We had to develop the
choke and filtering system with other relevant manufacturing/supply companies, to produce
a flame with the specified height and burn duration;
How to fit and hold the three shells together;
How to switch the torch on/off in a safe and effective manner;
How to produce the correct colour and texture finishes on the three
shells.
A
number of innovative solutions were utilised to satisfy the above.
It was decided that the outer and middle shells would be made from sheet aluminium and
sheet stainless steel for the inner shell. For the outer and middle shells we initially
tried drawing two halves for each shell and then tig welding them together. This was not
very successful, so by experimenting with a hand-finished wooden punch and urethane die,
we produced a satisfactory result with a combination of stretch forming and drawing. This
proved that a developed blank could be produced, and together with a final cam-form
operation, the required side curvature could also be obtained.
Once the prototype torches produced by this method were approved by SOCOG, the tooling to
be used in production was designed using CAD/CAM equipment. The wooden punch was digitised
using our coordinate measuring machine after which the three shells were computer modelled
using Autocad 14. The tool paths were then entered into our CNC Mill, which machined the
necessary punches and dies.
It was critical that the middle shell fitted properly in the outer shell. In order to
ensure this, it was important that the length and width curvatures were consistent. It was
decided that a 'tapered' tool should be designed on which both shells could be made. This
ensured exact curvatures and kept the cost of the tooling to a minimum.
The same design/development approach was taken with the stainless steel inner shell, with
the material being stretch-formed initially over the wooden punch and urethane die after
which a dedicated production tool was made for this part.
In order to hold the torch together, we decided to try a hinge-pin idea similar to a
cut-throat razor. This solved a number of problems as follows:
- Joined the
completed assembly together;
- Provided a datum
point that enabled us to maintain the very close tolerances required;
- Together with
the cam formed sides it enabled self locking opening and closing.
In
addition to the above, the hinge-pin provided the inspiration to use the pivot point for a
cam style on/off switch which enabled the engagement/disengagement of the gas cylinder via
a simple push-rod. The on/off switch was designed to be self-locking in the 'on' position,
i.e. the switch needed to be in the 'off' position to open the torch and give access to
the gas cylinder. If an attempt was made to open the torch when it was lit, the switch
would automatically move to the 'off' position and the flame shut down.
The push-rod was designed to ensure that a 'straight' push action moved the gas cylinder
in an angular direction, in order to engage the gas cylinder into the burner housing and
allow the flame to be lit.
A nylon compression ring was also designed into the gas cylinder housing which produced
adequate back pressure to disengage the cylinder when the torch was switched to the 'off'
position. A safety washer was also fitted into the burner housing prior to the torches
being packed, which ensured that the gas cylinder could not be engaged by mistake during
storage and/or transit.
We worked very closely with Fuel & Combustion Technology and Adelaide University on
the fitment and final testing of the fuel system and burner assembly. The decision to
include a stainless steel secondary weather shield inside the top of the inner shell gave
a seamless look to the top of the torch and minimised the possibility of the flame being
extinguished in light rain conditions. It also acted as an additional heat shield, which
minimised heat transfer to the middle and outer shells.
A
significant amount of time and effort was required to design and develop the choke
assembly. This assembly regulated the gas flow and it took several months to develop a
choke and filtering system that gave a consistent burn time and also solved the inherent
clogging, vapourising and freezing problems.
The
final choke assembly was made up of three brass turned components and housed a 0.2mm thick
brass 'choke-cap' with a 70 micron (the approximate diameter of a human hair) laser cut
hole in the centre. This laser cutting of micro-machined parts was developed by Macquarie
University and Applied Laser Technologies and eventually, after experimenting with
different shaped holes, a consistent result was obtained.
The choke assembly also housed a 40 micron sintered brass filter followed by a 25 micron
gauze filter to ensure that the choke did not clog-up.
The colour and texture finishes on the inner and middle shells were quite easy to achieve,
in that there was no additional work required on the stainless steel inner shell and the
middle shell was anodised in turquoise blue to represent the blue waters of Sydney
Harbour.
The white fibre finish of the outer shell was intended to capture the feel and appearance
of the Sydney Opera House roof tiles and was provided by a local company who had the
methodology to achieve this look. It was decided to apply a white powder coat finish to
the outer shell, after which it was immersed in a water bath and a transfer film applied.
After drying, a two-pack clear polyurethane lacquer was applied to provide a superb glossy
finish.
Various ideas were considered for the application of the logo. It was finally decided to
use a silver hot foil stamp to achieve the required look.
When fully assembled each torch weighed 0.9kg, well below the specified maximum of 1.5kg
which made it very user friendly for younger, older and physically challenged
torch-bearers. It also made it easier to be carried underwater during the Barrier Reef leg
of the torch relay. For this leg, Paines-Wessex developed a special flare which was fitted
inside the torch and was capable of burning both in and out of water. The flare had a burn
time of approximately 3 - 4 minutes.
The use of clean-burning butane-propane gas reduced carbon emissions and made the torch
very environmentally friendly.
The reasonable cost of production also allowed SOCOG to offer each torch for sale to
individual torch-bearers.
100% of the design activities were carried out in Australia by Australian organisations.
Subsequently 95% of the materials used in the manufacture of the 14000 torches were
Australian. As stainless steel is no longer produced in Australia, this had to be sourced
from overseas.
The torch gained widespread approval and acceptance for both appearance and functionality
by SOCOG, the IOC, past and present Olympians, Australian sports people from all sports,
print and electronic media and of course the general public. This was proven time and
again as the torch relay progressed through each leg of its Australian journey and
culminating in the lighting of the cauldron at the Olympic Stadium on 15 September 2000.
Without a doubt, the colours, textures and shape captured in the original aesthetic design
to represent the culture and embodiment of Sydney and Australia as a whole, were
transformed into a wonderful example of practical engineering design and innovative
manufacturing methods. The cooperation and teamwork shown by all the organisations
involved in the design and manufacture of the torch resulted in a quality product that was
seen and admired by countless millions of people across the world.
The key organisations involved in the project were:
- SOCOG - Customer
/ Team Leader
- G.A. & L.
Harrington - Project Manager, Engineering Design / Development & Manufacture
- Blue Sky Design
- Aesthetic Design
- Box and Dice -
Solid Model
- FCT and Adelaide
University - Burner System
- Paines Wessex -
Underwater Flare
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