Preface: I figured I’d write a little blurb about my project to get my build log going. The plan was to write while my daughter took a nap. She took a longer nap than usual so this ended up longer than I really wanted. The upshot is if all goes according to plan (never happens) you should be able to read this post, assume I’ll finish it and go on with your life.
Little background on me first. I posted up in the introduction thread but Chet seems to be the only veteran that hangs out there. I’m a car guy, background is fabrication and engine building. Schooled as a Mechanical Engineer but dropped out of college three years in (with honors) when my European Performance shop was taking off without me. Ran the shop for five years and closed up one day when I was offered my dream job as an automotive consultant on the second largest racing game in the world. These days I only try to work on cars for fun since the five years of doing it for a living nearly killed my passion. My daily is an E36 M3, the baby hauler is an E34 525i Touring with an LS1 swapped in (no kit, 100% my work) and my beautiful, loving Wife has a spotless ’82 Rabbit S.
Clickable thumbnails of the LS1 BMW Wagon
On to the car.
I've wanted to build a Locost for years and as soon as I finished my last project I began planning for my very own little sports car. Planning started with a McSorley +4, Rorty IRS and SR20/S13 donor but quickly evolved into a more Caterham-ish design and virtually everything else changed too. Figuring Caterham has been perfecting the 7 since '73 I took a few cues from the current De Dion chassis and started designing. The rear is, of course, De Dion. Not many people seem to build them this way but I just love the way they handle. The joint between the lower A-Frame and the De Dion tube defines roll center and allows me some KRC placement adjustment. The upper links define the rear steer affect and are adjustable. It's the way Papa Chapman built the S2/3 and the way Caterham builds them today.
All chassis bracing omitted from model for clarity:
Up front I've added a kickup to the chassis and the lower control arms mount to the end of the chassis rails which allows me to extend the lower arms slightly and dispose the awkward book designed nose. I plan on running inboard front shocks and have the capability to map wheel rate through travel so it won’t be so much of a guess/check/rebuild issue. More of a define wheel rate curve/move points until it matches/build it once situation.
Other than that and a couple other changes (Lotus based rear structure, dropped N1/2 for arm clearance and some well placed round tubes) it's largely based on book/McSorley dimensions. I added 4" to the cockpit width to fit my race seats and 2" to the height from the scuttle fwd. I also added 2" of length just to the engine bay to ensure there's proper engine room and some symmetry. I’m tacking everything up with the MIG for right now and final welding will be done with the TIG.
The drive train is quite the mish-mash. I'd originally planned on a naturally aspirated SR20 but found them difficult to acquire stateside. Turbo motors are plentiful but the N/A versions aren’t. When we had a BBQ last week with some car friends the game was ‘best engine combination for a Locost’. Suggestions ranged from “HAHA… no” (Ford V8-60 and Cammer) to “Quick, get on the internet and figure out how to make it RWD”. I honestly thought no one would come up with a better idea than the SR until my buddy said ‘Hey, what about a Quad 4?’ Well what about one… they come in 150, 180 and 190hp flavors stock, two companies offer bellhousings to bolt them to a T5, they’re cheap-as-free, can be modded over 260hp N/A for peanuts and they only weigh 300lbs once you’ve removed all the stuff I don’t care about. That was it; decision made. Quad 4 on DCOE side drafts.
I still plan on using the S13 240sx diff, axles and hubs since the design mimics the Sierra with separate outboard hub flanges (plus you can get a OBX helical/torsen differential for under $400), T5 from either a Mustang or a Camaro, Manta or Q4R bellhousing and a neat little Quad 4. As luck would have it Quad 4s were the hot motor in SCCA Sports Racer C for a while and now they’re not… but they’re not old enough to be vintage so the ex-race parts are cheap. Last week I picked up brand new a 7.25” 7lb QuarterMaster racing flywheel for $99 ($600 retail). It uses a 7.25” twin disc clutch which, thanks to the used Nascar parts on ebay, is also dirt cheap. The next day I bought a $4000 set of GM Performance / Crower Titanium connecting rods for a scant $500. A quick chat with an autocross friend went a little like this, ‘You’re using a Quad 4 eh? If you need any parts let me know, I have two complete engines sitting here, pistons, cams, a dry sump… come on over and rummage.’ If deals keep coming up this often I’ll have all the parts to build a killer Quad 4 and no money for the rest of the car. It’s a ‘Locost’ with Ti rods… right.
A little short on space. I pull the cars out when I’m working.
2hr/day for a week and I have this. At this point I’m measuring hood clearance with a set scuttle and nose height.
Until next time…