Finished Quarter Elliptical Front end

I just finished the front end on my coupe. Quarter elliptical with posies springs. Made the top bars and had to improvise on the shock/ headlight bar.. I had to figure it all out on my own since I couldnt see and pictures besides jason grimes starting pictures. Posies had a truck but it didnt really show the front end components..

Good question on the upper bars and hairpins..I had to invert the bars for clearance issues since the frame is Z'd so much. The quarter ellipticals have to be in a 4 bar set up. The springs ae the 2 lower bars and you need 2 upper bars. The Hairpins keep side track and a good elipse arch to keep the front end stable..With a tube axle you need to be really critical of torque or you will crack the axle. An I beam axle would flex but I had the tube axle and ran it....

 

Why do you need Hairpins AND an extra top bar ?

Since the lengths are different, they will create a bind.

 

Because it has to be a 4 bar set up. The springs act a as the lower 2 bars and I needed 2 upper bars..The quarter ellipticals would sway if I didnt . With a tube axle they can crack unlike a flexable I beam..

 

They functioned smooth as silk. They are inward at 15 degrees to triangulate the front end.

 

i still see no reason for the upper bar with the hairpins. hairpins are flexible and work well with a tube axle. spring should be mounted with a shackle and use a panhard bar.

if spring is mounted to the axle with a bushing you could keep the upper bar and not use the hairpins.

 

The upper bars act as a panhard bar. Without it, the axle (and everything attached) could (and probably would) have side-to-side play.

But I agree with the others...springs anchored to the axle without shackles and the angled upper link arm makes it a 4-link setup. If you keep the hairpins, you effectively have an 8-link suspension.

 

Definitely overkill. My '32 3W had a Dave Gale chassis under it with both front and rear 1/4 elliptics with the spring connected to a "tube axle via shackles and a top 1" bar that ran from the top of the axle to the from just in front of the fire wall. Same basic setup in the rear except the the banjo housing instead of the tube axle. One of the best straight axle riding hot rods I have had. And if you know me you know I have had a bunch. Also, to muddy up the water a bit more, it had an early Honda manual rack unit for steering as well. I put a ton of miles on it and never had a failure of issue.

 

looks cool nice work!

 

Jason Grimes did a good article about this exact setup in Street Rodder a while back....

http://www.streetrodderweb.com/tech/0909sr_1934_plymouth_coupe/index.html

Do it over, ditch the hairpins.



Rich

 

Hmmmm... Interesting arrangement. I saw a picture on your other thread before you put the hairpins on.

http://www.jalopyjournal.com/forum/attachment.php?attachmentid=911362&d=1267302127

You show no shackles, so this definitely uses the spring as a dynamic and load adjusting lower link and the upper as a solid stationary link. I'm a little confused by the arrangement. Without seeing how you've mounted the back of the hairpins, my first instinct is that you will have binding with this suspension geometry.

EDIT: The rodster beat me to it. Certainly not the best way maintain control caster angle, so wouldn't be my choice of front suspension, but no reason why it shouldn't ride pretty decent with the triangulated upper arms.

These two pictures are key...

 

Nice job and the way YOU want it which is fine. As a note. There is no sidesway in 1/4 eliphtics. Two top bars two bottom springs only works fine. Have now done it three times on three different cars. .

 

I dont know much, but I see no need for those hairpins. I dont see them doing anything for side to side sway either. You said it yourself, the springs and top bars create a 4-link, and by the looks of the top bar angle, it is triangulated on top. That will stop any side sway better than those hairpins anyway. It looks really busy, when it should be simple. Your headlight mounts look out of place too. Hard to say without seeing a shot of the whole car, but it might look better with some bent F-1 mounts with the headlights attaching to those. Just another losers opinion. Id like to see a shot of the whole car.
Rob

 

I always found the quarter elliptical set up interesting.That link is great. I have a number of bars from a old 4 link kit that can be used.Going to have to keep this idea in mind.

 

I thank the American Counsel of Armchair engineers that have crunched the numbers and my front end. How much do I owe?? LOL....Just kidding.... : )

 

You're right,I would go ahead and add a set of wishbones and a four-bar while you're at it.

Rich

 

Well that's a great attitude when discussion occurs about your car with people who just might know more than you do.

 

other than that, those headlights are going to be wiggling severely, at least until that curved tube breaks from all the shock action. back to the drawing board.

 

You're new, so you probably don't know, do yourself a favor and check out some of the stuff these guys have done. You just might be surprised a bit. They aren't really armchair engineers.

 

i have done this set-up already and about to do it to a another pair of springs and a pair of bars worked great the one had a big block in it no sway or shake handled well also.

 

I plan on using 1/4 ellipical set up on my next ride. I will be triangulating the top bar with the spring as bottom bar. I'm I right in thinking both should be parallel and be the same length, but does it matter if they are level or go up hill in the rear. I am using a 37 Plymouth axle so I have to make a swivel mount for the spring.

 

Quarter elliptical springs don't allow any appreciable lateral movement, do they?
In which case, a single bar per side would suffice...with no triangulation needed. And as mentioned, the two different length bars...the upper bars and the hairpins...will definitely tend to bind due to unmatched arcs. True, hairpins have some give...they twist as one side of the axle moves higher than the other. But they're not meant to be flexed linearly. Granted, with limited suspension travel, the bind may not be immediately evident...but it's there. I'd think that hairpins or wishbones and the springs with shackles at the axle end would be a more reasonable setup.

 

JMO it looks like shit.

 

I think the "normal" way of combining quarter-elliptic springs with wishbones would be to use shackles on the springs, and let the wishbones handle the axle positioning.

The additional top "4-link" bar is redundant.

Use a Panhard bar to control axle movement side-to-side.

FWIW.

 

Why not use two springs per side like Harry Miller did on his INDY cars?

 

Just exactly what I'm doing on my lakes modified, front and rear. If it worked for Harry Miller, it should work for me.

 

I hope there are more photos and comments. I've been researching this for a while to use on a project I want to do.
How does this setup handle in the corners?