More 1/4 elliptic rear suspension questions

G'day
I'm planning a small light vaguely lakes inspired T. I've looked at ways to get the chassis lower than traditionally but don't want to step the rear and have decided one option maybe rear 1/4 elliptics. I've searched the HAMB and I a question. Why do I need a shackle or an eye on the axle?
On the assumption my chassis rails aren't parallel so it tapers from front to rear about 6" if I ran rear 1/4 elliptics they would likewise be wider at the rear. Why can't I mount them fixed at each end without an eye or shackle. The vertical movement (yes I know the rear axle would be traveling in an arch) would be no different to so called NASCAR truck arms, the side ways movement would be contained by the splayed layout and any body roll would be minimized as the springs would twist and resist it. I don't think the springs would wind up any worse than a set up with top arms - I'm not planning any big power. I saw a pic of a '20's something Buick (?) that was not unlike what I'm proposing but it would have had a torque tube.
Cheers
Tony

 

I don't know if I could answer your question, but here is a 26 buick rear assembly.

 

And another. The buick mounting at the axle is a rotating unit that with the torque tube is needed, but with a u joint setup on your third member it most likely would not be needed. I am gonna use this same stock setup in the 26 but without a torque tube rear, but mount the spring on the bottom of the axle without the rotating part.

 

Here's a couple shots of the rear QE setup on my Roadster chassis.
I think it's similar to what you are talking about --- no shackles.










Malcolm

 

Malcolm. I really like that setup. CLEAN

 

you need the shackles due to the change in spring "length" relative to suspension travel... bind and broken springs will result otherwise

 

I'm going to try to prove you wrong... we'll see what happens

 

Two words TORSION BARS

 

i like what i see, and i really, TRULY hope i am proven wrong bud

 

I was going to suggest you Google Bugatti GP or Type 40 for a photo of their rear spring setup, then I looked at Malcolm's photos. That setup looks very much like a Bugatti only the springs are in front of the axle. Is there a build thread on that chassis? Really like the looks of the tube work. Bob

 

That may be why the Bugatti setup has an oval eye in the main leaf that allows the bolt to slide back and forth a good inch if memory is correct. They had a torque arm that ran from the center section of the rear to the trassmission to center things.

 

Here's my Speedcar with a set of splayed 1/4 ellipticals with the axle end free to slide in a containment open ended box which is built on to the radius rod which also terminates with the big end of a connecting rod that allows the axle housing slight rotation during travel.

This is a torque tube drive line and we have included a panhard rod as the springs are narrow and the cornering forces high.

We have also mounted the spring and special U bolts to a pad that has a short piece of sawed off torsion bar welded to the pad that passes through a bushed spud welded through the tube frame with a splined torsion bar stop on the inside of the frame to provide ride heighth adjustment.

Are you in the Barossa Valley?

 

it would work, and WELL, if and if... both the spring and the bar move in a parallel arc and hit the apex at the same instant... i cant tell if nicks is going to be like that at ride height or no...

if im wrong, i;d rather be told what the reality is so then i know more than i do now

 

28dreyer, that is the exact same design used on a Type 59 Bugatti, much better IMO that the earlier oval eyed spring hole. Ever see a Dreyer Wiggle Front End, with two long springs and Model T Ford axle parts?

 

This T modified was in one of the recent Rod and Custom issues. Here are the photos I took at the Yakima Vintiques run last year.





It does have shackles because it runs split bones and the shackles keep the spring from binding as they don't act as a lower half of a fourbar.

This is a different modified with quarter elliptic springs on the front.

OSLYN05RUN062.jpg[/IMG]

Ok, I've been wrong for the past 7 years, the black car does have split bones with the spring mounted without shackles. I always had it in my mind that it used something more like the lower half of a fourbar so the spring acted as the top half. I'm inclined to think that the spring might want to bind a bit on this one.
It will work fine the way Malcom showed with his but with the split bones like the two I showed going without a shackle would probably cause the spring to bind.

 

Just look at a 1959 Austin Healey Sprite rear axle assembly. They were 1/4 elliptic. One of the better road race designs ever. I am putting a version on my bobber. Works great for drag racing too...if you set it up properly

 

You only need shackles if the axle is located by other means.
Four bar, hair pins, triangulated 4 link, etc.

If the springs help locate the axle, with no binding,
you don't need shackles.

 

read my next post... explains my thought better

 

This is a Dreyer 1/4 elliptical front end on a mid 30's Big car but propably not what you are referring to. Don't see any Model T parts here.

Notice the straight tubular front axle ala today's sprint cars and midgets. I'm not enough of a Dreyer person to know when he might have started doing that and how long it might have continued.

 

Jaguar MK11 cantilever rear suspension the front half of the springs mount inside the chassis rails a bit smoother than 1/4 ellipticals due to longer effective length

 

Ever see a triangulated 4 bar, where the
upper and lower links are different lengths ?

How about a 3 bar, with a short upper link ?

Or a Torque Arm, typically longer than the lower links ?


Forget "parallel arcs and the apex" whatever that is.

 

imagine malcomes 1/4 elip. flattened out .........the length could change by over an inch....the top link isn't going to change ....pinion is going to move down when hitting a bump possibly when the drive shaft is level

 

G'day
I just had a read of your reply's and of my post again. What I didn't make really clear is by fixing the arm and both ends without a shackle or an eye I would be using the spring also as the only suspension arm - No top arm or radius rods. If you imagine the two link layout under a c10 pick-up or NASCAR but using the springs as the lower arms.
And to who ever asked I'm in the Barossa.
Cheers
Tony

 

Early Bug-eye Sprite setup, similar to what Tony just described:

 

Notice the upper and lower links are different lengths.

 

No parallel arcs and/or apexes.

 

I did a rear suspension like Malcolms in a deuce roadster I built back in the early 80s I used a 40 front spring split in half with the triangulated bars/no shackle and I see the car every year at the LARS and it's still going strong with about 150K on the speedo. I currently do the 1/4 rears with a Posie kit with shackles and P&J ladder bars and to date I haven't had the need to add a panard as the spring is captured in the bracket which prevents side movement.

 

Have you calculated how much that "change" in length actually is? I have, I think you are in for a surprise. I am doing basically the same thing (no shackles) but with the torque tube as the upper link. Guys always get lost in the engineering on here, and forget to do the math.

 

If the springs are relatively flat, the length change is nothing to worry about. I'd be real careful about the combination of a fixed mount on the torque arm and any serious arch in the spring pack. The torque arm doesn't work the same way as a set of upper links that will allow some pinion angle change....