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 Post subject: Rear Springs?
 Post Posted: Mon Mar 16, 2009 6:03 pm 
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I'm thinking about replacing the rear springs on the Studebaker and was wondering if anyone knew of a spring rate chart online? That thing has 1860lbs on the rear tires so it's going to take a pretty stiff spring.

I'm thinking about getting a pair of AFCOs for the Camaro and if I do, I'm going to put the QA-1s that are on the Camaro now on the rear of the Stude so I might as well replace the springs while I'm at it.

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 Post subject: Re: Rear Springs?
 Post Posted: Mon Mar 16, 2009 7:14 pm 
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Ken, I gave John the #s he needed to figure the weights for my car and he was inside 25lb on his figures!!!

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 Post subject: Re: Rear Springs?
 Post Posted: Mon Mar 16, 2009 9:13 pm 
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Cool another calculation post =; =; Ken, I can work up a spring rate for your car tomorrow and I can pm you with the info I need besides the total rear weight you have now to get as close as possible, (and that was 18 lbs Barry I got within of your actual spring you had in it from 170) ;-) ;-) , but doing the math was fun and easy with all the numbers. Let me know Ken, I would be glad to help and learn as we go, neat stuff too, and I can lay it all out for ya to see how I figure it.

John

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 Post subject: Re: Rear Springs?
 Post Posted: Mon Mar 16, 2009 10:26 pm 
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I don't have scales to give more weight info. The rear weight number I posted was from the NHRA scales down at Dinwiddie a few years back. Total car weight with me in it that day was 3459lbs and that was with aluminum heads on that engine but they are cast iron now. So, the car is actually heavier now than it was back then but I don't know by how much.

I got no clue what is on it now but I'd venture to guess that I'll need something in the 180 to 200lb range. Rear weight on my Camaro is 1200lbs and I got 125s on it.

So what other info do you need?

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 Post subject: Re: Rear Springs?
 Post Posted: Tue Mar 17, 2009 8:12 am 
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Ok Ken here we go, and we really need to have access to scales, but we can get you real close without from what we have, and I will let you know WHAT we need if we need it, ready?


Info needed to find your lever ratio per your suspension, and shock length needed, the #3 measurment will need to be with the car on the floor, or on boxes so you can get under car to mesasure in case your fat like me =;

1. rear axle type used
2. Distance of shock off car, fully extended(eyelet to eyelet)
3. Distance of shock on car loaded-race ready(eyelet to eyelet)
4. 4 link or ladder bar
5. Measurement from front mounting point of ladder or lower 4 link bar to axle C/L
6. Measurement from front mounting point of ladder or lower 4 link bar to lower shock eyelet
7. shock angles if any, how many degrees and which direction, angled in/out, or front/back.

Now, with this info, I will be able to find out your sprung vs UNsprung weight for your setup, your lever ratio of your suspension, and your travel of your shocks that should be correct for your chassis ride heigth.

Since we don't have actual weights of the rear axle components, I will use average weights per gathered info from the same applications as yours, but without the EXACT weights, this is where we will only get real close and not exact, sorry, but scales really make the choice of spring that fined tuned variable. If, you have a bathroom scale, and feel like taking components off the Stud, we could get a little closer as well, and here is what we would need weighed;

1. wheel & tire combined
2. shock & spring
3. complete axle with shafts gears yokes and no brakes
4. brakes
5. wheelie bars
6. all hardware also needs to be measured to get a total more precise.

Basically the complete rear suspension seperated from the chassis and driveshaft, and brake line. I know, what a pain right? you may have no idea the actual springs needed for your setup and if you want to be like the average racer and have sets of springs in the garage, feel free to go alone on this, but we can get you pretty darn close to knowing exactly what you need and to get the right spring for you.

I will also show you the calculation I use and break it down with your info to see how the math plays out for your spring rate needed in the end. So, looks like your off to the garage for a little while and let me know when you have the info. ;-)

John

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 Post subject: Re: Rear Springs?
 Post Posted: Tue Mar 17, 2009 9:19 am 
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Ah........I think I'll just use the ones that are on there now! Dayum, I got a brain cramp now! Seriously, I got no way to get all these dimensions and crap cuz I don't have any way to get the car up so I can get under it and take all those measurements.

Thanks but I'll pass this time. :-k

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 Post subject: Re: Rear Springs?
 Post Posted: Tue Mar 17, 2009 7:45 pm 
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What's on there now?


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 Post subject: Re: Rear Springs?
 Post Posted: Tue Mar 17, 2009 9:35 pm 
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Scott Smith wrote:
What's on there now?


That's the problem. This car was built back around 1990 from a chassis kit that I purchased from Chassisworks out on the left coast. In short, I got no clue and I don't remember the springs being marked so I could find out either.

I did find a chart on Chassis Engineering's website that say 200lb for a total rear weight of 1700 to 2000lbs, which might be close as the weight of the Camaro (1250 or so) they call for a 130lb spring and I put a 125 on there that works. So, iff'in I had to make a "calculated guess" I'd say that the 200 would work, ya think?


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 Post subject: Re: Rear Springs?
 Post Posted: Wed Mar 18, 2009 4:53 pm 
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I have seriously thought about 4 link geometry for many years. I noticed that the fourlink programmes available did not agree accurately with the data logger suspension movements and other data from our race car so I developed my own physics analysis programmes based upon the force vectoring. This programme is accurate to the data. If you do this yourselves you will arrive at the conclusion that the 4 link is incorrectly described in literature. It is well worth the effort to write a spreadsheet of all the forces and how they interact. The first thing that becomes obvious is that the 4 link is not the same as a ladder bar of equal instant center location. The instant center concept is the common held view of how a four link works, in fact the four link doesnt actually interact through an instant center. By using a spreadsheet and the function of circular referencing you can write the math of how the four link forces move with the reactions of the suspension etc. Its very interesting to do.
The various methods described of how to measure and predict factors like anti squat and torque lift etc are mostly inaccurate and sometimes plain incorrect. They may be useful methods to convey an initial concept to a beginner but if one seeks correct understanding of the physics exerted in a four link and the subsequent ability to be able to use that understanding to enhance performance then one needs to fully breakdown the forces.
On the subject of this thread when you install higher rate springs in the rear the fourlink movement range is restricted. If you used infinite hard springs ( like a solid rod) then there will be no four link reaction at all. The most influential bar in a four link is the lower one. The lower bar has compressive torque reaction load plus compressive acceleration reaction load. So small changes of the angle of this bar have reasonably large effects upon tyre loading. The other important issue is the mounting location of the upper bar Diff point. Moving this point forward and backward in a horizontal plane has large effects upon the upward force reaction of the top bar. The top bar has tension loading from the torque reaction and compression loading from the acceleration force. In some designs the top bar has zero load under acceleration.
So when you change the ride height you change the bar angles and the reactions, when you change the spring rate you change the bar angles under the dynamic situation of acceleration weight transfer etc. Some of the cars weight transfer is reacted through the four link to the diff and some is done via the springs. It depends upon the four links geometry and the cars Center of Gravity location etc as to what wins, the four link or the spring. Change the tyre pressure, alters the angles, its amazing what happens when you correctly work it out.
I will try to describe a new way to make you think about how a four link works. Basically what a four link does (that doesn't seem to be how the literature etc describe it) is it tries to move the chassis attachment in a particular manner. It tries to rotate and or lift etc that piece of chassis that its attached to. That piece of square tubing or whatever you have between the 2 front mounts gets shoved somewhere and the sprung mass of the car then reacts to that force and has a movement etc visible in the springs. So if you were to visualise what would happen to your car if you got under it and wrenched that piece of chassis around in the manner that the four link does then you will have a different perspective on how the four link works. The forces going down the bars don't magically intersect at the instant center and lift the car from there, they don't form any form of line of force to the tyre patch from the instant center, they don't need to intersect at the camshaft or some other accepted point on the car. the piece of chassis just has to be manipulated such that the vehicle maintains control dependent upon it's weight, distribution, power and available traction.
I rarely discuss this subject as it seems that I fly in the face of fully accepted convention. So comment constructively if you will. regards Shrinker


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 Post subject: Re: Rear Springs?
 Post Posted: Wed Mar 18, 2009 5:51 pm 
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Ken0069 wrote:
Scott Smith wrote:
What's on there now?


That's the problem. This car was built back around 1990 from a chassis kit that I purchased from Chassisworks out on the left coast. In short, I got no clue and I don't remember the springs being marked so I could find out either.

I did find a chart on Chassis Engineering's website that say 200lb for a total rear weight of 1700 to 2000lbs, which might be close as the weight of the Camaro (1250 or so) they call for a 130lb spring and I put a 125 on there that works. So, iff'in I had to make a "calculated guess" I'd say that the 200 would work, ya think?


Ken very simple to see where you are.

Put a bathroom scale on your drill press table. Set the spring on top of the scale. Put a block of wood on top of the spring large enough to cover the foot print of the spring. Pull the head of the drill press down and compress the spring 1".
Read the scale. :-$ ;-)

if the scale says 200 it's a 200# spring.
If the scale says 150 it's a 150# spring.


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 Post subject: Re: Rear Springs?
 Post Posted: Wed Mar 18, 2009 5:57 pm 
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Scott Smith wrote:
Ken very simple to see where you are.

Put a bathroom scale on your drill press table. Set the spring on top of the scale. Put a block of wood on top of the spring large enough to cover the foot print of the spring. Pull the head of the drill press down and compress the spring 1".
Read the scale. :-$ ;-)

if the scale says 200 it's a 200# spring.
If the scale says 150 it's a 150# spring.


And how accurate will that be with a spring that has been under that 3500lb car for 17 years? O:) ;-)

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 Post subject: Re: Rear Springs?
 Post Posted: Wed Mar 18, 2009 7:35 pm 
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Well you will know where you are currently.
The scale wont lie.


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 Post subject: Re: Rear Springs?
 Post Posted: Sat Mar 21, 2009 8:08 pm 
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This kind of depends on the shock length and a few other things. But I would probably be looking at about 150#-170# springs. If you go with the 150s I think they will crush about 4 inches to ride height. They ought to help out pretty good with chassis seperation on the rear. JMO,... for what it's worth. ](*,)

Don

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 Post subject: Re: Rear Springs?
 Post Posted: Sat Mar 21, 2009 8:58 pm 
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John,

If you're wanting to talk about this some time let me know. I don't use much math to pick out my spring rates. I was taught by some pretty talented guys on how to make these choices. But I'm not near as good as they were... :---)


Don

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 Post subject: Re: Rear Springs?
 Post Posted: Sat Mar 21, 2009 10:15 pm 
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Hey shrinker, that was good for part 1, please keep going.

Coy

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