Abstract
M.Ing.
Terragrader (Pty) Ltd developed a working prototype for a machine capable of making
and upgrading earth roads.
The working prototype was based on practical engineering sense and any available
components in order to produce a “concept proving” machine. As a consequence, a new
working prototype was required which would include sound mechanical engineering
design to address mass production requirements and any operational and maintenance
issues. To achieve a sound prototype design, extensive research regarding earth road
construction and maintenance was conducted.
This dissertation documents the design and development of the new working prototype
for a machine which will mechanically refurbish existing earth roads or create new earth
roads in rural or informal areas in South Africa.
The concept consists of a wheeled machine towed behind a commercial tractor. The
tractor will provide the pulling force required to:
• tear up (scarify) the existing earth road/ground.
• grade and form the road shape.
• stabilize the formed earth road by light compacting.
The hydraulic pressure needed to actuate the machine is provided by the hydraulic power
system integrated into the tractor. The machine will require a tractor driver, and one
operator sitting at the rear of the machine. From this position the operator is able to
observe and control every aspect of the earth road manufacturing process.
It is envisaged that the production machine will be operated and maintained by semi
skilled/unskilled workers, therefore, the new production working prototype must take this
into account. The project, when implemented by Terragrader (Pty) Ltd will include
training and instruction on the use and maintenance of the production machine.
The research part of the project was done within several complimentary fields to gain a
full understanding of the design requirements and constraints.
The following complimentary fields were researched:
• To determine the requirements of earth road design in South Africa,
• To understand the make up of the earth conditions in South Africa, the types of
road defects, the repair and construction methods applied in South Africa.
• The amount of pulling force required to perform a grading, scarifying and
compacting operation. As a consequence, a number of formulae and
recommendations were identified and were utilized to quantify the pulling force
required, thereby confirming that the tractor chosen by Terragrader (Pty) Ltd was
adequate.
• The types of existing road construction machinery have been researched and
documented. A survey of the current commercially available earth construction
machinery, in particular Graders, has been conducted to identify operating
capacities, and compare these with the design criteria as specified.
• Since the first working prototype was based on “engineering sense” only,
mechanical engineering design practice was used to ensure that all initial design
shortcomings and deficiencies were addressed to facilitate mass production,
operation and maintenance.
As this dissertation is being completed, the new production working prototype is being
manufactured and any difficulties or improvements are being addressed and integrated
into the design.
The manufacturing of this second prototype will be completed towards the end of 2007,
with the design finalization taking place once the prototype testing is completed.