Open for suggestion and criticism first car

Hello Guys,

I'm the team leader and my university in Brasil just implemented the FSAE Project. My first proposal was to make a tubular frame so that way we can acquire experience and than move up to the monocoque. But the university was very incisive about doing the monocoque. So I'm here to ask you guys some advice and/or criticism. We're going for the electric design. Because the project just started this month, we have some design objectives but we don't have yet the motor, the batteries, control unit.

http://flic.kr/p/e1Fvqf
http://flic.kr/p/e1zQx4
http://flic.kr/p/e1zQtz
http://flic.kr/p/e1FvdG
http://flic.kr/p/e1FvuE
http://flic.kr/p/e1FvAw
http://flic.kr/p/e1FvEE

Thanks in advance.

Don't have rod-ends in bending.

I also recommend telling your university that a spaceframe is much, MUCH better for a first year team.

Ben

Nice start. There are two basic things that pop out at me at first glance:

1. The driver looks stuffed in there. At the very least, he's going to want more elbow room. It's wise for any new team to build a "seating buck" or "mock chassis" to work out some realistic driver ergonomics and packaging. You will save a lot of resources by doing that early on, thus avoiding rework when you realize the driver simply can't fit or drive properly. It's also worth seeking out as many "real" racecars as you can to see how certain positions feel to you. Some cars are *much* more comfortable than others. A comfortable driver is usually a quick driver.

2. If you're going to use Catia, do yourself a favor and learn as much as you can about the powerful surfacing capabilities that the program offers. Doing a composite structure is cool and all, but designing it as a series of slab panels with constant radius curves between them is a shame. Learn about curvature and acceleration, and how they can be used to make more attractive shapes. It's not really "mechanical engineering" per se, but it certainly has its place within the automotive realm. Understanding that sort of surface design will also open up the world of efficient aerodynamics to you too.

-Kirk

Go visit a team in Brazil that has a good history of international competition so you can touch and feel the car to get a better idea of what you are doing.

Agree with Kirk.
Begin with a very crude full scale mock up.

Get some PVC electrical conduit and a hot air gun to bend the stuff, and put together a rough skeletal outline frame to locate all the major components.
A physical 3D frame you can actually walk around, sit in, and view from any angle will be very helpful in tweaking your CAD dimensions to fit a human driver.

Cardboard and duct tape make a terrific monocoque.

If you can fabricate a torsionally stiff chassis out of PVC conduit and cardboard, you are definitely on the right track.
It's fast, cheap, fun, and very instructive.

Quote:

---

Originally posted by Warpspeed:
Agree with Kirk.
Begin with a very crude full scale mock up.

Get some PVC electrical conduit and a hot air gun to bend the stuff, and put together a rough skeletal outline frame to locate all the major components.
A physical 3D frame you can actually walk around, sit in, and view from any angle will be very helpful in tweaking your CAD dimensions to fit a human driver.

Cardboard and duct tape make a terrific monocoque.

If you can fabricate a torsionally stiff chassis out of PVC conduit and cardboard, you are definitely on the right track.
It's fast, cheap, fun, and very instructive.

---

this would make a GREAT inter-team competition. We make our actual "racecars" but It'd be hilarious to see what kind of a soapbox car we could make given only wood, screws, PVC and cardboard.....with some duct tape obviously

I agree with all said above, and would like to add :

If you really have to make a monocoque, maybe the Oxford Brookes way of making it (folding a sandwich material instead of using molds) can make it a bit easier? To me it seems that it would be easier to make a new, revised monocoque if you realise that there is some problem that can't be fixed otherwise.

Do you have any contact with other Brazilian FSAE teams? If not; make contacts as soon as possible! When we started, we had one guy that had FSAE experience, contacts with the other Swedish teams and a couple of us had visited teams and seen actual cars/facilites and talked to people involved. That helps a lot! Experience in any way, shape or form is needed.

Also, measure everyone that wants to drive and make CAD models that you know are accurate of the max/min length that the rules dictate, as well as your standard driver. As Kirk said, it's not that fun to have to try and "find" a couple of centimeters somewhere when the chassis is produced and you realise that something doesn't add up ...

When looking at the car itself, it seems to be a bit too high and/or tight around the drivers sides.

A couple of centimeters, or a hard surface right where your knees or elbows keep wanting to go can be no fun at all to drive.

At Case Western, we built a plywood mockup of the cockpit and the rear-end packaging before we built our chassis.

We really should've just added the steel roll hoops and raced the plywood car!

Hi Thiago,

It was very brave of you to offer your design for our feedbacck, and for this you have my full respect. Politely, I offer the following:

1. As you will get deeper into your design, you will realize that the chassis is just a big bracket, that holds all the components where they need to be. Therefore from a mechanical design point of view, design your chassis last, after you know where everything else needs to go.
From a marketing point of view, design your chassis first - so you have something to "sell".
From a real world point of view - do both. Use your first iteration chassis to draw attention, but do not marry yourself to that first design. Be prepared to change, and iterate.

2. From top view, your rear a-arms are at a very shallow included angle - and will experience huge loads under cornering. Be careful

3. This is your project, your design, for your education. That is priority one for your team. Do not let yourselves become free labour building a showpiece for your school. I've been in a situation where the latter objective took priority over the former. It is a horrible place to be.

Unis are notoriously heavy on the ground with technophiles, who will often have a marvellous repertoire of well-practised arguments as to why their pet technology needs to be on your car. Usually, such people have never designed anything more complex than the string of words coming out of their mouths.

If the uni is dictating a design solution, then walk away until they have delivered that solution. They demand a carbon tub? OK, they can deliver you a carbon tub. Let them wear the consequences of their decisions. Do NOT let yourself get in a position where the uni makes the decisions and you become their lackeys. I can assure you, when the fit hits the shan and their decision is proven a poor one, you dont want to be in any way exposed when they start deflecting the blame.

Good luck!