[This message has been edited by ITALGT (edited 02-09-2013).]

Thanks Joe... (at least I think it was a compliment)

I've finally completed the schematics of what I plan to build for the rear suspension, well, at least as far as I'm going to develop them in electronic format. They aren't 100% complete because I've reached a point of diminishing returns (and I'm starting to get cabin fever). Before I describe the important aspects of the design, I want to mention that I've strayed from my original goal of making this an easily retrofittable modification. I apologize to anyone who might have been hoping to duplicate my design, but I ultimately had to choose between either a relatively simple modification that would not work very well, or a more involved project that would give good performance. Since I am primarily building this for myself and had no plans to market any kits, I chose the latter. Now, onto the final configuration...

As I mentioned in one of my previous posts, I had a breakthrough in the design process when I finally ditched the idea of keeping the extended Held/HT Motorsports lateral links I had bought earlier. Their length meant that any new upper link mounts would have needed to protrude into the engine bay if I wanted decent suspension performance. With that constraint removed, I shortened the lower lateral links considerably in my drawings until the inboards mounts cleared the overhanging F40 transmission on the LH side. That then allowed me to raise their mounting points as well. The rest of the geometry was a piece of cake from that point. With the geometry set in stone the first thing I needed to do was design a new cradle to tie the new lower link mounts to a framework that included the front and rear cradle mounts:

THE CRADLE

Since my OEM cradle was rusted out anyways, I started a clean sheet design by placing everything I had (engine, transmission, raised cradle mounting points, and new lower lateral link locations) on a 3-view drawing, then drew a set of four 2" X 3" X 1/8" beams to attach all the known points together. I chose this size tubing to maintain a cross sectional area that was at least as large as the OEM for greater strength. While the design of the cradle side rails is basically complete, the shapes and locations of the cradle cross members aren't. They're just "fill-ins" until I have the time to design mounts for the Northstar, the F40, and the exhaust layout. Here is the top view with the new cradle in blue compared to the OEM cradle outlined in red:



From this view you can see that I moved the forward lower lateral link mounts outboard by 96 mm and the aft link mounts 123 mm further outboard, per side, than stock. Two neat things followed: the first was that both link mounts now lined up perfectly with the front cradle mounting point, eliminating any need to joggle the cradle side rails inward like the OEM cradle (I believe this will make the cradle stiffer); the second was that it added some wiggle room at either end of the engine/transmission. One side effect however was that with the new side rails being further apart, the rear cradle mounts would have to be offset inwards to meet up with the lower frame rail of the car. At first this concerned me knowing that I would have to create offset rear cradle mounts until I realized that the OEM mounts are offset by an equal amount outwards. That meant they could be swapped sides and all would be well again. I also shortened them to raise the cradle 25 mm. Here's the rear view showing what I mean... again, the blue is new, red is OEM:



I'll evaluate the need for gusseting the rear mounts better once I get into the actual fabrication of the cradle.

Finally, here's the RH side view showing the profile of the cradle side rails.



The important features to note are that:

1. the cradle mounting points have been lowered 25 mm from stock, which will result in the cradle being raised up into the chassis;

2. the lower lateral link mounts have been raised an additional 70 mm from the stock location as well as having been moved outboard;

3. the cradle bottom extends 10 mm below the oil pan allowing a skid plate or other oil pan protection to be installed; and

4. the rear cradle kicks up at the rear allowing for such features as exhaust system clearances, a marginally better ramp angle, and/or the installation of towing hooks.

Up next, the whole schemozzle installed in the chassis along with the new upper links.

(edited to update drawings to "as built" configuration)

[This message has been edited by Bloozberry (edited 07-26-2013).]