29 Jul 2008

Carefully measured where the rear Miata hubs are positioned relative to the drivetrain so that axles can be ordered. It does little good to have the suspension just right if the arms hit the axles, the axles hit the chassis, or the CV boots rub on something, etc, etc. Since I have neither Honda nor Miata axle parts on-hand, it’s hard to know how much room to give them. I rather just order the real deal now instead of wasting money on used axles parts that won’t get used other than for mock-up. I refuse to weld a Honda and Miata axle together, so instead, a custom axle set will be assembled by a specialty axle shop.

28 Jul 2008

Here’s a few pictures. It was a little depressing that when my brother saw it, he used the dreaded “D-word”, dune buggy. I was warned about this, that after putting everything where it has to go, what else could it look like? The culprit is the roll cage, but I’m not designing it out; it’s there for good reason. I’m pretty confident that the side panels will downplay the dune buggy…ness.

The very unfinished front end is fairly straight forward because the nose drives the design. In fact that’s why it’s unfinished; after seeing it was all going to go together pretty well, attention turned to other areas. The back is a different story. As with Kimini, the drivetrain is a challange to design around; it’s not hard, just challanging. The “tubes” at the back are already different than in the pictures. Once the hub was put in place it revealed a faily major goof involving wheel offset; I think I inverted the wheel offset, which is important to get right! A small subassembly will contain all the inboard suspension pickup points and the rear engine mount which will get triangulated in with the rest of the chassis.>

I have’t figured out which tubes will bolt-in so the engine can be removed. At first I though I’d place the tubes on the parimeter so that the body panels attach to them, but that’s not where all the strength is needed. The main tubes have to move inward and downward toward the suspension pivots. Once that decision was made, it was pretty easy to picture a small-tube framework to support the panels. It’s not a bad thing since the load-bearing tubes won’t have holes drilled in them for rivets, something that seems to upset some people ;).

I’m considering changing how the rear shocks connect, changing them from a push-rod/rocker-arm setup to attaching them in the traditional manner, bottom on the hub or lower arm and top on a chassis tube intersection. They package nicely, are fairly easy to get to, lower their CG by about a foot(!), and not fabricating a rocker-arm assembly saves time, money, and weight. The downsides are not having 1:1 wheel ratio, (but it’s close enough), and having the shock mount in single-shear, sticking out the side of the upright by about 1.5″, a lot more than I’d like, but we’ll see.

The last picture, with the dark masonite panel with the curved edge, gives an idea what the rear bodyline will be in side-view. The shape is purely functional; the curvature matches the rear fender radius with a small buffer for the bodywork to smoothly curve up over the chassis.

Sorry for not having more whole-car shots; the garage doesn’t let me back away far enough. Also, I tend to work on one side and ignore the other; since it’s a mirror-image, why spend the time? The original idea of curving the side-panels inboard to serve as engine inlet ducts may be changing again (check the renderings posted some months back.) In fact, the same panels may now curve outward slightly to give more elbow space (unlike a Locost, the passenger’s arms are inboard.) Depending how it looks, I may go back to the original idea of having the air duct be immediately ahead of the rear fender. I’ll make sure to fully finish the right side of the chassis so I can get some decent pictures with the cardboard panels in place.

Other odds and ends, the empty area behind the seats is for a triangular-shaped gas tank with upto 15-gal capacity. Also note how close together the seats are, just enough room to run the bare essentials to the front of the car. I’m still going to have a cover of sorts because I don’t want anyone getting burned if a coolant line springs a leak, or simply resting the side of their foot against a >200 deg F tube!

22 Jul 2008

Decided to make the chassis 2″ wider just forward of the seats. The trick is tapering the chassis toward the nosecone with the same angle as the nose itself so it doesn’t look goofy. Said another way, it’s aesthetically important to continue the taper of the nose back along the sides of the car without the chassis suddenly widening and ruining the lines, I say. Fun stuff.