Boxing in LCAs
What the plates do is resist deflection by adding shear strength. Looking at it like I do from a construction background, a wall frame is stiffened tremendously when it has plywood sheathing nailed to it. The plywood adds a huge amount of torsional resistance.
Here is a simpler way of looking at it all: The chassis and frame all have some degree of flex that occurs under stress. The less flex, the better the car will handle. These were designed around 6 inch wide bias ply tires so back then, the chassis probably never saw as much force put into it as we are able to deliver with todays tires.
Some upgrades like this are cheap and easy to do and lay the foundation for upgrades in the future.
Backing up a bit....
A solid platform is a great way to ensure that everything bolted to it works to its potential. What I mean is, if you put in bigger torsion bars, sway bars, better shocks and wide-sticky tires, they will not work their best if the chassis is still stock as built when new. The chassis/frame acts as another "spring" in the system, as the suspension goes up and down the frame is moving too. Subframe connectors, torque boxes, Monte Carlo braces, radiator yoke supports, a welded K member...All of these things work together so that the suspension is connected to a solid foundation.
With my 70 Charger, I took a stock K member and welded all the seams fully. The steering box mounts on all of our cars had open voids that allow the steering box to flex and move around. This only gets worse with wider tires and hard use. I made metal pieces to fill in the voids so that the steering box stays in place. I made my own frame connectors and torque boxes and welded them in. It was a pretty cheap upgrade that really gave the car a solid feel.
What the plates do is resist deflection by adding shear strength. Looking at it like I do from a construction background, a wall frame is stiffened tremendously when it has plywood sheathing nailed to it. The plywood adds a huge amount of torsional resistance.
Here is a simpler way of looking at it all: The chassis and frame all have some degree of flex that occurs under stress. The less flex, the better the car will handle. These were designed around 6 inch wide bias ply tires so back then, the chassis probably never saw as much force put into it as we are able to deliver with todays tires.
Some upgrades like this are cheap and easy to do and lay the foundation for upgrades in the future.
Backing up a bit....
A solid platform is a great way to ensure that everything bolted to it works to its potential. What I mean is, if you put in bigger torsion bars, sway bars, better shocks and wide-sticky tires, they will not work their best if the chassis is still stock as built when new. The chassis/frame acts as another "spring" in the system, as the suspension goes up and down the frame is moving too. Subframe connectors, torque boxes, Monte Carlo braces, radiator yoke supports, a welded K member...All of these things work together so that the suspension is connected to a solid foundation.
With my 70 Charger, I took a stock K member and welded all the seams fully. The steering box mounts on all of our cars had open voids that allow the steering box to flex and move around. This only gets worse with wider tires and hard use. I made metal pieces to fill in the voids so that the steering box stays in place. I made my own frame connectors and torque boxes and welded them in. It was a pretty cheap upgrade that really gave the car a solid feel.