In this article we meet Tuomas and Kimi, two amateur bike enthusiasts who pooled their knowledge of materials science and manufacturing in order to design and build themselves a triathlon carbon fibre bicycle for the amateur competitor.
The friends and colleagues had a simple aim: to build an affordable custom composite bike to compete in triathlon events.
Custom-made carbon composite bicycles too costly for amateur cyclists
There are now several bespoke high-tech carbon composite bicycles out there, but they are all very expensive items for amateur competitors. A significant proportion of the cost comes from the creation of complex 3D shaped moulds needed to make the highly-contoured frame sections. "We looked at means of reducing this cost from both a design and a manufacturing approach", explains Kimi.
Using standard composite parts to bring down costs
"Our concept uses conventional carbon fibre composite tubes from 15mm to 50mm diameter, made by Exel Composites. The stiffness of these tubes contributes to the overall ride performance of the bike. It's down to rider preference: a trade-off between good power transfer and comfort", explains Tuomas.
Whilst this largely avoids the need for the expensive complex-geometry moulds to make aero dynamic tube sections, the key points remain those where the various frame elements come together: known as the head tube, bottom bracket shell and, for this study, the seat cluster. This is a complicated shaped component comprising a tube section with three of lugs where the saddle post connects to the top frame, and also connects to the rear axle. "It's where the composite tubes are bonded together, so an important component regarding load-bearing and durability".
"For the proof of concept study, we chose a wet lay-up of 8 plies of carbon fabric. Using fabric helped it drape over and around the core. This gave us a finished wall thickness of about 2mm."
"In the next development stage, we will take a closer look at optimising the engineering properties of the composite. This can be done fairly easily using ESAComp, the software tool from Componeering Inc".
"We are also equipped with Altair software, including SolidThinking Inspire used for topology optimization of complete frames and some metal parts, plus HyperMesh for basic FEA".
3D printed moulds – a low cost option to make complex composite parts
"To manufacture this key component, we investigated 3D printing as a method of making the moulds".
"With a slight change in the conventional geometry of the component, it could be made in a two-part mould instead of 3-part, using an internal removable core".
Candidate mould materials were investigated. "Too stiff and we found the mould could crack on closing, whereas too flexible and it wrinkled, so the part didn't keep the required shape".
"We used PLA for the external mould and ABS for the core. Printing took about 12 hours and, in general, the slower the print, the better the mould". The core design includes internal features as supports during moulding, but are also necessary for the printing process – can't print onto fresh air!
Here, cores were removed mechanically, but other printable materials can be dissolved either with chemicals or water, however these tend to be more expensive.
Frame assembly - a one-step bonding process
"When it came to assembling the bike frame, we degreased, abraded then cleaned the mating parts before bonding with a two-pack, RT cure toughened epoxy adhesive."
All the components were bonded in one go, so a jig was used to ensure all parts came together correctly and retained the geometry throughout the 7 day cure.
"Our first one got a traditional "Finnish post cure" = 4 hrs in the sauna!"
Some preliminary performance stats....
"We tend to talk about the frame only, because we use standard components that are not made by us".
"The bike frame we showed at JEC World 2016 weighs in at 1.4 kg, which is a little heavier than mass produced bikes. But we are not focused solely on weight because ride characteristics and structural reliability – along with price - play an important role, too", Kimi continues, "Any frame under 1.5 kg is light enough in our opinion. For steel frames less than 2.0 kg is considered good".
The overall weight of a complete bike can be brought down further by using more expensive bolt-on components, but this only increases the price.
2016 Finntriathlon events – the ultimate test schedule!
Whilst waiting for the ice to melt, Tuomas is in training and ready to put the ideas2cycles bike through its paces at triathlon races (sprint and Olympic distances) in June and July: Vanajanlinna, Vierumäki and Joroinen events.
Tuomas explains "We are honing our design specifically for these races! It'll look more like a road bicycles, using road handlebar and shifters, because the geometry of the current design is better suited for this purpose".
And, talking of price ......
"With this frame, we can do a bespoke build to meet customer requirements starting from about 4000 EUR", says Kimi, "making high-tech, personalised performance affordable".
Kim-Niklas Antin [photo: left] Kimi is a bicycle enthusiast with an engineering background. He founded ideas2cycles in 2010 and contributes mainly to the development and utilization of materials and manufacturing methods.
Tuomas Pärnänen [photo: right] Tuomas is a triathlete and composites expert, contributing to the design and fabrication of lightweight structures.
Founded in 2010 by students from Aalto University, Finland, other members of ideas2cycles (ideas2cycles.com) team are J-P Virtanen, an everyday cyclist contributing industrial design knowledge, and Jussi Hämäläinen, an FEA expert familiar with traditional hunchback FEM as well as modern user-friendly software.
Aalto University, established in 2010, resulted from the merger of three major Finnish universities: Helsinki School of Economics, University of Art and Design Helsinki and HUT - Helsinki University of Technology (founded 1849), who was responsible for the initial development of ESAComp software for the European Space Agency.
Componeering wish to thank Kimi and Tuomas for their assistance in compiling this article and permission to reproduce their photographs.
© 2016 Componeering Inc, by Jo Hussey