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Re: 230 - 260 leaf springs and 1.26" torsion bars
[Re: docford]
#1485522
08/17/13 12:37 PM
08/17/13 12:37 PM
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Joined: Jan 2003
Posts: 5,388
Pikes Peak Country
TC@HP2
master
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master
Joined: Jan 2003
Posts: 5,388
Pikes Peak Country
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Take the stock car specs with a grain of salt because they were designed for 112 and 115 inch wheelbases. Quite a bit different than your Cudas 108. Weight distribution for you will be key, especially with an elephant sitting on the nose.
No one makes 1.26 or 1.28 T-bars any more. Mopar did make 1.22 bars up until the late '90s early 00s, but they are no longer being made. You can sometimes find them on for sale forums, otherwise you may be limited to a 1.18. However, if you really have everything speced around that, talk to Dick at Firm Feel and see if they could whip up a one off set at 1.24, which, coincidently, is the biggest you can put in the factory E body sockets. To go bigger, you need to convert to C body sockets.
Also, are those rates you have calculated including sway bars at all? You want to look at total roll couple front to rear against total weight, split weight and dynamic weight, which will include sway bars and cross weight in the formula. If you are strictly looking at spring rates and then add s-bars on top of that, your balance is shot. However, since T-bars are a limiting factor, you can often manipulate balance using s-bars and leaf springs.
I'd recommend recalculating with available T-bars to back into a complimentary leaf spring number. There are limited T-bars out there, but you can spec out leaf spring rates pretty easily. Additionally, by setting up a tubular sway bar set up with modular links, you can really dial in the sway bar part of the formula using a variety of diameters and wall thicknesses to get things exactly where you want.
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Re: 230 - 260 leaf springs and 1.26" torsion bars
[Re: TC@HP2]
#1485523
08/17/13 12:52 PM
08/17/13 12:52 PM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
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About to go away
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Not having your reference as a guide, I have to wonder if those rates are predicated on have a lot of down force at speed. I have vague recollections that on the winged cars running back then down force was a substantial factor and the spring rates took that into account. Without out that down force and that level of speed probably means you will be way over springing your ride, imo.
All that being said, it is now 2013, some 42 years later. Suspension theory and design has changed a lot. You might want to step up in time and reconsider.
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
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Re: 230 - 260 leaf springs and 1.26" torsion bars
[Re: jcc]
#1485525
08/17/13 09:49 PM
08/17/13 09:49 PM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
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About to go away
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I dunno, to be honest I was 6 then and I really don't recall that much about racing. I did watch it, but what 6 yo knows anything about the details.
All I know is that Chrysler put a nose cone and a wing on their race cars for aero purposes and that the cutouts/scoops atop the front fenders were supposedly there because down force would put the tire into the top of an unmodified fender.
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
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Re: 230 - 260 leaf springs and 1.26" torsion bars
[Re: Viol8r]
#1485527
08/18/13 07:29 PM
08/18/13 07:29 PM
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Joined: Jan 2003
Posts: 27,467
So Cal
autoxcuda
Too Many Posts
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Too Many Posts
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Posts: 27,467
So Cal
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Quote:
Let's also remember what drives a lot of the aggressive set ups then and now..... grip. Most of us are not running slicks all the Way around.
I believe Docford is building a track dedicated racecar. He may be replicating the 1970 race AAR cuda that was taken to France and run with a Hemi at one point?
I thought Firm Feel makes or partially makes their own Torsion Bars. They do not make their own Leaf Springs.
There are sources for custom Torsion Bars. Sway-A-Way, Speedway Engineering. I think I asked Shroader and there equiptment would not handle the length. You've got to be able to machine stock at that lenght AND heat treat at that length. The oven at that length is the tougher of the two.
There are custom road racing leaf springs made up for the Vintage Trans Am guys. So need to find their source.
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Re: 230 - 260 leaf springs and 1.26" torsion bars
[Re: docford]
#1485528
08/19/13 09:19 AM
08/19/13 09:19 AM
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Joined: Feb 2010
Posts: 1,645
Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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Caution with respect to the Stock Car bulletin is warrented. There are several reprinted in the DC Oval Track book (P4286727) but the focus was definately circle track. In many chapters they specify "Super speedway", "Grand national" or "Short track" recommendations. The only area I can help with is the "Handling Line". The "Neutral Line" also appears in Mike Martin's book. (see "Suggested Reading for Handling") But it appears to be the same as the one emperically derived from short track cars (see: DC tech bulletin 141 "Basic Chassis Setup for Short Ovals). It is my conclusion that the concept is useful but the exact position of the line is not (except for the specific racing it was made for). My conclusion is based on (a) the weights, spring rates and anti-roll numbers published for production Barracudas (A & E), and (b) my own and other mopax set ups for competition (mostly autocross). In summary, the slope is appears to be universal, but must be shifted left or right depending on the application. Details on my Neutral Line page. I can not help as to where to get t-bars larger than 1.24, but obviously they were available for circle track at one time. (The sources listed in Martin's book were dead ends 15 years ago.) However, it is true that Firm Feel is making their torsion bars in-house. I've never seen the tech specs on the Chrysler France race cars. The photos show a lot of body motion compared to the US trans-am prepared cars. This may be due to rules or other limitations, or the need to compete in hill climbs and other open road events where a reasonable degree of off-pavement performance and ground clearance was needed. As far as 230# leaf springs go, that should not be too hard to find. Either of the big two circle track spring companies shpuld be able to make up a set. This may be the cheapest for testing rates and arch etc. Eaton will of course be willing to make up a more sophisticated stock type spring pack (6-7 leaf) with a primary and secondary leaf of the thicknesses, shape, for your needs and a final ratio and rate you want.
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Re: 230 - 260 leaf springs and 1.26" torsion bars
[Re: Mattax]
#1485529
08/19/13 12:10 PM
08/19/13 12:10 PM
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Joined: Jan 2010
Posts: 1,442
NW Chicago suburban area
Mopar Mitch
pro stock
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pro stock
Joined: Jan 2010
Posts: 1,442
NW Chicago suburban area
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I'm not certain of the exact specs, but I believe the factory-race T/A and AARs were running ~1.30 or a little larger TBs for the TransAm series (then and now with the vintage race events), as well as with the C-body anchors front and rear.
Their front sway bars are massive and tubular of the nascar-track types. Their rear sway bars are fairly small (maybe 1/2-5/8", and adjustable) and anchored low on the frame rails instead of high as we have factory-stock locations.
Their rear leafs are very stiff.. and with many leafs... I'll try to post some pics later as I have them from both cars (T/A and AAR) as seen at road race vintage events over the recent years. Their leafs are near flat at rest, and it wouldn't surprise me if their leafs are about 300-325-350 per inch. I know of SCCA C/P autocross cars that have run leafs that stiff.
Mopar Mitch
"Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers!
Check out MOPAR ACTION MAGAZINE, August 2006 issue for feature article and specs on my autocross T/A!
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Re: 230 - 260 leaf springs and 1.26" torsion bars
[Re: TC@HP2]
#1485530
08/19/13 05:13 PM
08/19/13 05:13 PM
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Joined: Aug 2010
Posts: 208
Munich, Bavaria
docford
OP
enthusiast
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OP
enthusiast
Joined: Aug 2010
Posts: 208
Munich, Bavaria
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Quote:
... However, if you really have everything speced around that, talk to Dick at Firm Feel and see if they could whip up a one off set at 1.24, which, coincidently, is the biggest you can put in the factory E body sockets. To go bigger, you need to convert to C body sockets.
Also, are those rates you have calculated including sway bars at all? ...
yes, I did factor in the sway bars and converted it all to wheel rates.
Thanks for your advice. I'll get in touch with Dick Ross at FirmFeel and see if he can make me a pair of 1.24" torsion bars.
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Re: 230 - 260 leaf springs and 1.26" torsion bars
[Re: docford]
#1485531
08/20/13 10:21 AM
08/20/13 10:21 AM
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Joined: Nov 2008
Posts: 1,491
Lethbridge, AB, Canada
dangina
pro stock
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pro stock
Joined: Nov 2008
Posts: 1,491
Lethbridge, AB, Canada
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Quote:
yes, I did factor in the sway bars and converted it all to wheel rates.
Thanks for your advice. I'll get in touch with Dick Ross at FirmFeel and see if he can make me a pair of 1.24" torsion bars.
let us know what he says - I'm curious about this as well
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Re: 230 - 260 leaf springs and 1.26" torsion bars
[Re: docford]
#1485535
08/22/13 10:48 PM
08/22/13 10:48 PM
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Joined: Feb 2010
Posts: 1,645
Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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Quote:
OK, I'll let you know. Right now it looks like 1.24" torsion bars without hex offset, because otherwise the car sits too high with such stiff springs.
depends on the nose wieght, but generally I agree. 1" and even a little bigger generally can use some offset, but 1.14 up generally not needed. Again, depends on weight and assuming no other mods.
Quote:
On the rear, it should be 6 or 7 leafs to get the desired spring rate. Spring arch needs also to be factored in, as well as standars eye or reverse eye option.
Number of leafs is not the only way to skin the cat. You can pick up off the shelf circle track leaf 'mopar style' springs with 4 leafs with 200 and more lbs/in. Landrum and Afco are two well known manufactures.
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Re: 230 - 260 leaf springs and 1.26" torsion bars
[Re: jcc]
#1485537
09/07/13 07:52 AM
09/07/13 07:52 AM
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Joined: Aug 2010
Posts: 208
Munich, Bavaria
docford
OP
enthusiast
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OP
enthusiast
Joined: Aug 2010
Posts: 208
Munich, Bavaria
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Quote:
Quote:
I have to wonder if those rates are predicated on have a lot of down force at speed. I have vague recollections that on the winged cars running back then down force was a substantial factor and the spring rates took that into account.
In 1971 stock cars, wasn't track banking a much larger factor then aero on spring rates? I never thought they achieved HIGH downforce, just a huge improvement over the huge lift demons from previous years, speaking in 1971 terms. 
That is correct. I do have some downforce and drag numbers from the Chrysler wind tunnel of 1970. It loks like the engineers where much more focused on optimizing drag than tuning in more downforce back then.
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Re: 230 - 260 leaf springs and 1.26" torsion bars
[Re: TC@HP2]
#1485538
09/07/13 07:59 AM
09/07/13 07:59 AM
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Joined: Aug 2010
Posts: 208
Munich, Bavaria
docford
OP
enthusiast
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OP
enthusiast
Joined: Aug 2010
Posts: 208
Munich, Bavaria
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Quote:
Hotchkis uses a drop eye arrangement with the front eye in their leaf spring kits.
Drop hangers can eliminate blocks too, but blocks can also be used to fine tune roll center height. Moving that front mounting point and the intersection of the eyes can have slight impacts on geometry if your trying to optimize things.
Good point ! We do have two monting positions on our front leaf spring hanger and four on the rear.
I'm not really a fan of reverse eye springs on a racecar, as the leaf is the "pulling" on the eyes and not "resting" on the weight of the car.
However, here is an interesting picture of the leaf springs on Richard Petty's 1968 Roadrunner.
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Re: 230 - 260 leaf springs and 1.26" torsion bars
[Re: docford]
#1485539
09/07/13 12:39 PM
09/07/13 12:39 PM
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Joined: Jan 2010
Posts: 1,442
NW Chicago suburban area
Mopar Mitch
pro stock
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pro stock
Joined: Jan 2010
Posts: 1,442
NW Chicago suburban area
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One additional concern should be, if the front spring eye location is changed up/down then to use angle shims at the leaf/differential to re-adjust the drive shaft / pinion angle.
Mopar Mitch
"Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers!
Check out MOPAR ACTION MAGAZINE, August 2006 issue for feature article and specs on my autocross T/A!
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