Register to reply

Race car suspension Class

by Ranger Mike
Tags: class, race, suspension
Share this thread:
missile07
#145
Jun10-11, 09:02 AM
P: 14
I agree that maybe too much weight is staying on the RF instead of transferring back to the rear but the LR is always going to hit the chain, top out the shock, or bottom out the drive shaft through the motion of the 4 link suspension.
missile07
#146
Jun10-11, 10:58 AM
P: 14
Here is an example of the chain and suspension I am talking about. This is not my car but one very similar. The chain is red and you can see it between the spring and front shock.
Attached Thumbnails
IMAG0045.jpg  
HowlerMonkey
#147
Jun13-11, 09:22 PM
P: 276
There is no single process that works with all race car suspension.

The car's class determines ultimate suspension development.

An evil "anti-chapman" once said......"any suspension will work...if you don't let it" so it really depends on your very specific application and rules more than suspension theory.


That said, this thread is full of great discussion and advice for a variety of very different applications.
Ranger Mike
#148
Jun15-11, 02:40 AM
Sci Advisor
PF Gold
P: 1,474
Thanks Howler,,glad to see another wry cynical racer has joined the fray..

I got a PM..from a racer who wishes to remain anonymous..

He drives his own dirt late model car. He is finding that the farther the roll center moves right during cornering while still staying above ground the better his car performs. He asks for input regarding this...

Secondly he finds that the left wheel camber going negative while turning left does not effect performance. How far right can the roll center move before it stops helping performance?
Ranger Mike
#149
Jun18-11, 02:20 AM
Sci Advisor
PF Gold
P: 1,474
I got a PM..from a racer who wishes to remain anonymous..

He drives his own dirt late model car. He is finding that the farther the roll center moves right during cornering while still staying above ground the better his car performs. He asks for input regarding this...


OK... if you read post 5 and 6 above it is a good review of RC height, location and Weight Jacking..
On dirt we use a very hard tire compound which requires a lower roll center to create more down force and bite. Lower Rc means more body roll and thus more side bite.

On dirt the RC is located to the Right side of the cars center line. See the diagram of weight jacking in post 6 above.

Secondly he finds that the left wheel camber going negative while turning left does not effect performance.
It may not if you are lifting the left front...need more info on this point,,

How far right can the roll center move before it stops helping performance.....
We locate the RC to the right by 3 inches to create enough leverage ( using body roll) to plant the right front tire so it sticks on corner entry. This lets the rt front tire steer and turn properly going into and at mid turn. IF we place the RC too far to the right we have too long a lever... thus lifting the left front tire as the body rolls. This will load the rt. rear tire too much under acceleration.
If we locate the RC to the LEFT of center, the car will not turn well..not enuff force to plant the rt. front tire..car will push going in and be loose coming off the turns..
HowlerMonkey
#150
Jun18-11, 06:42 PM
P: 276
I typed a long post and it disappeared.......am not typing it again as I will be busy downloading data and reducing it from our testing at the space shuttle landing facility runway......maybe later.

I didn't have any counterpoint in that post to what was written by others in this thread.

This forum seems to be governed by logic and scientific method which puts it above most any other forum I have yet seen.
Ranger Mike
#151
Jun19-11, 02:09 AM
Sci Advisor
PF Gold
P: 1,474
Thank you and I hope you will have time to review our efforts from time to time...very glad to have you notice our efforts here..
RM
Fahlin Racing
#152
Jun25-11, 08:25 PM
P: 91
Vertical laoding creates downfroce on the outside tire so the more vertical loading there is the better the outside tire sticks during cornering.
I haven't read the book you are using here, but I have read Herb Adams', and he states that when Vertical Load gets too high (for whatever design is being used) is not good, in turn reduces cornering efficiency of the vehicle.

Good stuff Mike, albeit, thought I would add that into here to add more to the visualization on VL.
Ranger Mike
#153
Jun26-11, 04:57 AM
Sci Advisor
PF Gold
P: 1,474
thanks Fahlin....good advice..
that is a classic "Push" developed by over loading the tire CF...thats what gets beginners confused when the front end pushes..is it the rear tires hooking up too much or are the front springs too soft????

When i first started " round tracking" I watched all the old timers hot lap and they would always get out of the car and walk around to the right front tire and put their hand on it to see if it was "hotter" than the right rear tire..tire pyrometers were way too expensive back then..they wanted to " make her loose and then tighten her up"...
it was all guess work back then...we had something like 7 cars racing from one small town of 10,000 people..
these were "Hobby Stocks"..big V8 in 1955-1957 Chevy, Fords were popular...we ran a 1964 Ford Fairlane. too much nostalgia..sorry..

racing is a compromise ..the chassis only really works with one set up at one particular time on one particular track for one unique set of tires at one ambient temperature...constant tuning is required to WIN...
Fahlin Racing
#154
Jun26-11, 06:17 AM
P: 91
You can also mistake an under-inflated LF tire (in circle track) for causing a 'pushing-like' situation because the contact patch is very small, if there is one. When the RF is gripping during the turn, the inside is just slipping from poor tread contact from the tire deforming.

Not having a temperature gun in the tool box just makes things more fun I think. Checking tires pressures and by touching the tires themselves after qualifying/heats/features is a good teaching tool for beginners in circle track on what part of the tire is used most. It worked for me, we moved up in the field slightly just by adjusting our air pressures when we first started.

I can't remember exactly, but I think it was in one of Smokey's books (and others I am sure)that you want each tire within a few degrees of each other (hopefully possible in the situation that is present).
missile07
#155
Jun28-11, 01:52 PM
P: 14
Mender,

I am very interested in learning more about how the spring rates change when things bind & what exactly that would do?

We still have yet to race due to rainouts & flooding here locally, so I haven't been able to test anything out.

I went back and looked at a bunch of the previous posts & reading and this is a really good forum!
rwstevens59
#156
Jul14-11, 07:48 AM
P: 16
Northeast dirt modified chassis stiffness question.

Here we go again. Just read a blurb about a new chassis builder up here in our neck of the woods extolling the virtues of his new chassis one of which is a change made to the bracing design under or around the engine area which provides better 'chassis flex'. These cars are a complete fabrication using no stock parts, think big sprint car with a lot of added sheet metal. Solid axle front and rear.

Now the race engineer in me says flex is bad, torsional stiffness is good. If the chassis has good (high) torsional stiffness it will be more tunable with springs, shocks and anti-roll bars (if you run them). Low torsional stiffness means, to me at least, that I have a large undamped spring of unknown rate for a chassis and it does not respond well to changes. The claims that these cars are 'easy' to tune on may be true only because they don't respond much to normal tuning changes.

So what am I missing? Why do a lot of the dirt car builders feel chassis flex is a good thing?
For me, I just don't get it.

Ralph
Ranger Mike
#157
Jul14-11, 08:09 AM
Sci Advisor
PF Gold
P: 1,474
Unless i missed something..i am 100 percent in agreement...

flexy flyer chassis theory been around since the straight axle was introduced...

in my opinion..Races are won by the car that gets there first. to do this..it s all about TIRES...period...if you have the best tire contact patch..you will stick better than the other guy and out corner him..given a half way decent engine and all things being more or less equal..
so how do we do this...by dealing with the with transferred when cornering..its going to transfer...nothing you can do about it..so you learn how best to deal with it..one way is to understand where the CG is and where the RC is and modify these as the rules permit,,,next is to calculate the amount of weight transferred and understand where it goes and at what time ..during the cornering process...that is why you have to understand suspensions and how they work ,,and even more importantly..how to make track side changes to deal with each situation...
rwstevens59
#158
Jul14-11, 08:34 AM
P: 16
Thanks Ranger Mike, at least I don't feel so alone in the chassis 'woods' anymore, talking to myself. LOL :-)

Now if I could just get these boys to listen to me about those tires you mentioned....
emccalment
#159
Jul16-11, 07:04 AM
P: 4
Digging through this forum, you guys post valuable information I'm dying to be able to understand better. While I'm still working on that particular aspect, I have questions that differ greatly from the current discussion thread I was hoping you could help with. Likely beginner questions, but then again, I'm a beginner. :)

Upon return from Afghanistan I'm going to be looking to buy a car for purposes of taking it to the track and really learning how to drive. Wilst reviewing a wide variety of cars I began to wonder not about initial potential for a car and its handling abilities, but for the modified potential of the cars I'm looking at.

My current questions are how the wheelbase, track, weight and center of gravity would effect a car's final performance abilities. To determine said abilities, am I going to have to go further in depth to type of suspension and characteristics of each?

I apologize if I'm asking in the wrong place, but I am enjoying this thread thoroughly.

Thanks,
Ezra
Ranger Mike
#160
Jul16-11, 11:13 AM
Sci Advisor
PF Gold
P: 1,474
Welcome and thank you for the service to our country. I recommend you consider joining SCCA. Sports Car Club of America is 200,000 member organization for the amateur motorsports fan/driver. You can join a region and enter in the PDX event which is professional driving experience where you are given instruction by SCCA official on driving the actual track like Mid Ohio. A licensed driver from SCCA will sit in the passenger seat and tech you to drive the course..Then they turn you loose. My old car crew member burned out a set of brake pads on his Toyota Camry during one of these. Then if you really want to step it up, you can by something like a Miata and compete..various classes in SCCA have strictly stock all the way to Open Wheel like we run. all types of classes for all types of budget..I seen guys drive to the track, jack up the car and change tires and go racing..super economical..there is always a racer who can help you and all you need do is ASK
btw this is how you learn about understeer (push) etc,,,in a stock car and start to modify from there,,
steve09
#161
Jul19-11, 10:58 PM
P: 13
hello everyone .
this fourm has alot of info on racing all kinds of different car classes,and i,ve been reading
through this fourm off and on.my dad has three late models one limited and two super.
I help out on the weekends and we have recently got a shock dyno.not shure what valves
work the best and shims to use any info.we race a half mile oval asphalt with sixteen deg
banking. coilover shocks with adjustments for compression and rebound.also mike what
do you recomend for a good software program.
Ranger Mike
#162
Jul20-11, 03:57 AM
Sci Advisor
PF Gold
P: 1,474
welcome..Steve 09 having purchased a shock dyno means you guys are very serious about winning. I bought one a while back. Got to dig my shock note up in the car hauler. What type software are you looking for? Usually the shock dyno has software with it?


Register to reply

Related Discussions
Car Suspension Explanation General Engineering 6
How does a Physics class differ from an Engineering class? Academic Guidance 38
In class final for a graduate EM class? Academic Guidance 3
Car Suspension Engineering Systems & Design 3
Spring suspension on car Introductory Physics Homework 4