Rules Reduction Recommendations

[Dunk Mckay]

Measuring any part of the wheel, rim or tire, is always going to be a challenge. Flexibility of the tire or different setups, should not be too much of a concern, because the requirements must be met at all times regardless of wear, pressure, expansion, setup, etc. So you'd have to leave a margin of error (a realistic engineering challenge is to know how much margin you need).

Measuring width ways will always be a challenge, because of camber, which is why I've use terms like "innermost". So you would, as you say, take a plumb line to the the ground.

Wheelbase measurement is the same as current rules. The trouble with wheel centers is that it either requires specialized equipment, to make sure you are properly centered, and would be affected by toe angles. Additionally some competitor's wheels don't really have any centers to speak off, so that would be a real struggle.

What would potentially be interesting would be to come up with a simple and cheap design for a measurement tool, with four cornered adjusters that sit on the ground and tighten to the point of contact around each tire, attached to a graduated frame that sits flat under that, from which you can read all the required measurements. The specifications could then be sent to all teams so they know exactly how they are going to be measured. But I think that could be a bit elaborate, and would face resistance form some event organizers.

[Z]

Dunk,

Following from the discussion on the FSUK 2016 thread...
... I also posed the question of the relevance to the competition of the Alternative Frame rules. Unless someone can come up with an example of a reasonably well designed car from the last 3 years, that made good use of the AF rules, I would motion that they not be included.

And on the FSUK-16 thread you wrote:

... the AF section ... has always seemed like a bit of a waste of space, and a big section of the rules that you have to read, that doesn't seem to add anything to the competition. ... So much so that FSG does not accept them unless they have already passed scrutineering at a previous FSAE event.

I have always maintained that if you're making a space frame car, it's because you've gone down the road of simplifying your design process. That being the case, why would you then over-complicate things by using the AF rules?

I'm sure people will say there could be some elaborate design that has some clever benefit, but doesn't work under the normal rules. But realistically I don't see that happening often enough (or at all) for it to be worth it.

I wish I had more time to cover the many other issues regarding "changing the Rules", but right now I want to stress that the AF section has the "seed" of a good set of frame rules within it, albeit buried under much nonsense.

Considering the 2017-18 version of the Rules on the FSAE website, there are ~56 pages of "Part T - General Technical Requirements", followed by 8 pages of "Part AF - Alternative Frame Rules". I agree with you that these ~64 pages can be greatly shortened. I reckon ten pages could comfortably cover it all.

But, and importantly, I see most of the larger "Part T" as the redundant part, mainly because much of it acts AGAINST the "education of young engineers". The tube-frame rules in Part T, and much else there, is very PRESCRIPTIVE.

In essence, these Rules tell the students "Thou shall build thine frame (and the rest of the car...) as detailed here. Thou MUST NOT THINK about it. Thou must SIMPLY DO WHAT WE TELL YOU!".

The end result is that countless tube-frame cars that I have seen have a side-view very similar to that shown in Figure 7 on page 44. This is a piss-poor design for torsional stiffness, because the shear forces are carried by long, narrow, triangles. I repeat, BAD DESIGN! Nevertheless, many Teams blindly copy this design because, in essence, they are told to do so and it is thus the easiest option. No education happening there...

By contrast, the "AF" section presents a set of FUNCTIONAL requirements. Something like, "Thou shall build thine frame ... so the top of Main-Roll-Hoop can sustain a force of F kN, in X,Y,Z direction, with less than D deflection ... [and with similar functional requirements imposed on other parts...]".

Unfortunately, the "AF" section then goes and spoils this good approach by mandating that these functional requirements are "proved" via the least reliable method known to man (or, at least, by me), namely FEA! I am sure that it is this onus on the students to "prove via long-winded correspondence with the Officials..." that ultimately turns Teams away from the AF section.

The madness of all this is that an FS/FSAE frame is really a very small thing. The easiest way to really prove that it meets the functional requirements, is to really build it, and then subject it to real, full-scale, tests. That is, build it, load it up, measure the deflection, then check for any permanent damage!

Of course, if the students want to do a year's worth of FEA first, or perhaps a week's worth of hand calcs to help predict if their rough-draft frame is in the ball-park, then fine, let them. But the only "proof" they really need provide to the Officials, namely that their frame meets the functional requirements, is a real-world test at scrutineering. Bring car to comp, let the Scrutineers load it up, and if no failure, then good-to-go.

I have a whole lot more to say about how these tests could/should be done. But very briefly for now, a few more tests than currently in the "AF" section would be a good idea, and they should be done somewhat differently. Just some examples:
1. The MRH tests (acting both forwards and rearwards) should be "impact tests" (think Izod/Charpy pendulum-test), not just "static" load tests.
2. I would like to see the floor given an upward push acting on a small area located anywhere under the driver. Say, something like a tennis-ball being pushed upward with force 300 N (~30 kg, or more?).
3. The Side-Impact requirement should reflect the fact that the other car's IA (presumably the bit that is T-boning your car) can be as small as 10 cm high x 20 cm wide (x 20 cm long). That is, the current 25 cm diameter "impactor" is much too big. A minimum size IA should not easily fit between SIS tubes. So do a real "side intrusion" test with an "impactor" of frontal-area = minimum-size-IA, and acting with some reasonable load (perhaps half load expected of a collision, to test integrity, but not damage the car?).
~o0o~

Again, much more to say, but for now I should counter the expected criticism that all the above frame load-testing is going to be too much for the Scrutineers to do at comp.

Firstly, not all tests have to be done on all cars. The Scrutineers can simply wave through the cars with frames that look like railway bridges, and only pick the cars with fragile looking MRHs to undergo the "MRH-Pendulum-Impact-Tests". Or, if flimsy looking floor, then test it, and so on.

Secondly, consider the current "functional" requirement that prevents cars rolling over in SP, AX, and Enduro (or at least minimises the number of rollovers). This Rule is simply that the cars must pass the "Tilt-Table-Test". This Rule requires that the organisers build a rig that can carry out the TT test on all the cars, and do it reasonably quickly (hence some hydraulically powered rigs, etc.). But imagine how many extra pages would be added to the Rule Book if this simple real-world test was replaced by a long-winded "prescriptive" list, that mandated every detail of how masses must be distributed in order to keep the CG low wrt track-width, blah, blah...

To show how few words are needed for the functional requirements of "rollover stability" and "fluid-system integrity", here they are IN TOTAL.

"T6.7 Rollover Stability.
T6.7.1 The track and center of gravity of the car must combine to provide adequate rollover stability.
T6.7.2 Rollover stability will be evaluated on a tilt table using a pass/fail test. The vehicle must not roll when tilted at an angle of sixty degrees (60°) to the horizontal in either direction, corresponding to 1.7 G’s. The tilt test will be conducted with the tallest driver in the normal driving position."

and,

"T8.5 Integrity of systems carrying fluids – Tilt Test.
T8.5.1 During technical inspection, the car must be capable of being tilted to a forty-five degree (45°) angle without leaking fluid of any type.
T8.5.2 The tilt test will be conducted with the vehicle containing the maximum amount of fluids it will carry during any test or event."
~o0o~

Note also that the "Cockpit Template" rules are a good example of functional requirements, and hence are, IMO, GOOD RULES. There is no long-winded mandating of tube diameters or wall thicknesses, or where and in which direction the tubes must be, but simply that sufficient empty space be provided for the template to pass through.

Similarly, your above suggestion of "keep-in volumes" are also good functional requirements. (I called these "Green-Allowable-Zones" earlier in this thread. I have quite a few suggestions for how to more reliably specify these GAZs, but maybe later...)
~o0o~

The above Tilt-Table tests, Cockpit-Template tests, and so on, are real-life, proof-of-the-pudding, tests. I suggest that "frame integrity and safety" be also specified and tested in a similar way. The Rules should guarantee safety in a realistic way, and not just hope for it via the current, long-winded (~50 pages!), prescriptive recipe.

Maybe more later...

Z

(PS. "Keep-In-Zone" dimensions would be better referenced from a horizontal-plank (maybe 3 m long x 0.5 m wide) raised up from under the car and supporting it. Then all X,Y,Z dimensions are referenced from this plank using squares, etc. Picture "build-table".)

[BillCobb]

I'd rather see mention of two wheel lift than "roll" for rollover stability. That means a front and a rear and in both directions. You mean it can't roll at all ? Just a teeny weeny bit? And somebody WILL roll one at low speed with just the right dynamic maneuver.

[Dunk Mckay]

Z,

Those are perfectly good reasons why the AF frame rules present a better engineering challenge. But if no one has used them effectively for years, it is also unlikely any team will try to use them effectively in future.

Any team that is up for taking a more challenging approach to their chassis design, is almost guaranteed to take the monocoque route. My thoughts were that frame rules, now, are essentially for teams that are aiming for a simpler design process. In such cases the gains from using an AF frame (if they get it right...) are relatively minor. But the hr gains from being able to throw together a legal frame design quickly, and then spend their limited time and human resources on the rest of the car are significant. Based on those assumptions, the AF rules become somewhat redundant. Interesting as they are.

There are also lots of teams that use the standard rules and build something very far from the "prescribed design" you mention. Usually adding in many unnecessary members that do nothing to improve their design. So in some cases, even using simple rules that seems to basically tell you what to design, some teams fall short.

In essence, while the AF frame rules may present the opportunity for the best possible frame design, I do not expect anyone to ever make use of them. I know that's not a great reason for getting rid of them. But it's an easy 8 pages to lose, that will make little if any difference to the series.

[NickFavazzo]

Food for thought, a recent uwam car essentially took the "prescribed" minimum chassis and built that, as we didn't have a huge need for the torsional rigidity. I wasn't on the chassis team for that but that is largely what I remember.

Another thought. Why do we need mandated minimum wheelbases and track widths? too big and it is just plain slow, too small and you physically cant fit things in. We struggled to make a minimum wheelbase car with the cbr engine. Roll over stability etc is tested elsewhere.

Regarding aero, what about giving a max height and width relative to track/wheelbase and that is it. What is inherently wrong with covering the wheels?

[Dunk Mckay]

Many teams to the same. Nick. I When I designed my uni's first space frame for 5 years I essentially put in the points for suspension attachment and those mandated by the rules and connected the dots. I added a small number of additional members to meet the stiffness target we had set. In testing we found we didn't really need the extra stiffness, so the following year they built the same design (tweaked) without those extra members.

The reason for mandating a minimum track is so as to have a fixed value for the width of the "green box" as Z puts it, above 250mm ahead of the front wheels, as well as for rear wing width. In keeping with the "nothing in front of the front tires above 250mm rule. You either have to specify that distance relative to the tires (which recent history has shown is just not a realistic solution), or specify a minimum track, equal to the maximum width of the >250mm front green box.

Minimum track is justified as it limits how much of the cars ends up hanging over the front wheels. The 700mm rule does this IF it applies to all parts of the car (currently only applies to aero). But many people argue that a big safety improvement would be to mandate that pedal boxes be located behind the front axis. This would mean most cars having much longer wheelbases (closer to 1700-1800mm). But front end collisions are not really a safety issue on current track layouts, so it hasn't been adjusted. It's mostly a case of "if it ain't broke" for the 1525mm rule.

Covering the wheels has a few downsides, some minor, some less so.
- It's one more thing to have to remove for judges and scrutineers to see what's underneath. (in fact it's 4 more things)
- They essentially would have to be made from carbon and molded, which makes them expensive and time consuming to manufacture. Giving even more advantage to teams with bigger budgets and more team members/resources.
- It's something else to break, increasing the unreliability of cars.
- Additional rules regarding the strength of mounting said fairings would be required, otherwise they risk falling off due to aero loads and being flung in all directions by the wheels (including at the driver's neck).
- Formula Student has always been an open wheeled formula. It's tradition, having wheels fairings would change the aesthetic of the event. That may not seem important to some, but to others it is. The exact same reasoning applies in Formula 1.

[JT A.]

In the spirit of this discussion, why is there a minimum wheelbase rule at all?

[JulianH]

Why do we need such complicated rules with keep out zones?

Can't we just say "no part of the car besides the main hoop can be higher than XXXXmm" + "no part wider than XXXXmm" + "driver egress must be unobstructed by parts" + "power ground effect is prohibited"?

With this we perfectly set the maximum achievable downforce and everything can be measured without reference to other car parts.

Why do we need the 75% rule? Why not set a minimum and maximum track width and people can what they want to do?

[Dunk Mckay]

I think part of the idea with this was to simplify the rules, while keeping things similar to what they currently are.

There are good reasons for limiting things like having wheel fairings, as I've discussed above. A simple max height and width, also doesn't allow for taller roll hoops, while still restricting aero to "safe" limits (or more competitive limits for teams that can't afford/manage big aero packages).

The current keep-out rules came about because of people complaining about the ambiguity of the term "open wheeled racer."

The 75% rule, as far as I can tell restricts aesthetics (so they look like people expect race cars to look), but also prevents Reliant Robin type situations, where teams build what are as good as 3 wheelers, that might have some awesome aero opportunities but are incredibly unstable in roll.

I feel my proposal, or something similar, would be simple enough. Easily made into diagrams (which I'm still struggling to upload).

[NickFavazzo]

...

Covering the wheels has a few downsides, some minor, some less so.
- It's one more thing to have to remove for judges and scrutineers to see what's underneath. (in fact it's 4 more things)
- They essentially would have to be made from carbon and molded, which makes them expensive and time consuming to manufacture. Giving even more advantage to teams with bigger budgets and more team members/resources.
- It's something else to break, increasing the unreliability of cars.
- Additional rules regarding the strength of mounting said fairings would be required, otherwise they risk falling off due to aero loads and being flung in all directions by the wheels (including at the driver's neck).
- Formula Student has always been an open wheeled formula. It's tradition, having wheels fairings would change the aesthetic of the event. That may not seem important to some, but to others it is. The exact same reasoning applies in Formula 1.

Too be fair they are all pretty petty reasons.
- one more thing to remove, its not different from other bodywork, its up to the team to remove anyway, not a big job.
-we made ours a few years ago from scrap carbon, using a styrofoam mold and masking tape as release, then just spent time sanding them before painting them ourselves. cheap, easy and looked great.
-something else to break, what about all the extra components associated with conventional suspension? way more parts with wishbones than our beams. Trivial reason.
-falling off due to loads, thats just engineering design and crappy designs should be picked up in scrute. If it breaks it breaks = black flag. Its in the teams best interest to properly design and manufacture the part. I would be more worried about a wing coming off...
-Screw tradition, its an engineering competition, open wheels are just plain inefficient. Our wheel pods a few years back were pretty close to legal and achieved the intended purpose.

Not having a go, I just don't like dismissing ideas so quickly.