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Thread: Pat's design error of the month contest Dec 2008

  1. #1
    Take a look at the pictures at the end, Pat claims he found at least 18 design errors on that old F1 car

    Pat's design error contest

    Here are the ones I found with a first glimpse:
    - scariest ARB-actuation with the longest ARB I've ever seen (at least 5 design flaws)
    - steering rod with a huge angular offset for best linear actuation
    - mounting of the steering rod to the hub will result in a torsional moment to this odd looking spigot.
    - spigot seems to be screwed to the hub. This means that a torsional moment during cornering could unscrew the spigot, hmmmmm
    - good old rod ends in bending
    - bad vector force load pathes where the heavily stressed lower a-arms are mounted to the chassis will result in beding
    - brake lines are carried by a sharp looking metal sheet -> danger of abrasion when moving due to cornering
    - mounting of the shock will result in a beding moment to the lower a-arm
    - Uhmm, where is the roll center supposed to be?

    In addition I don't want to crash in that car The front steel frame will have little effect and supposedly would simply snap away. And the fire extinguisher would be a good slam to the head...

    Merry Christmas and a Happy New Year to all of you!

  2. #2
    Take a look at the pictures at the end, Pat claims he found at least 18 design errors on that old F1 car

    Pat's design error contest

    Here are the ones I found with a first glimpse:
    - scariest ARB-actuation with the longest ARB I've ever seen (at least 5 design flaws)
    - steering rod with a huge angular offset for best linear actuation
    - mounting of the steering rod to the hub will result in a torsional moment to this odd looking spigot.
    - spigot seems to be screwed to the hub. This means that a torsional moment during cornering could unscrew the spigot, hmmmmm
    - good old rod ends in bending
    - bad vector force load pathes where the heavily stressed lower a-arms are mounted to the chassis will result in beding
    - brake lines are carried by a sharp looking metal sheet -> danger of abrasion when moving due to cornering
    - mounting of the shock will result in a beding moment to the lower a-arm
    - Uhmm, where is the roll center supposed to be?

    In addition I don't want to crash in that car The front steel frame will have little effect and supposedly would simply snap away. And the fire extinguisher would be a good slam to the head...

    Merry Christmas and a Happy New Year to all of you!

  3. #3
    Hey, thats a good start, keep going.

    By the way, you have spotted some stuff that I didn't, so maybe we can find over 20 Design Errors.

    Happy Holidays and have a great new year.
    I will see you all in Hockenheim in August

    Cheers
    Pat
    The trick is ... There is no trick!

  4. #4
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DART-CG:
    Take a look at the pictures at the end, Pat claims he found at least 18 design errors on that old F1 car

    Here are the ones I found with a first glimpse:
    - mounting of the shock will result in a beding moment to the lower a-arm </div></BLOCKQUOTE>
    It will. But is this a design flaw?? How is a control arm mounted push/pull rod any different? We see that all the time and it works well. Mounted away from the center of the control arm's span may not create an unnecessarily large bending moment.

    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
    - mounting of the shock itself without a rocker arm will result in huge forces carried by the chassis... </div></BLOCKQUOTE>
    Are you saying a rocker arm will reduce loads into the chassis?? I'd say not. A rocker arm creates more points of force application to the chassis, not mention the possible magnification of some of those forces. What are you trying to say? There are no HUGE forces from a direct-to-chassis mounted coilover.

    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
    - Uhmm, where is the roll center supposed to be? </div></BLOCKQUOTE>
    Who cares?? What difference does it make?? A kinematic roll center means nothing to the handling of a racecar.

    MERRY CHRISTMAS ALL!!!

  5. #5
    It looks like the spindal is held in place with a nut on the inside of the upright. This should be retained with somthing to keep it from backing off.

    The steering links could be mounted in double shear pretty easily. I'm not sure if this is a design error, but its good practice to use double shear.
    -BenB
    '03-05 Oregon State FSAE Alum

  6. #6
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by BennyHL:
    [QUOTE]Originally posted by DART-CG:
    Here are the ones I found with a first glimpse:
    - mounting of the shock will result in a beding moment to the lower a-arm </div></BLOCKQUOTE>
    It will. But is this a design flaw?? How is a control arm mounted push/pull rod any different? We see that all the time and it works well. Mounted away from the center of the control arm's span may not create an unnecessarily large bending moment.

    -&gt; Hmm, if you can avoid any sort of unwanted stresses without big expenses then you should do it. For sure, rod ends in bending are no deal when you overdimension them. But is it the way to do?

    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
    - mounting of the shock itself without a rocker arm will result in huge forces carried by the chassis... </div></BLOCKQUOTE>
    Are you saying a rocker arm will reduce loads into the chassis?? I'd say not. A rocker arm creates more points of force application to the chassis, not mention the possible magnification of some of those forces. What are you trying to say? There are no HUGE forces from a direct-to-chassis mounted coilover.

    -&gt; OK, my fault. My brain switch the work = force * way in the wrong direction

  7. #7
    HOLY BUMP STEER BATMAN!!!

    1) No free threads above the nylocs on the pivot arms.

    2) No captive washers on the free ends of the isngle shear bearings.

    3) It looks like the lower damper pivot might even not be aligned longitudinally with the leg of the lower link, so it's actually a bending + TORSIONAL loading. Special.

    X) Jam nuts on two of the rod ends I can see are not snugged, but this could just be a during-the-build rollout photo, so I wouldn't count those.

    4) A mighty outragious scrub radius. About 5 inches I'd say.

    5) What is the brake cooling duct pointingat??

    6) Looks like the upper damper pivot and forward leg of the upper wishbone pivot on the same bolt, which gives it a might bending moment, unless there's a third shear separator in there, which I'd wager there is not.

    7) I don't see washers under any of the non-counterbored SHCS's like on the lower wishbone pivot.

    8) !!!!!! The steering arm spigot is threaded into the upright, and then loaded in bending, and one steering direction will work to un-thread it!!!!!

    9) The two arms of the upper suspension link look like they are bolted together by that vertical SHCS, so the loading on the upper arm has the rod end in bending, and the threaded insert in bending.

    10) On the frame side, there are lots of triangulations not terminating at nodes, and lots of trinagulating members just stuck in the middle of tubes, like the forward front members, and the support for the fire extinguisher. Looks like the front 'shovel' structure is bolted on, with the bolt guides not axial to the tubes, but stepped off the sides. Which is I suppose not terribly bad since the welds are all nice and long and loaded in shear, but it could be a lot better....

    11) The rear wing is not in free air at all.

    12) Wing end-plates don't extend nearly low enough for F1 speeds.

    13) Semi-radially mounted valve stems might open under high rotational speeds.

    14) Front tires look a little low-rider-ish, they're a little narrow for those wheels.

    Good call on abrading the rubber brake hoses on the sheet metal DART. With steel braided ones, you'd abrade away the sheet metal guides!!

    Best,
    Drew
    _______________________________________

    Northwestern Formula Racing Alum
    Head Engineer, Frame/Suspension 2006-2009

    My '73 Saab 99 Road Race Build

  8. #8
    Is that a fire suppression bottle mounted in the front crush structure?
    Neil Schreiber
    Missouri S&T Racing
    '05 - '08

    http://fsae.mst.edu/
    *formerly University of Missouri-Rolla

  9. #9
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    1) From what it looks like, the steering rack retaining brackets are bolted to the bulkhead in close proximity to the holes. This looks like it could flex when large loads are applied.

    2) The holes in the front bulkhead have lines running through them, but are not grommeted.

    3) The rear ARB (what we can see of it) seems to be mounted to the chassis pretty close to the center of the bar, instead of near the ends. This would cause a bending moment on the ARB along with the torsional moment.

    4) Right behind Arno's head seems to be an exposed fuel filler neck with no barrier between it and the driver.

    5) The forward link on the front lower A arm looks to have a large tab welded tangent to it, which the shock is then mounted to, as if Arno ran out of space to put a proper bracket!

    6) This is a hard one to see, but it looks as if the two legs of the A arms are BOLTED together instead of welded!
    Formula SAE: When you just can't get rid of a girlfriend.

  10. #10
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DART-CG:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by BennyHL:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DART-CG:
    Here are the ones I found with a first glimpse:
    - mounting of the shock will result in a beding moment to the lower a-arm </div></BLOCKQUOTE>
    It will. But is this a design flaw?? How is a control arm mounted push/pull rod any different? We see that all the time and it works well. Mounted away from the center of the control arm's span may not create an unnecessarily large bending moment.

    -&gt; Hmm, if you can avoid any sort of unwanted stresses without big expenses then you should do it. For sure, rod ends in bending are no deal when you overdimension them. But is it the way to do?
    </div></BLOCKQUOTE>
    </div></BLOCKQUOTE>

    Isn't that the exact reason why you have that block of steel in those beautiful wishbones? It would be ideal to mount the dampers directly to the ball joint, but unfortunately impossible with any setup. I would have to disagree in saying that any bending is a design flaw, because it is unavoidable, in any currently feasible configuration. Minimizing the bending is needed, but as far as I have seen, it is impossible to eliminate.

    An Australian team just finished 4th (I think) in their design finals with direct dampers, so I cannot see this being one of Pat's chosen design flaws (he seems to like those Australian teams ).

    Oh, and I don't see any safetywire on those bolts, IMO, the worst design error of them all!
    J.R.
    University at Buffalo Alum.
    Safety Wire Team Leader

    "Most of the things worth doing in the world had been declared impossible before they were done."
    Louis D. Brandeis

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