The 'Tools", What do they do?

[Hoop-98]

I thought this gap in the schedule, might be good for a tech topic.

So, I thought I would start with one of the most common driver "tools" and what it does.

The Tool is the front and rear anti-roll stiffness.

To illustrate what it does I have built a very simplified weight transfer model. It doesn't allow for tire stiffness, caster, aero, only for the difference increasing roll stiffness splits from one end to another.

This would normally be associated with the anti-roll "bar" settings, although in NASCAR they adjust the rear roll stiffness during pit stops (Track bar).

Here is the Chart.

http://i25.tinypic.com/2heftc6.jpg

This would be weight transfer during a steady state left hand turn.

Next we can discuss why it works to fix push or loose if there is any interest.

rh

[chuck34]

Hoop I love this stuff. I have done a lot of it myself. But I'm always ready and willing to talk about it with others. Sometimes it's hard to find people who will talk about it. You know "secrets" and all.

Have you ever tried to write a lap time simulator?

[Hoop-98]

Hey Chuck34, not really a lap time simulator per se, but when we raced karts I did a lot of excel stuff, some predictive of Lap Time changes with different power etc. I also tried it with St Pete and a few other tracks with decent correlation. I have some documentation on basic Lap Time Simulators but i am not proficient in Programming, with a few Calculators etc.

Back to the tools, I am just trying to simplify some of the magic/secrets for discussion purposes.

It is important to state up front, this is only the very tip of the iceberg, reality gets about 1 million times (really a million, not exaggerating) and way over my head when you look at all the dynamic stuff. However, IMO, some basic understanding of mechanical grip, tire mu, weight transfer, helps our discussions of say, driver weight.

For example; Everyone grasps the Grid Weight, but what difference does the driver weight make on weight transfer, even if we weigh with the driver.

So I am going to say that Paul Tracy or Justin Wilson cause the CGh to be .4 inch higher than say Da Matta or Patrick.

So let's see what that does to weight transfer.

I am going to pick a number to begin with, then add .4 to it.
Of course there is no Aero Weight Transfer so we will deal only with the Car/Driver/Fuel Weight.

So Car Weight 1790 Pounds, Avg CGh 13, Avg Track 65.5, Rear Weight 59 PCT. These are figures in the same general scale of an Indycar, not exact figures.
So sitting on the grid the wheels scale weight would be.

Wheel Weights LF 367 RF 367 LR 528 RR 528 Left % 50.0% Rear % 59.0% Cross % 50.0%
In a Steady State 2.5 G LH Turn with a 13 inch ACGh the weights would look like.

LF 183 RF 550 LR 264 RR 792
With a 13.4 ACGh

LF 178 RF 556 LR 256 RR 800
This is a small but measurable difference in cornering power. The closer each end is to 50/50 the better it will grip (we can discuss this later.

In the Da Matta/Patrick Example we end up with 25 Pct Left/ 75 Pct Right.
In the Tracy/Wilson Example we end up with 24.2 Pct Left/ 75.8 Pct Right.

Let's take a break.

rh

[chuck34]

Hey Chuck34, not really a lap time simulator per se, but when we raced karts I did a lot of excel stuff, some predictive of Lap Time changes with different power etc. I also tried it with St Pete and a few other tracks with decent correlation. I have some documentation on basic Lap Time Simulators but i am not proficient in Programming, with a few Calculators etc.

That's exactly what I've been trying to do. I'm basically saying that the car will corner at x g's, accelerate at y g's, and brake at z g's. Then making two half ellipses to build my g-g diagram. I wanted to do that for a start, I'll get more accurate later, maybe. Then I start at the smallest corner radius on the track. Set longitudinal accel to zero, lateral accel to max, and work out from there. It works ok, but I run into issues when the corner radius tightens down on exit or entry, but doesn't go to the min value. Basically I need to work on my accel/brake "logic" I think. Either that or fudge my track map so that it doesn't ever have tight radiuses (radii?) on exit and entry.

Anyway, sorry to hijack your thread. I really enjoy that sort of stuff. As you can probably tell from my sig. If you don't have a copy of the Milliken book you really should pick up a copy. It's great for this sort of thing.

[chuck34]

Perhaps one thing that you might want to point out for those new to this is tire load sensitivity.

Basically a tire produces more cornering force if it has more normal force on it. Normal force being what you measure with a scale. So the more "weight" on a tire, the more cornering force it can create. The problem with this is that you don't gain as much by loading a tire as you loose by un-loading a tire.

So using Hoops first example, you have 394lbs on each front tire statically. Then in a 1.8g turn you now have 276LF 512RF. That means that you have gained 118lbs on the RF, and lost 118lbs on the LF.

Using made up numbers, because I don't know the tire properties of an IC tire. That means that you have probably gained about 100lbs of cornering force on your RF (compared from static), but lost about 120-150lbs of cornering force on you LF (again compared from static).

What that boils down to is that you want to have your tires evenly loaded (side to side) in mid corner. In that situation you will have the most cornering power. That is why oval track cars have more left side weight. They start with more weight on the left side so that when load is transfered in the corner (from your left side tires, to your right side tires), they end up with even tire loads under cornering.

Clear as mud?

[Hoop-98]

Perhaps one thing that you might want to point out for those new to this is tire load sensitivity.

Basically a tire produces more cornering force if it has more normal force on it. Normal force being what you measure with a scale. So the more "weight" on a tire, the more cornering force it can create. The problem with this is that you don't gain as much by loading a tire as you loose by un-loading a tire.

So using Hoops first example, you have 394lbs on each front tire statically. Then in a 1.8g turn you now have 276LF 512RF. That means that you have gained 118lbs on the RF, and lost 118lbs on the LF.

Using made up numbers, because I don't know the tire properties of an IC tire. That means that you have probably gained about 100lbs of cornering force on your RF (compared from static), but lost about 120-150lbs of cornering force on you LF (again compared from static).

What that boils down to is that you want to have your tires evenly loaded (side to side) in mid corner. In that situation you will have the most cornering power. That is why oval track cars have more left side weight. They start with more weight on the left side so that when load is transfered in the corner (from your left side tires, to your right side tires), they end up with even tire loads under cornering.

Clear as mud?

Much lower opacity than mud!

For example:

http://i31.tinypic.com/20hvwwx.gif

or

http://i32.tinypic.com/vzwrj4.jpg

So the bottom line we want to minimize weight transfer either by,

Wider Track (Not Allowed)

Lower Center of Gravity ( Newer tub or lighter driver allows ballast placement)

Driver with Lower CG ( Additional ballast, or lower upper body weight)

We can't stop Left to right weight transfer, but with roll stiffness we can make wither the Outer Front, or Outer Rear carry more of the transferred weight.

More front resistance loads the RF, unloads the RR, reducing the spread (difference)across the rear and increasing the spread across the front, or more rear grip.



rh

[chuck34]

Thanks Hoop. I usually try to use charts and graphs when explaining this stuff. But I don't have anything at my fingertips here at home. :-(

[Chamoo]

Well this stuff is very interesting. You guys obviously know a lot more then the average joe.

Keep doing things of this nature. I don't know what all of it means, but I'll learn a hell of a lot faster reading these messages then if I never see them from you guys.

These technical talks add a nice element to these forums.

[chuck34]

Well this stuff is very interesting. You guys obviously know a lot more then the average joe.

Keep doing things of this nature. I don't know what all of it means, but I'll learn a hell of a lot faster reading these messages then if I never see them from you guys.

These technical talks add a nice element to these forums.

What don't you understand? Ask questions. There really are no dumb questions, so ask away. That helps you learn, and therefore enjoy the racing more. And it'll help me to better understand as well. Teaching is the best way to learn something. :-)

[Hoop-98]

I'll echo what Chuck said, we aren't high muckety engineers, just fans with some understanding and tons of questions.

rh

[garyshell]

I'll echo what Chuck said, we aren't high muckety engineers, just fans with some understanding and tons of questions.

rh


Ok then, just muckety engineers. Certainly not mere mortals like most of the rest of us here! :s mokin:

Gary

[Marbles]

That's interesting. I never thought about the drivers centre of gravity.

If I may attempt to contribute in a wholly unscientific way:

http://www.aaim1.com/pdfs/anatomy.pdf

Note figure 12.

Imagine the anti-roll bar as a 12 inch ruler in your hands. Holding it out and with the flat side down it is more easily bent towards the floor. This would be the extreme soft setting. This would be for a rough circuit or a drivers adjustment for rain.

Hold the ruler with the flat of it facing you and it can no longer be bent towards the floor. This is the extreme stiff setting.

On a road circuit, some drivers will adjust these settings over the the course of a single lap... every lap. Also, drivers have their own preferences regardless of what engineers recommend. J. Villeneuve was notorious for being pig headed about having a stiff setup.

I have a question for those who may know. I recall some drivers, specifically Mario Andretti, would often twitch the car right before turning left into the corner during Indy qualifying. Did this have a real world benefit (in regards to loading the right side) or was just a nuance of the driver.

[NickFalzone]

I'm a little too dense and/or lazy to closely follow what's been discussed so far, let alone going into further mathematical detail. But I have been wondering about a few things:

1. What role does driver weight, under the current weight "balanced" system, play on road courses and ovals? Do the shortest and/or lightest weight drivers have an advantage because the ballast can be placed in a more helpful area than that weight would be on a larger driver? Does this stuff come more into play depending on whether it's an oval or a road course?

2. Is usage of the tools a skill that very experienced drivers, like say Dario, have an advantage over less experienced drivers, like Conway? In other words, does it take a lot of experience to make good use of the tools, or is their usage pretty obvious to even the rookies?

3. Are the tools used more on ovals or on road/street courses?

[chuck34]

That's interesting. I never thought about the drivers centre of gravity.

If I may attempt to contribute in a wholly unscientific way:

http://www.aaim1.com/pdfs/anatomy.pdf

Note figure 12.

Imagine the anti-roll bar as a 12 inch ruler in your hands. Holding it out and with the flat side down it is more easily bent towards the floor. This would be the extreme soft setting. This would be for a rough circuit or a drivers adjustment for rain.

Hold the ruler with the flat of it facing you and it can no longer be bent towards the floor. This is the extreme stiff setting.

On a road circuit, some drivers will adjust these settings over the the course of a single lap... every lap. Also, drivers have their own preferences regardless of what engineers recommend. J. Villeneuve was notorious for being pig headed about having a stiff setup.

I have a question for those who may know. I recall some drivers, specifically Mario Andretti, would often twitch the car right before turning left into the corner during Indy qualifying. Did this have a real world benefit (in regards to loading the right side) or was just a nuance of the driver.

Your PDF is a bit out of date, as it has the shifter on the right side of the cockpit. They now have paddle shifters. But other than that it give a good overview.

I like your ruler explanation of the blade type anti-roll bar. That illustrates the concept really well.

I don't know that flicking right before left would really do anything. Perhaps it's just an artifact of Mario's driving on dirt?

[chuck34]

I'm a little too dense and/or lazy to closely follow what's been discussed so far, let alone going into further mathematical detail. But I have been wondering about a few things:

1. What role does driver weight, under the current weight "balanced" system, play on road courses and ovals? Do the shortest and/or lightest weight drivers have an advantage because the ballast can be placed in a more helpful area than that weight would be on a larger driver? Does this stuff come more into play depending on whether it's an oval or a road course?

2. Is usage of the tools a skill that very experienced drivers, like say Dario, have an advantage over less experienced drivers, like Conway? In other words, does it take a lot of experience to make good use of the tools, or is their usage pretty obvious to even the rookies?

3. Are the tools used more on ovals or on road/street courses?

1) It's slightly less of an advantage for the "small guys" now that min. weight is with drivers. But it is still an advantage in just the way you say, by being able to place ballast in more usefull places.

2) There have been cases of drivers "going the wrong way" on an adjustment with dire results. Particularly at the Speedway. This could be either the driver didn't know if he wanted to go stiffer/softer, or that he thought he was going stiffer but moved the lever softer type of thing.

3) They are used pretty extensively on both types of courses.

[Chamoo]

Not sure if you guys would know about this stuff, but it is still HP based I would think.

How much are the taller drivers like Justin Wilson and Graham Rahal disadvantaged by blocking part of the air intake?

[Hoop-98]

Not sure if you guys would know about this stuff, but it is still HP based I would think.

How much are the taller drivers like Justin Wilson and Graham Rahal disadvantaged by blocking part of the air intake?

16 - 18 HP would be 1 MPH at Indy so doubt it is more than 5 or so. Strictly a guess. The ram is worth about 20 total I have been told so I am guessing 2-5.

rh

[PA Rick]

The great thing about the sport is the way teams work together to compensate for the hundreds of variables.
The static weight distribution and tilt table cornering variables are the real foundation, but like people have said there is much interactive stuff going on.
Tires and track condition change throughout the race and if you don't have a good base setup you could chase handling all over the place.
Driving style also is a huge variable as some drivers lean on the rears and others are more neutral. A car set up for one driver could be a real handful for another. Also, some drivers can communicate the handling more efficiently so the settings can be improved.

[Hoop-98]

Interestingly enough, much of the research on 'tilt table" weight transfer and push/loose was funded by GM for the Corvair defense.

They could make a Corvair understeer by changing the front/rear roll rate and going to a double joint axle shaft for better roll center location andd to prevent jacking..

This was important because Corvairs, Renault, Volkswagens, were 'loose".

The problem there is when a Falcon or Dart pushed and you let off the gas it helped.

When a loose car lets off the gas it oversteers more, which is why no one wants a car loose on entry.

GM fixed the Corvair, Renault and VW didn't but Nader wrote a book (being a trial lawyer advocate, it was go for the money, plus GM made a horrible mistake by putting PI's on him ) so no more Corvair while VW's carried the same faults for another decade.

If GM suspension engineers had been let loose in F1 in the 60's they would have killed them.

As it was a few of the guys like Jim Hall went US sports car racing and did ok.

rh

[PA Rick]

You didn't mention the Spitfire. Formula 1 like coil over shock unequal A arm front suspension, horse and buggy like swing axle transverse leaf spring rear. I feel like I'm stuck in a time warp with the front in the future and the rear in the past.

[Hoop-98]

You didn't mention the Spitfire. Formula 1 like coil over shock unequal A arm front suspension, horse and buggy like swing axle transverse leaf spring rear. I feel like I'm stuck in a time warp with the front in the future and the rear in the past.

Well be sure you keep the roll couple properly balanced between the future and the past, not sure if push or loose works best in temporal displacements....


rh

[PA Rick]

Well be sure you keep the roll couple properly balanced between the future and the past, not sure if push or loose works best in temporal displacements....


rh

With 58 horspower, most adjustments are futile.

[chuck34]

With 58 horspower, most adjustments are futile.

Of course. But since this is a time warp car, does horsepower really matter? I mean if you can warp space-time, you can go any speed you want, right? :-)

[wedge]

On the subject of weight transfer does anyone put up pictures of the weight jacker system (not just the lever) and how does it work exactly when a driver makes an adjustment?

[Hoop-98]

There are quite a few different types, here is one example...

http://www.pitstopusa.com/images/ALL64220.jpg

rh

[chuck34]

There are quite a few different types, here is one example...

http://www.pitstopusa.com/images/ALL64220.jpg

rh

To explain that a bit more. The crank (left side of the picture) goes in the cockpit. That's the adjuster the driver uses. The jack itself is on the upper right of this picture. What it is, is basically a little ram that pushes on the spring. That causes more pre-load in that spring. That means a bit more static load on that wheel. Think of it a bit like putting a matchbook under a wobbly table leg.

The other two rings in the picture are bearings so that the spring doesn't bind up.

[Hoop-98]

To explain that a bit more. The crank (left side of the picture) goes in the cockpit. That's the adjuster the driver uses. The jack itself is on the upper right of this picture. What it is, is basically a little ram that pushes on the spring. That causes more pre-load in that spring. That means a bit more static load on that wheel. Think of it a bit like putting a matchbook under a wobbly table leg.

The other two rings in the picture are bearings so that the spring doesn't bind up.

i think the thing to remember is that a weight jacker can't move weight left , right, or fore/aft.

If it is installed on the LR/RF axis, increasing the load would Add Tire Load to the RF/LF or lowering would do the opposite.

This is often referred to as cross weight, or wedge.

On an oval track increasing cross would normally tighten the car up by increasing rear grip, lowering front.

It lowers the rear L/R split and increases the front L/R split.

Of course the lower the split, (closer to 50/50) the more grip is available from the tires.

So stiffer front roll and more cross both do similar things.

Now where a shock/damper can come to play might be the next discussion?

rh

[wedge]

I'm called Wedge for no reason!

What I was meant to say was where precisely is the weight jacking spring located on an Indycar?

[Hoop-98]

In the past they have been moved around to different corners. Not sure about the current dallara, here's one on the RF of an older model.

http://insideracingtechnology.com/Resources/irwtjkr.jpg


rh

[Hoop-98]

Some real life charts, but not sure what years, older for sure. Interesting to compare the f1/CART

http://i28.tinypic.com/2hdv7mr.jpg

http://i25.tinypic.com/241v0iw.jpg

http://i25.tinypic.com/9vebrr.jpg

rh

[Chamoo]

Can either of you describe the difference between Sarah Fisher's new car and her old car? Their PR said the new car was 25 pounds lighter then the old one. Are there any other benefits? What will 25 pounds do for her at Homestead?

[chuck34]

Can either of you describe the difference between Sarah Fisher's new car and her old car? Their PR said the new car was 25 pounds lighter then the old one. Are there any other benefits? What will 25 pounds do for her at Homestead?

I don't know about the weight, specifically where that would have come from. But 25lbs should help out quite a bit due to the "new" ability to place teh weight where they want it to adjust for specific characteristics.

The biggest benefit will be in torsional rigidity. Even though these tubs are really strong and built to last, all tubs will flex and weaken over time/use. Therefore her new tub will be stiffer/more rigid. That means that any change made in set-up will make a bigger, or more distinct, impact on handling.

[Chamoo]

I don't know about the weight, specifically where that would have come from. But 25lbs should help out quite a bit due to the "new" ability to place teh weight where they want it to adjust for specific characteristics.

The biggest benefit will be in torsional rigidity. Even though these tubs are really strong and built to last, all tubs will flex and weaken over time/use. Therefore her new tub will be stiffer/more rigid. That means that any change made in set-up will make a bigger, or more distinct, impact on handling.

Great, thank you.

I believe the 25 pounds comes from repairs to the chassis/tub by Dallara. I believe I remember somewhere that patching cracks and break in the tub added weight. 7 years using the same tub would add up to alot of repairs and fixes.

Also, different materials from 7 years ago may add to the lightness of the chassis?

[chuck34]

Great, thank you.

I believe the 25 pounds comes from repairs to the chassis/tub by Dallara. I believe I remember somewhere that patching cracks and break in the tub added weight. 7 years using the same tub would add up to alot of repairs and fixes.

Also, different materials from 7 years ago may add to the lightness of the chassis?

Ah yes, I didn't think about that. The repairs would add a bit of weight.

I wouldn't think that they would use different materials now than 7 years ago. They are probably using the same spec. I don't think they would want to take the time/spend the money to re-qualify a new design/materials for a spec series. But I could be wrong.

Yep, the 25lbs probably comes from the repairs.

[Chamoo]

Ah yes, I didn't think about that. The repairs would add a bit of weight.

I wouldn't think that they would use different materials now than 7 years ago. They are probably using the same spec. I don't think they would want to take the time/spend the money to re-qualify a new design/materials for a spec series. But I could be wrong.

Yep, the 25lbs probably comes from the repairs.

I'd love to see a 7 year old tub to see all the cracks and such. It must be just absolutely covered in repairs and scars from wrecks and cracks.

[Easy Drifter]

It is an old joke/truism that there were a lot of old fast McLaren Mk1/2/3 Can Am cars but no old fast Lola T70s. The early McLaren's were tube frame and the Lola's were early tubs of basically stressed skin aluminum. The McLaren's maintained their (relatively weak) rigidity while the Lolas became real flexi flyers.
The progressive lack of ridigity in an early tub design due to stresses was not really understood (at least by most people) in those days.
In my opinion some of the problems some teams are having today are tubs that are long past their best before date and/or too many repairs. A repaired tub is unlikely to have maintained the same ridgidity as as an undamaged tub.
I am not sure now with all the rule changes in F1 but a few years ago a tub was relegated to the test team after 4 to 6 races.
Sarah's performance in what has to be a real piece of brown stuff has been impressive.

[PA Rick]

In the past they have been moved around to different corners. Not sure about the current dallara, here's one on the RF of an older model.

http://insideracingtechnology.com/Resources/irwtjkr.jpg


rh

In the photo I only see two springs. Doesn't the Dallara use three springs? The center spring acts like an anti roll bar to lower the unloaded corner when the loaded corner deflects under cornering.

[Hoop-98]

In the photo I only see two springs. Doesn't the Dallara use three springs? The center spring acts like an anti roll bar to lower the unloaded corner when the loaded corner deflects under cornering.

I believe that would be an option or choice for a team to make. I haven't seen any third spring installs on recent Dallara's or any front spring setups period on the current model. I think the DP01 allowed for one but I don't believe the series allowed it.

The "Third Spring"

http://i33.tinypic.com/2112jip.jpg

Is normally installed to add bump resistance when both wheels are traveling together.


rh

[grungex]

DP-01 rear.

http://i202.photobucket.com/albums/aa208/grungexx/100_9630a.jpg

[Hoop-98]

So a third shock with packers but no spring. I believe here we are trying to limit bump travel from aero loads.

Here is a third spring on the front of a Lola at Long Beach.

http://i38.tinypic.com/4zuhhv.jpg


rh

[chuck34]

I believe that would be an option or choice for a team to make. I haven't seen any third spring installs on recent Dallara's or any front spring setups period on the current model. I think the DP01 allowed for one but I don't believe the series allowed it.

The "Third Spring"

http://i33.tinypic.com/2112jip.jpg

Is normally installed to add bump resistance when both wheels are traveling together.


rh

Hoop, is that an F1 rear end? If so then the "roll springs" (is that a proper term?) would be torsion springs? And as such located along the axis of the bell crank? If not, then there doesn't appear to be any roll resistance, other than the "pre-load" in the shock?

The third spring/mono-shock set-ups tend to get fairly complicated. The easiest way to think of it is that with that type of set-up you can have a fairly compliant car in roll (very desirable) but that doesn't drag the ground because of the aero loads (very bad). You might hear some people say something along the lines of "the roll and pitch modes have been de-coupled". That is a bit of an over simplification, but it may help illustrate the point. Maybe?

[Hoop-98]

Hoop, is that an F1 rear end? If so then the "roll springs" (is that a proper term?) would be torsion springs? And as such located along the axis of the bell crank? If not, then there doesn't appear to be any roll resistance, other than the "pre-load" in the shock?

The third spring/mono-shock set-ups tend to get fairly complicated. The easiest way to think of it is that with that type of set-up you can have a fairly compliant car in roll (very desirable) but that doesn't drag the ground because of the aero loads (very bad). You might hear some people say something along the lines of "the roll and pitch modes have been de-coupled". That is a bit of an over simplification, but it may help illustrate the point. Maybe?

No that's a sports car.

Another word used is softer in Warp or along the diagonals.

rh

[chuck34]

1) No that's a sports car.

2) Another word used is softer in Warp or along the diagonals.

rh

1) Sports cars also make use of torsion bars sometimes. Please tell me that is the case (torsion bar suspension) in the picture you posted. Otherwise I may need to re-evaluate my engineering fundimentals. :-)

2) Yes, but Warp is a whole 'other issue. And gets us back to PA Rick's questions. ;-)

[PA Rick]

And where is the best place to hide the mass dampers?

[Hoop-98]

And where is the best place to hide the mass dampers?

If they are illegal in IndyCar they are big enough to be hard to hide. If they aren't in the rules maybe in the nose somewhere.

Remember though PARick, I am not an IndyCar crew member. So other than the pictures I take at the races and what i can read or discover in books and online I am discussing the basics of handling theory, not the reality of current practice.. Sometimes a crew member or engineer will correct me or share something, but I am a fan of the technology, not a real life Indycar engineer.

The mass damper brings into the discussion the other 4 springs, the tires, which are undampened. Also in a F1 car 30 - 50 pct of the travel may come from these undampened springs.


As far as warp, well I think in concept is that with a third spring offering much of the aero load resistance, we can get more wheel travel and better compliance or mechanical grip as wheels encounter road irregularities.

We will likely see more development in the "interconnected suspension" area, unless restricted in rules. More complex interconnected hydraulic systems are out there now.


rh

[chuck34]

Hoop, one point of correction. I hate to be a jerk, but one of my professors beat this into us in College, so now it is sort of one of my querks.

A mass/spring system (suspensions) are damped. "Shocks" are dampers, they damp out ocilations.

Things are dampENed in the rain.

Just one of those nit-picky things we all have I guess.

:-)

[chuck34]

We will likely see more development in the "interconnected suspension" area, unless restricted in rules. More complex interconnected hydraulic systems are out there now.


rh

I believe that most of those interconnected hydraulic systems are outlawed in the IRL. But I believe that they are popping up on sports cars and F1.

[Hoop-98]

Hoop, one point of correction. I hate to be a jerk, but one of my professors beat this into us in College, so now it is sort of one of my querks.

A mass/spring system (suspensions) are damped. "Shocks" are dampers, they damp out ocilations.

Things are dampENed in the rain.

Just one of those nit-picky things we all have I guess.

:-)

Gotcha Dampers damp, dampeners moisten.

That's ok, my sticky is motors and engines, you connect power to a motor, you fuel an engine.

rh

[Nem14]

Great stuff.

These forums had tech discussion sections for F1, Indy Car and NASCAR at one time. To bad they still don't.

[Hoop-98]

Dampen;
Meaning #1: smother or suppress
Synonym: stifle

Meaning #2: make moist
Synonyms: moisten, wash

Meaning #3: deaden (a sound or noise), esp. by wrapping
Synonyms: muffle, mute, dull, damp, tone down

Meaning #4: reduce the amplitude (of oscillations or waves)

Meaning #5: make vague or obscure or make (an image) less visible
Synonyms: deaden, damp

Meaning #6: check; keep in check (a fire)

Meaning #7: lessen in force or effect
Synonyms: damp, soften, weaken, break

hmmmm


rh

[chuck34]

Dampen;
Meaning #1: smother or suppress
Synonym: stifle

Meaning #2: make moist
Synonyms: moisten, wash

Meaning #3: deaden (a sound or noise), esp. by wrapping
Synonyms: muffle, mute, dull, damp, tone down

Meaning #4: reduce the amplitude (of oscillations or waves)

Meaning #5: make vague or obscure or make (an image) less visible
Synonyms: deaden, damp

Meaning #6: check; keep in check (a fire)

Meaning #7: lessen in force or effect
Synonyms: damp, soften, weaken, break

hmmmm


rh

Ok, so that Prof. is full of crap. What else did he tell us that was wrong?

Now I have to question everything. :-(

[Hoop-98]

Great stuff.

These forums had tech discussion sections for F1, Indy Car and NASCAR at one time. To bad they still don't.

Well me too, but if it's not about Versus, Danica, the demise of the IRL, it's not a big topic here.
Thanks for participating.

rh

[Easy Drifter]

Hoop: I have been enjoying this thread.
Of course, as you know, there are many ways to alter a cars handling in addition to adjusting the bars or wheel loading.
A simple tire pressure change can do it as well as damper settings, ride height, spring rates or little aero tweeks among others. The big trick is to figure out which one to use that least affects other areas of performance.
Don't get me wrong I am not been at all critical of your postings I just wanted to have others understand there are other adjustments possible. I expect most who have been following this understand that but some might not.
One car that was exceptionally sensitive to a little tiny areo tweaks was the Chevron B25/27/29 series. A little 'kicker' between the main nosecone and the allowed raise at the outer end of the sports car nose was a neat little mod. that those in the know used. Only about 6 inches long a adjustment of a 1/32 of an inch could change understeer to oversteer or the other way. We often ran them illegally high but as soon as the car left the track a crew man with a nylon or plastic hammer would knock them down. We all hid what height we were running them from each other and only adjusted them just before going on the track.

[chuck34]

Hoop: I have been enjoying this thread.
Of course, as you know, there are many ways to alter a cars handling in addition to adjusting the bars or wheel loading.
A simple tire pressure change can do it as well as damper settings, ride height, spring rates or little aero tweeks among others. The big trick is to figure out which one to use that least affects other areas of performance.
Don't get me wrong I am not been at all critical of your postings I just wanted to have others understand there are other adjustments possible. I expect most who have been following this understand that but some might not.
One car that was exceptionally sensitive to a little tiny areo tweaks was the Chevron B25/27/29 series. A little 'kicker' between the main nosecone and the allowed raise at the outer end of the sports car nose was a neat little mod. that those in the know used. Only about 6 inches long a adjustment of a 1/32 of an inch could change understeer to oversteer or the other way. We often ran them illegally high but as soon as the car left the track a crew man with a nylon or plastic hammer would knock them down. We all hid what height we were running them from each other and only adjusted them just before going on the track.

The tire pressure changes you speak of work EXACTLY like a spring rate change. Tire pressures are just a finer adjustment than a spring change usually is. And MUCH easier to do during a race.

As for the nose mod on your Chvron, while I have no direct experience with that car, in general aero works in the same general sense as spring changes.

It's ALL about loading the tires to the optimum amount to maximize the acceleration vector.

It's the details, like your hammer, that make racing interesting.

[Easy Drifter]

Very true Chuck.
I just wanted people to understand there are several ways to accomplish the optimum and the key is to figure out the right one!
You might want to look at a very new forum that Hoop and I belong to www.motorsportengineering.net (http://www.motorsportengineering.net)
It is just getting started so there is not a lot there yet but it does have possibilities

[Hoop-98]

Hoop: I have been enjoying this thread.
Of course, as you know, there are many ways to alter a cars handling in addition to adjusting the bars or wheel loading.
A simple tire pressure change can do it as well as damper settings, ride height, spring rates or little aero tweeks among others. The big trick is to figure out which one to use that least affects other areas of performance.
Don't get me wrong I am not been at all critical of your postings I just wanted to have others understand there are other adjustments possible. I expect most who have been following this understand that but some might not.
One car that was exceptionally sensitive to a little tiny areo tweaks was the Chevron B25/27/29 series. A little 'kicker' between the main nosecone and the allowed raise at the outer end of the sports car nose was a neat little mod. that those in the know used. Only about 6 inches long a adjustment of a 1/32 of an inch could change understeer to oversteer or the other way. We often ran them illegally high but as soon as the car left the track a crew man with a nylon or plastic hammer would knock them down. We all hid what height we were running them from each other and only adjusted them just before going on the track.

Absolutely agree Chevron. I was just trying to start the discussion in a very simple fashion. Tire's are a very significant part of the spring equation and even Kart racers "spring rate" their tires to get the right spring rates from supposedly identical tires.

Also the Tire Spring rate is in "series" with the wheel rate (Spring rate x motion ratio).

http://www.miracerros.com/mustang/t_wheel_rate.gif

http://i33.tinypic.com/fyz7up.jpg



Now next we get into rising rate lol...


rh

[chuck34]

Very true Chuck.
I just wanted people to understand there are several ways to accomplish the optimum and the key is to figure out the right one!
You might want to look at a very new forum that Hoop and I belong to www.motorsportengineering.net (http://www.motorsportengineering.net)
It is just getting started so there is not a lot there yet but it does have possibilities

Yep, there are thousands (millions?) of possibilities on how to do these things.

Hoop sent me that link a while ago, and I haven't had time to take a look at it yet. Maybe today.

[chuck34]

Also the Tire Spring rate is in "series" with the wheel rate (Spring rate x motion ratio).

rh

The tire spring rate is not multiplied by the motion ratio. In order to get the "wheel center rate" you would first get the ride rate (spring rate*motion ratio^2) *don't forget to square the motion ratio*. Then as you said the ride rate and wheel rate are in series. So in order to get the wheel center rate you have to use the formula:

Kw=(Kr*Kt)/(Kt-Kr)

where,
Kw=wheel center rate
Kr=ride rate
Kt=tire rate

That naming convention is what is used by Milliken. But I find it isn't used by too many people in the field. Milliken's wheel center rate is usually called suspension rate or total ride rate. And what Milliken calles ride rate is what a lot of engineers in the field call wheel rate. As you can see, it can get a bit confusing. So be sure to know what someone is talking about. But in general I use the "engineer's" terms, not Milliken.

[Hoop-98]

The tire spring rate is not multiplied by the motion ratio. In order to get the "wheel center rate" you would first get the ride rate (spring rate*motion ratio^2) *don't forget to square the motion ratio*. Then as you said the ride rate and wheel rate are in series. So in order to get the wheel center rate you have to use the formula:

Kw=(Kr*Kt)/(Kt-Kr)

where,
Kw=wheel center rate
Kr=ride rate
Kt=tire rate

That naming convention is what is used by Milliken. But I find it isn't used by too many people in the field. Milliken's wheel center rate is usually called suspension rate or total ride rate. And what Milliken calles ride rate is what a lot of engineers in the field call wheel rate. As you can see, it can get a bit confusing. So be sure to know what someone is talking about. But in general I use the "engineer's" terms, not Milliken.

Sorry I wasn't clear...obviously motion ratio doesn't apply to the tire. And yes the nomenclature varies by series, geography, nationality etc. Oh don't forget to throw in the sine of the spring mounting angle if any.

rh

[chuck34]

Sorry I wasn't clear...obviously motion ratio doesn't apply to the tire. And yes the nomenclature varies by series, geography, nationality etc. Oh don't forget to throw in the sine of the spring mounting angle if any.

rh

The spring angle only applies to McPherson struts, I think? And then it really sort of acts like the motion ratio. To me at least I always think about motion ratio as sort of like taking the spring off, jacking the hub up by x amount, and measuring the displacement between spring perches. I would do this at a fairly fine resolution so that you can capture any non-linearities.

[BoilerIMS]

Gents, please keep this thread going! The uber-dorky engineer in me is loving this.

[chuck34]

Gents, please keep this thread going! The uber-dorky engineer in me is loving this.

Dorks of the world unite!!

Dyslexics of the world untie!!

Sorry, hope that doesn't offend anyone, I just find it funny. :-)

[garyshell]

Dorks of the world unite!!

Dyslexics of the world untie!!

Sorry, hope that doesn't offend anyone, I just find it funny. :-)


Screw political correctness, it IS funny.

Gary

[Hoop-98]

The spring angle only applies to McPherson struts, I think? And then it really sort of acts like the motion ratio. To me at least I always think about motion ratio as sort of like taking the spring off, jacking the hub up by x amount, and measuring the displacement between spring perches. I would do this at a fairly fine resolution so that you can capture any non-linearities.

http://i33.tinypic.com/9tizhj.gif



The spring angle is illustrated above.

There are lots of calculators where you put in D1,D2 and angles and or course with a rising rate suspension it as always, gets more complicated.


rh

[PA Rick]

http://i33.tinypic.com/9tizhj.gif



The spring angle is illustrated above.

There are lots of calculators where you put in D1,D2 and angles and or course with a rising rate suspension it as always, gets more complicated.


rh

The d1 d2 ratio and spring angle determine the actual spring rate(the actual rate of the spring itself) vs vehicle spring rate. The important ratio is upper A arm to lower A arm length which compensates for camber changes as the car rolls. In a McPherson strut suspension the spring/strut angle sort of acts the same way.

[Hoop-98]

The d1 d2 ratio and spring angle determine the actual spring rate(the actual rate of the spring itself) vs vehicle spring rate. The important ratio is upper A arm to lower A arm length which compensates for camber changes as the car rolls. In a McPherson strut suspension the spring/strut angle sort of acts the same way.

I would add that the angles are most important in controlling the camber curve. With the above illustration you can see that due to the angles the suspension will curve negative in compression and positive in extension.


rh

[chuck34]

http://i33.tinypic.com/9tizhj.gif



The spring angle is illustrated above.

There are lots of calculators where you put in D1,D2 and angles and or course with a rising rate suspension it as always, gets more complicated.


rh

I would have to look "under the hood" of your calculator, but I would suspect they use the D1, D2 to figure motion ratios. So perhaps I was a bit "sloppy" in my earlier explaination. I wasn't thinking about this type of suspension, I was thinking more along the lines of modern IndyCar/Sports car types with bell cranks, etc.

[chuck34]

The d1 d2 ratio and spring angle determine the actual spring rate(the actual rate of the spring itself) vs vehicle spring rate. The important ratio is upper A arm to lower A arm length which compensates for camber changes as the car rolls. In a McPherson strut suspension the spring/strut angle sort of acts the same way.

What you are talking about with teh upper/lower arm angles is called camber recovery. And in a strut suspension there is very little camber recovery. Since the upper arm is basically the body, the camber pretty much just "rolls over" with the body. There is a bit of recovery because of the angle of the lower arm/spring, but not much.

[Hoop-98]

I would have to look "under the hood" of your calculator, but I would suspect they use the D1, D2 to figure motion ratios. So perhaps I was a bit "sloppy" in my earlier explaination. I wasn't thinking about this type of suspension, I was thinking more along the lines of modern IndyCar/Sports car types with bell cranks, etc.

If you wanna peek ;P

http://i33.tinypic.com/sxzlo5.gif

rh

[Hoop-98]

What you are talking about with teh upper/lower arm angles is called camber recovery. And in a strut suspension there is very little camber recovery. Since the upper arm is basically the body, the camber pretty much just "rolls over" with the body. There is a bit of recovery because of the angle of the lower arm/spring, but not much.

The Key with a fixed mount strut suspension is that the lower arm be near parallel to the ground in full compression.

http://i38.tinypic.com/24nmw0m.gifhttp://i36.tinypic.com/13z39d5.gif

Mustang Strut ======================Short/Long Arm

I have always called this camber gain btw.

rh

[chuck34]

If you wanna peek ;P

http://i33.tinypic.com/sxzlo5.gif

rh

That must be a code I don't know? I don't see any equations there, maybe I missed it?

[chuck34]

The Key with a fixed mount strut suspension is that the lower arm be near parallel to the ground in full compression.

http://i38.tinypic.com/24nmw0m.gifhttp://i36.tinypic.com/13z39d5.gif

Mustang Strut ======================Short/Long Arm

I have always called this camber gain btw.

rh

Sweet animations. Where did you get them, and can you make them play slower?

The other thing to remember is that while bump (what your animations show) is interesting for certain things, it isn't nearly as interesting as roll. That's because the car is more in a roll state when cornering than bump.

Yep, camber gain/camber recovery are the same thing. I suppose most call it gain though.

[Hoop-98]

Sweet animations. Where did you get them, and can you make them play slower?

The other thing to remember is that while bump (what your animations show) is interesting for certain things, it isn't nearly as interesting as roll. That's because the car is more in a roll state when cornering than bump.

Yep, camber gain/camber recovery are the same thing. I suppose most call it gain though.

On the calculator thing I was pulling your leg, I just put the formulas into excel.

The animated gifs could be edited with a gif editor, I found them at the site listed on the image. I had to download them as I got a Hot Link error, I googled to find them.

Yes a roll illustration would be cool, but most are greatly exaggerated as Indycars don't roll much or travel much period. I will look for some illustrations.

Also, back on motion ratio etc.., with a bell-crank linkage, the motion ratio is most likely non-linear so you can't solve that with a simple equation.

jm2c
rh

[chuck34]

On the calculator thing I was pulling your leg, I just put the formulas into excel.

Gottcha. I guess I'm pretty gullable a lot of the time. :-(


The animated gifs could be edited with a gif editor, I found them at the site listed on the image. I had to download them as I got a Hot Link error, I googled to find them.

No gif editor, or at least I don't know if I would have one. And I can tell that there is a site on the image, but it's going too fast to make out. :-(


Yes a roll illustration would be cool, but most are greatly exaggerated as Indycars don't roll much or travel much period. I will look for some illustrations.

And F1 even more so. I'm not sure those guys even really care about suspension geometry much anymore. Just keep the "platform" from moving around much so that the aero works, and no one cares much past that.


Also, back on motion ratio etc.., with a bell-crank linkage, the motion ratio is most likely non-linear so you can't solve that with a simple equation.

For the small movements found in IndyCars, it can be fairly linear. But I don't know if that's what these guys use or not. I just don't have much (as in basically a tick more than zero) hands on experience with IndyCar suspensions.

[chuck34]

Hoop, you know much about dampers? That seems to be where the real "black magic" is. I know a bit, but as always, I'd love to know more.

[Hoop-98]

Hoop, you know much about dampers? That seems to be where the real "black magic" is. I know a bit, but as always, I'd love to know more.

I'm fairly conversant on the topic ;)

Low speed (damper piston speeds) are the main influence on dynamic tire loading and unloading.



rh

[Hoop-98]

A Damper Tuning Chart:

http://i33.tinypic.com/o5qih5.jpg

rh