Race car suspension Class


by Ranger Mike
Tags: class, race, suspension
Ranger Mike
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#541
Feb11-13, 02:09 AM
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Mustngthundr...thanks you..

question- is car pushing going in and loose coming off turns?
mustngthundr
mustngthundr is offline
#542
Feb11-13, 03:21 AM
P: 7
Typically not loose on exit. From about mid- turn off its usually pretty decent unless I get held really tight to the inside, then it will get a little loose.
Ranger Mike
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#543
Feb11-13, 05:32 AM
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When we have Roll Center too far to the left of centerline, the car will not turn well. We have to load the right front tire with down force to assist the tire. See Post 251 on page 16 Body roll does not give enough leverage to stick the rt ft tire. It slides sideways thru mid corner. When we exit, there is not enough lift from the Lft Ft on to the RT Rear to add traction.
Your roll center is 10 inches to the left. You are right on with the suspension software as thsi is the tool to figure out the set up.
We must locate the RC to the right of centerline so at least half the left side mass sprung weight is rotating thru it to stick the Rt Ft. Unless you have Aero adding a lot of down force at the end of the chute, you need this to stick the rt. ft. So we run 3 to 4 inch offset to the right of centerline just for this purpose.
As a minimum relocate the RC to center...3 inch to the right is ideal. This means you will have a little more than 55% left side sprung weight wil rotate thru the RC ( on 66" track width car). This will make your set up consistant and you can fine tune from here.
mustngthundr
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#544
Feb13-13, 04:42 AM
P: 7
Ok that makes sense. I'll give it a shot. Thanks again!
NaLLa8705
NaLLa8705 is offline
#545
Feb13-13, 11:57 PM
P: 6
Hey mike!

Finishing up my race car build, found a friend with chassis software, now wondering where to measure my upper control arm pivot points so i can determine roll center. The upper control arms on my car are angled so at what point do I pick to plug into my software? Dead center?

Ranger Mike
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#546
Feb14-13, 02:50 AM
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welcome and sounds like a good plan. On all the chassis software i use, i have to measure the height and location from center line of the top outer pivot point and top inner pivot point and the software calculates the angle. The better and more accurate you measure, the better. I had to make stop blocks to jam under the lower A-arm to maintain exact height and slipped off the front tires on occassion when running wide tires and big wheel offsets masking the outer pivot point. Eventaully I borrowed a portable cmm arm.
NaLLa8705
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#547
Feb14-13, 07:34 AM
P: 6
Perhaps my question wasn't clear enough, or maybe because I haven't I looked at the software I am confused, but what I am having trouble understanding is where on the pivot do I pick the point to put in. The arm is angled like I drew up in paint.



That is in a two dimensional plane...
Ranger Mike
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#548
Feb14-13, 08:31 AM
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on circle rack analyzer use attached..i use suspension analyzer which requires 3D input
Attached Thumbnails
circle track 001.jpg  
rohitsr987
rohitsr987 is offline
#549
Feb14-13, 11:31 PM
P: 2
hi..i am building a groscope sysytem to balance two wheelrs..i need to know what is roll torque and how it can be countered?
07superstreet
07superstreet is offline
#550
Feb16-13, 01:26 PM
P: 3
Mike,
Hello, i am new to the discussion. I stumbled across this website and forum, luckily i might say, trying to find some information to help my race team. We have a stock snout, camaro frt. clip, tubular 2x3 tubing, chasis. It's been difficult getting the handling on this chasis. Before, we had a stock camaro chasis and we had figured out what it took to make that chasis work, but we were behind everyone else. They had swicthed to the chasis that we have now. With the old chasis, we would run 49-50% frt. and rear percentages. Only reason for that was that was all we could get. On this chasis, we run 55% rear percentage and 52-54% left side. The issue we are having is with ride height. We can not find anyone that can or will give us ride height numbers for this chasis. In reading all the information on this thread, i see that ride height and all related to that are very important. I know that if we can get the proper ride height, everything else will fall into place. Thank you so much for all the information you give. I have been glued to this thread since i found it.
07superstreet
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#551
Feb16-13, 01:43 PM
P: 3
Mike,
I failed to mention that this is a dirttrack car. Sorry for the omission.
Ranger Mike
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#552
Feb17-13, 02:58 AM
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welcome 07superstk and thanks for the kind words...I am not the only contributor here and we have a lot of racers on this post!.
my opinion for what its worth ...
Ride height – distance of track surface plane to four reference points of the bottom of the race car chassis. This Ride Height will allow the race car to go faster than any other height setting for a particular track. Typical ride height has 3 criteria.

1. Chassis clearance –You need enough clearance to accommodate suspension travel ( 3 inch for stock car classes paved, 4 inch for dirt) yet keep the car as low as possible without bottoming the suspension components.

2. Front camber build. As the body rolls we build camber. For every 1 inch body roll we build 1 to 1 1/2 degree camber because the bottom A-arm is longer than the top A-arm. Set the ride height and check camber build over 3 inch travel ( paved). If the camber build is over 1 1/2 degree per inch the car is too low. If the change is less than 1 degree the car is too high and I do not believe this rule of thumb. More on this later.

3. Rear Steer- We want minimum to zero rear steer at desired ride height UNLESS WE INTENTIONAL DIAL IT IN. We want rear trail arms as level to the pavement as possible. Leaf springs will most likely be slightly down hill to counter anti squat.


My opinion – I think it best to change the Roll Center Height and location with the applicable suspension components. Drop the RC to at least 2.5 inch above track surface and 3 inch offset (paved, 4 inch dirt) to the right to help plant the RF tire, reduce camber build, and reduce weight jacking effect. If you can afford it get the spindles that will give your set up minimum camber loss due to King pin Inclination angle (KIA) on the right side and max positive camber build on the left side AS YOUR SET UP REQUIRES. I like Ackermann and zero bump steer. Once you got all this you should roll steer the car at the rear to see what is happening through your suspension travel and correct to zero. Then see where things set. Pick your 4 bench mark points and permanently mark them. A grease pen is not permanent and paint grinds off is you suffer an off track experience ( get into the marbles or out in the weeds). Weld a big washer at each point. Now you got a permanent bench mark at each corner. Finally, cut a piece of 2 x 4 board the proper height to slip under each bench mark and mark them RF,LF..etc... When at the track you can use a level concrete pad and check the established ride height should you crash and need to swap out suspension parts.

Personally, I am not a great believer in ride height as much as being aware of what is happening thru suspension travel.
Chassis Rake - not so much on door slammers as Formula Cars, Rake is a setting where the front is as low as possible and the rear is an inch higher to try to channel air properly under the car. With todays disfussers and belly pans, level is good and the hiked up rear is old school and can hurt aero.
If you need specs, here they are-

Typical ride height is LF – 4”, RF – 4.5”, LR - 5”, RR, 5.5”. paved
dirt needs a little higher to gain overturning moment
LF- "5, RF - 5.5", LR -5.5" , RR - 6"
One alternative to ride height blocks is to make clearence blocks that will fit between front A-arm to chassis points and trail arm to rear end tube points on the rear. Paint large arrows at these points so you can duplicate measurements at the track.
07superstreet
07superstreet is offline
#553
Feb17-13, 04:42 PM
P: 3
Thanks Mike. Can you give me some points to make the measurements from? The stock snout is connected to the tub chasis where the rear clip bolts would be bolted to the stock camaro chasis. That is what the snout is from. A 1979-81 camaro. The 2x3 tubing chasis is that from an older Dirt Late Model. The frt. suspension is stock lower A-arms, tube upper A-arms with the mounts relocated more forward and shorter racing springs with screw jacks on top of springs. We have racing shocks all around. The rear suspension is Chrysler style multi-leaf leaf springs attached to the chasis with Sliders. We just added the Sliders this off season, so we don't know what the car will act like with them. Any advise on the best/easiest way to make the RC measurements would be great. The car doesn't have the body on it, but it does have the engine and everything else in place. Thanks again for your help and time! If anyone else is reading this that might have some helpful information, that to would be greatlt appreciated. I am trying to get away from the"good ole boy" information from the locals.
Ranger Mike
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#554
Feb18-13, 05:49 AM
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Now is the time to do all the hard work on measuring the suspension. Taek out the front coils and unhook the ARB.
Use the easy acess to record bump steer, ackermann, camber build, rear steer and the like thru at least 3 inch travel, more for dirt. Suspension bind will kill you on handling. Pay close attention to shock travel and make sure they are not rubbing at max travel. And make sure you dont have shock that limits your required suspension travel. It happens. Same with ARB (swaybar). You dont need the body on thecar to get some good scale data but you should have weight added for fuel and driver. Once you set ride height go thru the drill of cranking on the wedge bolt to see how much cross weight you gain. Record it. Your penci lis your best friend during this time.

read page 19 post 290 and the rest on benchmarking the car.
Ifin you get the Roll Center height and location close and it does not migrate all over the place, and you get close on the spring rates, you can tune in the rest at the track.
But you must bench mark the car to get there.
Ranger Mike
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#555
Feb25-13, 05:44 AM
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Couple of things about Daytona this year. First up – You can thank Nascar for making as good and safe a race as possible in spite of the bad crash that saw an engine and various components end up in the stands. Dales death was a loss but we all gained from it by efforts made to make the sport safer.

Generation 6 Car - The Car of Tomorrow (COT) has been raced for 5 years and Nascar decided to try and make the actual race car look a lot closer to the production cars. One reason - Dodge dropped out of the series, another rumor is that GM threatened to leave if the cars did not resemble production cars.. NASCAR allowed the three manufacturers to develop unique versions of the Gen-6 car. That led to cars that closely resemble the Chevrolet SS, the Ford Fusion and the Toyota Camry. Grills and body lines are similar. Silhouettes are within millimeters of their showroom counterparts. Hence the new G6 car and you saw Ford, Chevy and Toyota all show case their Nascar entry in a show room with the production model during the race.

Last year they mandated ethanol and fuel injection and that gave the engine room boys a full load. This year they decide to cut 160 pounds off the car and re-engineer the rear end package. The hope is, with less weight, Goodyear will be able to build a softer tire that will provide more grip, create more tire wear and make the cars racier while using the same chassis from the current car.

One team crew chief said the center of gravity will be off from last years set up and all new bench marks have to be established. NASCAR is doing all it can with the new car to improve handling and reduce the aerodynamic push that makes it hard to pass with the current car. The center of gravity for all these cars will be off (too) because they (NASCAR) are taking weight out of the cars: 100 pounds off the right-sides, 60 more pounds off the left-sides. The intent was to ease the load on the right rear tire.


Another significant development with the Gen-6 is the attempt to do away with “crabbing” — where the rear of the car is skewed to the right.

Crabbing was achieved by altering several rear suspension components and it improved handling by increasing down force and side force.

“Everybody did it to some degree,” Germain Racing crew chief Bootie Barker said. “Instead of having moveable bushings, you don’t have those anymore, you’re limited on your truck-arm split and you cannot run a rear sway bar (except at the road courses). Elements that went into crabbing have been taken away. Crabbing' is the long-familiar chassis trick in which cars appear rather sideways down the straights, in order to have better cornering. That's part of the trick that Rick Hendrick's teams, particularly the Jimmie Johnson-Chad Knaus team, have used so successfully.

NASCAR changed, again, the 'skew' of the rear-ends of these cars and wants basically a 'straight-up' rear-end housing. 2012 cars run rear-ends with a half-inch of toe-in on the left and a half-inch of toe-out on the right. This year 'zero toe.' means the 'crabbing' around the race track will go away.

In addition, NASCAR will be allowing teams more 'camber' in the rear-end, four degrees instead of just two degrees in an attempt to get grip back in the car. And no rear sway bars. According to one crew chief , “The rear of your car will be more 'stuck' with four degrees." Here is the wrinkle- The COT was designed for aero grip but did not look like a stock car. Todays production cars do not have the same aero grip as the COT so the G6 rear spoiler is bigger to aid rear down force. Had to since you are taking aero-grip away from the car ( G6 vs COT) and putting mechanical-grip back in the car. That's good, though Goodyear may have to make some tweaks since the changes force teams to design new drive-plates and rear axles because when you start 'bending' rear tires further, things that want to run straight don't run very well.


2013 changes include new Windshield package. The windshield frame is oriented to position the test windshields at 37° from horizontal. Both the monolithic and laminate windshields were tested. All test windshields had a single layer of Mylar tear-off applied. A steel projectile passed through the monolithic windshield but did not pass through the laminate windshield. Analysis of the high-speed video reveals that the steel projectile was traveling at 110 fps after passing through the monolithic windshield. This equates to 161.6 ft·lb (219.1 J) of kinetic energy. While the monolithic windshield allowed the projectile to pass through it, the projectile kinetic energy was reduced by more than seven times. As a result of testing, the laminate windshield is being implemented for 2013 NASCAR vehicles. FYI - Simply increasing the thickness of a single-layer monolithic polycarbonate windshield is feasible only to a point. Acceptable optical clarity becomes increasingly more difficult to achieve as material thickness increases. Secondly, as the windshield weight increases, more emphasis must be placed on windshield retention.

Other changes include a redundant Halo bar and backwards Petty bar to stiffen the roll cage.

While the wheelbase remains at 110 inches, the length of the car was reduced by 6.3 inches—from 198.5 inches to 192.2. The width also was increased by three inches—from 74 inches to 77. There were no significant changes to the height (54.2 inches) or ground clearance (3.5 inches).


http://www.nascar.com/en_us/2013-car.html
sierra76
sierra76 is offline
#556
Apr1-13, 05:24 AM
P: 5
Hi Have not been on forum for some time. Thanks for the 3 link advice Ranger Mike your set up worked really good with our car winning 7 Features in a row.
Just working on front arms and was wondering is there a ratio to the length of top to bottom. Also ideal front roll centre height for space frame 4 cylinder dirt track car . Any help would be a appreciated.
Ranger Mike
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#557
Apr1-13, 06:27 AM
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Thanks much for the kind words but we have a lot of contributors here and the credit goes to them too,,
I would not change a thing..until,,,I measured your front end setting and found out exactly where you are now with the RC height and location...
ifin it aint't broke , don't fix it...and you got 7 checkers....i really recommend you find out where you are before changing a thing..then get the software and figure out what the Roll Center migration is and where it is moving within your suspension travel...there is no ratio on upper to lower A-Arm length in a purpose built car as they all are different and unique..hence the need to benchmark a winning set up so you can come back to a base line after a crash or going off in the weeds regarding new " trick" hot set ups...

one more thing..I got a private message asking if a race car can be too light...in my opinion..no...you can never go too light ..as long as safety is maintained..in my early days we ran a roll cage set up where only the main hoop was to the required wall thickness..the other bars were “ exhaust tubing” wall thickness....dumb dumb dumb...this action was when I was always seen at tech inspection at the scales with my clip board. I would lay it on the right side of the car when we pushed it on the scales...surprising what you can do with a acetylene torch and a bunch of old wheel balance weights on a winter night...ask me about the 50 pound helmet that was an exact copy of the one our driver wore in the race and ALWAYS hung on a hook on the right side of the cockpit..left side weight rule, huh!!! ...takes practice to swap out things on the way to the scales after the feature...but that would be cheating...
Ranger Mike
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#558
Apr24-13, 05:29 AM
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200,000 views of this " race car suspension class"...wow!!

Thank you for the support over the last few years...what ever small contribution I have made here is due to the books and references I have tried to note along the way. Credit goes to those authors as well as various software programs related to chassis set up. Like I have always said..You can set up a winning race car your self..all I did was shorten the time a little...
RM


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