It would be hard to beat the excitement of last year’s World Human-Powered Speed Challenge, but 2016 held its own, with the team overcoming a terrible speed wobble early in the week, cracking the world record twice, and coming unbelievably close to 90 mph! Adding to the excitement, this year hosted the widest array of international competitors, with new teams from Japan and Mexico, and returning teams from the U.K., Netherlands, Russia, Australia, U.S.A., Canada, Italy, and France. Another incredible year, with incredible results, pushing the world human-powered speed record an additional 2.9 mph!
This year the week started with a bit of a scare. Since dialing in the bike’s stability in 2015, Eta had handled like a dream, but all of a sudden during Monday’s runs, Eta developed a vicious speed wobble between 50-60 km/hr. Todd managed to figure out how to get through it and to clear the timing traps at reasonable speeds, but when slowing down for the catch the wobble resumed and nearly resulted in a slow-speed crash. Speed wobble (see video) is a very interesting phenomenon, that’s very difficult to model, and difficult to nail down. We saw this wobble for the first time a few weeks before when we were testing at the Las Vegas Motor Speedway, but there it was only very minor and controllable.
After trying to figure out what had changed and trying a variety of solutions we ended up installing a rubber steering damper that did the trick. Unfortunately, the damper masks the natural handling qualities of the bike, making it much harder to launch, and adding a bit of unnecessary excitement to every subsequent run!
Tuesday evening the runs were cancelled with the most rain we’ve ever seen in Battle Mountain, so we were able to spend a bit more time with the kids at the annual Show and Shine and have the bike ready for action when the competition resumed on Wednesday. With slightly cooler temperatures, but almost no wind, Eta launched into what would become a world record run at 88.26 mph (142.04 km/hr)! For all our fellow nerds out there, breaking 88 mph (a.k.a. the speed necessary for time travel in the movie "Back to the Future") was almost as exciting as setting the world record in the first place! Of course, the following night / day was filled with various discussions of time travel and how we could use it to our advantage to attain even higher speeds.
Thursday was another good day for low winds. Todd’s power input was almost identical, but the final speed was a bit lower, possible due to cooler air, or possibly due to a small piece of foam that had broken off and gotten stuck in contact with the wheel. The result of 87.6 mph, which would have been unbelievable only two years prior, didn’t quite get the same standing ovation.
Friday the weather was getting hotter. The anticipation of faster speeds could be felt in every team, and we were warming up with 90 mph on the mind. Eta started off the evening run performing reasonably well, but with about 2 miles to go in the course the on-screen display indicate that something was wrong. The onboard computer receives power measurements from the pedals and calculates in real time how fast the bike should be going. It compares this to the bike’s actual speed and displays the percentage on the screen. Over the course of 0.5 miles, the speed of the bike dropped by 2% compared to the prediction and it was obvious that is wasn’t going to be worth wearing out the rider with a final sprint. Eta coasted through just below 80 mph and we started looking for answers. It wasn’t too long before we found a bug smashed against the front of the shell, sacrificing itself to try to prevent a record run. Eta is incredibly fast because it is designed to maintain an extended laminar boundary layer, but even the smallest bug or imperfection can cause a large turbulent transition wedge, bringing down the bike’s top speed.
With one day to go, knowing that the bike could go faster still, we pulled out all the stops. The team spent the day polishing the shell, trying to gain every last bit of laminar flow. We re-oiled the wheel bearings, coated the bike in a bug-resistance wax, and took time to mentally rehearse the upcoming run. The wind was down, the air was warm, and within the first two miles the bike was registering performance numbers 1.5% higher than we had ever seen. In the end, Friday’s bug incident may have been a blessing: being forced to take it easy on Friday after all-out efforts on Wednesday and Thursday meant that Todd still had a bit left in the tank for a solid final sprint. Eta accelerated to a final speed of 89.59 mph (144.17 km/hr), smashing last year’s top speed of 86.65 mph (139.45 km/hr). This was another massive leap in an event that had been fighting for 0.1 mph gains over the last decade. Breaking into this new range of speeds, Eta has truly earned its name and its title as the world’s most efficient vehicle.
Looking back at the year, there are two lessons that were further hammered into our team’s psyche: First, no matter how much we think we know, the harsh reality of the real world will always keep us humble. These days we assume our ideas have a 50% chance of being wrong until they’re actually proven on the road. Second, is the importance of being absolutely prepared, consistent and mentally focused for every single run. In the end there’s not much we can do about bugs and weather, except how we prepare and how we react.
Looking forward to the challenges ahead and to taking Eta through to the next level!