| Author | Message | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 284 Registered: 5-2002 |
They are very strict about the rules, but there are very few rules. 600cc max, 20mm flow restictor and minimun strengths for roll bars and such. The engineering comes in things like the rule says 1" OD x .065 wall mild steel, so you switch to 4130 and go .049" wall, or better yet go up to 1.25"OD and drop to .035" wall and save 40% on the weight. Design is a tough game, kiss (keep it simple stupid) is best, but really, it's as simple as it can be and meet the specs. On the frame, I designed a very complex structure that was hard to build, but it is about 25 times stiffer than a simple ladder frame of equal weight would be. Just bolting the shock to the a-arm is easy, but you either end up with the shock at a steep angle and therefore a decreasing rate or a very heavy arm. Adding a simple linkage gives the the lightest design with the best result rates. At competition, I think we were the only team sitting between events, because nothing breaks. We probably ran 50 hrs of practice, the competition, a few autocrosses with several drivers, and whatever the new people have done and nothing breaks. It could be lighter though. | ||
| Tim N (Timn88)
Intermediate Member Username: Timn88 Post Number: 1828 Registered: 6-2001 |
How strict are the rules? I would think that keeping stuff simple would win. In the freshman design competition all these "smart" kids came up with these elborate, complex designs. When it came time to build them, they couldnt. the ones that actually were able to build their devices, ended up with really fragile ones. Mine was simple because A.) i waited till 2 days before to build it and b.) it takes alot of effort to make complex things. If the gear didnt break off our motor, we would have won a few more rounds. similar to what you describe, i didnt we didnt win alot but still got 100's. the group that won didnt get close to a 100. the 100 averaged in and really helped my final grade though  . | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 283 Registered: 5-2002 |
Everybody drives. you need at least 4 drivers at competition because the rules limit the # of events one person can run. Remember it is an engineering competition, not a race. You can even make the design finals if you're over 500 lbs, and that's like 20% of the points, so you can win all the driving events and only finish mid-pack if the car isn't well designed and though out. The truth is that at the acceleration event, we ran a 4.6 and out of 120 cars, there was only one other car even in the 4s. It turns out I know how to make HP | ||
| Tim N (Timn88)
Intermediate Member Username: Timn88 Post Number: 1825 Registered: 6-2001 |
Hopefully i can work on those problems wheni join. if they are that weight concerned i gues i will never drive. they could save 40 lbs going with a 140lb driver. | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 282 Registered: 5-2002 |
Everything can be made better. The plan was 8-10 lbs off the frame. The frame they built eliminated the weight reductions. The body was literally built and painted in 3 days. It weighs 30 lbs, I designed a new one that looks better, improves crash protection, and weighs less than 10, I started the molds and they are just the way I left them. There's 10 lbs to be saved on the exhaust, �......With a full tank of gas, the car weighs 520 lbs, it should be under 450. There's a lot of work to be done. We just didn't have time to address everything, there were only 3 of us. | ||
| Tim N (Timn88)
Intermediate Member Username: Timn88 Post Number: 1823 Registered: 6-2001 |
How much more advanced can the car possbily get? | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 281 Registered: 5-2002 |
I'm about 30 miles west of philly these days. It's kind of funny really that 3 people (plus 2 part timers) built that car in 8 months and team of 8-10 hasn't been able to build a copy of it (I didn't seen any new engineering when I was there) in 3 years. | ||
| Tim N (Timn88)
Intermediate Member Username: Timn88 Post Number: 1821 Registered: 6-2001 |
So you arent in the capitol district any more? | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 279 Registered: 5-2002 |
It looks like since I left, they haven't built any new cars. The rear is really only a partail inboard I guess. The new frame that's sitting there must be the one I saw, yes there are some very bad welds on it. In fairness, it's mostly 0.028" tubing which is very hard to work with...they should have practiced a little. I has at Union a long long time. I had a 2 year degree when I got there, started in '95 I think and finally technically graduated in '02. I worked and went part time, and was in a combined BS/MS program...although I only got 2/3 though the MS part when I got an offer here in PA I couldn't say no to and moved. | ||
| Tim N (Timn88)
Intermediate Member Username: Timn88 Post Number: 1817 Registered: 6-2001 |
Wicks talked about his furnace for 2 hours. Its a really good idea. he just said that noise was a problem, and so was convincing people to buy it. That guy knows so much stuff, i read some of his articles that he wrote. Thats a clever idea with the suspension. i figured there would be more unsprung weight, but wicks explained that there wasnt or something. How often do they build new cars? Theres a new frame sitting there too. If i have time i want to join that club, but the spring is a really busy time with crew. I'll find time for both, i'll justhave to cut back on school work. oh, on that new frame thats sitting there, there are some real crappy welds. I'm no expert welder, but i can tell a bad one when i see it. on the car you built it looked like only the fronts were inbound. what year did u graduate? | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 278 Registered: 5-2002 |
Tim, I built the frame in Prof Wick's furnace. Any way, I stopped by the shop last summer. I car I built was still there, although it was not completely assembled. There was another frame sitting next to it which appeared to be a design I help another student with a couple years ago, but it had been modified to eliminate most of the impovements and was quite badly built, some really poorly assembled joints. The suspension both front and rear were (some one many have f**ked it up....I mean redesigned it)an inboard design. That is done to get the shocks out of the air stream, reduce weight, and allow better wheel/shock leverage ratios to be obtained. The shocks are "upside" down, as all good shocks should be to reduce unstung weight, only the shaft is moving, not the whole shock body. | ||
| Tim N (Timn88)
Intermediate Member Username: Timn88 Post Number: 1808 Registered: 6-2001 |
I saw that car in the workshop, at least i think its the same one. the rear suspension is cool. the shock is upside down and doesnt attach directly to the chassis, this allows it to have a wider stance (or so says frank wicks). I dont know the last time you were in Union's engineering lab building, or if you know any of the current professors, but theres so much sh*t in that lab now, its a pain in the ass to walk around. theres 2 forumla SAE chassis, a formula baja, professor wicks' device to heat your house AND save on electricity bills at the same time, and countless wheels/tires/engines/parts lying around. anyway, if you know frank wicks, you know that hes a little weird. one time he walked the class over to that building to show us the table we were using for our design competition. Next thing i know we are hearing about how to save $ on eletrical bills using his invention. before we knew it we were hearing the history of electric motors. he goes off on 1.5 hour tangents all the time. | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 273 Registered: 5-2002 |
Philip, As far as i know, they didn't fix the problem on the GTOs, it's just a streched 308 chassis Here's a car I designed and built the frame and suspension on http://engineering.union.edu/me_dept/students/formula.01/home.htm I was considering building a mid engine p-car and designed (including FEA) a couple frames to do it that would work on a 308. One is a no door convertable (I was going to use a 356 speedster body) that is basically twin formula frames. about 65 pounds and 12000 ft-lb/degree torsional stiffness (a viper is 3500). I also did a with door version that would be about 100 lbs, but I didn't do the FEA on that as I recall, but it should be almost as good. The problem is that it has about 250 separate tube that need to be welded together and you loose some interior room. Very strong though. | ||
| Philip Airey (Pma1010)
Junior Member Username: Pma1010 Post Number: 79 Registered: 7-2002 |
I am curious (if and) how Ferrari addressed the issue in the 288s. I believe they were all supplied with an internal roll cage (but do not know from what I've read if it is a simple hoop to save the nut or something involving the A pillars or a full cage). Mark Would be happy to see your sketches if you'd care to post or email to me Philip | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 266 Registered: 5-2002 |
Philip, All good points. On the shocks, I just can't say enough good things about Ohlins, although other brands many be just as good. The ride is smoother than stock even with the springs I'm using that are 3 times stiffer (450f,400r). It does start to feel a little lose over 130, I'm going to have the vavling touched up this winter to correct that Over all thouhg, they're just nice. With the stiffer springs, the stock 18 mm (.710")gts anti-roll bars seem about right. I have heard, never tried, that 1" front bar with 7/8" rear and 350Front spring, 300 rear springs is also a good set up and that sounds about right. Chassis flex. You're 100% right that 3x8s flex quite a bit and it would be better if they didn't. The suspension would work better and it would be more stable going into and out or turns. I just don't know of any quick fixes though. The problem is that they use what's basically a simple ladder frame, although it does have a little monoque reinforcment. The stiffness of the frame is just the sum the the stiffnesses of the 2 main rails. With a coupe you pick up some across the roof, but really the windshield posts aren't very strong, so you don't get as much as you'd thing. I have been toying with the idea of a custom frame to fix the problem and have a couple sketches, but it's quite a bit of work. I have been thinking about it just because I enjoy modifing things and it would be really cool, not really because I need to ring the last couple performance percent out of it. | ||
| Philip Airey (Pma1010)
Junior Member Username: Pma1010 Post Number: 78 Registered: 7-2002 |
All Your thoughts have been helpful, thanks. My logic in raising the chassis stiffening point was as follows. First, I have upgraded the wheel/tire combinations to a stickier/low UTQG tire on 16 inch rims, 225/50s at the front, 245/45s at the rear (245/50s fouled the wheel well liners at the rear). Second, I am going through and replacing the 25 year old shocks, sway bar bushings, control arm bushings etc. Given the car will still spend a high proportion of its time on Illinois' bumpy roads, I've elected to go slightly harder than stock on all the above (but clearly would go more if this was a mostly track car). Third, I have yet to upgrade the rear sway. From memory the stock on my 77 is in the 12 or 14 mm range. Later cars (with 16 inch rims) have a larger rear sway (18 mm like the front) and a racer friend has had good results from going to an even fatter bar on his 328. Any advice here appreciated . Now, to the chassis stiffening. This was spured by three observations. - First, on bumpy roads my 308 makes quite a bit of noise (various interior parts or the rear poly screen moving around I assume). Maybe inappropriately, I attributed this to chassis flex. - Second, I had the opportunity to take a trip around Road America in an F40. While the power (and stopping) had to be experienced to be believed, the total lack on flex in the chassis was extraordinary. - Third, I was previously involved in an effort to make Miata's go faster (resulting in one pulling 375 rwhp at 21 psi). All kinds of chassis bracing etc were tried. One that produced good results (in a unibodied car) was the expending foam in the chassis. While a challenge to work with, the impact as felt by drivers I respected was claimed to be significant. [Sorry, I don't have data]. We later found out that Lexus was also using the foam to create a stiffer chassis. Given the 308 chassis has a few large section members and a variety of smaller section tubes, it would seem (to me) to be a good candidate for a similar treatment. Hence the question. Last, it is, at least for me, not a question of whether it is a competitive in a certain class, rather, at (hopefully) modest cost can the car be upgraded to be better than stock. Philip | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 256 Registered: 5-2002 |
Terry, I ran it once stock, what a pig. I can't say enough good things about the way the car handles after the suspension upgrades, it's just a whole different car, very smooth and predictable. The way you would expect a Ferrari to be. I had the wheels/tires and they definately helped it stick, but it was the shocks/springs that made it feel right, they really redifined the car's charater for the better. I guess the quick direction changes at an autocross favors a mid engine, so a 911 at 3000 lbs, same as my 308 is easy prey. I don't think I've ever run into a well prepared early one, that might be a different story. | ||
| Terry Springer (Tspringer)
Member Username: Tspringer Post Number: 369 Registered: 4-2002 |
Mark, Im impressed if your 308 is autocrossing so well! Mine is all stock still and would be a real pig on an autocross. Perhaps I really should move on getting better wheels,tires and springs/shocks. I am certain it would do wonders for the car. In an autocross, the 911's to watch out for are the early cars. The '69 to '73 911's are very light weight, have better steering and handle much better. These cars can be made into demons without spending tons of $$$. My '69 has a 2.7RS engine and fully tweaked suspension. AT 2050lb and 230hp with all the suspension mods its a blast. The later model 911's, particularly after 1989, dont have as much autocross type potential. They are just too heavy. I had a '95 993 with with RS track suspension, hot chip and exhaust. It was 300hp and the suspension was awesome on the track. However it weighed 3000lb. At the PCA autocrosses the guys in the early 911's would eat my lunch I would be lucky if I posted within 3 sec's of their times on a sub 1 minute 30 sec track. | ||
| Mark Eberhardt (Me_k)
Junior Member Username: Me_k Post Number: 245 Registered: 5-2002 |
Terry, I basically agree, in class racing, you'd spend a ton on the 308 and still loose because of the power to weight issue. That said, mine does very well at the local autocrosses and has never fallen to a 911 in the 6 or 8 times I've had it out. I think you'd be surprised you well they behave once you though the OEM shochs/springs in the trash where they belong and get some wider tires on it. Also, a supercharger works wonders for correcting a poor hp/wieght ratio. I didn't car much for the 308 when I first got it, but now it is the best car I have ever driven overall.....I hope allenlambo doesn't find out I said I like a Ferrari | ||
| Terry Springer (Tspringer)
Member Username: Tspringer Post Number: 367 Registered: 4-2002 |
A 308 is a really fun street car, and can made to be pretty quick and handle pretty well. But trying to take one to the point where it needs chassis stiffening to handle better? I dont see any real point. A 308 will never make a good racecar, it could really only be competitive in an all 308 Ferrari club or such class. Here is a quick synapsis why: The 308 with a 3.0 engine will race against other 3.0 cars. There are too many cars in this class that are just so much lighter, stiffer, more powerful and with more modern suspension and brake setups. Heck, you dont even have to look at more modern cars to see why the 308 is no racer. Compare it to a same year Porsche 911. Fully race prepared for IMSA style GT Racing, the 308 would probably put out 375hp or so. It would have upgraded brakes, would be much stiffer and would handle much better. It could also probably be brought down to around 2400lb if you really went at it. However, nobody did this with 308's back in the day because even after you put in all the effort, the equivalent 911 would eat its lunch. A Porsche 3.0 RSR put out 320hp, weighed 1800lb and dominated its class in international racing. Anyhow, I love my 308 and upgrading the wheels/tires plus perhaps some stiffer springs would make it drive a ton better, but it will never be a REALLY fast car that handles REALLY well. My '69 Porsche 911S on the other hand is a rocket powered roller skate that many an M3 driver has found a bit shocking. | ||
| Mark Eberhardt (Me_k)
Junior Member Username: Me_k Post Number: 241 Registered: 5-2002 |
The reason I started by asking why it needs to be stiffened, is it's been my finding that the best why to fix a problem with a chassis that is not stiff enough is to replace the driver because he's doing something wrong. If you take any average stock car and want to race it, about 70% of the improvement that can be make is tires/wheels. About 25% is shochs/springs/sway bars. 4% in the bushings. So that leaves about 1% going from a stock to a full race chassis. It's easier to tune when the chassis is stiff and it's more forgiving of an erratic driver, but it's not really much faster. A 308GTs already has a roll hoop that is well made and nicely tied in. Adding another piece of metal across there isn't going to do an awful lot unless it's really big, like 3-4 inch diameter. When you go to a full cage with front and rear bar and good triangulation, that's a different story, they make the car stiffer. A roll bar does a good job protecting your head if you roll the car, which probably makes it worth while if you drive at the limits, not so much to improve torsional stiffness. | ||
| billy bob (Fatbillybob)
Junior Member Username: Fatbillybob Post Number: 108 Registered: 8-2002 |
Geez Mark the 308 flexes so much even the top on the GTS makes a difference you can feel! | ||
| Mark Eberhardt (Me_k)
Junior Member Username: Me_k Post Number: 235 Registered: 5-2002 |
welding the doors shut will definately help. I have measured the torsional stiffness in 3 cars before and after a 4 or 6 point roll bar and never found a real difference. I've never measured a 308 though. The math says it won't really help, but I've seen stranger things. | ||
| billy bob (Fatbillybob)
Junior Member Username: Fatbillybob Post Number: 106 Registered: 8-2002 |
Anything works on a 308 they flex like a tin can. Racers have welded the doors shut to get results. A 6 or 8 point cage works and a roll bar of 4 points helps...you can feel it. Custom strut bars help. But for all the trouble just buy a 348 it is stiffer. Better your get a 355b or 360b. B's are way stiffer than T's | ||
| Mark Eberhardt (Me_k)
Junior Member Username: Me_k Post Number: 234 Registered: 5-2002 |
Foam isn't going to do much of anything for you. Ditto on the roll bar. A full 12 or 14 point cage will up it maybe 50% if it's done properly. Why do you think it needs stiffening? | ||
| Philip Airey (Pma1010)
Junior Member Username: Pma1010 Post Number: 75 Registered: 7-2002 |
Curious if anyone has any good thoughts on this. Two solutions I have seen are foam and an (interior) rollbar. On the foam, I heard lexus uses something similar in their cars to stiffen the unibody. Anyone? Archive search revealed nothing. Philip |