Bicycle Design

Trimtab 3×3 recumbent trike

David Parrott is developing an interesting semi-enclosed recumbent trike for his Master’s thesis in Industrial Design at the University of Cincinnati DAAP. I mentioned his Trimtab 3×3 concept briefly in a previous post, but it is worth a second mention to point out that David is currently building a functional prototype of the design at Losantiville Kunstwerkhaus, a collaborative design/fabrication studio that he started in Cincinnati with a low-impact mobility theme. Take a look at the Trimtab 3×3 Flickr set to see additional renderings of the vehicle and photos of the prototype that is currently under construction. You can also follow the Losantiville Kunstwerkhaus blog for updates on the project as the prototype progresses.

David explained that he designed the Trimtab as a transportation design project created through the lens of “Slow Design”. He points out that, “it’s a 3WD, electric-assisted, lean steered delta trike with seasonal fabric skins & seating (breathable, ripstop nylon for summer; therm-a-rest style inflatable skins for winter), an acrylic aircraft-style canopy, and flatbed storage.”

He went on to mention that his design  “challenges some of the basic dogma of the bike design scene (Rear steer! Yikes!) as well as the “I can draw it but I can’t build it”, styling-driven methodology” that is increasingly common in the Industrial Design field these days. I have heard some very strong criticism of all rear steer bike or trike designs here on the blog, so I am curious to hear what you all think of David’s lean steer concept. Hopefully when the prototype is complete, he will post some video of it in action to prove the concept, so to speak. I am definitely anxious to see the results…and I wish I could ride it to see for myself.


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Comments

22 responses to “Trimtab 3×3 recumbent trike”

  1. Adam Rice Avatar
    Adam Rice

    This doesn’t seem to be rear-steered in the conventional sense. The layout and lean-steering is similar to the GM Lean Machine concept from a few decades ago.

    Reply
  2. Adam Avatar
    Adam

    This bike does end up being a form of rear wheel steering once all of the math is worked out. It is a geometry that is nearly identical to the Trailmate Fun Cycle. Many beach front bike shops near where I live rent theses. They are super fun but very unstable once they hit higher speeds. They snap over correct and toss the rider. On the sand this is also fun. However, because of this many rental stores will not allow them to be used on city streets, only on the sand.

    I think that recumbents are a blast to ride (though I don’t own one) and with the proper isolation of forces rear wheel steering is physically possible. However my advice to you, Mr. David Parrott, is to test this thing on a mild grass hill before you take it for a high speed run on the streets, and wear a good helmet. Have fun and never stop trying. The bike looks amazing.

    Reply
    1. Aaron Avatar
      Aaron

      It isn’t “rear steer”, follow the steering head angle. it has positive trail on the front wheel.

      The difference between this and the Trailmate style vehicles is that the steering pivot line here is at or above the rider’s CoG which makes it much more stable.

      Reply
  3. Ross Nicholson Avatar
    Ross Nicholson

    I proposed the hammock bicycle seat in my failed “contest” submission, as well as motor steering. There is nothing new under the sun, eh?

    Reply
    1. James T Avatar
      James T

      Yes, the basic idea of a suspended fabric seat has been around, but that is just one element of this concept. I certainly don’t see a similarity between this design and the sketch that you submitted for the design competition.

      Reply
    2. David A. Parrott Avatar
      David A. Parrott

      I hadn’t thought of using the motors to steer. As it is now, I’ve been planning on a single input device into two, separate controllers (taken from RC cars, if you can believe that). I’d love to see your concept some time and chat about the idea of motor steering. (I’m not sure what it would do to this thing functionally, but I think the controllers could be made to manage it.)

      Reply
  4. romu Avatar
    romu

    That’s a pretty amazing concept I’d love to ride to commute everyday. But it’s pretty similat with the Mosquito concept made by 2 Frenchies in London. James have a look at the Mosquito web site: http://www.mosquito-velomobiles.com/

    Reply
  5. human_amplifier Avatar
    human_amplifier

    Neat – squew axis (AKA skateboard truck) nice n simple … and as such probably better than the 4 bar linkage.

    Reply
  6. human_amplifier Avatar
    human_amplifier

    Oh and love the comment …
    ““challenges some of the basic dogma of the bike design scene (Rear steer! Yikes!) as well as the “I can draw it but I can’t build it”, styling-driven methodology” that is increasingly common in the Industrial Design field these days” …. sounds familiar

    Reply
  7. David A. Parrott Avatar
    David A. Parrott

    I made an earlier concept that used a negative trail geometry similar to that of the Fun Cycle and Mosquito concept, and I found the same thing you described above: it was fun but nearly impossible to ride – horribly unstable, in fact. I was hoping to use the Python negative trail geometry because its open-source development jived (is that the past tense of jive? Could it be jove?) nicely with the slow design philosophy around which this concept was developed.

    I abandoned negative trail to arrive at the version you’re looking at. It has 1-3″ of adjustable (using the slotted dropouts up front – hard to see but visible in the images) POSITIVE trail to achieve stability through caster effect, just like a conventional bike. I was heavily influenced by Greg Kolodziejzyk’s Trans Canadian Rocket (TCR) trike which has similar, positive trail geometry (though a much shorter wheelbase).

    Reply
  8. Shevonne Avatar
    Shevonne

    Very cool. It’s always nice to see some new and exciting bike innovation

    Reply
  9. jorgensen Avatar
    jorgensen

    My Mattel X-15 Varoom Cycle has rear wheel steering, but only front wheel drive, and it banks into a turn, circa 1964. I had to give the original away as my mom saw a car almost run over me and it as the car was coming out of a driveway. I did however buy another 5 years ago, as they are just too cool. My son did however find that it has serious speed wobble on decents at speed.

    Reply
  10. nicolas Avatar
    nicolas

    it’s great to see a concept idea brought to life, as usually designers express themselves with some 3d drawings that are non functional. A positive trail is not solving everything, but it makes a rear steer trike ridable at any speed, as I experienced it by myself with the mosquito (100mm positive trail). This 3×3 trike though, like greg’s TCR, does not solve the bump steer pbm, which makes it not practical to ride on open road. Moreover great care has to be taken concerning the position of the center of mass to make sure the trike won’t roll over when cornering at speed, this is a trade off with other parameters such as keeping a good traction on the front wheel. Another parameter that makes a leaning trike difficult to ride is the steering induced by side winds or aerodynamic forces, it seems that this design won’t be any better than the TCR.
    congratulation and best wishes to the designer, because that kind of project is really difficult to manage successfully.

    Reply
  11. smalghan Avatar
    smalghan

    Like Adam mentioned, bumps at the rear wheel will induce some steering but that can be solved at the expense of a little added complexity. Replicating the principles used on the Carver tilting 3 wheel car, keep the body’s tilt axis parallel to the ground and also enable the front wheel to steer as in a typical delta trike. That will decouple tilting from steering so it will still track true at high speed over bumps. Highsiding is an inherent risk with any tiling vehicle so the risk is no greater with this than with a two wheeler as the temptation to test the limits always exists…Love the clean lines and look forward to a first ride report!

    Reply
  12. Leo Horishny Avatar
    Leo Horishny

    Good luck David, you have some great ideas and creativity…definitely not a widely appreciated combination, from our experiences living in Cincinnati.

    I am interested in what you have in mind for suspension. Horrible road surfaces are one of the impressions we took with us after living in Cincy for 25 years, especially within I-275. You definitely have several high speed twisting hills to test this ride quality on.

    I like the Losantiville moniker, how about a future model being tagged the “Cumminsville Commuter”?

    Reply
  13. Andy Willingham Avatar
    Andy Willingham

    There is now a YouTube video of it in action. Just search for Trimtab trike and you will find it. Was just released yesterday.

    Reply
  14. David A. Parrott Avatar
    David A. Parrott

    I am currently working on a new video and sewing some seasonal skins for the prototype. I hope to design out the bugs before spring. Please check out the videos if you get a chance!

    Reply
  15. Steven Myers Avatar
    Steven Myers

    wow looks just like the Baccara Rush from a few years back (front wheel drive, lean steer, delta, with 3x700c wheels). I don’t think they went any further than a concept image though. Although I did see teh designer do a 50 mile ride hands free in Salem Oregon and we hit 50 on one downhill into Shampoeg Park!

    Reply
  16. Jim Healy Avatar
    Jim Healy

    I tested this today, what a blast! The gear seat was small so this was nowhere near top speed but I got GT 30 mph without much effort. As with any Mark I prototype there are things that need work but overall there is great promise here. This was mostly straightaway so didn’t get a sense of how it will handle on a curve at speed. No wobble, felt steady. Thanks for the ride, David!

    Reply
  17. fred Avatar
    fred

    i still like my tryke better, mine has 2 wheels in front and 1 in back, steers like a car, but thats a cool design

    Reply
  18. Problem, solution, catch, possible solution, and outlandish proposal. | Jwinning

    […] cover image is the model of David Parrott’s industrial design master’s thesis, which is an enclosed delta t…. As a master’s thesis I’m going to shoot a bit […]

    Reply
  19. steveG Avatar
    steveG

    its not rear wheel steer, the whole frame is equivilent to the forks on any other bike/trike, just with a VERY steep rake.

    Reply

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