The luxury of designing for one

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It weighs 7.5 tonnes and is powered by both a jet engine and a rocket, which together will produce over 135,000 bhp – more than six times the power of all the Formula 1 cars on a starting grid put together. It has temperatures inside the rocket that reach 3,000°C – twice as hot as the inside of a volcano. And it’s all designed to power the supersonic Bloodhound car to over 1,000 mph.

But when it’s screaming down the South African desert, the car will be controlled from just one component – our steering wheel – designed for just one brave driver, Andy Green (see video here).

The Bloodhound project has faced many extreme challenges and is an awesome engineering adventure. However, as we became more and more involved in the design of the steering wheel component, I couldn’t help but notice the contrast with the design challenges we normally work on that end up in mass production. So I thoroughly enjoyed the specificity of the Bloodhound brief – which led me to ponder on how manufacturing volumes influence our design approach. I think this can be summed up in three areas:

1. User needs – we normally design products to be used by millions of people in multiple markets. This means that, although they differ hugely in age, physical size, strength and cognitive ability, they must all receive a safe, consistent and excellent experience to meet their specific needs. To understand these diverse customer groups, we employ techniques like ethnographic research, human factors studies and statistical analysis. We then test design features, through prototyping, with representative user groups to validate our vision.

With the Bloodhound steering wheel, on the other hand, when a feature needed to be confirmed or adjusted, we simply had to print a model and ask Andy to hold it. Luckily for us, Andy has an extraordinary clarity when it comes to what he likes and dislikes – and this process quickly led to an optimised design, with adjustments to the button locations, the handle geometry and the clearance for his legs until everything was right! In terms of mechanical strength, we could proof test the actual wheel to make sure it met the technical specification. Although we calculated the strength using finite element analysis, it was verified by a tensiometer machine when we had the first sample wheel manufactured. We were later reassured to hear that the Bloodhound team couldn’t actually break it in what was intended to be a destructive test.

2. Manufacturing volume – when we create new products for our clients, we must consider how to mechanise manufacture to make millions of replicas at high quality and low cost. As engineers, we need to maintain the function of a new device despite the natural variation of materials and manufacturing processes, and the degradation of the product during its life. We use strategies like ‘failure modes and effect analysis’ and ‘tolerance analysis’ to help predict how the design will react to manufacturing variances – and how this might lead to failures or poor outcomes for the user. We identify critical design and manufacturing features – and check that they can be easily reproduced by the materials processes we are using to ensure a high production yield and high product reliability, all within acceptable costs, of course. Because we never see the product before it is shipped to the customer, we have to rely on statistical analysis to prove that every copy of our design will work as intended until it comes to the end of its service life.

The Bloodhound steering wheel, in contrast, was manufactured in a very low quantity (just a handful – the actual wheel and a few back-ups). This allowed a very slow (days/hours rather than seconds) and very high-performance manufacturing process to engineer a large margin of safety to make sure nothing would go wrong. So the wheel is 3D printed in titanium and costs around £15,000 to make – a manufacturing cost per part that would make our regular clients faint!

3. Environment – in product development, the environment of use can be hard to predict. During transportation, a product can be taken from extremes of cold to hot or wet to dry – consider a medical device trucked across a desert in the Middle East that then has to perform a critical diagnostic test. We engineer products for these extremes, which often leads to significant design challenges. The product can also sit in contact with nasty chemicals on a shelf for years before the customer receives it – which could slowly degrade many plastic components.

The difference with the Bloodhound project is that the environment is relatively well known. We know where in the world the steering wheel will be used – and that it will be used under the strict supervision of many project engineers. However, no car has ever travelled at the speeds expected – and when you extend that thinking beyond our component to the whole car’s aerodynamics, power and stability, then only the engineers intimately involved in the project really understand the scale of the challenge. 

However, they are overcoming this challenge using the same principle that we use to create reliable mass-produced products. It’s based on careful specification of the challenge, breaking this down into systems and subsystems, and then designing each carefully to that specification. The design is systematically tested – first at component level, then system level and finally at car level. Then the Bloodhound team will run the car gradually faster and faster, all the time monitoring performance through a network of sensors and data loggers installed around the vehicle. If the calculations work out to be correct, this process will continue until the 1,000 mph target is exceeded.

So, in conclusion, do I really think that designing for the ‘one-off’ Bloodhound was a ‘luxury’ project? As a potentially iconic design for such a high-visibility engineering project, then it truly is an honour to be involved. Certainly, with the steering wheel, many of the complications involved in design for high-volume manufacture just went away.

But, at the end of the day, it was not detailed aspects of process or approach that I remember most. What I have really taken from the experience is the value of having a team with such a clear and inspiring vision of success for the project – to travel at 1,000 mph and inspire a generation of new engineers. This vision meant all the people we worked with were totally focused on finding ways to succeed. Perhaps this is because we can all visualise the 1,000 mph run in our mind’s eye – whereas a million different customers using a product, each in a slightly different way, in their daily lives is much more divergent.

So what I will take back from the Bloodhound experience to our ‘designing for the many’ projects is that when you can build a ‘clarity of vision’ across the team as to what success looks like, then this will pay dividends many times over in the outcome of the innovation.

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Jez Clements