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Old 03-24-2007, 10:23 AM
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Staggered 4-bar okay?

I know this has been answered/discussed somewhere in a prior thread (or threads) but I couldn't seem to narrow down my search words enough to find it.

Can I stagger the top/bottom 4 bar location on the rear of my chassis as shown in this pic. Assume that that bar lengths are equal top and bottom and that the the bars are parallel to each other and horizontal to the ground.

I'm not sure it matters for this question, but these bars have to be very short...only about 14" center to center.

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Old 03-24-2007, 10:36 AM
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Sure

Sure you Can.
you can even make the top bar shorter if you want and it won't have much effect depending on how far your suspension will travel.
The key is to make the lower arm parallel to ground at ride hight.

Hope that helps,
Mike
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Old 03-24-2007, 11:06 AM
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Realize that this arrangement will give you extreme squat on launch. You can eliminate the squat if you keep the bars parallel to each other (to eliminate binding during cornering), but tilted upward, from the rear, with a tangent equal to the CG height divided by the wheelbase. Yes, this will give you some roll steer effect (which is why it's often recommended that the lower bar be horizontal), but it's nothing to worry about. You'll need less steering wheel angle for a given turn, but, since wheel loads are unaffected, there are no inherent stability problems.
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Old 03-24-2007, 12:10 PM
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Thanks Mike and BillyShope. This car isn't going to get "launched" a whole lot but it's very good to know that if anything, I should error on the side of having the bars angled UP from the rear end rather than down (which I assume would make the squat problem even worse. If I can get the bracketing to fit right, I'll try to get the recommended angle on the bars.
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Old 03-25-2007, 12:32 AM
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Have you seen the quarter elliptical rear setup on the Loaded 29 pu? They use the springs as two of the four links.

http://www.rodandcustommagazine.com/...adster_pickup/
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Old 03-25-2007, 05:30 AM
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Quote:
Originally Posted by home brew
Have you seen the quarter elliptical rear setup on the Loaded 29 pu? They use the springs as two of the four links.
VERY pretty!! And, that makes a very "neat" suspension for a show car. For a street car to be built within a reasonable budget, however, adjustable coilovers make a lot more sense. Not putting you down, home brew; I'm just concerned that someone is going to see something from a show car and try it on his first project car.
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Old 03-25-2007, 03:13 PM
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Quote:
Originally Posted by BillyShope
VERY pretty!! And, that makes a very "neat" suspension for a show car. For a street car to be built within a reasonable budget, however, adjustable coilovers make a lot more sense. Not putting you down, home brew; I'm just concerned that someone is going to see something from a show car and try it on his first project car.
I agree. Cboy has been trying to work outside the box and use as much of his donor truck as possible and I have been trying to feed him ideas. I have seen several quarter elliptical rear suspensions built in this area. Of course they have not used the rear springs as part of a four bar but a panhard bar and triangulated radius rods.

Do you see a reason that using this idea with half of a "four bar" setup for the top bars and a panhard bar and shocks mounted to a separate cross member would not work? How would this setup ride and would the rear suspension work correctly in a fenderless T or A type bodied hot rod built for the street.
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Old 03-25-2007, 04:22 PM
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Once you have the right rate for the quarter elliptics, there's no reason why it shouldn't work. Probably wouldn't need the Panhard. But, it's that finding "the right rate" which makes the design something which should probably not be attempted for a street car. And, the "fuzziness" concerning the locations of the "pivot points" where the springs attach to the housing makes it difficult to accurately predict the performance. With adjustable coilovers, these problems are eliminated and you have the time and money to conquer the other problems which are bound to occur.
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Old 03-25-2007, 10:30 PM
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Thanks for the reply. I had never considered using a rear quarter elliptical suspension but I may go with a Posies front spring set up. I like the ride height adjust-ability and the new swivel shackles which are said to eliminate binding.
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