Hi Rinaz,
I can't really post many close up technical pix. You must realise I an the Technical Advisor to the Australian and German events, and have been a Design Judge at FSAE and Formula Student.
As such I am well known and trusted by many teams and am always welcome in their tent or at their University. This means I have access to all sorts of stuff and the teams trust me. To simply post stuff over the internet would not be fair.
I agree that in most cases it would make no difference, and I accept Denny's POV that anything at the event is public knowledge, but I also know that often I see stuff or I am told stuff that is not really for public consumption.
Cheers
Pat

On that note, anybody else who was at the competition and willing to share pictures with the rest of the community?

p/s: pat, im very much aware of your position, but i guess it doesnt hurt to ask

Frank,

It is a loss to FSAE-A that you are leaving. You have done some great work with Queensland. The build quality of the last few UQ cars has been outstanding.

Good Luck on wherever life takes you.

Cheers,

Kev

all those cars are pure sex, awsome pictures!

mini baja? http://evilallianceracing.com/ipw-web/gallery/FSAE-AUS05/P2190608

I saw an antena sticking off UWA's roll hoop, either their car was remote control or they have some cool videos to share.

Storbeck,

i thought it would be k*x at each wheel because the bumped wheel would compress the spring x, and that would create a force k*x on the bumped wheel.

the equal and opposite load would be applied to the unbumped rocker.

i might be missing something simple though... my eyes just can't see it!!!

cheers,
Scott

Scotty, Storbeck,

"Spring rate", usually "K", refers to a relationship between force and displacement. What force? What displacement?

The type of spring being considered here is one that interconnects two wheels. A name for this type of spring might be an "end-pair-anti-similar-motion" spring, or more briefly, an "end-pair Z-bar". This is in contrast to a conventional ARB, which is an "end-pair-anti-different-motion" spring, or an "end-pair U-bar".

With either of these two types of spring, the force they exert on one wheelprint depends on the positions of BOTH wheelprints (the "position" is the vertical height of the wheelprint relative to the body). So, Force-on-Left-Wheelprint = Function(PositionLW, PositionRW), and similarly for the right wheelprint. This functional relationship is usually NOT linear. Non-linearity can be a problem, or it can be an advantage.

Because of leverages in the connecting linkage between wheelprint and the actual spring, the forces and displacements as measured at different points in the linkage can vary a lot from the F's and X's at the wheelprints. So it is important to be consistent where these F&X's are measured. Probably the most sensible place is at the wheelprint. Refering to the "force/displacement" at the actual coilspring can be confusing (cf. "wheel rate" and "spring rate").

A common type of third-spring ("end-pair Z-bar"), works a bit like a beam-axle with a single coilspring at its centre which supports that end of the car against bounce, but not against roll (eg. similar to the linkage on the front of UWA'04?). If the coilspring itself has stiffness K, and the linkage is "linear", then;

ForceLW = (K/4 x PositionLW) + (K/4 x PositionRW),

and similarly for the right wheelprint.

It is also possible, and very beneficial , to have springs that interconnect all wheels of the vehicle (and there might be more than four wheels). In this case the force on any one wheelprint depends on the positions of all the other wheelprints.

Z

http://evilallianceracing.com/ipw-web/gallery/albums/FSAE-AUS05/P2170102.jpg

Are those rain tires?

kev (and all UWA guys),
sweet suspension system there man. caused a few turned heads and debates not only on the forums but amongst my team and probably many others out there. i like their website quote, "so good they banned it".
i do however still have a question or two. from a little visual inspection and reading this and other threads i have a good idea how your system works in one wheel motion. my question is what controls your roll? does your kinetic system read the travel sensors and engage a ton of damping under roll? i read on another thread (although it sounded pretty hearsay) that you can do the judge's push/pull on the roll hoop and have the car not budge, but be able to lift one wheel of the ground fine. is this true? the reason i ask is because the way your "arb" is setup its more like an anti dive bar and in roll it would actually promote more roll due to the inside wheel springs restoring force pushing the "arb" to pivot about the point on the 3rd spring and cause the car to roll over farther. of course the more your roll the more force your outside spring is exerting and the opposite for the inside spring, so it essentially becomes negligible.
so are you just kept flat hydraulically or am i missing something here?
also do you have all four wheels connected within the system or is the front isolated from the rear? i can't tell from any of the pics.
but yeah, nice work gentlemen, its good to see an "innovative" (that word is getting more and more loaded as these forum discussions continue) car take numero uno. also good job on the carbon tub, us composite guys need to show the steelies what's what (do i dare bring up the carbon/steel chassis debate/fistfight...?)
again, nice work and congrats on the win.

Storbeck, yes they are - Goodyear 20x7 R065, and they look like they're working hard in that photo. The clerk of course made it clear in the day's briefing that on account of the patchy weather we were allowed to use either tyre up until the track was declared wet, when we would be forced to use wets. I can't be sure, but I think we were the only team that took the option to run wets for skidpan/accel.

John, the third spring (connecting rockers horizontally at front and rear, visible at rear only) does not act in roll. It behaves as Z explained earlier, as a single central spring on a beam axle. There are no pro-roll effects from the 3rd spring, and there's a good shot of the rear spring in the link in Storbeck's post.

The roll resistance is provided by corner springs and by the springing effect of the accumulators, as the interconnected dampers attempt to pump them full of fluid when the car rolls - and the gas pressure resists this fluid flow and thus resists roll. During warp motions, the fluid gets largely pumped between the four dampers, so that the accumulator pressure doesn't resist the motion. This is how it can be all nimbly-pimbly in warp, and stiff in roll.

The entire system is passive, the sensors are there as part of the DAQ system and they don't affect how the suspension works. And yes, all four corners are interconnected.

Cheers,
Nick

Thanks for the kind words Kev,

I got to say again that the UWA car TOTALLY OUTCLASSED EVERYONE ELSE.

I think that car is a testament to the legacy left by Kev,
and a testament to the UWA team and faculty's commitment to become world-class competitors.

It was truly fascinating to watch the UWA car from the dynamic staging area.
I'm guessing the car makes drivers look better than they are.
I'd be so stoked to be a part of UWA's team.

As for UQ's car, here's about as much info about it I can give in one post:

The electrics are all Deutsch (we're sponsored by Deutsch).
There's a PCB that replaces relays.
The Wheels are carbon outer, 7075 centre, and 7075 fasteners (glued and bolted together).
I'm not allowed to tell you how we made the outers.

Dynamically, no secrets there, a fairy stiff 4130 chassis,
we concentrated on removing compliances from bearing compliments.
Glued the 0.7mm ally floorpan.

The spool ONLY works when you've got high levels of grip, and on a fast(ish) course.
When it works it really works, otherwise you're doomed.
Spools are garbage in the wet.

No suspension data logging, just trial and error.
Most importantly good driver feedback.
Shocks are rebuilt Risse's and set on a dyno.
About 50-75% critical in bump, and critical in rebound.
There's a driver's adjustable blade ARB on the front,
but we didn't use it at the competition, because there's no-way-near
as much grip as we get on our regular testing tracks.

It's a very simple car, with good attention to detail.
It's done a LOT of miles (the engine and manifolds are 3 years old).
There is NO secret engine mods,
in fact we've never even taken the cylinder head off
(no-one on the 05 team would know how).
There's a nifty dry sump, and MoTeC traction and launch control.
There's a 5000PSI carbon fibre bottle holding air to drive the shifter
(open loop control only, we recon it needs to be controlled).
The bottle is only run at 3500PSI.
The low pressure lines use Festo equipment, and is run at 8 Bar.
The gearbox is standard.

These are the actual parameters used in the enduro.

There was 1.75 degrees of camber front and rear, 7" hoosiers. at 20PSI (hot pressure)

0.5deg of toe out (per wheel) at the front
and 0.25 deg of toe in (per wheel) at the rear

These spreadsheets are accurate for what was run during the enduro.

http://www.uq.edu.au/fsae/frank/UQ_Suspension.xls
http://www.uq.edu.au/fsae/frank/UQ_Traction.xls

Finally, I must thank Mark Fenning,
for running the team while working a full time job.

Mark also managed to organise the whole project to be done
"just in time", and ON BUDGET (a first for our team)

Shout outs to Mathew Bryson from FERRA engineering in Brisbane,
thanks for the CNC turning work.
(world class work, bound to make your uni tradesman jealous)

Shout outs to UQ tradesman Neil Duncan,
thanks for letting me CNC mill all that stuff.
Neil taught me heaps about CNC.

Shout outs again to Pat Clarke, he's a great guy.
If you're new to FSAE, listen to Pat.

Hi Frank,

Your right, the car does make the drivers look a lot better than what they are. This is something we have focused on for a few years now because at the end of the day, we are amateurs.
Having said that though, a lot of time and effort is put into driver training and it is not often recognised as a strong team contribution, despite the hours involved.
We were simply thrilled that having driven the car for a few minutes (literally!) before comp, it had a setup that was a pleasure to drive, rather than a struggle. I guess Nick and the dynamics team can be thanked for that.

Cheers,

Mike.

P.S. Scott, I did win the bet, its sitting in my hot little hand as we speak, I mean slur.. I mean... I forgot.

Awe Shucks Frank, does that mean I have to buy you a beer next time I'm in Brisbane ?

And for those who haven't had the pleasure to meet Frank, he's the guy in the shades wearing proof positive of his multiple personalities
http://evilallianceracing.com/ipw-web/gallery/FSAE-AUS05/P2180173
Good luck in your endeavours Frank
Cheers
Pat

i dont mean to say UWA drivers were not good, they were excelent! (be very scared USA)

the car made them look even better, it looked to be a pleasure to drive

yes Pat, you do have to buy me a beer

nick,
thanks for the reply. i perhaps was a bit ambiguous in my post. i realise and understand that the third spring doesn't act in roll, what i meant was the following: when a car with your particular type of "arb" setup is sitting static, both (i'll talk about the front only for now) wheel springs will be compressed x amount due to the weight of the vehicle. under (steady state) roll the outside wheel spring will be compressed more than x, while the insde wheel spring will be compressed less than x. on a car with just two wheel springs and no ARBs the inside wheel will just hang out on the ground or sometimes even lift off the ground depending on the magnitude of the roll and your wheel travel limits. on your car the two wheel springs are connected about the pivot on the third spring. when i said your setup would promote more roll i was referring to the inside wheel spring, not the third spring. as the outside wheel spring compresses in roll, the inside wheel spring will be expanding back to its neutral position while exerting that force on your "arb", which will in turn pivot about the point on the third spring and push the outside wheel spring to compress more. so it seems like if you took the arb off your car it would roll less (by a very small amount) due to the inside wheel spring not pushing it down more.
assuming the third spring is the same K as the two wheel springs, it seems that under one wheel bump you get 1.5K for a spring rate, in two wheel bump you get 3K for a spring rate (1.5K each side) and in roll you get either just K or K(xoutsidecompressed - xinsideuncompressed). something must be wrong with this logic because you would think you want a higher K for roll than bump (hence the conventional ARBs). if it's just your dampers that takes care of the roll, cool, but removing dampers from the system, i can't find where my logic is flawed. let me know what you think.

I would like to get some information about this caliper.
http://evilallianceracing.com/ipw-web/gallery/FSAE-AUS05/P2180590

the team name should help for the moment.

thanks

flo

John,

You might be confusing the issue by calling the "extra" spring an "ARB". Better to call it a "third-spring", "anti-bounce-spring", or "anti-axle-bounce-mode-spring". It does nothing during body roll (its length doesn't change).

Also, in principle, the UWA suspension will work without the four corner springs (ie. the coilsprings at each wheel). The front and rear "third-springs" will control body bounce and pitch, while the interconnected dampers will control body roll. In practice, these springs might have to be made stiffer.

Here are some pics that might help explain these types of suspension. Look at the simplified system at top-left of the third (bottom) sketch. This has axle-bounce-mode springs at front and rear that act like UWA's "third-springs". The side-pair springs act like UWA's interconnected dampers.

IMO Kinetic's system is more complicated than necessary, but that's another story.

Z

wow.
i think i've managed to mislead people yet again. after i just finished saying that "i realise and understand that the third spring doesn't act in roll" it seems i need to be told that the third spring "does nothing during body roll". and when i said "arb" in my posts i wasn't referring to the third spring, but the the bar connecting the two wheel pushrods. ok i'll try to be very clear this time.

wheel spring=the springs attached to each wheel via the rocker
third spring=the third spring (or anti bounce spring)
anti dive bar push rods = the linkages from each rocker to the anti dive bar
anti dive bar= bar connecting each of the two pushrods and the third spring in the middle.
Kw=wheel spring rate
Kt=third spring rate
Xo=outside (in a roll) spring travel
Xi=inside (in a roll) spring travel

ok, i'll try and repeat what i said before in a more formulaic way. maybe i should first say for clarity that i know that the third spring does nothing in roll. i get it. sweet. and i'm leaving out the negatives in the hooke's law formulae due to laziness. and i assume that all anti roll or anti dive devices are one a 1:1 motion ratio to the springs (i know that's seldom the case but just for simplicity).
So,
1) during one wheel bump, the total spring rate you will attain will be Kw + Kt/2.
2) during two wheel bump, the total spring rate you will atain will be 2Kw + Kt, which is still Kw + Kt/2 for each of the two wheels.
3) during roll, the total FORCE resisting roll will be Kw*Xo - Kw*Xi.

this is because with the anti dive bar one wheel moving up will move the other one down. this is simply because the pivot on the third spring (which i know doesn't move, remember that i understand that the third spring does not move in roll, i get it, sweet) changes the direction of motion. is this not true? so under roll, the outside wheel spring will be compressed and will represent a resistive force of Kw*Xo. this is true for any no arb (or no anti dive bar) setup. where your system deviates from that is due to the anti dive bar changing the direction of motion, the inside wheel spring will represent a force opposed to that of the outside wheel spring. is this not true? so, with the inside wheel spring trying to restore itself to its static length, it will exert a force of Kw*Xi against the outside wheel spring (and make it want to roll over more than if the anti dive bar wasn't there).
so my final question is this, if the sole action of the anti dive bar is to give extra force in one or two wheel bump, then why not just replace the wheel springs with ones with a rate that is Kw + Kt/2 and get rid of the anti dive bar? that way you can have the same amount of force in bump, actually more resistive force in roll, and get rid of your third spring and anti dive bar. you can still have your dampers take care of the roll, of course.
so really what does the anti dive bar and third spring give you that can't be accomplished with different wheel springs?

Z, i like the drawings, they do help understand the concept of a z bar you keep bringing up. the difference i see here is that there are no mechanical linkages between the front and rear outside wheels to resist roll like all your drawings have.

everyone is welcome to point out particulars of the design i have missed or misunderstood. i'm eager to get a foothold on this system.
thanks guys.

John,

All this would be much easier with a simple sketching facility!

I think my misunderstanding of your previous post was to do with the end of the UWA car being considered. I was looking at the rear end (in many recent pics). I guess you are talking about the front end...

Here are some comments regarding your above post:

quote:

Originally posted by John Valerio:
...
1) during one wheel bump, the total spring rate you will attain will be Kw + Kt/2.
2) during two wheel bump, the total spring rate you will atain will be 2Kw + Kt, which is still Kw + Kt/2 for each of the two wheels.
3) during roll, the total FORCE resisting roll will be Kw*Xo - Kw*Xi.

1) What do you mean by "the total spring rate"? During one wheel bump, THAT WHEEL ONLY feels a spring rate = (force increase on that wheel)/(displacement of that wheel) = Kw + Kt/4. The adjacent wheel feels an increased force, but it doesn't move. If your "total spring rate" = (force increase on both wheels)/(combined displacement of both wheels - one of which, by definition, is zero), then, yes, it is Kw + Kt/2. As I posted before, you have to be clear about which forces/displacements you are talking about.

2) This part is correct but assumes "total spring rate" = (combined force increase of both wheels)/(average displacement of both wheels) with avg. disp. = (Xl+Xr)/2.

3) During roll a COUPLE resists the roll, not a "FORCE". A couple is two equal but oppositely directed forces separated by a distance (=~track) - which is a big difference.

quote:

...this is because with the anti dive bar one wheel moving up will move the other one down. this is simply because the pivot on the third spring (which i know doesn't move, remember that i understand that the third spring does not move in roll, i get it, sweet) changes the direction of motion. is this not true?

No. Not only does the "third spring" do nothing in roll, but the "anti dive bar" also does nothing. Take it away and the corner springs compress and extend just the same amount as with the bar there.

quote:

...due to the anti dive bar changing the direction of motion

Again, same comment as previous.

quote:

...so my final question is this, if the sole action of the anti dive bar is to give extra force in one or two wheel bump, then why not just replace the wheel springs with ones with a rate that is Kw + Kt/2 and get rid of the anti dive bar? that way you can have the same amount of force in bump, actually more resistive force in roll, and get rid of your third spring and anti dive bar.

The purpose of the anti dive bar and third spring (at both ends of the car) is to support the car in bounce and pitch, while offering NO RESISTANCE to roll or TWIST MOTIONS. If you get rid of the ADBs/3rd springs, and stiffen up the corner springs, then, yes, you get "more resistive force in roll". BUT (!!!), since "corner springs" give equal stiffness in all four 4-wheel modes (bounce, pitch, roll, and twist), by stiffening them you also get an equal INCREASE IN TWIST MODE STIFFNESS!!!

The whole point of suspensions like this is to have A SOFT TWIST MODE. This is A VERY IMPORTANT POINT!!!!!!!!!

quote:

...the difference i see here [UWA vs Z-bar sketches] is that there are no mechanical linkages [in UWA's car] between the front and rear outside wheels to resist roll like all your drawings have.

The UWA car has hydraulic connections between all its wheels. These are actuated via the dampers, and are roughly similar to the side-pair Z-bars. This hydraulic interconnection resists 4-wheel-roll-mode ONLY, and offers no resistance to the 4 wheels' bounce, pitch, or twist modes.

As a result, the only springs giving any twist mode stiffness to the UWA car are the relatively soft "corner" springs. Hence UWA's party trick of being able to easily lift one wheel off the ground while the other three wheels remain firmly planted.

BTW, I have no connection to the UWA team, and have never seen their Kinetic system up close. UWA team members are welcome to correct my explanations.

Z

Z, thanks for clarification of some of these points, there are a couple things you mentioned i would like more explanation if you don't mind. and yeah i can see how looking at the opposite end of the car would lead to some confusion.

quote:

quote:

Originally posted by John Valerio:
...
1) during one wheel bump, the total spring rate you will attain will be Kw + Kt/2.
2) during two wheel bump, the total spring rate you will atain will be 2Kw + Kt, which is still Kw + Kt/2 for each of the two wheels.
3) during roll, the total FORCE resisting roll will be Kw*Xo - Kw*Xi.

1) What do you mean by "the total spring rate"? During one wheel bump, THAT WHEEL ONLY feels a spring rate = Kw + Kt/4 (not Kw+Kt/2). The adjacent wheel feels an increased force, but it doesn't move. As I posted before, you have to be clear about which forces/displacements you are talking about. Just talking about "total spring rates" is probably counter-productive.

by total spring rate i meant the combination of the wheel spring and the third spring acting to resist movements of the wheel.
why is the spring rate Kw+Kt/4 and not Kw+Kt/2, if it's just a lever arm pivoting about a point twice as far away as the third spring is from the push rod mount?

other than that its all good. i didn't consider the twist mode when thinking about the dynamics of the situation. i can see how the third spring would prove useful in giving the soft twist and stiffer pitch and bounce modes.
thanks

quote:

Originally posted by John Valerio:
...by total spring rate i meant the combination of the wheel spring and the third spring acting to resist movements of the wheel.
why is the spring rate Kw+Kt/4 and not Kw+Kt/2, if it's just a lever arm pivoting about a point twice as far away as the third spring is from the push rod mount?

John,

(You got me half way through editing my last post. Some of it has changed.)

Briefly, the answer is because the third spring is acting with a motion ratio = 0.5, and wheel rate = spring rate x MR^2.

In more detail, say Kw = Kt = 100lbs/in, and one of the wheels bumps up 1 inch.

The corner spring of the bumped wheel compresses 1", so it increases in force by 100lbs, and this force is passed directly to the bumped wheel .

The third spring only compresses 1/2", so IT increases in force by 50lbs. But this 50lbs increase is then distributed between both wheels at 25lbs each.

The other, unbumped, corner spring stays the same length, so same force, no change.

So bumped wheel has +125lbs force for 1" of displacement, so its "single wheel bump spring rate" is Kw + Kt/4.

The unbumped wheel has +25lbs force for 0" displacement, so what is its "spring rate"?!

This is what I mean about being careful with defining which forces/displacements you are considering. With interconnecting springs the force on any one wheel is dependent on the displacements of all the interconnected wheels.

So in this example;

THIS-wheel's-force = ((Kw + Kt/4) x this-wheel's-displacement) + (Kt/4 x the-other-wheel's-displacement).

It is not possible to extract a simple "spring rate" from this equation.

Z