2015 FSAE Rules

[Z]

To reiterate my main point here, there is a strong suggestion in the proposed Rules changes, and in many students comments here, that E-cars have an "unfair advantage" over the C-cars. This is supposed to be particularly so with the 4WD E-cars in the Acceleration event, and the recent FSUK-14 results might (!?) be used to support this view.

FSUK-14 results:
#. Team ......... O/A ... Acc.
===================
1. Delft(E) .... 856 ... 73
2. Stutt(C) .... 837 ... 38
3. KIT(C) ..... 828 ... 37
4. Zurich(E) . 827 ... 75
5. Monash(C) 821 ... 21

My argument is that if the above C-car teams learn how to do Acceleration properly, then there would be NO E-cars on the podium!

I will spell out how to do this in more detail in a few days, but meanwhile...
~~~~~o0o~~~~~

Stever95,

"I.....I......I...... Disagree."

The appropriate saying here is that "Opinions are like a...holes. Everyone has one."

Would you care to support your opinion with some quantifiable reasoning?
~~~~~o0o~~~~~

Troy,

"... intuition would suggest that combining lower inertia losses and a higher tractive potential for an equivalent power level would give higher acceleration, all other things being equal, no?"

Your intuition is wrong because your premisses are wrong. Your main mistake above is the second one. I'll give the numbers later.
~~~o0o~~~

Thijs,

"In other words, there must be enough grip off the line to lift your front wheels in the first place.
You basically agreed to that, by saying we should assume a start line acceleration of 2.5g."

Yes, as all the Toothless-Hillbillies know! And the "front-wheels lifting" kind of makes your front-motors redundant, doesn't it? (Except, as noted before, for regen-braking, and also good for very low grip conditions where there is little rear weight transfer.)

"You still haven't told me where you do your tire shopping."

I buy whatever is readily available, but then use it correctly. I note that Delft has some rather special looking Apollos? They look good.

"This is how sticky a drag strip is:
https://www.youtube.com/watch?v=x5wQajhGaeI"

And on that sort of drag strip (which is only like that near the start) a Top Fueler takes ~3.8 seconds for ~400m (Edit: STUPID Z!!! See later post). That is an AVERAGE of more that 5.5 Gs, over the full distance! I am asking you to aim for LESS THAN HALF that number, and only for a very brief period at launch (numbers later....).

"I don't remember seeing cars in a circuit race class lifting their front wheels.
...
If you want to make a point about how slow and boring current FSAE car designs are, and how stupid 4WD is, please point out a single race car that can go around corners ..., and that accelerates quicker to 60km/h than the fastest 4WD electric FSAE cars."

You really should get out more. Or use Google?

Last time we had this discussion all the student "experts" were saying that no racecar engine could ever make the 30 kW/sq.cm of restrictor area that I said was a reasonable upper limit. I then had to spend five minutes on Google to find the countless engines that do, in fact, make close to that number, with some claiming quite a bit higher.

You are being LAZY. Please do your own research.
~~~~~o0o~~~~~

Daniel,

"Regarding the weight distribution ...
[Premisses ->]
If you only look at acceleration then yes, you want to design a static weight distribution as close to the driven [rear] axle ...
However, there are 4 dynamic events in formula student, where 3 out of 4 require some sort of lateral force creation. ...
With minimal load on the front axle, minimal total lateral force is created needed for cornering. ...
Then you have the issue of balancing the car for these 3 dynamic events. ... slight hickup ... oversteer ...
[Conclusion ->]
So yes, [with 50:50 WD] you take a slight hit on 75 points from acceleration, but you gain a lot more on 50+150+300=500 points."

Try not to take this personally, because the majority of your fellow students also think the same way, but the above reasoning is really STUPID.

Firstly, your "theoretical" reasoning is based on vague, qualitative, hunches. There are NO NUMBERS! If you do your calculations/simulations correctly, with NUMBERS, then you will see how wrong the above reasoning is.

Secondly, you have clearly not done any "empirical" research (ie. checking the "prior art", aka "benchmarking"). If you did, then you would be aware of the countless racecars that have a significant rear weight bias, with larger rear-tyres than fronts, and can BOTH accelerate hard, AND go around corners fast. See below for examples.

Sadly, your sort of reasoning is all too common amongst people who like to call themselves "Engineers" (I have heard it too many times in the past). NO correct use of theory, and NO checking of the empiricism. But worse yet, NO shortage of arrogance along the lines of "I are an Engineer, so I know all about these things. And if I can't do it, then it can't be done!".
~~~~~o0o~~~~~

Steven,

"[Maryland car]... as far as lateral force generation goes, if I remember correctly, there weren't many SAE cars faster around a skid pad, or scca autocross.
... transient response and the length required to get the weight distribution could be improved with a custom, short engine/driveline ..."

Yep. It works well, and squashing it all up and making it a bit lighter would work even better...
~~~~~o0o~~~~~

Jay,

"Minimal axle loading may create minimal lateral force, but there is less mass to move. See the Deltawing concept."

Again, yes.

Ben Bowlby's DeltaWing concept is driven primarily by the goal of half-mass + half-power = half-fuel-consumption + same-laptimes. To a large degree this is achieved via better aerodynamics. But along with the aero (or as a result of it?) the DW has ~28F:72R weight-distribution (with 75% rear aero), and it goes around corners just fine!

Interestingly, before it ran all the Engineering experts said "IT WILL NEVER WORK!!!". They said this even though the earlier 1980's AAR Eagles that inspired the DW worked really well! Ah, ... experts!
~~~~~o0o~~~~~

Bottom line for now, next year's FSUK C-cars should aim to win Acceleration outright, and push the E-cars off the Overall podium. So stop carrying on like sooky little girly-boys and wingeing that the E-cars are not playing fair...

The empirical evidence is out there, and numbers coming soon...

Z

[JurrienK]

To reiterate my main point here, there is a strong suggestion in the proposed Rules changes, and in many students comments here, that E-cars have an "unfair advantage" over the C-cars. This is supposed to be particularly so with the 4WD E-cars in the Acceleration event, and the recent FSUK-14 results might (!?) be used to support this view.

FSUK-14 results:
#. Team ......... O/A ... Acc.
===================
1. Delft(E) .... 856 ... 73
2. Stutt(C) .... 837 ... 38
3. KIT(C) ..... 828 ... 37
4. Zurich(E) . 827 ... 75
5. Monash(C) 821 ... 21

My argument is that if the above C-car teams learn how to do Acceleration properly, then there would be NO E-cars on the podium!

I will spell out how to do this in more detail in a few days, but meanwhile...
~~~~~o0o~~~~~

Z, it is noteworthy that both the electrical cars in the top 5 had problems getting a good time in endurance. Zurich got 6 laps in which they lost 30 secs per lap (3 minutes, equal to about 90 points on FSUK) and Delft also lost about 2.5 minutes (equal to about 70-75 points) due to some problems.

[Mumpitz]

I can't get this image out of my head when visualizing Z's weight distribution concept
http://images.thesamba.com/vw/gallery/pix/1025010.jpg
Low CG (boxer motor)
High rear weight dist.
No unnecessary technology

Don't take that as an insult to the idea by any means either. As an FSAE alumni with a few rotary motors laying around and an adapter kit for a VW bug box... craigslist is a dangerous place for the post FSAE junkie.

[tromoly]

Z,

May I suggest spending more time around the drag strip when the track is being prepared. I have worked at a multiple-time record-holding (both ET and MPH) drag racing facility for 8 years, the track surface is sprayed the entire quarter mile in PJ1 Trackbite, per NHRA guidelines.

I'm not buying the Top Fuel comparison. I am personally interested in seeing your math that says an FSAE car on an unprepared surface can accelerate at half the rate of a Top Fuel dragster with a power/weight ratio >5200 hp/ton on a much higher bite track surface.

ADDED: Also, the quarter mile record is 4.58 seconds in a wheel-drive car as seen here (*Language Warning* http://youtu.be/57-DDGblOJw), you are most likely thinking of the 1,000-foot record of 3.7 seconds (http://www.nhra.com/points/national-records.aspx). Unless you're thinking of the 3.58 quarter mile set by a Hydrogen-Peroxide rocket car at Santa Pod a number of years ago (http://youtu.be/0lnEjOuQGBc), that really isn't relevant 'cause rockets aren't FSAE-legal.

[Dylan Edmiston]

FSUK-14 results:
#. Team ......... O/A ... Acc.
===================
1. Delft(E) .... 856 ... 73
2. Stutt(C) .... 837 ... 38
3. KIT(C) ..... 828 ... 37
4. Zurich(E) . 827 ... 75
5. Monash(C) 821 ... 21

My argument is that if the above C-car teams learn how to do Acceleration properly, then there would be NO E-cars on the podium!

To quote someone I highly regard on these forums:

Would you care to support your opinion with some quantifiable reasoning?

I would like to see support from your statement that the combustion cars are NOT doing accel "properly". On top of that, support that the electric cars ARE doing accel "properly".

[MCoach]

For the people that are not swinging their lower members around here....



With reference to the proposed rules I don't think anyone has bothered to reference to the 2014 rules. Throttle only seems to affect forced induction applications.
Check page 66: http://students.sae.org/cds/formulas...fsae_rules.pdf

T15.9 Throttle Body – The committee is considering changing the position of the throttle body to place it
downstream of the compressor on turbocharged and centrifugally supercharged engines. The restrictor would
remain upstream from the compressor. Naturally aspirated engines would not be impacted by the change.

Drive by wire includes switch (hopefully not, because we already have a driver kill switch)
T15.7 Drive by Wire Throttle – The Committee is considering that drive by wire throttles can be used on
Formula SAE cars if they include a form of the brake plausibility device which is currently required for
EVs. Feedback on this topic and whether you would like to adopt a throttle by wire throttle would be
appreciated.

As a student from Kettering, and having by far the most cost efficient car, this is in my interest.
T15.10 Design Event – The committee is considering including the objective of value in the design event
objectives. This is to make it clear to all participants that a cost effective car which is well executed should be
able to score well in the design event. This will result in the design event being judged on the three main
objectives of Design for Performance, Design for Value and the knowledge of the team members. The
committee hopes that this will change the perception of the design event so that it is clear that a large budget is
not a prerequisite to winning the design event.
T15.11 Cost Event – The committee is considering a major revamp of the cost event such that it addresses
product / component engineering issues including design for cost, design for manufacturing, design for
sustainability and the life cycle of the product. Students will be expected to have an appreciation of all areas of
relating to product / component engineering which will be important in their engineering careers. The
committee would appreciate feedback and prop

[Swiftus]

I'll bite on on this one MCoach.

Would a kind person please explain why engines with different types of induction should be treated differently with regards to how their power is being limited?

"T15.9 Throttle Body – The committee is considering changing the position of the throttle body to place it
downstream of the compressor on turbocharged and centrifugally supercharged engines. The restrictor would
remain upstream from the compressor. Naturally aspirated engines would not be impacted by the change."

[MCoach]

Jay, glad you've asked. I went looking and dug up another relevant document.

From this 2013 document, this is the exact reasoning from the rules committee:

http://www.fsaeonline.com/content/Ch...tion%20web.pdf

"B8.6.1:
Moving the throttle body downstream of the centrifugal boosting devices will avoid
creating a vacuum in the compressor housing when the throttle is closed which draws oil
past the seal resulting in visual engine smoking and potential plug fouling. No
performance benefit will be gained by centrifugally boosted engines as any air leaks in
the throttle body will reduce the amount of air going into the engine at wide open throttle.
The restrictor will continue to choke the flow through the compressor limiting power as
with the current configuration.Placing the throttle body downstream from the turbocharger will put it in the normal
position used in current production vehicles thus making the turbo a realistic design
option for the teams. Turbocharging of production vehicles is widely expected to grow
significantly worldwide in the near future so providing an opportunity to incorporate this
technology into FSAE performs an important part of the educational purpose of the
competition.
Naturally aspirated engines would keep the same layout (sequence) as currently
required because of concerns that a leaky throttle body downstream could allow
unregulated extra airflow to the engine if it was placed downstream of the restrictor.
Positive displacement boosted engines would continue to use this layout because oil
seal leakage is not an issue and there is no motivation to change the design."

[Swiftus]

Thanks MCoach.

I don't see how a 'leaky throttle' is a defense though. At FSG the scrutineers will put their hand over the intake to physically plug the engine. If the engine doesn't immediately die, they will ask you to go full throttle as they plug the intake. This should make the engine stop faster... unless there is a 'leak'.

This same process could be performed no matter where the throttle body is located within the system and no matter what kind of induction the engine has equipped.

Why not simply place the restrictor after the throttle body and the turbo?

[Pat Clarke]

Oh Jay, think about it :-)
You want 300 horsepower turbo FSAE cars?

On second thoughts, sounds good to me :-) :-)

Pat