Beam Axles - Front, Rear or both.

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Originally posted by AxelRipper:
American Racing and Hoosier both make tires in 8" size for MiniCup cars.

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It's American Racer: http://www.americanraceronline...Track/mini-cups.html They claim to have "softer" compounds.

Hoosier seems to only make that one very hard 8" MiniCup tire. http://www.hoosiertire.com/pdfs/speccat.pdf (page 5) Do we have any FSAE alums working at Hoosier that could convince them to do a run of R25B compound MiniCup tires?

What does it take to get new tires into the Tire Test Consortium queue? http://fsae.com/groupee_common/emoticons/icon_smile.gif

I'm sure to a lot of people using 8" wheels seems nuts. Perhaps as nuts as a 450 single seemed in 2005. Just because there hasn't been a simple, commercially available solution before doesn't mean it's not a smart approach to the FSAE problem!

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Originally posted by Z:

The bottom line is that suspension Bounce (=heave) and Pitch modes only need very short travel. This is easily done with beams by having short travel (+/- 5mm) bump rubbers fitted at the mid-beam position. With these the chassis can be run very low with no scraping, so low CG, but there can still be plenty of wheel travel in Roll and Twist modes to keep the scrutineers happy. The soft Roll mode is, of course, no problem because no camber change, and the undertray doesn't scrape because it is beam mounted.

Z

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Has anyone checked HOW the "minimum suspension travel" rule is measured? Usually the marshals push the car down with their foot (so suspension operates in bump) and visually check it. A solution such as the one described by Z above could not be acceptable then...Of course you could use scrutineering-specific rubber bumps and replace them for the race (suspension springs CAN be exchanged at any time and this is essentially a suspension "spring", but I do not know how the scrutinneers will feel about it; it is a bad way to get DQ. Anyone checked it with the rules yet? Instead of a rubber "spring" you could use a horizontally mounted spring/damper, actuated by a peg n slot driven bellcrank, thus having an adjustable (and dampened) heave/pitch spring...

Seriously, topics like this ARE the reason why I love the fsae forums. I would really like to have this convesation up personal with all of you, something like a design meeting with a drawing board somewhere in the room, but I'm afraid we would be discussing for days.... http://fsae.com/groupee_common/emoti...on_biggrin.gif

Have you talked to American Racer? If so, what information have you gotten about their MiniCup tires?

Splitting a 60 tire production run between a few teams wouldn't be that bad of a deal to put together. 15 sets is nothing! I think the current Hoosier MiniCup tires are only $60 each!!! I'm sure they've seen how much demand there is worldwide from FSAE, considering they seem to be out of 13" FSAE tires at least once a year. The only way to make something like this happen is to convince a company that it makes business ($$$) sense. The "passion project" approach will never work.

What were the other 8" asphalt racing tire manufacturers that you identified? My cursory search a few months back only found the two we've been talking about.

[sorry about the major thread hijack]

I dont think the rules specify how exactly they are measured, you may need a clarification on this, putting different springs in to pass shouldnt be necessary, what if you run mega stiff springs, you can have the required trvel, but you don't use it, it would need to be proven another way..

We ran into a design issue with our car two years ago, but didn't figure it out until about a week or two before competition. The kinematics our rear suspension made it incredibly stiff even with the softest springs we had ( its my fault, and I'll admit that ). Anyway, we definitely had the capability to move 2" kinematically, but in reality it only moved about 0.5" when you jumped hard on the rear end of the frame. Judges looked at me skeptically, but passed us through with no real issue.

Travel was always "measured" on our cars that way; a marshall jumping up and down on chassis...that's why I was wondering about the solution Z proposed.

Z, I was reading your thoughts on "damper histograms" thread, and I have a question... In a beam suspension like the one described here, why would anyone want any stiff mode? You could limit chassis roll by using stops, but again, why limiting pitch and roll? Besides geometric weight transfer caused by movement of the CoG while pitching/rolling(which isn't that much), I cannot think of anything obvious... Another thing is that by using beams, all the lateral forces are transferred to the chassis via 2 points for each axle (plus two for the dampers), so a fairly stiff bottom is all you need. The rest of the chassis could be really flimsy (besides crash structures) with no problems. Plus you can achieve a soft twist mode (while having harder pitch and roll modes) by making a chassis torsionally flexible....

It looks like a great idea.

But I'm not so sure about the aerodynamics.

So far we haven't seen any great aero-packages without wings that helped a lot.

e.g. Munich's car didn't seem faster through the undertray compared to a similar design from Stuttgart.

One thing I'm curious about is the "live" aero.

I couldn't find anything in all the aerodynamic papers online that said that live aero is so much better than a normal mounted aerodynamic.

I just read that the suspension can be softer but no other significant bonuses.

I guess it's good to have the force directly on the wheels but is that enough to change the whole layout of a car?


The design of the different wheel sizes is interessting. Maryland did it with 13inch and 10inch. Maybe this would help the concept too. The new 13inch Goodyear's should be pretty soft...


Cheers,

Jack

Jack,

Besides running softer suspension setup, which aids mechanical grip due to reduced tire load variation, and more direct aero load paths, it also has the advantage of being able to run the sides of the undertray extremely low, as its distance relative to the wheels is maintained. This in turn gives extremely good seal to the negative pressure developed by an undertray, and lots of downforce due to ground effect (remember sliding skirts or even better "double chassis" Lotus F1 cars?). On the negative side, live aero means added unsprung weight... IMO the main point here is not aero, as live undertrays are possible with double wishbone suspensions too, but purely (possible) kinematic/loadpath gains....

Thank you for your explanations.

I was just curious about this topic in the first place and thought it might be a good point to register and ask it right now http://fsae.com/groupee_common/emoticons/icon_smile.gif

I read Pat's column and saw that he sad ECU's aero wasn't that good as Monash's because it was chassis mounted not unsprung.

I can't see the huge advantage at the front wing for instance if it's mounted to the bellcranks or something like that..

Thanks again!