IRS discussion: was Re: Noise and vibrations.......

[mr.utility at highstream.net (David Utley)]

Some, it helps some...  :-0

I don't think I know enough to comment intelligently, so I will refrain (the 
crowd cheers!)..

David Utley

Quoting Dan Bubb <jdbubb@ix.netcom.com>:

> First, I'd define independent suspension:
> If you can move one wheel/tire assembly from droop to bump without changing
> the camber or toe of the
> wheel on the opposite side of the car, then that would be independant.
> I would define a beam axle as the two axles being contrained relative to each
> other in six
> dimensions i.e they can't move relative to each other in 3 orthogonal planes
> and they can't change
> angles relative to each other within those three planes.
> (I'm trying to make this easy, but it doesn't seem to be coming out that
> way!)
> Anyway, the Scirocco rear suspension meets the definition above. If you
> remove the spring/shock
> assembly from one side of the car then you can freely move that side up and
> down and see that the
> other side is uneffected.
> If the Scirocco rear suspension was a beam axle then moving one side up and
> down would change the
> camber of the other side. So, I guess the point is that just because a beam
> is used in its
> construction doesn't mean it has the characteristics of a classic beam axle.
> The Scirocco rear axle is really a simple version of a pure trailing arm
> suspension. ( as opposed to
> a semi-trailing arm like the 924/944 Porsche)  It has no camber or toe change
> from droop to bump. It
> is functionally no different from the twin beam concept that Julie proposed.
> The neat part is that
> VW incorporated both sides into one unit. The "T" cross section is stiff in
> bending in both a
> horizontal plane (to control toe during cornering loads) and in a vertical
> plane (to control
> camber), but because of it's open cross section is relatively weak in
> torsion. So, VW was able use a
> really wide base for the bushings to minimized toe change due to bushing
> deflection (roll oversteer)
> and at the same time incorporate some roll stiffness into the structure. It's
> a really neat design
> in its simplicity except for its complete lack of camber change to improve
> cornering.
> Almost all suspensions have some sort of interconnection from side to side in
> the form of a swaybar.
> That interconnection doesn't make the suspension not independant (at least
> according to my
> definition).
> Anyway, if you're looking to replace the "T" beam with a bar or tube there is
> a good chance you will
> increase roll resistance at the cost of a lot less stiffness to control toe
> and camber deflection
> due to cornering and bump loads.
> There's lots more to say about how the position of the beam effects camber
> change if anybody's
> interested.
> Hope all that was clear.
> Dan
> 
> 
> ----- Original Message ----- 
> From: "Calimus" <calimus@techography.net>
> To: "David Utley" <mr.utility@highstream.net>
> Cc: "Dan Bubb" <jdbubb@ix.netcom.com>; <scirocco-l@scirocco.org>
> Sent: Wednesday, March 17, 2004 6:43 PM
> Subject: Re: Noise and vibrations on the steering.. Solve one, find thereason
> for the other !
> 
> 
> > I knew this would happen, LOL.  I took the conversation off list, but if
> > you want to join in thats cool.  My viewpoint is that it's not IRS and I
> > kinda explained that a bit.  My basic idea is to replace the cross piece
> > of the rear beam with a torsion bar.  That would achieve IRS wihout
> > having to fab tons of new mounting points and all that happy stuff.
> > Just have to do some fabbing to the rear beam and bolt it back in the
> > same way it came out.
> >
> > William
> >
> > David Utley wrote:
> >
> > >Dan,
> > >  Now trust me, I am not trying to incite anything but friendly
> discussion,
> > >but you knew someone would ask...  How is it that it is independent, when
> it
> > >uses a beam?  Trucks (american) have an axle beam, and it is a rigid rear
> > >suspension, what makes the A1 cars different?
> > >
> > >David Utley
> > >
> > >
> > >
> >
> 
> 
> 
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David Utley
-----------
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