Premiere on the ice track
After the wind tunnel tests it was now the turn of the ice track, a big moment for those taking part in developing and building the Citius bobsleigh. The initial results were more than a relief.
It was two o’clock on Monday
afternoon and the time had come: the Citius bobsleigh, a joint project between
the Swiss Bobsleigh Federation, ETH Zurich and the industry, made its first run
on the ice track. The start of the 1233 metre bobsleigh track at Igls, a suburb
of Innsbruck in Austria, was a scene of industrious activity. Mechanics,
students and doctoral students were all kept in suspense, as was Christian
Reich, the pilot for the test runs.
Last year’s 2-man bob was already
waiting at the start. Citius was still nowhere to be seen. The “baby” was not
driven up until shortly before the start and remained covered by a tarpaulin,
hidden from the inquisitive gaze of the bystanders. Now and then, a corner of
the tarpaulin was lifted to attach a cable or take something out. The secret
was finally unveiled shortly before two o’clock: Citius, with its bright yellow
streamlined outer shell, was plastered inside with grey adhesive tape fastening
the cables running throughout the bob. The cables led to small boxes that store
the test run data; Christian Reich, the pilot, still remained in the
background.
Serving the bob round the clock
Pascal Arnold, a doctoral student
at the Institute of Mechanical Systems, and Benjamin Zoller, a doctoral student
at the Institute of Fluid Dynamics of ETH Zurich, hurried back and forth with a
laptop re-checking the bob and its measurement sensor equipment and fixing a
camera to the pilot’s helmet, which was still lying on a table. Its task was to
record the course of the run. At the same time, Martin Elsener from the D-MATL
workshop of ETH Zurich together with other helpers prepared everything else
needed for the start. During the past two weeks they had all worked flat out at
the ETH Zurich Hönggerberg Campus to prepare the bob for the ice track. Often
working more than sixteen hours a day, including at the weekend, they applied
measurement sensors to the bob. Christoph Glocker, Professor at the Institute
of Mechanical Systems of ETH Zurich and head of the Kinematics I team of the
Citius project, explained that these had been positioned at the points where
critical joints were located. For example sensors were installed at the
flexible joints of the runners to follow their movements. Force sensors were
also attached in especially highly stressed areas to measure the forces
occurring. However, the participants were very reticent about the details of
the test installations, not wanting to divulge too much to the competition.
The main aim of the test runs is
to record the driving dynamics such as acceleration and rotation, as well as
the aerodynamic properties. To do this, the scientists and technicians use a
relatively simple method consisting of sticking wool threads to the bob,
recording the behaviour of these threads on film during the race and analysing
it afterwards.
Sixteen years of racing experience
When everything is ready,
Christian Reich suddenly appears. He is a former bob driver for the Swiss
Bobsleigh Federation who now builds bobs, playing a decisive part in the
construction of Citius. He began his career with eight years as a brakeman and
eight years as a pilot and has a reputation for driving with enormous
precision, consistently and “damned well”. Glocker says, “When the data curves
of the various test runs carried out with the old bob last year at St. Moritz
were superimposed, they almost coincided.” Reich also looks relaxed, as you
might expect: “When you’ve driven for so many years, you just know how to do it
and this kind of thing no longer makes you nervous.” He estimates he has
already that driven the Innsbruck track 200 to 300 times.
On the other hand, the ETH Zurich
team doesn’t look quite as relaxed – after all, it is the first time they have
built a bobsleigh. They are focused on the task in hand, say little and don’t
let anything distract them. Then a voice through the loudspeakers announces the
go-ahead for the start. Last year’s bob piloted by Gregor Baumann from the
Swiss Bobsleigh Federation will start first. It acts as a reference bob and, at
St. Moritz, has already run through the procedure now being undergone by
Citius.
Momentum from a bungee rope
To achieve comparable starting
conditions, a running start is not used. Instead the reference bob team sits in
the vehicle and waits for Martin Elsener to give them a send-off with a
stretched bungee rope. Then it’s Reich’s turn with Citius: the bungee rope is
stretched by pulling the bobsleigh backwards. When it is let go, Citius starts
to move. Everyone’s eyes are fixed on the panel which displays the time
measurements. Right from the word ‘go’, the start time is better than that of
the reference bob. However, the bob has still not experienced any particular
stress or significant acceleration or strain in any of the curves. It rapidly
disappears from view for those in the starting area and all that remains
audible is the typical dull thundering noise of runners on ice retreating into
the distance. Everyone stares expectantly as they follow the values on the
display panel. Citius runs faster than its predecessor! But still no joyful
roar, everyone just seems relieved. Christoph Glocker laughs and says, half
joking and half serious, “It’s come down.”
Although the researchers, developers
and constructors had, up to this point, assumed they had built a perfect
bobsleigh, none could say with certainty how Citius would behave on the ice
track.
Christian Reich also appears calm
and relaxed when he comes back to the top with the HGV carrying the bob and its
team. Project staff also return to the top with the HGV. At the finishing line,
they have already written a log of the run based on Reich’s report, which is
now discussed briefly with the team at the start. A certain satisfaction is noticeable
in Reich’s terse, dry comments – that the bob drove well and his driving feel
was no different to the bobs he had driven in the past. Almost with some
surprise, he comments in passing that the driving behaviour of the chassis is
unusually quiet. He has only one complaint: “The steering is not aggressive or
direct enough.” However, he says this problem can be put right without much
effort.
Unruffled to the last
In the meantime, Pascal Arnold downloads onto his laptop the data recorded by the sensors. After a total of three runs, in one of which – after a change of runners – the reference bob was faster, there are satisfied faces all round. Six more runs take place on each of the following two days. The data will be analysed carefully in Zurich. Only then will an idea be gained of what can be expected from Citius. Walter Caseri, Professor at the Polymers Institute, and Christoph Glocker, who together provide the scientific accompaniment for the program, appear satisfied for the time being: “It all looks quite reasonable.” However, no-one showed much emotion at the initial success, perhaps because they were exhausted by the hard work. But all were visibly more relaxed as everything was packed away quickly because a few had cold feet after two hours on the ice track.
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