We return this week from the World Human-Powered Speed Challenge in Battle Mountain, exhausted, but excited. A series of mechanical issues throughout the week, such as broken spokes, blown tires, and rubbing knees, held us back from showing the true potential of the Eta, but I wouldn’t go anywhere near calling it a failure. We managed to reach 126 km/hr with the bike still not fully refined and with the rider still unable to put in full power. The data we gathered shows that Eta is as efficient as predicted, which is an incredibly exciting discovery and what I would consider a huge success!
Our goal with Eta is not simply to break a speed record. Our goal is to reach such unbelievable speeds that it gets people to think twice about preconceived limits of what is possible. This year we made it through many of the necessary failures required to achieve success and we are excited to continue the journey with further refinements for next year. Read on for a more detailed description of the week and future development on Eta. Also check out the WHPSC site for full race results.
Day 1 (Monday): The morning qualifying runs went reasonably well except for the tires, which were not quite perfectly round. At lower speeds you don’t notice if part of the tire is 1mm bigger than another, but over 60 km/hr the vibration starts making it difficult to handle the bike. Todd, Trefor and Calvin all qualified at around 70 km/hr, limited by the vibrations. Not a big deal though, and by the evening runs we had fixed the issue and were ready to take it up to higher speeds. The plan was to build confidence handling the bike by taking it to higher speeds with each successive run. Trefor posted 93.2 km/hr and Todd 109.8 km/hr without having to put in too much power.
Day 2 (Tuesday): Too much wind in the morning prevented the team from running and the evening runs brought about the first mini-disaster. We had installed a new fairing to cover the front wheel, but hadn’t noticed that it could rub the tire if the winds were too high. During Calvin’s run the winds picked up and abrasion from the fairing blew out the front tire, sending Calvin into a slide off the road at about 100 km/hr. The bike is built to protect the rider in these types of situations, so Calvin came out unscathed, but this is approaching a worst-case scenario for the shell and electronics systems. Fortunately, the only damage was a scratched shell, which would mean more sanding parties for the team, but ultimately it wouldn’t hold us back.
Day 3 (Wednesday): In the morning we went for a practice ride to get more experience pedalling at higher cadence and higher power while keeping control of the bike. The winds were quite high in the evening and only Todd made a run, reaching 98.7 km/hr. Similar to our previous bike Bluenose, Eta tends to dive into the wind when hit with a gust, which makes it pretty uncomfortable (ie. scary) to put in much power when the winds are high. Eta was designed with wind stability in mind and does handle much better than Bluenose, but it will still need a few tweaks to the steering geometry or a small fin in the back to perfect it. At the very end of the run we first encountered the problem that would dominate the rest of our time at Battle Mountain: broken spokes. As Todd was applying the brakes moments before being caught at the end of the run, a loud “twanggg” rang out. One of the front spokes had broken at the threading. We went back to the Civic Center and with the help of Steve from team Varna and Hans from team Elan realized that the spoke holes hadn’t been drilled at quite the right angle and were causing unnecessary bending in the spokes. We fixed the issue in time to be ready for the Thursday evening runs.
Day 4 (Thursday): Again the winds were quite high and only Todd ran, posting 101.3 km/hr in winds that were twice the legal limit. We took the rest of the evening to make further improvements to the various components, hoping for better conditions in the morning.
Day 5 (Friday): The conditions were good in the morning, but unfortunately part way through the run Todd began to hear a rubbing noise. There’s always a lot of noise inside the bike, but it’s important to distinguish between expected noise and unexpected noise. The procedure is to try to determine as quickly as possible what might be rubbing and decide if it will result in a tire blowout, or simply in a small reduction in speed. The noise persisted even when pedalling ceased and seemed to be at a frequency corresponding to the wheels. Erring on the side of caution Todd pulled into the left hand lane, slowed down and was caught by the chase vehicle mid-course. No damage done. Unfortunately upon inspection of the vehicle we found that one of the spoke nipples had come lose and unthreaded. Once again, back at the Civic Center we isolated possible issues and got the bike fixed up for the Friday evening runs. Finally we had low winds, and a bike that was ready to go! Trefor had some trouble starting and had to scratch, but Todd managed to post an impressive 126.3 km/hr making him the 7th fastest human of all time. What’s most exciting is that this was done with far less than Todd’s full power output (due to inexperience in Eta at high speeds and some clearance issues with knees)! So we certainly knew we had a fast bike. Eta was living up to its predictions and its performance was nearly matching that of the simulation. With only one day left, we did what we could to fix the clearance issues and get Eta ready for the morning.
Day 6 (Saturday): Saturday morning the winds were calm, and even though the temperature was a bit low, it was still a good day to go fast. Todd took his time warming up, focusing on what could potentially be a record run. Slipping inside the bike he was finally starting to get comfortable clipping in the buckles and tightening the straps inside the cramped enclosure. The run started off well, with power numbers on target, but with about 2 miles to go a noise began. The rubbing was certainly somewhere in the wheel system, but given that guards that had been put on to protect the tires, it had to be the rims. Under most circumstances the best idea would be to stop, but given that this might be that last run of the year (the evening weather was looking very windy) and the bike was at a speed that could contend for the record, Todd decided to push through. Unfortunately, by the end, the rubbing of the rim and the bouncing of the bike (which continuously smashed knees against the frame) kept the bike to a mere 121.8 km/hr. Upon inspection afterwards, two more broken spokes were found and we went back to discuss our options. We thought about everything we could possibly do, and then worked through each option, but in the end couldn’t come up with a solution where the risk was worth the reward. We ended the week, with Eta in one piece, knowing that with some modifications and further refinement she can break 140 km/hr!
Further Work So what’s next? Well we’re certain excited to start on the next round of refinement and development of Eta!! We have three major development tasks to start off:
• Designing an ultra stiff/strong carbon fibre tri-spoke similar to what we were originally envisioning at the beginning of the summer. We had ended up going with spokes, thinking that it would be the least risk-prone option… but we bet wrong. The new design will involve some custom airfoil design and some fun aero-structural optimization of the wheel.
• Rolling tests to determine the best tire. Tests were performed throughout the summer, but now we’ll be taking it to the next level with more time options and more accurate measurement.
• Drivetrain efficiency. We’ve been playing around with different types of chains, and now it’s time to test them out and implement the best one.
After these research tasks we’ll be refining the inside of the bike to fix the clearance issues, making a stiffer fork, and making adjustments so that Eta handles better in the wind. Thank you so much to everyone that has helped out this year, from our sponsors and Kickstarters, to all the people we asked for advice, all the team members and all their friends and family that came in to support the project. Looking forward to continuing on and passing on exciting news in the futur