rec.autos.simulators

> in a time I should be doing completely different things, my mind can't
> help but wander back to car physics. Here's two questions that have been
> bugging me for a while.

> The first is the question of toe out/in at the front. It has often been
> said that a bit of toe-out at the front will destabilize the car,
> helping on turn in. I can't help but think that this should be exactly
> the opposite; when you turn in, the outside wheel begins to weigh up,
> meaning that you are making the tyre that points relatively more to the
> outside of the turn more ***, making the car turn in less. The way
> I see it, it is actually toe-in that should create better turn-in, as
> weighing the outside tyre which points more in the direction of the turn
> would in this case push the nose even further into it. Any ideas?

> The second question concerns oval stock car racing. There's always talk
> of inside and outside lines, and even real drivers don't take the
> outside-apex-outside line even when there is no cars on the inside. I'm
> not talking about restrictor plate races, as the cars don't even run at
> the limit there, but super speedways. In, say, Nascar 4, trying anything
> else than the geometrically ideal line will make you much slower. Is
> there generally more *** on the other lines that may make you almost
> equally fast in other lines as well, or am I missing something here?

> Enlighten me! :)

> -Gregor

> Indeed, but on the other hand it makes the outside wheel do less work
> than is necessary. If there is no weight transfer present (c.g. at the
> ground,

> > uh.  if you have cg at ground level, you'll still have
> > weight-transfer, no?

> Nope. Weight transfer is caused by the torque exerted on the car by the
> wheels - or specifically, the components of the torque that attempt to make
> the car dive or roll. If the CG is on the ground, those components are not
> present - hence, no weight transfer. Of course, like Gregor said, it's
> impossible for a car to have a CG on the ground or below it anyway.

> Think about a car that, for the sake of argument, has its body (and
> therefore its CG) below ground (no collision detection :-) In this case, the
> car would actually behave more like a boat: it would lean into the curve,
> and weight would be transferred to the inside wheels.

> > uh.  if you have cg at ground level, you'll still have
> > weight-transfer, no?

> Nope. Weight transfer is caused by the torque exerted on the car by the
> wheels - or specifically, the components of the torque that attempt to make
> the car dive or roll. If the CG is on the ground, those components are not
> present - hence, no weight transfer.

>Ah, there's an interesting aspect I haven't thought about! Basically,
>the torque produced by the turned outside wheel is much different than
>for the inside. It's the same reason why sometimes turning into further
>the spin will save your car instead of opposite locking.

>If the track width is wide enough, and the c.g. low enough, this effect
>just might be more than the weight shifting one, and probably there
>exists a geometry setting where the ammount of toe-in and out  is
>actually irrelevant under some assumptions. I'll need a pen and paper
>from this point on, but thanks for the clue!

>Cheers,

>-Gregor

> > > uh.  if you have cg at ground level, you'll still have
> > > weight-transfer, no?

> > Nope. Weight transfer is caused by the torque exerted on the car by the
> > wheels - or specifically, the components of the torque that attempt to
make
> > the car dive or roll. If the CG is on the ground, those components are
not
> > present - hence, no weight transfer. Of course, like Gregor said, it's
> > impossible for a car to have a CG on the ground or below it anyway.

> > Think about a car that, for the sake of argument, has its body (and
> > therefore its CG) below ground (no collision detection :-) In this case,
the
> > car would actually behave more like a boat: it would lean into the
curve,
> > and weight would be transferred to the inside wheels.

> At least for small outboard boats. Taller boats will have the CG above
> sea level and lean outwards when turning :)

> --
> Olav K. Malmin
> remove .spam when replying

> > > > uh.  if you have cg at ground level, you'll still have
> > > > weight-transfer, no?

> > > Nope. Weight transfer is caused by the torque exerted on the car by the
> > > wheels - or specifically, the components of the torque that attempt to
> make
> > > the car dive or roll. If the CG is on the ground, those components are
> not
> > > present - hence, no weight transfer. Of course, like Gregor said, it's
> > > impossible for a car to have a CG on the ground or below it anyway.

> > > Think about a car that, for the sake of argument, has its body (and
> > > therefore its CG) below ground (no collision detection :-) In this case,
> the
> > > car would actually behave more like a boat: it would lean into the
> curve,
> > > and weight would be transferred to the inside wheels.

> > At least for small outboard boats. Taller boats will have the CG above
> > sea level and lean outwards when turning :)

> > --
> > Olav K. Malmin
> > remove .spam when replying

> In a word: Ackerman.

> --Steve

> > I've also wondered about the origins of this.  Maybe the toe-in thing
> > started back when most cars had flexible steering systems and lots of
> > steering compliance?  This makes a good brain twister-- which way will the
> > front wheels point, with compliant steering and with the influence of
> > trail, tire aligning torque, etc?  I have not worked through this
> myself...
> > and depending on the front end geometry the answer(s) might differ??

> > There is one car that I did a lot of development testing on.  It was
> > a pretty strange car (sorry, no details today...), but it responded
> > very well to toe-out for straight-running stability.

> > On oval lines, here are two things that make it different from typical
> road
> > race cornering.  Just food for thought, not meant to be a complete
> > list<grin>:

> >  - When does the banking start getting steep, relative to the turn?
> >    Little point in turning in until you get help (download) from the
> banking.

> >  - Since ovals are usually run in one gear, sometimes keeping a
> >    peaky motor up on the torque curve (by going around the outside
> >    on the high line) may be quicker for the whole lap.

> > > Hi all,

> > > in a time I should be doing completely different things, my mind can't
> > > help but wander back to car physics. Here's two questions that have been
> > > bugging me for a while.

> > > The first is the question of toe out/in at the front. It has often been
> > > said that a bit of toe-out at the front will destabilize the car,
> > > helping on turn in. I can't help but think that this should be exactly
> > > the opposite; when you turn in, the outside wheel begins to weigh up,
> > > meaning that you are making the tyre that points relatively more to the
> > > outside of the turn more ***, making the car turn in less. The way
> > > I see it, it is actually toe-in that should create better turn-in, as
> > > weighing the outside tyre which points more in the direction of the turn
> > > would in this case push the nose even further into it. Any ideas?

> > > The second question concerns oval stock car racing. There's always talk
> > > of inside and outside lines, and even real drivers don't take the
> > > outside-apex-outside line even when there is no cars on the inside. I'm
> > > not talking about restrictor plate races, as the cars don't even run at
> > > the limit there, but super speedways. In, say, Nascar 4, trying anything
> > > else than the geometrically ideal line will make you much slower. Is
> > > there generally more *** on the other lines that may make you almost
> > > equally fast in other lines as well, or am I missing something here?

> > > Enlighten me! :)

> > > -Gregor