Could somebody PLEASE explain the relevance and use of cross-weight.
Steve
I am forwarding 2 bits of information I have lifted off the net and from
the file ncarrw.wri >>>>>>>>
From NCAR's Rookie Setup Guide:
Cross Weight or wedge is a way of preloading the RF and LR springs and
varying the amount of weight carried by the left rear tire and the right
front tire. Cross weight affects the cornering ability of a car through
an entire turn. Generally start with this at 50% or zero pounds. You
may want to save cross weight for race adjustments for the most part.
Increasing cross weight tightens up the car, reducing oversteer.
Decreasing cross weight loosens up the car, reducing understeer. A
combination of around 60% cross weight and higher stagger and stiff right
front spring will heat the tires up quickly for a qualifying run, but
will wear out the RF early and will not be suitable for a race setup.
[begin wedge discussion]
~Subject: INSIDER TECH input (WEDGE)
"From the Shop"
I am pleased to have been given the opportunity to share some lines
with you in what is the first installment of the "Insiders" tech-section.
We'll cut right to the 'meat' here in this opening segment.
Living on the 'WEDGE'
---------------------
Probably one of the most used but often least understood terms in the
sport of NASCAR Racing when watching weekend broadcasts would be the
infamous item known as WEDGE. Wedge and Cross Weight are synonomous
entities.
First, some facts. Don't let the term "cross weight" mislead you into
thinking you are adding more physical weight to your race car, you're
not. You are merely redistributing weight already present in your
machine. The only means of increasing your vehicles's weight is by
physically adding more to it.
We'll assume here that you are relatively happy with the rest of your car
set-up, as this is only a small piece of the 'set-up puzzle'. Also my
discussion will lean toward more 'real-world' situations and will assume
that the program has been modeled adequately ;-). I will attempt to not
re-hash stuff found in all of our manuals where I can avoid it.
Obviously one should read or re-read that section as well.
Adjustments to wedge essentially alters two things on your race car:
1) The redistribution of weight present in your car (commonly presented
in terms of adjusting weight percentages from the RF to the LR, though in
reality you can adjust from any corner to suit your needs, but we'll keep
to the game)
2) Adjusting the 'ride-height' of your racer.
Since this is not a physics lesson (and frankly, I'm by no means a
physics major ;-)), the ride-height is just simple words refering to the
differences in the center of gravity of your vehicle (The lower you can
get your center of gravity the more your car will 'stick' to the track...
this is why often times you can barely see the driver in a fine-tuned
stockcar at your local track as that it upwards of 200 lbs of weight
<driver> that is placed in the car; they want to get it as low as they
can)
As mentioned in the manual, wedge adjustments are performed via enclosed
adjusting shafts or rods in the suspension/spring assembly. These
adjusters can be tightened or lossened by way of a wrench from the top
(or under the hood for the front) at each corner of the car. (Hey! An
adjustment that can be made to a car and you may not even have to get
your hands dirty! :-) ). Basically when one corner is tightened, you
distribute an extra portion of the total weight to that point. In doing
so you effectively remove weight from the opposite corner (percentage
speaking). You also have adjusted the 'ride-height' of the chassis where
the weight has left and been added. The chassis will have been raised
where it left and lowered where it has been added. (A good example of
wedge/ride-height would be to have a look at some of your local "Street-
Stock" division racers on the track... ever notice how the RF-end seems
to be sticking up or protruding skyward on some of the vehicles? This is
a good indication the wedge/ride-height has been added/ lowered
(respectively) to the LR :-)). The ideal scenario, generalizied in the
game, would be the ability to systymatically add and remove weight from
all corners of the car and maintain a desired ride-height that you
wanted. (ie. you could add 5 lbs to the RF, take 5 lbs from the RR, add
5 lbs to the LR and take away 5 lbs from the LF. You have effectively
added about 40 lbs of wedge to your racecar, also maintaining your ride
height.... but this isn't a Math lesson either ;-) but there are formulas
for this exercise).
** Rules of thumb:- MORE WEDGE = TIGHTER CAR/UNDERSTEER
LESS WEDGE = LOOSER CAR/OVERSTEER
In setting up your race car for the simulation, remember a few items
when contimplating your cross-weight adjustments:
1) Your car will ALWAYS be 'loose' on coldish tires, nothing can
be done about this.
2) In general, remember you have +/- 20 gallons of fuel in which to
keep your car semi-driveable. I personally prefer a decent handling car
in the mid to early portion of a fuel load and pray for a caution as the
tires begin to go away. This translates into an extremely loose setup at
the start in terms of wedge but becomes quite comfortable after a few
gallons are exhausted. This will depend on driving styles, of course,
and work in conjunction with the other settings you've elected to drive
with.
3) As your car lightens due to fuel consumption (remember, each
gallon used is about 7 lbs. off your rear weight or nearly a full 1% of
rear bias!), you'll begin to develope a 'push' or understeer. Eventually
it'll want into the wall with more force then you can counter it with
without severly slowing down. This effect acts as if more wedge has
suddenly been added to you car.
4) For decent qualifying starting points, I suggest doubling or
even tripling your wedge settings in order to hold 'er to the track with
the limited warm-up period (ie. 20 lbs. race wedge, I'd look at 50 to
60, maybe more, for a qualify wedge setting)
Here's some other weight related tid-bits for you to ponder as we make
our way through the venues this IWCC-season. Guaranteed you'll be
referring to these for some advice (I think!) as they're what I apply to
my first time at a new track.
[Again, these are based on 'real-world' occurances, exercise extreme
caution when trying these at home :) ]
1) Increase REAR weight and you improve your turn exit speed, while
making the car looser in the middle portion of the turn.
In other words, improves forward speed in corners
2) Increase SIDE weight (left) and you improve your cornering
ability in the mid-portion of the corner.
3) Too much wedge = a colder LF tire running temperature.
4) Not enough wedge = a colder LR tire.
5) Banked courses = add wedge, decrease stagger
6) flatter corners = remove wedge, increase stagger.
7) Wedge does NOT alter the %'s weight on the portions of the car,
that reamins constant. The only way the %'s change from different
aspects of the car (left or rear) is by physically adding more weight or
removing it. Example: 52.4% left weight will stay that way no matter
what adjustments you make to the cross/wedge weight.
Well, that's it for "From the Shop" this time kids. Hope something in
this passage was found interesting or helpful. I can attempt to explain
certain things in more detail if anyone has any questions on the subject.
Also, if something doesn't sound quite right, please correct me if I went
astray somewhere. I can always haul out the video tapes again and double
check things, this was going more from experience and memory. Until next
time, apply full-throttle pressure and don't repaint any of the walls.
<off>
Chris Goucher
Northern Lights Racing team member
#2, Alpine Lager Beer Ford-Thunderbird
[go...@basmod.bio.ns.ca]
--
**************************** Michael E. Carver *************************
Upside out, or inside down...False alarm the only game in town.
mcar...@teleport.COM
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