You are thinking that as the tire rotates clockwise the housing is rotating counterclockwise and causing springwrap. And that shortens the wheelbase, if you have open drive then just one side will wrap and that'll cause rear-steer? Is that what i see in your drawing, the 'caster' change?
Dont the upper bars prevent the rear end from doing this? They would maintain the length from side to side because they are a fixed length, so only the entire wheelbase would change when spring wrap occured right? The wheelbase would be the same both sides. I am not nearly as versed on this as the rest of you just trying to learn here.
OJ, there is no caster to change, because the spring deflects it changes length, its a distance measurement. The drawing exaggerates the the concept to show what is happening to the axle center as the spring flexes.
If one wheel is dropping down while the other side is going up the springs are pushing the rearend in opposite directions front to back at the same time as they flex.
Imben, you are thinking only in one place in time, if the rear axle tires encountered the same bump or drop at the same time they would be constant but if one side hits bump or drop then the scenario changes.
I see, as the axle travels on its arc the length changes because the spring flexes on a regular four link but does it work the same when the upper bars are triangulated?
Just a reminder, the OP stated that the springs are NOT locating the axle... He is using a 4 bar and the springs have shackles on them.
Without those promised pictures all we can do is guess, and maybe even after seeing them there still might not be a clear answer. It could be that they are suspecting the spring setup and it could be something else, like steering design, or the squareness of the chassis. When my Son did the quarter eliptic setup on the back of his rpu he decided to not use just the spring as the bottom locator, even though Posies said it would be ok. So he installed a four bar setup and then used the springs just as springs only. He did install a shackle on each spring so that it could move freely without binding against the rear end housing as it goes up and down. The ride is really good. I have been following him and when he goes over pavement repairs and other rough surfaces the car stays straight. He has also driven the car very hard and under acceleration or braking it stays straight there also. I realize the OP has this type of setup front and back, so maybe that is contributing, it just adds one more thing into the mix. It will be helpful to see the pictures if and when the OP posts them. Here are some early construction photos of how Dan built his. Don
I suspect this will be a bump-steer issue. Also, I don't recall the mention of any shocks being used. Might just be an oversight, but no shocks can make for some funky handling.
The Panhard does nothing. I dont know why that is such a problem for people to see. If you need a panhard then something isnt strong enuf like your Spring or spring mounts. We are unable to produce any lateral (side movement in our set ups. With the hemi Jeep we tried everything to get some deflection because someone from the Isles insited it was necessary and so we showed him. Nothing. We were actually able to produce much more lateral movement in a normal leaf spring rear suspension than in the 1/4 eliphtic suspension. if you use 1/4 eliphtic and a four bar on shackles that is a whole different deal. The whole point of a 1/4 eliphtic set up is the 1/4 spring locates AND springs the car otherwise I fail to see what the point of using it is. If you are going 4 bar you might as well just pop in a coil spring shock assembly and a Panhard, or watts linkage or triangulation accross the lower bars. Will the Panhard hurt the 1/4 eliphtic set up? Probably not. No more than 2 pulleys and a chain hurts a WC but it is totally redundant. Don
Hey Hemigurl: Are you going to post pics ? Or reply to people's questions ? Because right now, it might as well say this: "My car doesn't handle right. Please speculate what is wrong with it, while I ignore your requests for pics and technical details."
Am I glad you posted this with pics. It gives me a clear direction on the rear of a build Im doing. Do you have pics of the front? I'm assuming it is Q.E. also.
My take...after building several quarter elliptic setups in light cars, I've always used a four bar for locators. The spring grows as it flexes, it lengthens, changing caster if solidly mounted to either front or rear axle, giving the car some weird control issues. Using a four bar and quarter elliptics require a shackle, as the four bar is rigid and does not grow in length during its travel. I build my own springs, its a fairly simple job, a well built quarter elliptic setup will give a light car amazing handling qualities, my T bucket on a windy hiway was a posche killer, 1900 pounds of pure fun, panhard bars are not necessary, you'll have a car that is rock stable, put the right shock in it and enjoy. What I read here seems to be a bump steer problem, poorly set up chassis will flex enough to cause the car to have a mind of its own, could it be frame flex issue?
No, the front is a traverse spring, but done suicide style. That is why I felt maybe the OP's handling issues were coming from the front, it just seemed to me that the front would have more tendency to cause steering issues than the back. But without those pictures.......................... Don
This is what happens so often, a guy comes on and has some engine problem or other problem and everyone jumps in with suggestions to help. Then we never hear back as to what he found . I think it helps everyone if the person lets us know what the outcome was and if any of our suggestions were right. Don
Well, even if the OP don't get the benefit this thread has gotten me to re-engineer my rear suspension. I have my quarter-ellips direct to the rear housing to act as both lower control arm and spring. i don't know how i will find space enough to add shackles and lower control arm but that is what i had better do. The shackle is the hard part, i'll need and 1" or so.
Absolutely right. People go to the trouble of asking for more information, so they can make an intelligent suggestion, or share their experiences with similar cars, and it's like they are talking to a wall. No reply, no feedback, no nothing. WTF ???
Ive been checking this all day as if i could help i would.There are are alot of good people on here with so much to give and as has already been said this happens so often !! IM done. JW
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