exceeded within a defined performance band.
They were what they were. Spartan and functional. They sold.
Chapman the scientist, engineer, pilot and aviation knowledgeable used aerodynamics to advantage .Performance and construction costs increased with aerodynamic bodies. These were absolute functional requirements at higher speed and at races where the speed could be exploited, like Le Mans.
It ought not be overlooked that the aerodynamic bodies contributed to fuel economy and hence sustainability. This is why Lotus won in the Index of Performance.
Its perhaps overlooked how sustainable Lotus cars were and the inspiration they provide for today. Some people question the real advantage/ green credential of electric cars.
This article can be used to drive a debate about aesthetics, aerodynamics and automobile design. Neither ought it be overlooked why greater fuel economy and sustainability has not been demanded or compromised by other counterproductive considerations and legislation. Lotus cars are essentially: light, fast, and sustainable
This article might be best seen in conjunction with A&R piece on Newton’s Laws, they overlap.
In future articles we will examine the most basic of aerodynamic concepts with illustrations –theory and practice along with experiments that can be conducted by subscribers. These are necessary to provide direct personal experience of a science that otherwise seems invisible and difficult to detect.
The Sports Car: Its design and development.Campbell.Chapman&Hall.1978.
Colin Chapman: Lotus Engineering.Haskell.Osprey.
Colin Chapman: Inside the Innovator. Ludvisgen
*Mother’s Little Helper Lyrics. The Rolling Stones.Richards&Jagger.
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.