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Thread: 2016 Formula Student Germany

  1. #11
    Quote Originally Posted by Kevin Hayward View Post
    Julian,

    You wouldn't know how much of a safety bead those teams run do you? I have seen some very marginal attempts of this feature on many student designed rims. A decent safety bead can keep a tire on fully deflated at high loads.

    Another method would be to screw into the tire beads radially.

    There are also internal spacers that can be used (and are in off-roading).

    Definitely something that can be accounted for in design.

    Kev
    Kev,

    I don't know what Hamburg is doing, but Zurich is running off-the-shelf Keizer shells after they had some issues with their CFRP rims.
    -------------------------------------------
    Alumnus
    AMZ Racing
    ETH Zürich

    2010-2011: Suspension
    2012: Aerodynamics
    2013: Technical Lead

    2014: FSA Engineering Design Judge

  2. #12
    A few years ago we saw Prototype cars coming back after 2 or 3 laps with "hot" tire pressure that were lower than the "cold" ones they had when they left the pitlane.
    The reason was that a sudden change of the tire side and vertical loads on the curbs of a chicane made the base of the tire wall move on the horizontal part of the rim (called the hump) that was not long enough and/or did not have a ledge.
    In the first few laps, or even the first few corners, without enough pressure built, the tire carcass flexed a lot and in some conditions of lateral and vertical tire load, the movement for just a fraction of a second was big enough to have the nitrogen get out of the tire
    Remember also that the tire carcass stiffness variation is the biggest in the first laps of a brand new tire
    Claude

  3. #13
    Well, a good re-design of the rim's bead should be enough.

    However, I haven't seen any rule regarding what pressures the teams are allowed to use in order to get the tyre in position. With an over-extreme design, the tyres can require a lot of pressure to jump the bead and get in position, and your rim may not withstand this.

    If it fails, half of the rim will go flying through the room. It is super-dangerous.

    I am actually quite surprised this is not covered by the rules. Being involved in Rallycross, Rallying and Off-Road rallying right now, I can tell you there is a maximum tyre pressure in all of these series. And even then, a guy almost got killed last year when he left the tyre grease dry out in the sun before inflating the tyre. The grease got sticky, he didn't pay attention and the pressure reached 15 bars before the tyre jumped in place, sheering the rim in 2 pieces and throwing one part 50m in the air.
    There may be room for a rule change there.

  4. #14
    Senior Member
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    Alternatively, like any engineer should do after identifying a potentially dangerous situation, is analysis their design, proof test and rate their rim, UWAM tested to failure a few of the earlier rims (before my time), as such, we had a number not to go past.

    There are so many things that can be dangerous if the risks of failure are not controlled. Why is there not a focus on inadequately designed wishbones? (I'm not saying the most recent failure was poor design, I wasn't there, so no offense is intended)

    The last thing we need is additional knee-jerk rules
    ex-UWA Motorsport

    General team member 2013-15, Vehicle Dynamics Team Lead 2012
    Project Manager 2011, Powertrain minion 2009/10

  5. #15
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    Thanks to all for your replies. We call this failure a de-bead or debead. Sorry to hear that this ended endurance for two teams.

    During TTC testing at Calspan TIRF this has happened a few times--at low pressure, cornering under high load (it also happens occasionally with larger tires). Often, there is enough airflow through the regulator and rotary union to re-inflate the tire and continue the lab test, so only one slip angle sweep is compromised. If a tire/rim is marginal, I've seen the bead start to crawl away from the flange and then pop back on when the steer angle reverses. A related problem is rotational slippage between the tire and rim during drive-brake testing. Various bead locking mechanisms are discussed in the TTC forum. From memory, we have had the TIRF staff mount tires dry, minimizing lubrication seems to help. They are very careful about overpressure during bead seating!

  6. #16

    Feel the pressure?

    Guys,
    I do not know any racing series where there is a rule about maximum tire pressure. However there are a few racing series with a minimum tire pressure, Formula One being one of them.
    But for God sake do not bring that rule into Formula Student.
    Because
    a) Formula Student is not racing
    b) It is going to make the rule book even unnecessarily thicker
    c) It is really hard to monitor and control as there are so many factors to consider: quality of the inflating gas, humidity, atmospheric pressure, ambient temperature, are we regulating the cold or hot pressure, how do you define hot pressure? After 75 mm of acceleration, after one stint of endurance? Will FSUK participants be disqualified for a tire pressure 0.02 bar under the rule limit? Come on...
    d) It is the responsibility of the team to make an engineering decision where the adequate pressure stands, as a compromise between performance, performance consistency and reliability.
    Claude
    Claude Rouelle
    OptimumG president
    Vehicle Dynamics & Race Car Engineering
    Training / Consulting / Simulation Software
    FS & FSAE design judge USA / Canada / UK / Germany / Spain / Italy / China / Brazil / Australia
    [url]www.optimumg.com[/u

  7. #17
    I wouldn't be surprised if low starting tire pressures were at play or the wheel loads may have been too high for the shell. The Keizer and especially Douglas rims are notably compliant.
    Last year, we noticed one of our wheels seemed to have a "wobble" to it when we got to competition and replaced it. Rolled to autocross on 4 shiny new wheels -- came back from autocross with 4 new wobbly wheels.
    I have also been able to bend 13" Keizer and 10" Douglas wheel shells by hand and I'm not very a big person.



    I've run 13" Hoosier and Goodyear and 10" Hoosier tires down in tire pressure until they debeaded. Sometimes it's just nice to know.
    I've also run FSAE events on 0 psi (gauge) previously on purpose without issue, so don't get all up in arms about minimum tire pressure rules either...
    Last thing we need is more rules.
    Kettering University Vehicle Dynamics
    Formula SAE 2010 - 2015
    Clean Snowmobile Powertrain 2012 - 2015

    Boogityland 2015 - Present

  8. #18
    Thijs and all,

    Australian team members are for sure as well educated, disciplined and passionate as any other team members in the world.

    They do not have as much potential sponsors, they not have the manufacturing habits/excellence that we can see in Germany (but it is not as if Australian manufacturing is bad) and the distance to Europe and the US is an issue...
    .....but I do not believe that explains the lack of performance in foreign competitions.
    I think the main issue is that, in simple words, the professionalism of the best FS teams has been exponential while the Australian teams progression is linear.
    The constant weight (if not in fact an increasing weight) of Monash car is an illustration of this low performance slope.
    In other words, it seems Australian students do not know what they do not know and I am not sure they do whatever is possible to discover what is missing.
    The few Australian teams I know well seem to be having a good team spirit, a good cohesion, they know how to have fun (it is important) but the awareness of the level of needed excellence to be competitive seems to be not well defined and/or not well integrated.
    Formula student is about offering the students the opportunity to learn by doing, but in a competitive and connected world it is also about learning quickly.
    Meanwhile, even with a low absolute value for now, progress slopes of Chinese and Indian teams are impressive and should not be disregarded.
    Claude Rouelle
    OptimumG president
    Vehicle Dynamics & Race Car Engineering
    Training / Consulting / Simulation Software
    FS & FSAE design judge USA / Canada / UK / Germany / Spain / Italy / China / Brazil / Australia
    [url]www.optimumg.com[/u

  9. #19
    Would be great to have Scott Wordley's take on the performance of Monash.
    Let's hope their "distraction" with the Electric car (very tough to build even 2 cars if you are as budget-constrained as Claude is assuming) does not "dilute" the performance even more.

    I'm sure those guys will bounce back and we will have a competitve Aussie team at FSG 2018!

    Claude,

    fully agree with you on the trajectory of the Chinese teams. We were amazed by the performance of that 222 Chinese team that rocked AutoX.
    They placed 13th and outperformed very good "Western" teams like UAS Karlsruhe, Kassel, Washington, Weingarten or Ann Arbor.
    Job very well done.
    The Indian teams seem to continue to struggle a bit but also a step forward!

    Sadly, the number of (German) teams that should at least have the chance to have decent funding (and therefore no excuse on that front) and showed very poor performance was also very high.
    I know, I lived in a fairytale bubble of FSAE in my time, but what the heck is going wrong there?

    I don't want to "point fingers" but now I'm calling the following teams to better understand, why they weren't driving or why they were not as fast as expected (>15sec OFF PACE in AutpX). I know that difficulties can arise; but for German teams FSG is the absolute (and sometimes only) highlight of the year. They present themselvs to Sponsors here. They are on fire... They probably will never be better prepared but still there were issues. I want to understand, so please:

    FSE (some very well established!): Kaiserslautern, Hannover, Braunschweig, Cologne, Nürnberg, Deggendorf, Illmenau, Aalen (they are quite new to be honest...),
    FSC: Wuppertal, Dortmund TU, Dortmund UAS (come on Dortmund, why not merge the teams?!), Schweinfurt

    Thanks for enlightening me. I hope I can understand the issues (even after Vehicle Status Videos that you all passed) better, so that I can help teams better in the future with that knowledge.

    Best
    Julian
    -------------------------------------------
    Alumnus
    AMZ Racing
    ETH Zürich

    2010-2011: Suspension
    2012: Aerodynamics
    2013: Technical Lead

    2014: FSA Engineering Design Judge

  10. #20
    Reading your reply Claude, I wonder if I expressed myself correctly.

    I was just talking about a maximum pressure used to get the tyre in position on the rim. Then, drive at the pressure you feel best suited to your needs obviously.

    I meant this just for the safety of the people putting the tyres on.

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