Designing an FSAE chassis

[G37Sam]

Very good point you guys mention. Of course I don't plan on getting too anal with the chassis design, not for a rookie team at least. As for the suspension design, there is still is some more reading & research I need to do on that topic, still need to convince myself that using a rocker assembly is smarter than a simple mount (across the a-arm)..

Damn rookies lol

[madtown77]

One important note, as a design judge at MIS this year, I saw a lot of first year teams. Make sure you have some documentation of what ideas you had along the way: good and bad (especially the bad, but you don't have to show us those if you don't want to ).

This will help your program develop a lot faster. I agree with the other posters, just design and build a reliable car to use as a basis for the future, we all had to start somewhere.

Please bring some stuff with you when you talk to the judges. We will give good feedback to you, but it makes it a lot easier when you at least have some design notebooks with hand drawings in them showing us how you attacked the problem.

As far as FEA goes, best bet is Ansys. Its relatively easy to setup the model and, more importantly, to make incremental changes in the tube location and loading forces and runs very quickly. Its also one of the best FEA packages around. If your school doesn't have it just do what most teams do and pirate it

[G37Sam]

haha thanks for the suggestions, luckily our school has licenses to ANSYS, Solidworks and AutoDesk Inventor, so software wise we're good. The theoretical support though is lacking in the vehicle design and race tech, that's why I feel like I'm on my own.

One question if I may, do you have 2011 rules for the FSAE competition? I couldn't seem to find them on the SAE website. If they're not out yet, do you know if there's been any major changes to chassis & suspension design?

Appreciate your feedback madtown

[bettonracing]

I hate to be the Autogyro for this thread (No ESRU's, but tangential topic), but I highly recommend You properly assess & decide on Your program's goals - especially with other equal level (and especially upper level) management within the structure (e.g. senior faculty).

Building a reliable car to make it to competition is sound advice for short term goals, but with FSAE becoming highly saturated (entries for major US competitions are usually filled within minutes) and "FSAE team member" becoming as common as bad grammar on new-graduate resumes, there may be long term advantages to alternate approaches.

Consider a [somewhat] fictitous comparison of finishing competition ~70th out of 120 with a reliable car vs. finishing ~70th out of 120 with an unreliable car equipped with contantly variable torque vectoring. Both approaches have merits.

Examples of longer term effects You may consider are:
-Team member graduates' resumes
-Program funding (i.e. internal)
-Program sponsorship (i.e. external)
-Program recruiting

Examples of alternative program approaches (to the "ole reliable") are:
-Targeting & developing 'new' technologies (e.g. torque vectoring, Dual clutch transmission)
-Targeting 'old', but interesting technologies (e.g. WWU's V8 engine, 4wd)
-Targeting one part of the competition (lap times? accel? static?)
-Targeting a local sponsor & helping to develop their product (e.g. a local composites supplier)

You should be able to determine other opportunities. Again, some [scientific] form of risk analysis (such as FMEA) may help You make this decision.


All that said, one of the best team morale building exercises is to take "good ole Betsy" and have everybody do a few laps in the parking lot. And obviously a car that never accomplishes anything - since it's never running properly - is the most counterproductive of all.


Best Regards,

H. Kurt Betton

[marcush.]

I firmly believe nobody would build a car that is going to break down...so surely right at the start of a project you have to dig deep to find out about your weaknesses and I highly recommend to start the FMEA thing on day one and live the risk management.
A car that is not able to withstand the tests is doing a lot of harm to reputation of all people involved not only those who messed up .In the end all will have to
stand up for the final product..loosing a wheel or other embarassing things that happen.

[madtown77]

..loosing a wheel or other embarassing things that happen.

Even the best of us have done that at some point...and are always surprised that our best designs have failed us.

Based on what are usually the resources of a new team, I think torque vectoring and such are lofty goals. Even for established teams it is difficult. I am in the camp of get a baseline car and make sure it passes rules. Documentation is really the key because you will find a lot of things that work and a lot that don't and its important not to repeat past mistakes in future years.

That being said, the car shouldn't weigh 800 lbs! If you want to set goals, try a weight and a power output because these dictate much of how well you will do in the competition.

As a first year team you probably have a dozen team members (and if you think you have more now, just wait until 5AM on a Saturday morning when you look around at who is still in the shop building the car).

[Jersey Tom]

as a design judge at MIS this year

How'd ya swing that? Thought there was something about having to be in industry for 5 years?

Maybe I'll have to ask Doug or Claude about it next time I see em...

[madtown77]

as a design judge at MIS this year

How'd ya swing that? Thought there was something about having to be in industry for 5 years?

That was my impression as well. I was originally going to be there to "support" the judges, but they seem to have come up a bit short in volunteers. This in part is due to the new format for judging (12 qroups instead of 10, with more to come next year).

Each judging group had at least one "rookie" judge. Most of us were only a year or so out of the competition as students, with a few exceptions. Part of this is I believe is to get a better perspective to current judges from those who actually built these cars recently. We had full judging responsibility in the preliminary round. Some were also there for semifinals.

Important to note that none of us that were recent graduates were judging our old schools. Though I did hassle them a bit...

[bettonracing]

Even the best of us have done that at some point...and are always surprised that our best designs have failed us.

Based on what are usually the resources of a new team, I think torque vectoring and such are lofty goals. Even for established teams it is difficult. I am in the camp of get a baseline car and make sure it passes rules. Documentation is really the key because you will find a lot of things that work and a lot that don't and its important not to repeat past mistakes in future years.

That being said, the car shouldn't weigh 800 lbs! If you want to set goals, try a weight and a power output because these dictate much of how well you will do in the competition.

Just to be sure it's clear to the OP, torque vectoring was just used as a random example. Majority of the knowledge needed to design torque vectoring would need to be derived from empirical data - a good argument for having a "good ole Betsy" from which to get Your data...

I could have used a more practical (relevant?) example such as an aluminium panel (monocoque) chassis. Absolute practicality is debatable, but it's likely more practical for some new teams than a torque vectoring system.

Moral of the story: Competition needs not be the only team goal.

Regards,

H. Kurt Betton

P.S. The point about quantity of team members is VERY true. Usually after a month or two You'll know for sure who'll be there for the long haul.

[madtown77]

Just to be sure it's clear to the OP, torque vectoring was just used as a random example.

...

I could have used a more practical (relevant?) example such as an aluminium panel (monocoque) chassis. Absolute practicality is debatable, but it's likely more practical for some new teams than a torque vectoring system.

Understood.

Aluminum monocoque? Been a few years sicne I've seen one but it can work (usually doesn't though )

I was thinking more like set a target for curb weight of 500 lbs wet (or under even). Most new teams show up over 600 and while overbuilding is better than underbuilding for your first car, it get a little ridiclous. Take a good look at tube frames from schools like Penn State and (biased?) Wisconsin (http://gallery.uwracing.com/main.php). The Penn State chassis is as lean as it gets (weight is 285 lbs wet!). Wisconsin is a heavier car (390) but makes a lot more power. Also remember, while the rules say "1 in. 0.089", it isn't needed everywhere.

Stay away from Inventor FYI .

[Jersey Tom]

I kinda liked Inventor more than Solidworks for handling large assemblies. Admittedly that was for spaceflight payloads and circa 2005.

[G37Sam]

I've been working with Solidworks for quite sometime and feel very comfortable with it.

Are the weights you guys referring to, using steel tubing? or were composites used?

[marcush.]

why not use alumium honeycomb in cut and fold technology..Patrick Head would love it!

[madtown77]

Both the above were steel space frames. A composite tub will save a bit of weight (frame alone in 2007 weighed ~60 lbs from steel, a composite one could be made for around 45 lbs.)

Still, you are talking 100x the complexity for a 15 lb reduction. This is part of the reason I hate the judges pushing the teams to CF monocoques...but I digress.

Ask Michigan State how the CF monocoque worked out for them last year. Unless you have an autoclave at your school or someone on the team who's daddy ownes one, I would avoid.

[madtown77]

One question if I may, do you have 2011 rules for the FSAE competition? I couldn't seem to find them on the SAE website. If they're not out yet, do you know if there's been any major changes to chassis & suspension design?

Rules when available will be on the SAE website. Usually these are posted right about this time of the year.

http://students.sae.org/competitions/fo ... ies/rules/

Chassis rules don't change a whole lot from year to year...unless someone found a new way to do something REALLY stupid. (last year we got a rule about not using the fuel tank as a structural member...thought that one would have been obvious)