The aim was to make a bike respecting those criteria that was 10% faster than Silvio. It turns out 7% faster than Silvio, which means it is about 24% more energy efficient. The prototype Maria was riding did leave a little on the table, that is, there are one or two things I’ll be doing to make the production version faster. Maybe another 1% faster, or something like that.
I highlighted the tease. I’ll tell you that John is surprised he was not asked how he intends to do that. Well, I asked him via email and here is what he says.
There are a few areas where we can improve the production version over the prototype while still holding fast to the key design criteria. Each of these areas probably slowed Maria down at White Oak.
- Handlebars: The bars fitted were production prototypes of the intended final design, but they are the large size. They are wider than Maria needs and so I am reasonably sure a narrower set will reduce drag. First, it will keep the arms and hands in line with the shoulders and second it will allow the arms to partly follow, even rest on, the forward section of the bars, creating a single element to pierce the air and avoiding interference drag.
- Depth below the seat: The silhouette of the bike and rider that is driving through the air needs to be minimized. On Silvio, the lowest portion of the seat is about 2cm below the buttocks. On Vendetta there is more padding and the seat shells are not quite positioned right, so there is additional depth. Removing this excess depth will reduce drag.
- Recline: With our current experience of using the headrest on the more reclined Vendetta and noting how we adapted cushioning to refine the riding position, the production model can reflect that optimizing with a more reclined body.
- Accessories: I pay close attention to designing everything on the frame and fittings to be as streamlined as I can. Then on race day we add this and that, a computer, a light etc. We add non streamlined elements. If we designed special rigging for these elements then they too would compare with the attention to detail given to the underlying frame. Everything matters. I’ll add spy holes to the boom to allow internal lighting wires.
- Bottle mounting: Not sure about this one, when I get the production prototype headrest there may be opportunities to integrate hydration better into the overall streamlined form of bike and rider.
I am hopeful that these improvements will conspire with additional rider acclimatizing on the Vendetta, more kindly weather and Maria’s known drive and ambition – to again threaten the current record. If they do so conspire I would predict a drop of another 10 minutes, which would see us meet our goal of making a bike 10% faster than Silvio.
There you have it. Combine the two John Tolhurst quotes I have given you [yesterday & the one above] and you have the inside scoop and the Cruzbike Production Model. Thanks to John for sharing this with me and allowing me to share it with you, my readers. –jim