The Design
Objective
Build a car for Africa. It needs to be suitable for its purpose (inabililty to drive along normal roads is
unacceptable). It must be capable of local manufacture without reliance on external source of parts. A vehicle
capable of carrying people or goods is essential.
Parameters
Normal roads have ruts 300mm deep caused by lorries. There is a lot of mud, potholes etc.
There must be at least 300mm ground clearance.
(Importance of ground clearance)
The suspension must be independant so that wheels can drop down to find traction, even when the centre is
grounded.
(Importance of independant suspension)
The underneath of the car must be flat, so that it does not get caught on obstacles
The wheelbase must be at least as wide as the inside wheels of the lorries
- for UK use a vehicle needs to be car width else it will never fit down green lanes
Four wheel drive only for extreme conditions (to save fuel)
Problem with wide, high vehicle is high fuel consumption - so must be streamlined - cabin not full width of car.
twin/large fuel tanks for range but limited future in cost/ ecological terms
Front wheel drive (or bias on four wheel drive) means that when stuck with wheel spin, the car is trying to drag
itself forward, rather than pushing and so digging in.
Solutions
Testing Africars worked well in ruts 450mm deep.
Chassis to be plywood, glued, filleted and sealed with epoxy resin - a technique used for boat building.
The body panels were plywood sealed with epoxy. Its a proven
technology producing something light and strong. Using renewable softwood so little energy consumed
in producing materials or building car. Plywood needs only low cost, low skill tools to work. The presses needed to
produce large steel panels are expensive (can be made by hand but more expensive and requires more skill than wood).
There is a steel roll cage protecting the passenger compartment, and the engine mounted in a zinc coated steel
subframe.
2CV has the only spec which fits the requirments of Africa, but too small, not enough load capacity and too
vulnerable to corrosion
- 2CV design concepts - air cooled engine, front wheel drive, in board brakes
- Suspension - simple leading and trailing links allow large vertical movements of the wheels without changes
to vehicle camber. Interconnection helps keep vehicle level.
- 2CV ground clearance needs to be improved - chassis is underslung and the pull rods operating the springs are
positioned low.
Solution - lift chassis and mount springs above arm pivots, activating with push rods.
The steel beams on which the suspension arms mount
are a longer item than on the 2CV because of the extra width, but they bolt on below
the chassis rather than above and with the repositioning of springs, gains more than 100mm clearance.
Damping was improved, better controlled interconnection and more extreme stiffening of suspension under
load.
The springs used were Nitrogen gas spheres and the dampers were simple lightweight Hydrogas
units.
High ground clearance also means high engine position - needs a special purpose low profile engine.
As far as I understand it, the development of this bankrupted the company. If it had run the first
batch of cars off with the 2CV mechanicals used in the protypes, the company might still be around.
Pick-up under construction |
Third generation AFRICAR epoxy plywood chassis for the station-wagon. |
The classic form of the AFRICAR chassis before su-frames, engine or transmission are added |
Pick-up under construction
Third generation AFRICAR epoxy plywood chassis for the station-wagon.
The classic form of the AFRICAR chassis before su-frames, engine or transmission are added