A post over on that other forum has sent me down the rabbit hole today.
Using coil springs in the rear of an MGB is something I have pondered over the years. I vaguely recall the MGB designers tried coil springs, but they did not like the handling. What did they use to retain the rearend laterally? Maybe that was the reason.
Anyway, I believe it to be do-able.
MGBBodyShellBottonRear.jpg
CoilSpringLocation2.jpg
CoilSpringTrailingArmPanhardRod.jpeg
CoilSpringRearSuspension.jpg
Fox Mustang is similar but 2 upper links for triangulated 4 bar. A lot of Cobra kit cars use it. some have done away with the coil springs and went with coilovers where the shocks are. Only with stronger mounts. Probably for the cool look.
The rate of the springs will need to be calculated based on the position on the LCA. MGB front springs are rated for about 200% of the corner load due to the 50% lever arm reduction. So travel is also about 50% of spindle travel. Exact numbers would require exact measurements.
So, there is no reason why you couldn't use full size coil over springs. I think it might be better than using the 2" ones we've been seeing and there should be plenty of room for them.
Ideally the spring seat would be in line with the two pivots, at the body and at the axle for even loading. That would determine the top spring seat location. I think that puts it in line with the frame rail though and I'm not sure there is enough vertical space there. The spring could also be angled forwards but that raises the spring rate.
Jim
In the past, I have read about the Mustang triangulated uppers causing bind. May not be an issue when not very much travel.
Yeah, no room for the spring on top of the axle. Plenty for full size coil spring forward of it. I have seen that on production cars and NASCAR.
TrailingArms.jpg
Might use a lower link similar to some of the traction links being used, if needed a drop section for the spring seat, then either triangulated upper links like in the CCE 4 link kit or a single top link and a whatchacallit for sideways. Shock might have to be behind the axle.
Jim
Track bars are not ideal for an MGB, but offset coil springs (adjustable, even) in conjunction with a 3-link & panhard rod, just may be.
AdjustableCoilSpring.jpg
I really like the adjuster idea. Looking forward to seeing someone take off and run with the concept. It's too good not to get done.
Jim
Coil-overs, proportunately are pretty high. Personally, I don't like the lateral arch of a panhard bar, especially with tight tire clearance.. A watts link has better properties but is more complicated. "What if", the outer ends drove a torsion bar ? No coils needed. Might fit better in tight constraints.
Art.
Wait ! What if torsion bard was splined or hex, you could tune the springrate.
Mmm, doesn't the bar itself define the rate, the hex just raises or lowers the susp?
Yes.
Carl
"MG was aware of the ride issue long before the first MGB was even built. According to an interview of MGB designer Don Hayter (which I found in Ken Smith's excellent little book "Aspects of Abingdon" as published by MG World, copyright 2006), the very first MGB prototype was fitted with a trailing arm and coil spring rear suspension that included a Panhard rod for side-to-side axle location. A similar suspension had been installed on MGA developmental vehicles. The factory engineers preferred coil spring suspension over leaf springs to achieve a smoother ride. Ultimately though, MG engineers were unable to overcome a slight steering effect caused by fitting a too-short Panhard rod".
This is copied from http://www.britishv8.org/Articles/MGB-4-Link-Rear-Suspension.htm
Seems they could have used a Watts linkage...
Jim
I read an article about that long ago, Philip. That is a good part of what had me pondering this approach. It is also why my panhard rod is 35 inches long. :)
The Watts was part of the plan, Jim. They went with the cheaper panhard rod that doomed the 4 link.
"Enever and chassis engineer Terry Mitchell explored a variety of alternative suspension layouts in hopes of smoothing out the ADO23's ride without sacrificing handling. The ideal solution would have been to reduce the rear unsprung weight with either independent rear suspension or a De Dion axle like that of the EX181, but cost considerations precluded either. As a compromise, Roy Brocklehurst, who had designed the original MGA chassis, came up with a four-link design that traded semi-elliptical leaf springs for coils, locating the axle with four trailing arms and a Watt's linkage, later exchanged for a cheaper Panhard rod. The new suspension provided a much better ride, but the Panhard rod mounting caused structural problems and erratic handling.
Given time, those problems could undoubtedly have been resolved, but with the project already running well behind schedule, Brocklehurst and Mitchell decided to retain Hotchkiss drive. The production car's sole concessions to improved ride quality were redesigned spring shackles and longer (and thus softer) leaf springs, the addition of which required the tail to be stretched about an inch (25 mm)."
https://ateupwithmotor.com/model-histories/mgb-and-gt-history-part-1/2/
Presumably the handling issue could have been resolved with a triangulated 4 link, but I'm not sure how common those were in 1960-61, I expect somebody was using them but I have yet to find out who. Oldsmobile was using coil springs in the rear in 1940 so it doesn't stretch the imagination too far to think the triangulated design was widely known by 1960.
Jim
May not be the first, but check out a '58 Chevy.
Was that the intro of GM X-frame??
Looks like the X-frame was first introduced by GM in 1957. It was used on the Cadillac starting that year. Chevrolet & Pontiac adopted it in 1958.
https://www.curbsideclassic.com/automotive-histories/automotive-history-an-x-ray-look-at-gms-x-frame-1957-1970/
Not really a triangulated 4 link, more a triangulated 3 link.
The X Frame only lasted till 1964 and GM went back to ladder type for more rigidity. The GTO 442 Skylark Malibu
began in 1964. Photo of Dyno Don 's 1963 drag car show the failures of the X. His left front wheel was up to 2-3' . Drag racer fixed this flaw by welding support beam to frame to from a ladder type frame. Those old motor made torque and got traction. also.
I think the real advancement in frame torsional stiffness came with the introduction of the tubular cross member sometime in the 60's. By the mid 70's it had become reasonably common and was a noted feature of the '75 I-H Travelall which needed all the torsional stiffness it could get. But at that time I think auto makers were having a real problem deciding if leafs or coils were better.
Jim
I have a very negative opinion regarding the X frame cars sine I spent so many hours under my Impala SS, 327 300HP, 4 speed due to busted spider gears in dif. Threading the 2 pcs. shaft thru the x portion and looking up convinced me that just no reasonable way it was superior to std. ladder frame design. Worked under many others and since our service station had a garage got to go under many different makes. All that work just sticks in my memory what is left of it.
1964 was the end for most GM cars. The article states that the Buick Riviera retain the X frame through 1970.
Seemed like Triumph and Spitfire used a sort of modified X frame, kinda similar to the Olds with the perimeter rails. By the end of the 60s the frames on American cars were getting pretty good.
Jim