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Re: Foot braking with Caltracs and preload?
[Re: menomoniemopars]
#1249025
06/12/12 08:54 PM
06/12/12 08:54 PM
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Joined: Jan 2004
Posts: 2,103
East Coast, NJ
fig426
OP
top fuel
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OP
top fuel
Joined: Jan 2004
Posts: 2,103
East Coast, NJ
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This is good stuff here. Now I have to figure out what my car likes. With a 1/4 turn preload, and launch from idle, I was getting a 1.55 60 foot. With a 3000 rpm launch, my 60 went down to 1.589. That's why I asked the question to begin with. I still think from my ET and my MPH, I should be getting a better 60.
Chris from New Jersey
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Re: Foot braking with Caltracs and preload?
[Re: nss guy]
#1249027
06/12/12 10:22 PM
06/12/12 10:22 PM
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Joined: Mar 2009
Posts: 2,464
Sydney,Australia
tex013
top fuel
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top fuel
Joined: Mar 2009
Posts: 2,464
Sydney,Australia
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i run the caltracs on my satellite with XHD springs,small block t bars. rancho rear shocks and QA1 single adjuster fronts. set the caltracs as per instruction,i think 2 turns preload with driver on both sides,lower hole front shocks full loose.i tried starting off rear shocks at 3-5 but found a lot of separation and wheel spin just off the line,topping out shock?.for the last 12 months have run the rancho's at #9,full tight extension,rarely have traction issues now. 1.52 60'best never played with preload after that as it pulls straight  Tex
New best ET 10.259@129.65 .
New best MPH 130.32
Finally fitted a solid cam,
stepped it up a bit more
3690lbs through the mufflers
New World block 3780lbs 10.278@130.80 . Wowser 10.253@130.24 footbraking from 1500rpm
Power by Tex's Automotive
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Re: Foot braking with Caltracs and preload?
[Re: tex013]
#1249028
06/12/12 10:51 PM
06/12/12 10:51 PM
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Joined: Nov 2004
Posts: 3,517
pacific northwest
Stroker Scamp
master
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master
Joined: Nov 2004
Posts: 3,517
pacific northwest
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1.44 best 60' footbrake, launch at bout 2500, havent really loaded the convertor, driver side 1/4" form touching, pass side touching, top hole
best time in my sig
footbrake N/A SB 408 Scamp 10.10 @ 132 street/strip
73 Duster 340 street strip 12.79 @ 105
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Re: Foot braking with Caltracs and preload?
[Re: Stroker Scamp]
#1249029
06/12/12 11:04 PM
06/12/12 11:04 PM
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Joined: Mar 2008
Posts: 553
Kentucky
clovis
mopar
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mopar
Joined: Mar 2008
Posts: 553
Kentucky
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Not as good an angle, but this is the old springs with about .085 gap, it still has some separation during staging but not as much as it does with the spring touching the pin. The rpms should be near the same as the April 7 video. This was a 1.403 sixty foot. Go about 1:05 in http://www.youtube.com/watch?v=I_RGmcnTYJA&feature=youtu.beNext time out we plan to experiment with moving the shocks to 9, upping the launch rpms, and adding air pressure.
'75 Plymouth Duster
Phase I 451 906/590/2-660 10.75/126
Phase II 451 Stage VI/590/1050 9.82/135
Phase III 383 906/Victor-Pump gas 11.30/119
"For by grace you have been saved through faith. And this is not your own doing; it is the gift of God,"
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Re: Foot braking with Caltracs and preload?
[Re: clovis]
#1249031
06/13/12 08:38 AM
06/13/12 08:38 AM
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Joined: Dec 2006
Posts: 1,178
Indy
FlyFish
super stock
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super stock
Joined: Dec 2006
Posts: 1,178
Indy
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Quote:
No, the first is about 3,000 and the second is about 2,000. The two are not really apples to apples on rpm nor springs/shocks, as the second video is on the monos with the shocks set at 8. The first is 6 cylinder springs/shocks set at 6 and spring just touching the pin. I will try to post a video with the old springs and a gap (no pre-load) to get a truer apples to apples. Even with the same spring/shocking setting and rpm, the difference in separation prior to launch is pretty significant. The preload really seems to make a difference.
Thanks for the info  . I'm getting ready to tune my CalTracs again...first outing broke my spring perches and bent the rear housing. I almost have it back together again, but this time with a MO875 and a back brace. 
67 Barracuda street car, 408, e85, 1.38 60', 6.44 @105.9 in the 1/8 mile, 10.19 @130.5 in the 1/4...so far....
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Re: Foot braking with Caltracs and preload?
[Re: moparniac]
#1249033
06/13/12 09:54 AM
06/13/12 09:54 AM
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Joined: Jun 2004
Posts: 148
Montgomery, PA
dodge340dart
member
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member
Joined: Jun 2004
Posts: 148
Montgomery, PA
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Sledgehammer, you are correct; I found more information from Dave Morgan and this is what he said:
Before I say anything, I should begin by saying I have no doubts that the CalTrac bars offer an improvement in the traction of a car. The results are too widespread and too common to say otherwise. However, they do not improve the traction because they relocate the Instant Center (IC).
We define Instant Center as the center of the arc the rear axle moves around as it travels vertically. In this application, we also define the IC as a lift point (there are other ICs in the car that are also the center of an arc, but don't function as a lift point.)
In the case of the CalTrac bar, the front mount of the bar is on a pivoting shackle, which by it's nature means that the rear axle still rotates around the front eyelet of the leaf spring, which was and still is the IC of the rear suspension.
This idea was tried before in the '70s. Chrysler engineers designed a rear suspension called a leaf-link suspension which really did relocate the IC. It had a pair of upper control arms that were rigidly fastened to the differential housing and the chassis. The front of the leaf spring then functioned the same as the lower pair of bars on a fourlink, while the new upper bars did the same as the upper bars on a fourlink. In that design, there was no pivoting shackle for the front mount.
I had no idea the tuneable IC aspect was part of the CalTrac Bar patent, but I have had students and racers show me the instruction sheets that come with the bars.
Competition Engineering created a similar product called a Slide-a-Link which works on the same principle as the CalTrac bar. In this design, the lower bar has an inner tube and an outer tube that can be tightened to reduce the amount of sliding, or extension that these telescoping bars permit.
In both cases, I think all they do is reduce wheel hop by reducing, or eliminating, the spring wrap that occurs when a bunch of torque hits the pinion gear in a rear end.
I hope this helps.
Sorry, if my previous statement confused anyone.
Chris
2011 & 2012 Beaver Springs Dragway Outlaw Street Champion
2012 BSD Friday Street Racer Driver of the Year
3-time Jr. Stock Eliminator
2-time Mean Street Eliminator
'69 340 Dart 1.500 60ft, 11.359et, 117.08mph
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Re: Foot braking with Caltracs and preload?
[Re: dodge340dart]
#1249034
06/13/12 01:56 PM
06/13/12 01:56 PM
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Joined: Mar 2008
Posts: 553
Kentucky
clovis
mopar
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mopar
Joined: Mar 2008
Posts: 553
Kentucky
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70dusterjohn
Can you post some details on your car/setup/timeslips? Going 9.80's with a 1.31/1.32 60 ft is getting it done. Whatever you are doing seems to be working very well-school is now in session.
Thanks for any input.
'75 Plymouth Duster
Phase I 451 906/590/2-660 10.75/126
Phase II 451 Stage VI/590/1050 9.82/135
Phase III 383 906/Victor-Pump gas 11.30/119
"For by grace you have been saved through faith. And this is not your own doing; it is the gift of God,"
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Re: Foot braking with Caltracs and preload?
[Re: clovis]
#1249035
06/13/12 05:07 PM
06/13/12 05:07 PM
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Joined: Jan 2004
Posts: 2,103
East Coast, NJ
fig426
OP
top fuel
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OP
top fuel
Joined: Jan 2004
Posts: 2,103
East Coast, NJ
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Headed to Island in a bit. Gonna try with an air gap and just touching without preload. See how it goes. Hopefully I'll be able to get 4 or 5 runs in.
Chris from New Jersey
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Re: Foot braking with Caltracs and preload?
[Re: moparniac]
#1249040
06/14/12 05:52 PM
06/14/12 05:52 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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As has been sort of implied... every combination is different.
Remember, the key to controlling tire spin, is finding a way to waste energy that would normally be used to overpower the traction to do something else. Sometimes it's body seperation, wheelies, spring deflection, etc...
What a caltrak is doing is managing that tire spin energy through spring deflection. If the spring is very stiff (lots of preload), there is no deflection left in the spring to "waste". If the car doesn't have the traction to use that energy, it will spin.
On the flip side, if the car already has enough traction and you let the spring "wind up" you're wasting energy that could be moving the car forward.
Ultimately on any given combonation, ALL of the energy eventually goes through the spring. It's the only thing that connects the body to the axle right? But what changing the preload does, is changes when that energy is applied. If the car is busy spending horsepower winding the spring up, it can't be spinning right?
That is basically how it works. Changing the bar location in the caltrac effects the above scenario. Putting the bar in the lower hole applys more pressure, at a slower rate to the front spring segment. Putting the bara in the upper hole applies less pressure at a quicker pace.
If the car doesn't spin, more pre-load will usually be quicker. The more pre-load you put in it, the stiffer the front spring segment becomes, and acts more like a ladder bar in the top hole at that point.
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Re: Foot braking with Caltracs and preload?
[Re: dizuster]
#1249041
06/14/12 08:16 PM
06/14/12 08:16 PM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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Quote:
As has been sort of implied... every combination is different.
Remember, the key to controlling tire spin, is finding a way to waste energy that would normally be used to overpower the traction to do something else. Sometimes it's body seperation, wheelies, spring deflection, etc...
What a caltrak is doing is managing that tire spin energy through spring deflection. If the spring is very stiff (lots of preload), there is no deflection left in the spring to "waste". If the car doesn't have the traction to use that energy, it will spin.
On the flip side, if the car already has enough traction and you let the spring "wind up" you're wasting energy that could be moving the car forward.
Ultimately on any given combonation, ALL of the energy eventually goes through the spring. It's the only thing that connects the body to the axle right? But what changing the preload does, is changes when that energy is applied. If the car is busy spending horsepower winding the spring up, it can't be spinning right?
That is basically how it works. Changing the bar location in the caltrac effects the above scenario. Putting the bar in the lower hole applys more pressure, at a slower rate to the front spring segment. Putting the bara in the upper hole applies less pressure at a quicker pace.
If the car doesn't spin, more pre-load will usually be quicker. The more pre-load you put in it, the stiffer the front spring segment becomes, and acts more like a ladder bar in the top hole at that point.
Thanks for making it simple enough for ME to understand  .
Fastest 300
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lots of good info shared on this thread though
