I ran across a few pictures of lil johns modified rear suspension. can anyone explain this setup. What a talented guy!
I think that cross-car torsion bar at the front of the lower bars is an adaptation (to a completely different springing system) of the bar connecting the leaf springs on one of the "Old Yellers"! If I'm right, it transfers reaction on one side of the car directly to the other...ultimately it is a sort of anti-roll bar! I think Buttera was likely guided by the son of the alien who worked with Balchowsky...
I don't believe that you actually can. Otherwise you would do so and also post your explanation here.
Ok, so after looking at this for for a bit, here's what I've come up with. The lower radius arms from the axle to the frame are tied together by that torsion bar and likely ride in some sort of bearing or bushing in the frame, this allows the system to work without binding going over bumps, meaning it allows the coil overs to work each side of the rear end without affecting the opposite side. Why that is needed, it's likely for anti sway as mentioned, since as the body rolls the coil overs would be forced to work against each other and the torsion bar would prevent component breakage. Next, the splines in the torsion bar obviously go out to the radius rod and pass thorough what I at first thought was a bell crank, but in actuality is just a lever with the "upper" part of the coil over mounted slightly off center. As the suspension compresses, that lever will roll forward and start to compress the coil over spring. At the same time this lever moves, it causes the small link up top to transfer force to the bell crank which pushes in the "lower" part of the coil over, increasing spring rate as the bell crank lever system operates. If I'm not mistaken this allows for a shit ton of up/down wheel movement out very little compression/expansion of the coil over, and the bell crank pivot carries all the weight of the rear of the car.
Here's what it looks like to me and I may be completely full of shit.... it's happened before. I think Bruce and Pocket Nick are pretty close, but it looks like Nick has the end result just backwards. A little movement of the axle at the end of it's compression travel makes a huge movement of the coil over shock. Modern dirt bikes, snowmobiles and probably racing 4 wheelers all have what is called rising rate suspension. They use different methods of achieving the results, but most have an arm and some linkage, some have 2 arms, all have linkage. What it does is offer a very soft spring rate at the first of the travel and it gets progressively stiffer as it is compressed. Snowmobile suspensions are what I'm familiar with. Just as an example, the first 2 inches of snowmobile suspension travel might only compress the coil over 1 inch. At 5 through 6 inches of travel it may compress the coil over 2.5 inches and the last inch of suspension travel, say from 10 to 11 might be compressing the spring 5 inches. The farther the suspension travels toward it's limit, the more it compresses the coil over per inch of suspension travel. I hope I stated that in a way that can be understood. If it's not clear, just google "rising rate suspension" there should be a lot out there about it. In the case of Buttera's car, I'm guessing he wanted the outside to appear as clean as possible, no shocks, no springs, only the 2 lower radius rods showing. I'm pretty certain that the bar that passes under the frame has splines on the outside end too with a torsion arm like a sprint car would use that hooks to the axle and operates as a lower radius rod and a torsion bar arm. So, with this set up he gets several inches of suspension travel that he most likely will not be able to bottom out on the roughest pothole, a sway bar and a lot of guys looking at the outside of the car and scratching their heads wondering what the hell holds it up. At least, that's what I come up with. I think it's pretty damned slick too. I may use part of those ideas on the little modified roadster I'm gathering parts for.... if I ever get time to build it.
Was hoping that Blue's taunting would get P-Wood to "splain it". No better resource than from the mind of Pete.
Spring bone connected to the rocker bone Rocker bone connected to the frame bone Frame bone connected to the push bone Push bone connected to the cross bone Cross bone connected to the...
IMHSO most has been explained in bit to complicated way,,, I am not a builder but it seems simple system, but very pretty. The lower/outside bar moves up and down and is tied to a shaft that goes through the frame and is splined to the lower arm one. As the spline is moved, it bell cranks the arm directly across, which pivots the second arm, which now is controlled by the shock. And the shock is the 'spring'. Very clean, almost 'Rube Goldberg'. Now his Jag rears,,,,,,,,
A lot of INDY car thinking here. The story goes that Buttera wanted to go to INDY, but only could afford the "TUB" (Gurney Eagle) and figured he could make the rest of the parts himself. Ordered a CNC machining center figuring that he would make payments on it till the parts were finished and let them reposess it saving him about $70,000 on buying the parts, Made the parts but could not let the machine go back because it changed so much the way he did things by hand
I was trying out some of the other Larry's tactics. Seemed to work well for him A proper explanation of all this would be great. It's an impressive looking setup.
After playing around with it a little bit it. I think the purpose is it allowed him to use long arm and still maintain the same spring rate. Sent from my LGMS550 using The H.A.M.B. mobile app
it's an interesting layout that keeps your unsprung weight low, your mass centered in the car and your spring rates adjustable buy simply changing out the arm. if it was a real racing setup all those arms would have multiple holes to make easy adjustments. in reality I'm not a fan of the execution. having so many suspension points in single sheer like that makes me nervous. I would also like some more detail of the lower arm mounting points to the torsion bar and axle. locking all those points together with no flex would be detrimental.
Because of the length of the lower trailing arm the amount of rotation at the rear rocker arm is limited and the shock/spring would not stroke enough to be effective. The ratio of the forward rocker arm fixes that problem while keeping the whole package below the floor. The lateral splined bar is simply an anti roll bar. Here is my solution to the same sort of problem on a street driven dragster that I built a few years back. The ratio of the linkage allows full travel of the coil over and the geometry makes it a rising rate deal--initially soft damping/spring rate gets higher the further that the axle travels. Roo
Kind of like door handles. Lots of trouble to hide the working parts. First you have to move the parts that do the work then you need to transfer the energy/motion to the new location of the working parts. Everything should be as simple as possible, but no simpler, right? So by simplifying the look of rear suspension the operative term of "everything" was ignored and the natural consequence is that rest or everything got more complicated.
Its funny, when I read this, I realized I didn't know what the rear suspension under any of the Old Yeller's looked like, so I went on the hunt for photos. I started with a Google search, figuring how hard can it be to find rear suspension photos of a car this famous? Came up empty. Now I am going through my own stuff, still not finding anything. Is this some closely guarded secret? Anybody have any pics?
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