[cboy]

This midget racer from 1947 was at a car show last Sunday and I was fascinated with the front suspension set up...quarter elliptical springs and a top side control bar. Looked so clean and straightforward yet utilitarian.

The owner said the leaf springs were made by cutting semi ellipticals in half and then doing LOTS of grinding to get them down to this size. Anybody know of a source for narrow leafs like this at a decent price?

My thinking is this would make a nice appearing setup on a street rod. Anybody see potential problems, pitfalls, drawbacks on a street car? (Yes, I realize semi ellipticals are often used on street rods...asking more about the setup here with the upper control arm/lower spring physics.)

[John Wohlfeil]

Zipper, uses that type spring on his roadster! Zipper Motors Phone # 970-243-6558. The area code might be different now ??? 3w

[Chopt 48]

That is what is called a Quarter elliptic spring. It is actually a somewhat popular setup. I first saw it on all four corners on a T that a gent named Mike Minette, (spelling may be off) built in the early 70's in Texas.
here are a couple of photos of a T that was at the Run to Roslyn in Wa State two years ago.




I have no idea who built this car but the front end is pretty simple and wouldn't be expensive to duplicate. It appears to have a late 40's early 50's pickup front axle with brackets bolted to the original spring pads on the axle to connect the spring eye to. The springs are just as you mentioned above, springs cut in half. These may be 46/48 Ford pickup front springs cut in half.

[cboy]

Sorry if I didn't ask my question clearly enough. I wasn't asking what this setup WAS (it's pretty clearly stated in my first sentence that it's quarter ellipticals) nor was I asking if quarter ellipticals have ever been used on a street rod (fairly common as I also noted in my original post).

What I was asking about is the specific setup shown in the midget pictures with the spings under and the adjuster/controller bar over and whether THAT setup would work on a street car. For one thing, I'm wondering if the lack of any shackle or allowance for spring extension would tend to rotate the axle or cause binding during axle travel. Other questions regarding the geometry may arise as well. But that was the discussion I was looking for.

[dinger]

That's an interesting set-up. I was wondering if there is enough "give" to the springs to keep the tires firmly planted, would the frame bottom out if a guy hit a pothole or going down a steep driveway? Dan

[Chopt 48]

Oops, I guess I missread your first post sorry about that.

Anyhow that style of suspension doesn't use a shackle. the spring eye bolts through the brackets below the axle and acts as the bottom half of a 4 bar setup. The upper link has the same pivot track as the spring and is adjustable to adjust caster.

From admiring your work previously I can imagine you would find ways to clean up the setup for a very slick appearance.

I think it would work great with the proper spring rate and shocks for the application.

[OneMoreTime]

If you can imagine a four bar with one of the bars replaced by the spring then you have it.. WE do not use this in the sprint cars any more because of the need to be able to adjust spring rates to track conditions at times..Other than that it seems to work just fine..Takes a bit of engineering to make it work well..

Sam

[home brew]

For discussion purposes - some thoughts off of the top of my head.

That is a very interesting use of quarter elliptical springs. It seems the only reason for the top bar would be to adjust the angle of the axle; but there would be no triangulation for the axle to stop side to side motion as in the use of four bars or stock/split/hairpin wishbones. I know that the early 20's Chevy's didn't use anything other than the spring to attach the axle to the frame but it was built with a slight angle to the frame not parallel to it like this midget. They also didn't use shackles to mount the spring to the axle. I would think this type of setup would place a lot of strain on both the control bar and the spring mounts on the axle. Maybe going around in a circle only one way would not subject the system to the same stresses of the street. The solid mounting of the spring as part of a four bar setup would also make it act a bit like a torsion bar so maybe that would take the strain off the mounts. But then again the need of the spring to return to its original shape while being twisted might create quite a loss of stability on the street when the tension was released and it returned to its normal position.

[cboy]

Originally Posted by OneMoreTime

If you can imagine a four bar with one of the bars replaced by the spring then you have it...

Sam,

Following up a bit on Brew's comments, I'm wondering if it truly IS like a four bar. The main difference I see is the with the quarter ellipticals, two of the bars are designed to flex...probably by 1"-2" in each direction measured at the tip of the spring. In a 4-bar setup, none of the bars flex.

Won't this flexing or bending of the lower bars on the midget setup cause the attachment point to lengthen and shorten as the length of the lower bar (the spring) is lengthened and shortened during the bending action? And the axle itself is prevented from twisting or rotating to accommodate that movement by the upper rigid bar. I'm just wondering how much actual travel you could get on that front axle before it it would bind up.

The other difference I see between the midget and a 4-bar, is that with a 4-bar all four bar ends are designed to pivot so that the bars can always remain parallel. In the midget setup there is one bar end (the frame mount for the elliptical) that is rock solid. To me this would change the entire dynamic of a 4-bar system if any one "pivot" was suddenly welded solid to the frame or to the axle.

Obviously the system works, at least for this type application. But does it really follow the rules and design principles of a 4-bar setup?

[OneMoreTime]

I do not think the bending of the spring would create enough of a difference in length to make much difference..Now when you are running on a dirt track things do tend to get bouncy so it might be hard to tell..WE do live with some deflection in the conventional spring layout so I do not believe it woudl be a great issue..If the springs are mounted directly to the axle with just a pivot point there may be enough resistance to side to side movement to be OK..We live with conventional springs with no panhard all the time..

Nice clean looking setup though..only way I know to prove it out is build it and try..Make your sacrifice to the Hot Rod gods..

Sam

[robin58]

Originally Posted by home brew

but there would be no triangulation for the axle to stop side to side motion as in the use of four bars or stock/split/hairpin wishbones.

I thought that too but then in looking at picture #2 I wasn't sure whether the bar from the top of the mount on the axle maybe was intended to serve that purpose? I'd assume there'd be a similar one on the other side which would theoretically hold the axle in the same place crosswise. Of course I might be looking at something completely wrong.

[oldbogie]

Originally Posted by cboy

Sorry if I didn't ask my question clearly enough. I wasn't asking what this setup WAS (it's pretty clearly stated in my first sentence that it's quarter ellipticals) nor was I asking if quarter ellipticals have ever been used on a street rod (fairly common as I also noted in my original post).

What I was asking about is the specific setup shown in the midget pictures with the spings under and the adjuster/controller bar over and whether THAT setup would work on a street car. For one thing, I'm wondering if the lack of any shackle or allowance for spring extension would tend to rotate the axle or cause binding during axle travel. Other questions regarding the geometry may arise as well. But that was the discussion I was looking for.

Yes, it will work fine. The upper control arm takes the front to rear axle locating load off the spring and between the spring attachment and control arm attachment the longitudinal roll center of the axle is maintained, this is the same thing the wishbone in some of the other pictures is doing with an additional piece of structure. Either way works, you just have to be careful to keep the rotation centers of the spring and control arm in the same plane so that the axle isn't pulled, pushed, or rotated as the tire moves it up and down.

Bogie

[cboy]

Originally Posted by robin58

I wasn't sure whether the bar from the top of the mount on the axle maybe was intended to serve that purpose?

I believe that top bar (arrows) is the friction shock.

It is not attached to the axle, just rides on top as I recall.

[azlogger]

i realize i'm bringing an old, dusty thread down from the attic, but i am just wondering if anyone sees a serious problem with this setup for the drive axle. Will the throttle/ braking torque cause the car to ride up or down because of the extending of the spring? this will also cause the pinion angle to change a little...

[OneMoreTime]

it will work fine on the rear..just look at how you make the control arms so the pinion angle does not change all that much..

Sam