Empire Bikes at TCT Show 2013
It’s not often that we get the opportunity to demonstrate the speed of product development that has been facilitated by AM in real time, but thanks to the involvement and quick work of UK-based Renishaw, the next chapter of the Empire Cycles story started is ready to be unveiled.
In the July 2013 issue of TCT we reported from an industrial estate in Bolton about a man with a plan to re-invent the bike, and the companies helping him with his dream of re-shoring cycle production to the UK. Working from the premises (and with the support) of Merlin Engineering, Chris Williams’ Empire Cycles is railing against the near-monopoly of bicycle manufacture in the Far East; specifically China and Taiwan. Realising that it’s impossible to compete with the ubiquitous hydroformed tubular frames so familiar to any cyclist, Chris decided to use his experience in Moto Cross to bring the competitive advantage to UK manufacturing and to riders of Empire’s bikes.
Making use of the Stratasys uPrint installed at Merlin Engineering’s production facility, Chris started to toy with 3D printing as a development tool both with scale models and latterly full-size 3D printed parts. Visitors to TCT Show + Personalize in September would have seen the fruits of these labours in the Innovation Showcase. The next logical step would be the production of additively manufactured functional parts, which is where Renishaw come into play.
Chris explained how the project got underway: “I've actually been using AM components in production for many years in a small way, this is the first time I've had the opportunity to have a go a full working product. I rang Renishaw up and let them know who I was and what I would like to do. They went away and did some research on me and then just said yes they would love to build all the parts!”
The team at Renishaw thought that some of the standard simple parts like the seat post or headstock could be the way forward to shave off a few precious grams as they were known entities and simple enough to validate and test. One only has to look at the professional road racing teams to see the hours of R&D — not to mention the significant investment — that goes into losing a gram here or there, gaining a split second in the process.
Initially the aluminium cast seat post part was taken and built as a benchmark just to show the base abilities of the laser melting process. Renishaw provided advice on how the part could be lightened; they used Altair’s solidThinking Inspire 9.5 software to perform a topological optimisation.Inspire generated a new material layout within the package space using the loads and supports as input. This provided a concept that not only met the performance targets but was also minimum mass.
Chris then took this model and used his own design know-how to generate suitable geometry around this concept for ALM manufacture. A tool such as Inspire goes hand in hand with ALM by generating component designs that maximise the manufacturing freedom of ALM, leading to stronger and lighter components.
“The intermediate part turned out difficult to build using the AM process,” explained Ian Brooks (Renishaw applications engineer) “I went to see Chris and worked through some of the sticking points, for example where unnecessary amounts of support were needed or where breaking supports from the main part would prove difficult. Other minor design points like drain holes for excess powder were integrated into the later designs.”
The ultimate aim of the project was weight saving, and the resulting parts are designed for maximum strength with minimum weight, not for aesthetics: “Eventually this thing will be chucked down a mountain with someone, probably Chris himself, on it. At that point what it looks like becomes irrelevant if the engineering behind it fails.”
“We took the seat post bracket from 360 grams down to 200 grams, and the cost of the weight savings don’t have to be made up in other areas. What we haven’t bottomed out yet is the finite element analysis, which is a big job for a project like this. What we can do is get close to optimum and test the bike in the real world with a whole host of sensors on the frame and collect actual data and optimize from there,” explained Robin Weston (Renishaw marketing manager).
Further weight was saved by integrating the clamping threads into the design, doing away with the need for a separate bracket.
With the huge weight saving achieved on this single component, and some reservations Chris had about the design, the scope suddenly expanded.
“Where we’d thought about extruded or hydroformed aluminum tubing or even carbon fibre for the frame, bonded onto some titanium bits for at the corners of the triangles (where the tubes meet components like the seat post and headstock) we started to look at doing even more. Chris explained that the use of the standard frame materials really inhibited the design freedom. As we looked at the likes of the main aluminum frame and realised that component weighed 2100g on it’s own; we knew we could help to create something equally as strong and shave a huge amount of the weight off. From there the idea that we could do more, even all of the major frame components, came together.”
It was agreed that the team would aim to build the whole frame, seat post and swing arm additively, allowing complete freedom of design. Hope Technology Ltd, a major supplier of precision CNC parts for cycles have agreed to complete the bike with the non-frame components and — fingers crossed — the whole thing will be on show at Euromold on Renishaw’s stand.
The cost of the process is such that the finished bike would be expected to retail for somewhere in the region of £20,000, but as David Ewing (Renishaw marketing engineer) explained: “It won’t be cost-effective at the moment but that was never meant to be a part of the project. Proving out a new concept will hopefully pave the way for more cost-efficiency in the future.”
The potential final cost of the frame alone lead to some further potential innovations in the construction. It would be quite easy to ‘build’ in serial numbers, riders names etc that would prove a barrier to theft. It may even be possible, eventually, to embed RFID chips into the frame as it is being built, creating a security tag embedded in the metal of the frame and therefore making it extremely difficult if not impossible to remove.
In terms of strength the initial optimised seat post bracket has already been tested to the BS standard, which includes exerting 1,200 newtons applied and released for 50,000 cycles at no more than 25 hertz. “We thought why not test to destruction and see how strong it really is – so far it has exceeded the standard 6 times, at 300,000 cycles and counting. This is after stress relief only; we are planning advanced heat treatments, such as Hot Isotatic Pressing (HIP) which could improve the properties even further”.
Going to press, half of the bike is still being designed, whilst the other half is going into production. The deadlines are incredibly tight, but as the pressure increases so does the excitement – after all it’s not every day you get to revolutionise the manufacturing techniques of this iconic mode of transport. As for the weight – you will have to wait and see, but the CAD data is predicting a reduction of 50%…