quarter elliptic rear suspension

I did a search on quarter elliptic + rear suspension and checked all of the 19 matches... but none answered my questions.

It seems everyone using 1/4 elliptics clamps the springs to the frame and connects the spring eyes to the axle. Has anyone clamped the springs to the axle housing (like a typical leaf spring suspension) and whacked off the part of the spring pack that projects behind the axle? Of course, two links would be needed to prevent the whole assembly from rotating around the spring eye... I guess it would look something like the attached sketch. Anyone have experience with this?

 

The u-bolt isn't a joint but rigidly mounted, so as you have it drawn, it will bind.

Edit: If the spring and upper link are parallel then I don't think it will bind. But I don't think that it's a good idea.

 

i started to say......the way its pictured.....the chopped springs would act as a lower link ....but wouldn't provide any spring ....then i thought about it some......seems like the top link would make the spring pack act as a spring to a degree....by forcing the spring to arc in order to keep moving ....seems like it would really make the pinion angle fluctuate....as the spring would flatten out....just thinking out loud....brandon

 

Use a shackle on the spring, and use a four link to locate the axle. In other words don't try to use the spring as a link.

 

Wouldn't that just act like two parallel swing arms, one on to of the other? What would prevent it from bottoming out against the frame?

 

i think it would depend on the quarter elliptic....if its arched it would move in a different arc than the top bar....til it was put into a bind ....then the spring would seem like it would flatten out ...seems like it would be a lot of movement....and not much spring .....brandon

 

77 your right its just going to pivot(?),

 

Yes, from the standpoint of keeping pinion angle relatively constant over the range of travel.

However the leaf springs have to be flexed for the axle to move up and down... like a normal leaf spring suspension. That keeps it from bottoming out.

 

Only if you tighten the bolt for the spring eyes really hard!

Take a long look at the sketch and you will see why i dont work!

 

That setup aint gonna hold nothing up.GREGG

 

As drawn, you'll car will pretty darn quickly drop flat on its butt. There will be some springiness, but not much.

If you want this design, I'd recommend having a long moment arm -- the distance between the centerline of the rear axle and the top pivot mount on top of the axle housing. It looks interesting. Try tacking a few things together and see how it sits and bounces. If I had to guess, I'd start with at least a foot and a half.

EDIT: I was awake thinking about this last night. I now don't think it will drop to the ground right away. It looks intersting.

 

In the sketch, the spring isn't a spring, just a complicated link. Turn the spring end for end, anchor it to the frame, and it will work. Don't forget a panhard bar. I'm building one like that right now. You can use a shackless spring if the spring and link are parallel and the same length. I did a front that way a few years ago too. Works fine.

 

it would work if you reversed the spring. the pack has to be mounted to the frame in that situation. I think?

 

The vehicle would have to be pretty heavy to get that stubby leaf to go into a compression arc and stands a fair chance of shearing off the mount. If that spring eye can't pivot you'll have suspension travel until it binds and then you'll have failure. If I'm looking at it correctly. It's a neat idea, I like it when people look at something that's been around since horse and buggy days and come up with something new. However, I don't think this one will work.

 

this is the way i have seen it work

 

What do you expect to gain by doing it this way?

 

http://www.rodandcustommagazine.com/featuredvehicles/0509rc_1929_ford_roadster_pickup/



See if you can get to this site. It's for Pinkee's 29' roadster pick-up. It has a drawing of the design they used on the back end suspesion. It looks like what you want to do. This was a VERY well done car, so if you copy them I would think it would work great!

 

PM member Mr. Mac - he has a quarter ellip set up on his T Sedan.

J.

 

I have built 6-7 1/4 elliptic rear suspensions using the springs with a shackle on the axle and ladder bars. this works excellent. But in 84 I did a 32 roadster with the spring as the top 4 bar and a pair of lower bars mounted like conventional 4 bars. I mounted the spring eye on the axle and the front of the spring to the side of the rails. Also used a panard bar. I see this car every year at the LA Roadster show, it has over 100K on it with the same suspension.

 

Eliminate the rear spring shackles and perches (and gas tank too) that stick out beyond the back of the body. I don't like the way they look. The attached picture is not my car, but the exact same year and model.

Additionally, I think that it will allow for adjustments to the Instant Center (for drag racing purposes).

 

Thanks for the link, but it had no pictures nor drawings. From the text, I couldn't tell how it was done exactly. Anyone have a copy of that article available?

 

There were no shackles on that car's rear suspension, right? If so, that's the closest thing yet to what I am asking about here.

The difference was I wanted the spring to be clamped to the axle instead of the frame for two reasons:
1.) easier since the axle alreay has perches on it
2.) simpler to allow for adjustment to the Instant Center

 

Doesn't it seem like if the pivot of the spring was on the front like you have it shown the spring would act similar to a lower control arm. But since it is a spring and the upper keeps the axle from rotating (as it would in a control arm setup) that it would put the upper link in compression. It doesn't seem like a very good idea.

It seems better to do it how I have seen it before, with the fixed end of the spring at the frame and the pivot at the axle.

I didn't really think too much about it with my first comments. But it seems like it wouldn't bind as it is drawn, but I think it would put a large compression force on the upper link, which is not a good idea.

 

I'll second that.

Leaf link suspensions were once the rage and even found there way into OEM useage...the 2 seat AMX being one example.

But with the use of a leaf (even a 1/4 elliptic) comes the problem of distortion under acceleration. The spring just doesn't have the stability to absorb the extreme forces of hookup and goes S shaped, causing wheel hop and self steering.

If your car has a strong enough engine to need easy adjustment of instant center etc on the 1/4 mile...then spend a couple of bills on a 4 link and do it the right way.

BTW...being able to reuse two little spring pads on your back axle is a very poor reason to redesign a proven suspension.
My feeling is you MIGHT get it to hold the car up, but it will be HELL on suspension bushings due to leverage forces being applied thru the arms at all times.

 

If you are set on mounting the spring to the axle, I believe you'd need to put a shackle between the frame and the spring eye(to get rid of compressive load on the spring eye bushing) and then run conventional 4 link or radius rods. 54chop

 

I'll have to nab some current pictures as we don't have shocks mounted here.


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I edited my previous comments. Now I'm thinking about it again and it looks like there is the potential for more unsprung weight with the new design than with the conventional quarter-elliptic.

I like the design in that it is pretty creative and has a weird twist to it. But in my gut I think there may be issues.

If you go ahead with it, good luck and post your pics and observations.


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It won't work

When the spring mounted solidly to the axle it will act on the axle as a lever and apply a torsional force on the axle. If there was 600 pounds of weight on each side of the axle and the spring was 2 feet long you would have 1200 ft/lbs of force at each end trying to twist the axle and it would probably break the housing or the upper link as soon as you set the car down.

When the spring is mounted solidly to the frame the same kind of forces are applyed to the frame which is why the spring mounts need to be well thought-out and well built. Using the shortest spring possible also reduces the leverage that the weight has on the frame.

At least that's how I see it...

 

Sorry Dodgeboy but your idea will not function as pictured. As most of the past posts have indicated you have a few flaws in your idea. Rather than just say it wont work, here is an explaination of why and you can revise your idea.

As others have pointed out, this really isn't a suspension system, you are not suspending anything you have just drawn a series of rear axle locator or anchor points.

Let's break this down a little starting with the spring. The way you have it now it is not a spring, it is just a control arm with a couple of flat spacers added. To be a spring it must support something. At this time it supports nothing and will merely pivot around the frame mount. The addition of the upper control rod just duplictes the lower control arm with a different radius. Neither of these actually support the chassis. What makes them appear as a parallel setup is misrepresented. Since one locating point is fixed (spring at axle) they can not operate on parallel arcs. They are control arms that operate on different arcs and create a bind. That stress probably would be transmitted to the uppper control bracket weldment on the axle tube and it would eventually fail. The only reason that it would appear to suspend anything is that in any other positon it would be all bound up and ridgid.

Now there is nothing wrong with 1/4 elliptical springs and to those of you who think I'm over critcial on "dumb ass" ideas here is a suggestion on how to maintain this setup.

If you really want to attempt this setup and drag race, it probably wont work well but that is your choice. First you are going to have to make it a suspension system. To suspend something you are going to have to support it. Right now you have no support.

Here is how to get it to work. Lets start by removing the upper link. With the lower spring/contol arm at ride height, you are going to have to position a heavy bump stop bracket that will control the movement of the spring upward. This bracket should be installed inward on the spring about 4" from the end of the spring eye. A more elaborate set up rather than just have the bump stop hit the spring, would be raise the placement of stop bracket up the frame rail and about 2" above the spring. Drill a hole in the bracket and install a 3/4" diameter bolt in the stop bracket so that the head of the bolt contacted the spring. This enables the bolt to be adjusted up or down by using a jam nut to fine tune the ride height. The installation of this bracket would now support the weight of the vehicle and the flexiblity of the spring would give some suspension. Without knowing the weight of the car, the overall length of the spring would have to be somewhere between 18-20" to give you a adequate ride. In addition you would have to install a drop strap to control the drop of the rear axle if the vehicle was lifted from the frame and it wouldn't be a bad idea for a panard rod or sway bar.

The disadvantage of this setup is that as the suspension deflects, it deflects around the centerline of the axle. This deflection causes an excessive wrap to the axle which continually changes the pinion angle, this must be set to a compromise. What happened to the other control arm? Well you can't use it either on top or below the spring as the addition of the rod would eliminate the necessary bending of the spring which determines the ride. Because this bending continually changes the length of the locating points a fixed lenght rod would again create a bind conditon and end up braking something.

The improvement on this setup is here is best represented by the picture provided by "lindross"and Krylon" where the ridgid portion of the spring is reversed and mounted on the frame and combinded with a flexible mount on the axle. This allows for a smooth operation as the spring is able to "float" during travel eliminating any bind and a link style locater is used. The hair pin system pictured also creates a twist in the pinion angle but is minimized out with the use of longer arms. Hope this answers some questions.

 

Here is the drawing from the other site. We have given them their credits so I think it would be ok. This has the spring mounted at the right end and I think this has to be done this way for your idea to work.
The name on the drawing is Christian, and it is a beautiful piece of art.