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

  1. #11
    Just to keep the discussion going =]

    I don't count the direct acting coilovers as a 'Design Error', after all, that was the way things were done back in those days. There are far worse cockups on the car than D/A suspension, as so many have noted.

    I am not sure that their D/A suspension had much to do with the Monash team being 4th in Design in Australia. I think their defence of the design had more to do with it. Whether the Judges like or agree with your decisions is immaterial, they judge on how well you defend your decisions. The racetrack will prove whether the design works or not!

    I regularly have Monash team members enthusiastically defend their suspension. But if D/A suspension is so great, why did mainstream race car makers abandon the design years ago?

    Firstly, D/A suspension is usually falling rate, not necessarily something you might want, especially at the front.

    Secondly. adjustments in ride height, ride frequency, corner weights etc are much easier with pushrods or pullrods.

    Ron Tauranac tells that he designed the RALTS with two position bellcranks, so wet setup was quick and easy. Moving the pushrods to a different position in the bellcrank raised the car and softened the wheel rate. Ron had designed many Brabhams, right up to F1 and Indy car champion level with D/A suspension, but once he went to bellcranks, he never went back.

    Next thing we will have a team spruiking their revolutionary semi elliptic leaf spring suspension =]

    Anyway, Best wishes to all here for the new year, I hope it will not be as scary as some of the pundits fear.

    Cheers

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

  2. #12
    Hey Pat,

    I just finished reading Brabham + Ralt + Honda by Mike Lawrence. One thing I tried to pay very close attention to was explanations for Ron's adoption of the different design aspect that make the cars resemble what they currently do. Granted you spend alot of time with him (very jealous) and so have probably discussed the matter in great detail, did Ron originally move away from direct actuating outboard suspension to an upper rocker arm/control arm with inboard suspension? My understanding of this was to clean up the airflow for the ground effect cars. The next step he took was to use bell cranks but initially they weren't very good because the motion ratio had way too much rising rate and the suspension would effectively bind. His first cars to use the upper rocker arm were some of the first Ralts ( I think the RT2, the RT1 was an F3 can and still used direct actuating suspension as it was sheltered behind the front body work).

    So what do bell cranks give us?
    - More flexibility in choice of motion ratio
    - Easily achieved rising rate (if you want it)
    - Cleaner air flow through the front control arms
    - Ability to easily package anti roll mechanism within the body of the car
    - More components to design, build and purchase parts for.

    So it is reasonably easy to see why bell cranks became the norm in the top open wheel classes where aerodynamics are such a big factor. But in FSAE where we are by no means drag limited and few teams use ground effects why are bell cranks the standard design?

    I went to the Top Gear Live show in Sydney on the weekend and there was a really neat live advertisement at the beggining where a small open wheel race cars comes flying out of a van and drifts around the stadium. It looked like it could slip right into FSAE. If anybody knows what this little car was and who makes it please let me know (it had direct actuating suspension).


    Sorry for the long post but I don't think this topic has quite been put to bed on this forum.

    Cheers

    Olly
    Olly

    Academy Racing 04-07, 09-11
    UNSW@ADFA

  3. #13
    Hi Olly,
    Yes, I talk with Ron T at least once a week, though we don't talk much about race cars =]

    Your points on push/pull rod suspensions are valid, along with the ability to adjust corner weights without changing preload, tailor rising/falling rates more easily and one Ron is proud of...The ability to rise and soften the car for wet racing by simply moving the pushrod to another point in the bellcrank. A very simple and rapid adjustment when it rains when you are on the dummy grid! Ron was a very practical engineer and many design features were for pragmatic rather than performance reasons.

    I didn't get to see Top Gear as I was in Brisbane. I am told they beat the crap out of our i30s and thet the Genisys Coupe was a big hit. Not sure what the open-wheeler was but I will enquire.

    Finally, Ron's RALTS were numbered mostly for the formula they were built for. For instance there were several different RT3s built for Formula 3 and ditto with RT4s for Formula Atlantic/Pacific.

    By the way, if anyone has a question for Ron, then let me know and I will ask. Olly, is your book autographed? If not email me and I will arrange it for you.

    Cheers

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

  4. #14
    I would also like to add that I thoroughly enjoyed reading 'Brabham + Ralt + Honda'. Just ask my wife, for an engineer I am quite a slow reader and I didn't put it down for three days (when I wasn't driving, working etc, I'm slow but not that slow ). There are many lessons to be learned from the book that I believe have massive significance to FSAE as our design brief is to build a customer of which we are meant to build 1000 per year. I don't believe Ron ever built 1000 cars in a year but he did do a lot to make his cars easier to manufacture and maintain.

    His cars were more popular than his competitors for a variety of reasons but one of the key ones was that he made them easy to set up and tune. He tried to make sure that adjusting one paramater would have minimal effect on another where ever possible. He also made them easier to maintain than his competitors by not sticking important components in hard to reach places.

    The book is not a design text by any measure but I think there are many good lessons about how to be successful in motorsport and the value of honesty and integrity, something that has been said of Ron by just about everyone who cared to comment for the book.

    The i30s definitely copped a flogging, which made me think in light of Toyota recently pulling all its money out of the Australian Rally Championship. How cool would it be to see a Hyundai backed i30 built for S2000 rules.

    If an advantage of push/pull rods is ability to change corner weights without changing preload. Could you not get the same result using direct actuation, setting preload and shimming or adjusting the shock pick up points. I have seen some LMP cars that have shim stacks in the push/pull rods and I assume it is for easy adjustment of ride height and or corner weights.

    Cheers

    Olly
    Olly

    Academy Racing 04-07, 09-11
    UNSW@ADFA

  5. #15
    Pat, That hat looks awfully familiar. I wonder where I've seen at least one other?

  6. #16
    Dick,
    This thread has meandered through a few topics. Which one are you referring to?
    Cheers
    Pat
    The trick is ... There is no trick!

  7. #17
    Quote Oz-Olly
    "I went to the Top Gear Live show in Sydney on the weekend and there was a really neat live advertisement at the beginning where a small open wheel race cars comes flying out of a van and drifts around the stadium. It looked like it could slip right into FSAE. If anybody knows what this little car was and who makes it please let me know (it had direct actuating suspension)"

    Michael, the car in the Shell commercial is a Jedi. More info can be found at www.jediracingcars.com

    Cheers

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

  8. #18
    Hi Pat,

    I had an inkling that it may have been a Jedi (thanks for confirming it), I did a bit of scouting around the net the other night. I came across the link you gave and unfortunately it is for a site which is under construction. A bit more info and some pics are available here www.formulajedi.com.

    Did you get my email? I am not sure if the adress I used was correct.

    Cheers

    Olly
    Olly

    Academy Racing 04-07, 09-11
    UNSW@ADFA

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