Darrell Mann
Industrial Fellow
Department of Mechanical Engineering
University of Bath
Bath, BA2 7AY, UK
Phone: +44 (1225) 826465
Fax: +44 (1225) 826928
E-mail: D.L.Mann@bath.ac.uk
Introduction
Bicycle seats are uncomfortable. According to Scott Adams in ‘The Dilbert
Future’, bicycle seats will always be uncomfortable.
State of the Art Bicycle Seat Engineering
The bicycle industry has evolved a bicycle seat design that tends to look something
pretty close to:-
Look in any bike shop, or any bicycle saddle patent on the US database and there
are literally hundreds of tiny variations about the same set of design principles. Each
one a subtly different balance between the trade-offs inherent to the concept of a product
that is required to give both weight support and the freedom to pedal. All in all, the
bicycle seat may be seen as a classic example of how the traditional Western ‘design
is a compromise’ philosophy produces a product that ultimately satisfies no customer.
Seeking Out Contradictions
The search for, and elimination of physical contradictions is a fundamental principle
of the TRIZ method. The search for design trade-offs like those found with the bicycle
seat – in other words the search for physical contradictions – is an often
potent means of defining the ‘right’ problem to be solved.
In the case of the bicycle seat, the fundamental design trade-off may be seen to be one
of compromise between a requirement for a WIDE seat in order to achieve comfort for the
cyclist, AND a NARROW seat in order to provide freedom of movement of the legs during
pedalling.
Seeking out the best compromise between the two extremes is clearly here not solving
the ‘right’ problem. The right problem is more likely to be how we might achieve
A BICYCLE SEAT THAT IS BOTH WIDE AND NARROW.
Or, expressed in the terms of the Altshuller’s Contradiction Matrix (see Ellen
Domb’s comprehensive July 97 TRIZ Journal articles for further information on
contradictions and their use), the thing we are trying to improve about the bicycle seat
is the ‘LENGTH (width) OF STATIONARY OBJECT’, and the thing that gets worse as
we try to improve the width is the ‘SHAPE’ of the seat.
For such a LENGTH/SHAPE technical contradiction, the matrix recommends:-
- THE OTHER WAY ROUND
- CURVATURE INCREASE
- DYNAMIC PARTS, and
- NESTED DOLL
as inventive principles used by others to solve this kind conflict. In particular, for
inventive principle ‘the other way round’ is the suggestion:-
"make movable parts fixed, and fixed parts movable"
And for ‘dynamic parts’:-
"divide an object into parts capable of moving relative to each other"
and
"if an object is rigid or inflexible make it movable or adaptable"
Which almost immediately gives rise to an idea very much like the following concept
from ABS Sports in the US:-
While it might be possible to argue about some of the details of the ABS design, it
seems almost immediately clear that here is a solution to the bicycle seat problem that
not only uses the two inventive principles recommended by TRIZ, but is also fundamentally
‘right’; not only giving cyclists support where the body desires support to be
found, but also – thanks to the moving seat components - giving the possibility of
zero-chafe pedalling action.
Conclusions
Bicycle seats will always be uncomfortable as long as designers continue to solve the
wrong problem using traditional trade-off methods.
Finding the fundamental physical contradiction is an excellent means of finding the
‘right’ problem to be solved.
Using the Contradiction Matrix is then an excellent means of finding solutions to the
right problem.
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