FSAE-A 2012 Curiosity...

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mep
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Joined: 11 Oct 2003, 15:48
Location: Germany

Re: FSAE-A 2012 Curiosity...

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Just by looking on the pictures posted here it seems to me these metal plates are their springs. That’s why they don’t have any springs around their dampers. The floor is attached directly to the suspension, which means this spring plate is probably rather soft. I wonder how they supported roll, if they did at all because this spring plate will only support heave. Maybe the lack of an anti-roll-spring is a reason why they did not run any events. I don’t really see how the different suspension modes are controlled. Apart from that must the unsprung weight by immense heavy.
Plus the floor will still not work. Actually, what is funny is that I struggle to see where the front and rear of the car is.

gato azul
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Joined: 02 Feb 2012, 14:39

Re: FSAE-A 2012 Curiosity...

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mep wrote:I wonder how they supported roll, if they did at all because this spring plate will only support heave. Maybe the lack of an anti-roll-spring is a reason why they did not run any events. I don’t really see how the different suspension modes are controlled.

If you look at the 2nd picture at full resolution, you will see that they run a anti roll bar (close to the CoG-> around the driver seat). You see the ARB connecting to the floor/undertray. You can see in the first photo, that there are some brackets on the floor/undertray around halfway front to rear, that is possible the location where the ARB drop link joins the floor.
I also think, that they run a sort of twin chassis concept with double beam axles.

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mep
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Joined: 11 Oct 2003, 15:48
Location: Germany

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Yes possible. I was wondering what those levers are for. But if you look at the picture showing the front of the car, left and right side looks asymmetric. Anyway, this means they just have 1 anti-roll bar in the centre of the car, which does not really allow having different adjustments between front and rear. What I read out of the pictures is that they have an absolutely rigid suspension unit connecting all for wheels. The chassis (driver, engine, gearbox) is sprung relative to that. Seriously, I doubt that is the idea of having a suspension on a vehicle. They could as well have just placed the driver on a pillow to feel more comfortable and have anything rigid else rigid. The tires are not able to follow road disturbances individually. Load transfer is not ideal; neither is camber changing during cornering. I even think a conventional design would be lighter. Connecting the ARB in the middle of the floor means the floor has to be very stiff. Also this beam structure connecting left and right wheels looks very heavy.
The point of connecting the floor to the wheels directly is that the springs don’t need to carry the high aero loads and thus can be lighter. But a Formula Student car is not quick enough to generate enough downforce to have any advantage of this.

Even if I am a bit harsh with that idea, I think we should have more topics like that on this forum.

RacingManiac
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Joined: 22 Nov 2004, 02:29

Re: FSAE-A 2012 Curiosity...

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Go Kart works quite well without suspension, but the rule in FSAE does not allow a "suspension-less" kart. This might well be the idea I think....The "wheels" are able to travel the "+/- 25mm" that the rule requires. Most of the FSAE even takes place on surface that's quite smooth(relatively speaking). They can probably get away without much suspension use at all...

If any teams understand the need for certain type of suspension design in FSAE, I think UWA is quite near the top of that list....their last car is quite conceptually the opposite to this....

RacingManiac
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Joined: 22 Nov 2004, 02:29

Re: FSAE-A 2012 Curiosity...

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The car did not pass tech. The car is really not finished...

gato azul
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Joined: 02 Feb 2012, 14:39

Re: FSAE-A 2012 Curiosity...

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mep wrote:Yes possible. I was wondering what those levers are for. But if you look at the picture showing the front of the car, left and right side looks asymmetric. Anyway, this means they just have 1 anti-roll bar in the centre of the car, which does not really allow having different adjustments between front and rear. What I read out of the pictures is that they have an absolutely rigid suspension unit connecting all for wheels. The chassis (driver, engine, gearbox) is sprung relative to that. Seriously, I doubt that is the idea of having a suspension on a vehicle. They could as well have just placed the driver on a pillow to feel more comfortable and have anything rigid else rigid. The tires are not able to follow road disturbances individually. Load transfer is not ideal; neither is camber changing during cornering. I even think a conventional design would be lighter. Connecting the ARB in the middle of the floor means the floor has to be very stiff. Also this beam structure connecting left and right wheels looks very heavy.
The point of connecting the floor to the wheels directly is that the springs don’t need to carry the high aero loads and thus can be lighter. But a Formula Student car is not quick enough to generate enough downforce to have any advantage of this.

Even if I am a bit harsh with that idea, I think we should have more topics like that on this forum.
I think. that what you see from the front are two different levers.
on the RHS ( in direction of the cars heading) you see, IMHO, the connection/droop link of the central ARB, while the lever you see on the LHS and in the side view picture, seems to be the shift linkage. But I could be wrong.

with a central ARB, you could still adjust/tune roll couple/LLTD by choosing the point where the droop link attaches to the
floor/undertray. I think, that is what they are doing, but again I could be wrong, it's just a possibility which IMO would work.
I don't think, that the undertray is very stiff in twist/torsion/wrap, that will allow the front and rear axle to assume a twisted/wraped position towards each other. Think of it as a torsional spring.
Now by connecting the central ARB more towards one axle, you will increase the rate of this torsional spring in regard to the axle which is closer ( like changing the length of a ARB for a given diameter).
Looking at the brackets attached to the floor, to me it looks like, that they allow for different mounting positions (backwards/forwards). This would, IMHO, be a option to alter the LLTD.
Using only one ARB would reduce the part count and thereby weight/mass and friction. Another small "advantage" would/could be, that you keep your overall roll stiffness (roll rate) constant, while you can alter/change the distribution by moving the attachment point of the droop link on the floor/undertray in longitudinal direction.
Most solutions employing two ARB's will not only change the LLTD, they change also the overall roll stiffness ( e.g. that happens if you only stiffen/soften one ARB at a time)

if their is an advantage of a beam axle, then it is good camber control. Why you can't have camber gain with this design (in roll) you also don't lose camber in roll in the first place. I would see that as one of the upsides of this concept.

From an aero point of view, it's not only that you don't need to pass the aero loads through the suspension, and therefor could run softer, you also have more or less constant ride height & angle of attack for your undertray ( ignoring tyre squash for a moment)

I agree wholeheartly with your last point mep

I think you will find some ideas of this concept in the mentioned car.
http://es.scribd.com/doc/49358553/balanced-suspension

to make this idea/concept work
Image

Lycoming
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Joined: 25 Aug 2011, 22:58

Re: FSAE-A 2012 Curiosity...

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gato azul wrote: if their is an advantage of a beam axle, then it is good camber control. Why you can't have camber gain with this design (in roll) you also don't lose camber in roll in the first place. I would see that as one of the upsides of this concept.
Ok, but how sensitive are the tyres to camber change? If they're relatively insensitive to camber, then this upside holds less weight against its downsides.
gato azul wrote: From an aero point of view, it's not only that you don't need to pass the aero loads through the suspension, and therefor could run softer, you also have more or less constant ride height & angle of attack for your undertray ( ignoring tyre squash for a moment)
With the tires that they're using, can you safely neglect tyre deflection?

gato azul
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Joined: 02 Feb 2012, 14:39

Re: FSAE-A 2012 Curiosity...

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regards to camber sensitivity:
-fair point, and I don't know how camber sensitive these tyres are, but would have yet to see a tyre who is totally insensitive to camber change. Nevertheless, your statement is correct, camber control would be more benefical on
a car with more camber sensitive tyres.
- it"s a bit like saying "high unsprung weight is not good", how much of a problem is this if you race on a smooth track?
As all things is a tradeoff between different objectives, and you would need to do (or at least should) do a sensitivity study on the parameters influencing the design. Then you can weight the different parameters and compare different options in a MCDA.

tyre squash:
-I did not mean that you can ignore it in global/overall terms, I just but this cavet in parathesis, because this assumption is needed to make the first part correct, as it was written.

For all practical purpose, the car will roll/pitch/heave on it's tyres, and thereby change the position of the undertray to the ground. Having said this, any car (with or without suspension) will do this, but the change in attitude in respekt to the ground would be even higher, if you would need to accomodate the suspension movement as well.(fixing the tray to the sprung part, as in a conventional race car)

I do not have an opinion, if this SAE car is "good" or "bad", that remains to be seen and lays in the eye of the beholder.
I just think, that there is some reasoning behind this concept, and that some of this reasoning is not "totally stupid".
That does not mean, that it will be a "world beater" nor does it mean, it"s the only possible way to go.
I'm with JT on this one, I like that they put some thought into it, and came up with a different concept to the "main stream" double wishbone solution. Would be nice if someone from this team could provide some more input, and adress the things which have come up here, like camber sensitivity of the tyre, how heavy are the axles, how stiff, what is the torsional stiffness of the undertray etc. etc.
I wish them the best on their way, it may not be the "be all /end all" solution, but I do think, that it is/was worth the try.

Lycoming
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Joined: 25 Aug 2011, 22:58

Re: FSAE-A 2012 Curiosity...

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gato azul wrote: tyre squash:
-I did not mean that you can ignore it in global/overall terms, I just but this cavet in parathesis, because this assumption is needed to make the first part correct, as it was written.

For all practical purpose, the car will roll/pitch/heave on it's tyres, and thereby change the position of the undertray to the ground. Having said this, any car (with or without suspension) will do this, but the change in attitude in respekt to the ground would be even higher, if you would need to accomodate the suspension movement as well.(fixing the tray to the sprung part, as in a conventional race car)
I understand, I just posted that comment because If you've been to competition or had the chance to see the cars drive up close, you would see that between different types of tires commonly used is fsae, the amount of sidewall stiffness can vary a lot.

gato azul
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Joined: 02 Feb 2012, 14:39

Re: FSAE-A 2012 Curiosity...

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here is another photo, where you can see the ARB & it's attachment point to the undertray more clearly.

Image

and another photo of their "springing device"

Image

remydio
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Joined: 17 Mar 2011, 12:27

Re: FSAE-A 2012 Curiosity...

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The front suspension system reminds me the front susp system au 1/12eme racing cars from the Manufacturer "Corally" years ago they were using something really near than that.
We had to use different "plates" of different thickness in order to adjust the smoothness of the front suspension system.
if that makes sense.

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flynfrog
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Joined: 23 Mar 2006, 22:31

Re: FSAE-A 2012 Curiosity...

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I was just thinking they reminded me of a pan car suspension.

Image

remydio
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Joined: 17 Mar 2011, 12:27

Re: FSAE-A 2012 Curiosity...

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That is not this car i was talking about but more this one :

http://corally12.nl/Eng/SP12/SP12.htm

Smokes
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Joined: 30 Mar 2010, 17:47

Re: FSAE-A 2012 Curiosity...

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so they are using a W bar and a sliding kingpin suspension. I alway thought would be the quick option to go around a track for FSAE