30 Jul 2008

Ordered the axles, knowing that if I mess up (like when building Kimini) they’re going to be worth exactly zero if they don’t fit, due to them being for my quirky one-of-a-kind application. However, I double and triple-checked the numbers so it’s time to get on with things.

Hanging out on the various Honda and Acura sites sometimes pays off in the form of good deals. Picked up an adjustable fuel pressure regulator, braided fuel lines, fuel rail, 750cc injectors and clips, and a throttle-body. The throttle-body is needed because some late-model engines – like this one – are “drive by wire.” The throttle body doesn’t have a throttle position sensor because the computer knows the position it drove it to. Taking the stepper motor off is easy, but now the aftermarket ECU can’t know throttle plate position. The solution is to substitute a throttle-body (and an engine wire harness) from a similar model that uses a traditional cable-operated throttle.

Oh, and good news on the twin-disc clutch – it’s fine. That’s a relief.

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.

21 Jul 2008

Work progresses slowly on the wood mockup. The tricky stage is right now, where placing a wood rail has many consequences that have to be thought through as early as possible. For example, it’s unclear if there should be a break in the side rails, about mid-shin, to gain a few precious inches in width. The seats have robust shoulder bolsters that make it tough to set them side by side; the bolsters hit and the resulting stack-up really fills the width of the chassis. One idea is to offset one seat relative to the other fore-aft so the bolsters overlap some, but it won’t be clear how it’ll work out until things are further along. It’s good to deal with this now, using wider seats and getting them to fit, instead of hearing later from many unhappy builders! I’m hoping to have the basic cab done this weekend when I can show pictures of something other than just a couple pieces of wood.

One cool thing about a wood table is that it’s so easy to fasten down the wood, just run sheet rock screws through it. It’s nice because they can be carefully placed – once – and screwed down, never wondering if they’ve moved afterward. It’s actually better than a steel table where the tubes are clamped down. Bump the tube once and you can never really be sure if it moved or not… which requires remeasuring if you’re really paranoid, like me.

Got a great deal on a lightweight flywheel and twin-disc clutch – maybe. The previous owner said it caused the crank thrust washer to fail, the question is: why? Clutch throw must have been set wrong but then why don’t other people have the same trouble? For peace of mind it’ll be sent back to Competition Clutch to be checked out, especially to see if it’s the correct unit for my engine. Also picked up fuel injector connectors for the bigger-flow aftermarket injectors.

16 Jul 2008

Stopped by an off-road shop, one specializing in fabrication parts for dune buggies, Jeeps, and hard-core off-road race trucks. Boy, things have changed since the last time I was there (to buy Kimini’s steering wheel 10 years ago). They have all sorts of cool fabrication parts: rod-ends, tube thread inserts, gussets, fuel cells, steering and brake components, and aero-type plumbing fasteners. They were a treasure trove of information about who in town bends tubing (for fabricating dune buggies and race trucks). I checked out everything they carry and left with a Momo steering wheel and quick-release hub adaptor. I bought that particular adaptor (made by Sweet Mfg.) because it had virtually no play, very surprising for a spline-type adaptor. While all these parts are on the Web, sometimes it’s nice to be able to hold a part in-hand and test it for feel.

Waiting at home was the radiator along with a case of construction paper. Yes, big sheets of the material of what’s on the back of a pad of paper. I got a great deal – 70 sheets of 26″ x 38″. I went through a lot of it during Kimini’s build and it’s well worth the investment, using it for patterns and simulating paneling on the mockup.

This about does it for the parts needed to build the mockup. Now it’s just a matter of placing frame members everywhere the major parts aren’t… Some tube placement isn’t critical, which allows aesthetics to decide position. I’m looking forward to completing the basic layout and stepping back to see just what it looks like.

A reader suggested that I encorporate an RSS feed for this site, a good idea. I just have to buy the plug-in for Dream Weaver and find the time to hook it in. For those who don’t know (I didn’t), an RSS feed means you receive notification of when my site (or any site) has been updated since your last visit.

13 Jul 2008

Started in on the wood mockup. With Kimini I had a crutch; the pre-existing shell confined the chassis so I couldn’t mess up too bad. With Midlana, I have total design freedom, a mixed blessing. I haven’t cut too many “tubes” yet but am already changing things. It’s nearly a hard requirement to have all the major parts on hand; it would have taken a ton of time to do all of this in CAD, then a mockup would <em>still</em> be needed. The changes being made aren’t anything major, but it’ll be easier, simpler, and lighter to build – I doubt anyone minds. The part in question is the bodywork covering the front face of the rear fenders. Right now it “looks” simpler to just leave it out, more like a tradional Seven. Of course that means rocks will beat up the fenders just like in a Seven, so we’ll see. Regardless, the side air inlets will stay, ducting cooling air into the engine compartment.

Ordered a radiator, a sweet two-row, double-pass, aluminum unit. It, like all the other parts already on hand, are needed, now, to find exactly where to put all the tubes. I’ll post a few pictures this week.

11 Jul 2008

The Honda, like most modern engines, uses one long serpentine belt to run everything. Since Midlana doesn’t have power-steering or air-conditioning, the stock belt setup won’t work; simply using a shorter belt won’t work because the routing counts on the accessories to change directions. An alternator adaptor from┬ák-tuned.com relocates the alternator to where the air-conditioner was, down near the pan, nicely lowering the CG about a foot. I ordered it now because it’ll absolutely be needed, and it’s good to have a solution now for one of the nagging issues before it’s a problem.

Ordered a Mugen oil pan which solves the oil starvation issue these engine have when run at trackday events. Researching the oil issue, while half a dozen pan makers claim to have eliminated oil starvation, only the Mugen part seems to have really done so, as attested by their customers, who grudgingly admit that while it’s expensive, it does indeed work. They got my business because I don’t want to spend time solving an oil starvation problem using my motor as guinea pig when I rather be enjoying the car. Since Mugen produces true road-race components in Japan and their cars usually win, that’s good enough for me.

10 Jul 2008

Most steering racks are measured in “inches per turn”, the amount the rack moves with one revolution of the steering wheel, yet no one seems to know what the Miata rack speed is. So finally getting around to it, the Miata’s various hydraulic lines were removed and the rack cranked to one end. Backing it off by exactly one turn showed the speed to be 1.77″, a surprisingly fast rack for a modern car. (Kimini’s Triumph Spitfire rack is about 1.8″/turn.) That’s a good thing because there was a concern that my “sports car” might turn as slow as a Lincoln, you know, about 10 turns lock-to-lock. (A bit of an exaggeration, but not by much. We rented a Lincoln for a trip once and the brakes, seats… and steering were terrible.) Anyhow, it means Midlana will have fairly quick steering – as intended. Also, the rack appears to be in good condition, with no slop in the assembly.

8 Jul 2008

The sawhorses supporting the table are rated for a combined load of 2400 lbs, so “technically” there’s nothing to worry about. However, the rating is apparently a laboratory-tested value using a static vertical load. However, if it’s a real-world load that is sometimes bumped side-to-side – like a car project – the wobbly, spindly legs don’t endear much confidence. After a reader mentioned a builder’s table collapsing, it pushed me to add two 4 x 4 legs with cross-bracing at the heavy end of the table now before things get heavier. Better safe than sorry.

I can already tell that making the table 60″ x 120″ wasn’t a luxury; any smaller and too much of the chassis would hang off the edges. I thought (for what, a day?) that maybe a 4 x 8 ft table would have worked – nope. While the wheelbase is 96″, the overall length of the car is about 11 feet; good thing I didn’t cut corners. BTW, one good sign of how stiff the screwed-and-glued table assembly is, was when the drivetrain was sat on it. Not one pop, creak or crackle. Good.

Speaking of getting the engine on the table, I turned the crank several revolutions with a wrench. It was reassuring to feel the compression in each cylinder – no sudden clunks or scraping sounds. Another concern averted.

As a fun side project, the selection of turbochargers is narrowing down. I’m fully aware that a turbo isn’t a requirement, much less needing it now, but at least once, I’d like to own a powerful rear-wheel-drive turbo car. I realize a turbo can make a car slower at the autocross, and potentially only a little faster at trackday events, but you know, I don’t care. This car’s all about having fun. I’m not building an F1 car, trying to win an SCCA national championship, or even a local autocross event. It’s for fun. I might even buy the turbo early as motivation, an awesome component to serve as a goal, to provide a suitable platform worthy of its inclusion.