Linking forward and rear suspension

Discussion in 'Cycling Equipment' started by Simon Brooke, Nov 25, 2003.

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  1. Simon Brooke

    Simon Brooke Guest

    I was looking at a picture of a Whyte PRST1 earlier today, and musing as one does... The Whyte uses
    quite similar suspension units for both front and rear suspesion: <URL:
    http://www.whytebikes.com/whyte-2004/images/whyteprst1side72dpi.jpg >

    and what I was musing about was the Citroen Deux Chevaux and the original Issigonis designed Austin
    Mini. The 2cv had a single suspension unit on each side of the car which linked the front and rear
    swing-arms; the original mini used 'hydrolastic' suspension units where the oil reservoir in the
    forward suspension unit was linked with a pipe to the oil reervoir in the rear unit on the same
    side. This was a conscious imitation of the principle of the 2cv system while avoiding the Citroen
    patents. The hydropneumatic Citroens - DS, GS, SM, BX, CX, XM, Xantia and C5 - have of course more
    complex hydraulic interconnection of the suspension units but that isn't what I'm thinking of here.

    The point is that on both the 2cv (a car I love - in my opinion the world's most under-rated
    sportscar) and the early minis the scheme worked extremely well to limit pitch, giving a perception
    of a much smoother ride. When the front hit a bump and the front suspension compressed the rear
    suspension would extend, keeping the body of the vehicle relatively level.

    It struck me that this principal, if applied to mountain bikes, would possibly give a steadier and
    more controllable ride particularly over fast rough sections, and that with modern air/oil
    suspension struts it would not actually be that hard to rig up, and would add very little in weight.

    So the question is, who has tried it and what were the results? I've done a quick web search but
    haven't come up with anything... but the idea is so obvious _someone_ must have tried it, surely?

    --
    [email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/

    ;; this is not a .sig
     
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  2. Stu

    Stu Guest

  3. Marcus Coles

    Marcus Coles Guest

    Simon,

    The original BMC mini used rubber for a suspension medium. The later ones, IIRC 1965 and later used
    the Hydrolastic suspension setup. In rallying and racing any hydrospastic minis I have seen were
    converted to a dry suspension.

    The interlinking of suspension does have some merit to contol roll, dive
    and squat in the automotive world. Such active systems do add complexity
    and to work well need microprocessor control and a host of sensors.

    I really don't see it being much use with the light weight, relatively short wheelbase and varying
    conditions faced by an offroad bicycle.

    That being said I'm sure somebody with time on their hands and some hose, double acting hydraulic
    cylinders and a couple of diaphramed air/oil reservoirs could have hours of entertainment.

    Marcus
     
  4. Werehatrack

    Werehatrack Guest

    On Tue, 25 Nov 2003 19:05:02 GMT, Simon Brooke <[email protected]> may have said:

    >So the question is, who has tried it and what were the results? I've done a quick web search but
    >haven't come up with anything... but the idea is so obvious _someone_ must have tried it, surely?

    Maybe not, with good reason.

    While it might seem logical to want the suspension to work that way, consider the effect in a
    *downhill* situation. I think the problem will be immediately apparent. Then consider that unless
    the system is disengaged during braking, it *accentuates* the forward weight transfer effect; this
    is not desired behavior at all.

    I had noticed the 2CV's tendency to exhibit unusual dive effects long before I knew why they were
    present. When I looked at the design, I understood why it wasn't more widely used.

    --
    My email address is antispammed; pull WEEDS if replying via e-mail. Yes, I have a killfile. If I
    don't respond to something, it's also possible that I'm busy. Words processed in a facility that
    contains nuts.
     
  5. Jobst Brandt

    Jobst Brandt Guest

  6. In article <[email protected]>, stu wrote:
    > http://www.whytebikes.com/whyte-2004/images/whyteprst1side72dpi.jpg Is it just me, or is there
    > something not right about the lacing on these wheels?

    They're the new VariCross(tm) wheels from VariSpoke, scheduled to be released in early April. Notice
    the hubs are 100% hidden in the picture in accordance with the VariSpoke pre-release product rules.

    Greg
    --
    Gregory S. Sutter "How do I read this file?" mailto:[email protected] "You uudecode it."
    http://zer0.org/~gsutter/ "I I I decode it?"
     
  7. Rick Onanian

    Rick Onanian Guest

    On Wed, 26 Nov 2003 11:04:10 +1100, "stu" <[email protected]> wrote:
    >http://www.whytebikes.com/whyte-2004/images/whyteprst1side72dpi.jpg Is it just me, or is there
    >something not right about the lacing on these wheels?

    Apart from there being something fundamentally wrong with the whole bike? It appears that it could
    have been done better if they had thought even _more_ outside the box. Although I can't visualize it
    at the moment, I imagine there must be a _much_ simpler solution to the idea of putting both shock
    absorbers on the frame, rather than the front in the fork.

    However, even so, doesn't the fork represent unsprung weight, which, IIRC, should be minimized for
    better handling? Or is that not true of bikes?

    Okay, back to the question: I'm no wheel expert, but the spoke lacing does appear a bit odd; I
    seem to see parallel spokes where I shouldn't, and such pairs aren't evenly spaced from other such
    pairs either.

    It does appear to have very low gearing, though. I like that in a gnarly off-road bike...especially
    if it also appears to weigh 50 pounds. ;) (The site says "Weight 27.8lbs fully built!")
    --
    Rick Onanian
     
  8. Stu

    Stu Guest

    > It's just you. That's conventional 23 x 3. How about exposing your doubts. What is it you
    > find odd?
    >
    > Jobst Brandt [email protected]
    Happy to take your word on it What I was looking at was how, on one half of the wheel you 3 places
    where 4 spokes cross almost at the same spot, yet on the other half of the wheel it looks nothing
    like that. I use 38 myself, so I guess I have just never noticed this before. thanks stu
     
  9. Peter

    Peter Guest

    stu wrote:

    >>It's just you. That's conventional 23 x 3. How about exposing your doubts. What is it you
    >>find odd?
    >>
    >>Jobst Brandt [email protected]
    >
    > Happy to take your word on it What I was looking at was how, on one half of the wheel you 3 places
    > where 4 spokes cross almost at the same spot, yet on the other half of the wheel it looks nothing
    > like that. I use 38 myself, so I guess I have just never noticed this before.

    I certainly find it odd that Jobst considers 23 spokes to be conventional and that you use 38. :) I
    think the appearance that's bothering you is just due to the perspective not being quite
    perpendicular to the wheel and lining up some left-side and right-side spokes.
     
  10. Stu

    Stu Guest

    > I certainly find it odd that Jobst considers 23 spokes to be conventional and that you use 38. :)

    lol oops I noticed Jobst's typo, lucky I didnt have a go at him about it hey lol

    >I think the appearance that's bothering you is just due to the perspective not being quite
    >perpendicular to the wheel and lining up some left-side and right-side spokes.
    >

    yes you are right, l went and had another look at my wheels and they do the same thing. l had
    throught about that before l posted but l didnt find the right angel. thanks again stu (who must
    look more carefully next time) and install his spell check
     
  11. Stu

    Stu Guest

    ">
    > I certainly find it odd that Jobst considers 23 spokes to be conventional and that you use 38. :)

    lol oops I noticed Jobst's typo, lucky I didnt have a go at him about it hey lol

    >I think the appearance that's bothering you is just due to the perspective not being quite
    >perpendicular to the wheel and lining up some left-side and right-side spokes.
    >

    yes you are right, l went and had another look at my wheels and they do the same thing. l had
    throught about that before l posted but l didnt find the right angel. thanks again stu (who must
    look more carefully next time) and install his spell check
     
  12. Stu

    Stu Guest

    ">
    > I certainly find it odd that Jobst considers 23 spokes to be conventional and that you use 38. :)

    lol oops I noticed Jobst's typo, lucky I didnt have a go at him about it hey lol

    >I think the appearance that's bothering you is just due to the perspective not being quite
    >perpendicular to the wheel and lining up some left-side and right-side spokes.
    >

    yes you are right, l went and had another look at my wheels and they do the same thing. l had
    throught about that before l posted but l didnt find the right angel. thanks again stu (who must
    look more carefully next time) and install his spell check
     
  13. Stu

    Stu Guest

    my posts have started not to appear????? l hope you arent all seeing this for the fourth time

    > I certainly find it odd that Jobst considers 23 spokes to be conventional and that you use 38. :)

    lol oops I noticed Jobst's typo, lucky I didnt have a go at him about it hey lol

    >I think the appearance that's bothering you is just due to the perspective not being quite
    >perpendicular to the wheel and lining up some left-side and right-side spokes.
    >

    yes you are right, l went and had another look at my wheels and they do the same thing. l had
    throught about that before l posted but l didnt find the right angel. thanks again stu (who must
    look more carefully next time) and install his spell check
     
  14. Jobst Brandt

    Jobst Brandt Guest

    Rick Onanian writes:

    http://www.whytebikes.com/whyte-2004/images/whyteprst1side72dpi.jpg

    >> Is it just me, or is there something not right about the lacing on these wheels?

    It's just you. That's conventional 32 x 3.

    > Apart from there being something fundamentally wrong with the whole bike? It appears that it could
    > have been done better if they had thought even _more_ outside the box. Although I can't visualize
    > it at the moment, I imagine there must be a _much_ simpler solution to the idea of putting both
    > shock absorbers on the frame, rather than the front in the fork.

    Ah, but you missed the feature. This bicycle uses the BMW patented anti-dive fork suspension
    with unequal length leading links. I don't know how important the feature is for bicycling, not
    having tried a suspension front end. It is a useful function for motorcycles that have large
    suspension travel.

    > However, even so, doesn't the fork represent unsprung weight, which, IIRC, should be minimized for
    > better handling? Or is that not true of bikes?

    It is probably untrue of bicycles about the same as wheel balancing. Weight of bicycle wheels and
    forks is small compared to rider weight and poses no significant inertial dynamics.

    > Okay, back to the question: I'm no wheel expert, but the spoke lacing does appear a bit odd; I
    > seem to see parallel spokes where I shouldn't, and such pairs aren't evenly spaced from other such
    > pairs either.

    As was mentioned, it's perspective.

    > It does appear to have very low gearing, though. I like that in a gnarly off-road bike...
    > especially if it also appears to weigh 50 pounds. ;) (The site says "Weight 27.8lbs fully built!")
    I he weight is probably correct.

    Jobst Brandt [email protected]
     
  15. Chalo

    Chalo Guest

    Rick Onanian <[email protected]> wrote:

    > >http://www.whytebikes.com/whyte-2004/images/whyteprst1side72dpi.jpg
    >
    > Although I can't visualize it at the moment, I imagine there must be a _much_ simpler solution to
    > the idea of putting both shock absorbers on the frame, rather than the front in the fork.
    >
    > However, even so, doesn't the fork represent unsprung weight, which, IIRC, should be minimized for
    > better handling? Or is that not true of bikes?

    That fork looks like a variation on the BMW "Telelever" design, whose main virtue is to be
    non-reactive to braking forces.

    http://www.encycleopedia.com/index.cfm?pid=23&edID=260&thePage=photos

    Chalo Colina
     
  16. Carl Fogel

    Carl Fogel Guest

    [email protected] wrote in message news:<[email protected]>...
    > Rick Onanian writes:

    [snip]

    > > Okay, back to the question: I'm no wheel expert, but the spoke lacing does appear a bit odd; I
    > > seem to see parallel spokes where I shouldn't, and such pairs aren't evenly spaced from other
    > > such pairs either.
    >
    > As was mentioned, it's perspective.

    [snip]

    > Jobst Brandt [email protected]

    Dear Jobst,

    Yeah, perspective and smaller brains. I hate all you guys who didn't have to go out to the garage
    and stare at a front wheel from different angles. I hate all optical illusions.

    Time to go out in the back yard and pretend to throw the stick for the dog to make myself feel
    smarter. Unfortunately, basset hounds lose interest in chasing sticks at about one year old, so I
    may have to borrow the neighbor's dog to tease.

    You guys should all be ashamed for trying to fool me.

    Carl Fogel
     
  17. Rick Onanian

    Rick Onanian Guest

    On 26 Nov 2003 10:56:46 -0800, [email protected] (Carl Fogel) wrote:
    >Unfortunately, basset hounds lose interest in chasing sticks at about one year old, so I may have
    >to borrow the neighbor's dog to tease.

    Just get a younger stick.

    >Carl Fogel
    --
    Rick Onanian
     
  18. Bruce Lange

    Bruce Lange Guest

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