Suspension Design

Cole,

It is not such a weird mechanism. It is just a four link rear end with triangulated lower links. Way easier to get a lower roll centre than using a panhard bar or a watts linkage.

Difficult to keep the engine low with the setup and from the look of it the links aren't orientated too much in the lateral direction which would increase the load in the a-arm. pretty ordinary attachment of the rod end as well. There would have been better ways to build that adjustable roll centre in.

With these systems you need to watch longitudinal movement of the axle. This can be pretty noticeable in roll as it will angle the beam to the chassis, however you can control this by the upper link angles. Good toe control will lead to some amount of anti in the suspension however.

Not a bad approach to keeping structure away in the rear. Also like the simple side mounted shocks at the front. setup that way the rockers have very little load, everything operates in the same plane and the parts get about as simple as they can for a rocker based double a-arm setup. 4 of the cars (2 as student) that I have been involved with have had that style setup and it is amazing how much time can be saved not worrying about making sure all the movements are in the right plane etc.

Kev

Z,

More great drawings, thank you!

These are great ideas for teams to investigate especially for teams further down on performance. Not because they are inferior, rather because a team of 100 people with a current super fast car are less likely to make changes to their concept and take the risks. That leaves an opening.

One of the great thing about the trailing links (and some four link designs) is you design them quite effectively with much easier and cheaper bearings (or bushes) rather than just using ball joints and rod ends at every opportunity. By reducing the accuracy required in manufacturing you save yourself time and money, both of which are far more important than most teams realise.

Again these concepts very much suit a single (or small) engine with a narrow sump such that you can still keep the engine low.

I wonder if the real question for teams to ask is how do you setup a team such that you do not immediately reject these ideas. For example if you break a team up into roles based on components and allocate a person to a diff then you are much more likely to end up with a diff of some sort (most likely an expensive drexler) than a spool or beam axle.

These sorts of suspension systems require a complete game change of the vehicle with people working very closely on suspension, chassis, engine, aero etc. and having a lot of people accept compromises for the better vehicles that at first look horrible.

How many teams share and discuss these sorts of concepts, with a reasonable amount of discussion and preliminary design, before rejecting them. Or are teams just jumping into double arms, rockers, etc. just because they want to save time and arguments?

Kev

Kev I bet 95%of the teams do the latter; we all tend to forget the big picture and focus to details.

Cole,

That design is fairly typical of a F500 car just a different variation of it. It was most likely copied over from that series. For example...

http://www.apexspeed.com/forum...?p=191266#post191266

...our rear suspension was based very much off the Novakar but with dampers and a satchell 4-link instead of the trapazoid link...

http://www.youtube.com/watch?v=PviU2A_uOo4 (bunch of pics in there that's why i posted the vid instead of link to photo dump)

Kevin,

I think the single biggest factor in making radical decisions is to have a healthy "f*&k it...lets go for it" attitude amongst your peers. Geoff said it best in his previous post about designing the car for yourself. While I am sure that there were lapsims, data and discussions about the competitiveness of the RMIT single at some point there was belief in a concept/dream, whether founded in reality or not, followed by a "f*&k it...lets go for it". That leap of faith is something that many engineers have a hard time doing because of lack of creative thought, hum drum personalities and anti-rebelliousness. Engineering is rife with personalities that are the antithesis of someone like Neil Degrasse Tyson. In our case we knew there wasn't a chance in hell of beating RIT (example team because of proximity)at their own game(double irs with 600cc 4 cylinder) so we decided to take a lateral direction and held onto that concept of doing things different. When I came on to that team I sold the concept to them based on passion and exuberance followed up with some rough comparative analysis. It turned out well given all the factors we dealt with and could have been a real contender in following years of turd polishing iterations but alas it didn't happen.

I think the second biggest factor is it appears that these radical changes or directions are carried out by tight small teams. I think in general the bigger and more established a FSAE program is the more the likely they are to not rock the boat. This leads to the much discussed stagnation of only doing tiny changes versus great leaps. Obviously there are reasons for doing this in those big programs so I can't be entirely critical. The small team structure allows for easier subsystem integration since people spend more time talking about concept integration versus going off into respective corners and obsessing over the individual components. Holistic vs big medicine if you will. Once you get through that part of it the questions of how to actually carry it all out are pretty easy to be honest. For instance myself and Harry Bikas from U.o.P. Racing Team just go nuts and riff on cool ideas which from those talks and him working with his team have come up with an astonishingly cool design that I think will turn heads and rack up a good amount of points. Being from a small team allows him the freedom to pursue such things because there isn't a culture of "we have to make sure we gain another position this year for the dean to be happy" or "Chauncey needs to make this happen on the car so he can get a job with Stuffy Engineering Inc. after bragging about his boring design to people at the yacht club"...

http://www.youtube.com/watch?v=MWolPnWF3m0

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I wonder if the real question for teams to ask is how do you setup a team such that you do not immediately reject these ideas.

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Alternative question, if I may Mr H

I wonder if the real question for us to ask is how do you setup a competition such that teams do not immediately reject these ideas...

I'm going to leave all the suspension talk to the suspension guys, but I just wanted to say something about the idea that "we'll never beat Team X at their own game":

I suppose I should say that I interpret "beat/better/etc" as being having equal laptimes, or points in events.

Anyway, I think teams are much more fragile than we think, and that personnel changes happen year to year. Just because a team did really well last year, doesn't mean it will be a repeat the following year.

I think too many things go wrong when decisions *aren't* supported my some sound logic (of which the best/most convincing is probably a points sim).

Also, having lots of similar cars means sharing ideas on how to make those cars go fast works better. This is all about learning, so having lots of similar systems out there means a lot of info to share for the new/slow guys.

Kevin: while some of these systems are *simpler* to build, teams with experience can build the standard car quite *easily*. I know Z goes on about less a-arms and hardpoints, but I don't think those things take up an unreasonable amount of time. Considering that most failures in FSAE stem from a lack of basic engineering (with known designs), there's a lot to be said about getting the basics right.

I'd be happy to be part of a team that produces a car that finishes top 3-5 (in AUS) {3-5% in the big comps} for many years in a row. That would be greater achievement than winning for a year or two, then dropping off the map. Or never bringing a fast car at all (all those teams running 1-2 seconds (over a 60s lap) behind the fastest car are seriously off the ball, in my opinion).

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Originally posted by Z:
"... shouldn't the wheel be attached by one of those fancy tapered face torque couplings<grin>?"
An important trick is the spacer ... (this appears in the sketch as a small triangle).

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Thanks for clarification--a good trick to use the split tapered washer.

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"... the beam axle could have a single joint at the car centerline to instead form two swing arms."
Ah, yes, this was used very widely by Mercedes around the 1950s. ... Essentially, take a live axle with diff offset a bit to one side, cut it in half next to the diff, put a single UJ there, and presto!, two Swing-Axles.

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Also used by Archie Butterworth on the front of the AJB Special. He started with a Jeep front axle (offset diff) and split it to make a front swing axle. After being wrecked and rebuilt, it became the Butterball that my father raced. Just one "little" problem, on hard acceleration, the propshaft torque reaction would lift that front wheel off the ground! Some details at http://en.wikipedia.org/wiki/Archie_Butterworth Built in 1948, I wonder if Mercedes copied Butterworth?

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Originally posted by Big Bird:
I wonder if the real question for us to ask is how do you setup a competition such that teams do not immediately reject these ideas...

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Geoff,

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Originally posted by Z:
... How [UWA] only managed 3 points (out of 200!) in Design is beyond me. Something very wrong there... It is clear to me that the Design score does NOT reflect the car's design, or the student's knowledge... Some more openness and transparency in these decisions would be welcome...

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Yep, more openness and transparency. For example;

Full public release of Design Judges scoresheets and opinions on each car. Why did this DJ give that team a high/low score? Etc.

Similar release of scoresheets from the Teams, rating the Design Judges performance during Design event. Did the DJs seem to understand what the Team was trying to achieve? Did the Team learn anything from the DJs, either during or after Design event?

Perhaps the Teams could also rate each others cars (not their own) with this contributing to the overall Design score for each car.
~o0o~

Currently, the 200 point Design score in FSAE-A reminds me a lot of that editing option on my new scanner - "Try Your Luck!" http://fsae.com/groupee_common/emoticons/icon_eek.gif

Z

Z,

I am right behind publishing design feedback for all cars with the design reports. This can only aid the educational aspect of the competition. It would be great to see how other teams have approached the same problem.

Would be considered unacceptable in the competitive world of professional motorsport, but we shouldn't be following the same rules.

Share and learn together!

Kev

Z thats a great proposal. Kev, wow mate!Sure thee have been teams sending out their DRs in the past (ADFA had theirs on their website and I have sent ours out to someone who asked) bur having access to such info from a top team like UWA is really cool. Also hats off to any team who dares to be different, think outside the box and often change the game. UWA especially despite not being a small or unsuccessful team and still being brave enough to try novel ideas. I will also have my eyes open for Cal Berkeley team this uear...