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F.5.6.1 The Chassis must include both a Main Hoop and a Front Hoop.
F.5.6.2 The Main Hoop and Front Hoop must be Triangulated into the Primary Structure with structural tubing.
The Triangulation must be at a node in side view for:
a. Bends in side view
b. Bends in front view below the Upper Side Impact Structure F.6.4, F.7.5
F.5.6.3 Roll Hoop and Driver Position
When seated normally and restrained by the Driver Restraint System, the helmet of a 95th percentile male (see V.2.1.1) and all of the team’s drivers must:
a. Be a minimum of 50 mm from the straight line drawn from the top of the Main Hoop to the top of the Front Hoop.
b. Be a minimum of 50 mm from the straight line drawn from the top of the Main Hoop to the lower end of the Main Hoop Bracing if the bracing extends rearwards.
c. Be no further rearwards than the rear surface of the Main Hoop if the Main Hoop Bracing extends forwards.
F.5.6.4 Driver Template
A two dimensional template used to represent the 95th percentile male is made to the following dimensions (see figure below):
A circle of diameter 200 mm will represent the hips and buttocks.
A circle of diameter 200 mm will represent the shoulder/cervical region.
A circle of diameter 300 mm will represent the head (with helmet).
A straight line measuring 490 mm will connect the centers of the two 200 mm circles.
A straight line measuring 280 mm will connect the centers of the upper 200 mm circle and the 300 mm head circle.
F.5.6.5 Driver Template Position
The Driver Template will be positioned as follows:
The seat will be adjusted to the rearmost position
The pedals will be placed in the most forward position
The bottom 200 mm circle will be placed on the seat bottom where the distance between the center of this circle and the rearmost face of the pedals is no less than 915 mm
The middle 200 mm circle, representing the shoulders, will be positioned on the seat back
The upper 300 mm circle will be positioned no more than 25 mm away from the head restraint (where the driver’s helmet would normally be located while driving)
Explanation
F.5.6.1 The Chassis must include both a Main Hoop and a Front Hoop.
The Main Hoop and the Front Hoop are the only two members on the chassis that really have to be bent. They're primary purpose is to protect the driver from contacting the ground in case the car rolls over during a dynamic event (while the car is driving). The idea is that the roll hoops are strong enough to not bend or break even if this roll over happened at high speeds with high impact forces.
UNCA 2023 Front Hoop
UNCA 2023 Main Hoop
There must be triangulated tubes supporting the roll hoops as part of their integration into the chassis. There are specific required support members that will probably end up serving as these triangulated members (more on that later) but there are some special cases for triangulated that need to be covered here because they will not be covered in these other rules.
a. If there are bends in the side view, there needs to be a triangulated tube at the bend node (a tube supporting the bend)
Tube with bend and no triangulation Added triangulation tubes (red)
If there was a bend in a tube (in side view), there would need to be extra tubes added (red) to make sure that bend node is fully triangulated.
b. If there are visible bends in chassis members (in the front view) that sit below the the Upper Side Impact Structure, they need to be triangulated (in side view) at the bend nodes. This means that the support for these bends must appear triangulated when looking at them in side view (you are drawing the triangle in side view)
First I will show you the Upper Side Impact Structure and the region below it, then I will show you what it would look like if there were "front view bends" in this region. We will also look at what triangulating this would mean.
The red highlighted tube is the Upper Side Impact Member. Any bent tubes in front view below this need the additional triangulation.
This is the front view of the chassis. These green members I have drawn in are bent in the front view because they do not create a straight line (linear slope) in front view. I would be required to add triangulation members (red). They do not look triangulated in front view, but the rules dictate they must appear triangulated in side view.
I have rotated the "bent tube from the front view" example in to an isometric view, and then a side view. The red tubes appear to triangulate this tube if we view it in side view, which is what the rule is reffering to when it says the bent tube has to be triangulated in side view.
F.5.6.3 Roll Hoop and Driver Position
When seated normally and restrained by the Driver Restraint System, the helmet of a 95th percentile male (see V.2.1.1) and all of the team’s drivers must:
a. Be a minimum of 50 mm from the straight line drawn from the top of the Main Hoop to the top of the Front Hoop.
b. Be a minimum of 50 mm from the straight line drawn from the top of the Main Hoop to the lower end of the Main Hoop Bracing if the bracing extends rearwards.
c. Be no further rearwards than the rear surface of the Main Hoop if the Main Hoop Bracing extends forwards.
There is a Driver Template used to evaluate rules compliance for the cockpit of the car. The template is a bunch of circles constrained to be spesific distances from each other that represent the shape of the driver. The template needs to fit in the car in such a way that the circle representing the helmet is
a. At least 50 mm from the imaginary line connecting the two Roll Hoops (blue)
b. At least 50 mm away from the imaginary line that connects the Main Hoop and the base of the Main Hoop Bracing (in our case, the Main Hoop Braces follow this line) (pink)
c. If the Main Hoop Braces are not behind the Main Hoop, the driver's head should not extend past the back of the Main Hoop.
All of these rules may seem specific and arbitrary, but they make a lot of sense if you think about what they are aiming to achieve. The goal of the Roll Hoops is to protect the driver in case the car rolls over. They want a minimum clearence for the Roll Hoops because they are the only thing protecting the driver's head from impacting the ground if something goes wrong on the track.
Driver Template that represents the driver
F.5.6.4 Driver Template
A two dimensional template used to represent the 95th percentile male is made to the following dimensions (see figure below):
A circle of diameter 200 mm will represent the hips and buttocks.
A circle of diameter 200 mm will represent the shoulder/cervical region.
A circle of diameter 300 mm will represent the head (with helmet).
A straight line measuring 490 mm will connect the centers of the two 200 mm circles.
A straight line measuring 280 mm will connect the centers of the upper 200 mm circle and the 300 mm head circle.
I know you've seen it, but here it is again:
The driver template is a physical thing you will need to build (out of cardboard or something) to represent a standard driver they expect your car to be able to accommodate. It's really imortant that you use this as a reference in the CAD to validate the cockpit rules of the chassis before moving into the build phase of the car.
F.5.6.5 Driver Template Position
The Driver Template will be positioned as follows:
The seat will be adjusted to the rearmost position
The pedals will be placed in the most forward position
The bottom 200 mm circle will be placed on the seat bottom where the distance between the center of this circle and the rearmost face of the pedals is no less than 915 mm
The middle 200 mm circle, representing the shoulders, will be positioned on the seat back
The upper 300 mm circle will be positioned no more than 25 mm away from the head restraint (where the driver’s helmet would normally be located while driving)
These driver template positioning rules are pretty self explanatory and shown in the graphic they provided, but I decided to annotate it a little bit just to make the whole thing more digestable.
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