Chapter 6 - Engineers at Play
After all of the chatter today about driveshaft angle and interference, I figured that I should take this as a sign to enter my next chapter. As some of you noticed in the last photo of Chapter 5, the chassis of the Spence car has changed a little bit. Before I spill all of our secrets, let me provide a bit of background.
Unique 9122 was initially sold to our friend Spence back in December of 1991. Since that time several updates to the design have been made by the Weavers, including relocation of the rear trailing arms, elimination of the MG front suspension, brake upgrades, and other improvements. In addition to faithfully reproducing a Carroll Shelby race car, my Dad and I had decided that we wanted to update the car to current technology wherever prudent. A quick phone call to Maurice Weaver both loaded up my credit card and resulted in a big box on the front doorstep just after Christmas.
The rear suspension pivot brace and relocated trailing arms were the first modifications to be made on the 12 year old frame.
http://www.uniquecobra.com/uploaded/...rear parts.jpg
Before the Jag rear suspension was dropped out, we located and installed the rear pivot arm support. With a simple cut and a shower of sparks, the car felt a little bit more like ours. The feeling of mounting new parts was also a thrill as we recognized that the process of building had actually commenced. A few minutes with the angle grinder yielded a cleaned up and neatly radiused bracket. With this in place we turned our attention to something a little more exciting.
As mentioned in Chapter 5, we knew that a drive shaft interference problem existed on our car. The reason for this was a combination of the frame not having a relief cut like the current version and the transmission was sitting little low. All of this was easy to see from our vantage point, however, the original builder never had the body off the frame.
With our measurements double-checked twice, we broke out the Sawzall and angle grinder and let 'em rip. A mere 30 minutes later our fillet was clamped in place and is ready for welding. We allowed 2" of clearance from the bottom of the bolt circle and matched the radius of the pinion input.
http://www.uniquecobra.com/uploaded/...t sway bar.jpg
Just below the drive shaft relief are the four bosses that we located for the rear sway bar, another update that showed up in the belated Christmas present that came from the Weavers.
As much fun as these changes were to make, the "piece de resistance" of our updates clearly shows the "engineers gone overboard" that is present in both my father and I. Our first sit in the Rescue Cobra two months ago clearly illustrated that the fiberglass floors of the body could use some additional reinforcement from below. Again, this is something that the earlier cars did not have. Most sane builders would have cut and welded in a flat plate and called it good. However, prescribing to the "too much is never enough" theory, my dad chucked up the ball cutting tool in the mill and beveled the edges of our 1/4" thick 4130 chromoly seat support pans.
http://www.uniquecobra.com/uploaded/...e/ball cut.jpg
The result you see is an edge which perfectly matches the radius of the frame stock. Sitting in the opening with no other support than a perfectly engineered fit, the supports are also ready to be welded in place. Tomorrow at lunch the welding will be completed and the frame will be almost ready for powder coating.
http://www.uniquecobra.com/uploaded/...at support.jpg
Our seat supports were not the only custom fit metal work that will be part of the Cobra. As mentioned in an earlier chapter our rusty cowl brace was removed in order to clean up the corrosion that had accumulated over 12 years of sitting. After cutting the brace to get it free of the body, a stainless steel plug was machined to match the inside dimensions of the tube and is held in place with allen head bolts. Although the plug has been adequately sized so as to be stronger than the tube around it,
