“The 21 was introduced as a stop gap design to meet the regulations that came into force in 1961, placing a 1500 cc limit on F1 engines ”
The subject of regulation and regulation change remains relevant to the current day in FI and is a central element of Chapman’s design career as we shall demonstrate in a future article devoted to the twin chassis concept.
Within this context we take the opportunity of looking at a structural comparison between the human skeleton and that of the space frame chassis.
Both share the role of supporting a body and facilitating movement.
Figure 1.Image taken from the net. The skeleton has six major functions see text.
Subscribers might like to see also structured and integrated A&R articles on:-
- Engines including Cosworth
- Lotus chassis
- Specific Lotus types
- Aesthetics series
The Human Skeleton
It has six major functions:-
- Blood cell production
- Endocrine regulation
The Lotus 21
The 21 was something of compromised design in that the preferred and potentially more competitive engine was not immediately available.
Despite this it was completed in six weeks.
It demonstrates Chapman’s flexibility and adaptability. Despite the constraints the 21 did reasonably well and raced in several categories.
Figure 2.Editors sketch of Lotus 21
From wiki: –
“The Lotus 21 was a Formula One racing car  designed by Colin Chapman. It was a mid-engine design using a tubular spaceframe structure skinned with fiberglass panels, of a more advanced build than seen in the Lotus 18. Powered by the 1.5-litre Coventry Climax FPF 4-cylinder engine, it used disc brakes all round.
Used by the works Lotus team and the privateer Rob Walker Racing Team in 1961, the 21 was the first works Lotus to win a Formula One Grand Prix, in the hands of Innes Ireland at the 1961 United States Grand Prix. (Previous victories were taken by Rob Walker’s team). Customer teams continued to use it up to 1965. It was soon rendered obsolete by the Lotus 24 and the monocoque Lotus 25 introduced for the 1962 Formula One season.”
Technical Specification from Taylor
|Engine||Coventry Climax FPF|
|Power Output||155 bhp|
|Transmission||ZF 5 speed|
|Chassis||Multi tubular space frame|
|Front Suspension||Fabricated upper rocker arm, lower wishbone, inboard cs-damper|
|Rear Suspension||Reverse lower wishbone, top link, twin radius arms,cs-damper, anti- roll bar|
|Brakes F/R||Girling outboard 10.5 inch /9.5 inch discs|
|Wheels F/R||15 X 5.5/16 X 6.5 inch magnesium “wobbly web”|
|Tyres F/R||5.00X15/6.00 X15|
|Track F/R||53/53 inch|
Lotus 21: Chassis Drawing
The chassis was tube type, clearly evident in our sketch are the hoop diaphragms constructed from tube and steel deployed in the cockpit [forming the dashboard] and at the rear to locate suspension etc.
Figure 3.Editors sketch drawing outlining the main structural elements of the space frame chassis cf with Lotus 25 monocoque.
The functions of the chassis are extremely well set out in Costin &Phipps and our subscribers are directed to this work.
We hope then our comparison with the human skeleton will be more evident.
Form and Function
“the 21 was designed with the same aerodynamic concepts and configuration as the 20, but with the intention of carrying the new Coventry Climax V8 engine to contest the incoming 1500cc formula 1…………to get the 21 mobile, Lotus redesigned it to accept the updated 4 cylinder 1497cc FPF unit….allied to ZF gearbox
The Lotus 21 of 1961 had a tubular frame but this was lower and less cigar shaped, it had a tided up body more so than predecessors .The driver’s seat was considerably more reclined .
In addition, the Coventry Climax engine was canted at 18 degrees to the vertical.
Its perhaps worth noting the cross section of the Coventry climax engine and how this major component impacted on the overall width of the car and very much dictated cockpit width etc.
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:-
- What were the exact F1 regulations for 1961?
- What controversy surrounded the announcement?
- How did Chapman adapt ?
- How does the Coventry Climax FPF compare with other manufacturers engines in 1961 series?
Exhibitions, Education and Economics
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 particular we feel the following might be appropriate:-
- The Lotus 21:Chapman gets key to the car
- Lotus 21:The bare bones
- Lotus 21 :structure and Framework
- The Lotus 21: Anatomy dissected
- Lotus 21: Constitution and Construction
- Lotus :Cerebral Design
The Lotus 21 was possibly not chapman’s greatest success but as noted there might be explanations for this within the compromises that he was forced to adopt. Despite this the car did reasonably well; we believe it was runner up. Eleven examples were sold and this must be seen in context of times, and the very large contestant base for 1961.
The A&R attempts to analysis Lotus types and bench mark these in a continuum.Its hoped this brief study we have placed it in context whilst taking a look at constructional details and allowing designers to appreciate wider structural comparisons .
Appendix 1 :from wiki-contestants in 1961 FI World Championship
[provided to assist benchmarking the Lotus 21]
The Lotus Book.Taylor.Coterie Press.
Stirling Moss 80_80.Russell.Flat out Productions.2009.
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.