4 link dragster help

BillyShope · Post by **BillyShope** » Mon May 28, 2007 11:58 am

Ed, engineers don't deal with theories. We leave that sort of thing for the scientists.

This is a straightforward kinematics problem. You apply a force here and another force there and the mass reacts in a certain manner. It doesn't matter whether there is 5 horsepower involved or 50,000 horsepower, the kinematics are unchanged.

Having said that, I recognize that the final result can be affected by other factors. The "well known chassis shop" can have a customer come in with a car that's balanced like a Shriner clown parade car, for instance, and all their work is for naught. (I will fault that shop, however, for not warning the customer that his car was very poorly balanced.)

And, the parallel bar arrangement does not assure squat. As I pointed out in the previous post, it will, with the proper angle, yield neither squat nor rise (100% anti-squat). At a steeper angle, there will be rise. So, you can achieve exactly the same results (as with a conventional 4link adjustment) with the IC at an infinite distance forward from the rear axle.

I'm not familiar with the "4link Wizard." I assume this is some software that somebody's selling. The necessary information is available...for free...at Page 25 of my blog:

http://home.earthlink.net/~whshope

Bubstr · Post by **Bubstr** » Mon May 28, 2007 2:57 pm

I will put my 2 cents worth in the mix. As of Buckys last report, spring shock completely compressing and staying there. This is for sure a red flag. Unless you got that spring from a used papermate pen, you have too much squat.

I truly believe there are horses for courses, and it starts with static weight placement. Think of any car as a solid suspended car as you are putting it together. Higher H/P to weighr cars need weight farther forwaed and lower in chassis. Lower H/P to weight need weight farther back and possibly higher. Why? because we want the Low H/P car to transfer weight and the high H/P car not to blow over. The distance and hight of weight creates it's own leverage. The closer the static weight is to optimum the less we have to try to control it, relating to bigger sweet spots and less stress on parts.

Billy is absolutly right that force is applied to the instant center point. What is not constant is Center of gravity, wheel base and applied power, I say applied power because we don't always put as much as availabe to the ground till wheel speed comes up. Regulating it with slipper clutch, torque converters, and staging NOS. The difference between wheel speed and applied torque maintains traction. Not a dead hook but something called slip angle by Goodyear racing. this is the amount of slip either sideways or forward or rearward or compounds of each that a tire has it's optimum traction. Now if we are useing a 4 link (any suspension) we generaly put some anti squat in it to counter act too much weight transfer or less to promote more weight transfer ( this is usually less resistance to squat, not really inducing squat).

Now we have to be careful What we wish for, A no slip dead hook can be disasterous to drive lines and pulls RPMs below power curves, wheel stands ect.. Not the Hot set up. We need 100% of weight transfered to rear, evenly placed on both tires, but eased on to rear and not allowed to unload quickly. This is a balance of antisquat, springs, shocks and static weight placement. Next we want a tire that is optimized for weight, applied power, or optimize applied power for tire.

The base line calculators may be fine for getting a starting point, but remember as with most computers garbage in garbage out. You need to speak and understand car language, the car will always tell you what it needs It's just understanding what it's saying and what your tools are to give it what it needs. Yours is screaming , give me more anti squat right now. How much? It will tell you when it's happy, watch compression in rear. When you get close it may say I need more spring rate or stiffer compression on shock. But that is how you fine tune a chassis. Listen close and know your tools. Your tire shake is saying the same thing, the compression came so hard and fast it scrunched me up and I expanded then scrunched and couldn't stop. This sounds silly but there is a lot to be said for visualizing what your car is experiancing, and knowing what tools fix it.

WheelSpeed · Post by **WheelSpeed** » Mon May 28, 2007 7:19 pm

Good discussion. I maybe stepping a bit over my head here but I'll take a stab at this anyways.

I don't know that I agree that the car will react the same given any IC as long as it maintains a certain antisquat value. If the force applied to that(those) point(s) was the same, then yes it would be correct. However, by changing the 4 link bar locations on the housing and the chassis the force applied then changes, and with that the force that is transmitted to the vehicle. Net force over time would be the same(right?), but the instantanious forces would not. Managing those instantanious forces as they apply to the tire is what gets the max amount of acceleration for a given tire/track condition(co.ef. of friction).

Ed, Just curious who you were hearing those #s for the NHRA Pro Stockers from?? Last I heard, rear %' s were in the 46-47 range(maybe less now?) and most ICs were in the mid to upper 50s at between 6" and 7"s(6 being in the mid, 7 being in the upper).

Back to the original question. That shock graph is like none I have ever seen before. By the shape of it it almost looks like that data is being displayed opposite from how it should be(ext showing comp & viceversa).

BillyShope · Post by **BillyShope** » Mon May 28, 2007 7:32 pm

I should have elaborated on that which chassis shops should do before wasting a lot of time (and the customer's money) on chassis adjustments. Assuming the use of good slicks, if the answer, when the product of 2.5 times the total weight times the CG height is divided by the wheelbase, is greater than the static weight on the front wheels, the customer should be warned that he needs to shift weight forward or excessive wheelstands could make the adjustments worthless.

Transman · Post by **Transman** » Mon May 28, 2007 8:46 pm

If you have the proper torque converter it will not run slow dead-hooking it. But, many Comp/PS style cars will have some wheel spin leaving the line. As long as you have the right converter to deal with a rapid climb in pump (engine) speed so you don't drive into premature lockup (as much as possible that is...) of the converter, it is fine as long as it repeats.

Ed-vancedEngines · Post by **Ed-vancedEngines** » Tue May 29, 2007 6:33 am

Ed, Just curious who you were hearing those #s for the NHRA Pro Stockers from?? Last I heard, rear %' s were in the 46-47 range(maybe less now?) and most ICs were in the mid to upper 50s at between 6" and 7"s(6 being in the mid, 7 being in the upper).

That info came to me equally from both Rick Jones and from Jerry Bickel while we were in conversation about another issue of side to side weight distribution, we were not discussiong IC we were discussiiong effects of weight distribution as it is now considered as opposed to things the industry was doing years agao to make all attempts to pre-laod the cars as they were built back then. Back then it was common to move the engines and drivetrains considerably to the passanger side to build right rear weight into the car and then to better equalize the left to right weights completeing the rear by spring and bar pre-loads which of course shifted the previously built in weight bias on the right front onto the left front as the weight was jacked to the right rear. That is all old school endeavours now and now the atual side to side rear weights are not the strong considerations they used to be if they are within 75 # of each other. It is the front to rear bias that is important to keep at near 50% - 50% . That was in essence their words in the way I understood it. I will of course agree with you that many of the guys are still hanging weight on the front, when the bars and shocks are close.

Mr Billy;
I am in pretty much agreement with this statement from you.

when the product of 2.5 times the total weight times the CG height is divided by the wheelbase, is greater than the static weight on the front wheels, the customer should be warned that he needs to shift weight forward or excessive wheelstands could make the adjustments worthless.

Still varaibles can and will apply. I lived with this problem first hand years ago in my own car which in my stupidity I built in too much rear weight bias. It was a handful until I found the magic buttons to tame it down. It get get tamed down though with the changing of bar angles, bar spreads and totally assanine Instant Centers.

That little Vid ot Tony's Tiger Car is showing the effets of a front biased car of 52% with too long and too high of an IC, if you looked at it. I have not yet touched that suspension. So far it has been done by two different high rolling shops in Houston. Before this radical change it was with a lower but still high IC and a short iC which resulted in severe Dead Hook, which broke just about everything it could. For the guy that said a Dead Hook is ok, I strongly disagree. You need some wheel speed in these cars. When it was adjusted wrong enough to dead hook it suceded in busting Pro Teflon Heim Joints, Anti-Roll bar and two sets of wheelie bars it hit them so hard. So the brains at a well known chassis shop solved his dead hook by moving the bottom bar up one hole in front and the front of top bar up two holes. The result you can see in the vid.

Billy, I raed your words and in the reading they do make sense but in the real world it does not work that way. A car that is working pefect with a certain suspension setting absolutely will not be working perfect when you radically increase the power levels. I will go even further, hen you increase the power levels, not only will a different adjustment be needed the rear pre-laod will need to be changed too.

Possibly a car with 4-Link Bars in complete parellel with each other and the bar spread in the rear of equal mounting locations top and bottom from axle center May react the same no matter what the power level is. I say possibly becuase there is no way I would even think about trying it, but there are those that do try it in other forms of vehicle use for driving. That is the way a typical Street Rod 4- Bar suspension is configured. That is for ride and handling not for any traction enhancing.

Take the factory GM Triangulated 4- Link suspension for example. tHAT HAS ic ALMOST TO THE INFINITY OR AT LEAST THOUSANDS OF FEET IN FRONT OF THE CAR. (Caps lock) . The IC is moderately High but is very very long. Those cars will squat when torque is applied to the rear tires. Those cars will actually show a lifting force on the rear axle when torque is applied to the suspension and in factory condition do little for traction. Now if you raise the Rear of top bar by increasing top bar spread from axle center, Like with a Mr. Gasket No-Hop bar set, Those cars will hit the tires so hard they need heavier shocks to control the suspension action you all want to call anti-squat. Before they exhibited tons of squat. Moving one rear bar position to now give the car a sligtly lower, by not much, but a severely shorter IC results in more traction than we can use. When the bars had an IC to the infinity the car would not hook. Move the IC back and it hooks big time.

You are an engineer so for you a finding is called an Engineering fact. Yet all the time in our world new unconsidered environments arise or are discovered that do change the results of the Engineering Facts unless the engineer updates his material which was used to arrive at the now obsolete facts.

Like the example I grew up with and I know that you did too. Engineering fact is that it is impossible for any vehicle to be able to accellerate in the 1/4 mile at a rate in excess of that to equal a top speed of 168 mph.

I do wish that you could get your feet wet once aagain and be involved in modern day high horsepower drag racing, and see that new formulas or fresh data is now out there in this arena of interest. You did wonders in getting those old Super/Stockers to hook on a 7 inch tire. I'll bet you could likely do much in today's racing if you were closely involved and could see and could test for rsults of what happens if. Can you understand that we amateur racers are now putting more power to the track with smaller tires than the professionals are. Of course there must still be something better.

Ed

Bucky1 · Post by **Bucky1** » Tue May 29, 2007 7:33 am

Nicely done not belittling anyone.

Yes, the CG of the car is about 30" behind my 101" centerline.

Yes, the IC can move like I mentioned, because the holes in the housing are spaced further apart then the holes in the front. The bottom bar will have less downward angle with the change. It is a rear engine dragster with a small block, not a high horsepower car.

Ed, I think that you have a great deal to add, but sorting through all the ranting and insults makes it pretty hard to get to. I always appreciate a post that intends to help, but in reading your posts, I'm not sure what your intentions are. I did get an ounce of information about springs and IC's, but otherwise I was told how I am not talking the way I should, the settings that I have come up with are absurd, experts that use the termanology that I use don't know what they are doing, and a lot of comparisons with huge horsepower cars. I don't know how you can think all of that is helpful.

Last season I tried just about every IC setting that did not result in squat, and every tire pressure and shock setting. The car always hooks and then unhooks. This long IC may not be ideal in your book, but the unhook has vastly improved. I have gone from a car that just didn't work very well to at least being in the ballpark. I don't know how wrong that can be.

I respect your knowledge Ed. Your bedside manner leaves something to be desired.

Ed-vancedEngines · Post by **Ed-vancedEngines** » Tue May 29, 2007 8:14 am

not belittling anyone.

I gues that this is not all that belittling but I will call it instructional criticism towrd me. Thanks. I needed that.

Ed, I think that you have a great deal to add, but sorting through all the ranting and insults makes it pretty hard to get to. I always appreciate a post that intends to help, but in reading your posts, I'm not sure what your intentions are. I did get an ounce of information about springs and IC's, but otherwise I was told how I am not talking the way I should, the settings that I have come up with are absurd, experts that use the termanology that I use don't know what they are doing, and a lot of comparisons with huge horsepower cars. I don't know how you can think all of that is helpful.

You may not have a high horsepowered car but I'll bet that you have a high horsepower to weight ratio as compared to the many examples we all think of.

I think that Billy Shope should know me and my rantings by now. In a wierd sort of way I consider him to be an unknown long distance friend. We do not agree a whole lot about things in modern drag cars but we do at times find mutual ares of agreement. IT was guys like Mr. Billy Shope, that got us all on a path of doing and thinking about the what-ifs a long time ago. Far back when cars could just not accelerate any quicker with suspensions He was very instrumental in proving it could be done. It was he, by my informational sources that got well above 600 hp to hook on a tire 7 inches wide. I do have great admiration for him, but that is not meaning I can agree with him all the time. Shoot I seldom find anyone to agree with me all the time about anything, make that seldom into never. lol.

Sorry about the very few words concerning the usage of Squat and Anti-Squat. It still sounds to me like someone getting ready to take a crap. I am too old, these terms are fairly new and are now used a lot. At least I can understand what you and others mean when you use them. In the older days Those terms were never used in drag race chassis tuning or building and we all were talking on the same pages when we talked on the phone. If used correctly now it is meaning the body goes down over the tires more or the shock is compressing when you say Squat and Anti-Squat should mean that the shock is extenting or the body is separating from the tires. It is just a peeve of mine I have had since my first Alston Chasis Clinic and I see it in Dave Moragn's too.

I think that for your benefit and for my beneft I will further stay out of this thread becuase my experiences with real cars of all horsepower ranges means zilch when compared to a computer program or my friend Billy. 101 IC. I still say is outrageous though. I think you would have had better results by moving your IC down and not as far forward. How far down can it be moved? As far down as necessary to get results. If you have still enough power to overcome the long IC, I will bet that thing is wanting to lift the front more than before too. By moving the IC forward you too the anti-squat from the rear tires as much. You would have also done that by moving the IC downward.

Yep,
Not much bedside manner, but I won;'t be sleeping with any of you is my hope.

Ed

Bucky1 · Post by **Bucky1** » Tue May 29, 2007 9:41 am

Ed,
Thanks for the additional input. I was probably too harsh this morning. I am beginning to see your humor too. The last thing I want to be is ungreatful, and that is what I was. My bad.

Cammer · Post by **Cammer** » Tue May 29, 2007 9:48 am

I will speak for the engineers out there.

Engineers do not work in an environment where everything is set in stone.

Many mechanisms such as engines change into basically "living" devices during operation. It is impossible to perfectly figure what goes on in a running engine! New innovations such as CFD promise to help engineers in their work.

Engineers commonly write deviations and engineering changes on parts that do not work as designed.

An engineer is a scientist.

______________________

Ed-vancedEngines · Post by **Ed-vancedEngines** » Tue May 29, 2007 10:27 am

I will add to this also.

I do think the world of Mr. Billy Shope. Don't anyone believe otherwise. I hope that by now Mr Billy does not think I try to cut him down simply becuase we are not fully in agreement.

Thank you,

Bucky,
I hope it all works out for you. I do not ever intend to be mean. That is not me, It is not what I am about.

I will suggest you can go to racing junk . com and in the chassis section is a 18 or 19 page article written by me about this subject. Maybe you can get something out of it or not. I also suggest to go to the webpage of Mr. Billy that he supplied the link to and to read his words on this subject. By reding both of our writings you can really end up scratching your head or you can actually find some common agreements in them.

For what it is wrth I have experienced the chnges of making changes in a car with heavy rear weight bias of 55% on the rear. I ended up with a IC buried into the ground. lol. really that is what worked best in that car.

Ed

BillyShope · Post by **BillyShope** » Tue May 29, 2007 11:14 am

Cammer wrote:
An engineer is a scientist.

______________________

Sorry, but I do not consider myself a scientist.

I realize there are those who call engineers those who practice "applied science." These same people refer to true scientists as those who practice "pure science."

Conversely, scientists could be referred to as those who practice "abstract engineering" and engineers could be referred to as those who practice "practical engineering."

I suspect that many somehow believe the title "scientist" carries more prestige than "engineer." I really don't know why. It's apples and oranges.

Those scientists involved in the Manhattan Project immediately became engineers when they started the development of a thermonuclear device. In this case, of course, it was expedient to do so for project time was critical. I suspect, however, that many aspects of the project were delayed because these men and women were unfamiliar with sound engineering practice.

Bucky1 · Post by **Bucky1** » Tue May 29, 2007 1:48 pm

It's all good. As an engineer myself, it's frustrating when you don't have enough real world data (experience) with a particular combination to know which way to go. I tried a lot of combinations in the areas where many had pointed me, and they just didn't work for my car. When I finally told myself that I don't know what I don't know, and tried something out of the area that generally was excepted as the way to go, is when I finally made some progress. I really think that 4 link dragsters are still a little theory, a little art, and a lot of experimenting. Until the experience on different combos starts really getting up there, there just isn't enough reference data to use.

John Wallace · Post by **John Wallace** » Tue May 29, 2007 9:07 pm

On a solid mounted rear end in a rear engined dragster, is there a way of figuring IC?

Or said another way, is there a way to make it hook better since there is no adjustments?

BillyShope · Post by **BillyShope** » Tue May 29, 2007 10:07 pm

John Wallace wrote:On a solid mounted rear end in a rear engined dragster, is there a way of figuring IC?

Or said another way, is there a way to make it hook better since there is no adjustments?

Glad you asked! Yes, there is definitely a means of improving such a setup. As you've noticed, even a suspensionless dragster will often lift the left front before the right. The same torque that's lifting the left front is acting at the rear to cause unequal loading and, consequently, less than maximum forward thrust.

What is needed is some "droop" in the left front. In other words, when a floor jack is located centrally in the front and the front lifted, the left front should droop below that of the right front. With the proper amount of droop, the rear tires can be a whole lot closer to equal loading on launch.

To determine how much droop, you need to use a traction dyno. For an explanation of the setup required, see my blog:

http://home.earthlink.net/~whshope