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Re: Caltracs Versus Triangulated system from Unlawfuls
[Re: Kiddart]
#494986
10/17/09 06:58 PM
10/17/09 06:58 PM
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Joined: Jan 2005
Posts: 3,635
Oakland, MI
dizuster
master
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master
Joined: Jan 2005
Posts: 3,635
Oakland, MI
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Wow, I started this post as a simple, Cal-Tracks DO NOT change the IC. But it obviously became much more. Hopefully this helps explain things further. As for the Cal-Track changing IC issue. The thing that I think is being missed is the fact that all of the forces still go through one single point (per side) on a cal-track. Concider this. If you made the lower portion of a ladder bar bolt to the upper bar in an adjustible fashion, would you be changing the IC? No of course not. It would just be an adjustible brace on a ladder bar. The IC is defined as a central point (actual or theoretical) where the forces are applied on the chassis. With one single point of rotation on a spring/cal-track, any modifications you do to that spring, or behind that point of attachment have no effect on the IC. Cal-tracks appear to have the same type of adjustment as a 4-link, but the difference is that the 4-link applies the force of both bars directly to the chassis, while the forces from the adjusted caltracks still go through the same single front spring bolt regardless of bar location. Hope that clears that up. As for "squat". Body rotation happens because of two distinctly different reasons. 1) The first reason has absolutely nothing to do with suspension points, 4-links, cal-tracks, or any of the like. The first one is basic physics. As the car accelerates, there is a weight shift from front to rear. This is because of inertia. The car's mass resists the acceleration. If you remember your old high school science. "An object in motion tends to stay in motion. An object at rest, tends to stay at rest." Because of this "wanting to stay at rest" there is weight shifted to the rear tires. You can all feel this when you launch your cars. That force you feel during launch on your body, is your body weight being applied towards the rear of the car. You can easily "feel" how weight is being transfered to the rear tires. This doesn't mean that the weight of the car is changing, it's just moving from front to rear. Now because all of our cars have springs, that newly added weight on the rear causes the rear spring to compress more. At the same time, there is now less weight on the front, which causes the front spring to expand. Front up, rear down = rotation. No different then putting a load of sand in your truck. Added weight causes squat. In this case, it just came from the acceleration weight transfer. 2) The second thing that causes body rotation, DOES have everything to do with suspension set up. For one minute forget everything you know about suspensions, IC's, Anti-squat lines, etc... First things first. C.G. is center of gravity. This means that if your car was flying through space, it would rotate around this center point. An easy example is when you throw a frisbee. Throw it right handed, left handed, underhanded, etc... any way you throw it, it always spins around it's center. The same principal applies to a car. It always wants to rotate around it's center of gravity. A simple thing you can do to understand how the location of force (chassis setup) effects rotation is this... Take a pencil, pen, marker, wooden dowel, etc.. anything like that you have, and stand it on it's end on the table. Now this pencil, pen, marker, whatever you have, has a center of gravity right at it's center point (easy to visualize on an object like this.) Now if you take your finger, and "flick" it right at the base where it meets the table, what happens? The pencil rotates, but doesn't move forward very far. Now set the pencil up again, and "flick" it right at it's center point (vertically). what happens? The pencil fly's forward, but with little rotation. This is an easy way to "visualize" how changing the point where the suspension acts on the car causes body rotation. Apply the force low, and the body will rotate rearward (squat in the rear), apply the force up high, and the body will rotate forward (rise in the rear). Now applying these forces through suspension, shocks, and a CG that moves with acceleration (because of weight shift) is a MUCH more complicated situation. But hopefully this gives a simple explination of what's going on during the launch. Now, just because I understand what's happening during the launch, does not mean I know how to adjust suspensions! That's where someone like Monte comes in. This is one area where all of the math and engineering in the world, can't touch "been there, done that." I for one am grateful to see guys like Monte chime in with experience. 
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Re: Caltracs Versus Triangulated system from Unlawfuls
[Re: dizuster]
#494987
10/17/09 08:47 PM
10/17/09 08:47 PM
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Joined: Nov 2007
Posts: 439
Ortonville, MI
StyleElements
mopar
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mopar
Joined: Nov 2007
Posts: 439
Ortonville, MI
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Quote:
Wow, I started this post as a simple, Cal-Tracks DO NOT change the IC. But it obviously became much more. Hopefully this helps explain things further.
Hey there neighbor
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Re: Caltracs Versus Triangulated system from Unlawfuls
[Re: StyleElements]
#494988
10/17/09 09:24 PM
10/17/09 09:24 PM
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Joined: Jan 2003
Posts: 6,591
Canton, Ohio
Sport440
master
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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Quote:
Quote:
Wow, I started this post as a simple, Cal-Tracks DO NOT change the IC. But it obviously became much more. Hopefully this helps explain things further.
Hey there neighbor
  mike
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Re: Caltracs Versus Triangulated system from Unlawfuls
[Re: justinp61]
#494990
10/19/09 01:17 AM
10/19/09 01:17 AM
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Joined: Nov 2004
Posts: 6,890
North Alabama
Monte_Smith
master
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master
Joined: Nov 2004
Posts: 6,890
North Alabama
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Quote:
Quote:
WOW..... this is really deep... squate this, dampen that... it makes me dizzy
Now which suspension system is best for stopping my head from spinning?
Dallas
If you find it PM me  . I can see what Monty is saying about the pivot on the Cal-Tracs and the IC not changing. But, how does the IC change on a four link? The bars are only moving up and down, the mounting point is not moving, it's welded in the car. It all seems to be theory to me. The Cal-Tracs have a single mounting point but so does the four link, the spring eye for the Cal-Trac and the front bracket on the four link.
I'm probably way out in left field on this and by no means an expert. Oh, I have Cal-Tracs on my pig .
This the kind of thread I like to read, hopefully I can learn something  .
The 4 link, with lots of adjustment holes, can have 1,000 possible ICs with all the different holes on the housing and chassis brackets. The IC is where the two bars would cross, if you extended them. So the IC is projected, not physically mounted. A leaf spring, or ladder bar, the IC is where it is mounted to the chassis, period, it can be nowhere else. Now multiple mounting holes, can move the IC up or down, but the length is common, because it is a one piece, fixed bar, attached to the chassis. So a 32" ladder bar, has a "32 out" IC center. As said the height can vary with mounting holes, but the length will ALWAYS be 32". The IC of a leaf spring, is out as far, as the front segment is long. As far as the front mounting point of a CalTrac, lower bar, altering the IC, it can't, because the pivot point on the chassis never changes. All that adjustment does, is change the amount of leverage, that the spring, applies to the chassis. Just take some time and actually look at your CalTrac bars, visualize what happens as the rear tries to seperate from the car and the pinion rolls up. You will more understand how the adjustments change the way the force is applied to the spring pocket.
Monte
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Re: Caltracs Versus Triangulated system from Unlawfuls
#494992
10/19/09 05:44 PM
10/19/09 05:44 PM
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Joined: Jan 2004
Posts: 4,866
North of Detroit
HemiDart68
master
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master
Joined: Jan 2004
Posts: 4,866
North of Detroit
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Quote:
For background purposes, my drag car is a 1963 Plymouth Savoy set up with Cal Tracs, monoleaf springs, sliders in place of conventional shackles and AFCO double adjustable shocks. Lower bar is mounted in the bottom hole. Pinion angle is 4 degrees. Front suspension is six cylinder torsion bars, double adjustable AFCO shocks and suspension limiters to control suspension travel. Car weight with driver is approximately 3650 pounds with a 50/50 weight distribution. Engine is 572 CID, 727 with 2.28 1st gear to soften launch, Dana 60 with 4.30 gears and MT 31x15x10.5W tires. I have 100 pounds mounted over the rear axle with a 20 weight bar mounted under the radiator.
Best 60 foot time to date was 1.29, 9.09 ET / 148 MPH at Milan Dragway. Three passes were made back-to-back with the same results.
While this may have been the exception, 60' times are typically in the 1.31 to 1.33 range with Gary Jacobs/Jakes Automotive driving. Car launches at 1800 RPM, no brake
I'm a firm believer in this system as demonstrated by the cars performance to date. I take a total system approach considering both front and rear suspension. One consideration is adjustability in terms of shock package and front suspension travel and initial set-up using scales.
I will agree that the shocks were expensive, however, considering the total cost, much less expensive than a ladder bar or 4 link set-up.
It can be done.
I've included some websites. I hope you can access since I'm new to this. If you cannot access directly, type into Google and see what happens.
Thanks.
http://www.racefab-asi.com/gallery9.html
http://www.youtube.com/watch?v=vOLyjoARDII
Well Len since this your first Moparts post, im going to take it as an opportunity to bust your balls if you dont mind.
I think one of the key reasons why you have alot more success with a Caltrac car then most, is the fact that it is a 50/50 car. My car when i ran them was 55/45 and I had mixed results. Personally i was a happier camper changing over to ladder bars. I probably could have spent more time working with the caltracs, but it seemed like it costs $500 every time I went out, so i figured one or two wasted trips paid for my ladder bars, which worked on the first hit.
Look at our buddy Mr. Jiles car. There is a reason why this car leaves like this with no caltracs, just leafs and little tires. its all Weight distribution.
In God we trust, all others pay cash.
www.lightnens.com (Home of the world's fastest Paint Job)
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Re: Caltracs Versus Triangulated system from Unlawfuls
[Re: HerboldRacing]
#494994
10/24/09 08:35 AM
10/24/09 08:35 AM
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Joined: Mar 2008
Posts: 1,596
BX, CT, FL.
B1KILLER
pro stock
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pro stock
Joined: Mar 2008
Posts: 1,596
BX, CT, FL.
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Here a video of my car, with a 10/28" slick, @ track rental, going 9.50 @ 139mph, all motor pass. http://www.youtube.com/watch?v=wTupJMuG3WoCar also hooks on juice going allot faster   All this with simple mono leaf, Rancho 9 way adj, go figure 
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Re: Caltracs Versus Triangulated system from Unlawfuls
[Re: Monte_Smith]
#494996
10/24/09 02:23 PM
10/24/09 02:23 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Why wouldn't the cal impose a different mounting position though? As the suspension rotates, the top of the cal track mount hits the leaf, at which point it behaves like a solid piece of steel mounted at the spring hole position, and the position where it hits the leaf,more motion is constrained by the interference with the leaf.
As a result, it acts as though it were a solid piece, which should allow it to behave like a geometry defining link. It's motion is more complex though, as it relies on the leaf to present the mounting point for the bracket, and while it clearly hits the leaf and thus defines a new link, the leaf still has some movement, and as a result the ic isn't as solidly defined as it would be if the cal track mount were actually welded to the frame.
(not saying that should be done, just pointing out how the motion of the bracket, though constrained, isn't quite fixed. Also, this is an order of magnitude thing, the motion is hardly unlivable. After all, the chassis is trying to squat, so the leaf is trying to lengthen, which means the leaf is pushing against the bracket, not pulling away from it.)
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Re: Caltracs Versus Triangulated system from Unlawfuls
#494997
10/24/09 03:40 PM
10/24/09 03:40 PM
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Joined: Dec 2008
Posts: 127
Phoenix, Arizona
HerboldRacing
member
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member
Joined: Dec 2008
Posts: 127
Phoenix, Arizona
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Quote:
Why wouldn't the cal impose a different mounting position though? As the suspension rotates, the top of the cal track mount hits the leaf, at which point it behaves like a solid piece of steel mounted at the spring hole position, and the position where it hits the leaf,more motion is constrained by the interference with the leaf.
As a result, it acts as though it were a solid piece, which should allow it to behave like a geometry defining link. It's motion is more complex though, as it relies on the leaf to present the mounting point for the bracket, and while it clearly hits the leaf and thus defines a new link, the leaf still has some movement, and as a result the ic isn't as solidly defined as it would be if the cal track mount were actually welded to the frame.
(not saying that should be done, just pointing out how the motion of the bracket, though constrained, isn't quite fixed. Also, this is an order of magnitude thing, the motion is hardly unlivable. After all, the chassis is trying to squat, so the leaf is trying to lengthen, which means the leaf is pushing against the bracket, not pulling away from it.)
My experience with rigid body computer simulation agrees with this.
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Re: Caltracs Versus Triangulated system from Unlawfuls
#494998
10/24/09 03:57 PM
10/24/09 03:57 PM
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Joined: Jan 2005
Posts: 3,635
Oakland, MI
dizuster
master
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master
Joined: Jan 2005
Posts: 3,635
Oakland, MI
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You are correct, the bracket does change the way the spring reacts. However, keep in mind, the resultant force vector is still applied through the body at a single point (the front spring eye bolt).
I see what you're trying to say though. I believe you're thinking that effectivly, the point of rotation becomes the contact between the spring and the upper rear cal-track pin. The spring does effectively become shorter (thus stiffer), but just like a ladder bar, even if it didn't flex at all, the effective point is still the free rotation point (front bolt).
Remeber the front bolt is a pivot, so it can not impose any moment (torque). It can only impose the x and y forces...
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Re: Caltracs Versus Triangulated system from Unlawfuls
[Re: dizuster]
#495000
10/26/09 04:22 PM
10/26/09 04:22 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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When you step on the gas, the stopper comes down on the leaf coming up. As a result, there are now two points at which the bracket is mounted, the forward point at the leaf spring pivot, and the point four inches back pushing down as the spring pushes up.
the spring doesn't just bend out of the way, because the chassis is trying to get it to come up (as a result of the leaf twisting due to the axle torque) so you end up with the downward force of the bracket canceling on the upward force of the spring. the front bolt essentially now has a rigid beam four inches(or whatever length they are) long to the back stop. The forces cancel(more or less) and you get a beam, to which the bracket is mounted, which in turn provides the revised IC.
Finally, while the front bolt is a pivot, the spring itself is not, it's bound by the front pivot as well as the rear shackle.
This is easier to visualise if you forget about the spring behind the axle, and think of a bar connecting from front eye to axle,leaving the axle free to rotate.Now you can see that the stopper can't just push on the front eye and pivot, it has to push on the tire and lift the chassis to do so.
so you can push down on the stopper and as a result push up on the whole chassis. Which is why the stopper on the cal track works.
From what I've found in discussion with others, the resultant IC should be at the intersection point of the Cal Tracs side view swing arm and the axle centerlines virtual arm.
Making it much like a four link in terms of IC projection.
Though unlike a four link, as the suspension moves, the IC won't move around like a four links would, but instead would move in relation to the motion of the front spring eye angle.
As a side note, based on this I see that you'd need springs that will deflect enough to work with these. Leaves with a forward spring pack would prevent the suspension from winding enough to engage the cal track. though you could always crank the preload way up I suppose.
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Re: Caltracs Versus Triangulated system from Unlawfuls
[Re: Sport440]
#495002
10/26/09 11:14 PM
10/26/09 11:14 PM
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Joined: Nov 2004
Posts: 6,890
North Alabama
Monte_Smith
master
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master
Joined: Nov 2004
Posts: 6,890
North Alabama
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Quote:
I gave this alot of thought! IMO the Caltrac design does indeed change the IC even with the single point front spring mount. For the reasons already stated by me in my posts and the reasons stated above on both of acex,s post.
Simply put! From the Two/three points of contact from the Caltrac front lever. Its more then just a Leverage thing. mike
Sorry...the leaf spring applies the force to the chassis in ONE place and ONE place ONLY. That place is the instant center. You don't move the pivot point, you don't move the IC. Moving the Caltrac bar up or down, simply changes the amount of force placed on the pivot bracket. Simple physics.
Monte
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Re: Caltracs Versus Triangulated system from Unlawfuls
[Re: Monte_Smith]
#495003
10/27/09 01:24 AM
10/27/09 01:24 AM
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Joined: Jan 2005
Posts: 3,699
Newport, Mi
Evil Spirit
master
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master
Joined: Jan 2005
Posts: 3,699
Newport, Mi
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Quote:
Quote:
I gave this alot of thought! IMO the Caltrac design does indeed change the IC even with the single point front spring mount. For the reasons already stated by me in my posts and the reasons stated above on both of acex,s post.
Simply put! From the Two/three points of contact from the Caltrac front lever. Its more then just a Leverage thing. mike
Sorry...the leaf spring applies the force to the chassis in ONE place and ONE place ONLY. That place is the instant center. You don't move the pivot point, you don't move the IC. Moving the Caltrac bar up or down, simply changes the amount of force placed on the pivot bracket. Simple physics.
Monte
Yep. The Caltracs work well to preload one side or the other to make a car go straighter, which helps 60' - same as shimming the snubbers on a set of slapper bars. You can also "stiffen" the front of the spring to help keep the car from squatting, which is actually the axle being lifted off the pavement. Changing the height of the rear of the bar only changes the leverage that the pivot can apply, not the I/C. To change the I/C you need to raise/lower the front of the leaf springs mounting point.
Free advice and worth every penny...
Factory trained Slinky rewinder.........
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Re: Caltracs Versus Triangulated system from Unlawfuls
[Re: Monte_Smith]
#495004
10/27/09 03:12 AM
10/27/09 03:12 AM
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Anonymous
Unregistered
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Anonymous
Unregistered
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ICs aren't fixed in motion, that's why they're instant centers. IC can be derived using devices which only operate in a certain suspension mode. Decoupled torque arms come to mind. IC doesn't define a solid point regardless of motion, it only defines the point at some particular instant.
IOW, at the instant the Cal Tracs engage IC can be derived by the system for just the point at which they are engaged.
A/S (Which is what most look for by moving IC) Can be exactly 100%, which completely binds the system, no suspension movement at all. If it relied on the motion of pivot points to work, than the bound suspension wouldn't have IC at all. That is what occurs under A/S after all, it's the chassis exerting force through suspension geometry instead of through the springs. It happens before the suspension moves.
If you've done front suspension you'd know it as Roll Center. But whereas a roll center near to cg on is undesirable, it's used on the rear as a/s because:
If there is a rate of change in acceleration (Not just 1g, but going from 0 to 1g) some of the force applied through the links can actually be exerted downward on the tires. That's why A/S provides that initial bite. With a large rate of change in acceleration there is also a large downward force on the tires. The trade off being that suspension compliance under accel goes out the window, as the system is in bind.
And again, the leaf only applies force through one point, but with it bound as it is by the Cal trac stopper it makes an excellent place mount another momentary pivot, Which is the cal trac.
Last edited by acexp2; 10/27/09 03:37 AM.
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I'll re-read it tomorrow 
