Vehicle Status 2012

[Thrainer]

Awesome! Keep the pictures coming, please (twitter, facebook). I didn't expect such an early announcement of the aero package. I hope she will weigh less than 180 kg, not more.

[Paul Achard]

Kopito, how do you package your inboard cv joints, if at all? Very impressive, what with carbon-ceramic brake discs!

[Thrainer]

Zurich's first attempt at aero... and first 10" wheels since 2007:


Plooba, they're using tripod joints, the housings of which you see on pages 5 and 6. The aluminium tripod housing is attached to the 4th gear of the transmission. Is that what you were asking?

Regards
Thomas

[Paul Achard]

The packaging just seemed too tight to me... are the tripod housings bonded to the halfshafts (RCV Performace-style)?

[Mike Cook]

Let me know how much lateral stiffness that wing mounting has.

[Konrad]

Hi Mike
It's hard to give you exact numbers since the mounting consists of several composite parts. Therefore it's not that easy to predict the global stiffness by simulations. The upper front wing is laterally supported by the Moncoque directly. The lower front wing is mounted to the moncoque using milled steel parts (lateral stiffness in the order of 5kN/mm). Regarding the rear wing assembly supports the lateral stiffness would be approximately in the order of 2kN/mm. What do you think about it?
Regards, Konrad

[Mike Cook]

The front wing is probably ok. Both us and monash run a similar rear wing mounting and it really needs to be over constrained to not move. We added another lateral strut between the bottom a-arm mounting point and the opposite side suction side mount. If you think of your current setup as a four link rear end from a Nascar, basically you need to add a panhard bar. Any small compliance will add up to big movements of the rear wing. Trust me.

[Konrad]

You are absolutely right. We know that this might be a possible problem. Therefore we will finish most of the necessary parts for this additional strut at the same time as the other aero components. Nevertheless we belive that we won't need to mount it, due to the slightly different wheelside mounting of the rear wing support compared to you and Monash...
What do you think about having only one wing suspended? Due to the possible disadvantages we are ready to mount the rear wing onto the monocoque instead to the upright.

[Mike Cook]

The main downsides I can see to having only the front wing mounted to the monocoque are:

1) At high speed the car will nose dive, so that when you hit the brakes you will definitely slap the wing on the ground.

2) As speed increases the chassis will rake. The front roll center will decrease. From a weight transer standpoint, this will increase front grip.

3) As the front squats, the front wing gets closer to the ground it will probably increase front df, up until you choke the flow off.

4) If you only increase the front spring rate to try and help front squat, your car will push like a fat pig on the slower manuevers. It would possibly make the car more neutral at high speed.

5) Increased body rake will probably screw up your undertray. I'm not sure how sensetive your tray is to pitch.

6) As modeled, your front wing looks very low to the ground. When you roll, I imagine the endplates will hit badly. Even with unsprung wings, you have to deal with tire squish which can be considerable so we can only run so low too.

I think overall, your car will end up being way too loose at high speed, which is going to make it very unstable. For FSAE it might not really be an issue, but I tend to look our cars very loose at low speed and tighten up the faster it gets. This is definitely easier for the drivers. You could run bump stops in the front, and this could fix a lot of things. The highest speed corner at FSAE is probably about 35-40mph, so as long as you set it up to not be on the bumpstops at this speed the suspension should still handle ok. Good luck.

Mike

[Konrad]

Thank you for your explanations. We had an intensive discussion about this topic at the beginnig of the year. Finally it ended up that we cannot make a credible prediction with our CFD simulation about how much the (suspended) undertray counteracts the effect of the front wing if at all. In the extreme case you are describing it would be definetely easier to run the rear wing suspended too. Maybe someone has some interesting (experimental) data about this topic? - In any case we are looking forward to gain more understanding of our system using the automitive wind tunnel in may =).