Three-wheelers.... the way of the future?

Discussion in 'Polaris Slingshot vs The Competition' started by voyager, May 23, 2016.

  1. voyager

    voyager Member

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    I got the label "the way of the future" from the movie The Aviator, which was about Howard Hughes.
    Three-wheelers like the Slingshot and T-Rex offer the type of Fahrvergnügen that somehow got lost with the modern car. Because of its single rear-wheel the three-wheeler can make sharper turns. In a normal car the two rear-wheels have the tendency to plow on in a straight line, which the front wheels need to overcome during cornering. A three-wheeler's wide front-wheel stance prevents it from oversteering under normal conditions. So far, so good.

    But have you ever realized that a three-wheeler can mean so much more. It could make for the perfect Next-Gen auto-mobile, and combine everything what we like about three-wheelers... and more. Lose the wide stance at the front and have the vehicle deal with the weight shift during cornering by making it tilt or bank. Have such a vehicle lift the outside and dip the inside, very much like a motorcyclist does, might be considered the car's last frontier...

    [​IMG]
     
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  2. Blitzkrieg

    Blitzkrieg Well-Known Member

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    I've got 40 years of motorcycling under my belt. Dirt bikes to the most powerful hyperbike ever made.

    I love motorcycles and know how to get rid of chicken strips in the curves quite well.

    That being said, what I love about the Slingshot is it doesn't wear me out. I like the fact that is like driving a well mannered sports car in the curves but I don't have to work very hard at tearing the curves up.

    So... I don't want it to "lean". If I want that I'll just drive my sportbike.
     
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  3. voyager

    voyager Member

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    I understand, Blitzkrieg. One needs a stable platform to use the 88. Can't have tilt. I ride a Moto Guzzi I use from time to time.

    What I am getting at, is that in 'three-wheeler country' there are more modes possible for various reasons and purposes - from the squat, triangle-platformed, fun-loving SS to the Piaggio MP3 tilting scooter most of you are familiar with. One is the Toyota i-Road, as a way to get around town, protected from the elements.

    [​IMG]
     
    Last edited: May 24, 2016
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  4. Funinthesun

    Funinthesun Well-Known Member

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    I don't want one (Toyoya), but her name (Driver) and phone number would be appreciated
     
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  5. Noah Katz

    Noah Katz Active Member

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    Sorry, you need to study up; all of the above is incorrect.
     
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  6. voyager

    voyager Member

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    Last edited: May 27, 2016
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  7. Noah Katz

    Noah Katz Active Member

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    Last edited: May 27, 2016
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  8. WI_Hedgehog

    WI_Hedgehog Winner of the "Most Factory Defects" award Staff Member Moderator

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    There have been a quite a few tilting-car concepts over the years, and they've all failed due to cost, complexity, and oddly enough, lack of crash safety. If you take the incredibly wide Slingshot and make it an eco-friendly micro-parker, it's not a Slingshot, it's one of the very-similar-looking tilting micro-vehicles.

    I will agree there isn't much axial grip from the centrally located rear tire, a bit much petrol in a corner and it breaks loose, especially in wet conditions. There isn't the same side-loading to enhance grip as in a 4-wheeler. That's not exactly a feature.

    You may have not tried to drift these, but it's a rather odd experience, and controlling one at speed when sliding is pretty unnerving. It's incredibly hooked-up, you break it loose, and it just goes....then you try to keep it under control and it's all over the place. It has to do with the weight shift in the front end loading the front outer tire, and the rear sliding too fast in an outward direction. When giving a correction it unloads the front outer tire and shifts the weight abruptly the other way, causing the rear to snap the other direction and if left unchecked, load the other front tire. It's as if the rear tire were on ball-bearings until it hooks up again--and that can be unpleasant if done abruptly. The rear really comes around easily, so over-correction in a slide is pretty easy to do, under-correction will cause a spin, and the sweet spot is really a narrow window between the two. With the current ECU map, good luck modulating the petrol pumper progressively. With that understanding (and don't try to drift based on the aforementioned explanation, it'll bodge in a billyo), imagine if your average driver started to fish-tail in a micro-mobile; the tilt-system would have a hard time keeping the egg from rolling and scrambling the yolk.

    Good try though!

    BMW_Isetta_-_Flickr_-_mick_-_Lumix[1].jpg
     
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  9. Noah Katz

    Noah Katz Active Member

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    Doesn't have anything to do with being central, it's because a trike designed not to roll over will have most of the weight on the front wheels.

    The rest of what you describe may be true for the vehicle you picture because of its inherent instability - high CG and narrow front track - but the rest isn't true for a properly designed one.

    In fact power oversteer should be more controllable on a trike because there's no variation of roll stiffness; lateral weight transfer is purely a function of CG location, track, and cornering speed.
     
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  10. voyager

    voyager Member

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    Interesting discussion, gentlemen.
     
  11. WI_Hedgehog

    WI_Hedgehog Winner of the "Most Factory Defects" award Staff Member Moderator

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    For clarity, the sentence's subject is "grip," "central" is simply a location descriptor, and we agree about the weight distribution vs. stability.

    However, you're excessively simplifying the relation of Center Of Gravity to handling. The window of control is narrow in the Slingshot as I described; when you buy a Slingshot and drive it for a while you'll probably come to a similar conclusion if you regularly push it past normal daily commuter driving and into "the fun zone." (hopefully you'll be getting one soon, they're a metric tonne of fun)

    If the track (vehicle width) were narrowed to facilitate meaningful tilt, the vehicle height would increase in proportion to the decrease in width, when holding all else constant. That necessarily raises the CG, providing for "a more tippy vehicle" for which the proposed solution is vehicle tilt--all good there. However, the handling has not been addressed by tilt, only vertical stability, and therein lies the rub--handling has not been addressed. If we were to address it, we find tilt causes some shift in the CG's Y and Z axis, Z being the slight lowering of CG, and Y being the movement of the CG inboard. Do note that while the Y translation helps with the outboard roll up front, the effect is minimal, and further it doesn't increase grip in the rear which still wants to come around. The tilt system does introduce difficulty wherein the tilt system tries to keep up with the course corrections from the driver; any lag results in the driver having to predict what the vehicle will do under varying conditions while the tilt system catches up, analogous to the current complications in handling during extreme maneuvers. Basically the current system would be traded for a more complex system without increased benefit regarding handling, although the vehicle would be narrower and taller which may be of benefit--of course, then it's not the low and wide Slingshot.

    2015-Polaris-Slingshot-burnout-front.jpg
     
  12. voyager

    voyager Member

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    Let's not forget that the 'four-wheeler' has come a long way from the leaf-sprung rigid axles to today's sophisticated suspension with its multiple linkages etc. IMO, it is worth researching a tilting narrow three-wheeler. For instance, I can imagine that electric propulsion and the subsequent battery pack may dramatically lower CG. Using twin rear-wheels (a bit like my avatar is suggesting) may further reduce the vehicle's tendency to side-sweep the rear. And then there's the, as far as I know, never debated option of having the rear wheels co-steer to a certain extent when taking high-speed bends. Oh, and there's of course a difference between having RWD or FWD.

    Curious what forum participants have to say... Now I know that this all has little to do with the undiluted fun you'll get out of a triangle platform as basic as the Slingshot's... Here's what I am hinting at, a sort of elongated Isetta. Perhaps you don't need 'full tilt'.... merely active dampers that compensate for the weight shift...

    [​IMG]
     
    Last edited: May 29, 2016
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