2.4 Simple Structural Surfaces
The simple structural surfaces method SSS originated from the work of Pawlowski [Ref. 3] and is described in the notes by Brown [Ref. 2] and the book by Brown, Robertson and Serpento [Ref.4]. These references should be consulted for a thorough understanding of this approach.
The SSS method provides a simple way of determining load paths through a structure. Each surface is assumed only to have in-plane stiffness and no out-of-plane stiffness. Each surface is acted on by forces, e.g. the engine mounts. For equilibrium, adjacent surfaces must provide reactions. This process is continued throughout the structure and determines the load on each SSS. It can then be realised if an SSS has insufficient supports or reactions and therefore determines the continuity of load paths and the structures overall integrity.
Fig. 9 [Ref. 2] Fig. 10 [Ref. 2]
As can be seen in the SSS example in Fig. 9 the box structure is loaded in torsion by the moment Ms, which causes the shear forces Q1 and Q3. All the surfaces are in complementary shear, and the structure is stiff in torsion.
If one shear surface is removed, as shown in Fig. 10, none of the complementary shear forces can exist. The torsion load is then transferred to the floor of the box via the edge forces Q, so the floor panel is loaded out of plane rather than in complementary shear.
3 The Locost Concept and the Competitors
3.1 The locost concept
Luego have become part of the cottage industry to emerge from the Locost concept. The locost concept began a number of years ago with the publication by Ron Champion of his book “Build Your Own Sports Car for as Little as £250.” This book details how he designed and built a Lotus Seven Inspired Sports car for his son and others in his capacity as a teacher of motor engineering at a public school [Ref. 5].
Due to the low budget on which the car was to be built, it was named the Lowcost, later shortened to Locost. This is a two seat open top sports car with a front mounted engine and gearbox linked by a propeller shaft to a rear mounted final drive.
The original Locost chassis was based around the running gear of the then cheap and plentiful rear wheel drive Ford Escort Mk.2. Many of the components of this “donor car” were used on the Locost with the major components being the engine and ancillaries, gearbox, propeller shaft and rear axle.
These items dictated the rear track of the car and the basis of the wheelbase. However, this led to the construction of a chassis that was relatively narrow. The rapid success of the book and the number of builders emulating Ron has led to a shortage of Mk.2’s. this has been exacerbated by the race class set up for running Locosts by the 750 Motor Club which dictates the chassis and running gear to be as per the book. Replica parts are available but do not adhere to the Locost ethos aspired to by many builders.
This shortage of available Mk.2 donors and the lack of space available in the original chassis has led many builders and chassis providers to use an alternative donor car. The favoured replacement for the Mk.2 Escort is the Ford Sierra. This is also front engined, rear wheel drive but comes with a range of engines from the 1.6 Pinto to the 2.8 Cologne and Essex V6’s and even the 2-litre Cosworth derived engine. It also benefits from a 5-speed transmission and independent rear suspension. This is all packaged in a slightly longer wheelbase and wider track. This allows a chassis to be designed with more room for passengers and a more varied drive train choice.
Luego were the chassis constructors for the Champion Motor Company as mentioned previously. Seeing the decline in parts availability and the popularity of the sierra based chassis’ they have constructed a prototype chassis to accept the Sierra running gear and provide fitment of a wide range of large displacement engines from the Pinto to the Rover V8, Ford and Chevrolet, small and big-block, V8s’ and the Jaguar V12.Motor