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slapper/ladder bars

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    Posted: Nov/17/2019 at 1:05pm
since racing season is over(for pa residents!) i decided my car is in dire need of suspension work(44 years of original parts) - its a purpose built bracket car that runs 13.50- 14.00 that i've owned and raced since February of this year.  my car has  lakewood style traction bars. when i got them off and put then on the floor side by side i noticed 1 was 5 inches shorter then the other!!!(drivers side shorter)  is this a mistake or am i missing something here?  i know they are used to prevent axle wrap /wheel hop and when racing my car  i get 60' times between 1.82 - 1.92. (3000 stall converter/4.11 gear/slicks/1500 rpm@launch,360 w/a mild cam). i tried to give you enough info about the car to help with this situation. thanks  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Nov/17/2019 at 4:04pm
Normally the idea is to have the bump rubber under the front spring eye unless this is some sort of suspension tuning trick that I don't know about. Your 60' times seem pretty good for that ET, not sure if you would see any gains from Caltracs.
I've finally given up drinking for good...........now I only drink for evil.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote 360x Quote  Post ReplyReply Direct Link To This Post Posted: Nov/17/2019 at 5:25pm
i have very little invested at this point and the car launches well and like you i dont think caltracs are needed. i guess i'll re-bush the springs and shackles and put these bars back on the way they were and keep playing till something breaks!  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 360x Quote  Post ReplyReply Direct Link To This Post Posted: Nov/20/2019 at 6:02pm
westernred  mentioned that the rubber bumper should be located under the spring eye -- that being said what can i use to make these equal length and extend to the spring eye? 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Nov/22/2019 at 2:04am
I just made my own out of some 40 mm x 40 mm RHS and a bit of plate. My understanding is that you can adjust the distance between the bush and spring eye to tune your launch.


I've finally given up drinking for good...........now I only drink for evil.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FuzzFace2 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2019 at 7:58am
Originally posted by 360x 360x wrote:

westernred  mentioned that the rubber bumper should be located under the spring eye -- that being said what can i use to make these equal length and extend to the spring eye? 
I would not waste my time trying to fix the them.
 
I know you said you did not think the Cal Trac's were the way to go and I will say you are wrong!
I have them on my 70 Javelin drag only car, 360 w/cam, 3000 stall TH400, 4.56 Detroit locker AMC 20, 9" slicks, 13.0 - 13.5 and also ran brackets when I was racing.
 
What is nice is if the track changes the Cals are easy to adjust unlike the slappers you have now. You would need to adjust the rubbers to have a different gap between springs and bumper.
Just a little change of the Cals makes a big difference.
 
You did not say what model this is, what you did to the front suspension, or did to make the car lighter being a drag only car?
Mine has Gremlin 6cly front springs, 90/10 shocks (gas shocks out back), sway bar removed, battery to trunk, gutted the inside just a race seat & the needed gauges.
I may be ugly and not as fast as the others but in brackets you just need to run the numbers.
I don't remember the 60' but think it could have been better, the reaction times were great and true from run to run as was the 1320 numbers to run many rounds.
Go with the Cal Trac's and don't look back
Dave ----
 
ps: I have slappers on my 70 street Javelin as that's what was on it when I got it and they will stay for the street.


Edited by FuzzFace2 - Nov/28/2019 at 8:02am
TSM = Technical Service Manual

75 Gremlin X v8 for sale
70 Javelin 360/auto drag car
70 Javelin 360/T5 Street car
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 360x Quote  Post ReplyReply Direct Link To This Post Posted: Nov/30/2019 at 6:41pm
my car is a stripped/gutted car with a seat and gauges similer to yours except its a gremlin(2840# with me in it 
90/10 front with v8 springs - sway bar delete -- stock rear springs 
gonna redo f/r suspension with some new parts and bushings - like the idea of 6cyl. springs 
got some light weight skinny rims for fronts and aluminum for the rear(had all steel wheels!) 

i am not unhappy with the slappers for now - i'll see how the car performs this spring and go from there 
thanks for all the input -  GO AMeriCan !
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Post Options Post Options   Thanks (1) Thanks(1)   Quote tached_out Quote  Post ReplyReply Direct Link To This Post Posted: Jan/01/2020 at 6:53pm
A good set of slapper bars will get you off the line quickly and consistently. I built mine out of 2 1/2''x1 1/2'' rectangular tube similarly to Western Red's. My car got 1.5 second 60' times. It ran low 11s.

A Gremlin uses a bar that measures 23'' from axle centerline to spring eye.

This car sat with the top of the tires one inch below the wheel well and the front of the bars pointing downwards. You can see how much they plant the tires in the picture.

Glenn




Edited by tached_out - Jan/01/2020 at 6:58pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CARnivore Quote  Post ReplyReply Direct Link To This Post Posted: Jan/03/2020 at 6:15pm
The poor mans leaf spring traction setup has always been solid front eye bushings and spring clamps on the front side of the leaves effectively turning them into solid links. I run caltracs on my AMX
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcenthusiast Quote  Post ReplyReply Direct Link To This Post Posted: Jan/07/2020 at 10:50am
...I think this thread might go in 'suspension' category...

I also think that 'anti-tramp' (British slang name) or 'override bars' (US name) were first used by OEM on cars that showed need for it -to control wheel hop or prevent excessive leaf spring deflection.

As I understand it, one of the nuances of what is not being discussed here is 'pinon angle' which is a sub-topic of 'chassis geometry'.

'Cal-Trac' bars create variable pinion angle with relation to torque loading of the chassis.

'Slapper bars' create pinion angle limitation during torque load reaction by the chassis.

AMC 'Torque Links' create pinion angle limitation for both power and brake torque load chassis reactions, some having adjustable slots for 'pinion angle preload' and some were made with no slots.

AM's Torque Link traction bar system was preceded by early model leaf spring Chevrolet Corvette, Studebaker Avanti and early Shelby Mustang which also feature a similar 'override traction bar' set up on those cars.*

*Torque Link type traction bars tend to be more important for sports car applications because they affect leaf spring deflection under braking as well (axle housing twist motion both ways; acceleration and deceleration) for improved handling. Cal Tracs and slapper bars (generally speaking) only work to control axle twist under acceleration.

The angle of the slapper bar with relation to the chassis, is related to what is described as 'instant center' in most drag race chassis tech articles. -the lengths and angles all affect how much leverage is transmitted through the slapper bar. -a 90 degree angle has more force than any other... see Khan Academy 'torque of an angle' https://www.youtube.com/watch?v=ZQnGh-t25tI

Moreover, instant center, whether it's higher or lower, moved forward or back, affects how the car moves with relation to it's engineered 'center of gravity'. (this component involves leverage also)

As I understand it, Cal-Tracs actually create a 'roving'/variable instant center as the torque load is distributed into the chassis under acceleration. -part of the design: the variable geometry effect is similar to having a moving weight inside the car which reacts in reaction to power input?

...it's all very interesting topic to study; no reason to be bored & plenty to learn -as usual!


Edited by amcenthusiast - Jan/07/2020 at 10:54am
Link to XRV8 Race Parts website: www.amcramblermarlin.1colony.com
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