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| The development team
of the «Heizkörper»-bike |
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| Manufacture of the
negative mould on the CNC milling machine |
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| Inserting the carbon
matting into the negative mould |
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| Hardening the laminated
half shells in the autoclave |
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| Prototype in the load
test |
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UNIVERSITY STUDENTS BUILD CARBON BIKE
4 mechanical engineering students from the Technical University,
Rapperswil, have developed a functioning carbon bike within
the scope of their degree work.
Task description / aim of project
The team had to develop a fully sprung mountain bike up to pilot
production stage. The frame was to be manufactured from carbon
and the sprung rear swinging arm from aluminium. In order to
fulfil this aim, prototypes were produced and further developed.
The cost of the project had to be covered by sponsorship money.
The way to their goal led through the following stages:
– Dimensioning and optimization of the frame
– Determination of the frame kinematics with UG motion
– Calculation of frame geometry with FEM
– Parallel work on a complex project
– Preparation for production / discussions with manufacturers
Economical production
The four biker friends first had to familiarize themselves with
composite fibre materials. Production was to be simplified and
weight saved with integral construction methods. This was accomplished
with a carbon frame of two half shells. The frame geometry and
kinematics were determined with FEM calculations and the mix
of materials established. The stresses were difficult to estimate
in order to design the aspects of the strength and rigidity
of the bike correctly. The target group Enduro was aimed at.
They chose Prepreg material for the bike frame which was hardened
in an autoclave. «The composite technology is very expensive.
It would have been absurd to manufacture the rear section in
carbon as well», explained bike fan Pfyl. «With
an aluminium construction the parts of the rear swinging arm
could be machined and welded to one another.»The rear
section was designed for a 150 mm spring travel, the pedal kick
back was calculated and minimized. «Because the bike will
be used on extreme terrains, we assumed relatively high load
forces», said student colleague Markus Föllmi. «The
same loads occur on the joints of the rear section as on the
main frame, because both elements are connected via double jointed
rods.»
Design
«We wanted to conceive the main frame with dynamic shapes,
flowing transitions and variable cross sections so that the
rider would recognize it immediately as a real carbon frame»,
said Thomas Tischhäusler.
Manufacture included in the design
With each step of the development the crew had to take account
of the industrial feasability and the cost framework. Suitable
machines and specialists had to be found for about 100 individual
parts and processes. «We were often permitted to use the
facilities of these firms», remembered Urs Bruhin. In
particular the regional SMEs (small & medium sized businesses)
were ready to listen to their requests.
Thus PaucoPlast AG in Altendorf,
to which the team were led in their search for a composite manufacturer
on the internet, was also contacted.
«I was fascinated with what determination and with how
much stamina the students set to work», stressed company
owner Paul Pfenninger.
He not only manufactured the carbon frame for the future engineers
at reasonable cost, but also helped with valuable tips. Haba
AG in Cham spontaneously made available high-strength, expensive
special aluminium to the team. Stutz Schweisstechnik in Hinwil
helped out with welding the aluminium parts.
High-tech Heizkörper
In October 2004 it was at this stage: Two prototypes were ready
in order to prove the operating and materials safety in tests.
It was also necessary to carry out laboratory measurements to
gather data on rigidity, geometry and kinematics. Various long-term
tests in accordance with DIN were called for. Velotech.de GmbH
in Schweinfurt carried out the loading tests.
Practical tests
The former racing cyclist Ruedi Hafner offered to test the efficiency
of the 13.5 kg low-weight bike with two cycling colleagues for
a whole day in variable terrains. Their conclusion was positive.
«The rear springing of the bike responded sensitively
to the smallest unevenness. The bike is ergonomic and safe»,
commented Ruedi Hafner. «The large spring travel offers
great comfort on terrains, without detracting from its climbing
capability on steep escarpments. This is not a matter of course
for an Endurobike.»The tail-heavy sitting position had
a somewhat unfavourable effect. It reduced propulsion on the
level and reduced the load on the front wheel too much uphill
– a flaw which the team still want to remedy. «Constructive
adjustments are still required. But it is astonishing how the
team could build such an amazing type of bike without any experience.»
Fit for the future
«The road to success was no mere stroll. It required a
sizeable amount of commitment», said Markus Föllmi
looking back. «Most of our colleagues thought that we
were mad to tackle our degree work as a foursome, all of which
demanded almost a whole year from us.» But by «not
slackening» the techno-freaks found the necessary resources.
«In order to create the means, something concrete had
to be laid on the table», stated Urs Bruhin. «Parts
often had to be reworked, which jeopardized the schedule. Then
again we were anxious about the necessary finances» said
Marc Pfyl, looking back. «In dealing with all these problems
we learned just as much as through the designing itself.»
In 2005 the bike should be brought to the pilot production stage
with the brand name «Heizkörper». Afterwards
it is planned to bring the bike onto the market with suitable
partners. |
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PaucoPlast AG
Talstrasse 14
8852 Altendorf
Fon +41 55 451 11 44
Fax +41 55 451 11 49
info
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