CAR HANDLING AND DYNAMICS EXPLAINED

[shanks]

Thought it may be a good idea for us to have a thread where car handling dynamics are explained for those of us that dont fully understand them yet (that includes me!)

Going to start posting info - which i have found on other web-sites on this topic.

Maybe useful for people to post how they solver problems i.e. you were at track xxxx suffering from grip roll on a certain corner - fixed it by lowering the back end etc etc (just an example)

Ill post the first bit of info next which talk about one way diffs and how they work

NOTE: I have copied this info from other web-sites - i assumme the writer will be ok with this as they had posted for general use - if you are the writer and do not want your words here please get in touch and i will remove asap.

OOPLERS - do you thing this is a good thread idea? - got loads more to post up if people want to read it

[shanks]

Understanding One – Ways


THIS MISUNDERSTOOD TUNING OPTION


One-way bearings are still considered the "mystery" option in racing. We see them listed on the "Options" pages in kit instruction manuals, but how do they work? What do they do? And how will they affect your car's performance? There are several types of one-ways, and they can be installed in a variety of locations on the car. In this article, I explore the types of one-ways available and explain how they affect a car when it's racing.

INSIDE A ONE-WAY


As the name implies, a one-way bearing functions in only one way: it rides on various types of shaft that pass through its center, and the shaft, or bearing, rotates freely in one direction but locks in the other direction. A one-way bearing comprises numerous roller, or needle, bearings inside a metal case. The shape of the race allows the bearings to rotate in one direction but not the other (hence the term "one-way").

These bearings are installed so that they "lock up" to drive the shaft they're on when powered. When no drive force is being applied, the bearings are released from their locked position and will spin freely. The bearings can be in several places in the drive train, and they may be found in both nitro and electric cars.

FRONT-DIFFERENTIAL ONE-WAY. This unit replaces the front differential. The replacement unit usually incorporates two one-way bearings—one for each outdrive. This setup allows the wheels to spin independently of one another, but it doesn't allow "true" differential action in a corner; the outside wheel will simply freewheel

CENTER LAYSHAFT ONE-WAY. These units are used on both nitro and electric vehicles. On an electric car, you'll find the one-way bearing on the layshaft (the shaft to which the spur gear is attached).

The one-way bearing transfers power to the front diff under acceleration but allows it and the front belt to "freewheel" while decelerating or braking. Unlike a one-way "diff," a center one-way allows front differential action. Since most nitro-powered cars have three belts, they also have two layshafts; the one-way bearing is usually installed on the layshaft that drives the front end.




ADJUSTABLE ONE-WAY. Like the "clicker" one-way, this setup allows freewheeling action to be adjusted or locked out. It works like a miniature slipper clutch. A center one-way unit is usually fitted with a spring-loaded friction plate or plates that can be adjusted to limit one-way action when decelerating or braking. Set it loosely, and the front drive system spins freely; tightening it decreases the freedom with which it spins, and that increases front braking.




UPS AND DOWNS OF INSTALLING A ONE-WAY BEARING

By installing a one-way bearing, you change a car's driving characteristics. There are conditions for which one-way systems are very beneficial. These conditions are narrowly defined and oddly contrary to what most of us would assume to be the "ideal" conditions, so I'll explain how each type of unit affects a car.

FRONT DIFFERENTIAL ONE-WAY. This has the most dramatic effect on handling. These are generally best for high-bite surfaces with sweeping, high-speed turns. When entering a corner off throttle, the front drive spins freely and isn't affected by deceleration or braking. Under these conditions, the front tires have exceptional bite, and this results in maximum off-power steering.

Conversely, only the rear tires are used for braking, thus reducing rear bite. These conditions, without the proper chassis setup and tire combination, could result in excessive off-power oversteer. The rear-wheel-only braking is what makes this type of one-way best suited to high-bite tracks. The car would simply take too long to slow down, or it would be too difficult to control on a low- to medium-bite track. It's something like yanking the parking brake on a full-size car; it doesn't slow the car really quickly, and its rear end wiggles all over the place.

This is also why front one-ways are better suited to tracks that allow cars to carry higher speeds through the corners where rear-wheel-only braking is sufficient to scrub off enough speed to make the corner. The car can be driven with more of a rolling motion—coasting through the corners and smoothly accelerating on to the straights more like a pan car. Conversely, tracks with 2x4 barriers outlining a series of tight, low-speed corners require very hard braking to haul the car down to a safe cornering speed—not a strong point of a one-way system.

Under acceleration, a front one-way eliminates differential action. In a perfect world in which all the tires are perfectly stuck to the racing surface, this wouldn't have much of an effect on handling. What's more common, however, especially in high-speed turns, is that the diffs will unload in the direction of the inside tires and this bleeds off power that could be used for better drive out of the corners. A front one-way locks under power and delivers 100 percent of the power to the ground.

CENTER LAYSHAFT ONE-WAY. A center one-way is similar in function to a front one-way, but there's a very distinct difference between them: there's still a traditional front diff in the car. The center one-way allows the front wheels to freewheel when they want to spin faster than the rears, so it still eliminates front braking, and it's also better for high-bite tracks. The presence of a front diff, however, makes the center one-way somewhat of a compromise between having no one-ways at all and the aforementioned front one-way configuration. In some ways, the center one-way is better for tighter turning and low-bite surfaces than a front one-way.

The front diff scrubs a little more off-power speed during corner entry, so it makes the car more manageable in slower corners. It also allows "true" differential action when exiting the corners—exactly like a car without any one-ways.



An important note about one-ways and foam tires on touring cars: a one-way system should always be installed on a car that runs foam tires. They wear unevenly, and that makes the wheels rotate at slightly different speeds, even when the car is going straight. Unless there is a mechanism such as a one-way system to compensate for this, the drive train will bind, and this will worsen as the tires wear. The binding won't cause any immediate damage or significantly reduce performance. If you're reading this article, however, you probably race and want to get the most from your car. The subtle binding caused by running uneven foam tires without a one-way system could be enough to cost you the victory in a Main.



WRAP-UP


Now that you understand what a one-way bearing is and how it works, you'll be able to determine whether you need one. If you do decide to try one, keep in mind that you will have to change your driving style. Driving a car with a one-way requires a smoother, more flowing line rather than the choppy throttle/brake extremes used on tighter tracks. Given the right track conditions and the proper adjustments to driving style, however, a car that has been properly set up with a one-way drive system will be very tough to beat!

[shanks]

Springs
Stiffer springs make the car feel more responsive, more direct.StifferThey also help the car jump a little better and higher.Stiff springs are suited for high-traction tracks, which aren't too bumpy.

Softer springs are better for (mildly) bumpy tracks.They can also make the car feel as if it has a little more traction in low-grip conditions.

Stiffer Front -The car has less front traction, and less steering. It's harder to get the car to turn, the turn radius is bigger and the car has a lot less steering exiting corners.
The car will jump better, and maybe a little further.On very high-grip tracks, it's usually beneficial to stiffen the front, even more than the rear. It just makes the car easier to drive, and faster.

Softer Front - The car has more steering, especially in the middle part and the exit of the corner.
Front springs that are too soft can make the car hook and spin, and they can also make it react sluggishly.


Stiffer Rear -The car has more steering, in the middle and exit of the turn. This is especially apparent in long, high-speed corners. But rear traction is reduced.

Softer Rear -The car has generally more rear traction, in turns as well as through bumps and while accellerating.

[blue_pinky]

Ref the springs, and I'll be interested to hear some other points of view as it's been mentioned in other threads at times, I beleive the reverse to be true...

Softer = lower initial bite = less aggressive steering & less rear end bite. Body rolls more, as it rolls it applies load gradually, grip level increases slowly. Can be used on the front to prevent grip roll on high grip surfaces but can cause understeer on low grip surfaces.

Harder = higher initial bite = more agressive steering & more rear end bite. Body rolls less, load is applied quickly, grip level increases faster. Used on the front on low grip surfaces to prevent understeer but can cause grip roll on high grip surfaces.

I'm sure there is loads more to it as it also interacts with the surface smoothness, grip level, ride height, jumps, flat, etc, etc. But this is the basic theory I've been practicing up to now. It's a big balancing act setting the suspension and makes a massive difference to the cars potential so I'd be really interested to hear some other thoughts on the fundemetal theory to add to the car specific chats which happen regularly all over this site.

Nice idea on the thread by the way!

[Southwell]

http://users.telenet.be/elvo/

[shanks]

Yes pal id be interested to hear more theory too - just grabbed the info i posted off a web-site (the guy seemed to know what he was on about) sure he said he was involved in motorsport..

Perhaps ill look for a book on the issue.....

Hopefully through different peoples opinions we will get to some sort of agreement and get it made into a sticky.....

[shanks]

Originally Posted by Southwell

http://users.telenet.be/elvo/

cheers southwell - thats the site i got the first bit of info from....

Not too much point me posting the rest - everyone interested can simply follows southwells link i guess

[millzy]

just read Elvos page(s) on it

its on the link Southwell just posted

really dont need more than that - also saves millions of post about what dose this and that on a car

[shanks]

Originally Posted by millzy

just read Elvos page(s) on it

its on the link Southwell just posted

really dont need more than that - also saves millions of post about what dose this and that on a car

agreed the link does the job - no point making it messy on here

[smokes]

Get Race Car Vehicle dynamics by Miliken and Miliken...
It explains the theory, and the pratice behind it.

Spring and dampers in off road are a lot more of a compromise as they have to handle extreme impacts i.e landing of jumps with handle ruts and all while allowing the car to turn!

[terry.sc]

Originally Posted by shanks

...just grabbed the info i posted off a web-site ..

If you are going to take info from someones website just post a link to the website or at least acknowledge where you got the information from.

Otherwise people assume you wrote it which tends to upset the people who have put their time and effort into writing the articles in the first place, in the same way Jimmy gets upset when other websites "borrow" his photos.

[Garry Driffill]

I like the idea of this thread, Thanks for posting Shanks.

[mole2k]

Elvo's site is pretty comprehensive although I think it would be good to have a discussion thread on various different parts of vehicle dynamics.

[Lowie]

quote from Elvo's site:
(first page)

© Copyright 2001 by Bruno 'Elvo' Heremans. The contents of this site may not be used for commercial interests, nor for use on other sites without the author's permission.

... so my question: did you??

If not, you clearly didn't respect his wish and I suggest you remove his material ASAP.

[shanks]

get a grip for gods sake.....

i did mention that i had taken from someone else's site - just couldnt remeber where when i posted......if any of the moderators on here want it removing then remove it please!!!!!!!!!

perhaps learn a little more about copyright law as well before making comment....im not about to offer education though.....

UPDATE - i have e-mailed the site owner (that would be the guy that spent all that time putting this information onto the world wide web to be shared with others!) asking him if he wants it deleting from oople or not.

[Lowie]

Stop making such a fuzz.

Elvo clearly mentioned you had to contact him.
Then just do that.

[update] So now you did what you had to do first thing.
Big chance Elvo won't mind at all!

[Lee]

I think Elvo would be ok with it, im sure he would be slightly more annoyed if you had said this is my setup guide and then posted Elvo's