Old school leaf spring traction devices vs Cal Tracs

[af2]

Lowering blocks and de/re arching springs and shackle lengths will merely change the ride height of the rear of the car and therefore the Center of Gravity only.
Clear as Mud?

Ok when ride hight is changed, the elevation of your front mounting point is also changed. as your rear end does not change, it has to change both the center of gravity and the instant center. The changing of ride hight is great for small adjustments even on ladder bars or 4 links in between holes.

I guess the part that stumps me is all force is applied to the front mounting point, no matter what bells and whistles. Now if we where to say that as it cut down spring wrap up it increased front half spring rate to help any anti squat that was present. I might be able to understand that. I keep thinking of the monkey that rides the bicycle on the tight rope with a big bird suspended below on a curved half circle perch. no matter how big the bird or what shape the perch the force is always straight down. It's impossible for the monkey to fall over because there is only one point of force. I guess that is the source of my mud.[/quote]


Ok. I might get pounded on this one! There is no center of gravity change with a leaf spring. I don't care what bar you run. It has to do with the front spring eye. I have run Al's bars which is very different and efficient at taking the load off the rear and transferring to the front of the car. There are 2 pivot points doing this. #1 the bar location and #2 the pivot point on the cross member holding the bar. Which is free to swing to make up the short and long squat and rise on acceleration.
It is like a ladder bar with 1 more pivot point. It works as the #1 C/Gas car used it for the last 10 years. I am not trying to sell it but letting you know there is more out there!

[Larry Woodfin]

I completely understand a person being unclear about the Calvert concept. However, if you install a set and race with that set, the resulting experience will clear up how it works.

In order to "visualize" the operation, "imaginary" lines have to be draw as explained in an above post. Do not be locked into thinking all force is being focused at the front spring eye, that is not the case. The lower bar has an imaginary intersect point that reacts with force from the spring eye mount.

The car truly thinks it has a four link. When you get the opportunity, watch some well prepped NHRA stockers run. Then compare them to the chassis action of a super stocker with a four link. You will notice that each class of car makes a similar move away from the line. The super stocker of course having more power, but you will notice the trend.

[cpmotors]

Let me clear up my previous statement of raising or lowering the rear end moves the Center of Gravity. What I meant to state is the LOAD is shifted.
By definition the C/G is the perfect balance point of the mass of the vehicle.
The only way to change the C/G is to remove, add, or shift mass to another position.
The raising or lowering of the ride height of a ladder bar or leaf spring car will change the resultant vector(by resultant vector,I am refering to the angle from the tire contact patch thru the I/C, and where it is applying force in relation to the C/G) but the instant center is still the same, as it is a fixed location the rear suspension rotates around.
On a four link, ride height adjustments change the I/C because the lower and upper bars are different lengths, with different arcs, changing the point of intersection, or I/C.
For a clearer picture and fascinating reading, Dave Morgans book goes along way to explain the physics of it all. Pages 24-28 apply to this discussion pretty well.
af2, who is Al and are his bars for leaf spring cars?

[af2]

af2, who is Al and are his bars for leaf spring cars?

Al's Automotive.
He started building the bars in 1962. As of today he is working on a 56 Ford he built 40 years ago with lift bars and a straight axle in front. He is putting a ZZ502 in it.

They work the best with leaf springs. The C/Gas car runs coil over and is dead consistent on 60's(till the slicks need replaced)

The guys in the Bay area know of him. (West coast San Francisco area)

[mike ramirez racing]

af2, who is Al and are his bars for leaf spring cars?

Al's Automotive.
He started building the bars in 1962. As of today he is working on a 56 Ford he built 40 years ago with lift bars and a straight axle in front. He is putting a ZZ502 in it.

They work the best with leaf springs. The C/Gas car runs coil over and is dead consistent on 60's(till the slicks need replaced)

The guys in the Bay area know of him. (West coast San Francisco area)

I've never heard of him but heard of Al's auto. What car does he run in C/gas?

I have to tell ya I had slapper bars that were custom made for my car so they didnt hang down and worked good. I was gonna buy Cal-Tracs cuz they were different and lots of stock suspension 10" slick cars were using them and they were working excellent. They have made their way to the street too...anyways my friend Leonard offered to make my some traction bars like the Cal-Trac but were fixed not pivoting. I have adjustability and they work very well for my car.

In one of the Hot Rod magazines they did an article on the "poor mans 4 link" they took the leaf springs on a 55 chevy and did the clamping deal up front and then put a solid bar above the axle to the frame. With upper bar and the leaf spring now stiff up front its a 4 link.

[Novaz]

Cant say my results mean much to anyone elses setup but heres what i have 2800# 72Nova
9" rear end I relocated dble adjustables behind the axle vertically installed a hotchkiss sway/anti roll bar ,put a half leaf on the front of my multi leafs and clamped the front halfs of the leaf pack with 3 clamps per side I also tied the sub frame connectors to the floor with some square tube , last year was my first season and after learning a bunch I finished up with a 10.30@133 with no slapper bars or caltracs this year hoping to go 9.xx
theres some pix here.
Thanks to Bubstr and Jeff Swisher for the help and info

http://www.glowfoto.com/users3/dnewnova ... 1&offset=8

http://www.glowfoto.com/users3/dnewnova ... &offset=17

http://www.glowfoto.com/users3/dnewnova ... id=1829162

[A HotRod]

That is a very interesting approach, and it appears as it works too!

[BrazilianZ28Camaro]

Bubstr wrote:
"I'm having a hard time seeing how a caltrack will change the instant center. The actual front mounting location of the spring or the bar does not change. the tire contact patch does not change. It could Stop the wrap up of the front spring half and even spread the load a bit on the most sever bend of the spring on a wrap up. It could even induce rear steer depending if they where set equal, but I can't see an I/C change. I can see a I/C change on a pinion snubber, depending on hight it's set at. There are different connecting points on a snubber.

The front half stacked spring is for wrap up control with out changing spring rate. If you take a leaf spring, for most of our uses, you can figure the front half is for wrap up control and the rear half is for rate.

The only ways I can see to change the instant center on a leaf spring is, 1 change front mount, 2 lowering blocks (ride hight up or down), 3 rearching or dearching springs, 4 pinion snubber, 5 shortening or lengthening rear shackles. Any thoughts on this?"







I would agree with all of this since the mounting point on the vehicle does not change and there is only one per side unlike a four link.

It's my belief that the two adjustment holes just make the front half of the spring act stiffer or weaker via the input from the rear mount when the axle tries to rotate. One adjustment just has more leverage than the other and pushes on the top of the spring harder so as to make the spring act stiffer.

That's the way I see it, but I would like to hear more from some of the real suspension experts on this subject, as I'm sure many others would too. CJ

I agree. The caltracs are simply anti wrap up, pre loaded devices.

If leaf spring wrap up is eliminated by other ways the caltracs aren't necessary, they are?

[Calypso]

I agree. The caltracs are simply anti wrap up, pre loaded devices.

If leaf spring wrap up is eliminated by other ways the caltracs aren't necessary, they are?

An old thread, but interesting. I don't claim expertise, but I do see this differently (I'm using Cal-Tracs ).

The bar front height change causes a change in behaviour of the car, which is similar what you would get fom IC change. Bar in the upper hole separates rear suspension and lower hole lifts front end more. If they were anti wrap up only, that shouldn't happen.

I've explained this to myself like this: when the front pivot bolt rests on spring, the bar (front) attachment point can't move forward. If the attachment poind will not move forward, the rear axle (pushing that point with the bar as the axle wants rotate the opposite direction to tires) does not know if if the attachment point is welded to the frame or not. It behaves like it was welded from the axle perspective. Then the angle of the lower bar does indeed define the instant center.

If you begin to look closer, when the rear suspension separates, it actually allows small movement of the bar attachmant location (towards front of the car) as the spring bends and pivot transfers the movement to the bar end. However, this has very small effect to the bar angle.

[BrazilianZ28Camaro]

"Bar in the upper hole separates rear suspension and lower hole lifts front end more."

did you keep the same pre load on both holes?

If the pre load was different the rear suspension squat will be different.

when you put the front of the bar on the upper hole, the force it impact on the spring is multiplied or divided by the relation of the distances of the points of the front triangle to twist the spring AND/OR lift the car, like a lever effect.

When you set the bar on the lower hole the force acting will be greater than before,to keep the spring firm, and therefore shock the tires sooner. This can make your car plant the tires and lift the front end better.

I'm not a expert but I know that is a dynamic work. Not that easy to understand

[CDMBill]

I've been lurking on this this discussion for sometime trying to get clear on the concepts involved. For full disclosure I have a bastard setup with Cal-trac split mono leafs and Competition Engineering Slide-a-link bars.

In order to have a virtual pivot point like a four link the the Cal-Trac or CE for that matter would have to cause the rear end to move through an arc that is different than that based soley on the front spring eye of the leaf. With some preload on the bar that change is almost zero unless the spring itself straigtens out a bit as it would be in tension and the bar in comnpression. This iseems to be a tiny change in I/C assuming the axle stays in the same location relative to the body of the car.

This is the fundemental issue as a leaf setup that doesn't cause either body sepration or squart has zero change in what I would call DYNAMIC I/C and therefore has no effective change in I/C period.

However, my experience and others with Cal-Tracs shows that preload and the position of the front bar changes the dynamic I/C as the axle moves differently based on pre-load and bar postion. My car hooks best when I have more pre-load and the rear tires separate by 1-2" from the rear wheel well in pictures. This also shows up as greater front end lift as the more effectively leveraged transfered torque creates greater front end lift and weight transfer.

This is in contrast with a well set up four link car that plants the tries and doesn't even pull the front tires but leaves hard. Think Pro Stock or the really fast Comp Eliminator classes. The typical Stock or Super Stock car pulls the wheels up two feet. Excieting but inefficient. Just like those guys whose cars twist like pretzels at the launch. Wasted power.

This my way of resolving the appearant conflict between the "there is no I/C change with any traction device on Leaf springs" and "yes there is with Cal-tracs". Cal-tracs enhance the dynamic I/C change and that's why they work and why so many people try to make cheap or even not so cheap knock offs.

The clamped front leaf, MOPAR Super Stock fanboys ( I used to be one) are living in the past, there are better ways to hook and go faster. But, they'll have to make a change to find out.

[MaxFlow]

Leaf spring induces roll steer.......Bar does too.....They swing in different arcs.

What we done back in the day was use an "Equalizer" from a Reyco type suspension. Mounting the front spring eye on the front and under acceleration the equalizer would rock and shorten the effective length of the front half of the spring. I would make a 250R625 leaf main with zero arch in the front and when I rolled the spring eye I would cut it down and get rid of that torsion twisting large arse eye and rubber with thin brass bushing. The long chevy front half would be cut in half upon acceleration. I should have mass produced those for production but made them for a few guys at the track and dominated the "real" street tire classes then, deadly consistent setup, too. They closed our local dragstrip in 85 or so and there was really no interest.

[BLACK BART]

When you guys change the preload on the bars it also changes your pinion angle. If you are not keeping pinion angle consistent with every change in preload you are not making a valid test of the changes the preload makes.

Those damn bars flat out work any way you cut it, but they are as complicated or as simple as you wish to make them. I for one would like to find something with fewer parts, especially moving parts, that did the job just as well. To me, a simple part is a beautiful thing when it works properly.

CJ

[enigma57]

Have you seen the Mopar Chassis Book and what they called the “Leaf Link” as used on the Motown Missile `70 Pro Stocker? The leaf springs are clamped from the axle forward at each leaf tip and a solid link is above the axle. There’s more to it than just that, drawings and an explanation are in the book. The main leaf is heaver in the Mopar racing “Super Stock” spring pack.

My father taught me the “moonshiner’s trick” of clamping the leaf tips forward of the axle when he and his racing buddies put some on a Hudson Hornet circle track car in the early 50’s. Absolutely the best thing you can do for an early Mustang or Camaro if you want it to remain flexible enough in the rear to handle well in corners too. Clamping the leaves increases the rear roll stiffness and has to be balanced with a bigger bar in the front to keep it from being loose.

For the Camaro and Nova a good trick is to use the mono-leaf for a main leaf, cut the front eye off the multi-leaf main leaf so the front tip is right under the front spring eye bolt and also use 2 or 3 secondary leaves. The extra leaves are shortened or cut off behind the axle so the spring rate isn’t increased too much. Make solid clamps with 3/8” x 2” strap with two 3/8” bolts on each end as close to the springs as possible and don’t use the slippy stuff between the springs. This gives the strength of the larger main leaf with the axle wrap-up control of the clamped multi-leaf segment in front of the axle. A pinion snubber is a good thing. This method is too simple to please some people.

Excellent info, Tuner! I have used the MOPAR method with success on several '55 - '57 Chevys many moons ago. What I did was to have a spring shop de-arch the main leaf for a 2" drop (to compensate for the added stiffness that would be built into the springs, as I wanted the car to ride near stock height when done).

Then I had them make up 6-leaf springs having the ends of the leaves stacked close up front, beginning with the 2nd leaf, which extended forward, terminating below the front spring eye and staggering the remainder of the front leaf ends rearward at 3" intervals. I made up clamps from 5/16" thick strap iron 2" wide and clamped these springs in 2 equidistant places between the front spring eye and axle tube.

Behind the axle, only the upper 3 leaves extended rearward, terminating in the usual widely staggered OEM way, the remaining 2 (lower) leaves terminating (cut off flush) just behind the U-bolts securing the rear axle.

In other words, the front portion of the springs were stiffened considerably whilst the rear portion behind the axle worked in normal OEM fashion.

I ran modified shock mounts with 2 HD gas filled Koni shocks per side (1 in front and one just behind the axle tube and U-bolts).

Worked great. Cornered well and controlled the rear leaf springs perfectly during heavy acceleration and braking. No traction bars needed.

Happy Motoring,

Harry

[pdq67]

I love my beat-up, homemade slappers.

And one way to make them work in reverse is to take the slapper-bars front mid-spring "clamps" and set the top of them right on the top main leaf's so that when you go into a hard brake, they pull down on them and keep the rearend from reverse wrapping the springs up. But doing this will probably make them way noisy running down the road.

All that said, "Chicane" should be able to hook you up with a pair of H-D rear leaf springs that have a 2nd leaf that wrap's part way around the front spring eye such that no traction aids are needed.

pdq67