So, as my first post to the site - Does anyone know the technical reason that E Body rear leaf springs are angled outward at the rear? The fronts of the leaves are 3 inches closer together than the rear.
Robert
No. That's what I'm curious to find out. I can't think of a reason and I'm an engineer.
I have the Challenger up on its side on the overturning fixture and I just measured the distances. The center to center of the front hangers is ~45 inches, the C to C of the rear hangers is ~48-1/16 inches.
I just looked in the 9th ed. of the DC Chassis book, and it shows that the E body springs are angled outward toward the rear by 1.67 degrees.
Something I just read that I didn't know was that 71 and later B bodies are angled inward toward the rear by 0.61 degrees. And F Bodies have springs angled outward 0.85 degrees toward the rear.
A bodies and pre-70 B Bodies have parallel springs.
Robert
Do you think it could have been a by-product of a floor / seat design need and the small amount of angle was within a specification that would not affect the overall function of the spring? :notsure: Just guessing? They must have done it for a reason, right?
:popcorn: :popcorn: Always wondered about that.
Quote from: Cuda Cody on April 15, 2017, 03:49:42 PM
Do you think it could have been a by-product of a floor / seat design need and the small amount of angle was within a specification that would not affect the overall function of the spring? :notsure: Just guessing? They must have done it for a reason, right?
I hope so. I'd hate to think that someone put a crease in a final assembly drawing and didn't catch it until it was too late to fess up to management. But you never know.
Bob
I believe it has to do with helping to keep the rear end centered in the chassis when cornering. Sort of like what a panhard bar does.
" installed rate is another rate all together. The installed rate is the rating of the spring as it is positioned within the chassis itself. Leaf spring rates can be increased or decreased based on the mounting positions and angles. For example, when the leaf springs are toed in (the front eye locations closer together than the rear mounts) the lateral rate or twisting resistance is increased, therefore one's side bite rate is increased."
https://landrumspring.com/technical/leaf-spring-technical-information/
The quote is from the link article.
I don't know the answer just found this info.
If I remember right , the Dodge pickup I rented in Nov had a panhard bar and it really handled well driving on the Colorado mountain roads.
My 59 Chevy Belair also used it.
I think it was a little of both. The tail of an E-Body is a little shorter than a B-Body and they probably spread the rear rails to get a big enough gas tank in and fit the exhaust. It would also serve as almost like a tri-agulated four link does. Mike
Quote from: 73440 on April 16, 2017, 06:39:10 AM
" installed rate is another rate all together. The installed rate is the rating of the spring as it is positioned within the chassis itself. Leaf spring rates can be increased or decreased based on the mounting positions and angles. For example, when the leaf springs are toed in (the front eye locations closer together than the rear mounts) the lateral rate or twisting resistance is increased, therefore one's side bite rate is increased."
https://landrumspring.com/technical/leaf-spring-technical-information/
This is the answer as to why. I'd also add that the wider the springs, and the wider the mounting position on the axle, the greater the the resistance that can be achieved with a lower actual rate so you get improved performance without a compromise in comfort.
The '71-79 B bodies and '76-80 F bodies were splayed the opposite way for the same reason. A bodies never got it because they were going away in '76.
Don't forget, the 71 B bodies were late to market. They were originally supposed to be '70 models to be released with the new E platform, but they were not ready.
I have never seen an explanation however my theory is to package the mufflers beside the framerails underneath the trunk. Maybe the blueprints for the front hangars were cast in stone and they moved the rears later to fit around the mufflers and tank. I like Brad's theory too. You really have to hand it to Chrysler Engineers of the day. Look at the bottom of a 70 Mustang or Camaro. Then check out one of our cars. Work your way back, superior torsion bar suspension with great for the day geometry. Great clutch and the strongest 4 speed in the Industry, 7290 U-joints and a big driveshaft, Dana 60 rear axle with super Engineered, bias leaf springs. 2 1/2 inch headpipes with a superior exhaust system. It sure makes up for the crappy door panels and not so hot side window tracks and mounting.
That's why I love Mopars.
Quote from: RUNCHARGER on April 16, 2017, 08:46:36 AM
You really have to hand it to Chrysler Engineers of the day.
They were on it. There is a lot more engineering in a pair of mopar leafs and their layout than initial glance would imagine. The anti-squat percentage, instant center location, leaf width, leaf alignment, leaf taper, leaf ends, leaf interliners, leaf mounting positions, check rate, installed, rate, spring rate, axle location, control ratio are all factors that make mopar leafs a lot more than simple buggy springs.
They sure were. Just hit the throttle on a 480HP Stock suspension GM or Ford, no comparison.
Quote from: 73440 on April 16, 2017, 06:39:10 AM
https://landrumspring.com/technical/leaf-spring-technical-information/
The quote is from the link article.
I don't know the answer just found this info.
This is interesting. Thanks. I'll have to do some math and see what the effect is.
Bob
Quote from: rftroy on April 16, 2017, 05:39:51 PM
Quote from: 73440 on April 16, 2017, 06:39:10 AM
https://landrumspring.com/technical/leaf-spring-technical-information/
The quote is from the link article.
I don't know the answer just found this info.
This is interesting. Thanks. I'll have to do some math and see what the effect is.
Bob
It reduces rear steer induced oversteer.
When a longitude mounted spring goes into a corner, the outside compresses and in the inside retracts. This has the net effect of shortening the inside wheelbase and lengthening the outside wheelbase which in effect, turns the rear axle towards the outside of the turn which loosens the car. Mopar's low arch design minimizes this motion and when combined with a splayed mount, reduce the roll oversteer effect which makes the corner turn in more linear.
Quote from: HP2 on April 17, 2017, 07:35:43 AM
Quote from: rftroy on April 16, 2017, 05:39:51 PM
Quote from: 73440 on April 16, 2017, 06:39:10 AM
https://landrumspring.com/technical/leaf-spring-technical-information/
The quote is from the link article.
I don't know the answer just found this info.
This is interesting. Thanks. I'll have to do some math and see what the effect is.
Bob
It reduces rear steer induced oversteer.
When a longitude mounted spring goes into a corner, the outside compresses and in the inside retracts. This has the net effect of shortening the inside wheelbase and lengthening the outside wheelbase which in effect, turns the rear axle towards the outside of the turn which loosens the car. Mopar's low arch design minimizes this motion and when combined with a splayed mount, reduce the roll oversteer effect which makes the corner turn in more linear.
When I did tech for circle track cars , All the street stock leaf spring cars ( GM's) always wanted Mopar spring set ups. ;) I never let them.... :)
Yea, not surprised, but its funny you called them out and prevented them from doing that.
In my oval days, our tech was the same way. I got around it and the whole stock mounting location thing by deliberately bending the main leaf so that acelleration torque would force the bend up into the the edge of the hanger and effectively take around 5" of spring out of the equation while radically changing the control ratio. When asked about it, I said it was the result of incidental contact and I hadn't gotten around to fixing it.
Quote from: HP2 on April 18, 2017, 08:59:48 AM
Yea, not surprised, but its funny you called them out and prevented them from doing that.
In my oval days, our tech was the same way. I got around it and the whole stock mounting location thing by deliberately bending the main leaf so that acelleration torque would force the bend up into the the edge of the hanger and effectively take around 5" of spring out of the equation while radically changing the control ratio. When asked about it, I said it was the result of incidental contact and I hadn't gotten around to fixing it.
Yep ,damaged in competition covers a multitude of sins! :D When I'd find something " questionable" I would often say " humm got bent in competition right?" Some of the more " thick" ones I'd have to repeat it 3-4 times before they got my drift. :-[ Around here it's 99% Chevy's , they were quite alarmed when a competitor built a Dodge. Street stock back then was for the most part "stock" parts, 2BBl carbs, .390/.410 valve lift Mopar was a problem as they never had cams with such low lift., The Chevy crowd was fine with Mopars going by them on the straightaways as they usually got it back in the corners..... until the Mopar guys started figuring things out.The internet sure helped with that! When headers came in I cautioned them to be careful what you wish for as a Chevy with headers would NOT be the same in a Dodge. But they ignored me. Then later whined/petitioned to add weight to a Dodge. ::)
Now 3 years after I left racing street stocks are called "super stocks" and people are actually spending 50k on a car, :bigmoney: how stupid is that! :pullinghair:
On a complete side not I was able to order new rear leaf springs right from dodge for my 71 cuda. Pretty cheap in my eyes. 120 Canadian a side