Fabricating the Chain Guard

Chain Guard

Finished chain guard in place

Formula 1000 rules require a chain guard equivalent to 1/4″ aluminum to contain the chain in case of a break. I had the blank laser cut, then bent it on my tubing bender. After bending, it was sliced in two parts for easier access to the chain and rear sprocket, drilled and tapped for an overlapping tab, cross-drilled for mounting holes, and installed.

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Foam-Filling the Driver’s Head Surround

Foaming Action

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.

Installing the Fire System

Fire Extinguisher

Fire extinguisher with trigger cable and plumbing

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.

Fabricating the Halfshaft Collars

Finished Collar

Finished halfshaft collar in place.

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.

Completing the Chain Tensioner, Rear Sprocket & Shift Linkage

Rear Sprocket

Rear Sprocket in place

Completing the car is now just one long series of small projects. Three are shown here.

The original chain tensioner design was not able to take up enough slack in the chain. The chain was either too short or too long, no matter how many links I used or where I put the adjustment. I had to come up with a new design with two idler sprockets instead of one, as you can see in this post. The bearings are special ceramic hybrids to handle the extreme chain speeds seen with a GSX-R1000 engine.

I’ve had a rear sprocket on the car for some time, but that was just for fitting. The lightening holes on that sprocket conflicted with the mounting holes required by the differential, so it wouldn’t have been strong enough. Instead, I ordered a blank sprocket from England and machined the correct mounting holes and center hole, then cut it in half on the bandsaw so that it could be mounted or changed without disassembling the whole rear axle and suspension.

I also built an adapter to go from the auto shift linkage to the transmission gear change lever. I bought a Suzuki GSX-R shift link rod from Ebay, cut off the front, and welded it to a threaded rod. The rod threads into a bushing I made that fits inside the eye of the shift linkage. The sleeve of the shift cable must be held securely, so you can see here the bracket that mounts it to the frame rails.

Mounting the ECU

ECU Mount

Finished ECU mount

I was lucky enough to find some 7075-T651 aircraft aluminum plate, still with the Martin Marietta markings on it. Very useful for miscellaneous parts like this ECU mount. That stuff is strong! Almost as hard to bend as steel, but it makes for a very stiff end result. So I just cut this blank out of the aluminum plate, bent it in my hydraulic press, and added lightness using the milling machine. It mounts to the frame with aluminum clamshell mounts purchased on Ebay.

Fabricating the Fuel System

Swirl Pot

Fuel swirl pot view from right rear

The car uses an OEM Suzuki GSX-R1000 fuel pump mounted in an external swirl pot. The swirl pot is fed by another electric fuel pump that draws from the fuel cell, with excess fuel returned to the fuel cell. The swirl pot will generally be full, providing a buffer in case the pickup in the fuel cell temporarily sucks air during hard cornering or braking. The shape of the swirl pot is tall and narrow, with the fuel drawn from the bottom so that the engine should never experience fuel starvation.

The swirl pot was fabricated from 1/4″ thick aluminum plate and tube stock just big enough to fit the OEM fuel pump inside. Welding was done by an outside professional welder. An interesting fact about the Suzuki fuel pump, discovered a bit late, is that the five bolts appear to be evenly spaced but aren’t. One of them is off by a bit, probably so the pump can only be installed in a single orientation. This necessitated welding one of the holes closed and re-drilling it.

The OEM fuel pump has a large appendage for fuel level sensing which clearly won’t fit into a small swirl pot, so I cut it off. it would be nice to have a level sensor in the swirl pot so I can watch fuel starvation and get enough warning to get back to the pits before I run out of fuel, but I haven’t figured a way to do this yet.