That would make a GREAT rule
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That would make a GREAT rule
1.) Endurance starts with the fastest cars and works backwards. As they finish, design finalists are re-evaluated. If for some reason a finalist wasn't able to run auto-cross, use an educated guess based on skid-pad and accel times to slot them in so they're finished with endurance by lunch. If they didn't finish accel, skidpad, or the finalist honestly qualified in the afternoon, find new design judges.
2.) Fix the design event. I've said it before and here it is again. It should go something like this: "Here's a picture and load analysis of a perfect hub. Here's the compromises we had to make and why. Here's what is actually on the car." Design judge will evaluate student on knowledge of "perfect" hub and whether or not compromises are reasonable, INCLUDING cost and manufacturing ability of the school. I really like the aforementioned "Engineering Event" since oversized rod-ends in bending are never good design, but there are certainly cases where they can be a perfectly acceptable solution (ever try to build a budget car that needs to be easily serviced in a third-world country? We aren't all Germany here folks...)
3.) All schools are required to hold their FSAE teams in the same regards as their football teams in terms of marketing, performance, funding, and continual improvement.
1) I don't like a "reverse grid" in Endurance. Spectatures will just leave, nobody watches the middle pack anymore it's really sad.
We had that in Spain once when they ran C class from slow to fast and then E class from Fast to slow. After the Top 5 E-Cars finished Endurance, everybody left. That is really uncool for the slower teams and reduces that "magic moments" of a Final 5.
I know that this is the "show part" of FSAE but I, especially as an alumn, like this part :)
I actually don't think that "finishing Endurance" is necessary for a Design Event.
All failures that we had in Endurance are not really related to car design but were mostly human error or a buy-part getting killed:
FS Italy 2009: That was not really E85...
FSG 2010 somebody forgot to lock the battery packs correctly
FSUK 2012: We had a faulty bearing in the gearbox
FSG 2016: Set wrong tire pressure
So yes, we had like 4 DNFs out of 20-ish Endurances. But was our "engineering capability" better in the 16 other events? I doubt that... (of course you can argue that "better engineers" would have designed parts better so that it is not possible for stupid humans to make mistakes, but the "same design" was used in the other events as well but it was just more properly handled)
2) Fix the Design Event. Sure. I like it. I always tried to judge the knowledge of the students about the parts that they designed. I scored a team very high that had a bad Aero design but they knew why it was bad and had just limited resources and could show that their money was spent better on other stuff of the car. That is good stuff "already" in the Design Event.
I think Alumni of FSAE make for better judges that the typical Automotive Industry judges because they are of course more impressed by the fancy laser sintered upright...
3) We are not all USA here folks... Universities in Europe don't have "sports teams" and they don't give a cr.. about any of their student projects.. they like the free publicity of a World record or a Title at FSAE but otherwise, no support at all.
FSUK
I agree that a reverse grid kills some (okay, a lot,) of the fun in watching endurance, but seems like a better compromise to me than design finals before the race. Really I'd like to see an extra day added back in to the competition if for no reason other than allowing teams proper time to set-up their car for each event rather than having to use the same set-up for accel and skid-pad. A parc-ferme system could be used to force teams into only making minor and quick suspension adjustments rather than trying to rebuild things they should have sorted weeks prior. In addition you wouldn't have to juggle tech and static events.
Also, some sort of allotment for simple minor repairs during endurance would go far, but is virtually impossible to define. It's done in Baja, so not impossible. Maybe something like you get one replacement tire, a handful of zip-ties, and can reconnect electrical connectors/toggle main power so long as the car is able to exit the track and drive to the repair area under its own power. 2 minute penalty regardless of how quickly you preform the fix. One stop only.
I agree with most of your ideas, except for allowing extra time for setup changes between skidpad & accel. There is enough time already, if you have the adjustments planned out and have practiced them once or twice. My last year as a student I changed damper settings, tire pressure, camber, wing flap positions, ride heights, front & rear toe between skidpad and accel. Other years we were more disorganized and unprepared, and we could only manage to change tire pressures and wing flaps. But in my opinion, that's the way it should be. Teams that come prepared, and designed a car that is quick to service / adjust, get to take advantage of it. Teams that are unprepared and designed bad adjustment systems have to run the same compromised setups for both events.Quote:
Originally Posted by Alumni
If anything the rules should do more to reward quick adjustments & penalize teams that can't. For example, change skidpad so that teams only run it in 1 direction. Each team is told which direction when they enter the dynamic area, and they have 5 minutes to change their car setup before they have to push the car in line and stop working on it. It rewards teams that 1) Understand asymmetric vehicle setup and can think outside the typical FSAE box to optimize their car for a certain direction 2)Designed a car with quick & easy adjustments, and 3)Were organized & prepared enough to practice the setup changes before the event.
I don't disagree, my thinking is more along the lines of nudging teams in the direction of doing so. I could have worded it better.Quote:
Originally Posted by JT A.
Throwing a wrench in the works for some events as you mention could be interesting as well. I'm not sure what events you could add (split-mu braking anyone?) but it'd be cool to see some more options that competitions could choose from like baja. Announce which events you'll run a month before competition.
A little preview of what you can do with eight horsepower.... https://www.youtube.com/watch?v=KFku5vz9EXY
It won't go to Lincoln this year for logistical reasons.
Charles,
On a similar note, the simplicity, speed, and insanity of Outlaw Karts have captured my heart recently.
https://www.youtube.com/watch?v=j8MBIK1V06cts
Charles,
I especially like the vibrant shade of brown you have chosen for the paint job! :)
Your video certainly shows that quick laps on twisty tracks are more about corner speed than horsepower.
Can you give us some overall specs of the kart, perhaps to help students doing overall concept simulations?
For example (just in round numbers):
1. Overall Mass (with or w/o driver), and Rear%.
2. Track-width, Wheelbase, and CG-Height.
3. Engine Capacity, Power (8 hp, but at crank, or wheel?), and Peak-Revs.
4. Overall Gear-Ratio (crank/wheel), and Rear-Tyre-OD.
5. I assume Aero-DownForce (CL.A) is close to zero, but any idea of CD.A?
Students can then plug these numbers into their simulator (or download something like OptimumLap), and then try to justify the need for a ~100 hp turbocharged-tyre-shredder to power their car!
Students can assume same tyre-Mus on both types of car. Or, more realistically, a higher Mu on the LIGHTER, smaller-engined car.
Z
MCoach,Quote:
Originally Posted by MCoach
Some specs on these would also be good.
Better yet, bring one to Lincoln!
Z
They are very popular with the top level national racers when they have a spare moment to do so.Quote:
Originally Posted by Z
They are also very popular with drivers trying to advance into sprint cars as they handle very similarly.
Specs:
Mass: Minimum kart and driver weight is 450lbs (204kg) total (with fuel).
Track width: adjustable from about 38-46" (965 - 1168mm), depends on kart manufacturer
Wheelbase: adjustable from 41-43" (1041 - 1092mm)
Rear Gear : 13-15 tooth drive gear, 23 - 75 tooth driven axle gear
Engine: Open class, 550cc 2 or 4 stroke engine (both have same displacement), typically make 85-100hp (63 - 75kW) at the crank. Peak rev is typically 8-12k rpm.
Tires: different for each corner and variable from slick or treaded and 11x5-6 to 12x9-6 (diameter x width - wheel diameter)
Brakes: One rear brake on the rear axle and one left front wheel. The right front does not use a brake.
Frame: standard oval racing offset chassis with a cage made from 3/4" x 0.083" tubing. The cage is sprung from the kart via 4 valve / die springs at each corner.
CG:I'd estimate the CG is 55% left side weight, and about 12-18" (457mm) high due to the wing height, driver height, and upright driver seating position.
Aero:
CLA and CD are hard to quantify but there is also attention to CLS that is needed.
Most people are familiar with coefficient of lift and coefficient of drag, but many are not familiar with coefficient of side force or literally Fy from aero forces which this generates a lot of.
Either way, it is a single element giant wing with asymmetrical end plates. Throw some numbers in simulation.
The wing is adjustable in angle of attack via a push-pull cable from the driver and is directly mounted to the cage. This in effect means that the chassis is unsprung mass, but the wing and roll cage is sprung mass.
Interestingly changing these springs change how the karts fundamentally handle.
Cost:
The top-of-the-line open kart chassis is available for about $4500 without motor. Race built motors tend to run $1-5000 depending on the quality and reputation.
Used, these karts can be found for $2-8000 with motor.
Z,
Quick stats on the kart, in English units because that's what my tape measure uses.
1) With driver, 150# front, 222# rear, 60% rear. Without driver 182#.
2) Front overall width 45 1/4", rear overall width 51 1/2", wheelbase 41", c.g. height estimated at 6". Measurement of CG height difficult due to small value and unwillingness to get dumped on my head on my garage floor.
3) 12.5 cubic inch displacement, clutch engagement at 3300 RPM, 8 horsepower (crank on pessimistic dynamometer at Briggs and Stratton) at 5500 RPM, redline 6100 rpm.
4) Single reduction by chain drive, 15t driving sprocket concentric with crankshaft, 59t driven sprocket concentric with rear axle. 34" rear tire circumference WHEN STATIONARY.
5) With downforce-generating bumpers and sidepods removed, I lose about 15# and am about 0.5% slower than without. CdA is about 5 square feet, estimated from speeds at a different track.
MCoach, Charles,
Thanks for the specs.
I would really like to see students simulating the above cars, on typical Autocross tracks, to compare laptimes with the super-uber-mini-F1-style cars of their dreams.
Then, of course, the students should also factor in Cost, build-time, and reliability, to see which is the more sensible direction to go ... assuming they WANT TO WIN!
Hmmm..., thinking, thinking... idea!!!
~o0o~
Claude,
How would you feel about hosting a "Virtual FS World Championship"?
Teams would logon to your website and use OptimumLap to design a car, which then sets a laptime on a given Autocross track. Only one entry allowed per registered FS/FSAE Team.
The tricky bit is that each car is also assessed by a secret formula that gives it a score for "Cost/Build-time/Reliability", with lower score = better. This discourages the Teams from choosing minimum mass + maximum power +++, etc. Typically, a 100 hp engine is much more costly (and raises minimum selectable mass), than a 10 hp engine. Uber-aero-numbers have longer development time than middle-of-road numbers, so are more "costly" because less testing time, and so on. But exact details of the formula are not given, reflecting the fact that even professionals struggle to predict exact costs and finish times when "pushing-the-envelope".
Then, at the end of the year, or end of a given "competition period", the secret "Cost" score is added to each entry's laptime in seconds, and lowest total score is crowned "OptimumG's Virtual FS World Champion"!!!
The Cost-formula is now revealed, to show students how stupidly expensive they were in their design decisions. The next year (or next comp-period) the track is changed, setting a different "problem" to be solved, and the "Cost" formula is tweaked to reflect those different conditions.
This idea may need thinking through? Maybe..., build it, test it, improve, repeat?
~o0o~
MCoach,
BTW, yes, those aero-sideforces certainly are useful. I see some big opportunities here that no team has yet exploited.
(Big hint: Flat-plates are nowhere near as good as cambered-aerofoils. And vertical cambered-aerofoils that can switch camber from left to right-side, as needed, are ancient prior-art.)
Z
Erik - such a virtual FSAE thing already exists: VI-Grade Virtual Formula
Here's an outline for the "OptimumLap Virtual FS Champion 2018"
Suspension - Whatever's light. It's not modeled anyway so it just needs to connect the tires to the chassis and have them somewhat straight and vertical. All aluminium A-arms since it only needs to do one lap.
Chassis - Rules minimal spaceframe, mild steel
Engine - 80kw and flat torque from 2000-10000rpm, because I said so. Weighs 30kg.
Aero - Literally drives upside-down at 20km/h
You get the point.. without extensive validation (how? who?) this would be unfeasible. Who's going to check that the CAD density for steel isn't half what it should be.
One way you could make it work is to provide formulas for each part e.g. Engine is 0.75 kg/hp. You can buy a 1kg weight decrease for $1000
Of course once you settle on an acceptable set of numbers teams will cry out "Our engine is 20% lighter and 20% more powerful and we bought it for $1000 off Ebay".
Chances are something like this would be won by a simple script to search all possible configurations for the fastest/cheapest car - might take a week to compute but expect a couple of teams with the same setup
Maybe this still has value in showing there's more than one way to win, but it would require a lot of work to make an evenly balanced competition.
Tim W,
Looks like I'm six months late.
Nevertheless, that VI comp seems similar to what I had in mind. Except it seems to be E-car only (I just had a quick look?), and it misses the important "Cost" component/discouragement (see below).
(And what happened to Adelaide? You came dead last!)
~o0o~
Tim P,
Read my paragraph beginning with "The tricky bit ...", and continuing with "This discourages the Teams from choosing minimum mass + maximum power +++ ...reflecting the fact that even professionals struggle to predict exact costs and finish times when "pushing-the-envelope"...".
The SECRET Cost formula I suggested is aimed directly at Teams who start the year dreaming of,
... with these Teams invariably ending the year with a non-running car that scores zero dynamic points (ie. the core theme of this thread).Quote:
Engine - 80kw and flat torque from 2000-10000rpm, because I said so. Weighs 30kg.
Aero - Literally drives upside-down at 20km/h
So, to do well in the Virtual contest, Teams have to be REALISTIC (perhaps even conservative) in their choice of mass, horsepower, aero, etc, lest their unexpected, but exorbitant, Cost-overruns cripple them.
Z
Z,
How do you propose setting up this magic formula?
Historical data? - doubt it would be any use as I'd judge the skills of the team more important than their car concept.
A table of parts with costs and probabilities of failure? Still assumes that each team is essentially the same.
FSAE is more execution-dependent than design-dependent in my opinion. Take all the aero-13" wheel-cbr600 teams and plot their results. And all the Emrax-spaceframe-no aero teams. And probably the AMK 4wd, practically-drives-itself teams. I doubt you can find a winning concept, at least in AUS.
There are plenty of simple cars that fail as well as complicated ones. I doubt there's a real correlation in Australia.
From 2016 Aus scores. Teams that score higher in Cost tend to finish more dynamic events. However, R^2 = 0.23, and I'd wager that can be explained by cost penalties and cost task. Remove Western Sydney Uni, and the R^2 goes down to 0.18
Attachment 1182
I think the lesson is that teams need to select a concept which is achievable with their budget, organisational skills and engineering skills. I'm sure Delft and AMZ etc could build great brown go karts, but i doubt they'd be more reliable, and definitely wouldn't score more points.
If you know you can pull off an ambitious concept, do it. If you don't - don't. That's what I think teams are lacking.
For example a certain team that designed half an EV, toured a 2015 car and built a 2016 car, another which built a (purple) EV and an IC, and one that built a (red) IC with wings and a fancy gearbox. All of them didn't do as well as they wanted to.
Tim W,
I have looked a bit more at the VI-Grade comp, but it is taking me ages to download some of the stuff. So ... can you fill in some of the details?
The VF2017 Rules/Regs seem straightforward enough, only 4 pages! :)
The idea of competing in Accel, Skidpad, and Autocross events is also good, because it makes it harder to "optimise" a single vehicle design.
I also agree very much with the inclusion of a FUEL EFFICIENCY score (essentially a "Cost" on OTT designs), because it again makes it harder to find an "optimum". Just chasing maximum horsepower or biggest wings becomes counterproductive.
Question: I noticed that there are "cone penalties", so is this a "Driver-In-the-Loop" simulation? Something like the video games (GTA?)?
If so, then great, because that is the type of VD sim that I am now developing (slowly, in spare time). But my general proposal for a Virtual FS comp could also use the more conventional "computer drives the car" simulator.
I would also be interested to hear any other interesting details of how this went.
Anyone from Adelaide care to comment?
~o0o~
Tim P,
I sense much confusion in you.
It would help if you listen to (or read) what others have to say, and then CONSIDER such, before blurting out comments like "...doubt it would be any use...".
But you did get this bit right.
Which is the theme of this thread.Quote:
I think the lesson is that teams need to select a concept which is achievable with their budget, organisational skills and engineering skills.
Selecting "the right concept" is also the reason for doing good simulations, in that it is pointless aiming for an exotic, super-spec, car, when the sims show that a much simpler and quicker-to-build car, is very nearly as fast. And it uses less fuel, so it wins on points anyway!
Z
Dear Z,
I took the numbers of the Briggs Kart and did a Optimum Lap sim. I assumed a pretty flat torque curve with a maximum of 11 Nm. Coefficient of friction longitudinal was 1,5, lateral was 1,6. I estimated the downforce at 0,3 mē ClA.
The competitor was an average European Top10, all-wheel-drive, carbon everything, full aerodynamic package car with this specs:
car with driver: 265 kg
driven type: AWD
Engine: AMK DT5
CdA: 1,5 mē
ClA: 3 mē
tire radius: 0,225 m
longitudinal coefficent of friction: 1,4
lateral coefficent of friction: 1,5
torque peak: 112 Nm
peak power: 80 KW
Final drive: 13
I did a simulation of all FSG Dynamic Events, except that the Wet Pad was a Dry Pad.
Results:
Briggs Kart:
Skid Pad : 4,5s
Acceleration: 9,8s
Autocross: 87,5s
Endurance: 104,5s/lap
E-AWD:
Skid Pad: 4,8s
Acceleration: 3,4s
Autocross: 69,9
Endurance: 75,3s/lap
The lower CoG and track width were unregarded, because of point mass calculation. Both would surely play in favor for the kart. For a event points calculation i assumed the Kart setting the top time in Skid pad. The other top times were estimated with Delft-ish times. Efficiency was not considered.
In total the dynamic points for the Kart are: 108/575 (because for everything except skid pad it received only the points for completing)
The E-AWD dynamic points are: 493/575
Just looking at those numbers and looking at the speed plots I see, that the disadvantage in traction and weight of the E-AWD is almost completely compensated by downforce. So what makes the difference between those two is the amount of power the E-AWD is putting out. But interpret it for yourself. Attachment 1184
I don't think a Kart could be somewhere near competitive. I agree that the simplicity and radical reduction on necessary parts only is something many students can learn from Karts when they have super fancy electrically adjustable titanium blade ARB's in mind. But a Kart itself would be nothing which could win anything (let alone all the modifications which had to be done to make it rules compliant).
Also adressing the other points you stated:
Cost: A lot of the parts we use came in through sponsoring, In our experience, it is pretty hard to find a sponsor which purely gives you money. It is way easier to get materials, parts or machining time for free, than cash. So the best materials/parts we can get for free will make their way into the car. If there is somebody that will make us titanium bolts, I don’t see any argument why we should not say thank you and take them. They do the same job and safe almost a kg on the car even though they would be ridiculously expensive if bought. On our teams savings account they cost zero.
In case there are two or more possibilities to choose from, for example a cheap and heavy cardan joint and an expensive fancy motorsport joint or in a another example different qualitites of carbon fibres, where you would have to compensate the lower mechanical abilities with more material to pass the SES, I do a simple “return of investment” calculation. When technical features are comparable and it comes down to costs vs weight, I have a number what every saved gramm is worth to us. This number depends on our overall budget and varies from year to year, for example 1€/gramm. This would mean that if we could save 10 kg on our existing design through higher quality/lighter material, it would be worth 10.000€. This is not based on actual numbers, just to give an impression of the way of thinking.
To be able to fund your car it is a game of give and take with your sponsor to keep them on board. When I think about what we can give them I have a list of 4 points:
- Good results and a neat looking car, so they see their logo well represented
- Impress them with the performance of our car on sponsor driving days, to activate the emotional side
- Impress them with knowledge and state of the art technology so they might want to invest in you
- Co-development of new technologies/materials/software they also benefit
My point is, if you build a, like you call it, kind of mini-F1-style car you get access to sponsors who will help to make this possible for you. So this is not a cost question. If you have the option to use high-tech materials and electronics which give you a competitive edge you take it and say thank you. The weekend racer idea is dead. At least in Europe the majority of the teams is purely performance/innovations driven.
I was just talking real money in the last three paragraphs, because I think the majority of FS people would agree that cost report money doesn’t mean anything. The number in your cost report doesn’t have anything to do with real costs and also has no parallelism to the real costs. But that’s a different story. FSG realized, that letting students calculate the costs of their vehicle in a report which takes 45 min to print and therefore is impossible to be thoroughly inspected by the judges is pure bollocks and only promotes fiddling the figures.
Build-time: Having a top level aero kit doesn’t need to stretch your development time in my opinion. The top aero teams did not get there in one year. It is usually a “let’s take lasts years aero and increase downforce or efficiency closer to our target values” kinda approach. Like probably all teams, we have a design freeze. This marks the freeze of airfoils to be able to send the mold data to our manufacturing partners. While this happens, further optimizations of aero balance, AoA, gaps, vaines, plates and gurneys can be done without risking trouble in the overall time table.
Reliability: I’m not quite sure how you judge the reliability potential of a concept, but a pure comparison of weight to power seems a bit too easy for me. In don’t have any statistics to back this up, but if I look at the DNF’s at events I would guess that it’s above 50% a CAD/manufacturing/assembly issue. So the initial concept was perfectly fine, it was just mistake of one person not doing their job properly, like bolts which weren’t properly fastened, stress raising edges, bad welding, wrong positioning of BOTS, aero positioning out of the designated areas, wrong power limits at e-cars, wrong engine mapping resulting in too much noise. Also for e-cars a lot of electrical issues were the cause for DNF’s, which don’t have anything to do with weight.
Personally I would much rather try to keep the reliable and good performing parts from last season and only do detail work on them so you can shift focus on parts with bigger issues to really optimize reliability and performance. In think it’s often the missing work on the details like tolerances, friction, deflection and all the little small side effects nobody thought of, which can cause a good concept to not work as it should. For us this was often the case when we tried something completely new or to radically optimize systems which were already good.
- Freddy
Freddy,
Care to post your OptimumLap files?
I'd be interested to add in a 2wd EV and aero IC car
If you don't want to give up the track files we can use this one:
Attachment 1186
Well done Freddy. I think you've hit the nail on the head right there.
If these are added, add 4wd IC car. You'll like what you see.Quote:
Originally Posted by tim_pattinson
Downforce > all. The power is just there to get you from one corner to the next.
Freddy,
Thank you very much for bringing numbers to the forum.
What I find most interesting is how "close" the Briggs-Kart is to the E-AWD. The Briggs has LESS THAN ~7% of the power, but is still ~70+% as fast as the E-AWD.
Also worth pointing out that a very simple kart frame can take much more power and still work well. MCoach's Outlaw-karts (specs given earlier) have similar power to your E-AWD, but significantly less mass. And I recall seeing somewhere that these karts sometimes run the Jawa speedway bike engines (= 500 cc air-cooled single with 80+ hp)...
So, could you run one more kart simulation, with power somewhere between Charles' 8 hp Briggs and MCoach's 80+ hp Outlaw? :)
What I have in mind for the engine is the JUNIOR JAWA. This is a 250 cc, sleeved and short-stroked, version of the "Senior" Jawa, intended for under-16 year old boys starting speedway racing (the t-shirt reads "No brakes, no gears, NO FEAR!").
The conservative specs on this engine are 30+ Nm up to ~10 krpm, giving 30+ kW (many quote ~45 hp), and 12 krpm redline. This engine has "bare" mass ~25 kg, so make the total car+driver mass = 200 kg (up 30 kg from Charles' car). This should cover the bigger wheels, mandatory safety stuff, etc., of FS cars.
If I were to build this car (which I am sure could go under 130 kg dry in "all-steel" version), then I would fit it with a two-speed gear-box, with low GR = ~15:1, high = ~9:1 (for the typical R = 225, 10" tyres). If you want to do it as a single-speed kart, then maybe GR = ~12:1.
My simulations of the 2-speed JJ-engined car, with ~65%R, suggest it can get just under 4 seconds in Acceleration, depending on set-up details such as ride-height, anti-squat, etc. A turboed version of the JJ (which has the same bottom-end as the 500 cc Jawa, so can take the same power), should comfortably beat the 3.4 seconds you have for the E-AWD (ie. ~80 hp JJ in a RWD-only car).
Lastly, since 2005 I have always pushed the "brown go-kart, WITH AERO-UNDERTRAY". As MCoach repeated above, the whole point of building a simple (= "no-bling" = "brown"), lightweight (= "go-kart" style) car, is that the lower the mass, the more cornering-Gs can be leveraged from any given level of aero-downforce.
So, to start with some conservative, round numbers, could you model this car with CD.A = 0.5 m^2 and CL.A = 2 m^2. I reckon a lot more DF can be had with a good undertray, and possibly less drag (for less Fuel usage). But that might entail a bigger "Cost" risk. Chasing higher numbers first time around means more time taken for design, and more fiddly aero parts to make, so much later build-finish, so less time for durability testing, so bits start falling-off at comp, so (maybe) LOSE MANY POINTS.
(I was going to have a long rant about "Cost" = "Risk". No time now, but deep thinking students might want to read Sun Tzu's "Art of War", Chapter 4.)
Anyway, the above "2-speed Junior-Jawa FS-car/kart with aero-undertray" would be relatively easy and cheap to build. And it should also have exceptionally good fuel economy.
But ... HOW FAST IS IT? :)
Z
Z's JJ does FSAE-A 2016 track at a 86.7 sec pace (with equiv. R25Bs 10" on 8" wide rims). Fuel consumption is estimated 0.144 L/lap. Concerns here are the 2.0 m^2 to 0.5 m^2 ratio (L/D = -4, okey dokey), as well as the added complexity of a non-integral gearbox and turbo doesn't seem to me as typically "brown".
http://i.imgur.com/dhi5Mkt.png
Interestingly, the single speed 12:1 ratio does a 86.9 sec lap, even though limited to about 77 km/h, and fuel usage plummets to below 0.13 L/lap. With a more readily achieved L/D (~2), results don't get too much worse.
http://i.imgur.com/Ix2OzzH.png
These are pretty well comparable with the numbers you get from a 190 kg (+ driver) with a big single or twin with more achievable aero targets. Fuel mileage may vary. N.b. you need a well-trained driver to get these results, the sim is spec driven rather than design driven etc. Didn't take into account that JAWA burn Methanol, so there's that.
I don't know so much about the competition but I use that same software for simulator/simulation work.Quote:
Originally Posted by Z
From what I understand the manoeuvres are all closed loop using the virtual driver included in the software. A part of the project is actually calculating the best trajectory and tuning the virtual driver's control parameters. The cone penalties I imagine are imposed when you stray more than X meters from a nominal centreline of the track.
Freddie,
Thank you for the simulation. Looking at the output graphs I notice two things:
1) I do not think I'd bring a 15/59 gearset to a competition featuring courses like that. I'd aim to hit the rev limiter at the end of two or three of the straights. Would a 15/64 reduction, giving me about 10% more acceleration, change anything?
2) Even in <30 km/h corners, my kart is shown to have no cornering speed advantage. The point-mass simulator uses a single low-speed maximum lateral acceleration figure to represent all effects on the car (grip losses through roll and weight transfer, the need to use the grip to perform work to change the rotational kinetic energy on turn-in) etc. 1.5g is in concession-kart tire territory; on a "green" surface I get 1.9-2 g midcorner. Can you plot sensitivity to this?
Even if a FSAE car built along these lines can't use an MG Yellow tire, the tires used for a light car are very load-sensitive and on something that light would be well over 1.5 warm.
Sincerely,
Charles
Charles, Z,
sorry for just making one statement and then stop replying to the thread.
I'm quite involved with the Setup of our 2017 car and right now pretty busy with fixing understeer Problems.
If i find time, i'll update the results with some other cars and also your finetuning of the Kart.
This refers to a FSAE car or your Kart ? If it's the FSAE car, a discussion about this situation would be interesting to the Peanut Gallery as well as the players.Quote:
Originally Posted by FrederikWe
Freddy,Quote:
Originally Posted by FrederikWe
Take your time.
I know exactly how you feel. (Sighhh ... now to repeat yet again details of rising/falling-rates on other thread...)
Z
Sorry I'm late, but a little on the Vi-Grade Competition. My team participated last year and full disclosure is partnered with Vi-Grade for software access. It was a very enjoyable competition, although it was hard to get members engaged as most were focused on the physical car (I was the only one from the team who directly participated.). The program has DIL capability, my team and I are are working on fully implementing it. The competition itself does not use dil, the cone penalties are for the car driving off the designated path. If you (or anyone) has any specific questions about that competition feel free to ask.Quote:
Originally Posted by Z
Noah