Articles
The geared Mirage Drive
- Category: Equipment, rigging & preparation
- Published on Thursday, 30 September 2010 18:24
- Written by Josh
- Hits: 3186
The geared Mirage Drive project is something that I put a fair bit of speculation into while pedalling around the ocean and the more I thought of it, the more an idea formed. I mentioned my ideas to Taso from Tastech Industries and instantly he agreed to work with me on a few prototype designs - the photo above shows the latest rendition, which isn't terribly far removed from what I think the final product will end up looking like. I've got a bit more testing to do this weekend, but the project has reached a point where I'm happy to reveal the concept in order to gather feedback before deciding upon a final design. Field testing thus far has proven positive for the most part, with results being fairly close to what I'd envisaged. I will add as a side note, however, that throughout this process I've concluded that there are some very good reasons Hobie arrived at the default design they did and I now understand why they opted to run with a single geared design instead.
I do think that for the vast majority of people, the pedal arm length of the Miragedrive really is right on the sweet spot, offering good leverage and performance without a requirement for heavy physical exersion. Its very rare for any new user to hop in, start pedalling and then complain about the action and performance of the pedals (and if that ever happens, its usually because the leg-length setting is too long or short). In short, they got it pretty much right I reckon.
But for some time now I've been curious about what might happen to leverage, torque, acceleration and cruising performance with alternative pedal height positions. My very first test involved shortening a pair of old pedal arms by 1.5 inches, which involved a fair bit of measuring, more measuring, then some drilling and hacksawing. Upon trying the new pedal position out instantly I could feel the difference in potential speed, as well as how it altered the feel of pedalling. The net result was much as was expected - the pedal height was noticably shorter, so in comparison, I was more so pedalling at a downward angle as opposed to horizontal, feeling a little like gravity was more on my side. The distance between a full pedal stroke was also shortened a little, which although causing a bit more resistence and thus physical effort, is capable of slightly faster fin stroke oscilation. This is due to the fact that the reduced travel distance of the pedalling still drives the fins the same distance as always. So although a bit more effort is required, it is possible to get the fins moving a bit faster.
Because we all have different leg lengths, physicalities and usage requirements, it's impossible to accurately determine the optimal pedal height for each user. As mentioned earlier, I feel that hobie's default position is perfect for most. But I have to admit - I do like the feel and performance from pedalling at a shortened pedal position (which creates a side effect of having to adjust leg-length position (forward) as well. No doubt about it, I'm working a little harder, but I'm certainly able to go a bit faster if need be. But it's not at all out of the realm of possbility that I may at some stage, for whatever reason, readjust the position and thus gearing of the pedal. Some users may well be inclined to use the various pedal positions to find their own sweetspot (with respect to their own fin preference) and then just chop them down to that geared position. I suspect some users might instantly decide to stay on a lower gear setting exclusively. The greatest challenge facing the project currently is finding the right hardware to allow for simpler repositioning of the pedals. Right now we're aiming to refine pedal positions and spacing between them and once perfected, we'll look at a final hardware (nuts & bolts) solution. Note that in the photo above I have a thru-bolt system for leg-length position, which is not really very accomodating to the concept of a geared drive, because changing pedal height tyopically also means changing pedal length. ie: Moving the pedal a notch down typically requires moving the leg-length adjustment forward by a notch also.
Whilst we did actually test out a pair of custom made pedals, ultimately we decided that Hobie's own pedals were perfectly suited for the cause. I thought this preferable for anyone who might be interested in such an upgrade, as reusing the existing pedals also reduces the overall cost. When we're happy with the final design - whatever it ends up being - we'll make them available to yakass members. If you find the concept strangely provocative and have some thoughts you'd like to share, now's the time to offer some input