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  • #16
    Originally posted by justanengineer
    Many vehicles do this today, and it is one of the reasons why "A arm" independent suspension on all wheels has become so popular.

    If you look at an independent suspension, typically you have either two A arms or one lower with a driveshaft acting as a second upper link, ie connections top and bottom of the hub. These two links are typically not parallel and swing in arcs independent of each other. The links also typically arent of equal length and consequently the arcs they swing arent of equal radii. By having a greater distance between the two links at the hub than at the frame, or by having a shorter upper link (ie, tighter upper arc), or other geometric "arc analysis," its rather simple to make a car "lean" into the turns.
    Well, its simple to have wheels that lean into the turns when the car leans *out* of the turns, resulting in a higher inner wheel and lower outer wheel and the car trying to flip itself over as its center of gravity moves to the outside of the turn.

    I was looking at making the car lean into the turns, ie try and move its center of gravity to the inside of a turn.

    I am starting to think that with a light enough vehicle and soft enough suspension, the operator should be able to just lean the vehicle with his own weight. Maybe with some kind of seat tilt feature to make leaning more natural feeling.
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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    • #17
      Perhaps you might want to look up William F. Milliken. His book, "Equations
      of Motion" publilshed by Bentley
      could be an interesting read for you.

      Among many topics, Mr Milliken recounts his self-financed design and
      construction of the MX-1 camber car. This car was the inspiration for
      the STV mule subsequently developed by Frank Winchell's group at
      GM. It no doubt also served as an uncredited inspiration for MB's F400
      ARV
      fourty years later. Mr Milliken mentions the F400 in EoM
      and notes that it does not meet, let alone surpass the performance
      of his MX-1.

      In lieu of reading EoM, here is a bio by auto journalist Karl Ludvigsen
      that appeared in Automobile Quarterly, First Quarter, 2004 - 'Mister
      Supernatural'


      In gathering material for this post, I discovered that last fall (11/11)
      the very spry 101 years young (DoB: 1911.04.11) Mr Milliken, tested
      the MX-2, a second-gen camber car built by Multimatic
      , the Ont,
      Canadian performance engineering firm.

      Edit: Ludvigsen, not Ludvigson

      .
      Last edited by EddyCurr; 04-13-2012, 02:06 AM.

      Comment


      • #18
        Originally posted by Black_Moons

        I was looking at making the car lean into the turns, ie try and move its center of gravity to the inside of a turn.

        I am starting to think that with a light enough vehicle and soft enough suspension, the operator should be able to just lean the vehicle with his own weight. Maybe with some kind of seat tilt feature to make leaning more natural feeling.

        It would seem to be easy enough until you think about it for a minute or two. To make the vehicle lean into the turn means moving the weight of the vehicle into a tighter turn than that followed by the wheels, this is easy enough on a two wheel vehicle where a turn is initiated by first steering out of the turn then as the vehicle begins to topple reversing the steering and balancing things out with speed and centrifugal force. (***** plenty of scope for debate here****** ). I am not sure how the same situation could be induced on a three or four wheel vehicle that is, unlike the bicycle, inherently stable.

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        • #19
          W.F. Milliken's MX-1 camber car.

          I also see that in Sept 2011 Mr Milliken was inducted into the 'Legends of the Glen'.
          Along with some guy named Andretti ...

          .
          Last edited by EddyCurr; 04-13-2012, 02:33 AM.

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          • #20
            Originally posted by The Artful Bodger
            It would seem to be easy enough until you think about it for a minute or two. To make the vehicle lean into the turn means moving the weight of the vehicle into a tighter turn than that followed by the wheels, this is easy enough on a two wheel vehicle where a turn is initiated by first steering out of the turn then as the vehicle begins to topple reversing the steering and balancing things out with speed and centrifugal force. (***** plenty of scope for debate here****** ). I am not sure how the same situation could be induced on a three or four wheel vehicle that is, unlike the bicycle, inherently stable.
            Well, Yes, I think the solution here is in the fact that my vehicle will hopefully be a fraction of the drivers weight and just by having the driver shift there body, they will be able to put enough weight on the inside tires to greatly improve cornering and stability.

            I also thought it might be an amusing exercise to have a steering column that tilted side to side, directly controlling camber of all 4 wheels via control linkages. Maybe Mk2 will try that out...

            You would lean to balance the G force on yourself in a downward direction and drag the steering column with you.



            Of course, While talking to the motorcycle/ATV shop owner down the road today about 'leaning 4 wheeled suspensions', he had an interesting tidbit to say:
            "That is a stupid design. You will still wipe out, Just differently!"

            He may very well be right in a way..
            Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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            • #21
              Hmmmm... I think you are leaning towards the principles of a skateboard! That could be worth a close look I think!

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              • #22
                Originally posted by The Artful Bodger
                Hmmmm... I think you are leaning towards the principles of a skateboard! That could be worth a close look I think!
                Motorised skateboards are not allowed due to too small of wheels. The city can't be bothered to actually fix the potholes around here, so they would rather just ban vehicles that would be fatally affected by them!
                Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

                Comment


                • #23
                  Originally posted by The Artful Bodger
                  It would seem to be easy enough until you think about it for a minute or two. To make the vehicle lean into the turn means moving the weight of the vehicle into a tighter turn than that followed by the wheels, this is easy enough on a two wheel vehicle where a turn is initiated by first steering out of the turn then as the vehicle begins to topple reversing the steering and balancing things out with speed and centrifugal force. (***** plenty of scope for debate here****** ). I am not sure how the same situation could be induced on a three or four wheel vehicle that is, unlike the bicycle, inherently stable.
                  You do it by making the steering/suspension behave like a bicycle!

                  That has already been described in this thread!

                  Here's a nice tilting recumbent trike; http://www.youtube.com/watch?v=GCJp4tU4TE4

                  Also look for Piagio MP3 on youtube.
                  Paul Compton
                  www.morini-mania.co.uk
                  http://www.youtube.com/user/EVguru

                  Comment


                  • #24
                    Originally posted by Black_Moons
                    Motorised skateboards are not allowed due to too small of wheels. The city can't be bothered to actually fix the potholes around here, so they would rather just ban vehicles that would be fatally affected by them!

                    I was not suggesting a motorised skateboard but rather an examination of the principles on which they are steered.

                    Comment


                    • #25
                      leaning into the curve

                      Back in the late 50's or early 60's someone built some hybred '' Studeillacks'' these were equipped with mercury switches and a system to pull down the inside of the curve side of the car
                      geno

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                      • #26
                        Originally posted by EddyCurr
                        Perhaps you might want to look up William F. Milliken. His book, "Equations
                        of Motion" publilshed by Bentley
                        could be an interesting read for you.
                        Eddy,

                        Hey, I have that book too! He had a lucky escape with the B-29 test flights. A very dangerous aircraft with its fire-happy Wright engines. I have the Last Great Miller too.

                        Camber Car....I don't care, that just looks wrong!

                        The Bentley link was good too, some video interviews with Mr Milliken.

                        Peter

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                        • #27
                          Comes to mind that a person could give some steer to the rear wheel pair as the front is leaned. If you consider that the rear of the front framework ends in a section of rod, about which the rear section pivots, then by adjusting the angle of that section you could steer the rear to some extent. If the rod went straight back, parallel to the roadway, then leaning the front would not steer the rear at all. If the rod were tilted downwards, then leaning the front would steer the rear into the turn. That could be a little strange to drive- . If the rod were tilted upwards, then leaning the front would steer the rear away from the turn. Too much of this would probably make it undriveable. Making this angle adjustable would give you a way to fine-tune the feel of it.

                          Of course, castor and steering tube angle on the front wheel are critical adjustments as well in terms of handling. When I did my tadpole design, I also paid a lot of attention to this. Even though it doesn't lean, I'm sure that minor changes here will be very noticeable in the way it handles. Because my bike has very nearly the same wheelbase as the tadpole, I just copied the geometry from it. I have no way of making a valid comparison to say whether it's right or wrong, I can only go from how it feels when driving it. It feels alright, not twitchy or hard to steer.

                          One of my original intents was to provide a way to adjust the steering tube angle to 'dial it in'. At the same time there would need to be a way to change the position of the front axle (or axles). They could ride in slots like the rear axle on a motorcycle, making for some adjustability. All in all it just added more complexity to the design, and I didn't go that route.

                          This is a slow speed vehicle, so I suppose I could make some comparisons to a scooter or even a wheelchair- how much work actually went into designing those things for handling - probably not much. Personally though, I'd be fussy over how it handled.

                          Where a person is designing the vehicle to be capable of comparative speed, say more than 30K or so, I would think you'd want to refine these geometries to a fairly high degree.
                          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                          • #28
                            Originally posted by Peter S
                            Originally posted by EddyCurr
                            Perhaps you might want to look up William F. Milliken. His book, "Equations
                            of Motion" publilshed by Bentley could be an interesting read for you.
                            Eddy,

                            Hey, I have that book too! He had a lucky escape with the B-29 test flights.
                            A very dangerous aircraft with its fire-happy Wright engines. I have The Last
                            Great Miller
                            too.

                            Camber Car....I don't care, that just looks wrong!

                            The Bentley link was good too, some video interviews with Mr Milliken.

                            Peter
                            I haven't read 'The Last Great Miller' and will have to look it up. Mr Milliken's
                            adventures at WG & Pikes Peak with his Miller were great reading.

                            Anyone wishing to gain greater insight into how and why vehicles handle
                            could benefit from adding Mr Milliken and son Doug's book 'Race Car Vehicle
                            Dynamics' published by SAE to their library.

                            In either EoM or RCVD, there is a discussion of tricycle dynamics, IIRC.

                            .

                            Comment


                            • #29
                              Darryl, I believe you are quite right regarding steering the rear end and I expect that regardless of front steering inclination the vehicle will be neutral when the axis of the leaning pivot passes through the front wheel contact point.

                              Comment


                              • #30
                                We're working the same page....

                                The observation you made about the wheels and side load is a vital one. On the vehicles where the rear wheels stay vertical they will for sure need to be more robust than a bicycle wheel.

                                You and I are working a very similar program though a somewhat different approach. I've decided (until or unless I find out it won't work safely) that I will be using cast wheels from a scooter. That is actually why I bought the new lathe I got, so I could rework the wheels to move the axle stub more to the middle of the wheel and to allow the addition of disc brakes and of course the steering knuckle/spindle assembly. As I mentioned (in another of these posts ?) I'm using a fixed double wheel assmebly in the rear to provide some stability but as you lean into the corner it will transition to only the inner of the two tires being in contact with the road to allow me not to require a differential.

                                The thing that perhaps most has me scratching my head at this point is having unequal lenght A arms to allow for a reduced scrub angle but still having to make allowance for the whole mechanism to lean into the corners and keeping the relationship of the steering in sync with the rest of the moving suspension (that is not ending up with the outside wheel bump steering as it were through the transition). Clearly this problem has been licked on that 4 wheeler....I'm interested to know just how they did it.

                                Stay tuned for more info as it comes.
                                Allans Rule: Anything worth doing is going to be a pain in the butt.

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