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Thread: Upright Mass Comparison

  1. #51
    Kev,

    Surely the ECU system also has 3-5x the toe base normally seen when teams try and squeeze ~25+ degree of wheel lock into 10" wheels.
    UQ Racing

  2. #52
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    Mitchell,

    The toe base is pretty good, and all of the connection points are on decent radii (reducing the angular play due to slop), but I was just addressing the rocker hate

    Kev

  3. #53
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    Quote Originally Posted by Kevin Hayward View Post
    2) As a design judge do you place similar requirements of the more conventional teams to perform the same process on systems with universla joints and steering racks?
    Kev
    This brings up a very interesting point. I can't speak for Claude or other design judges, but my general impression from being on the student side of 8-10 design judging events is "No". If your design is what a judge considers "normal" it is much less likely to attract the same scrutiny as a non-traditional design.

    Some examples

    This one was especially true 4-5 years ago when wings weren't as common. If you had wings on your car, you are expected to be able to justify how it improves the performance of the car, CFD predictions, in depth knowledge of the inner workings of CFD, wind tunnel data or other physical test like coastdown, how much lift does your wing make going 40mph backwards...and on and on. If you can provide all of that information it will help you get a higher score, but if you're missing one thing (ie didn't get the car built in time to do a coastdown test) it will hurt your score. All the other work/knowledge that went into your wings generally doesn't help unless you have EVERYTHING that the judge wants to see.
    A team without wings isn't expected to know any of that stuff and basically gets a "free pass".

    Going back to the other thread about purchased vs manufactured parts. Based on that thread, if a team uses a rear hub from a Polaris ATV they will get a lot of scrutiny to justify that choice. How much deflection does it have, how much is acceptable, how will that affect your performance, how does the weight compare to one you could have made, how much cost did it save you, etc. My team always made it's own hubs/uprights and never got nearly that much scrutiny on them. At most a design judge give the tires a firm shake, and maybe ask to see an FEA picture. Which is lucky for us. We almost never had physically measured compliance values. We used the same hubs and wheel bearing design for 3-4 years with almost no design work or analysis put into it after the initial design. If we had faced the same amount of scrutiny as an "ATV hub team" you probably would have found that we had just as little engineering work behind our design as a team that just bought one. But luckily we got a free pass because we made it ourselves. By "made it ourselves" I should say we got the the CAD file off our computer and sent it to a machine shop

    The question of what you choose to scrutinize vs what you don't is very important, because a short design round of 45 minutes to 1 hour is not nearly enough time to cover everything. If you spend the whole time scrutinizing every part with the same level of detail whether it was purchased or self made, whether it is "traditional" or "not traditional" you'll make it through maybe 3 components before the round is over. In my opinion that doesn't give you a complete idea of how much a team knows.

    Consider this scenario:

    Team A is has some "non traditional" design choices. They have a front ARB but no rear. They have direct acting shocks without bellcranks. They use rear hubs from a Geo Metro that have been "lightened" on a lathe. That team gets forced to spend their entire design round defending things that a design judge is inherently biased against. Even if they do a good job defending their ideas and have every bit of info a design judge asks for to back up their decision, at best the design judge will be "satisfied" but never "impressed".

    Team B follows the cookie cutter recipe for an FSAE car - double wishbone, pushrod/rocker suspension, CNC'd aluminum hubs and uprights, etc. They get a "free pass" on all of the things that team A had to defend. Despite the fact that all of those parts were designed 3 years ago and the current team may not know anything about them other than "they haven't broken yet". But since they didn't have to face the same scrutiny on those parts, they get to spend their whole design session telling you about all the tire data they analyzed, the lap simulator some graduate/PHD student at their school made, the pretty yaw moment vs lateral accel diagrams they made, and all the data they've collected with "their" car (or was it data their teammates collected a year or two or three ago, you'll never know!).

    Which team do you honestly think is going to score higher in design? Which team should score higher in design? Can you even make a fair comparison between those teams based on the completely different content & criteria they were being judged on?
    Last edited by JT A.; 05-09-2016 at 10:15 AM.

  4. #54
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    JT, you raise some really interesting points, and I'd been thinking along similar lines. Back when I had to present powertrain to a design judge, he noticed that our restrictor was shorter than others. This 'looked worse' to him. The reasons we did it that way were largely packaging based, but we had a bunch of CFD and some flow bench tests to back up our unconventional design. He wasn't interested, and we were marked down. So I can totally relate to the unreasonable scrutiny of stuff that is 'non-conventional'
    Jay

    UoW FSAE '07-'09

  5. #55
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    Yea, I think you only need to justify your solution if it doesn't appear in Tune to Win. Just ask UWA.

  6. #56
    At Lincoln in 2012, one DJ refused to answer questions or speak with us after the Design event where he criticized our design (or understanding of it) for having an LLTD significantly different than our weight distribution. The most we got from him was that we should stick the car on a K&C rig. I don't know enough about vehicle dynamics to say if our design was some kind of universal sin or not, but it was frustrating trying to learn and at that time, appearing to be shut down because something was different.
    Cole Easterling
    Brendon & Lawrence Mfg.
    2011-2012 TAMU FH/FSAE

  7. #57
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    Judge and yee shall be Judged. (Here Come Da Judge)

    How about a hint of a name or age? My feeling is that some judges know a lot less than their badge broadcasts. Saw that in the infield this weekend. The LLTD probably ought to be different than the weight distribution but there are ways to dictate it from analysis without K&C data. These are rear heavy cars but with extreme weight reserve tires. So...

    "____ Fill_In_The_Blanks___" yee expert judges ! (If you can). If not, you prove my point. (Ouch).

    Looks like there are two Judge factions in the tent: Engineering vs. Art & Science. The points allocation system sure doesn't help the situation either.

  8. #58
    Maybe I should finally get around to dumping the stash of K&C data I've collected on various FSAE cars over the years. Even among the "good" cars (event winners) there were interesting things that dropped out.

    I would suggest that many teams put a lot of emphasis on their a-arms and uprights, but then underestimate the amount of compliance their wheel bearing arrangements are causing. I've also seen a lot of floppy wheels. The competition results likely sort very well by rear toe compliance

    I've also seen teams spend a lot of resources on trick driver adjustable spring setups that change their roll stiffness distribution about 1% from full-soft to full-hard.

    I'm probably never going to have time to do the complete post-processing for all the cars but if there's interest I can strip out any identifiers and post the raw data without too much trouble.

    Claude's comment of teams not making good use of the data is on point. I didn't get a lot of positive feedback from either design judges or the teams themselves that they did much with the data. Out of all the teams and students I tested with, there was really only one or two that I would think of as showing up prepared to test.

  9. #59
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    Raw KFC with Roll

    ZAC, if you can/want to just post the raw data, I could take a stab at it IF the format of the data is all the same (as in the TTC datasets). Maybe the TTC site is a good candidate to stash it, too. You need tire data anyways to make it actually worthwhile.

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