So, after far more Real Life Drama(tm) than I wanted, I'm able to resume work on my wife's mid engine build.
Most of the design remains the same:
1x1 tubing chassis general "Lotus 7" appearance full cage 15 inch wheels with 195/50-15 tires De Dion rear axle 1-liter Suzuki/Geo FWD engine and driveline inboard rocker arm front suspension rear mounted radiator
Over the last few weeks I've been turning my scribbled sketches into dimensioned scribbled sketches. This involved making decisions on various parts, then purchasing them.
This has, of course, not been without its adventures. I know what the space between the hub flanges is on the donor; to determine the width of the chassis, I needed to know the backspace of the wheels.
An early decision was to use Honda 15x6, 4-on-114.3 steel wheels. In my previous experience, steel wheels often weigh the same or less than the same size of aluminum wheel, a very similar wheel is used on some base Caterhams, and the local U-Pull place wants $6 for a steel wheel.
Except, of course, they didn't actually have any 15" Honda steel wheels. I noticed that some of the Honda aluminum wheels were decent-looking, particularly the "5 thick spoke" style.
Honda being Honda, they have more than a dozen wheel styles, most of them in 4-on-100 instead of 4-on-114.3mm bolt pattern. I wanted to stay with the 114.3 since that's that the Geo hubs use. The local U-Pull wants $14 each for OEM aluminum wheels. Hey, that's cheap enough. Except... they didn't have any of those either. So I hit the local "auto dismantler", who claimed to have a set... nope, it they'd entered the wrong code, all they had were some of the "Ronco Vege-Matic" style. No way am I going to use those. They found some of the proper wheels out of state, for $50 + a charge to remove the tire + shipping, coming to over $80 per wheel. I checked Craigslist and eBay and the usual suspects, but the going rate to my door from anywhere looked like $70-$90 each. Too much for a used wheel, in my opinion.
After a few weeks I punted and started looking at new wheels. I sort of wanted some spun aluminum Center Lines; I've run them before and they're very light. But Center Line doesn't make spun aluminum wheels any more. In fact, almost nobody makes spun aluminum wheels now. Even three-piece wheels aren't very common. On the other hand, cast wheels are way cheaper than they used to be. I wound up with a set of Motegi 15x7s that supposedly weigh 13 pounds each. They cost $95/each to my door. Considerably more than the $6 I started off expecting, but way cheaper than an equivalent wheel was, not that long ago.
Luckily, this ain't my first rodeo, and such things were to be expected...
After iterating around various configurations, I decided to weld up the front uprights from a spindle and sheet metal. It turns out Honda had some neat cartridge bearing hubs that fit on a spindle. Some cars used them on the rear. I picked up a pair for a 2000 Accord for $14 each, then a pair of new brake rotors for the same price. The rotors go between the hub and wheel, so I had get some to find out how thick they were.
The 2011 plan called for using a rear-steer Geo rack and pinion. This evolved into using a VW steering box with a relay rod and idler arm; much easier to deal with bump steer and easy to play with Ackermann. However, the fuel tank had migrated from behind the seats to between the front wheels, and the steering box, fuel tank, and inboard springs and shocks wound up trying to share the same space.
I eventually decided to go for a center-steer GM rack with two idler arms. This isn't quite as demented as it sounds; two short rods from the rack to the idler arms will replace the relay rod. I managed to snag one off eBay delivered to my door for less than the local U-Pull place wants. As an extra bonus, it's the non-variable ratio version.
The rack will sit high on top of the footbox, ahead of the brake and clutch pivots, and over the top of the fuel tank. Since I'm welding the uprights from scratch, the tierods will be in line with the upper control arm pivots to simplify bump steer geometry.
The rack is *just* narrow enough to fit inside a Book chassis. The Jaz fuel tank will fit. The springs and shocks will be offset ahead of the fuel tank. The idler arms will be above the fuel tank and to the sides, so there shouldn't be a problem there.
Various bushings have arrived; I'll be using Spitfire rubber bushings on the upper A-arms, Audi TT lower arm bushings on the lower arms, plus the four link in back. The Audi bushings sound exotic, but most of the VAG cars made in the last quarter century appear to use the same bushing; the "Audi" ones were just the most common and cheapest.
A trailing-arm Beetle upper ball joint is designed to take spring load. I ordered one to measure.
Kinetic uses a particular Moog tierod end as a ball joint. I ordered one of those to use as the bottom ball joint. Jack uses it on top, but it shouldn't make any difference. There won't be any spring load on it.
Camber adjustment will be by screwing the lower ball joint in and out. I'm not making any provision to adjust caster. If there's a problem I'll weld up another set of control arms. Same with the trailing arms in back.
All of the tierod ends are VW Beetle, left and right hand. This left me with 12x1.5mm LH and RH for the tierod ends and 16x1.5mm for the ball joints. Metric jam nuts in those threads were not available locally; some are coming via Amazon.
I had to order three different metric taps, which have arrived.
The lower ball joint is supposed to have a 7 degree taper. Nobody online seemed to agree about what taper the VW bits have. I bought a piece of O-1 drill rod to make a D reamer from. After I measure the tierod ends I'll make a reamer to match.
All suspension joints are ball joints or rubber bushings; no rod ends.
I picked 125#, 10x2.5" front springs to start with. I had to have something to measure and build around; if I need 100 or 150# springs I'll get them later. Compared to what I'm used to, the 125# springs look like they're for a toy. The wire is pencil-sized. Theoretically the rockers will run them at 1:1 with the wheel; the chassis width, front taper, and fuel tank location may require shorter rockers and a less favorable ratio.
Miscellaneous bolts, bits, and bobs have arrived, including a complete MGB triple wiper setup for $45. I won't need that for a long time yet, but the price looked right.
I still need more parts before I can firm up the front end layout, but at least I have some bits to work with now.
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