Automotive Race car suspension Class

[smokin butts]

Thanks ranger

fuel cell location in asphalt racing
in road racing in the center of car if the fuel cell is mounted to the right
in oval racing fuel load becomes left side weight . =which deminishes as the race goes on < therefore left side weight goes away

 

[Ranger Mike]

Good question, Smokin...
Check the rule book and do not fudge when it comes to safety. When it comes to mounting, up, down, left, right, or center? The one you choose depends on the type of racing, how long your races are, and even what fuel you use.
If you run on pavement, you want the lowest possible center of gravity. Therefore, the fuel cell should be low and should not be the lowest thing on the car, but it can be as low as the frame rails. There must be substantial bracing around the cell..do not cut corners here. The cell should be mounted to the right. This is more important if you run long races in which you burn so much fuel that the cross weight changes. If you use alcohol, you will burn fuel at a much faster rate. This weight change tends to tighten the car as fuel (weight) is burned, and at the end of a race, it is better to have the car tighten up than have it get loose.

On a dirt track car, up is better because you need weight transfer. Mounting the cell high, not extremely high, but let's say on the trunk floor, aids weight transfer. This is a protected spot in the car as well. If you are using gasoline and running 20-25-lap races on a 1/4-mile bullring, the side on which you mount the fuel cell won't really matter. You probably won't use more than a couple of gallons. In this case, the loss of 15 pounds from a 3,200-pound stock car is not going to be noticed. On the other hand, if you were using alcohol, you would lose maybe 30 pounds. That might begin to be noticed, so mount the cell to the right.

For left weight, such as when using a 16-plus-gallon fuel cell filled for ballast, mount the cell to the left. Keep in mind that this corner usually takes a lot of abuse.
n some situations racers find themselves moving weight behind the rear axle to compensate for hard tires or very low traction conditions. While this can work, it is a double-edged sword. As weight is placed farther behind the rear axle, front-wheel weight decreases and steering control is reduced. Think of it as a seesaw, (see Diagram) as weight is increased or moved farther behind the fulcrum, the amount of weight felt at the front of the chassis decreases--especially when the forces of acceleration and the car bouncing through rough parts of the track are factored in. Locating the weight directly over the rear axle will produce forward bite while helping to maintain steering control through the corner. Extra bracing here adds left and rear weight as well as protection.SAFETY FIRST.

 

[Ranger Mike]

Squaring chassis set up

I made this " traverse gage" a few years ago. Had 2 x 4 inch aluminum rail. I had the 12 foot rail cut into 3 sections and dovetailed for accurate fit. Had digital tape measure, height stand mounted on rollers and digital cross arm. You can really nail down the set up but for most set ups, string is going to give you enough accuracy.

 

[WN9Y]

Any basic suspension advice for a FWD class car? 1/4 mile pavement, minimal banking.

 

[Ranger Mike]

my old sportsman driver was racing at Anderson Indiana in this class. I got to catch up with him on the set up..i think he was racing a Ford compact 2300 cc 4 cyl that has an automatic in it.
The rules in these classes of racing are real limited as the point is to provide a race series as cheap as possible.
You ca not change suspension parts and are real limited on tire size and selection. no more than 1/2 inch stagger. as any racing it is all about tire contact. he runs- 1degree on lft front and up to 3 degrees + camber on rt ft.
go as sticky on the tires as you can...also he runs a real stiff RR spring to drive off the turns..
if it were me..i would bench mark the car as in previous posts to find the roll center and work at changing that height and location to your advantage.
Moving weight around to get most left side weight and as close to 50-50 front to rear weight and some good cross weight would be in order too.

 

[WN9Y]

Thanks Mike for asking. Anderson has more banks than Wall Street, but sounds like the rules are close. Not a whole lot to play with.
Have talked to a few about cross weight and have been told to go easy on it because of the push in the FWD cars. (?)
Enjoying the thread.

 

[Rebel42]

hey mike i found this site today and been reading just about all day an learning everything iv been wanting to know.. i got to question to ask.. I have a metric frame monte carlo street stock an iv been lookin to make it wider in the front by using longer lower front control arms.. is there any type of vehicle out there that has em that fits my frame? Also a couple of post back someone mentioned using impala spindals over regular monte ones.. what year impala has the 5-43/4 bolt pattern and why are they better?

 

[Ranger Mike]

WN9Y you are correct..according to "Krash" my old racer buddy, who is selling his compact and racing street stock this year...these FWD cars do tend to push so you got to drive it into the turn until you see God, then nail it. You have to drive it out of a push. total against logic we been to taught on RWD cars. Anyway it works for him.

Rebel42 welcome to the forum and thanks for the kind words..like I said..Krash is building up a street stock and i have to dig out out notes on set up. I do recall the spindle swap will change roll center height legally..same thing with the A-Arm length..

Before making a change..I would bench mark your front end even if the engine is out of the car so you can note the Roll Center and location..something the competition would not do..
there is a whole lot of monkey see monkey do in the beginner ranks without understanding what the purpose of the changes are. So before making a change..know what it will do to your set up.

rm

 

[WN9Y]

"Drive it into the turn until you see God, then nail it"
You forgot the part about closing your eyes.

Anybody on here ever bench marked a strut car? Any tips?

 

[Ranger Mike]

"Drive it into the turn until you see God, then nail it"
You forgot the part about closing your eyes.

Anybody on here ever bench marked a strut car? Any tips?

forgive me WN9..some times do not remember if I discussed this point..let me write up the bench mark process and will psot soon...

 

[Ranger Mike]

forgive me WN9..some times do not remember if I discussed this point..let me write up the bench mark process and will post soon.

 

[WN9Y]

Maybe you did, I maybe overlooked it. But, thank you in advance. It's been a fun project, looking forward to your post.

 

[Rebel42]

thanks for getting back with me, and i hope you find your old notes on what parts are interchangable for the better. are track has made some new engine rules this year, and with making are class faster i know i need to make the chassis handle more speed. we use to run 10inch wheels and that really helped, but now the inspectors have made it clear that we can only run the 8inchers.

 

[Ranger Mike]

Why change spindles? it' s all about tires. You want to maintain the most tire contact and controlling camber change is the solution. Shorter Spindles ( all else being the same) will lower the Roll Center and reduce camber change. See post 4 to 7 above and look at post 13 diagram. Please read the posts on why roll center height and location are so important in round track racing. The Impala spindles are the " hot set up " on a metric chassis. Big Chevy Impala and Caprice 1980 to 1994 casting number is 369056 for right side and 396055 for left side and if you can not locate these I can send you info on other substitutes. They are 6 pound lighter got 1 inch wide x 12 inch rotor and 5 x 5 bolt circle.

 

[Ranger Mike]

One of the most frustrating things I found in racing was shear ignorance of some people who ought to know better. The monkey see monkey do phenomena is alive and well at the short tracks and its every where. for the young racer coming up the quicker you learn this and the faster you grasp the basics , the better off you will be..to include dealing with life's frustrations..Enough of this philosophy b.s.

We bench mark a race car to establish a measurable base line. Racing is a constant adjustment process. on any given day the track will change and you have to adjust for this condition. Add in competitive changes to improve performance and you are constantly working on the set up. Races are won buy the driver and crew that can negotiate the course the fastest and FINISH ahead of the rest. When you are adjusting many things ( only one adjustment at a time is the rule...right.. like that's going to happen) you have changes things from the base line. What happens if you get punted and hit the wall and have to swap out suspension parts? Back to base line and add in adjustments you made to the point you got wrecked.

We are going to bench mark the car to measure all settings and make are record so we can make logical adjustments that will give us better performance than the other guy.
Get some white poster boards from the drug store or Wal-Mart. You will have to tape a few sheets together so you have enough area cover both front tires and frame mount points when you drop a plumb bob from the upper and lower frame mount points in the front. We are not going too deep into the suspension and will not worry about the upper and lower A-arm rear mount points.

Start with the car fueled up, tires inflated, in full race trim and it helps if you can get the neighbor hood fat kid to sit in the drivers seat while you are measuring things. In my case I got some Massey Ferguson tractor weights that equaled the drivers weight..(and some said IQ but I digress). We need to establish a vehicle center line. I use the mid point of the track width ( mid point of the tread ) and mark this on the paper.
What we are going to do is measure and record the vehicle center line. We are going to measure the length of all A-Arms from the frame mount point to the center of ball joint AS VIEWED FROM THE FRONT OF THE CAR. This length may not necessarily be the length of the A-arm. In other words the distance between these two points as intersected by a plane parallel with the floor.
We are going to measure and record the height from the floor and distance from vehicle centerline of each ball joint center, spring pad center or coil over mount point center and A-arm frame mount center point. On strut cars we have to do the same for upper and lower strut height and location , lower BJ and upper and lower spring pads if applicable. When complete we will use the Circle Track Analyzer from Performance Trends to see where the Roll Center is and go from there..More later. out of beer..

Rebel and WN9 ...i am counting on you guys to send me the data once I finish this post so we can see where things are on both your cars..send me private message if you prefer not to post..

 

[mender]

no more than 1/2 inch stagger. as any racing it is all about tire contact. he runs- 1degree on lft front and up to 3 degrees + camber on rt ft.

Is he racing in Australia?

Another thing that helps with a strut FWD car is to put in lots of caster to make up for the limited camber adjustment on most of these cars. If the driver is comfortable with trailing throttle oversteer, keep increasing the rear roll resistance until the car is only a little pushy with throttle on. Biasing the front brakes can crutch the turn-in enough to get to mid-corner where the driver can switch to throttle. Left foot braking helps.

Do the mods in that order.

 

[Ranger Mike]

excellent..This FWD racing not my strong suit..thanks Menfer

 

[WingedOver]

Nice post man! I've read all of the books you have mentioned throughout my younger years and they kind of helped push me more towards being a engineer. I'm in mechanical at la tech right now trying to balance the course load with racing a sprint car when my shop is 2 hours away! Not fun... ok maybe a little!

Anyway just wanted to commend you for the post, pretty interesting stuff here.

 

[Ranger Mike]

Welcome and thank you. There are so many high quality people contributing...a world in fact..this whole Physics forum is like having every possible experts in the world available and all you have to do is ASK... best kept secret on the internet..
look forward to hearing about your car
rm

 

[Ranger Mike]

some tips to help you bench mark the car

 

[rce4csh]

Mr. Mike, can you expand on the construction and use of your fabricated traverse bar? I. like many others, am looking to ease the whole set up procedure to effectively reduce the amount of time and effort spent on the mundane work so as to get to the "meat of the matter." Time spent messing with jackstands and strings, the neighbor's dog who came to visit adjusting your strings, back and forth on the caster/camber/turn plate deal, etc. is time that could better spent on the tiny details that make for lower lap times. More time to spend on the shock dyno, more efforts at the "what ifs" in software geometry analysis and so on.

In my mind and at my age, I am leaning toward a take down fixture with enough accuracy that it can easily be set up in the hotel parking lot, adjusted to accommodate pavement irregularities and will allow you to get the bulk of your critical squaring, caster camber, toe, bump, etc done with the suspension basically locked ( blocking, fixed links, add on fixtures. etc.) and the obstacles (tires) out of the way. Following this, the balance of scaling operations with the car reassembled. The specific details of procedure can be finalized when the details and use of traverse bar is refined.

On another note as to why this sort of thing is important; anyone here notice the drop off in interest in part time crew help? Seriously, I have noticed a strong trend in the last six years where race car help is becoming more difficult to obtain. The poor economy further fuels this problem as people who are likely to help, think twice about their out of pocket expenses in doing so. Also, the sheer number of diversions and intrusions on a person's time makes getting the appropriate amount of time spent on the race car harder to accomplish. That is why time spent here is so important. A good understanding of what to achieve coupled with refined and expedient ways to achieve them with less people power saves time for other activities needed to make things go fast...including beer, pork rhines...and the occasional romantic endeavor. The later done to maintain clear thinking and refine one's personal style!

 

[flashpuppy]

First post to the site. I have been going through this thread for about two weeks now, but I have a few questions. I'm building a little street rod and am having some trouble deciding on what to do for rear suspension. I am using a ton of circle track parts on this and wouldn't mind sticking with that style of rear suspension. The thing weighs around 1950lbs wet + 200 for me, SBC, TKO600 manual trans, Winters Quick-Change, front suspension is based off of a "Rayburn" car.

What would some of you guys be looking at and considering for this? I'm kinda leaning towards a torque-link setup right now or maybe a triangulated four-link? Thoughts? What else do you need from me?

Here's a quick pic for S&G's:

 

[Ranger Mike]

rce4csh ..the whole point of the traverse gage was to provide a quick easy to use set up to measure any changes ( via sudden impact with the 3rd turn wall, other cars etc..)
problem is it was bulky, and only measured one side at a time. I sold industrial lasers at one time in my seedy and questionable career and played with the idea of using a couple of rifle bore scope lasers to replicate the string procedure. Note attached sketch..
we need to fabricate a reference datum made 1" x 1" mild steel tubing. We have to mount this inside the cockpit as mounting it underneath the car can be a problem due to headers and the like. the mount locations could be roll bar gussets drilled to mount the stand off bars that connect to the reference bar. The reference bar would have a plate welded on each end to accept the bore scope laser block.

Bore scope Laser block - This block can be rotated and locked into position through out 360 degrees rotation. It has 4 flat sides and a small spirit level can be placed on it to level to earth. Now we have a means of doing quick chassis checks anywhere.

The mounts and blocks should be as square as possible and marked for mounting.. i.e. once you mount this make sure each time the bar is mounted the same and that way the right side laser will be on the right side..etc.

How it works- You have to string the car as described in the previous post. Place the spirit level on the block and level it. This should spot the laser on the garage floor as perpendicular as possible. This is the right side bench mark. Place a piece of masking tape there and mark the dot with a felt tip marker. Now you can spot the laser dot at the ground in front of the right front wheel at the location you have marked after using the sting method to determine the proper location. You are simply recording the distance from the bench mark to this point so you ca repeat this in the future without having to string the car.

If you really want to save time you can fabricate a " square " for each wheel which is simply a 4" x 4" block of wood trued up to square that has a center line scribed on it and is the exact height of the spindle center line or axle center line. Instead of one laser dot at the wheel location you record two or three and scribe a line on the masking tape. Then you place the " square" on the masking tape and center the scribe line of the square to the spindle center line. Now you can record the distance from the bench mark and you have your set up for that wheel.
BUT.. you are at the mercy of an unknown garage floor surface and things get squirrley when you project " squareness " from a non true surface.don't forget the car should be in race trim and same ride height. It would help greatly if you used a set of wheels and tires ( we painted our red) that was used for this. That way we knew the stagger was the same and the wheels were not bent.
I am sure the active minds on this forum will skull this out and come up with other innovative solutions...

 

[Ranger Mike]

Flashpuppy..

welcome..

i assume you have some kind of limited slip differential in the quick change..right?
coming up..rear end mounting , trailing arms etc..

 

[rick7343]

Hmmm... I typed out a lengthy post here in this forum yesterday and it said it was sent, but I don't see it anywhere...

I was looking for more info on stock rear 4 link trailing arm angles...

With stock brackets on the rearend at a 6" ride height, the lower arm runs downward to the frame mount... Better to run a higher ride height to get a level or or slightly upward angle, or can a longer bracket on the rearend help?

Can the rear end bracket be too long?

Or is it just the relationship between the upper and lower rear arms?

Affect on roll center by changing angles?

Rear roll center or center of gravity more important?

Mid banked 1/4 miles asphalt car... 3200lbs, 55%left, 50% rear, 8" towel city retreads, 13.5" crank height, 69 chevelle type chassis... Frame mounts have to be in the stock location except front uppers, we can adapt a Ford 9" so we can play there a bit...

Thanx! this forum is AWESOME!

 

[Ranger Mike]

Rick..no you are not going crazy..you sent it as private message to me..thanks..i am working on reply but need to dog into notes ..have not go chance to get er done..yet..but i will
welcome to the forum ..

rm

 

[rick7343]

DId I send you 2?

Thought I posted one and sent you message as well...

Thx...

 

[Ranger Mike]

Rear mount points and other rear end issues
read post # 253 on page 16 in this thread. for the 3 link definition


read post 132 on page 9 for the 4 link definition
read post 116 page 8 for the rear steer definition

I do not have any dimensions on the stock rear end angles and will have to check out Krash's sportsman metric chassis next time I am over there.

in general, I am opposed to raising the ride height for any reason.
if you read the post above, the 4 link lower links run slightly down hill ( 5 degrees) to the frame as you are.
I need you to clarify the rear end bracket you are describing..is it the trailing arm from rear end to frame?

Regarding the relationship between the upper and lower rear arms and effect on roll center by changing angles..
since you are severely limited by the rules there is not a whole lot you can do..BUT...there is a definite advantage by using eccentrics to adjust rear roll steer which should be legal by the rules..you may want to check this out. Personally, I believe the Roll center height and position are more important to changing the chassis performance. Rules dictate how low and how far back the engine can be. You are pretty much stuck with the 9 inch Ford rear end and its effect on CG..and earlier post noted fuel cell location. If you have reached 55 % left side and 50 % rear you just about reached the Max. as I assume you have to scale and meet this specs.
You are racing on hard tires in a very structured class. Big Horsepower is a waste since you can not hook it up on the rines you have to run on..My suggestions...run a two barrel carb, .. find the camber curve on the front and rear tires, eliminate bump steer, add in ackerman if possible, measure and understand the rear end eccentric that can crank in roll steer and use it.
note the eccentric from speedway motors..has 1/4 inch offset so...ifin you use one omn each arm you can crank in as much as 1/2 inch rear steer..don't know but if possible i would run 4..just thinking out loud.. if i could crank in an inch and really hook up..maybe a checker

 

[rick7343]

I assumed the relation fo the rear arms affected weight transfer and traction when on the throttle and brakes. What seems better for forward bite raises the rear roll center which would want to make the car loose in the corner (?). I can change these angles somewhat since I am using a 9" Ford rear and have to install mounts on it anyway...

On stock rear four links and all the 3 links at the track, the upper bar(s) are angled down toward the front of the car with lowers being close to level... Some with stock four links are running with the right rear wheel pulled ahead to combat loose conditions... seems like a bandaid...(?)

Just wondered if there were optimum angles to provide good traction and how it affect rear roll center, or would it change the rear roll center since it is high compared to the front anyway...

So the current thinking is that we want the rear of car to steer out when the body rolls in the turn?

 

[sierra76]

Having my first go at building a 3 link for dirt track racing.
Wheel base is 101 inches .
Because of tyre rules (Control Tyre) most cars find it difficult to get power down on hard slick tracks
Is there a ideal length of bottom and third links.?
should we run a third link solid or rubber/spring loaded.?
Height and position of 3 link on axle housing?
Angles of links?
Position of coil overs?
I was thinking of running rear mounted panhard mounted RHS of chassis.
Sorry for all the questions but it seems a good idea to start right fiorst time
Thanks