47 replies to this topic

[Lukin]

Hi All,

I am after some advice on a decent testing program for an open wheeler. It’s an Oz spec Formula Ford so aero isn’t a consideration. I am really after some good hints and tips before we take the track (which is planned, hopefully, in the next few weeks). Also, the testing is more for setup than developments.

I haven’t modelled up anything yet with Susprog3D or anything yet; I’d rather get half a grasp of setup changes before I go down that road. I have a few references for cause and effect which can be used for race day, but given all the races are on the one track I would like to establish a good baseline setup that can be altered as conditions change.

From two books I have I got the following tips for anti-roll bar and damper tuning.

Anti-Roll Bar (Van Valkenburgh, P 129-130)
The best practise is probably to develop front tyre cornering performance first (since the car should be understeering), and as it becomes better, to keep increasing the front anti-roll bar rate as necessary to avoid oversteer. When no more front cornering power is available or the front roll rate is so great that it lifts the inside front tyre off the ground, then it is time to work on increasing the rear tyres capabilities. The rear anti-roll bar rate may be increased to create oversteer, as a rear tyre limiting condition is overcome.

Tyre test procedure is simply to record average laptime or lateral acceleration for each configuration change.

Dampers (Staniforth, P240-241)
Bump Control Adjustment
1) Set all four dampers at minimum on both bump and rebound.
2) Drive a few laps to get the feel of the car. Disregard body lean or roll and concentrate solely on how the car feels over bumps.
3) Increase the bump adjuster by three clicks (note – damper setting dependant I guess) on all three dampers. Drive a few laps. Again increase bump settings a further three clicks. Keep repeating until things start to feel hard and jolty over bumps.
4) Back off (reduce) bump adjustment by two clicks. Note: it is very unlikely that both front and rear will match. Get one end right and continue the same at the other until they are similar. Make a note of these figures in writing.

Rebound Control Adjustment
1) Leave the newly chosen bump setting untouched. Rebound to full soft noting particularly how the car rolls entering a corner.
2) Increase rebound by three sweeps (3/4 of turn) in adjustor slot. Drive it again noting how it enters a corner. You are looking for smoothness without a drastic attitude change or excessive sudden roll.
3) Increase stiffness three more sweeps if necessary until smoothness is achieved. Too much will be indicated as above, so back off two sweeps at the appropriate end of the car.

Does anyone have anything to add (or detract) from Van Valkenburgh or Staniforth? Or any comments and tips really. They would be much appreciated.

Also, if I could get tyre data and determine the optimum camber angle, could I use the suspension settings to find the roll angle at the most common lateral g for the track, which could give the greatest cornering performance?

Cheers!

[Greg Locock]

Optimum camber might be a bit tricky. Look at Milliken fig 2.30, you've got about 10-15% on lateral force from 0->-5 degrees, most of which you lose again by -10 degrees.

The implication from the text (and this seems intuitively right) is that this is a genuine increase in 'diameter' of the friction circle, but it is possible that you'll also be affecting the optimum steer angle, that is,as you generate more lateral force via camber, you may not be able to generate as much via steer.

Anyway, yes, I would have thought you could use the body roll to figure out the best camber setting for a given curve. I didn't think that was how people set the camber (I thought they looked at the change in tire temp across the tread).

[red300zx99]

Tire temperature across the tread seems to work well. Better yet measure the circumfrence of the tire across the tread at the operating temperature, but be sure to remove any gunk that has stuck to the tire.

[Lukin]

Originally posted by Greg Locock
I didn't think that was how people set the camber (I thought they looked at the change in tire temp across the tread).

I've never set (or tried to determine) camber so it was just a first guess. We have a pyrometer so I will use it as much as I can to ensure the temperature gradient isnt too severe.

Any ideas (hints!) on testing procedures?

[dc21]

It all depends if you have a baseline setup or not. Without a baseline setup you have to work from instinct. With a baseline it's just a case of refining what you already have. Only make one change at a time and get as much feedback as possible. If you have data acquisition ensure you correlate driver feedback with the data, this will help you identify handling problems in the future. Don't rely on books too much (I would argue against using them at all). People seem to look for answers in them, instead of thinking logically about what the car is doing at a given point on the circuit.

Your initial priority should be getting tyre pressures/temps right. If these aren't working you'll go miles off track on setup. Pick the most important corners and work on a good setup for those. Remember that gear ratios have an affect on car handling too, lots of people seem to forget this. Keep records of everything, I prefer a book to setup sheets.

Ensure the driver knows how to drive, the driver can create more handling problems than discrepencies in setup. If the driver is useless the stopwatch is king. As the driver improves the stopwatch becomes less useful in making changes.

Just a few pointers from my own experience,

Dave

[McGuire]

Originally posted by Lukin
I have a few references for cause and effect which can be used for race day, but given all the races are on the one track I would like to establish a good baseline setup that can be altered as conditions change.

What is the starting point? Do you already have some baseline, or are you proceeding completely from scratch?

[Lukin]

We do have a baseline from last season (the car was used by other people from the same team), so I guess it does make those suggestions a little redundant.

[dc21]

In that case, especially with a FFord, it's all about bum in seat time and small changes for the conditions of the day and the ability of the driver.

Dave

[Greg Locock]

Are you saying that a formal exploration of the design space is a waste of time?

[dc21]

No, I'm saying that people spend far too much time theorizing (is that a word?) and not enough time doing. At FFord level, you will find much more time giving the driver seat time, than you will performing detailed theoretical analysis. You seem to be looking at this from a design point of view, as opposed to the end user. I know nothing about designing cars, but I do know how to setup race cars. If you feel a detailed suspension analysis is going to help, do it. I'll spend my time at the circuit gathering real world data.

Of course, once you start working with competant drivers, and the level of competition is close enough, you'll start noticing minute differences and therefore gain more useful insight performing analsyes. Since I'm always willing to learn, what sort of useful information (that translates to the track) would you learn by performing suspension geometry analysis, remembering that little to no tyre data is available (getting tyres to work being the main aim in all this)? This is a genuine question, not a rhetorical one.

Dave

[Greg Locock]

Well one big difference is I can do suspension analysis 24/7, you can only test drive cars when you're at the track. So even though you learn a lot more per minute at the track, there's no harm in exploring interactions theoretically. I know the V8 supercars in Australia explore interactions on rig tests - expensive data, but given their limitations on track testing, they don't want to be exploring shock tunes for each spring and sta bar combination while they are at the track

I'm a bit puzzled about your comment on the lack of tire data. 6 strain gauge rosettes and you have an instrumented corner of the car. Along with accelerometers and string pots it is now capable of generating tyre data under realistic conditions - something no Flattrac machine can do (especially given that you aren't really interested in all 6 'forces'). Admittedly we do this with very expensive wheel force transducers, but with a bit of thought you can do the job with strain gauges.

Oh, I'm not knocking track setup - it is essential. The computer models we have are good for identifying /trends/, not settings.

[McGuire]

Semi-technical testing program tip: after the very first session, when you lean into the cockpit for your first debrief, take careful note of what the driver is fussing or fiddling with or is otherwise distracted by while you are trying to talk to him: shifter, brake pedal action or bias adjuster, whatever seems to be annoying or troubling him inside the car. Make fixing that item Job One and you will immediately become a Wizard as far as he is concerned.

The good news here is that with this one simple and easy change, you may very well produce the single greatest improvement in lap times you will see this season. However, the bad news here is that with this one simple and easy change, you may very well produce the single greatest improvement in lap times you will see this season.

That's race engineering: you start at the wide, easy end and work your way to the narrow, difficult end. The closer you get to the narrow end the more incremental the improvements will tend to be. So the more clever you become as the year goes on, the less effective you may appear. The trick is in knowing where you and your team are on the progress curve, and directing the effort to the right places. This can be annoying for engineeers, as they would rather be working on the areas they are most intrigued in than in the best potential areas for improvement.

Another tip: photocopy a bunch of track maps and use a copy in every debrief. Pick the most important corners and divide each into three parts: entry, middle and exit, and make the driver talk you through each segment. You may find the driver is describing oversteer as understeer and vice versa, depending where he is in the corner. Saves a lot of confusion and wasted effort.

[dc21]

Some very good points there McGuire, especially concerning drivers descriptions of over/understeer. You also have to be aware that a driver will often feel what they expect to feel, and are often the real cause of any handling problem you may have. The driver can make the car do some very strange things.

Regarding my comment on tyre data, you have to remember the level you're racing at. Most FFord teams at club level will have no data acquistion. At most they'll have a basic rev/speed/temperature logger. When buying a new set of tyres the only information you get given is max inflation pressure, and maybe recommended running pressures. If you're really lucky they'll tell you approximate running temps to aim for. You have no other information, nor the means to obtain it. Given this lack of information, how do the analyses performed, translate to useful on-track data?

Dave

[Lukin]

We have linear pots, lateral/long g, steering angle, wheel speed, rpm, lambda, temps, pressures (I think thats all of them). I have data (slip, COF, SAT) from Avon for the FF2000 wheels from the US, and am in the process of finding out if there is any for the ones we use as the FF2000 ones are slightly wider. A lot of tools are available to me, so I would like to get familiar with them for the future. (I know you weren't aware of that so I thought I should clarify)

Speaking to the team manager last month, he thinks that a lot of time can be made from damper understanding and development.

[Lukin]

Originally posted by McGuire
Another tip: photocopy a bunch of track maps and use a copy in every debrief. Pick the most important corners and divide each into three parts: entry, middle and exit, and make the driver talk you through each segment. You may find the driver is describing oversteer as understeer and vice versa, depending where he is in the corner. Saves a lot of confusion and wasted effort.

Good tip. Cheers!

[Lukin]

Had the first round last weekend (didn't get any pre race testing).

Due to the nature of the race (warm down lap and all) the tyre temp gradient doesnt say a great deal. When we go testing before the next race I will get the driver to come in full tilt at the end of a flyer to check the gradient there.

The grad recorded was usually 10-12 deg C difference from the inside to the outside (inside was hotter of course). One think I did notice that there was little to no wear on the outside of the tyres. They were new and it looked like the outside of the tyre had barely made contact with the road. For the last race to fix some oversteer we reduced the rear bar a little, which made a dramatic difference to the tyre wear (it looked like the whole tyre was actually in contact with the road1!). The temp gradient didnt really change a great deal but, like I said, not putting too much faith in that at the moment.

Given there are very little kerbs and bumps on the track, I would like to stiffen the front and rear of the car (tuning the roll bars like Van Valkenburgh said in his book) to increase the cornering performance. The camber is currently 2 deg on the rear, but Im thinking I would have to drop the camber to maintain the contact patch under lateral g.

I dont have any tyre data (to find out optimum camber angles), but does this seem like a bad thing to do?

[bobdar]

Lukin: You haven't mention what kind of chassis or tires you are using, but here are some general suggestions:

"Due to the nature of the race (warm down lap and all) the tyre temp gradient doesnt say a great deal."
If you have access to one, a skid pad is a much better place to get the camber and tire pressure baselines; you can accomplish more in a couple of hours on a skid pad than in an entire race weekend. I like to use a temperature probe rather than a surface pyrometer; the tire's surface cools down too quickly.

"For the last race to fix some oversteer we reduced the rear bar a little, which made a dramatic difference to the tyre wear (it looked like the whole tyre was actually in contact with the road1!)."
It sounds as if you may be using excessive roll to mask bad camber settings. See below.

"Given there are very little kerbs and bumps on the track, I would like to stiffen the front and rear of the car (tuning the roll bars like Van Valkenburgh said in his book) to increase the cornering performance. The camber is currently 2 deg on the rear, but Im thinking I would have to drop the camber to maintain the contact patch under lateral g."
Have you checked the wheel rates yet? I get the impression that you are trying to stiffen the car with the roll bars, instead of stiffening the car with stiffer springs. The general rule of thumb is that the wheel rates should be approximately the same value as the respective corner weights, and that usually requires fairly high spring rates. The ARB's are for fine tuning, not for stiffening the car. I would work with the ARB's in a neutral position and fiddle with the spring rates until you are happy with the overall balance of the car. If you find one ARB wants to be "full hard", it's likely that you need more spring on that end of the car; and vice versa. Then, work with tire temps to establish a good baseline for camber and pressures. Ultimately, you want a car that is neutral, has four tires in maximum contact patch, and still has the ARB's in mid (neutral) position.

[Lukin]

You haven't mention what kind of chassis or tires you are using
Up the top of this thread its mentioned. It's a Formula Ford Oz spec (no wings, 1600 cc) with Avon Racing tyres.

It sounds as if you may be using excessive roll to mask bad camber settings
That might of been the case. I didn’t set the camber (this was my first proper round) and it was just an observation I made after the rear roll settings were changed. It prompted me to think about reducing the rear camber. I’d like to reduce the roll which, as you said, will require reducing the rear camber, which I plan on doing.

If you have access to one, a skid pad is a much better place to get the camber and tire pressure baselines; you can accomplish more in a couple of hours on a skid pad than in an entire race weekend. I like to use a temperature probe rather than a surface pyrometer; the tire's surface cools down too quickly.
That what I’m hoping to do as it takes out other factors (steering, traffic) and concentrates on exactly what I want. I am trying to organise one. Given I volunteer and I don’t know a great deal, it takes a little persuasion to get something done!

The general rule of thumb is that the wheel rates should be approximately the same value as the respective corner weights, and that usually requires fairly high spring rates.
Could you expand on that? Our corner weights are around 109 and 142 kg on front and rear (each wheel). Is that the corner weight your alluding to? What spring rate do I am for? 109 N/mm or is it in imperial (242 lb/in)? Sorry, I just don’t completely follow.

The ARB's are for fine tuning, not for stiffening the car. I would work with the ARB's in a neutral position and fiddle with the spring rates until you are happy with the overall balance of the car. If you find one ARB wants to be "full hard", it's likely that you need more spring on that end of the car; and vice versa Ultimately, you want a car that is neutral, has four tires in maximum contact patch, and still has the ARB's in mid (neutral) position.
Thanks for that! At the moment the bars are barely on. I would like to increase them to mid range, but being able to utilise the springs to a better degree will help no end. For the rear, is it better to have high spring rates with a lower roll bar to optimise traction without significantly increasing the roll angle during cornering?

Cheers for the response!

[shaun979]

Originally posted by red300zx99
Tire temperature across the tread seems to work well. Better yet measure the circumfrence of the tire across the tread at the operating temperature, but be sure to remove any gunk that has stuck to the tire.

The following was a criticism of Fred Puhn's book on handling. I am curious as to how true the statement about modern tires being designed to run hotter on the inside is.

"The book includes between zero and little advice on modern suspension tuning techniques. There's no mention of corner-balancing and cross-weighting in the book. The section on pyrometer use for diagnosing a car's handling is less than half a page long and includes a couple of flaws. One of them is suggesting that the "ideal" setting results in equal temperatures across the surface of the tire; modern directional tires are built to let the inside edge to more work, so the tire will run hotter towards the inside."

How does one tell which type of tire is designed to run hotter on the inner area, and on such tires (if they really do exist) how much higher percentage wise should we expect the inner area to get?

[Lukin]

Originally posted by shaun979
How does one tell which type of tire is designed to run hotter on the inner area, and on such tires (if they really do exist) how much higher percentage wise should we expect the inner area to get?

I would think every tyre used in racing would be designed that way. With the exception of active suspension cars, I cant see how any tyre on a halfway decent car would have an identical temperature range across the tyre. The only way I could think you could get that is by equating the work the outside of the tyre does during cornering to the work the inside does on the straights (assuming they start with negative camber). In any case, I cant see how that is a way of tuning the car.

[shaun979]

So how much higher in temp should the inner areas be? I don't recall Paul Van Valkenburgh writing about this (inner portion temps being higher) in his book. It has been a while since I read it though.

[Lukin]

From a corrospondance with Fat Boy:

As far as temps go, they are important, but as a reference, not as a target to shoot for. The target is a quick car. When you get a quick car take note of the tire temp spread. The inside will always be hotter. It really doesn't matter if it's a 20 or 60 degree (F) spread in temps. I've had
good cars in both cases. Bias ply tires tend to run less of a spread and radials tend to run more of a spread, but there is no perfect tire temp distribution.

Valkenburgh says very little about it. Im not sure either.

[red300zx99]

I've never heard of the inner being hotter as a good thing. Even tire temps and/or tire wear across the tread is what to aim for. Mainly adjusted through camber and tire pressure settings. And you can also compare avg temps front to rear, left and right. The fast cars have these sorted out.

[Dmitriy_Guller]

Originally posted by red300zx99
I've never heard of the inner being hotter as a good thing. Even tire temps and/or tire wear across the tread is what to aim for. Mainly adjusted through camber and tire pressure settings. And you can also compare avg temps front to rear, left and right. The fast cars have these sorted out.

The reason why even tire temps is a bad idea is that with negative camber, the car rides on the inner edges of the tire on the straights. To equalize the temperatures, the car has to ride on the outside edges in the corner, which is not a good thing, as you want to utilize the entire tread width in the corner (where the grip is most needed.) Therefore, the fastest car will ride on full patch in the corners, and insides on the straights, and the inside edge would necesserily have to be hotter.

[BRIAN GLOVER]

Differential, differential, differential. Start with an open diff and do all your set ups. Diff set ups vary with downforce. Fine tune suspension settings with the diff. Start introducing in and out slip for the turn that will give you the most gain. F1 guys spend 3 days setting up the diff.
Next to tires, the diff is the most important thing. Also, about tire temp and camber.
Which part of the track will give you the most gain? Post a picture of the track and the seeds thru the turns and brake zones. Post a read out if possible.
Is there a long straight? Tire temperatures are not important if there are no high G corners and high cambers may give lower rolling resistance. If there are a series of high G turns and you can gain significant 10ths, then full contact patch becomes more important. A pyrometer wont tell you anything, especially if you make it all the way back to the pits long after the high G turns and the temps have normalized.. Determine which corner will give you the most gain and set up for that by simulating it on a skid pad both left and right..
If you cant find a skid pad, it is good to observe the tire in the corner and watch the wear in real time. The back, with the mirrors. Also stop immediately after the corner in question on the track if possible and feel the tire with your hand before the heat spreads. Your hand is the most accurate instrument. Set for the highest G and verify visually and by hand. It is possible to have too much tire. Train a few guys to feel temps by hand, stop after that turn and let them run to the car to feel the tires. Verify with a gauge if you want.

Originally posted by Lukin
We do have a baseline from last season (the car was used by other people from the same team), so I guess it does make those suggestions a little redundant.

[Lukin]

We pretty much dont have any downforce (apart from a small amount of underbody) and as far as I know, the diff isnt tuneable, but I will check that.


The red is brake, the blue is throttle from 0 to 85%. Ignore the entry into turn 3 where it looks like the brake is on then off.

[BRIAN GLOVER]

Interesting. Looks nice. Is that MPH? What's the other number? How long is the track? Is it flat and smooth? Who is the fastest driver? Have you talked to him? Have you followed him? Which part do you think you could improve by the most? How many laps permitted on the tires? can you change compounds.?Is there website for the rules?
Off the top of my head, the 3 right handers is the key. 5, 6 and 1 in order of importance. Left Tires may go off soon so it mustn't push. Compound choice is important. The biggest gain will come from exiting 5 before the long straigtht and the diff is important in 6 and 1 if this is MPH.
The fastest way to see what is going on for an initial dry set up is to see what the car does in the wet.

Originally posted by Lukin
We pretty much dont have any downforce (apart from a small amount of underbody) and as far as I know, the diff isnt tuneable, but I will check that.


The red is brake, the blue is throttle from 0 to 85%. Ignore the entry into turn 3 where it looks like the brake is on then off.

[Lukin]

Nah it's km/h. It is only Formula Ford. The top number is speed (max straight or min corner) and the bottom one is the revs at that speed. www.formulaford.com.au has all the details. There is a single compound, they are semi-slick Avon's that last 6 rounds to lower costs. Turn 5 is the important corner and it's a downhill straight after and a good passing oppurtunity, we made up around half a second last year just through changing the braking into that corner. The track is smooth, and there is no advantage in riding the kerbs. The only concern is the kerbs on the outside of the last corner, which can be a problem for anyone being too aggresive. Because it's only a state series, there is no practice at the round. Qualify, then three races. We will be testing on the track and hopefully on the skid pan (I will be pushing for this). I have only spoken to the quickest driver in passing, though he works out of the same garage. Will get a better chance at the next round as everything wont be as rushed.

[BRIAN GLOVER]

100hp, Jees. Nevermind.
Is there someway to cheat? Anyway, I wish you luck and lots of fun. Keep us posted and tell us what you have learned.
I guess the cars are close in performance so driver skills play the biggest role. Pay attention to what the fastest guys are doing and find a way to do it better.

I'm going to try and stay awake for the GP at 1:30am.

Originally posted by Lukin
Nah it's km/h. It is only Formula Ford. The top number is speed (max straight or min corner) and the bottom one is the revs at that speed. www.formulaford.com.au has all the details. There is a single compound, they are semi-slick Avon's that last 6 rounds to lower costs. Turn 5 is the important corner and it's a downhill straight after and a good passing oppurtunity, we made up around half a second last year just through changing the braking into that corner. The track is smooth, and there is no advantage in riding the kerbs. The only concern is the kerbs on the outside of the last corner, which can be a problem for anyone being too aggresive. Because it's only a state series, there is no practice at the round. Qualify, then three races. We will be testing on the track and hopefully on the skid pan (I will be pushing for this). I have only spoken to the quickest driver in passing, though he works out of the same garage. Will get a better chance at the next round as everything wont be as rushed.

[Lukin]

Originally posted by BRIAN GLOVER
100hp, Jees. Nevermind.

120 hbp thanks. Cmon!

Is there someway to cheat? Anyway, I wish you luck and lots of fun. Keep us posted and tell us what you have learned.
I guess the cars are close in performance so driver skills play the biggest role. Pay attention to what the fastest guys are doing and find a way to do it better.

I've found that about the driving. With MoTeC you can find best complete laps (ie one full lap but starting at any point on the track, not the start/finish line) and in one race the drivers best complete lap was quicker than the winners fastest lap. That said, conditions for said race were not the best.

I guess it becomes my role to give continual feedback on the driving style and try and tailor the car to make consistent driving easier.

It's already been a blast. Had a mechanic go through and show me how to adjust corner weights, check all the settings and make changes as required.

[BRIAN GLOVER]

Great GP. Slicks at last. I hope Senna's pole record stands. I managed to stay awake. 3:45 AM now. Looks like a great season ahead. First time I havent fallen asleep during a GP for ages.

So the engine builder is king in your series. I'd rev the **** out of it and gear it accordingly. Can you change the diff ratio? Gear it for max speed down the straight. Iwould forfit all handeling and dial out out all stability. The highest tire pressure possible and the most negative camber and little caster. It will be a bitch to drive for the first laps as the contact patch grows. Driver must be ultra sensitive. Speed bleed off looks like the biggest problem in the 3 right turns with that kind of power. Id experiment with a corner weight stagger and zero roll control. I would go for the smallest contact patch and control steer by jacking the right front or back and the highest spring rates. To increase contact patch, I would leave tire pressure high and reduce camber if required. The straight and the 3 right turns is all I would consider. Good luck.

Originally posted by Lukin

120 hbp thanks. Cmon!



I've found that about the driving. With MoTeC you can find best complete laps (ie one full lap but starting at any point on the track, not the start/finish line) and in one race the drivers best complete lap was quicker than the winners fastest lap. That said, conditions for said race were not the best.

I guess it becomes my role to give continual feedback on the driving style and try and tailor the car to make consistent driving easier.

It's already been a blast. Had a mechanic go through and show me how to adjust corner weights, check all the settings and make changes as required.

[BRIAN GLOVER]

This may cause lock up under straight line braking if you have jacked the right front to control oversteer, which I expect you will. But you will be turning right which allows late braking deep into the 3 turns. Turn 6 may be tricky. You suggest that people come off here?
Mario Andretti and Collin Chapman did wonders with this type of out of the box thinking.

Originally posted by BRIAN GLOVER
Id experiment with a corner weight stagger and zero roll control.
[/B]

[dc21]

Amidst all this pontificating, what does the driver say?

In the dry you tend to be full stiff on the rear ARB, tuning the front ARB for balance. 2.0 degrees rear camber sounds a lot, and would account for the oversteer. Try coming down to 1 degree on the rear. Remember, ARB's only really come into affect when the car is loaded up through a corner. Use dampers, rake and toe to tune turn-in.

Does the driver left foot brake? Going up the box should be a clutchless shift, while downshifts can be clutchless with practise. This will allow the driver to left foot brake all the time, and minimise shift time.

Dave

[bobdar]

Lukin asked for more information re. the relationship between spring rates and wheel rates. To write this relationship, you need to know the motion ratio for the suspension configuration, which varies from car to car and from front to rear on most cars. Motion ratio is the change in wheel position divided by the change in spring length. Since the motion ratio is not constant through the entire range of travel, it is usually measured in the vicinity of the static (weighted) ride height. For example, if you set the suspension at normal ride height, move the wheel 1.5" into bump and measure the spring length (or the shock length if the springs are off the car). Then move the wheel 1.5" into droop and measure the new spring length. The motion ratio is the delta wheel position (3" here) divided by the delta spring length.

WR = SR / MR**2

Wheel rate = spring rate divided by the square of the motion ratio. The concept of making wheel rates approximate the corner weight results in a very, very stiff car--fast, but not for the novice driver. Nevertheless, once you find a good balance between front-to-rear wheel rates, you can increase spring rates gradually and maintain that balance by keeping the wheel rates in proportion.

[BRIAN GLOVER]

I've been working on my Hot Rod for next weeks auction, but I have been thinking about this thread. Testing program tips is the name of this thread. You must ask yourself what your objective is. Do you want to be like Michael Schumacher or Jean Alesi? IE: Do you want to win the race or go for a Sunday afternoon drive in a car that handles really well and drive it without applying driver techniques suited for this track and this track only. Do you want to practice the "Art of Racing' or have fun. Racing is a serious business and like in Sun Tzu's, 'The Art of War', you may have to drive in a less than exemplary fashion. IE: Like Schumacher does.
I understand that this is the only track that you race on? If this is the case, there is one place to pass and that is the long straight as far as I can tell.. There are 3 corners that require a similar set up. 5,6 and 1.
Assuming you want to win the race at this track, we are not setting up for poll or even the fastest race lap, we are setting up to win.

Each lap you should pass a car down the straight and prevent anybody passing you for the rest of the lap. That is the plan. Design for this.

So first, you concentrate on the straight. It appears that there is not much difference between the performance of the cars so you have to get far out of the accepted envelope to win.
Are the engines sealed? Are the revs limited? Anyway, the engine builder must take meticulous care to build this engine. Gear ratio and axle ratio must be chosen for reaching the max speed 4/5ths down the straight.
It is interesting to hear the engines of F1 engines on the straights. Ferrari reaches max rpm in 7th just before braking for turn one at Indy, while all others reach max rpm, long before that. In fact, this track is similar to Indy because you don't know whether to setp for the turns or the straight.


To set it up go fast down the straight is obviously going to cause problems for the rest of the track.
IE: Apart from gearing, high tire pressures, high neg. cambers and spring rates are required.
Remember, Jean Alesi could not drive Michael Schumacher's car after he left Ferrari. A special driver needs to drive this car. It will be set up asymmetrically and will be a bitch to drive. Youwill have odd corner weights to get you around the right handers.
The axle shafts must be as straight as possible( We don't want any HP robbing angles.),aircraft tape is used to get rid of any parasitic drag. Cover all gaps in the body. Flair the holes in the body around suspension parts etc.
The next thing to do is to see what the car will do in turns 6, 1 and 5 with this set up. You may have to reduce the cambers on the left and steer it around turn 3 by bump tow out on the right rear. Remember, all you are doing here is preventing anybody from passing you so handling is a secondry consideration. Most will be too scared to pass when they see the car going all over the road anyway.
Braking at the end of the straights will be an experience. You will have to transfer load to the left of the car because of the stagger.. IE: you will have to be in a slight turn. This is perfect, because you will have just passed another car at the end of the straight and you will be able to brake later and deeper. I understand that people come off at the end of the main straight.
Well, you are going to have to learn a new skill to get around there and learn how to use your left foot on the brake to compensate for the cars poor handling.
As has been suggested, tire temps are not going to tell you anything unless you test with real time pyrometers. The real time visual and the hand trick is the next best thing. Once you have passed all the cars, the handling will improve as the contact patch grows but the son's of bitches will still try and pass you. You will have an easier time staving the bastards off now. How many laps in the race?

Anyway, this is how I would win this race and I'll give the booing crowd the number one gesture

Originally posted by Lukin

120 hbp thanks. Cmon!



I've found that about the driving. With MoTeC you can find best complete laps (ie one full lap but starting at any point on the track, not the start/finish line) and in one race the drivers best complete lap was quicker than the winners fastest lap. That said, conditions for said race were not the best.

I guess it becomes my role to give continual feedback on the driving style and try and tailor the car to make consistent driving easier.

It's already been a blast. Had a mechanic go through and show me how to adjust corner weights, check all the settings and make changes as required.

[Lukin]

Originally posted by bobdar
Wheel rate = spring rate divided by the square of the motion ratio. The concept of making wheel rates approximate the corner weight results in a very, very stiff car--fast, but not for the novice driver. Nevertheless, once you find a good balance between front-to-rear wheel rates, you can increase spring rates gradually and maintain that balance by keeping the wheel rates in proportion.

I was more referring to the units as I do understand the whole wheel/spring rate relationship. Some people here talk in lb/in etc. Our Motion Ratio isnt constant like you say. But for corner weights of 109 and 142 kg do you mean a wheel rate of 109 N/mm?

[Supercar]

Originally posted by Lukin
I was more referring to the units...

I think bobdar is talking in lbs and in/lbs. That spring rate would make your natural frequencies about 3 Hz, which I heard is about twice what FFord usually runs. May be a little too stiff for your car, IMHO.

Since you are logging steering angle and speed, you can try several different cambers, on one end of the car at a time, and see how that affects your steering angle (under/oversteer) thought the turns. Make sure that your test driver is driving at the same speed and following the same path. That may tell you your optimal camber better than tire temperatures.

Looking at your track it should also help to run an asymmetrical camber. Less negative on the right side of the car.

Philip

[bobdar]

Being an older 'mercan, I am talking (thinking?) lbs and inches, but the motion ratio has no units; so the wheel rate units would be the same as your spring rate units (force/distance)--lbs./in or kg/in. Why would springs be rated in N/mm? Still curious as to what brand of chassis you have; there would be a big difference between a modern VD and a 25 year old Lola. I have a '70 Lola vintage FF and the wheel rates are about .5 X corner weight (would probably tear it apart at WR = CW).

[Lukin]

Originally posted by dc21
Amidst all this pontificating, what does the driver say?

In the dry you tend to be full stiff on the rear ARB, tuning the front ARB for balance. 2.0 degrees rear camber sounds a lot, and would account for the oversteer. Try coming down to 1 degree on the rear. Remember, ARB's only really come into affect when the car is loaded up through a corner. Use dampers, rake and toe to tune turn-in.

Does the driver left foot brake? Going up the box should be a clutchless shift, while downshifts can be clutchless with practise. This will allow the driver to left foot brake all the time, and minimise shift time.

Dave

Good advice, many thanks!

[Lukin]

Originally posted by bobdar
Being an older 'mercan, I am talking (thinking?) lbs and inches, but the motion ratio has no units; so the wheel rate units would be the same as your spring rate units (force/distance)--lbs./in or kg/in. Why would springs be rated in N/mm? Still curious as to what brand of chassis you have; there would be a big difference between a modern VD and a 25 year old Lola. I have a '70 Lola vintage FF and the wheel rates are about .5 X corner weight (would probably tear it apart at WR = CW).

N/m and N/mm is just a throwback to uni I use. It's a 02 VD, would you have any suggesions as to a ratio of corner weight to wheel rate?

[Lukin]

Originally posted by BRIAN GLOVER
I've been working on my Hot Rod for next weeks auction, but I have been thinking about this thread. Testing program tips is the name of this thread. You must ask yourself what your objective is. Do you want to be like Michael Schumacher or Jean Alesi? IE: Do you want to win the race or go for a Sunday afternoon drive in a car that handles really well and drive it without applying driver techniques suited for this track and this track only. Do you want to practice the "Art of Racing' or have fun. Racing is a serious business and like in Sun Tzu's, 'The Art of War', you may have to drive in a less than exemplary fashion. IE: Like Schumacher does.
I understand that this is the only track that you race on? If this is the case, there is one place to pass and that is the long straight as far as I can tell.. There are 3 corners that require a similar set up. 5,6 and 1.
Assuming you want to win the race at this track, we are not setting up for poll or even the fastest race lap, we are setting up to win.

Each lap you should pass a car down the straight and prevent anybody passing you for the rest of the lap. That is the plan. Design for this.

So first, you concentrate on the straight. It appears that there is not much difference between the performance of the cars so you have to get far out of the accepted envelope to win.
Are the engines sealed? Are the revs limited? Anyway, the engine builder must take meticulous care to build this engine. Gear ratio and axle ratio must be chosen for reaching the max speed 4/5ths down the straight.
It is interesting to hear the engines of F1 engines on the straights. Ferrari reaches max rpm in 7th just before braking for turn one at Indy, while all others reach max rpm, long before that. In fact, this track is similar to Indy because you don't know whether to setp for the turns or the straight.

To set it up go fast down the straight is obviously going to cause problems for the rest of the track.
IE: Apart from gearing, high tire pressures, high neg. cambers and spring rates are required.
Remember, Jean Alesi could not drive Michael Schumacher's car after he left Ferrari. A special driver needs to drive this car. It will be set up asymmetrically and will be a bitch to drive. Youwill have odd corner weights to get you around the right handers.
The axle shafts must be as straight as possible( We don't want any HP robbing angles.),aircraft tape is used to get rid of any parasitic drag. Cover all gaps in the body. Flair the holes in the body around suspension parts etc.
The next thing to do is to see what the car will do in turns 6, 1 and 5 with this set up. You may have to reduce the cambers on the left and steer it around turn 3 by bump tow out on the right rear. Remember, all you are doing here is preventing anybody from passing you so handling is a secondry consideration. Most will be too scared to pass when they see the car going all over the road anyway.
Braking at the end of the straights will be an experience. You will have to transfer load to the left of the car because of the stagger.. IE: you will have to be in a slight turn. This is perfect, because you will have just passed another car at the end of the straight and you will be able to brake later and deeper. I understand that people come off at the end of the main straight.
Well, you are going to have to learn a new skill to get around there and learn how to use your left foot on the brake to compensate for the cars poor handling.
As has been suggested, tire temps are not going to tell you anything unless you test with real time pyrometers. The real time visual and the hand trick is the next best thing. Once you have passed all the cars, the handling will improve as the contact patch grows but the son's of bitches will still try and pass you. You will have an easier time staving the bastards off now. How many laps in the race?

Anyway, this is how I would win this race and I'll give the booing crowd the number one gesture

I have been wondering how to respond! There is a fair bit of passing into the three right hand corners, though the one after the longest straight is the most common. There is very little passing into the left hand sweeper, it's more that people try to get a run into Turn 5.

I'm all for aggression but if we have a quick car in qualifying we wont need to pass people on each lap. Im up for staggering corner weights and settings, though we still have to maintain exit speed from the left hand corner to ensure we aren't vunerable into Turn 5. What effect will the extra weight on the outside wheel have on drive out of the corner? Im still not sure what diff we have.

Engines aren't sealed, and will be revved no doubt. You sure about hitting the limiter in top gear 4/5 of the way down the straight? Races are only 8-10 laps, which is only 10-15 minutes, very short. Cant really wait for grip to come to the car, it has to be ready to go straight away. Cant warm the tyres up or anything. Need to get better traction off the line, losing a spot waste at least 1 lap.

[Patrice L'Rodent]

Lukin,
How are things, long time no see =]
I am sure the Formula Ford regs require you to run an open diff. Anything else is simply not legal. I suspect there may well be some tricks in the assembly of a FF 'open' diff ;)
Pat

[Ben]

Originally posted by Patrice L'Rodent
Lukin,
How are things, long time no see =]
I am sure the Formula Ford regs require you to run an open diff. Anything else is simply not legal. I suspect there may well be some tricks in the assembly of a FF 'open' diff ;)
Pat

If they do the test with a torque wrench a plate diff with negative preload should do fine :-)

Hi Pat, how's things? Will you be doing FStudent in July?

Ben

[Lukin]

Hey Pat, hows things? Im good, enjoying this FFord thing. CMT didn't end up going very far but it definately gave me the bug!

I just checked the regs and....... yep, I should of picked that one up. No LSD, locking or torque biasing. Any idea's to ..... help?

[Greg Locock]

Well, it's very difficult to assemble an open diff. Any friction in the little gears stops it working properly. Cough cough.

[Lukin]

Ah I see. We wouldn't want that now......

[Patrice L'Rodent]

Lukin, Im well. Glad you are having fun, and I understand Curtin will be back in FSAEA this year.
Last time I saw a diff check in FF, they simply jacked the car up and twiddled wheels around to see if it 'felt' like a locking diff. I am sure a clever cheat could get around that =] But I would not support cheating, even if a considerable percentage of the FF field are doing it. Look at Greg and Ben's posts.

And Ben, yes, I will be doing both FSAE and FStudent this year again. I got my invite from Brian Robinson last week and was pleased to accept. Oh the delights of sunny Pontiac followed by a week in balmy Bruntingthgorpe =] Catch you there I guess.
Pat

[Lukin]

We use the Kent 1600cc, does anyone know the maximum power people get and the best engine builders around the world?