Jon Wells, Morgan’s Chief Design Officer, reveals what it takes to develop beautiful, high-performance rims and rubber for the iconic three-wheeler
WORDS: JOHN SOOTHERAN
IMAGES: MORGAN MOTOR COMPANY & JOHN SOOTHERAN
Designing wheels and tyres for the Super 3… how hard can it be? After all, there are only three of them!
This view is perhaps understandable, but it’s oh so wrong! It takes a bold vision, creativity, engineering excellence, stubbornness, flexibility and a lot of caffeine to craft something this beautiful.
But let’s let Chief Design Officer, Jon Wells, explain the ingenuity, the adaptability and even the inter-departmental ‘skirmishes’ that go into creating just one element of this iconic Morgan machine.
MOG: Where do you start when conceiving such an important element of the car?
“On Super 3, with regard to the wheels and tyres, we did a lot of work to analyse the ride and handling characteristics of the previous three-wheeler, which was a stable car, but it was a car that suffered quite badly from things like bump steer and torque steer. That was a lot to do with the fact that the control arms were very short, so the wishbones were very short, too. These components had to be short, because we had a wire wheel on that car, and the way a wire wheel is essentially structured is, you have the central hub and then the laces cross each other latitudinally to give the wheel strength and stiffness. That configuration pushes all the control points in-board, which means where the upright turns the wheel, you have a huge scrub radius, and that then makes it hard to balance things like bump steer and torque reactions through the car. This makes the car quite skittish and undynamic in the way it handles.
“So, the requirement for Super 3, was to push those control points as outboard as possible.
“This was discovered in parallel to the early design work happening. So, a lot of the early design sketches featured a very deep-offset wheel, or a wire wheel. To then find out, several months into the programme, that these hard points needed to be really, really far outboard, well, our initial reaction was a negative one, because a designer is always seeking as much offset as possible to allow a dramatic deep-dish wheel. So straightaway, we threw our dolls out of the pram and we got very upset!
“However, we very quickly realised that it was perfect, because we had an engineering function having a direct and very noticeable impact on the aesthetic, and that's the right way around. If you design the aesthetics first, you have a compromised function and the car’s disingenuous.
“That happened at the same time we were appraising things, like how we hold the engine, which isn't designed to be seen. The engine mounts couldn't be too far outboard, because then they would be pushing the control points of the wishbones further outboard, and we'd be countering any benefit we were getting. That led to the engine mounts being very thin castings, and they were also sculpted to guide air into the intakes.
“It was another example, quite soon after the wheels, whereby engineering function was having a direct influence on the aesthetic, and that's what Super 3 became. Everything on that car is a functional requirement that's been considered in parallel with the aesthetics, rather than one or the other leading. I think that's why you get such an honest look and feel.”
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“Longevity of ownership means minimum impact on the planet. Because if a car's kept above ground for longer, it's not being put back into the planet, that's ultimately better for the world.”
MOG: Can you explain Morgan’s ‘Design Philosophy’?
“When you look at the front of the car, it looks mechanical, technical, it's interesting to the eye. But that's only made better and compounded further when you can actually start ‘reading’ it, physically reading it, seeing how a component connects this to that.
“We have a name for it, ‘Intrigue & Integrity’. It’s something that every Morgan should do, it should create a level of intrigue, because there’s integrity in the design.
“So, ‘Intrigue & Integrity’ – everything needing to be honest and having a purpose, is one of our Defining Principles.
“Another is Timeless Design – we believe that's important for longevity of ownership, which means minimum impact on the planet. If a car's kept above ground for longer, it's not being put back into the planet, that's ultimately better for the world. Also, we don't think a Morgan is an of-the-moment purchase, it's something you look forward to having, sometimes over many years, so it doesn't want to date quickly.
‘Being bold, and light in proportions and stature’ is another one, and these defining principles also include ‘Using Relevant Technology’. We'll only use the right technology that's relevant to the experience.
“With something like Super 3’s ride and handling, using the correct multi-pivot, with a push-pull rod system for the suspension, is a very modern technology package, but it was right for the car. We didn't become constrained by the fact it didn't look like it was from the 1940s.
“That decision really pushed the offset out on the wings. So, the offset positions needed to be wider than the track-width of the vehicle – the track-width is measured from the centre of the tyre – and they needed to be outboard of that, to get the optimum turning dynamics for a three-wheeled vehicle.
“It's not like a car where the outer (rear?) wheels are the same (track-) width as the front wheels, so they all turn on a linear scale. With a rear wheel in the middle, it really exaggerates what we call the scrub radius, because you’ve got one wheel which is pivoting on the back, so your front wheel is having to do a lot more. You almost need to get over Centre, which is what pushed all the geometry outboard.” (Can that last line be explained?)
MOG: Is there a clear focus on aerodynamics?
“Yes, at the same time as that work, we were doing a lot of aerodynamic studies, investigating the effect of having a disc wheel on a three-wheeled car, where there's no bodywork behind that wheel. With a standard car, the turbulence created by the wheel is contained within the wheel arch, and you can use other devices to evacuate that air. But, with a three-wheeler, all of that turbulent air stays down the side of the car, and the whole car has even more drag.
“Drag was a problem for the three-wheeler very early on. Even though it's got a very small frontal area, if you look at the front of the Super 3, everything is intake. The cowl is an intake, the two radiators either side are an intake, and intakes create drag.
“There's no streamlined front end on the Super 3, which meant creating even more turbulence with the wheels wasn't a good thing.
“So, we had this outboard offset, we had the turbulence and the aerodynamics, leading us towards a disc wheel. So, we started trying to embrace what that could look like.
“I think it's fair to say, we did take some influences from other wheels, like the Compomotive-style rally wheel, and some old Bugatti wheels – like those on a Bugatti Royale, which had an interesting sort of solid wheel. They weren’t the primary influence for the design, but we did look at them, because you naturally look at other styles for inspiration. However, for us, we were doing a lot of work on the body sides at the time, playing with light and the speed of the light. The body sides of Super 3 are quite flat, but they have a really gentle inflection (curvature). That means that when a light hits it, the reflection of, say, a road marking moves quite slowly along the bodywork. We wanted that elegance, we didn't want the light to break harshly and be edgy, we wanted it to sort of have a slow-moving reflection, which brings the surfaces to life.
“So, we experimented with that on the wheel. And we really, really subtly tweaked the amount of curvature in the disc wheel, so it looked flat, but it just caught a nice slow reflection, that looked luxurious.
“Next, we’d started off with just a few ribs around the outside, but we had to add more for stiffness, and then we just obsessed over the thickness and the number of those ribs. They actually push the centre disc outboard of the wheel envelope. And then those little ribs give it structure, they do all of the structural work.
MOG: What was the process behind finding the right tyre?
“So, the last thing to consider on the wheel was the profile of the rim (tyre?) itself. We were lucky on the Super 3 that we had the opportunity to develop a tyre that's unique to the car, with a manufacturer – in this case Avon Tyres. It’s not something that happens often, you normally take an off-the-shelf, proven tyre.
So, we did look at off-the-shelf tyres, but, ultimately, they didn't exist with the speed ratings and the load-performance requirements for that size wheel, unless they were much wider. For example, a BMW i3 tyre was the closest we got. It had a five-inch width and was quite a tall tyre, but it would have grown the whole wheel very wide.
“And then you look at turning circle, and when you turn a wide wheel, it will touch the body, or you'd have a terrible turning-circle, so the car would have to get even wider, and that just wasn’t an option.
“The tyres that we had on the old three-wheeler were much smaller, and, while the new car is still small, it did grow about 100 millimetres from the previous three-wheeler. Had we had the same size wheels, they would have looked like trolley wheels on this car, and they would just look proportionally out of balance. Plus, they weren't speed-rated. So, we were left with no choice but to develop our own tyre.
“We did that work directly with Avon, and we were even able to tune the ‘balloon profile’ of the sidewall, so it wasn't a square-looking tyre – it had that sort of pre-war, ballooned-front-tyre look.
“For the tread itself, we started off with a modern tread pattern, because there's a lot of science behind ejecting water, but, because of the small contact patch on a three-wheeler, that proved largely irrelevant. It meant we had more freedom to create our own tread pattern, so we designed a zig-zag grip, which was inspired by the early board-track motorcycle racers. Combining the balloon tyre wall with the vintage tread pattern and a very modern rubber compound, was super exciting.
“At the same time, we were testing suspensions and doing simulations with Corum, who are a professional ride-and-handling-simulation outfit. So, they're advising on the sort of tyre performance we'd like; we're testing different rubber compounds, and we're doing real-world, dynamic testing on racetracks.
“With Corum, we inputted the specification for the rubber and the tyre profile, and the results are then simulated. This gives you a baseline, and you then have to test that and evaluate how accurate the baseline is.
“So, eventually we had this ‘balloon’ tyre profile. And what I'm most pleased with, is that the wheel profile of the rim is tangent to the tyre, so the tyre flows seamlessly into the profile of the rim – the whole thing just looks very considered.
“I think, when you look at the car, you may not notice explicitly, but, subconsciously, it just sits right, and the wheels and tyres just look right. I think that's because of all that honest engineering.
MOG: It’s interesting that a focus on engineering excellence, has led to such a beautiful machine.
“That's it. I think that's our methodology. If you embrace the engineering, and try and celebrate it, rather than fighting it and trying to cover it up, you end up with a very honest product.
“The three-wheeler's like a motorbike – the engineering is the aesthetic. When you get on a motorbike it looks good because you can see the engine, you can see the chassis. Often, the only bodywork is a fuel tank, and that's what you grip with your legs. There's such a purity to a motorcycle… and that purity is what we wanted.
MOG: Were there any issues in the process that made you go home quietly weeping?
“No, but we did out loud! Every time an engineer would throw something in, we made sure that we were very vocal about how upsetting it was, just to keep them in check a little bit, and just to make sure they knew they didn’t have total carte blanche. But then we would make it work, and we'd all rejoice afterwards.
“But yeah, there were certainly times where we were a little shocked about where it had to go – but very quickly, we were able to make it work.
“But the wheels and tyres were a success, precisely because our suppliers worked with us collaboratively and in harmony. That's what Morgan relies on, good collaborative relationships with our suppliers, because we're a tiny engineering team.”
MOG: What material did you use for the wheels?
“It's cast aluminium wheel, so it's quite light. As a result of being such a narrow wheel, with such a huge diameter, we had to do a lot of FEA iterations (Finite Element Analysis – a computational analysis to predict a body's behaviour under load and boundary conditions), to make sure it wouldn't fail. It was a case of doing many different iterations of different materials, metallurgical arrangements and the way the materials were heated and annealed – just to make sure it was going to perform.
“Fatigue is hard to simulate over the lifecycle of a vehicle, as you can’t use real-world testing. You can't test a car for 10 years, before you go to launch, so, you have to do a lot of digital analysis to give you a very comfortable safety zone, to make sure it's never going to fail. So, we simulate a lot of that, and then we do physical testing, too.”
MOG: Could you sum up how you think the wheel and tyre package came together?
“It was a parallel approach between design and engineering, and the suppliers. That's the nice thing; it wasn’t just design versus engineering. It was an equal collaboration between the ride-and-handling requirements, the design requirements, the aerodynamic requirements, and the supplier’s inputs in terms of the rubber compounds, and how the car would handle based on all of that. It was a totally holistic approach, which I think is apparent in the final design.
“You've got a branded tyre with vintage graphics, from Avon’s historic Speedmaster line – which is another triumph. All with a correct vintage aesthetic, which is designed totally with the engineering in mind from start to finish.
“So, to sum it all up, I think it’s a collaborative package. If we’d biased it in favour of the tyre manufacturer, you'd have a car tyre that looks square, and it wouldn’t look good, but the engineers and supplier would be happy.
“If you biased it in terms of engineering, the offset would be even greater, the wheels would look ‘inverted’, the tyre profile would be skinny, but the proportions of the vehicle would look totally wrong.
“And, if you biased it purely on the aesthetic, we’d probably had a very deep offset, and the car wouldn't handle very well.
“The original concept sketches came to life precisely because of that very joined-up attitude right from the outset of the programme.”