For the intermediate term I’ll be using a custom-molded seat insert made with readily available (and cheap) two-part urethane foam. I have a kit of the Indy/F1 style foam, but it’s so expensive I’m going to learn what I can from the cheaper seat first. I’ve learned useful things already: on the first pour the bag doubled over or stuck to itself and the foam didn’t make its way to the thigh area, so the first attempt was scrapped. It was also useful, however, in finding out where to slice the foam to get it out of the car easily, and learning how thin the foam will make itself under high pressure areas (zero thickness). So for the second attempt I first lined the entire cockpit with two layers of 10mm energy-absorbing foam before pouring the 2-part foam.
As it expands the foam pushes hard against any constriction, like your body. When it hardens it’s almost too tight to fit back into. Many hours of sanding and cutting are needed to make the fit reasonable and comfortable. As it is, I can’t even get into the seat with my wallet in my pants pocket. At first I couldn’t even breathe in fully with the shoulder harness straps moderately tight.
First attempt was a learning experience as the foam didn’t go into the thigh area
Plastic template for main foam piece
Using a hole saw on the drill press to make anti-submarine strap cutouts
One of two finished main foam pieces
Lots of energy-absorbing padding
Another view of the default foam padding
Pouring bag made from 2 XXL garbage bags taped carefully together for no overlap
Sanitized for your protection
The pour happens very fast
Immediately after the foam pour
Sliced down the middle at an angle for easy removal
One of many test fittings, complete with HANS device
Two-part polyurethane foam expanding to fill the driver’s head surround.
For proper protection in a crash, the driver’s head surround needs to be filled with foam. I placed an aluminum panel where I wanted the bottom of the foam to be, covered everything with plastic sheeting and poured two-part urethane foam into the cavity. The foam generates considerable pressure as it expands and cures, necessitating many iterations of trimming and fitting. I then sat in the car with the HANS device on, followed by many more iterations of trimming and fitting. Once the foam was cut to shape, I covered it in a single layer of fiberglass and epoxy, then painted it.
Aluminum panel to set the bottom of the foam
Ready to fill with foam
Left rear view of expanding foam
Foam sanded and cut to shape
Initial fiberglass covering
Driver test fitting with HANS device
Fiberglassing over the HANS device cutout
HANS device cutout in driver’s head surround
Boffom view of finished head surround with cutout for HANS device
The fire extinguisher sits under the driver’s knees with a single outlet tube that goes up to the left side of the driver’s left knee, where it splits at a T intersection. One tube goes up to the dashboard and crosses over to the right side where it ends in a nozzle to the right of the driver’s right hand. The other tube is routed inside the left of the driver’s compartment, through the firewalls, and ends in a nozzle pointed at the headers. The cable-operated trigger is mounted just to the right of the driver’s right hand. These locations guarantee that when the driver pulls the trigger his hand will not be blocking the driver’s-compartment nozzle.
Fire extinguisher trigger / release with safety pin
Driver’s compatment nozzle
Tubing routed near bottom of left side of cockpit
Fire extinguisher engine-compartment nozzle pointed at headers
I wanted to have a generic surface for mounting various switches and different permutations of gauges and data loggers, so I built a dashboard by shaping it from a flat sheet of aluminum. I thought it would only take a day, but it took a bit longer. Given that this is only my second attempt at metal shaping, the result is surprisingly good and it ways next to nothing. Take a flat sheet of aluminum and start pounding the crap out of it until its the right shape… (I may be oversimplifying a bit here) then weld the corners.
Cutting out the dashboard opening from the cockpit surround
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.
Laser cut parts arrive
Laser cut gas pedal parts before welding
Gas pedal parts clamped for welding. I like clamps.
Clutch pedal clamped for welding
Clutch pedal after welding and grinding
An early trial fitting
Testing fit inside the frame
Widening the main bracket
Finished main bracket
Lots of parts in primer now fitting together
Black epoxy paint
Finished except for brake bias assembly
New Chinese calipers: 2″ = 51.9mm LOLWUT?
Milling part of the brake bias adjustment bar assembly
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.
Components of the shifter
Forward end of shifter cable with fabricated mount
While the sides of the cockpit already have side-intrusion panels on the outside, they will also have a second panel on the inside to prevent the seat foam from extruding between the frame tubes and pushing on the outside panels, something those outside panels aren’t equipped to properly resist. The interior panels also must follow the SCCA rule against stressed skins that requires chassis attachment points to be more than 6 inches apart. Due to their different shape and size, the interior panels have a completely different mounting pattern and can’t share any of the exterior panel mount points. Thus, many more tabs are cut and welded on.
The seat back is formed by the fuel tank and three additional pieces of aluminum, shaped at the sides to provide shoulder support on the front while providing space and access at the back to the fuel pump on one side and the fuel filler on the other. The center section is removable to access the shoulder harness mounting points.
Test fitting the right side cockpit panel, view from inside
Left side clamped in place
Separate mounting tabs for interior panels
Left side mounting tabs welded in place
Left side cockpit panel installed
Test fitting the seatback
Seat back panel had to be cut in 3 pieces; right piece shoulder panel shown
Left shoulder panel provides access to fuel filler
Seat back center panel with shoulder harness cutouts