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Discussion Starter #1
Last race of the year here started today. I lowered the front of my caltrac bar down 1" by building new sidebrackets. This pushed my IC out in front of the CG by 17" and lowered it 2".

Here is video of the two hits we got today....first run was a 10.99 at 121.99 w. a 1.55 60ft.
Second run i stiffened the rear shocks 1 click, upped the air in the tires 1/2lb and turned the launch up 500rpm to 2500.
11.04 @ 121.66 w. 1.62. As the vid shows the added launch rpm caused the tires to do the plant, rebound............plant, rebound.

BUT.....

Im so happy to finally start seeing the light at the end of the tunnel.
For those who don't know......im stuborn an apparently feel i have something to prove. :roll:
This is all motor 4100lb truck w.Caltrac/leafsprings, DOT tires and mufflers driving to and from the racetrack track.

Looking at the video im pretty certain some stiff sidewall tires will be on it next spring.

 

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Lookin' much better Mike... All around, the 1st launch looked to be the best/smoothest of the 2... I definitely saw daylight on both runs though... :twisted: :twisted: :twisted: Pretty awesome for a truck... :wink: I think a stiffer sidewall tire will definitely help... Wish we had an 8+ month season here like some others have... BUT, then that would be cutting into hunting here this time of year... :lol: :lol: :lol: Good job,



Doug... 8)
 

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Discussion Starter #4
Thanks Doug!! Yep, the first was a 1.56 leaving at 2000 on the brake....it hooked pretty darn good w. out much rebound bounce so i decided to tighten up the rear shock 1 set and bump the leave to 2500 and see what happens. 1.62 w. bad rebounding.

Went 11.00 on todays TT....dialed a 10.98 ran a 10.99 but redlit by .022!! The bummer is that i had a .050, .041 and a .031 in time trials.
Hugo...yes i just go home but still have more racing tomorrow and through the weekend. Do you have an adj. to suggest?? Im ears!! lol
We have another bonus race tomorrow (basicly a no box gamblers) that im in then the Big race kicks off Saturday.

Here are a few shots of the new brackets i cut out....


 
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I take it the H-bash your talking about im not going this sucks but its all good have the new one here next year. Looking good keep it up. Jason
 

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Must be nice to be racing during the week when we are all "supposedly" working :roll: :D :D :D

Still a lot of separation in the rear, and it cant keep the tire planted. Lower the bar to the bottom hole, leaving the shocks where they are, and you will be alot closer :wink:
Adjust shocks as neccessary.

Goodluck.
 

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Your truck looks cool!! I hope you get the chassis sorted out, it looks like it leaves real hard and then unloads.I'm sure you'll get it figured out with all the help on here.good luck :lol:
 

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Dano,

You gonna be my Dyno helper "BIOTCH" this weekend :lol: The Coug needs all the help we can get. You know he will be at the Steak house and we will have to do all the work :lol:

Sorry to high jack your thread Mike , you got that puppy on the run now :wink:

Did you tell me today that this was the last race or are you going to get to test some more?
 

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Yeah blake ,I'll probably be able to help you guys this weekend....what time ?
 

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I think Randy is getting there around 3:00 tomorrow afternoon, call me a couple of hr's before you head up there, and I will meet you.
 

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No problem ,I'm only 20 minutes away :lol:
 

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You said you tightened the shocks 1 click, but where does this 1 click put the shocks at in their loose/tight adjustment range? If they are currently set kinda on the loose side, (say 1, 2, or 3 clicks from full loose) it might be interesting to crank the shock extension valving up close to full tight and pull some 60 ft's just to see what happens.

Upping the launch 500 RPM for the 2nd pass probably increased the available "at launch" power/torque number just enough to offset some of the benefit of increasing the shock's extension dampening 1 click.
 

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Discussion Starter #15
The shocks have 12 postions available, i was on 10 in the first run and 11 in the second as recommended by Hugo in a diffrent thread.

Ive got 4 passes so far and the the first hit has been my best 60ft. After i tried the higher launch rpm i decided to leave the shocks and air psi the same and just turn the leave back down.

W. the exception of the second hit (which was my worst 60 at this event) all of my runs have been .01 apart..... 10.99 first pass, 11.04 second(2500rpm launch) 11.00 and 10.99.

If i can cut a light again the thing should be pretty easy to dial and race. :lol:
 

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That answers my question. If the shocks are almost maxxed out, then its time to move the IC down(lower the bar to the bottom hole), and start with the shocks in the middle at 6, and tune them up from there.
 

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Discussion Starter #17
While i was just sitting here i had an idea.......Im thinkin by a four links theory this thing should squat bigtime. Clealy it isn't! Ive been trying to uderstand why not?? Obviously its cause its not a fourlink, But the only thing that i think would affect it is the way the leverage created by the bar is tranmitted in a downward flexing motion of the spring causing the body to seperate??

Im thinking i could limit this force by shortning the space from the front spring eye bolt to the bolt that crosses the top of the spring. By putting this point closer to the spring eye it would take some of the force away and flex the spring less.

Or i could build some type of slider that doesn't by nature force the spring into extension.

I don't feel that a Caltrac design could ever be made to squat due to this design feature.
Any input ??
 

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Hey Mike, I ended up doing a very similar thing to my leafs before I finally made the time and was lucky enough to have someone volutarily drive 300 miles to help me change my rear suspension... I just used some 1/4" plate 5" wide, and 6" long, and drilled 4 1/2" holes in both pieces (per side) and clamped them around the leafs front and rear, and sliding them either direction until it stopped or at least dramatically slowed the rebound of the leafs to allieviate the bouncing...

Good luck,




Doug... 8)
 

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dirt_worker said:
While i was just sitting here i had an idea.......Im thinkin by a four links theory this thing should squat bigtime. Clealy it isn't! Ive been trying to uderstand why not?? Obviously its cause its not a fourlink, But the only thing that i think would affect it is the way the leverage created by the bar is tranmitted in a downward flexing motion of the spring causing the body to seperate??

Im thinking i could limit this force by shortning the space from the front spring eye bolt to the bolt that crosses the top of the spring. By putting this point closer to the spring eye it would take some of the force away and flex the spring less.

Or i could build some type of slider that doesn't by nature force the spring into extension.

I don't feel that a Caltrac design could ever be made to squat due to this design feature.
Any input ??
Well, the fact is you do want some amount of rim/body separation at the initial hit anyway (not squat). But you want that separation to be a limited/controlled/restrained amount (only the amount that is needed to initially apply weight/pressure to the slick as the rim starts to wind-up the sidewall). Front-to-back weight transfer (pitch rotation) does not start the "hook"........it's the other way around because the separation & initial hook/sidewall wind-up is what starts the weight transfer.


The Caltrac might be designed to work kinda like a 4-link, but using a flexible curved/arced leafspring as the "top bar" is bound to cause some issues with big "at launch" torque levels a big inch motor can have. The Caltracks seem to work real good for a number of the small block & Cleveland guys because they don't (generally) have a massive amount of torque to work with. I can see where using the leafspring as if it was the "top bar" of a pseudo 4-link probably causes the I/C to move around a ton during the launch as the leafspring gets tension loaded, and then tries to snap back to a curved shape as the launch progresses.


It's said that on 4-link design, the height of the "imaginary triangle" it's 3 leverage points create (continuous line drawn from the I/C, to the top housing rod-end, to the bottom housing rod-end) is said to have an effect on how efficiently/smoothly the car can load the I/C point during the launch (for a given amount of power). If this is true then the Caltrac setup probably has an imaginary triangle with the least height of all the 4-link designs out there.
 
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