**Installment 3**

I remember this from a discussion about dynamic weight transfer.

Ignoring the effects of the human body, and chassis and tire reactions, here's how I look at it- on an Oval track:

There are 4 points of the kart where weight is transferred from the kart to the ground. Those 4 points are the connecting points of the hubs/rims.

If you draw this out on paper.(Looking down from above the kart). Connect the dots and you'll have a somewhat warped rectangle.

Scale the kart and write down the 4 corner weights.

By knowing your scaled weights in a horizontal plane you can find the approximate weight centers in both the x and y positions. If you don't know how to do this, ask.

The points for our discussion are;

"X" is Front to Rear,

"Y" is Left to Right (Driver side to Engine side),

"Z" is the vertical aspect.

Next,

Locate the weight center between the LF and RF (this point is XFront).

Locate the weight center between the LR and RR (this point is XRear).

Locate the weight center between the LF and LR (this point is YLeft).

Locate the weight center between the RF and RR (this point is YRight).

Now we are going to start our kart observation from a position already racing in a straight line, shortly after corner exit.

When the kart is accelerating forward, weight is transferred backwards, the X value will move towards the rear, the Y value will not change, and the Z value will rise upwards slightly (due to weight transfer and aerodynamics).

Next, the kart will decelerate slightly due to friction incurred from the front end tire grip while turning in at corner entry- the x value will move forward, the Y value will not change, and the z value will drop slightly. So, at corner entry the X value will decrease (usually to the apex) then increase with acceleration towards corner exit. The Y value will move to the Right until it reaches the point where maximum G's occur (apex), then it will begin transitioning back towards the Left towards corner exit. The Z value will roll slightly downward to the Right at corner entry, then back upwards from the apex to corner exit.

We've just looked at all of the 2D points in motion from a 3D aspect.

Now...Backing up a square, look at your original x,y,z values.

X and Y form 2D points on one plane, while the point for Z is above the X and Y plane.

Look just at the motions in X and Y for one lap.

Next, draw a line (A) from the weight centers of XFront to XRear in their static positions. Note how the location of the midpoint of line A moves (due to the motions along the X and Y plane) for that one lap. Next, draw a line (B) from the weight centers of YLeft to YRight in their static positions. Note how the location of the midpoint of line B moves (due to the motions along the X and Y plane) for that one lap. The intersection of A and B is our moving "Anchor point", ZZ (ZZero). Calculate the VCG and you'll have a "ZS" value (ZStatic). As the Z position rises and falls, we will have new values also (that moving 3D point is the Virtual "M"). Now look at the vertical rise and falling motion from point ZS for one lap. Next, draw a line (C) from our Anchor point (ZZ) vertically to the ZS position. Next, draw form any imaginary spherical radius with the center at ZZ and the outside radius at ZS.

In closing;

While racing around our oval track, the positions of ZZ and ZS will move, and can be calculated. For any track at any given speed, corner radius, and banking, G-Force values can be determined. If I can determine the G's and know the grip available at the tires**, I can calculate a maximum speed that I can put a kart through a corner before it will get loose and spin out (**Yeah, I know...there's a whole lot to the tire science, so let's not even go there!). If I can know the numbers, I can lock in on chassis analysis a little tighter. When I find "good numbers" for my chassis, I have a baseline to work from at any track, on any surface. Tracking this kind of stuff is how I learned to dial a chassis in AFTER it already "feels good".

Being fast for 10 or 20 laps is pretty simple, but when it's 50 or 100 laps, no amount of tire prep will beat selecting the proper tire duros and getting the chassis "right".

(That was tough to express on paper...hope it all came out straight!)

Y only changes due to g-forces during cornering- when motion is NOT is a straight line. Like I said, sometimes its difficult to write what I think and see in my mind.

I envision Z as rising and falling because its anchor (rotation) point during forward acceleration is the rear axle, and the center of the mass, "Z" (basically the driver's body) is forward of the rear axle. Due to the forces incurred during acceleration and aerodynamic lift, the nose gets "lighter" and it raises. I may be wrong. I'm not a genius, but that's how I envision it. It could also be that the rotation downwards behind the axle presses down so hard that it leverages the front up when pivot