I know Charlie he has a nicely engineered chassis.What chassis to use?
When I first started thinking about building a Miura, I hadn’t seen any chassis used for home builds of the Miura except the Fiero. The Miura build using the Fiero required lengthening the wheelbase and ended up using very little of the Fiero in the end. No offense meant to those who’ve used a Fiero as the basis of their car projects but this felt like a very hacky way to go about building a Miura so I eliminated that chassis option right away.
The next alternative I looked at was to build it myself. Hey, I’ve designed and built a tube chassis for the C5 GTO and already have all the tools, including a chassis jig, needed to do it. Alternatively, I could build a chassis from sheet steel like they did at the Lamborghini factory if I got myself a power shear and a big box/pan brake. Hey, I’m always up for learning some new things.
Then I was poking around on the Mad Mechanics forum and came across a car called a Chupacabra. I’d never heard of that car before so I didn’t pay it any attention at first. Then I kept seeing mentions in the recent posts section and words like “aluminum” and “chassis” caught my eye. So being the curious person I am, I clicked into the thread which mostly announced new videos in a series of videos posted on YouTube. What the heck, I took a look at a video, then another, then another…
It turns out the Chupacabra is a car being produced by Charley Strickland of Strickland Racing in Fort Worth, TX. Charley has been building Countach and Diablo replicas for some time and decided to build a similar car but of his own design, the Chupacabra. What really caught my eye was the all aluminum monocoque chassis that he’d designed and was preparing to manufacture for this car. It’s largely made from ¼ inch 5052 aluminum sheet cut on a 3 axis CNC router with indexing tabs/slots then fitted and glued together on a chassis table. I was impressed by all the thought that had been put into the thousands of details that go into a chassis for a car of this complexity.
I reached out to Charley and filled him in on my Miura project. I then asked if his chassis could be made to work for a Miura. Charley was already very familiar with the Miura as he’d owned and driven one in his younger days. Both the Chupacabra and Miura are mid-engined but the key difference is longitudinal engine versus transverse.
Charley and I iterated through some bulkhead/firewall placement options based on rim/tire sizing, engine/transaxle mockup progress and finally settled on a chassis sized for a 105.5% Miura. The planned wheel base is 104 inches where the regular Miura is 98.5 inches. This should result in a Miura with comfortable legroom fit for me and the space to mount a Coyote V8 transverse. So the answer on what chassis will be used is that I am using a Strickland Racing chassis for the Miura project.
And yes, there was a road trip from California to Texas in order to pickup the chassis along with a bunch of other useful bits and pieces.
So plan in summary for the Miura project is:
- Plus sized Miura at 105.5% resulting in 104 inch wheel base
- All aluminum car; monocoque chassis, engine, transaxle, and body all done in aluminum
- Transverse mounted 5.0L Coyote DOHC 32 valve engine, 8 stack EFI, and 5 speed transaxle
Can you show what you used to curve the 1/2 tube to bend like that.Front clip fender liners
While I’m waiting on transmission shifter parts to arrive, it’s a good time to cover some metal shaping in the form of the front clip fender liners. I had completed the front clip framework structural part and it’s time to hang some sheet metal off it. I set out on this Miura project because I wanted to metal shape an auto body from scratch and well there’s just a lot of stuff that needs to be in place prior to shaping up the exterior bodywork. I’m not starting on the actual bodywork yet but making fender liners certainly involves a bunch of metal shaping.
The front fender liners on a Miura are an integral part of the front clip and get raised and lowered as part of the one piece front clip. So not only do they need to surround the wheels allowing for clearance as the wheels turn and go up and down but they also need to clear the chassis tub and frame members as the front clip is raised and lowered. I decided to build them “in place” so I could factor in the needed clearances each step of the way in constructing them.
I started by bending up a ½” square tube to the shape of the wheel opening. The station buck was used as a template in bending this tube into the complex shape for the wheel opening. This tube will be used both as a guide in shaping the fender liner parts but also as the support structure for the wheel opening in the final bodywork.
I decided to use AL 3003 .050 sheet for the fender liner. My first choice would have been .040 sheet but I didn’t have any .040 sheets in the garage and as this occurred in the middle of the COVID-19 shutdown, I decided to go with the sheet I did have. I decided to start from the top and work downward. . To start the metal shaping process, I bent the sheet into a short “U” shape over my leg and then used a TM Technologies style air power hammer to shrink the front and back edges downward.
The fender liner inside edge will be attached via a bracket to the front clip framework so that edge was positioned adjacent to it. Next I worked backward by cutting and shaping another piece. The shaping is predominately shrinking on the front and back edges. The metal shaping went well enough but I discovered my thin aluminum sheet “butt” welding skills are very rusty. I tacked up the pieces together with the TIG with the later tacks being much better than the first half dozen. I then broke out the O/A torch for the actual weld. Let’s just say that while the weld turned out fine, it was kind of lumpy and thus wasn’t picture worthy. It did clean up nice with some filing and planishing.
While this is fairly basic metal shaping, it’s still fun to form the flat sheet into a useful shape.
I’m starting to get the feel back for O/A torch welding but the welds are still not picture worthy. The metal finishing for it is getting easier as I am starting to be able to weld using less filler metal. Maybe the next weld joint will be picture worthy.
Yes, heat control is certainly a challenge when O/A welding on aluminum. The main way to overcome blow through holes is good eyewear so you can see the aluminum "ripple" as it becomes molten and practice, practice, practice...It’s been years (decades) since I tried welding aluminum with Oxy Acetylene... As I recall, the difference between hot-enough and HOLE was like 3 bloody degrees. I have fiddled with aluminum brazing and was pleasantly surprised...
Tip of the day: Rubber mallet and a flat surface is the best way I've found to re-flatten sheet after cutting it with aviation snips.Amazing stuff. The only metal shaping that I find myself doing is trying to make my aluminum sheet flat again after it gets a warp from cutting it! And that's hard enough!
David: turns out a bench vice (bolted to a very heavy workbench) with rubber jaw protectors is the tool I mostly used for those bends. A tube of this size bends fairly easy when strong armed. I also used a couple of large crescent/adjustable wrenches for fine tuning some of the bend areas and to add/remove twist in the tube as the bends changed direction. The trickiest part of these bends is that they're 3 dimensional which most tubing benders don't do well at. A good part of the bend time was spent clamping/unclamping the partially bent tube to the station buck to see which direction the tube needed to go for the next part of the bend. I also did small bend refinements with the crescent wrenches while the tube was clamped on station buck.Can you show what you used to curve the 1/2 tube to bend like that.