This is a question about a rear suspension setup. On a single leaf in fron with dual shocks and radius rods would a person need to, or benefit from, running panhard and ladder bars? Or, would it be more effective if one were to split the rods (I like that look) and build a triangulated upper bar as below and run the spring behind with some dual shocks?? (without the pointy dracula styling. haha). I would think that a single triangulation would centre the rear end and keep it from needing a panhard bar, and with that setup maybe a torque/ladder bar wouldn't be necessary either?
I have a 31 with the rear suspension using the Model A spring, I installed a panhard bar because I could feel the rear getting a little itchy, loose when exiting a corner above 40 mph. With the panhard bar installed, the rear tightened up and handles great. My 37 truck that is being built now, I am using a 4 link and a low and long panhard bar with bags and shocks. The model a srung rear is a harsher ride.
Ok, not a suspension guru, but I'll give it a shot. The first pic shows a torque tube traditional style rear suspension. This type of suspension uses the leaf spring/shackles as a lateral locator for the axle and the torque tube as a longitudinal locator. The radius rods help support the torque tube from being twisted in the plan view (top view) and stressing the connection at the torque tube to axle. The torque tube takes both the braking and forward engine torque loads, and does not require an upper suspension member (upper trailing arms, etc.). You will get some sideways motion out of this type of suspension as the shackles do have some movement as the spring is the only thing truly holding the suspesion in place laterally. Ford eventually went to a rear panhard bar (post war I believe?) to help eliminate this. The second picture you show is a good way to handle both torque and lateral loads with an open driveline type set up (no torque tube). Similar to conventional style solid axle setups, the upper arm(s) are necessary for this. If you don't put the upper arms on some kind of aggressive angle (opposing each other)they will not take lateral load, and you will need a panhard bar. You hear of cars with a four link rear suspension - this can be two lower links, and two upper links (on an angle opposing each other), or two lower links and one upper link (to take torque) and a panhard bar to take lateral loads. Or you can have a five link (two uppers, two lowers (all longitudinal) and the panhard bar (for lateral loads). The second pic is a good design. The only risk with this design is that the one attachment point at the top of the axle housing takes all the stress - both fore/aft (braking/engine torque) and lateral loads. This attachment needs to be built pretty beefy (and that picture appears to be pretty beefy) in order to not fail. My two cents.
Another two cents worth. I'll be using a very similar design (without the Dracula imagery) on my modified. It's a copy of what you'll find under a '58 Pontiac. I may add a light panhard bar to remove the lateral stress from that center connecting point.
I built a Monza drag car years ago and we used a 4 link suspension with coilovers............we used a triangulated brace similar similar to the second picture but with a tube at the apex of the V and a sliding link made from a heavy wall tube with a 3/4 heim screwed into it. really makes a nice unit as far as keeping the rear centered. Just remember to put a little bung in the outer tube for a grease fitting for a street setup.
MOTOR: Olds Golden Rocket with progressive kit... 312 hp (232 kW) @ 4600 rpm and 415 ft·lbf (562 N·m) @ 2800 rpm FRAME: 2x6 custom frame ETC: Whaddayaneedtaknow?
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