Bicycle Design

ZIPcycle 2.0 by Eric Birkhauser

ZIPcycle-velomobileEric Birkhauser’s “open air” ZIPcycle velomobile concept was featured in a Bicycle Design post last year.  He points out that the feedback received from readers in the comments (and from an earlier post) directly led to his redesign… the ZIPcycle 2.0. In order to prove the concept, Eric’s next step is to build a working prototype, and he has launched an Indiegogo campaign to raise funds needed to accomplish that goal.

ZIPcycleThe basic idea behind the ZIPcycle is to increase efficiency so that the vehicle requires less input for more output.  To accomplish that, Eric’s design is (not surprisingly) “a recumbent bicycle that has been aerodynamically optimized for less exertion and higher cruising speeds.” As he further explains:

“The standard upright bicycle hits an aerodynamic wall as it approaches 20 mph.  If you have ever had the experience of riding with a 20 mph tailwind, you have experienced the elimination of this wall.  By shifting and streamlining the body position of the rider, and enclosing the drag causing elements of the bicycle in a fairing, this wall again can be eliminated.  The modern road bicycle and rider has roughly a drag coefficient of .80, the ZIPcycle effectively drops the coefficient to .14.  This reduction in drag means that about 40% less energy is required to maintain a cruising speed of 20 mph.  While the average commuting bicycle cruising speed is 12 mph, imagine easily doubling that cruising speed, while eliminating the handlebar strain and seat pressure of the conventional bicycle, and preserving the open air experiential component of the conventional bicycle. “

ZIPcycle-explodedKey Components of the ZIPcycle Design

  • A die stamped monocoque aluminum chassis
  • Linked steering mechanism, connecting the handlebar to the steering tube and front wheel fork (a mechanism found in underseat steering recumbent bicycles)
  • Hub shifting in the rear wheel to accommodate the necessary gearing range
  • Lubricated bearings, gears, and chains enclosed within the chassis in an internal driveshaft beam (so you will never again get grease on your clothes)
  • Hollow tail-box, accessible by tilting the ventilated seat forward, spacious enough for a medium sized bag
  • Option for an in-hub motor and lithium ion battery pack to provide hill and acceleration assist functions for cyclists in hilly and mountainous regions
  • Additionally, while the intent of this concept is to preserve the traditional open-air experience of the bicycle, the chassis has been designed in tandem with a fairing, and a fairing will be a future optional component of the design.

ZIPcycle-side

You can see a few renderings of the ZIPcycle 2.0 in this post, but I encourage you to visit Eric’s project page for more.

ZIPcycle-storage ZIPcycle-steering

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Comments

14 responses to “ZIPcycle 2.0 by Eric Birkhauser”

  1. Mohsen Avatar
    Mohsen

    I loved the concept behind zipcycle and i see how vigorously he has solved the problems of the previous design…
    Compliments to Eric

    Reply
  2. charlie Avatar
    charlie

    looks great, but wouldn’t sidewinds be a problem? seems like you could get tossed about pretty well with that kind of side surface area.

    Reply
  3. Bubba Nicholson Avatar
    Bubba Nicholson

    Keeping the body outside the fairing is an interesting approach which might diminish anxiety for many potential velomobile riders. Of course, just about anything (full wheel fairings, recumbent) would improve the modern bicycle’s aerodynamics. My own Quest tricycle is lower & includes the rider–but getting in and out of the thing! Minus the extra wheel’s drag, this idea could catch on. I hope so and we can leave the old bicycle skeletons behind.

    Reply
    1. Nick F. Avatar
      Nick F.

      I like the design, and it’s great to see the improvements over the first version. Things I’d suggest:

      Make sure your first iteration is cheap, and ride it until it dies before moving to your next prototype! There are lots of problems here in pesky old meatspace that just never show up in CAD. I can say from experience that nothing improves your product faster than the humble pie you’ll devour while dogfooding your prototype and realizing that many of your dearly-held preconceptions about the design were totally incorrect.

      In the consumer software world, people talk about “minimum viable product” as a holy grail for lean product development – but that isn’t terribly relevant for hardware products, because once your buggy product is the hands of consumers, it’s a nightmare upgrading it (and your production tooling). That concept DOES apply (powerfully) to the prototypes of consumer hardware products, however, and the sooner you can discover your failures, the less resources you commit down the wrong path.

      If you’re on your own timeline (it seems like you are)… give yourself some breathing room between prototype versions. There’s something essential about returning to a prototype weeks or months after the glow of its initial construction has worn off that lets you clearly see the failings of it – and the best steps forward.

      Hope you’re successful!

      Reply
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  5. Andy Avatar
    Andy

    I had started to construct a streamliner a few years ago, and then sold the bike before I finished. Unless you live in a flat area with good amounts of wind to make reducing the Cd meaningful, the aerodynamics of a bike like this for commuting are not the biggest factor – hills and stops are. Even if I go 10mph faster, I will still be waiting at the next intersection for my chance to go. With some moderate climbs in my commute, the weight and inability to stand and pedal on a recumbent killed my project. Basic recumbents are already on the order of 30+ pounds – add a chassis to that and you are getting above 35 pounds. Try pedaling a bike of any type up a hill without standing and you will instantly understand the problem, which is that you will need an outrageous gearing system that allows you go climb at 2mph but also cruise on flat ground at 30mph. I had a 63 gear system to handle that (3x7x3), but that had it’s own efficiency issues.

    The biggest non-starter is that recumbents are already thousands of dollars. Adding a chassis around it will add another few thousand to the retail price. You are creating custom handlebars and a new shifting system – which I can’t imagine could cost any less than another thousand on retail (Shimano Ultegra levers are mass produced and still cost >$300, so don’t expect to easily compete with their quality AND price at the same time). Shifter patents are also very extensive, and finding a new method to shift that doesn’t infringe of any concept that the big companies haven’t thought of yet and patented will be a full time job on it’s own.

    In the end, what you are designing may be great as a record setting recumbent for use on a long track, but don’t fool yourself into thinking that this design is a solution to why nearly nobody commutes on a recumbent. Commuting time has almost nothing to do with the bike used, and everything to do with the traffic, intersections, number of people on your paths, etc. Don’t get me started on why it’s an awful idea to bike over 10mph on paths too.

    Reply
    1. Nick F. Avatar
      Nick F.

      Do you think a well-integrated electric system would be able to offset some of these use-case drawbacks (assist during frequent stops, going up hills)?

      Reply
      1. Andy Avatar
        Andy

        Not any differently than with a cheap bike. If the problem to be solved is commuting across a city quicker, money would be best spent on a reasonable commuter bike with a cheap motor that last only as long as you need it to for assisting at stops and hills.

        It’s a rather simple experiment that can be done by car or bike: commute in casually on one day, and race it the next. There was a study I once read (sorry, don’t have the source now) that claimed that racing in a city will get you to your destination 4% faster, even when your top speed has increased by a fair bit. All the time you thought was saved with the speed gets lost when you wait at the same red light, or behind another car that isn’t also speeding. Not to mention that sprinting on a bike for commuting is not something people are likely to do regularly.

        I actually get through cities faster than most, by coasting to red lights and accelerating from a slight ways behind as they are about to change green. Other “fast” commuters will sprint to 20-25mph only to stop at the light, while I can slowly approach at 10mph but get back up to ~20mph as the light changes green and pass the commuter-racers every time.

        Reply
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  7. Androo Avatar
    Androo

    It’s a neat design, and I like the idea of external-rider velomobiles, but I think the construction method is just not suitable. (I say this respectfully as someone who works in the aviation industry).

    In order to realize any kind of realistic weight limit, I suspect the fairing is either going to need to be carbon composite, or a tensioned fabric (like heat-shrunk polyester).

    Monocoque aluminum requires massively expensive tooling, and unless the sheet is prohibitively thick and heavy, it will still require stringers and frame formers (i.e. like a semi-monocoque aircraft wing or fuselage). .016 inch thick aluminium is the thinnest stuff available, dents and creases just by looking at it, and still weighs 6x more than a sealed fabric post tensioning (which admittedly needs a frame to support it).

    I’d love to build some sort of design along these lines one day…

    Reply
    1. Nick F. Avatar
      Nick F.

      Wow, interesting. I had assumed that the “aluminum chassis” just meant the internal skeleton, but looking closer at the images it looks like it’s integral to the outer body panels.

      I agree about needing composites. Die-stamped aluminum would be a five figure misstep… reusable CNC’d foam molds for making composite body panels should only be a few thousand dollars, at most.

      Reply
      1. art Avatar
        art

        A hand shaped foam plug and a re-useable fiberglass negative would come in under a thousand. The nice thing about going composite instead of aluminum is that if you did your math wrong and the prototype breaks, you can make another one with a modified layup without having to source new materials and tooling. Also, die stamping those hard corners is going to be pretty dodgy.

        Reply
  8. Eric Birkhauser Avatar
    Eric Birkhauser

    Hello Folks,

    First off, thank you for your interest, comments, and positivity; they are and will continue to be invaluable in my process moving forward. Some great points have been made, coming from firsthand experience. As I make the transition from virtual to ‘meat’ space, I am certain some comments may come to haunt me, so I will do my best to heed the advice.

    If this project has caught your interest and you find the ZIPcycle vision intriguing, take a moment and join my campaign. Add comments, spread the word, and buy a cool t-shirt or hoodie. Your contribution is GREATLY appreciated!

    http://www.indiegogo.com/projects/zipcycle-the-next-evolution-of-the-bicycle

    Reply
  9. logan Avatar
    logan

    Recumbents are great for long, uninterrupted rides. They are horrible for stop-and-go urban riding, which is what most commutes are. The transition from stopped to riding is much more difficult than on a traditional bike.
    I wonder if the designer has ever ridden a recumbent with the cranks that high and an above-the-knee handlebar in city traffic.

    Reply

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