Sports Tech: Skeleton sledding
Image credit: BROMLEY SPORTS, shutterstock, science photo library
Skeleton is a surprisingly high-tech sport where the engineers who design the kit are almost as important as the athletes.
You might think that there’s not much of a role for technology in a sport like skeleton. Riders lie on the sled and slide as fast as they can down a track. Whoever gets to the end fastest, wins. What else is there to do?
The British skeleton sled team used to think like that, in the 1980s. Back then, the team wasn’t very good. Then, in 1994, BAE Systems employed a newly qualified aerospace materials engineer, Kristan Bromley, who loved riding motocross bikes and asked him to apply engineering principles to sled design.
Within four years, Great Britain was the world’s number one team. Bromley, who started testing his own sleds when GB riders refused, got so good at it that he was picked for the team. Apparently, the other riders didn’t want to risk using one of these new sleds because they didn’t want to jeopardise their times and place in the team by trying out something previously untested.
Soon afterwards, Bromley became British men’s number one and later European and World Champion. These days, all the top riders around the world use high-tech sleds.
Skeleton has been around since the 1880s and an Olympic sport since 2002, although it also featured in the Winter Olympics in 1928 and 1948. Riders go one at a time. Each starts with a running push and then dives onto the sled and flies down a winding ice-covered track that drops several hundred feet from start to finish. It’s the same track used for luge and bobsleigh. Yet whereas bobsleigh teams use a small vehicle and lugers lie on their back and speed down the track feet first, skeleton riders lie on their front, facing downhill, with their arms at their sides. There’s no steering mechanism, so the riders manoeuvre the sled with body movements.
Going as fast as you can, of course, involves maximising, manipulating and overcoming various forces. That’s where technology comes in.
“If we can reduce drag by 5 per cent that will equate to several hundredths of a second down the track, if not tenths of a second,” says Bromley. Bromley Sports Technologies, which he runs with younger brother Richard, a mechanical engineer, design sleds for several international teams and riders, including British number one Dan Parsons. “That’s often the difference between first, second and third at major championships, between challenging for medals and struggling to get into the top 10.”
The further down the track a rider goes, the harder it is to maintain speed. The faster they go, the more drag there is. This stops the sled from accelerating, as does any unnecessary skidding or sliding.
The best sled isn’t necessarily the fastest, though. It also needs to stay on the ice. “What you’re trying to do is run a sled on the point of instability,” Bromley says. “This means the point at which it has the least frictional drag.”
Runners on the base of the sled provide stability and determine the level of control the sled has on the ice. Each runner has two grooves on the back and the sharper they are, the more grip the sled has. “You want stability and grip, but not a snow plough on skis,” Bromley says. “You’re looking for optimal balance between control and stability on the one hand and speed and efficiency on the other.”
The saddle is also important and far more than something for the rider to lie on. It’s a steel structure that acts as the junction between athlete and sled. Any impact from the wall goes through the sled and the saddle into the athlete. To minimise that, the saddles have to be flexible. Otherwise, the forces would damage the athlete’s body.
The main part - the sled’s pan - is a composite pod designed for an aerodynamic shape. Inside it, there’s a steel frame, which makes the sled strong enough to withstand impact from forces acting on it down the track and during any collision with the walls.
Bromley says that designing the sled is about coming up with the right mix of materials and heat treatments for the steel (he won’t reveal the details, saying that it is the company’s intellectual property), so the energy is dissipated through the frame if the rider hits a wall. The frame is robust, but flexible enough to return to its original position if it takes an impact. Four bumpers on the corners of the sled protect it and the athlete from the side of the wall.
“A rider only has a 1.2 -metre-wide channel to aim for when they’re coming out of a big curve that’s maybe two storeys high,” Bromley says. “The frame structurally has to be able take the load of the knock.”
In the old days, everybody had the same sled, so the best rider always won, right? Wrong. Not all athletes are the same shape. Recent designs fit the sled to the rider, treating them both as a single system. Engineers work out what the individual rider needs by analysing their racing style and body shape.
“Some riders have good aerodynamic form and don’t seem to move on the sled because they’ve got control,” Bromley says. “Others ride very much on the limit, and therefore have to move around a bit to control the sled. They might gain in frictional drag, but they’ll lose out in aerodynamic drag.”
Bromley Technologies engineers use a Romer Absolute Arm, which contains an integrated laser scanner, a touch probe and non-contact laser scanner, to digitise and measure each sled’s physical characteristics. They also scan the athlete’s body shape, their ergonomics, the pressure points of their shoulders and knee to generate accurate mesh data for CFD (computational fluid dynamics) analysis.
In the past, sled designers gathered data from wind tunnels to measure aerodynamic drag, but Bromley says CFD is cheaper, faster, more flexible, and “is starting to give data of comparable consistency”.
The engineers also consider the shape and nature of the course on which the rider is about to compete e.g. whether warm conditions makes the ice slightly less solid. Each track has its own characteristics, which gives home nation riders an advantage as they will have spent more time practising on the track. This is particularly the case on a relatively new track, like the one in Sochi, which was designed for the 2014 Winter Olympics and will be used for the World Championships in February. During the practice week before the Championships, sled designers and technology support teams will be out taking readings from the track, to provide any final tweaks to their sleds.
Technology is now an important and permanent part of skeleton sled racing, but does it have too much influence? Who will win the World Championships next February? The best rider or the rider with the best sled? Bromley says that although technology helps performance, it doesn’t determine races and championships.
“To win medals these days, a rider does need the best technology,” he says. “But they also have to be one of the best riders, and have one of the fastest push starts.”
The sport has come a long way since Bromley started in 1994. Back then, he says, sled-making was an art, not a science: “A lot of hearsay went into these designs. Now, designers apply scientific principles and think about what they are looking for in terms of design and performance.
“You start with energy at the top of the track and you finish with energy at the bottom,” Bromley says. “Energy is lost, where’s it going?”
Absurdly simple, when you think about it - about as simple as sliding down an ice track on a sled, really, really fast.
Designed for speed
For a skeleton athlete, there isn’t a lot of equipment needed when you speed through the course.
It’s about being the fastest competitor there, and incremental differences in a competitor’s aerodynamics can mean coming first or ending up in second place, so manufacturers are always developing techniques for suit, helmet and shoe design to maximise your speed potential.
Tailored race suits, which can be used in bobsleigh, are mostly composed of Lycra. This makes for a tight fit while being light and comfortable for athletes, so it doesn’t slow them down. The suits come with hoods, but a competitor can cut them off if needs be.
The helmets are usually very sleek for optimum aerodynamics. They must be incredibly strong to protect the head, but also very light to minimise the effect of impact on the athlete. The helmet covers the face and chin too, otherwise skin will touch the ice. Perspex visors protect vision, and can be changed in accordance with track conditions.
Brush spikes are the requirement for footwear and look uncannily like a brush or broom. According to the British Bobsleigh & Skeleton Association (BBSA), the soles have over 300 needle-like spikes, which grip the ice for maximum power when pushing off.