LocostUSA.com

So, typical story here - long time lurker on this forum but haven't posted much to date. I've been planning this build for a pretty long time - I first discovered Sevens back in 1987 when I bought a copy of "Top Wheels" magazine and there was a feature article about Donkervoort's new IRS frame design - I always thought that was one of the coolest sports cars I had ever seen. Over the years I had daydreamed about building my own car from scratch, but it wasn't until I discovered this forum that I started thinking seriously about doing so.

About a year ago I had just finished construction of my shop and even though I wasn't planning on looking for a donor for a while yet, I heard about a deal that was too good to pass up. I ended up getting a totaled '96 miata along with a complete spare front sub-frame for $420 - and the car only had 25k original miles on it. It was pretty well stripped out already, but the drive-train and running gear was all there, so that's all that mattered. I was still able to sell off a few miscellaneous parts and made the $420 back (FREE drive-train!), and also got $50 from recycling the carcase as scrap metal.

Since I now had the parts in hand, I could start designing the frame and suspension components. A friend of mine, Skip Cannon, happens to own a very nice example of a Caterham SV, and was kind enough let me take detailed measurements from his car. Here's a link to it: http://www.britishv8.org/Other/SkipCannon.htm - back when he first built this car I had helped him out by making some extensive modifications to the transmission tail section, and fabricating the front motor mounts. Since the miata has very similar track dimensions to the SV, it made sense to me to design my car as a clone to the SV in dimensions and proportions, but modify the rear part of the frame for the IRS suspension.

I've been pretty busy over the last year, and probably should have started this log a while ago. I have a pile of pictures I'm going to upload to get caught up, and then I'll continue the log from there. Then I'll try and post something every couple of weeks as I go along. Since I'll be sharing this link with friends and family that have no idea what a Seven is, I'll start out with a couple of pictures of Sevens I admire.

- John

_________________
- John

Pics of the donor.

_________________
- John

While I was starting the frame design, I took some time to rebuild the uprights, brakes and running gear. I discovered the upper pivot bushings on the rear uprights were out of round by over .013", so I bored out just enough to make them round.

_________________
- John

That is a SMOKIN deal on a donor!

I like how you pulled the body off the drive train. Is it worth doing that way or does it take a while to get everything disconnected?

_________________
+442 - Miata

And what are you using to clean parts? Looks like you have a machine shop at your disposal?

_________________
+442 - Miata

for the upper bushing, I made a delrin bushings with a steel inner sleeve. On the lower end, I wanted an infinite adjustment for the toe settings, so I had the idea of making a stepped shaft that slips over the rod end, but is about .003" shorter in shoulder length than the width of the upright - so it all fits together nice and tight. The LCA will have receiver bores to fit the adjusters.

_________________
- John

I thought it was actually easier this way. I think this is how FM does most of their salvage cars too.

_________________
- John

Mostly elbow grease and mild detergent to clean parts - then once they're grease free I sand blast them before paint.

Yes, I have a nice little shop in my back yard. I saved (and worked hard) for 10+ years to build it, but totally worth it!

_________________
- John

Near finished CAD design. With this done I bought some tube and started tacking together the frame. I should say that this is my second-ever welding project. First welding project was constructing my welding bench.

_________________
- John

Some details of initial construction:

_________________
- John

More tubes, and getting initial motor/trans placement so I could build the tunnel around it.

_________________
- John

This is when I discovered my CAD model of the diff didn't exactly represent the actual part.... got lucky and only had to clearance the fins.

_________________
- John

Here's my lower differential mount. Welded steel, with poured in place 90D urethane bushings around steel sleeves. I'll show more on this process later with the motor mounts.

_________________
- John

Initial tunnel construction. I decided to clearance the trans in a similar way that we did for the Caterham. Shaved off most of the PPF mount - this allowed for a symmetrical and much narrower tunnel. I'll end up using the more rearward mounting bracket for a rear motor mount - in a similar way that Westfield does for it's miata based frame.

BTW, the tunnel in a Caterham SV is only 4" wide on the outside, but tapers out wider at the rear. I ended up making mine 4-1/2" wide. I used a mixture of 1/2" and 3/4" square on the tunnel construction and cross bracing. If you look at pictures of the CSR frame, you'll see that almost all of the tunnel and associated cross bracing is 1/2" square.

J

_________________
- John

At this point I spent several weeks finish welding the frame. This is where TIG takes a LOT longer than a point-and-squirt MIG, but I'm happy with the end result. And I'm a much better welder now.

When I was done welding and went to re-install the diff , I realized that I miscalculated my clearances and had to make the rear tube of my "subframe" removable. I should be able to take this in/out w/out removing the fuel tank that I have designed. I'm happy with how the mod turned out.

_________________
- John