My 72 Europa SS

[Sofa King]

All of the mods that I did on the body, didn’t happen in a vacuum. The body and chassis had to be built simultaneously.  Rough measurements Of the body were taken and I had an extra engine that I used for mock-up purposes. I started with the mock-up engine on a storage stand and dropped the stock body over it to see how things looked. I shoved it forward until it touched the firewall and of course sat in the car and made engine noises!!

[Yellowbelly]

Know what you mean about the toothbrush. However once i built the trailer i then filled it with other stuff so still no room for a toothbrush.

[Sofa King]

Very nice! Is the Cobra boat still under construction? 😂

[Sofa King]

Once I finished making engine noises, I could determine how much room I needed for the engine and transaxle, and where the axles needed to be. That’s what determined that I needed to move the rear wheel wells 3” backwards now I had to build a frame to hold the engine and rear suspension. 
I have been playing with Miatas for over 15 years, so I stuck with what I know. The thing that makes Miatas useful for something like this is that the front subframe is held in with 8 bolts and the rear is held by 6. Disconnect the additional 8 bolts that hold the tops of the shocks and springs and the entire body comes off, leaving the roller skate, which includes the entire suspension, engine transmission and rear end. The trans is connected to the rear by a power plant frame, so in theory you can just reconnect the two subframes and you have a rolling chassis. I decided to use the front and rear subframes and suspension components, so that I didn’t have to learn how to build them from scratch.
Starting with the rear, the subframe wasn’t tall enough to clear the Porsche transaxle. I knew that going in, but I misjudged by how much. I built a “trellis” on top of the stock subframe, then cut out the original cross bars, and boxed everything back in:

[BDA]

Very interesting! I guess you had to connect the front and rear sub frames together. I'm interested in how you do that.

Thanks for blow by blow. It's very interesting!

[Sofa King]

Yep, on to connecting the sunframes! I set up the rear subframe so that it could bolt in like stock. The front was a little more challenging. I wanted to push the wheels far enough forward to eliminate the inner fender’s intrusion into the foot well, but I didn’t want to have to lengthen the whole shell. As a compromise I cut as much off of the back of each leg of the subframe as possible. That meant that it had to be welded in rather than bolting. I think that worked out for the best, because it made for a more solid structure.

[Sofa King]

The rear subframe is removable, so that it can come out the bottom with the engine and trans axle as one piece.

[Sofa King]

This photo shows the upper perch for the rear coil overs.

[Sofa King]

This is the completed frame after paint. You can see the center tunnel is made from 1x1 tube to add some strength and both the front and rear bulkheads are made from 1x1 and sheet steel. The tunnel is offset 2” to the right to allow the brake booster to be mounted inside the front frame rail. Also gives me more space.

[Sofa King]

Here is a photo of the front section almost completed. The Miata springs mount above the upper a-arms. In order to fit under the Europa fenders I needed to make them more like the Europa a-arms. So I enlarged the opening so that the spring could pass through it, and then boxed it back in for strength.
Also visible in the photo (but not obvious) is the remote mounted electric water pump, and the battery.

[jbcollier]

Not much triangulation in there.

[Sofa King]

Which part do you mean?
The motor mounts and transaxle mounts tie the upper frame rails together, then there is a subframe brace that mounts under the rear section to tie together the two sides of the rear subframe and ties it to the bottom of the rear bulkhead. Also additional bracing was added to the tunnel after this photo was taken. It’s pretty stout!

[Clifton]

I did something similar using mr2 hubs and making a new rear frame and suspension. I love seeing your pics.  I can appreciate how much time you have in it just planning everything.

I'm not a Miata guy but I spent many hours on Miataturbo.net reading about  light, wide 15" wheels and sticky tires.

For what it's worth. Once I got the frame done and engine in and with it on stands, I jacked one corner and measured with a dial indicator how much torsional flex/twist I had. I checked a bunch of spots and I ended up using another 8' of 1"x1" tubing to tighten it up.  I'm not an engineer or frame builder so I can't add anything to what you did though. But I like it.

[jbcollier]

This build features a well triangulated frame:

http://www.lotuseuropa.org/LotusForum/index.php?topic=497.0

[Sofa King]

Gotcha! I have seen similar frames, and considered using similar bracing in the tunnel area. My perimeter framing is 2”x3” .120 wall tubing. Most of my strength is coming from there, especially torsionally. My primary concern was vertical flexing. I have already added 2 uprights in the middle of the long tubes. The good news is that area of the frame is very accessable, so that structure would be an easy add. Thanks.