I decided there was too much play between the axle halfshafts and the differential extensions, so I made collars with the precise inner diameter and length necessary to remove all play. I was pleased that I could make them so precisely, even on my old beat-up lathe, that they made an almost airtight seal. I’m showing many of the steps below as a reminder of just how many operations go into making even the simplest-looking parts.
Here’s a big project that spread out over a number of months. I’m aggregated the photos here and attempted to make them tell a coherent story.
The cluster as a whole can be adjusted forward and back for drivers of different heights. The gas pedal is adjustable for foot travel, throttle cable travel and left/right position. The brake pedal height is independently adjustable, and brake bias is adjustable from front to back. The hydraulic clutch pedal is also independently adjustable for height.
Many of the original pieces were laser cut from steel, then bent and welded to form the complex shapes required. Some of the bushings were CNC turned, but most were made by hand. The master cylinders, brake bias adjustment cable, and the nuts and bolts were purchased, with everything else custom made. This includes the brake bias adjustment assembly, which forced me to learn how to cut threads on the lathe. It’s not as easy as it looks. Take a look at the brake bias adjustment bar– it has three sets of threads independently cut on a manual lathe, three diameters, two snap rings and a threaded hole. Good fun! Due to changes in the steering rack mount, the main pedal bracket had to be widened as you can see in the photos.
I looked through a bunch of street car transmission shifter cables, brought a couple of them back to the lab, and decided on one that was the correct length, light, and low friction. Everything else was fabricated…
The car will use a Suzuki GSX-R1000 engine, which has a 6-speed sequential transmission, meaning the shifter only has two movements: shift up, and shift down.
The car will use standard Honda Civic axle halfshafts, and I had the choice of cutting, sleeving and re-welding them, or building extenders that effectively widen the differential to meet the unmodified halfshafts. The cut/sleeve/re-weld option would eliminate the axle hardening and leave unknown strength, and I’ve since seen an example where this was done and the axle broke right at the weld. The option of “widening” the differential has several advantages. First, we can easily replace the halfshafts if necessary in the future with off-the-shelf parts. Second, moving the inner constant-velocity joint closer to the plane of the control-arm pickup points minimizes the plunge, or change in length, required as the suspension moves through its travel. Third, the halfshafts become equal length, eliminating torque steer. Now you may say “but, the extensions will be of different length and will twist unevenly so the torque steer won’t be eliminated”. The extensions will be much stiffer than the axle shafts so that won’t be the case.
So the choice was clear. We started with a differential and a couple of halfshafts as raw material…
Thirty-four years ago I designed a car for the SAE collegiate Mini-Baja competition. The differential was inadequately supported in the middle, and although it didn’t break on us, it broke the next year and sidelined the car. I’ve felt guilty ever since, so that’s one mistake I’m determined not to repeat. This one should be adequate…
Later I plan on fabricating some sort of container or plugs to keep the oil in the diff.
My original plan was to make the engine install from the bottom as I’d owned Porsche 911s for most of my life, but feedback on the ApexSpeed.com forum made me change my mind. The change was fairly simple, requiring only making the upper right engine-compartment frame rail removable. Taking an angle grinder to cut a big chunk out of my finished frame definitely made me measure seven times, cut once.
Sorry for the long delay since the last blog entry. A lot of water has gone under the bridge since then. But don’t worry, the project has continued, although with some big distractions. I’ll be trying to catch up on my blogging in the next few weeks.
Next up is fabricating the engine mounts for the 2007-8 Suzuki GSX-R1000 motorcycle engine. I surveyed the state of amateur formula-car engine mounts, and decided a lot of them are inadequate. This video got me to thinking: https://www.youtube.com/watch?v=m1j7hmJmSJA as my car should be faster than a Ferrari 458. Some might be skeptical of that speed comparison; if you are, take a look at this comparison of a Porsche 911 Turbo versus a formula 4 car: https://www.youtube.com/watch?v=e8WyvVbVu4k . A formula 1000 car should compare favorably with a formula 4 car. Either way, you lose a lot of torsional rigidity with the large open hole to mount the engine, and I hope to recover much of that with a strong triangulated set of engine mounts.
I need to be able to lift the engine into the chassis, but due to the lowered floor of the work area a standard engine lift won’t work. While I’m at it, it would be nice to be able to lift the entire assembled car off the build table, turn it ninety degrees, move it to the door, and roll it out of the shop. Below is the solution. Sorry there aren’t any plans. The build process was “go to your local metal recycling center, buy some scrap beams, clean them up, cut them as necessary, and weld them together”. I’m getting more comfortable with winging it in the machine shop.
Also shown below is a mount I built to mount an angle grinder on the lathe. Parting-off has always been a problem. I’m just about to make the engine mounts, requiring at least 36 cutoff operations, and I figured I’d better solve the problem. I have a cutoff tool but only purchased a small number of carbide inserts; the inserts wear out really fast and I either have to order more from the US or drive at least an hour to a store that MIGHT have them. This baby works great, giving a clean straight cut. Just have to be careful not to let the abrasive get into the lathe.
Next up: mount the steering column in the chassis. Nothing magical here, just lots of little steps. The steel bearing cup insert did work well at preventing distortion during welding. To get a proper press fit for the rear support bearing I decided to use my new internal bore gauge. At first it didn’t work at all (made in China, of course), so I had to disassemble it completely, figure out how it was supposed to work, unstick the rusted shaft, replace the dead battery, and reassemble it. All in a day’s work out here on the frontier. So now I can measure both holes and shafts to a few microns and press fits are much easier to make.
I originally sent all these parts out to the CNC shop, but they never got back to me with a quote so I ended up making everything myself. The spline onto the steering rack was a tight press fit, so for now the entire column including the rack is a single assembly. I don’t know it’s possible to remove the rack later, and I’m not going to try as it might destroy the rack. The U-joints are special units from Sweet Manufacturing in the US, but don’t seem to be anything special. In the future I might try to adapt standard Honda steering column U-joints and column splines. These use a perpendicular pinch bolt so the column can be disassembled at each joint.