SpeedTalk Store - Opinion Columns

Quarter-elliptic rear leaf springs.

Shocks, Springs, Brakes, Frame, Body Work, etc

Moderator: Team

Quarter-elliptic rear leaf springs.

Postby pdq67 » Mon Nov 28, 2016 11:02 am

What are everybody's thought's on installing, "quarter-elliptic", springs on my 1st Gen. Camaro by making my sub-frame connectors strong enough to mount them solid up front.

Then attach them to my rear end so that they pivot and that's it. By probably use something like, "Johnny-Joints"... No shackles is all.

I would probably need a watts or a panhard bar to hold side to side sway tight.

Just trying to think outside the loop.

Might be able to use a stiff F/G mono leaf spring to save a lot of weight, imho??

Heck, I might take two Astro Van F/G springs and cut them in half and stack them to try this on the CHEAP?

pdq67

PS., I know now that I am retired, I have way too much spare time on my hands!!
pdq67
Guru
Guru
 
Posts: 6022
Joined: Thu Mar 04, 2010 8:05 pm

Re: Quarter-elliptic rear leaf springs.

Postby Brian P » Mon Nov 28, 2016 12:29 pm

Quarter-elliptic springs have been used in the past. A google photo search for "quarter elliptical suspension" returns quite a number of examples.

The connection at the fixed end of the springs needs to be a very strong moment connection (it has to resist twisting). A rigid end mount will also make the spring resist side-to-side motion (cornering forces). If you use it in conjunction with a panhard rod, the geometry will have to be carefully chosen to avoid binding. Probably the axle (pivot) end of the spring would need to allow side-to-side "give".

I'm not sure how this would be "better" than a traditional Hotchkiss layout given that you already have the space to use full-length leaf springs. The photos that I see on Google appear to be for suspension designs where the axle is very close to the end of the vehicle, or even beyond the end of the frame of the vehicle in the case of solid-axle front suspensions. In those situations there is nowhere to put the other end of the spring, so there is a legitimate excuse for using this design.

I know the Cord automobile of the 1930s used upper and lower quarter-elliptic springs to locate its rigid front axle.

If the intent is to control axle wrap-up, I think one of the proven solutions, e.g. a supplementary upper locating link, will work better.
Brian P
Guru
Guru
 
Posts: 1057
Joined: Wed Jan 02, 2008 7:35 pm
Location: Toronto, Ontario, Canada

Re: Quarter-elliptic rear leaf springs.

Postby pdq67 » Tue Nov 29, 2016 6:42 pm

Brian,

I very much thank you for posting back on this.

I post stuff and usually don't get squat back for helpful info.

I only brought this up because of the possibility of saving a bunch of rear end weight is all if I used junkyard Astro Van F/G rear leaf springs cut in two and stacked.

I would probably use a rear, "track locator", bar, that would be located at the bottom of my rear end, "pumpkin", if you will, so that my rear end roll center would be as low as I can make it.

Add this to my now front end roll center that is about 2.5" above ground and I should HOPEFULLY corner like a, SK-8 Board!!

pdq67
pdq67
Guru
Guru
 
Posts: 6022
Joined: Thu Mar 04, 2010 8:05 pm

Re: Quarter-elliptic rear leaf springs.

Postby Brian P » Tue Nov 29, 2016 8:15 pm

I doubt if it would end up lighter than a normal Hotchkiss leaf spring arrangement by the time all is said and done - including whatever you have to do at the fixed end of the springs to absorb that moment load. If you are stuck with a live rear axle it's hard to get lighter than Hotchkiss leaf springs because the same elements do the springing and the axle-locating, and they do a decent job of spreading applied loads out around the chassis instead of applying them in concentrated locations that then have to be beefed up. Of course, there are side effects, e.g. axle wrap-up, and imprecise side-to-side location.

Among the production live-rear-axle setups that I know of, the one that has the best geometry is that used in the S197 Mustang - 3-link with panhard rod, coil springs. The roll center is not too high, they can have decent anti-squat, bump-steer and roll-steer behaviour is not bad, axle wrap is well controlled, there's no binding within reason.
Brian P
Guru
Guru
 
Posts: 1057
Joined: Wed Jan 02, 2008 7:35 pm
Location: Toronto, Ontario, Canada


Return to Chassis / Suspension / Body

Who is online

Users browsing this forum: No registered users and 4 guests