Need tiny seats? Look in a Midget!

I made a big step this week to increase the British content of my locost by purchasing a pair of 1972 MG Midget seats.

The previous owner had them leftover after restoring his Midget, which he graciously let me sit in.

These seats are small (about 17-18" across) and relatively light (24 lbs. each). Plus they will really make the interior look "period correct".

My plan is to recover them once the car is done in MG's Autumn Leaf vinyl. I figure with a matching tonnau cover, tranny tunnel cover and dashboard it'll really look awesome against my off-white and navy blue paint.

Putting them side by side in my garage at their approximate spacing really drives home how small the passenger compartment will be. Awesome!

Now that I have my seats, I have every critical piece I need to design the car. I've been waffling on doing a detailed design phase and I'm pretty sure it is going to be a go. It will keep me busy while I finish renovations to my garage (including building a garden shed to clear out all my lawn stuff) and prevent costly mistakes later.

Bought a radiator fan

If you're paying attention to my Spartan 7 specification sheet, you'll notice that I had both the radiator and radiator fan on my design-phase purchase list. The reason is that I've seen several builders struggle to package the radiator into the nose of their builds, and I wanted to avoid this entirely by designing the front of the frame in advace around stock components.

Since I have an aftermarket Honda Civic radiator, it makes sense to use the stock fan, motor and shroud assembly. After all, they were designed to fit together, designed to work together and the stock radiator fan assembly provides enough cooling for engines as powerful (or more so) than my Miata donor's.

I purchased this unit off EBay for $35 or so. I was looking for a used unit, but all the local yards had been picked clean and I suspect this is a part that has a limited service life. It was only $20 more to get a new one, so I took the plunge.

The overall unit is a little bulky, but I like how clean and "factory spec" the final result looks. As I get deeper into the design phase we'll see if I can wrap a front end and nose cone around the assembly.

Next time I go to a junkyard I'm going to snip off a stock Honda connector for my wiring harness. That way I can put in a drop in replacement should the part ever fail.

First Autocross!

This weekend I competed in my first ever autocross!!! A friend invited me to hit the cones with the local Porsche Club of America chapter. Does everyone else know how much fun this autocross thing is?

Seriously, I've never had so much fun driving a car! My hands were shaking after each of my runs, and was pretty winded because I kept forgetting to breathe. Fortunately the course was only 3/4 of a mile or I would have passed out! I have never driven a car so aggressively before.

I'm pretty proud that each of my runs was faster than the previous. That was my goal for the day, to show continuous improvement. I didn't get anything close to FTD, but I was thrilled to get FTJ (Faster than Jeep). I've spent most of the last 24 hours lost in thought of where I left time out on the course. I can see how easily it is to become obsessed with this stuff.

As for my car, she did the job despite having crappy tires and worn-out shocks. I've never been truly at the limit in my car, and I have to say dancing that Miata around the cones was a religious experience. It has always been a major goal for the Spartan to have the same driving qualities as my Miata. I think if I get even close to having the same dynamic qualities it'll be a major victory.

Locosts predominantly race in the D-Modified class in SCCA autcrosses. There are a few details in the regulations regarding construction that I should look into when designing the frame, but otherwise nothing is really different from what I was planning anyway. There are a few tidbits for cars running slicks that I should pay attention to when putting the car together in case I go that direction for competition.

In any case it doesn't look like the Spartan as planned will be competitive in D-mod nationally, and perhaps locally if I'm up against purpose-built hardware. That's not the point of my build, though, and designing to a specific set of rules will probably result in less angst when some stickler techs my car.

Keeping track of things

Being a nerd, I like to keep track of things. Excel and I are on a first-name basis. So it's natural that I'd want to accurately document my build.

Even though the Spartan won't be an absolutely low-cost locost, I still want to keep track. Some have suggested that this is a crazy idea, as it gives my wife real numbers to yell at me about. Fortunately for me my wife is really cool about this obsession of mine, so I feel comfortable keeping a budget spreadsheet with the actual figures for my build.

I'm going to count the full purchase cost of partial items. That means if I use 10% of a $4 tube of grease, it'll be $4. I don't want the pain of tracking how much welding filler wire I've used. The spreadsheet will also break out shipping and tool costs and list sources for each item. I figure that may help someone else understand how I got those figures.

While I've been waiting to start my build I've been reading like a banshee. I've also scoured the internet for anything I can learn about building a car. Along the way I've made lots of decisions about components and specs for my car. I've decided to keep a specification spreadsheet (xls) listing what I plan on incorporating into the Spartan.

Both documents are now on the sidebar, and they'll be constantly updated as I go along. You're free to copy and use them as you see fit.

And so it begins...

My first ever component just arrived. Behold, the Spartan's steering rack!

I was alerted to a good deal on Ebay by an astute member of the LocostUSA forum. I'm not entirely sure it'll be what I need, but at the price I picked it up for it was too good to pass up.

Here are the details:

Appleton p/n: 7010410
18.25" width, tapered ends
2.5" travel per turn
4.5" total rack travel
17 lbs.*

The factory specs say that this unit weighs 17 lbs., but the shipping label says it's 14. I'll have to get a scale to make sure.

If you've been reading this blog, you'll remember that I'm not inclined to cut and weld a normal automotive rack. It's not that I think it's a bad practice, I would just rather spend a little more and know I've got a reliable unit. Losing steering control at speed doesn't sound like fun.

This rack isn't as nice of a unit as a Woodward rack, as you have to replace both the outer housing and the steering pinion to change the ratio. There also seems to be a bit of friction in the system, possibly due to the fact that the rack and pinion spacing are determined by the manufacturing tolerances of the housing, not some fine adjustment. I may be off base, but Staniforth claims that a good steering system will allow you to move the front wheels with one finger. Maybe he's a little used to high-buck purpose-built cars. I'll wait until I can inspect a stock Miata rack before I pass final judgment.

In any case I got such a good deal on it I figure I can still recoup most of my costs by selling it on Ebay if it doesn't work out. Besides, I've come to learn that a companion hobby to working on cars is collecting car parts.

Even if it's only one part, I'm still pretty excited about what this represents - my first tangible component of my car. It's all uphill from here!

Comparing Dimensions

I've been reading the excellent Lotus Seven & the Independents, and one thing I'm struck by is how much variation there is in the critical dimensions of various Sevenesque cars.

I've compiled various measurements for the two common Locost platforms as well as for three baseline Sevens and a few lightweight sports cars. I've also thrown in weight and horsepower numbers for reference.

Car	Overall			Track		Wheel base	Ride Height	Weight	HP
	Length	Width	Height	Front	Rear
1962 Lotus Super Seven Series II	131.5	56	39.5	47.5	48.5	88	6	924	85
Haynes Roadster (Gibbs)	129.5	67	46	56	57.5	94	3.9	1309	105 est.
Keith Tanner's CMC Miata-Locost	128	65.5	42.5	51 est.	56.2 est.	92	4 est.	1279	175
FM Westfield	131.5	63.4		55.5	56.2	91.5	5.75 est.	1300	125
2006 Caterham CSR Superlight	129.9	66.3	40.0	59.3	57.7	91.1	3.9	1245	260
1993 Mazda Miata	155.4	65.9	48.2	55.5	56.2	89.2	4	2222	116
1974 MG Midget 1500	141	60	48.3	46.3	44.8	80	4	1631	65
2003 Ariel Atom II	134.3	70.8	47	63	63	92.3	3.5	1005	220
1957 Lotus Eleven LeMans	139	60.5	31	45.5	47	88	4.5	1360	84
2000 Lotus Elise	147	67	45.2	56.7	57.9	90.6	6.3	1574	143
1964 Austin Mini Cooper S	123	55.5	53	52.8	46.9	80	6.3	1250	70

Click on the car's make and model for the sources for my data.

The first thing that jumps out to me is how tiny the original Seven Series II is. The Caterham is nearly 10" wider than the original car. Of course a lot of this is wider modern tires, but it's still significantly smaller than anything on the road.

The other thing is how much longer the wheelbase is on Gibbs' Haynes Roadster vs. every car in the table. If you look in the Haynes book, the front wheels actually stick out past the front of the nose cone! Since my frame design is based on the Haynes Roadster, reducing the wheelbase to 90-95" is going to be one of my design priorities.

I'm going with the stock Miata front and rear track on my Locost (as of right now), so the width of my finished car should be in-tune with the rest of the pack.

Update 6/22/08 - Chris Gibbs has contacted me with corrections to my table. It appears that the figures I had before for the wheelbase were way off, as many have commented. Now with the correct dimensions, it appears that the Haynes Roadster isn't as big as the discussion forums would have suggested. This makes me feel much better about using the design as a starting point!

Update 4/14/09 - It appears the Haynes Roadster wheelbase figures are in dispute again. I've received word from a reader who very adamantly states that the wheelbase is actually 94". The reader states this is what he got in CAD when modeling up the frame. Gibbs himself on his forum states it is 92", so I'll chalk that up to the book not completely representing the actual car.

Two British Lightweights

When I started researching for my locost build, I'd never seen a real Seven in the flesh. As of the beginning of this month, the closest I'd ever come was checking out Andrew's build-in progress. Fortunately, in the last month I've gotten to check out my two favorite cars (and biggest inspirations) in the flesh...er, metal. Both experiences were carried out with huge child-like grins!

First up was an honest-to-goodness Lotus Seven Series II that I caught at the 2008 12 Hours of Sebring. Actually, there were two of them - a racing and street version. These cars are owned by Paul Stinson. He races the high-output version in the SVRA and SCCA. The street car is his golf-cart substitute for commuting around Sebring!

He was kind enough to let me sit in the street version, which reaffirmed my need to lose weight or build a larger chassis. I was able to catch the car on video as it went out for a recon lap of the Sebring infield.



The best photos I took of both Sevens are up on my Flickr site.

The other car is the ultimate evolution of the the light-and-agile Seven. The Ariel Atom is my favorite car. If I won the lottery tomorrow, I'd drive to pick up my check in this bad boy. This particular Atom was parked nonchalantly at the 2008 Georgia Tech Auto Show.

I could have stared at this car for hours, but I was taking care of my daughter and had to look fast (fortunately pictures last longer). There are so many fantastic details, so many awesome welds and crafty bits of carbon fiber! Everything clearly had a lot of thought put into it. Even if my Locost doesn't go as fast as the Atom (which it certainly won't), I hope that I can put as much effort into the design and construction of my car as the folks at Ariel do in theirs. It's really a stunning car.

The Atom at the show was for sale for the cool price of $79k. It's tempting to sell our house and buy it, but since there are no body panels and no roof it wouldn't be very good to sleep in.

Both of these cars capture everything that is good and holy about sports cars. They're light, agile, responsive and provide the right medicine to treat the current pandemic of bloated, overweight and overwrought sports cars. I hope my locost comes close to their awesome example.

Starting to lay stuff out

The time has come to start to put things together with the design of the Spartan. I've reached the point where I've got far too many ideas for the frame and layout and it's becoming difficult to keep them coherent in my head.

I work with CAD every day (Pro/ENGINEER to be specific), so I can get quite a lot done during my lunches at work. Fortunately, the software is flexible enough that I can lay out a tremendous amount of detail before actually having the critical components in hand.

The chassis started as a Gibbs chassis, but I've already made several mods, most notably reducing the length 2". I think the Gibbs design is pretty long, and I'd like to get the wheelbase down to 95"-98". I'll post more about the frame once I get the preliminary design done.

The components are rough models based on pictures of the actual components and a few key dimensions. Already I'm pretty concerned by how big the stock Miata intake manifold is.

For right now, though, this will give me enough information to pick components and place them in the car. I'm hoping that I can do an accurate enough job to reasonably predict the CG of the car and do some tweaking. Eventually I'd like to have a very accurate model of the entire car.

Besides, frame development in CAD is cheap and easy. I have access to FEA software, so I intend to model the "stock" Gibbs chassis and compare it to my evolved frame so I can get an idea if my ideas will work or not.

Atlanta area Locost builders' meetup

Last weekend I met with several Atlanta builders to introduce ourselves and chat about Locost stuff. We all had a great time, and it was nice talking about the car with a group who are as passionate about building a locost as I am.

Additionally, I finally got to sit in a Locost/Lotus/Caterham sized frame (thanks eVox!). My first reaction is that the car is tiny! Unless I give up lateral support in the seats, I think I'm going to have to widen the frame to fit my physique. I'm trying to lose as much weight as possible before starting my build, but even then things are going to be tight.

I'd been resisting building a plus sized frame for some time, but I do think something's got to give. The Gibbs chassis is a +221, meaning it's 2" wider, 2" longer and 1" taller than the earlier Champion design. I think the extra 1" per passenger will make a big difference.

The extra width would also come in handy in the driver's footwell. It's a little tight, especially with my clod-hoppers on. I may have to invest in a pair of driving shoes.

No matter what, sitting in a mostly completed frame underscores the need for some kind of seating buck to simulate the passenger compartment of the finished car. Better to find out I don't fit before I start cutting metal...

Some thoughts on safety

"Do you ride motorcycles because of their proximity to death, or in spite of their proximity to death?"

This was the opening question posed by Matt Chambers, CEO of Confederate Motorcycles, during a recent presentation on American design.

I don't ride motorcycles, but if I did I'd have to answer "in spite". I'm lucky in that I have an abnormally high sense of self-preservation. I usually lift off the throttle well before the limits of my car and I always instinctively slow when rounding a blind corner. That's why I'll probably never be a great racer, and why I pay next to nothing for insurance!

I'm a father and a husband, and I don't particularly want to get killed or maimed for my hobby. Worse, I don't want to take someone out with me. So when a recent discussion with co-workers turned to the subject of the safety of my home-built car, it led me to make a few more decisions on what my car will be about.

I don't expect this car to be as safe as a real car, period. I plan on using 6-point racing harnesses, but I won't have airbags, ABS or even side-impact door beams. If I get t-boned by an Escalade, it'll probably put me in the hospital (or worse). I take my safety seriously, but I also lament the time where cars weren't loaded down with 1000 lbs. of safety features. I'm starting to get fanatical about weight, and a line has to be drawn between safety and the purpose of the car.

That being said, the primary approach I'm taking with regards to the safety of the vehicle is to prevent a loss of control of the vehicle or dangerous vehicle dynamics while on the road. I'll have to practice "active safety" (aka paying attention and driving defensively) with regards to threats from other vehicles on the road.

To me, loss of control usually falls into 3 areas: structural failure, loss of brakes, and loss of steering. There's also the terrible threat of a fire.

Chassis/Structure

Carroll Smiths "Prepare to Win" is an awesome book, and I think all builders should read it. It outlines his fanatical attention to car preparation to minimize mechanical failures. I won't go over all the details covered, but here are a few "high points" I'll focus on during the design and build:

• Use aircraft grade hardware to secure anything that'll hose you if it fails. Lock washers, nylock nuts and loctite just don't cut it.
  
• Safety wire or cotter pin all hardware that may vibrate loose.
  
• Redesign stress points (like suspension mounts) to maximize weld area and to prevent loading welds in tension. This is a major issue (to me) with the current Locost design.

Additionally, I'm planning on integrating the roll-bar into the frame (like Moti did on the LocostUSA forums). I'm not really impressed with the way the roll bar mounts on the current Locost design.

Finally, I just need to pay attention when designing and building the suspension. I don't plan on cutting corners with the structural integrity of the suspension bits and mounting points.

Brakes

Mark Rivera's crash at Mid-Ohio really opened my eyes to what could happen in my car. In his case, a fastener worked free on his brake pedal and he lost brake control.

Thankfully again he was on a track with enough run-off to contain the accident. My worry is that my car will careen out of control on the street. I've made a few decisions regarding the brake system.

• I'm going to use a commercial pedal set w/dual cylinders. I don't want to make my own when so many proven systems are out there.
  
• I intend to run brake lines away from heat and sources of puncture. The brake lines to the rear will have to run past the driveshaft, so I'll have to think of a way to protect them.
• I'm going to run hanging pedals, if possible. As one commenter on the LocostUSA forums pointed out, hanging pedals are less vulnerable to debris clogging the works.
  

Steering

There have been many posts on the forums concerning steering rack modifications to reduce bump steer. I get the willies when I think about welding my steering rack. Especially because once welded and reinstalled, there's almost no way to quickly inspect the welded area over the life of the car. If at all possible, I'd like a professional solution, either an off-the-shelf rack or something modified by a pro.

I'm considering using a removable steering wheel, but I need to do some research regarding the safety of these on the street.

Fire

This really scares me, and it should scare everyone else, too. It's going to be friggin expensive, but I want to use a real fuel cell for my car. I intend to mount the cell in the rear above the differential to give as much crumple room as possible in the event of a rear impact.

I'm going to have a fire extinguisher in the passenger compartment and battery cutoffs on the dash. I intend to run fuel lines in the same "protected" zone as the brake lines.

In closing, safety isn't just a punch list of features, it's a design approach. As I design and build this car I'm just going to have to be diligent about building something fun and light, but not dangerous.

Wheel and Tire Selection

Several sources I've read (the Kimini book, Competition Car Suspension by Allan Staniforth and others) recommend choosing tire sizes before ever embarking on suspension and chassis design. This makes sense, since nearly every book I've read so far starts out by stressing the critical role the tire plays in making a car go, stop and everything in between.

Tire Diameter

Since I've already decided on using the Miata as a donor vehicle, deciding on an overall wheel diameter is somewhat straightforward. The original NA Miata (1990-1997) was shod with 185/60R14 rubber, giving a wheel diameter of 22.74".

I'm going to add two additional requirements: I want to keep all 4 wheels the same, and I want to keep to relatively common sizes. These need to be in place for the simple reason that I don't want to have to spend a ton on odd tires or risk not having them available in the future. If I need larger rears that's something I'll have to address later.

So with a tire diameter set and a few requirements in place, I can start "shopping" for new shoes. My biggest priority for selecting wheels and tires is low weight (to reduce unsprung mass and rotational inertia). But at the same time I'd like to spec a wheel size that allows for reasonably short sidewalls and crisp handling.

Wheel Diameter

A stock Miata rides on tiny 14x6" wheels (45mm offset, approx. 11 lbs.). As has been mentioned many times, ther are not a lot of good wheel or tire options at this size, which is why most replace these little "daisies" with 15" wheels...which is exactly what the previous owner of my current Miata did. They replaced the stock wheels with the lightweight 15x6" wheels (40mm offset, approx. 13 lbs.) from an NB (1999-2004) Sport model.

Despite a relatively heated conversation on the LocostUSA forum, I've elected to stick to the Miata-plus-one 15" wheel diameter. While some may argue that 15" wheels are on their way out, I have faith that NA and NB Miatas will be in vogue for quite some time. Also, Spec Miata racing and autocrossing should ensure a long-lasting supply of tires for road and track.

Besides, that's what the front and rear uprights were designed for. Here's a great reference for stock and aftermarket Miata wheel sizes, offsets and weights.

Tire Width and Aspect Ratio

So given a wheel and tire diameter, it's time to pick rubber. Here's where things get broader. My current Miata rides on 195/50R15 tires (22.67" diameter). Staying in the ballpark of that size gives me 3 larger options. Here's the tire diameter calculator I used to get these figures.

There seems to be many more options at 205/50R15 than with my 195s, so I think that that's the best fit for my build. This gives me a tire diameter of 23.07" (+ 0.33").

Wheel Style

As far as the actual rims themselves are concerned, I've always loved the DTM look (image from the NY Times). I'd love to get a set of O.Z. Supertourismo WRC wheels (in white), but they're expensive and friggin 19 pounds!

I want to keep my wheels to less than 13 lbs (the weight of the upgraded 15" rims on my Miata). I also think that white painted wheels would really look awesome with my paint scheme. White rims will show every spec of brake dust and road grime, but I won't be driving my locost as much as my daily driver and it'll give me a lot of motivation to keep it clean!

These Kazera KZ-M 15x7" wheels (30mm offset) look awesome, come in white and weigh only 12.5 lbs. As an additional bonus, they were designed specifically for Spec Miata racing so they bolt right onto Miata hubs without any adapters. Finally, they're recommended by Flyin Miata which is all the validation I need. Did I mention they're also cheap?

Seems like a no-brainer. I just hope they aren't discontinued before I get around to needing them!

In Conclusion...

Whew. So long story short (too late), I'm looking to get a set of Kazera KZ-M 15x7" wheels shod with 205/50R15 rubber.

An essential addition to your library

Getting your locost library started is pretty easy. There are only three or four books necessary to a basic reference library. But which book should you get next? Without a doubt, you should get Kimini: How to design and build a mid-engine sports car - from scratch by Kurt Bilinski. In fact, I'm starting to think you should get it first.

At first, the Kimini doesn't seem at all like a locost. But despite it's more passive-aggressive styling, the car was designed, built and refined in the same manner as any other serious homebuilt. Kurt is fond of saying that this book is not a "cookie-cutter" set of plans on how to build, but instead is a detailed account of the process of building a car at home.

When I started looking into building a locost I was initially attracted to the "baseline" design. Heck, the car was done as far as I was concerned. As I've read more, I've found that the art and science of building a car at home is less about black magic and voodoo and more about carefully and purposefully thinking things through.

Reading about the Kimini build, I'm emboldened even more to research, analyze and detail every aspect of the car (within some kind of reason). After finishing the book, I started pouring through the standard locost books looking for the same level of engineering and design methodology as Kurt had put into his project. I didn't find it, and now I feel that there may be more left to improve in the design than I'd first thought.

Don't get me wrong. The Kimini book outlines years of research, development and building. Locost books make construction look easy enough to do. The Kimini book is much more realistic and transparent. If you still want to build a car after reading about Kurt's 10 year build, this is the hobby for you!

So I intend to roughly follow the design sequence Kurt laid out early on in his book. You can get a rough sense of the process from the table of contents. I'm sure there will be tons of references to his work in this blog in the years to come.

Buy this book. It's a good deal at twice the price.

And if you just want to cheat and skip the whole process, Kurt's Kimini is for sale...