2015 FSAE Rules

At the design review held at FSG the past week, Pat Clarke and Owen Carless confirmed some of the 'rumors' about the new rules for 2015. I'll sum up from what I heard, but in details I might be wrong.

Aero rules:
The rules for the aerodynamic devices such as wings and diffusers will be tightened again. According to the 2 chief judges, a few years ago the aero rules were loosened so that more teams would venture into aerodynamics. This was done because the rules commitee was of the opinion that too little research into aerodynamics was done. They now feel that the time is there to tighten the rules again and make it a bit harder to create a beneficial aero setup. In what shape or form these rules are was not discussed.

4WD electric rules:
There will be a drop in power for 4WD electric cars. How much was not specified and is not known yet.

Design Scoresheet rules:
Pat Clarke and Owen Carless made the 'announcement' that FSG (maybe FSAE? not sure) was looking into evolving the design scoresheet to better reflect current rules and regulations, especially considering the electric vehicles.

I'm only paraphrasing here, so I might have one or two exact details wrong. It would be nice if either Pat Clarke or Owen Carless would comment on this :)

THs (on the contrary of common belief) have also benn using internet a lot these days, so lots of info is available if you look into the right places.

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Originally Posted by Z

...Now a forward Fx force at the rear-axles pushes the car's CG upward (through the up-to-front sloping n-lines), and by action-reaction, the rear-tyres get forced down onto the road. So more than 100% of car weight is possible on the rear-tyres.

But this increase is only brief, because it only lasts while the car's CG is accelerating upward. So best to start with the CG quite low, so that the pro-lift can last for as long as possible. And you have to find the right balance. Too much pro-lift and you get a nanosecond of great launch, but then the car jumps TOO high, grip is lost, wheels spin..., slow ET. Not enough "wheelie" or "pro-lift" = slow launch, and Team Toothless is laughing at you (although you have beaten most other FSAE teams).

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Pro-lift forcing an "action/reaction" increase of Fz is a highly dynamic matter because of rotational dynamics (car wants to "pop a wheelie" and has a significant rotational inertia around that axis that works FOR you). Moreover, THs usually opt for 100% anti-dive (or close to that value), because exceeding it by far (having too much pro-lift) might plant the tires very hard in the first few milliseconts but eventually the nose gets back down and tires begin to slip, especially in very powerful drag cars. This is much dependant on track conditions, whether is slippery or not, and available power, so most drag cars are highly adjustable in terms of anti-lift. Moreover, in the matter of nose lift and coming down, front springs and especially dampers play a significant role as well. I would suggest to anyone interested to search the web for a Mr. called Bill Shope...

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Originally Posted by Big Bird

Oh, and if you are putting down Presentation Event presenters - I did it like 6 times for RMIT...

As you were...

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I guess you had to do something if you couldn't fit in the car!

Then again the RMIT guys probably wheeled you into the presentation with you halfway into a rant, then wheeled you out when you were a little bit past halfway through a rant. The judges would have been both astonished and bewildered. Must have been worth a few points.

If we are on the marketing presentation, how would you propose that you maximise the early launch phase of powerpoint to ensure you finish with the most number of words conducted during the event? And does the ridiculously high centre of gravity you possess enable you to exceed over 100% weighty words per sentence?

Kev

What do you mean I couldn't fit in the car? I did skid pad and presentation in 2003. Unfortunately I got the two confused. For my presentation I found myself talking in circles a couple of times, so I turned it around and went in a different direction. I then went off course, meandered around in circles a couple more times, to find that I had actually gone nowhere and I was exactly back where I started. It was all over in just over twenty seconds.

My fastest skid pad time was ten minutes, which was followed by three minutes of questions.

As for launching the presentation, I never found squatting at the back end to be all that helpful. You have to understand, we were running a smaller, lighter presentation than you guys - fewer words, much less weight to them, but less chance of choking when under full power. And I remember our presentation sounded a bit flatter than yours too - but then a single presenter always sounds flatter than four inline...

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"If the [16" high] CG is causing such massive weight transfer front-to-back, wouldn't that have a dramatic effect on cornering performance as well?"

NO, no, no. Not if you SET-UP the car to suit the different Events.

So for SP, AutoX, and Enduro I would definitely set-up the car with LOWEST POSSIBLE CG, and whatever else is required for good performance there.

But for Acceleration (remember = 75 points!) you could set-up the car with 4" of ground clearance. The Rules say you must have AT LEAST +/-1"of suspension travel, so 1" bump and 5" droop should be OK. (I don't have Rules here just now, but IIRC "shims, spacers..." and other adjustments are allowed.) So getting a 12" CGH up to 16", JUST FOR Acceleration, should not be hard. And not really necessary... (see below).

Or, easier, you can have a special "booster seat" for the driver that has a very thick squab. Given that most seat-backs slope backwards at about 45 degrees, I reckon you could easily move the driver up 4" and back 4". But check Rules on this...

More importantly, with CGH = 12" (0.3 m) and 60%R on a 60" WB (ie. ~0.6 m + 0.9 m = ~1.5 m) means 2 G gives you 100% on the rear. With same CGH, 2.5 G has you "popping a wheelie". However, you become power-limited a bit after 2 metres (see graph), so the Gs drop off and the nose comes down. Also any front-wing aero should start to act by this stage, pushing the nose back down.

So aim for as-low-as-possible CG for "normal running", and with 60%R you only have to bump it up to 0.25 m to 0.3 m for the Acceleration event.
~o0o~

Z

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T1.2.3 The vehicle must maintain all required specifications, e.g. ride height, suspension travel, braking
capacity (pad material/composition), sound level and wing location throughout the competition.

Someone's already thought of the super adjustable ride height. Sorry to burst your bubble.
I'm intrigued at the rest of the post though. Thanks.

Fair call MCoach. It is a long time since I've read the rules from front to back. You guys are much closer to the coalface than I these days.

However, my next step if I was confronted with such a rule /constraint would be to seek out definitions, and see if there is room for movement. Ride height must not change - so what is ride height? The distance between the lowest point on the main body and the ground? is it the whole floor plan of the car? Can we design a mechanism that leaves the lowest part of the floor at "ride height" level, and the rest of the car lifts upwards? Maybe an engine/drivetrain tray that can be adjusted up and down for different events.

What does "all required specifications" mean - has anyone asked that question?

The point is that there could be a whole range of interesting and alternative solutions floating around in the margins of our interpretations of the rules. I would point to the recent UWA cars which have a very interesting interpretation of "Suspension". Engineers are very adept at finding reasons to not be different. If the mindset changes from "that's not possible" to "lets see if it is", then things can become very very interesting.

Quote:

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Originally Posted by MCoach

T1.2.3 The vehicle must maintain all required specifications, e.g. ride height, suspension travel, braking
capacity (pad material/composition), sound level and wing location throughout the competition.

Someone's already thought of the super adjustable ride height. Sorry to burst your bubble.
I'm intrigued at the rest of the post though. Thanks.

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The only real required specification in the rule regarding Ride Height, CoG etc. is passing the tilt table.

I think the more interesting question would be how many teams actually change anything on their car during competition, and why they don't.

I see very few changes being made in between events. The top teams tweak a bit, the middle teams catch up on sleep, and the back-markers are still gluing together bits of carbon. I'd be very curious to see how extending the time for dynamic events would change this, as I know we were always caught between changing set-ups and prepping the car for endurance with our four-ish man team. Also not having dynamics a 30 minute walk from the paddock (at least at MIS and Fontana) would help.

P.S. I'm finding it increasingly amusing that the experienced alumni, has-beens, and old guys around here tend to agree more with Z than the still egotistically fragile young budding engineers he's trying to help.

"How dare you insult our theoretically perfect car! Last year GFR won with this same design so it will certainly work for us too!"

Having been there myself, I hope some listen. I wish I had.

At one point in FSUK, changing car setup between dynamic events was encouraged. That contradicts the 'T1.2.3 The vehicle must maintain all required specifications, e.g. ride height, suspension travel' statement.

Is this a rule inconsistency, or does FSUK cover it in the event rules not the FSAE tech rules?

Regards, Ian

Does that rule not simply mean that it must continue to meet all the rule requirements? In the case of setup surely maintaining the minimum +/- 1" of travel is all that's required, otherwise anything that's adjustable, and passed scrutineering as such can be adjusted. No?