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Re: Caltrac Science???
[Re: Cuda367]
#1693041
11/01/14 12:27 AM
11/01/14 12:27 AM
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Joined: Oct 2007
Posts: 3,978
Hilltown Pa
1967dartgt
master
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master
Joined: Oct 2007
Posts: 3,978
Hilltown Pa
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The front triangle pivots and increases the down force on the rear tires. The hard you make it pivot the harder it pushes down on the spring. You don't need it till you go faster then tens.
Brett Miller W9 cnc'd heads
STR Chassis fabraction
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Re: Caltrac Science???
[Re: Cuda367]
#1693042
11/01/14 12:42 AM
11/01/14 12:42 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:
First I don't want to start a war here, I am just trying to understand what my simple mind is failing to understand. I know that Calvets raced 60's mustangs and with the rear leaf spring design that they and other leaf spring cars, I can diffinately understand there need and how they function. A wonderful way to solve there problems but I get a little lost on there need on a Mopar. I understand the need for a very stiff front segment but once you acheive that how does there design put more down force on the tire???
Why would it make any difference that's its a Mopar. Leaf springs are leaf springs. If the design helps a Ford or Chevy....it also helps a Mopar
The goal is to make the segment as stiff as possible. ANY flex here is too much
Monte
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Re: Caltrac Science???
[Re: Monte_Smith]
#1693043
11/01/14 02:22 AM
11/01/14 02:22 AM
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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:
First I don't want to start a war here, I am just trying to understand what my simple mind is failing to understand. I know that Calvets raced 60's mustangs and with the rear leaf spring design that they and other leaf spring cars, I can diffinately understand there need and how they function. A wonderful way to solve there problems but I get a little lost on there need on a Mopar. I understand the need for a very stiff front segment but once you acheive that how does there design put more down force on the tire???
Why would it make any difference that's its a Mopar. Leaf springs are leaf springs. If the design helps a Ford or Chevy....it also helps a Mopar
The goal is to make the segment as stiff as possible. ANY flex here is too much
Monte
The Caltrac science does help the ford leaf springs better then the Mopar leaf springs. The axel is centered on the 60,s mustangs that Calvert designed them for, While the axels are much more forward on the same era mopars.
Monte, the statement Any flex here is too much" isn't accurate. At least in a lot of these front shorter segment Mopars.
A solid front short mopar front spring segment can be to violent reacting on a 450#+ torque motor on say a Abody,
The science behind the Caltracs is more then to make it just a solid bar.
Cause that's Easy to do.
EDIT; And the science behind the Caltracs isn't that technical.
Its like, okay my axel wants to rotate, can I put a lever off the bottom of my axel to push another lever from a pushrod to a V lever to push down on the upper part of my front spring so it wont rotate so bad.
The only science is to figure out the approximate lever lengths. And even those lengths will be a guestimate to what works better. Good idea to build in some adjustability here.  
Last edited by Sport440; 11/01/14 02:39 AM.
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Re: Caltrac Science???
[Re: Cuda367]
#1693048
11/01/14 01:14 PM
11/01/14 01:14 PM
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Joined: May 2010
Posts: 485
Central California
MoParFish
mopar
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mopar
Joined: May 2010
Posts: 485
Central California
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Quote:
Thanks so far. Lets say I can put X amount of torque to the pinion and read the amount of preasure to the front spring eye bolt. Now I install caltracs and repeat. For there to be an increase in traction the preasure at the front spring eye would have to increase and I am not understanding how that would happen. I have to be missing something because the answer here is always to put caltracs on it and I am fine with that as soon as I can understand why. My opjection to them is that they hang down below the car and make me think I am looking at some brank X with slapper bars on it. I am thinking I could put a bracket on the top of the axle and install the front part of the caltrac pionting up rather thab down. Now hidden, but won't put anything on until I understand why I am doing it. Thanks again
You would lose the down-force on top of the spring. As the bottom bar pushes forward, the "triangle" pivots off the spring eye bolt then pushes down on top of spring. I consider it a kind of basic four link? No expert here either but, works good on my stuff
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Re: Caltrac Science???
[Re: superhog88]
#1693050
11/01/14 01:18 PM
11/01/14 01:18 PM
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Joined: Jul 2010
Posts: 1,491
Oologah, Oklahoma
Big Squeeze
pro stock
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pro stock
Joined: Jul 2010
Posts: 1,491
Oologah, Oklahoma
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Quote:
I am no expert and will never claim that i am. My under standing is that the caltracs bars do the same thing that a pinion snubber only better. they limit the rotation of rear differential. the front segment of the spring and the caltracs bar act like a 4-link.
The difference is that a snubber does NOTHING to keep the leaf springs from wrapping up...when leaf springs wrap up, they don't consistently wrap up the same way plus wrapping up wears them out...
That's ALL Cal-Tracs do...keep the leaf spring from wrapping up...and they're adjustable to compensate for different power levels and track conditions...it's not any more complicated than that...they DO NOT apply more downward force on the tire or anything like that...The more power you have and/or the more available traction you have, the less leverage you need pushing down on the top of the leaf springs to keep them from wrapping up, and vice versa....
IMHO, the only reason to run them is if you have to (like in a restricted headsup Class) or if you don't want to install ladder bars or a 4-link, because they're both way better...
BTW, the reason for different length front spring segments is to move the Instant Center (front spring eye) closer to the 100% anti squat line....If the body tries to seperate from the rear wheel, you need a stiffer rear shock adjustment or you can move the front spring eye forward...
If you can't handle the truth, you're living a lie.......
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Re: Caltrac Science???
[Re: Cuda367]
#1693051
11/01/14 01:34 PM
11/01/14 01:34 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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Quote:
I am thinking I could put a bracket on the top of the axle and install the front part of the caltrac pionting up rather thab down. Now hidden, but won't put anything on until I understand why I am doing it. Thanks again
You absolutely could do this. The problem that you have, is that it puts the threads of the heim joint in tension instead of compression, which is much more likely to fail then the other way around. I thought about doing the same thing to help "hide them".
As for your question on caltracs creating more "pressure" on the tire. While there is no special geometry about them that makes more "pressure" on the tire from a static evaluation (links/torques/etc...) the part your missing is what happens in the DYNAMIC tire event.
When the car launches the pinion tries to climb the ring gear. One of three things happens.
1) The axle rotates up (car doesn't move).
2) The axle stays still and the tires spin without forward car movement.
3) The axle stays still and the car moves forward (traction).
In reality all three of these things can/do happen similtaniously. However during the initial "hit" the majority of the movement is #1 above. This is mainly because the force to rotate the pinion is less then any forces required to overcome the intertia of the body/tire.
What happens is that when the axle rotates up, there is a vertical force translated through the front spring segment to the front spring eye.
If you remember from high school science class, every action has an equal and opposite reaction. In this case, when the spring tries to pick up the body through the front spring eye, the opposite "Force" doing that is pressure on the tire. You can imagine this even in a static environment, if you put the jack under your tire, whatever force you apply to the tire, is translated to the front spring eye.
This all happens VERY quickly. Because shortly after the "hit" the torque of the tire start to overcome the inertia of the car to move it forward. So there is a very small window between "hit" and forward movement.
That all being said, what the caltrac does is allow the front segment to become very stiff almost immediately. If the front segment is soft, during the time period of tire "hit", all of the energy from the pinion rotation will simply be used to bend the spring (no additional force on the tire). However if the front spring segment is "stiff", then it allows the energy to transfer immediately to the front spring eye. When it tries to quickly accelerate the body upwards, the inertia from the car resists the movement. The result is that the sidewall of the tire "looses" the force battle, and the tire gets planted into the ground HARD.
Once you have the tire planted, it is less likely to spin because you now have more traction. More traction means that you can accelerate the car forward sooner/quicker.
Make sense?
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Re: Caltrac Science???
[Re: Duner]
#1693055
11/01/14 01:56 PM
11/01/14 01:56 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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Quote:
Alright, I have to ask.
What is the difference in what you just described vs the old traction bars you bolted under the spring?
There isn't a whole lot of difference, except one thing.
The caltrack through the front bracket pulls DOWN on the front of the main leaf segment at the front. The slapper bar pushes UP on the front of the main leaf segment at the front.
Since this area is already trying to bend UP (and is the primary source of spring flex), the slapper bar is less effective. It basically makes a large portion of the spring segment "solid", but it doesn't fix the biggest area of bending (front main leaf right behind the front spring eye).
Also, since most slapper bars have a rubber snubber on them, the rubber compresses (no different the having the spring waste pressure/energy through flexing).
The caltrac is steel on steel, so there is very little flexing. As Monte pointed out, you don't want ANY flex in the system.
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Re: Caltrac Science???
[Re: Duner]
#1693056
11/01/14 02:02 PM
11/01/14 02:02 PM
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Joined: Mar 2010
Posts: 632
MD-USA
Dodgeguy101
mopar
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mopar
Joined: Mar 2010
Posts: 632
MD-USA
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Well,
here is why I am asking. I wanted to try something different. So, over on bigblockdart.com, in the tech section, there is fellow across the pond, that made a bar system that goes under the spring plate and goes to the front bottom of the spring. Now, I made a set, and put them on the car.
Car has worn out springs that have been on the car for 30 years. I know I am going to beat up over this, but for the amount I drive the car, it was ok. It doesn't spin, car takes off straight as an arrow. The car was starting to bend the front portion of the spring. I put these homemade bars on, it stopped the bending and the car dropped the 60ft time from average 1.45 to 1.39. Now mind you the convertor isn't optimum for the engine, but it is what I have. Its a high 9 second car. It weighs 3100 with my 200lbs in it.
I just want to know, if these bars aren't great, I may get the Caltracs and new springs and move on.
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Re: Caltrac Science???
[Re: Duner]
#1693058
11/01/14 02:05 PM
11/01/14 02:05 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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Quote:
There must be a little more to it than simply stopping the housing from rotating.....
I made new rear mounts for my Caltracs that added 2.5" more "arm" to them - and dropped my 60' numbers by 2 tenths without changing anything else. I'll let some experts tell us why it worked - because I'm one of those "try it and see" kind of guys. I don't necessarily HAVE TO understand all of the science behind it. I try it anyway.
It's not exactly about stopping the housing from rotating, it timing the energy from the housing rotation, to apply it to the tire when you need it.
When you added length, you did two things. You lowered the pressure on the caltrac bar because you changed the ratio's between the axle arm and the front caltrac pivot arm. But you also accelerated how long it took for the front spring segment to go solid. 1 degree of axle movement resulted in more horizontal cal track bar movement, which made the front bracket rotate quicker. This is the same principal as putting the caltrac in the top hole (changes the pressure on the spring), or adding preload (changes the time before the front spring segment goes solid).
My guess is the reason that this worked on your truck is because you needed to keep the front spring segment a little softer because the shocks you have couldn't control the "hit" on the tire. I have no idea where the IC is on your truck either, so that may have something to do with it since it's a little "out of the norm" compared to other stuff.
P.S. There is nothing wrong with a "Try and See" approach. It's how most drag racers have been going faster and faster every weekend for years. I am fortunate enough to understand a little more science behind it, so I just try and share it in an easy to understand explanation.
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