It was thought that no one would ever ride the Wall of Death faster than 45 mph, but during the record attempt, experienced motorcyclist Guy Martin attempted to reach 80 mph.
The Wall of Death has been the most enigmatic dare-devil motorbike stunt for more than 100 years. Motorcyclists ride around the inside of a vertical wall, rather like a huge barrel, at speeds of around 30mph. Most Wall of Death “drums” are about 32 feet (10 metres) in diameter.
There is a Wall of Death near Cambridge, UK, run by Ken Fox. He was approached by NorthOne Television to assist in a mad project to set the world speed record for a motorcycle ride around the wall. The stunt was performed live on Channel 4 television this week – and I was lucky enough to be right there, as a consultant engineer for the show.
It was thought that no one has ever ridden the Wall of Death any faster than 45mph, but during the record attempt, experienced motorcyclist Guy Martin attempted to reach 80mph, a speed which would completely smash existing records. So how did he do? And how on Earth can a motorcycle ride around a vertical wall?
The G-force awakens
The limiting factor for speed on the Wall of Death is human physiology. When riding the wall, you are subject to high acceleration – or G-force. Under these conditions, blood drains away from your brain and eyes, much as water is flung out of clothes during the spin cycle of a washing machine. It leads to tunnel vision, temporary blindness, difficulty breathing and eventually unconsciousness.
When riding the wall, the Gs are generated by what most people call “centrifugal force”, but in actual fact there is no such thing. Physicists prefer to say that there is a ‘centripetal force‘ acting on your body as it goes around in a circle, but I’m an engineer, not a physicist, so I’m quite happy to go with the majority and call it centrifugal force.
Either way, the highest G-force that most of us will ever experience is when riding a roller coaster, where the body (very briefly) can be subject to accelerations of up to 5G. This is the equivalent of carrying an extra five-times your own weight throughout your body. Imagine: heavier arms, heavier legs, heavier head.
When you’re riding the Wall of Death the centrifugal force pushes you outwards and then friction holds you up. Imagine the wall was wet and slippery – you’d slide right down. That’s why it was very important that the wall was kept dry and free from dust and drops of oil. Clearly, the wall has to be built indoors and we needed a very big hangar for that.
The training for a high-G environment involves flights in stunt aircraft. During those Guy found himself passing out at around 7G – and it doesn’t bear thinking about would happen if consciousness was lost when riding a motorbike at 80mph on the wall. Guy had a serious crash in August 2015 at the Ulster Grand Prix. He was lucky to come out of it alive, but only six months later he was in full swing training for the Wall of Death.