Sorry for the delay getting back to you. Yes I am a part of FSAE - just had a big deadline last week compiling a cost report/eBOM for the car, and also preparing for our car launch on Weds, so been a busy time!

From my limited experience I think you are right r.e. modern vs old VD teachings though. I didn't take the vehicle dynamics module but have a copy of the notes and it is very much a long list of equations that don't truly explain their limitations or assumptions. Seems like a good module to get an understanding of the basics and the terminology, but less good if you actually have to design anything.

Good point on the jacking effect due to toe - I remember now, it is essentially a function of your caster and kingpin inclination angles. I was probably thinking of the effects of bump steer through suspension travel on jacking.

Interesting thoughts on analysing full independent suspension. I haven't really looked into it in any detail as the added cost/mass/complexity/compliance don't really justify the move from double wishbone when you're only dealing with max +-30mm suspension travel. I'd have to have a bit more of a think on how that works and how you could calculate them if this is true.

There are a number of cars that in some way create a 'virtual' suspension. As far as I know, it's generally done on FWD cars to give zero scrub radius (I presume what you mean when you say the effect of kingpin inclination) and so minimal torque steer. I'm not sure the Citroen DS link you gave is an example of that though - that appears to just be a standard suspension with the two outboard joints positioned to give zero kingpin inclination and zero scrub radius?

On your last paragraph, you are absolutely right about tie rod orientation needing to point towards ISA for zero bump steer. The difference in length of the tie rod vs the swing arm will also have an effect on the linearity of the bump steer. You are right about the push/pull rod too, I think I was just getting confusing - I haven't really looked at this stuff since last year when I was working on the geometry!

By interconnected suspension are you talking about his longitudinal z bars? They are an interesting concept, although again I'm not convinced of it's benefits in FSAE due to the limited suspension travel and generally smooth tracks. His designs also don't take into account the need to package the bars around underfloor aero and carbon fibre monocoques - although I'm sure he still believed both are unnecessary

Yeah he certainly knows his stuff. I must admit CM isn't really taught in the same way anymore as far as I can tell - I didn't really understand the term when I first read his posts. You are right though, the automotive industry seems to have gone towards instant centres and roll centres, which is fine as long as you realise what they actually signify - sadly very few people seem to. A perfect example of this is the design spec sheet you have to fill in as part of the competition, which includes 'roll centre migration'. Really you are only interested in the angle from contact patch to roll centre (effectively the n-line angles for left and right tyres), so why it is specified in terms of lateral and vertical displacement, as if minimising migration is the target, is a nonsense.

You are right though, I suppose the ISA location is constant relative to the wheel centre for a given wheel travel - so a lookup table could still work with tyre contact patch deflection taken into account afterwards. It wouldn't work for suspension damage though! I'd suggest there are two ways to calculate it in real time - geometric and force based. Creating planes defined by the wishbones and calculating the line through which they intersect would surely take minimal processing power. Alternatively you could construct a suspension link matrix for the 6 links that constrain the upright (direction vectors and outboard positions), and invert to calculate the loads in each link for upright equilibrium given a contact patch force/moment input. Those loads could then be separated into their vector components and summed to find the overall jacking force applied to the body. You would have to continuously compute the link matrix and its inverse though which I would imagine would be significantly more computationally expensive.

I understand the force based method is actually more accurate, as the toe link (and possibly push/pull rod?) can also provide some jacking forces. I haven't really got my head around that though.

This is certainly an interesting topic for which there is a lot of misinformation around - you've picked out one of very few resources that actually described anti-geometry accurately, although I'm not sure I agree with some of Z's other views I would love to hear Scawen's input on it.

From my understanding:

You are correct in assuming the suspension upright travel can be described as a rotation about an instantaneous axis.

If you only had a single wishbone, the instant axis would be a line going through the two connecting points on the chassis. This is hopefully obvious - if you try to move the upright, it is constrained to the chassis in those two points, and so rotated about them. Having two wishbones however means your instant axis moves with suspension travel (hence 'instantaneous'). You can consider the upper wishbone and lower wishbone as two separate planes in 3d space, and the line defined by the intersection of those two planes is the instant axis for that corner at the specific wheel position.

Forces at the contact patch then act on the chassis in the direction of a vector from contact patch to the instant axis. i.e. if the instant axis is above ground at the point where it is in line with the wheel axle, you have an anti roll jacking effect (i.e. if the front view instant centre is above ground). Similarly if the instant axis is above ground at the point where it is directing in front of the contact patch, you have anti dive or anti squat (jacking), depending on if the wheel is braked/driven. (the point is also called the side view instant centre).

As such it's not actually that difficult to model - you could create look up tables for the front and side view instant centre positions with wheel travel, and use cosines to apply the appropriate jacking force as a proportion of the contact patch forces. I would imagine this is already implemented considering how high the instant centres look on BF1 particularly, but that is a question for Scawen.

Out of interest, are you a part of the FSAE competition?

Quote from Scawen :

- Does anyone have any facts about the limits in real cars when front wheel drive is involved?

from memory most FWD hatchbacks/SUVs had around 33 degrees (with a bit of ackermann.. maybe 31-36 deg)

less on topic formula student cars have probably 25-40 if you fancy making a new one of those with all the aero on

Name: George Baldwin
Username: jinja jorj
Number (01 - 999): 12

Personally I would over do it (although not when it can ruin the race for someone else obviously), but I find it important to know where the limits are, and know the consequences. This way you know that during the real races you won't ever out brake yourself when you try to out brake someone else, or if you get push into a worse position where the proper race line isn't possible you will be able to respond well to it or even put it to your advantage. Perhaps this is somewhat just personal preference though.
Otherwise just practice practice practice

Quote from Krieger776 :

Now i had been mixing some sets in one that i got from Setupgrid, so what else i can do to get even faster times?

I need to get provided with stuff in order to get faster times, monsterrocks did a thread but that's only for FF cars, so i need tips for RWD ones, waiting for responses, also replay included.

If you're still wanting help, I'll give it a go, although I haven't played for a while so am quite rusty

The attached replay is my fastest online lap in a race setup, the lap starting just after the 10 minute mark (excuse the excitement during/after )

Hopefully it'll give you something to compare your driving to, along with the hotlaps on lfsw.. (driving a race set is slightly different to HL set so might make it easier to compare, as well as hopefully illustrating what I say below..)

now from your replay there I'd say:

Last corner before your lap starts, get closer to the right edge of track before the corner/your turn in and probably brake a little less. Also don't get tyres dirty on the exit, only use the kerb unless you're on a fast lap as it wrecks your first turn on the next lap.

Turn 1 you lose time for using the H shifter and clutch as you have to brake earlier, but skipping over that, try to change down to 2nd sort of as you turn in a bit and as early as possible without over revving. If you do this and come off the brakes quicker/don't trail brake, it should give you a little slide (not tyre squealing so much but being on the point of oversteering while still having grip). Otherwise you can use the handbrake to give the same effect.. The little slide gives you a better corner entry, as in your lap you understeer slightly/have to turn in quite hard which loses you speed

You can cut the middle kerb of the chicane too if you like, but that won't affect it much.

For the corner at the end of the straight I would use more of the kerb on the left before entry, and less trail braking to get the same sort of slide as turn 1 entry. For this sort of thing experiment with how quickly you come off the brakes and how much steering you do as you come off the brakes to find the best entry for your driving style

For the last corner I would brake less/carry more speed in, then be slightly later on the accelerator..

Other than that its a decent lap, mainly slower because of braking earlier to allow time for H shifter gear changes

On a side note I like to have a very oversteery set up, and drive it right on the edge of sliding.. Sometimes its the fastest way around the corner, and sometimes its just personal preference - so it might not work for you.. there are other ways of doing it so dont be put off if my way doesnt work for you

Chucked on some pictures from lfsw HL analyser to help illustrate the points, think that'll be easier than trying to describe where i mean

I'll have another look at your replay tomorrow and see if theres anything else other than what i mentioned in the last response

And thats a fair point CarlLefrancois, basically just means that you cant just jump in and drive the wr lap.. It takes practice and experimentation to find how the car feels and reacts in different situations.

Hope I've managed to help in some way anyway monsterrocks.. You can also try asking people online to help out/watch your driving, or even just watch them - see what they do different to you and try it.. Even if it works out slower for you, it still gives you the experience to know how the car will react if you are forced to use a similar racing line by other cars in a race

Quote from monsterrocks :

here are the attachments guys if someone could help explain to me in detail what i'm doing thats slightly different.

Always quite difficult when it gets down to this level.. I'd say the main points:

Not very smooth on starting curve, you keep wheel straight then turn quite hard, want a much smoother line.. thats only costing you like 0.01-.02 though

You also turn into the inside kerb of the chicane a bit too much, losing you speed out of chicane and hence are slightly slower all down the straight. I'm obviously not the person to come to for help here though, as thats also the main difference between my lap vs WR

You lose a bit more time at the corner at the end of the straight as you don't quite touch the apex.. want to just nudge that one..

2nd last corner need to straighten up wheel as you come off brakes to stop sliding, as it loses you a lot of speed.. you also are slightly wide of the apex
(Maybe what you did on lap 2 works, but think you could probably carry in more speed with a narrower entry, personal preference though)

Also could be minutely closer to last apex, although less of an issue. try to keep to the right on the final stretch to the finish line a bit more though

Another difference (not necessarily a bad thing in this case) is you carry more speed into 2nd corner in sc2, running slightly wider on exit so lose a bit of speed into sc3.. seemed to gain you time though

Hope some of that vaguely helped

As others have already said, don't bother with the ai drivers, you wont learn a lot.. try and get online and just race behind the others. It's also good to watch the other drivers from their incar view (assuming thats the view you drive from). As long as you're a safe and polite driver there are plenty of people out there willing to help!

Dark's setup is a good set too, it's the one I learnt in, with his help

The xrg is a tricky car though, especially around bl1.. Personally I found it a lot easier after spending time in the xfg, but thats just me. Also, trying to drive like the top hotlap laps probably isn't as good as watching and getting help online tbh, as there will be a lot of differences between your driving and theirs, which can be difficult to spot yourself and can get you into bad habits (I always oversteered ridiculously trying to copy fast drivers turn ins, when really the trick is to sit on the edge of where the grip is, so not sliding but not understeering, and steer a lot with the throttle).

At the end of the day it just takes practice - soon enough you'll be up there in the thick of it I'm sure.. My advice is just get online, look at others driving and even ask if they're willing to spectate you and help out a bit..

And you're welcome to give my setup a try, its on setupgrid I'm pretty sure.. although you may find you prefer dark's - I do like having a tail happy car

Quote from monsterrocks :

thx for the help Jinja Jorj the car seems to naturally understeer wide out of T1 i think its setup thing because as you said its made for eft hand side drivers and i'm on the right which is what i've always had in the back of my mind but wasn't sure how much of a difference it made but i guessit would when you sit on the left and the setup is based aruond that + its setup to use for a mouse and i'm using a G27 steering wheel dunno if it makes much difference though, but every little bit helps i'll try your set over the next 2 days and see how i go

No problem mate, hope it helps I use G25 and right side drive so hopefully my set will work for you too i do know what you mean about his set feeling quite understeery out of T1 good luck!

Quote from Rotaryman :

Ok, so I'm gonna use the thread to ask how can I rip off about 2 seconds.
Yeah, I know, you all gonna tell me that I need practice, but I want you to tell me precisely what I'm doing wrong, cause I hardly have an idea (as for example bad first turn entry, as well as poor turn after the long straight), I know I could go much fuster, both in terms of speed and laptime, but when I try to go a few kmph faster, I simply end up somewhere far away from the track, usually on sand. Yeah, I love beaches and sunlight, but not necessarily when racing.

My fastest time ever was 1,35,03. On the spr I made slightly worse, on 6th lap.

From the 6th lap I'd say the main things are:

Turn 1 braking - you braked very early, so turned in a bit early and had to dab throttle before apex.. If you're going for top times then you would also want to brake starting on the kerb on the left and trailing towards the centre of the track by the turn in point, but thats not so important just yet!
Aim to brake just slightly before the start of the kerb, then experiment with down changes and steering until you can happily get around the corner.. I hate to say but that part is mainly practice.. sorry!

Chicane - try to straight line the chicane slightly more, on lap 6 you just missed the central apex, although you hit the first and last kerbs right

Corner at the end of the straight - very good, theres lots of lines you can take there, all of them get pretty similar times.. you're on lap 6 was pretty close to being spot on tbh

2nd corner in sector 2 - What you did worked well, but you continued turning to the right for too long.. You can push wider on the exit and make the most of the inside kerb for the left hander
Another thing you can try is to use the kerb on the left on the entrance to this corner, which takes a bit of practice but gives a wider entry so a faster line through

2nd last corner - Good, but you braked a bit early/too much. Try to carry more speed into the corner, but be much later getting on the throttle
You can also try using more of the kerb on the left on entry when you get more confident with the rest

Last corner - again too much braking, try to really carry as much speed through here as possible. try experimenting with just a dab on the brakes (you may need to do it slightly earlier to not go wide). You can also push out wider on the exit.. aim to just mount the exit kerb with your right wheels just after the kerb width increases

Hope some of that helps, and of course you're welcome to give my set up a try, although as said previously its made for right side driving and is very tail happy..

Quote from monsterrocks :

heres a replay so you can all have a look and give me some tips guys

I havent played in a while so i might not be much help, but a few things i think could be improved on the first lap in that replay:
T1 braking, bit of a gap between coming off gas and getting on brake, think you could potentially do that a bit quicker (not a major issue really though)
T1 exit a bit wide i would say.. try not to go onto the blue/white kerb on exit
End of straight corner maybe a little too much sliding? could just be the setup though
2nd last corner, you turn in hard as you come off the brakes which really destablises the car so slide too much, possibly try to control it by straightening the steering very briefly as you release the brake?

Also you drive on the right side of the car (like me ) so people like nilexs setups may not be quite so good as they've been made for left side drivers

The fact that you're using a race setup rather than qually gears will cost you little on the wr times too

Its a very good lap though, keep it up and im sure you'll keep improving! Try to experiment with different lines etc as well as looking over the HL analyser..

Oh and you're welcome to give my setup a try, its on setupgrid.. just be warned its pretty tail happy

well done both btw, nice laps If im honest im suprised it took you so long

At some point i will try and get this back though, if i can sort out that damn sc1!