Here is Midlana with a traditional Seven rear end which looks pretty good. It has a convenient area on top to vent engine compartment heat yet not be visually cluttered when viewed from behind, and gives room to fully hide the muffler. However, the engine cover that builders chose will be entirely up to them due to strong - and very differing - opinions of what looks best. The book will provide suggestions but not dictate a solution since it's clear everyone wants to do their own thing, which is great! The only question is if hot engine compartment air might swirl forward due to the low pressure behind the windscreen. Or, will air pressure be lower behind the car so it isn't an issue? Guess we'll find out.
What's not decided yet is how much of the bodywork will be removable - and how. It would be nice if the entire rear area could be removed: fenders, rear panel, and top cover, to ease access, something I didn't do so well on Kimini.
Odds and ends.
I've been thinking ahead about what gauges to use. I'd decided upon the combination flat dash and datalogger from Race Technology. With Kimini sold and cash in hand it's all too easy to go nuts and buy really cool stuff, and cool it is. A flat dash, all instruments nicely integrated into one package. Alarms on all the important parameters, a datalogger and GPS, what's not to like - and then a funny thing happened...
First off, Midlana is an open car. The thought of having $1600 of dash and logger sitting there begging to be stolen bothers me. Then there's thinking of it getting beat on by sun and no doubt someday rain. Then there's something else - the economy. I'm surprised to admit it but what's going on is affecting me, like millions of other consumers. "Do I really need this?" No. I'm becoming turtle-like, slowly pulling arms and legs into a shells in anticipation of an economic storm of unknown size. I guess I'm getting older and a little wiser, no longer quick to spend money. Who knows what's coming next year, the year after, or even the year after that. I think we're watching history in the making - what's that Chinese proverb/curse, "May you live in interesting times"? I digress.
So the current thinking is that there's nothing wrong with old fashioned gauges. Looking through all the various tachometers it's a bit surprising to end up right back with the Spa Techniques tach/speedometer that was used in Kimini. It has an odometer which is nice for road use (and just for curiosity.) A nice tach, shift lights, 0 - 60 timer, electronically calibrated, it works well. Stack has a similar "all in one tach" that also has two sensor inputs. However, at around $750 versus $350 for the Spa unit, it's a no-go. For the $400 difference a couple extra gauges will work just fine.
Regarding the engine cover, there are a lot of very differing opinions about what looks best. This part of the build will definitely be left open for each builder to do as they please. I'll provide suggestions but there isn't much point in saying "do it this way" when everyone wants something different. I think it's great that each builder will create a different car; why build a car with plans that dictate ideas you don't like; I think variations are great.
The side inlets are proving difficult to model but there's no much pressure to dump a lot of time into them. At this point it's not so important to produce nice renderings; the ones already posted give a decent idea of where it's headed. Seeing an actual car is more important that a CAD rendering. Time is best spent pushing forward with finalizing the chassis, dimensioning it, and moving toward cutting steel.
Headlights, wipers, taillights. Headlights, tradition dictates the typical chrome bolt-on units but there are some interesting alternatives now such as 2" projector units, though they don't include housings as far as I know. Today I saw some 4" LED(!) "work lights" that might work as headlights but are probably not bright enough. Wipers, ugh, haven't given them any thought; how much does someone drive an open car in the rain? However I realize most areas require them by law. I'm half way tempted to just specifying hand-operated ones sold by hotrod shops. We'll see. Taillights will wait until later, too. While they aren't a big deal they certainly change the appearance of the car. If they go on the fenders it pretty much dictates an external-mount style like the original Seven to stay clear of the tires. OTOH if they go on the body then just about anything can be used. However, they seem so far off I haven't given them much thought.
And finally, I just got another e-mail requesting to be added to the pre-order list and thought I'd mention it. If you want to be on the list let me know. No, there's no free gift for doing so, just the knowledge knowing that you'll be the first to know the moment the book and plans are available.
Using Sketchup components of a Caterham 7 posted to the internet by "terradog", the nose and fenders were borrowed and rescaled to quickly create (very) rough renders of what Midlana will look like. And yes, I am partial to the burnt-orange color that's been appearing on new cars.
There is some discussion about how to style the curved back panel. Thoughts are: nothing (no cover), painted aluminum mesh, aero shaped louvers, an aluminum panel with many punched louvers, or a more traditional Locost back end (thanks to Dean again for bouncing these ideas around.) Regardless what is used, good air flow is key. If there's no clear styling winner then all will be presented in the book and builders pick their favorite - variations are encouraged!
The CAD chassis has been sent to a generous reader to run it through an FEA analysis. The results will only be approximate since stiffening by the attached panels isn't being taken into account, but it should give a good idea if additional triangulation's needed. It also has the benefit of not counting on the panels to be structural. One feature not dealt with yet are the side air inlets just forward of the rear fenders.
Slow work churning through the rear suspension redesign, coupled with long hectic weeks at work.
Adding colors makes an enormous difference for clarity, so much easier to see things. With a rough model of the drivetrain in place it's apparent why tubes are being run the way they are. Note how the transaxle differential housing extends rearward, preventing simpler triangulation. Hopefully - for the last time - the rear suspension is settling down; current total bumpsteer is less than 0.020 degrees over full suspension travel. A few tubes will change and a few are missing but the difficult ones are placed. The diffuser has been enlarged, using otherwise wasted space, currently at 12 degrees. The turbo is approximately where it'll go, though it's unclear if it'll be top or bottom mount.
The large radius rear curvature of the chassis is slighly larger than the rear fenders, visually integrating the rear curved deck and fenders, or that's the plan. The rear wheels and fenders will be rendered to see if it looks dumb or brilliant.
Due to drivetrain placement and the overall shape of the car, there's really only one place the shocks "want" to go, just ahead of the axles. The bottom of the shocks attach to the lower trailing link, but the proposed upper trailing links run right through where the shock body wants to be. While the shocks can go there they would have to lean inboard to miss the upper arms, getting too close to the drivetrain. Since it's unknown what drivetrains will be used it's best to provide as much room as possible. So, the upper links are returning to A-arms...
Mitchell's uber-cool BumpSteer program made short work of determining the toe-links locations, resulting in 0.016 degrees of bumpsteer from 1" of droop to 3" of compression, or about 0.008" toe-change measured across the face of the tire. (A big thanks to my suspension advisor buddy - it's great to have someone to bounce numbers off of who's been through this before!)
I hope this stuff is helpful, though perhaps a bit dull and boring; weeks of going round and round to get everything to work together. Sometimes this means violating engineering practices, such as the lower rear suspension arm having the trailing link intersect the lateral link part way along its span. The shocks will attach near the intersection, feeding a large bending load into the assembly. As mentioned, it'll be dealt with by using large OD tubing and overlapping plates, not a perfect solution but a reasonable compromise. The realities of using existing suspension uprights and clearances with the drivetrain and body sometimes dictate a less than perfect solution. It's all about compromise, which are all over cars, one-offs, and even production vehicles. As long as the reasons are understood and a safe solution arrived at, it's okay, and allows moving on with the rest of the design. This reminds me of what someone said during the Kimini build, about "walking a fine line between doing it right and getting it done."
FWIW, the 20" lateral links provide near-zero vertical roll-center migration in roll - within 0.001" over +/-2 degrees.
Things are busy this week and next so it's a bit slow on updates. It's one of those deals where by the time I get home, take a shower and eat, it's late and I don't feel like doing anything!
However, the parallel trailing arms have been modeled in WinGeo and nothing bad has appeared. I've had a couple readers express concern that moving away from A-arms is a bad idea. What's driving the suspension change is packaging; one reason is that there isn't enough room behind the drivetrain to have A-arms with a base wider than 10" which I feel isn't strong enough. I understand the concern but feel trailing links aren't much different than A-arms when it comes to toe control. No one bats an eye when they have to dial out bumpsteer at the front yet everyone freaks when it's the same situation at the back - it's the same thing.
In the 1960's, F1 cars commonly attached the rear toe-link to the lateral link, so this was tried first - it was terrible, the wheels toing in 0.440" over the full travel! The reason is because as the suspension moves into bump the trailing links pull the upright forward. Since the toe link is attached to the inboard pivot point, the upright and lateral link rotate forward as one about the inboard pivot, leading to really bad toe-in. The trick is to have a dedicated toe-link not attached to the lateral link, resulting in the much better control.
I was reminded that I got in trouble using trailing links once before, with Kimini. However, in that case I purposely designed in rear toe-in in bump. Older and wiser, I know better now and will design in a very small amount of toe-out.
Things are changing - again. After a buddy reviewed the chassis he asked, "Why didn't you use simi-trailing arms for the rear suspension like on Kimini? It's a nice compact layout and allows long links." Um...
It's a combination of things: the forward links can't go too far outboard because they hit the wheels; they can't go too far inboard because they hit the drivetrain; even in-between they hit the intercooler on one side and the alternator on the other; I wasn't sure, due to the simi-trailing nature of the arms, if the camber and toe curves would be polite. Perhaps it was the workload of getting the chassis into the computer that kept me from spending the time on it. Or, perhaps I just got tired of dumping so much time into such a small part of the chassis with little to show for it. Well now that the chassis is (more or less) done it's being redone - again.
The trailing links can be made parallel to chassis centerline if they're attached part way along the lateral links. It's not the best engineering decision though because of the bending loads imparted into the lateral links - unless they're made really strong. This might be an acceptable place for engineering compromise because it solves a number of packaging problems all at one time: it greatly decreases the amount of "stuff" behind the drivetrain; the lateral links can be made as long as I want; because it's then true trailing arms (parallel to chassis CL), there's no toe-steer going on; it also frees up more space for the muffler, an necessary component that easy to forget. The shocks/springs can package fairly straightfoward, but again, only if they're mounted slightly inboard of the lower pickups. Since the trailing links pick up from this area of the lateral links already, it's probably okay - if it's strong enough. I'll run the numbers, but since Kimini had to use 1.25" tubing for the lower tube - without the spring load - it may go as large as 1.5" OD square tubing, due to the separate large vertical and longitudinal loads. Overkill? We'll see what the numbers say.
So if it sounds like I'm talking myself into redoing it again, well, yes. Better this way than to build it from steel and then become unhappy with it. I wasn't real happy about it before, and my buddy's comments pushed me over the brink of redoing it.
In other news, I think I found a bug in Sketchup. Recall I'd been bitching about how sometimes tubes don't "snap" to where they're expected to. I just caught it red-handed; it was easy to see this time because it was in a clear area of the drawing. Clicking on a node I wanted to connect to, it looked like it connected fine, but it was very slightly off. Zooming way in showed that it was snapping to a point in thin air, ignoring the valid node right near it. Huh? Selecting the area confirmed that there's nothing there and yet it wanted to connect. Sigh, going to have to keep a close eye on that.
A major chapter has closed - Kimini was shipped to her new owner last night, read more here.
As this is my first full-blown CAD project, I get to learn all the quirks like everyone else, like CAD's wonderful ability to see everything with such exact precision. The snap-to feature is something I've been using all along and taking - too much - for granted. Move a tube to a junction and it "snaps" to the node, as it should. However, had I zoomed in close, I would have seen that it does indeed snap to a node... just not necessarily the one I intended! So where several tubes come together; the situation's ripe to have an added line be "slightly off" due to snapping to something nearby. The real damage (timewise) is that later tubes carry along the error, building errors the further along I went. My payment for being lax is to have to go back through the entire chassis and confirm each node is truly a singular point. I also noticed that the fuel tank frame doesn't quite fit... huh? Sigh, oh well, another thing that I thought was finished isn't. Add it to the list... but it's coming along, quirks and all.
That aside, the last of the tubes are in place, minus the rack and radiator mount; now it's a matter of figuring out how to optimize all the tubes. After that each tube will become its own component and get the end profiles cut; it's not hard, just very tedious. After that, everything gets dimensioned - that's the fun part - then it's time to start cutting steel! The idea is to build the car from these plans, adding notes and corrections as I go along, so that by the time the car is built there's a known-accurate set of plans. Unlike with Kimini, it means that if Midlana ever gets bent, there will be accurate drawings to make new parts.
Since no one likes the footwell reinforcement (I admit I wasn't sure about it myself), I took it out for now. All this stuff is subject to constant change as it progresses; even after it goes to steel there will no doubt be further refinements as the chassis solidifies. Per a suggestion from Dean, and remembering how I handled Kimini's floor, part of the floor is going to be double-skinned. This prevents the driver's legs from dropping out if the floor panel gets ripped off in an accident. (This is what happened to race car driver Bob Bondurant, so, as with Kimini, it's called a Bondurant panel.) This may change slightly, maybe using smaller diagonals, but you get the idea.
Reader Brian reminded me that there are many race organizations, not just US-based SCCA and NASA. While it's impossible to meet all the rules everywhere, he brings up a good point. It doesn't hurt to review rules from elsewhere and see what's easy to implement. I realize many people won't race their cars in officially organized events - I'm not. But because these organizations learned the hard way about what survives crashes and what doesn't, it pays to follow their guidelines. An accident at 40 mph with an SUV on the street can be just as bad - or worse - than a single-car crash at 100 mph on a racetrack.
I discussed the future fabrication of the turbocharger exhaust manifold with my race car fabricator buddy, Alan. For fun I mentioned possibly using Inconel and was surprised when he didn't laugh. He said it really is the best material to use, build it and forget it, if it's in the budget. It is not, at $200 per U-bend, I'd be spending about $1200 just for tubing! No, can't go there, but I will use 321 stainless. At $40-50 per U-bend it's still expensive but much less so.
Several people have written questioning whether the upper chassis is following SCCA and NASA rules; specifically, how the roof tubes cross instead of running parallel to the centerline of the chassis. I don't think I've broken the rules but would appreciate input if you feel otherwise, especially if pertanent rules can be quoted. The reason the roof tubes cross is to make it easy to get in and out. I really don't want a true boxed-in cage, where getting in and out resembles an old episode of "Dukes of Hazzard", never mind having a girl get in wearing a dress! I noticed with disappointed amusement that NASA, like the SCCA, allows using 1.375" OD "unobtainium" tubing.
So let me know; it's trivial to correct now; much tougher later on, never mind the liability of having a bunch of books in circulation saying to do it wrong...
One of the consequences of designing a car is often not knowing dimensions of components without first having them in-hand. Other times it's guessing about what will fit where and placing orders before all the details are known - that doesn't work sometimes. Such was the case with the floor-mount Tilton pedal assembly. With perfect hindsight, there is indeed room for an overhung top-pivot design, which fits better, is more ergonomical, and costs much less. The good thing is that it makes the overall project that much less expensive to build and fits together a bit better. Hard to argue with that, just wish I hadn't been so quick to order the wrong part, but so it goes.
I've been exchanging ideas with reader Dean, who's comments have helped make the chassis look a bit less dunebuggy-like and a bit more sports-car-like. Never mind the ugly nose, I'm too busy working on the rest of the chassis to create a proper render. Note that the side windscreen tubes now bend directly into the roof instead of around the windscreen as before. The foot of the windscreen frame now extends forward all the way to the floor. I also triangulated the bulkhead around the knees, though it remains to be seen if it'll interfere with the drivers legs or feet. I hope not because it hugely stiffens a bulkhead that's normally left open on most cars.
What's still half-baked is where to run the coolant lines. At the moment I'm back to running them down the center and if that doesn't work out it's back to outside the chassis. My buddy Ron suggested using large 3" angle for the lower outside frame rails and tucking the coolant lines inside, covering them with a radiused cover. That would look really sweet but there isn't 3" to give away outboard of the seats - things are that tight. I can't justify widening the car 6" just for coolant lines so if down the center doesn't work it's back to along the outside of the chassis, covered, ala Cobra side exhaust-style.
Kimini is officially sold; the trailer has already left for the new owner's home in Utah and next week Kimini will make her journey inside a proper transporter.
Blunting the impending emotional loss is the arrival of a Garrett twin-scroll GT3071 0.78 A/R turbocharger, also an emotional item, and admittedly not a necessary component, never mind this early in the build. Its purpose is to serve as an emotional goal, to look forward to hearing it whistling someday :)
The emergency brake system is done. Next is determining shifter, dash, and steering wheel (and steering shaft) placement. This naturally flows into dictating the cowl dimensions. It's all but been decided to use aluminum for the cowl rather than messing around with adapting an existing - but wrongly sized - composite cowl. (The term "cowl" refers to the assembly that houses the dash and extends under the windscreen base, meeting up with the hood.)
I knowingly swapped the Miata rear uprights side-for-side to bias the upper pickup point toward the rear, making it more of a straight shot to the upper pivot points. What I didn't realize was what I was doing to the emergency brake actuators... now pointing toward the rear of the car... doh! Fixed, it's an awkward reach for the upper A-arm, but oh well.
The gas tank is done, complete with hanging brackets, baffles and hose connections. Since it's triangular-shaped, not too much capacity was lost by shortening it a couple inches, improving cable routing for the shift cables and emergency brake. It does lower capacity to about 13 gallons but that's still a decent size and, hey, it lowers the CG a bit, too. Now I know how much work I avoided by not having an emergency brake on Kimini, it's a pain. The good news is that a stock Miata emergency brake lever and cables assemblies are used, no modifications necessary.
Dennis of DPcars.net kindly provided a very helpful link on cooling system design. I learned that a radiator only removes about 10 degrees from the coolant, and that moving the coolant and air faster is better, both of which I didn't realize and hadn't thought through.
Had the day off so good progress was made on the gas tank, either aluminum or stainless, seen here in its protective frame. This fits up behind the seats from below, fastening with only two bolts - pretty sweet I think. Sketchup says it's 14.23 gallons which is a good size. Still to be added are internal baffles, doors, filler, vent, etc, etc.
Reader Dean suggested running the coolant lines along the ouside of the chassis instead of through the chassis tubes. I'm good with that as long as it looks okay. Maybe something like those muffler covers on Cobras but smaller. The trick is finding something that requires little to no work; maybe perforated stainless sheet rolled over a form. I'm open to ideas.
Because space is so limited between the seats, a couple different arrangements are being considered. One rather massive idea is side pods, running the coolant lines through them instead of through the passenger area. Side pods have interesting possibilities: improved torsional stiffness, impact protection, and depending on their size, possibly blocking the line-of-sight path that rocks kicked up by the front wheels take to hit the passengers. They could even possibly provide some storage space. And, from a wishful-thinking standpoint, inverted wings could be incorporated into their undersides, though I'd expect the net effect to be about zero due to the 4" ride height, never mind getting all the dirty air off the front wheels.
They'd really change the look depending how big they are, making the car look much wider and perhaps less dunebuggy-like. It makes sense to make them about a foot wide, the same width as the rear fenders but geez, I don't know. Maybe I'll draw it up in CAD but I think they'll look, um, bad. Side pods look okay as long as they're more-or-less parallel, like on an F1 car, but a Locost tapers towards its narrow nosecone. Having big 12"-wide side pods angling towards each other conjures up odd images, but who knows. Besides the oh-my factor, they also weigh more, cost more, and extend construction time. Frankly, right now I can't see enough benefit to warrant the extra work and expense.
Another way is to run coolant through the lower-outside chassis tubes, now being reconsidered after several people I respect said that it's fine, running hot water down one side and cool water up the other... hmmm. It certainly is the most efficient and lightest way to go, with corrosion inhibitors in the coolant preventing rust. It means that rivets can't be installed into the tubes, though welding on the floor or riveting it to a small angle bracket solves that. There's time to roll this idea around until it settles; let me know what you think.
In other news, the Walbro GSL392 fuel pump, plus a factory Honda RSX-S ECU arrived and was shipped off to be converted into a Hondata KPro tunable ECU. The cool thing is that it'll have a preloading basemap that should work well with my engine components; it "should just start right up"... we'll see.
A little surprising, of the comments received regarding round-versus-square tubing, all the replies were pro-round. So that answers that; the only square tubing will be where it makes sense, for attaching paneling or suspension brackets.
CAD work continues; the latest puzzle is determining how to most effectively get coolant from the front of the car to the back. My fabricator buddy, Alan, says to put the radiator in back; I'd love to but don't trust that there'll be decent airflow through the side radiators. There's already some risk with the intercooler being back there but it's a calculated risk. I'm much less willing to experiment with the main radiator, though.
For routing the coolant, the various ideas are to: run coolant through chassis tubes; run coolant pipes down the center then up and over the fuel tank; run them along the floor and under the tank; or something I haven't thought of yet. I'm not too excited about running coolant through chassis tubes, not so much for corrosion but fear of spraying boiling coolant on someone in even a minor accident (never mind burning someone if they touch the tube.) A compromise is to run a tube-within-a-tube to both protect the occupants and isolate the heat somewhat. However, if the outer tube is on the floor, it's only natural to want to use it structurally and to rivet the floor to it. Having an aluminum pipe inside it means the inner tube will be sitting on the top of the rivets - possibly wearing through - though I doubt that's much of a problem. A good solution is to use stainless coolant pipe because it's much tougher than aluminum, has much better heat-insulating properties, and it obviously doesn't corrode.
Then there's how to balance that requirement against mounting the emergency brake lever and shifter. The shifter is going to be extra challenging because someone (me) designed things so that there's only about 3" between the seats. Either the shifter has to go ahead of the seats, above them, or be made really narrow. I have an OEM Honda shifter assembly and it's, well, huge, about 6" x 10". I might do a subproject and construct one from aluminum and rod-ends, which would look very appropriate in a car like this rather than a huge ugly plastic OEM assembly. We'll see.
Like pushing toothpaste out of its tube, the problems are slowly being pushed out and dispensed with. My brother keeps nagging me about when it's "going to metal" - when the CAD work is done. I'm going to use the plans myself to insure they make sense, dimensions aren't missing, and that whatever I build first will be just like the one that you're going to build ;)
I'm debating the use of round versus square tubing. Many builders prefer square because they say it's easier to cut. On the other hand, round tubing weighs 21.5% less, is equally strong in all directions, and looks nice. There's something about a round-tube chassis that looks... what, smooth, more refined somehow. I've used both types and don't feel strongly one way or the other. I do have a tubing notcher for doing round tubing so maybe I'm biased. Many builders say square is easy to cut with a hacksaw but I don't think they've cut many two or three-d junctions. The worst is a square tube that meets up with two other tubes with none of them at 90 degrees. It forms a tricky three-dimensional cut with each side of the tube having its own angle. Yes, single plane cuts are easy though I read that even two-dimensional cuts drive some builders crazy.
However, I realize the car's supposed to be easy to build and that means having easy-to-follow drawings. Showing drawings of round tubes with curvy ends isn't going to be very helpful; about all I can do is show the overall length. I can "unwrap" the tubes so paper templates can be made, wrapped around the tube, a line scribed, the tube cut, and presto... Only - it doesn't quite work out that way; square tubing isn't really square, the corners are radiused by varying amounts. Also, tubes have finite wall thickness, something that "unwrap" drawings can't take into account. The problem is that the inside of the tube might need a fairly different length than the outside at the same point on the edge. Some tube drawings could take a lot of fiddling to make them work right. (OTOH, many of the tubes have to be round due to being part of the rollcage. So, while a tubing notcher isn't required, there's not getting around dealing with round tubing.)
Also, as Gibbs notes in his book, having tube drawings with infinitely accurate dimensions is very misleading due to welding heat warping the chassis, cut variations, and very slight mistakes accumulating through the chassis such that by the time the builder gets to the other end, the lengths are way off. Regardless, drawings of some sort are needed. I'll probably make drawings for square tubes where there's a choice and let builders decide whether they follow the drawings or use lighter round tubing instead... I know which my car will use. (I should add that using square tubing off-axis, and unwrapping tubes in general, aren't something that SketchUp's particularly good at and takes a long time for each tube.)
In other news, the engine tray won't be removable; Turns out the drivetrain can come out by removing only one tube. It saves a few tubes and does away with half a dozen bolted connections, a dozen screw connections, and all the threaded inserts. The one removable tube will be the diagonal above the drivetrain and will have rod-ends to make sure it fits in spite of build tolerances and heat distortion.
While the drawings may look a lot like the last ones they're more polished and... focused. The engine bay is fairly complete, missing only a couple tubes on the lower panel and engine mounts (the rear one is in place.) I'm working my way forward, making final tweaks and working on tube intersections so individual tube drawings can be made. The upright cylinders at the back are the shocks while the large horizontal cylinder is the muffler - with 3" inlet and outlet ;)
The last picture shows the diffuser. Kimini is very stable as speed - I did something right - so Midlana is getting the same treatment with a smooth undertray in addition to side-exiting radiator ducting. As an open car there'll be more turbulence but it's worth a try and a future iteration might be a hard top!
I've got some good leads on engine builders and Kimini's sale helps that happen; I just have to decide when. The bent roll cage tubes will be the first tubes fabricated, followed by the bottom rails. After that it pretty much depends which end of the chassis is built up first. Starting at the front gives plenty of time for the engine to be done by the time I get to the engine compartment.
And finally, I'm selling two of the shocks, QA-1 DDR7855. They're too long for the rear suspension, but these exact units are used at the front, so consider it the first two components for your future car! Brand new, never used, still in the box, $470 shipped anywhere in the lower-48. Contact me if interested.
Now that the rear suspension is settling down the real drawings are starting (instead of the endless try-this-no-how-about-this-no-try-this-instead thing.) The engine tray is first only because it's the last thing figured out and makes a nice compartmentalized sub-project. I'll probably build it up in steel after finishing the drawings to have a sense of tangible progress. It would be nice to support the engine on it but the design is setup the other way round - to have the main chassis suspend the engine at each end while the engine tray simply keeps it from rotating. I know everyone wants to see pictures but it's pretty dull right now, lots of half-rendered lines on the computer screen is about it.
I may sell the shocks due to them being rather long for my needs; the design changed after buying them. Than again if there's no interest I may just use them instead of taking the loss. I'll have to double-check the fit-up at the front suspension, where the long shock body may actually lay-out better than a short body, one requiring the top shock mount to extend further out from the chassis than it does now.
I'm starting to look for engine builders. Initial contact was so-so; they need to understand that customers have nothing other than response time to judge them initially. When a week goes by before a reply they may as well not even bother in my opinion - they don't seem to understand who writes the checks. If I get annoyed enough I'll just rebuild it myself; the trick is finding a really good machine shop that knows what it's doing and have them do all the precision stuff - I just bolt it together, or that's the theory.
The rear suspension is slowly taking shape. True A-arms will be behind the drivetrain because trailing links didn't work for several reasons, the main issue being the use of Miata rear uprights. Between the wheel offset and upright design, they'd had to angle inboard 30 degrees, fouling chassis tubes and the drivetrain.
The shocks will be in the traditional outboard position, tucked nicely into otherwise-wasted space. The installation ratio was the driving factor, where the initial try resulted in a value of 0.6 - bad news. Compared to a shock which moves the same as the wheel, a 0.6 results in springs having to be 1/(0.6)^2, or 2.78 times stiffer. This would be a real problem because there's roughly 350 lbs sprung weight at each rear corner. A typical soft suspension starting point is to have the springs equal the sprung corner weight which would be 350 * 2.78 = 972 lbs springs, rates that are impossible to source, never mind that springing the car for the track may double that value. I managed to get the installation ratio up to 0.75 but it's still marginal.
The Miata rear upright has two pickup points at the bottom, inline with each other such that a long bolt passes through both. It's natural to use rod-ends, the problem being that the spring force bends the rod-ends radially. A spherical bearing in a welded-in cup will be used, with the other being a rod-end to allow adjusting toe; the upper joint will adjust camber.
Oh, and just for fun I moved some tubes around in the rear area to create a diffuser, much like Kimini's which made the car feel very stable. Of course Midlana being open top will be - to coin a currently-popular phrase - like putting lipstick on a pig - but why not.
The free drawing program Google SketchUp is looking better and better after discovering plugins that make it more than adequate. It's still going to be a lot of work, but that's true of any CAD system.
Our company began a 9/80 work schedule; 9-hr days with every other Friday off and today is our first Friday off - cool!
After some research I've backed away from using an air-to-water heat-exchanger in the engine compartment (for the turbo) with its associated pump and lines to the front where another radiator rejects the heat. These setups work great for drag-racing but for road racing they heatsoak and the overall efficiency takes a dump. Between that and the weight, expense and complexity, a straight air-to-air intercooler will be used, getting air from one of the side ducts. What's unknown is how much airflow there'll be.
It seems like it should be decent since there'll be a belly pan under the engine and the windscreen and curved engine cover should create low pressure behind it. Also, with the side vents being immediately ahead of the rear fenders, there should be high pressure piling up ahead of them. "Should be" means I really don't know for sure; if airflow is insufficient, there's always the McLaren F1 solution. It has a horizontally-positioned engine compartment fan that sucks air from below the car into the engine compartment, blowing it out the back. Doing it that way, the fan could push/pull air through the intercooler at the same time. This means a constantly running heavy fan, something I rather avoid, so we'll have to wait and see. One perk of the McLaren setup is that the fan generates significant downforce!
Yes, an F1/Atom type center-mounted engine air duct has been considered but doesn't seem appropriate. Since the car will have a windscreen it may prevent the duct from working at all, then there's my real reason: the bane of composite construction and having the rear view mirror completely blocked by the duct. I would find it very annoying. On the other hand, my brother says he uses only his side mirrors in his Stalker. Eh.
What the intercooler really does is break the mental block I've been wrestling with, how to handle the rear suspension. I had all but decided to use trailing + lateral links but it means there's zero room for the intercooler (and air intake, and maybe an oil cooler.) This is pushing the design back towards having true A-arms located entirely behind the engine. Now if I could just get rid of the darn rocker-arms!
I've received a few notes that - while being polite - hint at, "What's taking so long, when are you going to start cutting metal?!" As I've said, it's much creating blueprints for a big building. Rushing at this points sets the stage for disaster when I get to the third floor and discover some dire mistake made in the foundation. It has to be right, carefully thought through now so I don't screw myself later on. Doing this paid off big time with the Mini so I'm not rushing this.
The rear suspension is a very tough cookie. Making it easy to build makes creating the first one difficult, not a one-off where anything goes, lol. It's easy to make it complicated... I'm spending hours staring at the mockup trying to come up with a simple and elegant solution and it's hard. I really want to avoid push-rods and rocker-arms but if decent shock motion is to be had there's no way round it.
Changed the rear suspension layout yet again. The shocks have moved to the back corners where they're more accessible and the suspension arms now consist of lateral and trailing links - basically, really big A-arms - all to give the drivetrain plenty of room. Once the decision was made to have the engine tray removable, it's natural to attach all the suspension links to it, and maybe even the rocker-arm pivots. Though things are still in flux the design is settling down, really.
Yesterday was materially non-productive but a fundamental decision was made; the bottom engine frame/tray will be removable. It allows running tubes as needed to produce a strong structure without compromising them to get the engine in and out. The tray will bolt across the base of the main roll hoop and to the rear down tubes - just like Kimini. This stuff is the hardest part of the project, where all the decisions will come back to bite me if they aren't thought through very carefully. Everything that comes after this is icing on the cake!
Being back at my day job gives time to reflect on various design decisions - during break time of course. One consideration is whether to push on with a traditional A-arm rear suspension, or change over to what was used on Kimini, long lateral links and even longer trailing links. Doing so would eliminate one of the two bulkheads behind the engine, freeing up room and simplifying the layout. My only concern is the trailing links, long tubes heading back from the main roll hoop plane to the suspension uprights. In the case of an accident, they might be driven forward into the gas tank(!), or even into the passenger compartment. One solution is to use tall U-shaped channels to attach them to, which also act as "catch fences" for broken or bent trailing arms. The large bracket catches the failed tube and prevent it from passing forward of the main roll hoop plane.
Even if the above is done, it doesn't avoid the need for one transverse bulkhead behind the engine to attach the lateral suspension links to. The bulkhead is a prime issue when it comes time to install or remove the drivetrain. The trick is to have few - or no - tubes that have to be removable; I'm not sure yet if it's achievable.
In other news, if you haven't heard, philanthropist/actor/race car driver/race team owner Paul Newman is expected to pass away within a few weeks - cancer. I had the honor to see him in person once in 1984 at the Los Angeles Times Grand Prix. I was walking through the pits and there he was, sitting on the end of a bench, race suit around his waist, kicking his feet back and forth like a little kid. That's how I'll remember him, someone who obviously really enjoyed what he was doing. When he was out on track, he was just one of the guys, and a very competent driver in his own right. With the millions donated by his "Newman's Own" food brand, he's done a lot to help people. I read one time that he said that he acted in order to fund his racing and I don't doubt it. I enjoyed him most in "Butch Cassidy and the Sundance Kid" and "The Sting" - from a simpler time in Hollywood. Yes, he's had a pretty good ride. I think that's the best we can do here, where when it's over, people say, "you done good."
To end on a higher note, Kimini is virtually sold; the deposit has been received and the buyer has through September to pick her up. Her new home will be Salt Lake City, Utah, where the new owner said that I can come visit her. I might just take him up on that.
Work on CAD goes on and will continue for some time. The easy drawings are first, the ones where tube placement is already known. They'll be refined as tube placements are decided and finalized.
Heard from Mitchell Software... my mistake - big surprise there. I somehow changed the rotation point, an obscure parameter I had a hard time finding in order to set back to zero. How I managed to accidentally get into that menu, set it wrong, and forget doing so beats me.
Between catching the flu and awaiting an answer on strange results I'm getting from the Mitchell suspension software, I'm starting on the CAD drawings - may as well do something productive. Doing the drawings is already proving educational, forcing the need to address tubes that aren't even on the mockup yet. One thing to decide is how to pass the coolant lines, shifter and throttle cables, brake and clutch lines, and wires from the front of the car to the back. Some people have suggested running the coolant lines outboard, but that doesn't really simplify anything. They still need to be covered to avoid burns or having boiling coolant spraying about in case of a cracked line or accident. Even if they were run there, the throttle and clutch lines lend themselves best to running down the center of the car anyway, so may as well run everything that way.
Today the decision was made on where and how the rear shocks will mount.
There's going to be rocker-arms at the rear. Not because it's ubersexy, just that it's the most appropriate solution. Why? The Miata rear upright has its upper suspension pickup cushioned in a big rubber bushing. Putting a screwdriver through the bushing and pulling it from side to side shows that it's fairly soft. I was going to mount the bottom of the shock to it, but applying an offset load of ~400 lbs to it isn't a good idea. A solid bushing could be substituted for the rubber, but one design goal is to avoid lathe-work. On top of that, the steeply-inclined shocks gave too low an installation ratio, requiring spring rates higher than what's commonly available in 10-12" springs. They were also too close to the engine and exhaust for comfort, and that's on my drivetrain. Who knows how close they'd be to whatever drivetrains builders are going to install. Tilting the shocks to be more upright wasn't an option, either, because they'd stick through the engine cover with nothing to attach to. I would have attached the shocks directly to the lower suspension pickup point on the upright, but they'd would have to hang off a bolt in single-sheer about an inch out... won't go there.
The best solution appears to be to keep the shocks away from the drivetrain and keep them low. While putting them behind the drivetrain makes them accessible, the exhaust is back there, too, cooking anything close by. For these reasons they're being placed vertically, about a foot forward of axle centerline.
Speaking of the rubber bushing, if a single rod-end is bolted to one end, it'll twist the bushing. If a U-shaped bracket is used so a bolt passes all the way through the assembly (like a Miata) then it'll both bind slightly when toe is adjusted, and move "some amount" during cornering. I'll probably leave it as-is until I figure out how much of an issue it is.
With the front end sorted and the axles having arrived, attention returned to the rear suspension. Push-rod rear suspension was almost considered a requirement, but after spending hours staring at it and trying different solutions, an old-school shock layout was found. However, it's very tempting to modify the Miata upright to make it work even better, but that has to be thought about a bit more.
It's not easy routing the chassis around the engine, and while a de Dion axle layout makes things simpler, I don't want to settle for almost-great, may as well do the best I can. A true independent suspension is also the most flexible, for those builders who want to tinker with things - or just leave it as-is.
One thing I've been ignoring is how to remove the drivetrain; haven't decided if it's coming out the top or the bottom. I kind of like the bottom-exit solution because the drivetrain doesn't have to be lifted in and out, scratching up chassis tubes. Just wheel something under the car for the engine to sit on and lift the car up off it. Either way it means some of the tubes need to be removable, just haven't decided which ones yet.
I have two more days to get everything sorted (before the wife comes home) and I think it's doable, at least by the end of the weekend. Well, "sorted" in the sense that tube placement has been decided, then it'll take weeks to put it all into CAD. I'm concentrating on only one side of the mockup; no point doubling the work of making the other half.
I realized that it's impossible to go straight to steel without completely recording every dimension. Since I don't have space to set the mockup aside once steel construction starts, it has to be chopped up for firewood before I can. If I missed some critical dimension, well, that would be unfortunate. For that reason it'll go to CAD first. Now that I'm nearly out of the hardest part of the project, I'm starting to change my mind on how to do mockups. That is, I now think it would be easier and maybe even faster to do it all in CAD ("next time") though detailed dimensions are still needed of all major components.
While taking Cooper for his morning walk, we had another encounter with an animal. Much like the ferret from a few years back, we were walking along a trail and out of a bush came a light tan and white rabbit. It must have been someone's escaped pet, due to the coloration and also because he walked right up to us. I thought of picking him up, but then what? Cooper, who thinks rabbits taste wonderful, had never had one actually walk right up to him - he didn't know what to do. When he finally decided that it might really be a rabbit, it took off when he barked at it. Hope the little fellow finds his way home; being in the wild with white markings is like having a bulls-eye on your head.
Changed the side tubing placement slightly; I'd been trying too hard to achieve some sort of "look" instead of pure function. I finally relented and just let the car design itself - like what happened with Kimini - and put the tubes where they want to go. What it means is that the car might end up looking "like an engineer designed it." Be that as it may, all the tubes are right where they need to be, making the chassis lighter, cheaper, easier, and faster to build. Over the years I've been listening to what builders don't like about Locost chassis fabrication and designing mine to avoid the issues. For example, builders complain about the PITA (pain-in-the-ass) compound cuts at the front of the Locost chassis. I made sure mine only requires single-plane cuts :)
One slight contribution to looks is that I raised the base, and lowered the top, of the windscreen to make it look less dune-buggy-like. It also had the side benefit of moving several tubes right to where they are needed, which avoids additional tubing. I'm trying very, very hard to make the chassis as simple as possible. It's easy to make a complicated chassis... but very challenging to make a simple one!
I took this week off to push through the toughest part of the design, the front suspension/radiator/master cylinders/steering rack area. I'm thinking that in a day or so it'll be time to start transferring numbers into CAD.
Here's the axles, twin-disc clutch, radiator fan, and a poor shot of the new chassis layout. Connecting the axles to the Miata uprights and Honda drivetrain for the first time made me very nervous, wondering if I'd screwed up the specs somehow, but it all went together fine (whew!) They're rated at 450 hp - to make sure there are no issues with the turbo engine!
I'm backing away from using push-rod suspension; "simple, cheap, and easy" is going to win out. The more suspension motion that's needed, the more volume is consumed in the chassis for the rocker-arm, and with 6" suspension travel, the arm gets too large, never mind the weight. If the shocks are located down low, they cook in radiator exhaust air and crowd the master cylinders. Moving them up out of the air duct, raising them so that they're visible to look cool is poor form due to raising the combined 14 lb weight so high. And, placing them parallel the the centerline of the car means increased side-loading on the rocker assembly due to the push-rod changing angles. A rocker setup weighs more, costs more, and takes longer to build. Eh, I think I want to go simple on this car.
Push-rod setups do look really sweet, but the reason they're used on F1 cars has nothing to do with looks; it's to minimize the shock's aero drag - a situation we need not worry about. (F1 cars also have suspension motion on the order of 1", not 6" like we have.) The one valid argument is that rockers can greatly improve installation ratio, where the shock can be made to move 1" when the wheel moves 1". With a traditional outboard arrangement, the shock may move much less than the wheel so stiffer springs have to be used. Since the shocks don't move much, there can be issues with stiction of the shock valving. However, this isn't a problem here because of how much suspension travel we have.
After moving the parts around in CAD, it's not bad. The installation ratio ends up about 0.6, so the spring rate has to be about 2.8 times as much (installation ratio squared.) It means that while the wheel moves 6", the spring moves about 3.6". A 1"-thick bump stop brings total stroke to 4.6", and since it's good to have some overhead, the same shocks will work fine. Checking the effective wheel rate shows a gradual rising-rate, just as desired.
In other news, I took the transaxle and Wavetrac LSD to a shop to have the LSD installed. I don't know how many of you've seen the movie, "The Fast and The Furious", but this place, and the customers, were right out of the movie. That said, the mechanic was amazing to watch. He had the tranny apart in five minutes and it's good he checked it because there were several things wrong. First, one of the shift-rod ball-detents was broken. Second, transaxles have a magnet in the sump to trap metal debris. The previous builder apparently didn't know how to reinstall it and guessed - wrong. When we opened it up it had attached itself to the final drive gear! Good thing it hadn't been run. Anyhow, he completely disassembled the gear clusters, closely inspecting each gear and syncro. They all looked good except for third gear which had sharp burrs on it from overzealous shifting. He said reusing the parts could cause it to jump out of gear - no thanks. I left it to be repaired properly.
The decision's been made, out came the saw and off came the bottom radiator pipe. The decision was make easier after realizing that there are other radiator modifications that need welding, so what's one more? To fit the radiator under the nose, the filler cap flange is being replaced with a low-profile water bleeder. (The cooling system will get filled through a header tank back in the engine compartment.) Mounts are also needed, too. All the welding can be done at one time and transform a nearly-impossible-to-work-with-awkward-assembly into something that fits really well. It'll be well worth the bother.
Worked all day on the front chassis area, probably the most complicated part of the entire design. Kind of like juggling a bowling ball, flaming torch, chicken egg, frog, and a running chainsaw, there's the nosecone, steering rack, cooling fan, duct-work, and suspension pickup points. It's easy to deal with these one at a time, dedicating tubes to deal with them separately. It's about 100 times harder to use one tube to do two or three different tasks at the same time, very tricky! It'll be worth it - after it's done - in the form of fewer tubes doing the work. No pictures; it's just a bunch of half-finished wood pieces at various angles - not much to look at. I plan on taking a week off soon and will dedicate the entire time to finishing the mock-up.
After the mockup's complete, is the task of getting it into the computer. It's the only way to force myself not to cheat, taking measurements off the wood and going straight to steel without writing the numbers down. Come to think of it, that's not all that bad... and might actually be a good idea. If I go to CAD first, then build the steel chassis, I risk following mistakes and wasting material - and forgetting to make the corrections on the CAD drawings. If I build the steel chassis first, then take measurements, it guarantees that what's there is really what was built, not numbers that were later changed and forgotten about. Hmmm, maybe cutting steel is not as far off as I thought...
Ordered a muffler to make sure there'll be enough room for it and its associated pipes. Because a turbocharger acts as a muffler, too, a smaller muffler can be used, but since most people will run a normally aspirated engine, I have to save room for a larger unit. Since neither the muffler nor axles are here yet, the rear suspension area is on hold, so attention moves to the front suspension.
Installed the radiator and - as many Locost builders discover - the lower radiator pipe interferes with the steering rack in a big way, like, going right through it. The choices are to move the rack, move the radiator, or move the radiator outlet. Car design is all about compromise, but moving the rack is a really bad idea since it messes up both Ackerman and bumpsteer. Another way to improve clearance is to move the rack (and wheels) back, shortening the wheelbase. It's currently 96" and while there's nothing magic about that number, it gives a warm fuzzy 1.6:1 wheel-to-track ratio. I have to think about it.
Then there's moving the radiator pipe, and since it's a big 1.75" diameter that's already pointing the wrong direction, it's very tempting to move it. I'm reluctant to do this because it means builders will have to weld aluminum, or pay to have it done, something I'm trying to avoid. And finally, the nose and radiator can be moved forward to free up space... but I find this solution offensive, lengthening the entire car by 4" just to avoid one aluminum weld. I just can't bring myself to do that.
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.
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.
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!
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 - ruins the lines, I say. Fun stuff.
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.
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.
Lowered my price on Kimini to $25,000. I don't plan on any future price cuts.
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 still 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 (in the Sources link.) 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.
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 K-tuned 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.
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.
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.
A busy weekend. Saturday the table was finished, attaching the remaining panels and lifting the heavy *cough* bastard *cough* onto the sawhorses. Borrowed the engine hoist and scales from my brother so I could answer a question that's been bugging me for a long time: what are the drivetrain component weights? I expected it to be about the same as the Honda H22A1 I used in Kimini, or about 475 lbs. This engine's basically the same, in fact it's a bit larger, 2.4 liters instead of 2.2, so it seemed fair to expect about the same.
So what does a Honda K24A1 weigh? Engine + exhaust manifold + alternator + starter = 283 lbs. This does not include the flywheel or clutch (I have neither), nor engine mounts. The 5-speed transmission weighs 87 lbs + 10 lbs for the intermediate shaft, for a total of 381 lbs. Figure 8 lbs for an aluminum flywheel and maybe 15 lbs for the clutch. As far as I can remember, these are the same parts included when the H22A1 was weighed. So the grand total is 403 lbs, which is pretty awesome, a lot lighter than the H22. Of course neither total includes the engine mounts and axles but I'm pretty happy. It nicely lowers the weight by ~70 lbs and moves the CG further forward, now at an estimated 40/60 front/rear. I'm happy.
On the floor alongside the table is the bundle of wood that will become the mockup. I'll buy some plywood to make 90 degree "bends" for the cage, but things are moving along. I included a sketch (preliminary) as a teaser so you can get a feel where things are headed :). The last shot was after I turned off all but one of the lights, the first parts of the puzzle on the table, awaiting their buddies to become something pretty cool.
Regarding the next book, I'm considering a "cookbook" binding so that it lays flat, convenient for the garage. OTOH, it doesn't look quite as professional to me, and the kichen-type cookbooks we own have an annoying habit of not standing upright in a bookcase, slowly sliding down and either warping or falling over. I realize this is getting way ahead of things but I'm wondering what you think, if it even matters.
The last diary has been moved to the Old Diaries folder.
Kimini is in storage, freeing up garage workspace (I almost thought Kimini was going to sell last Saturday, but oh well.) After a very long (and of course, hot) day the table is mostly done, leaving only the top surface left to to install. It shouldn't have surprised me how heavy the table is; it's a beast, enough that I had to get two neighbors to simply turn it over. As construction progresses we'll see how smart it was going to the effort and expense of a 5' x 10' table as opposed to a 4 x 8 that would have been easier, cheaper, and lighter. Oh well, I won't be whining about not having enough table space.
What's with the hole in the center? Since it's a 5 x 10ft table made from 4 x 8ft sheets, some puzzle-solving resulted in using three full sheets with no leftovers. It did result in being four square feet short though, so the hole has been labeled an "access port" if I have to get up under the chassis.
The big pile of boxes behind it are parts: engine, tranny, seats, pedal cluster, fenders and nose which will go on the table and everything else going underneath. Got to free up floor space so I can move around.
Once the parts are in place it's a matter of getting everything where they're supposed to go and see how it all fits. As was done with Kimini, I'm going to resist (very difficult) going straight to steel and will instead build a wood mockup. It saved so many goofs and much heartache that it more than makes up for its time and cost. I can see the design in my head; it's now a matter of fine-tuning the details, especially since plans will be based on it. Much like Kimini, it has to be right the first time.