After our previous failed attempt, we were determined to make it work this time. We bolted the crankcase cover on to provide more structural support for the block and heated it to 250 F. With the sleeve in the dry ice again, we set up a smaller hydraulic press with a more controlled pressing capability than the hand press. To our surprise, the sleeve actually slipped right into the cylinder without pressing. Luckily the relief chamfers lined up with the connecting rod path and that was it, the sleeve was in the cylinder. As they always say, third time's a charm.
Once the sleeve was in, we drilled and tapped holes to match the bolt pattern of the Honda OHC head. Dan pressed the lower timing gear on the crankshaft and a timing shaft extension on the camshaft. With the timing chain tensioner in place, we were one step closer to getting the engine running. Next on the list: intake and exhaust systems.

Unmodified 3.5HP Briggs and Stratton block

Modified B&S block with cast iron sleeve

Sleeve with silicon putty on the piston to check for valve clearance

Honda head mounted to B&S block with external timing gears and chain tensioner

Just a quick video of us pushing the car around the shop floor at Central Roller.

Dan machined a sleeve out of a 4" cast iron stock and cut two relief chamfers on the inside diameter on the lower end for connecting rod clearance. Then we put the sleeve in dry ice to shrink it for an easier press fit. When we tried it on the hand press, we placed the sleeve on top of the cylinder and starting cranking, but there was one major problem: the sleeve wall did not line up perfectly with the cylinder wall. Result: the block began to flex and a wall of the crank case actually shattered.

Cast iron stock

Machined sleeve with relief chamfer

Sleeve dropped halfway into cylinder, broken crankcase wall

With the prototype frame fully rolling with brakes and all, I was able to go ahead and start framing up the body. Back in December I ordered 60ft of 0.5" OD steel tubing with 0.035" thick wall (very light stuff), that I planned to use as the space frame for the body. The next question was what to cover it with. After debating fiberglass, balsa, and remote control aircraft covering, I ended up deciding to try out PVC boat shrink wrap. I went to Hern Marine in Fairfield and discussed the project with them, and ended up leaving with plenty of shrink wrap to experiment with in three colors! Thanks to the guys at Hern for their support.

We didn't waste any time experimenting with the shrink wrap on the prototype frame. The first thing we did just to try it out was boxing in the front sides of the frame. Some tape around the edges, some patience with the heat gun, and the result was a drum tight, smooth surface!

Taping a piece on the side

Hitting it with the heat

After Shrinking

Feeling confident from the first try, we covered the other side. But we didn't stop there. We went ahead and used the small steel tubing to create a rear "lower cage" and then shrink wrapped that. We then formed the rear "upper cage," which is removable.

Checking the canopy with the prototype sides

The rear "upper cage" prior to covering

Covered and ready for shrinking

Rear "lower cage" covered and shrunk

Car with prototype tail put together

Check out the LED taillight

Jason has finished up one set of his new steering bracket configuration (see previous post). Big thanks to FKI logistics for helping us burn these parts out with the laser and using the brake to get the initial bend in for us! Jason had to mill a hole for what we call the "axle shoulder," which ended up being an interesting exercise in finding centers of holes on the mill. Jason also had to bore the axle shoulders for a snug fit with our 20mm aluminum axles from KMX Karts.

Milling for the Axle Shoulder

Boring the Axle Shoulder

With the milling completed, we hand cut small gussets to sit on either side of the brackets and welded the whole assembly together. The next challenge was to cut the old brackets off of the prototype frame and weld in the new downtubes with just a touch of leading caster in them. Jason decided that 2 degrees of leading caster would help the car track true, and so we put together a quick fixture with the tubing notcher to accurately notch each frame tube for the desired caster. Jason then used some aluminum rod which we threaded (one side right hand, the other left hand) for custom tie rods. The whole assembly looks and works great.

Cutting off the old steering brackets

Notching for the Kinpin Tube (2 degrees leading caster)

New Kingpin tubes welded with 2 degrees leading caster

The new assembly with custom Tie Rods

We were able to get out and test the two steering systems Jason has been designing: one with a "Pitman Triangle" as we call (like most go-karts and many four-wheelers), and the other using a junior dragster rack and pinion box. We predicted that the triangle would steer much quicker, which is not necessarily what we are looking for when running a 1.6 mile oval track. Stability is key, and the rack and pinion we suspected may give us an edge.

We modified the prototype frame (the tank) so that we could use both systems, and did some light experimentation with the two (the weather was cooperating back then). Rusty, our driver, confirmed our predictions that the rack and pinion steered slower and smoother. Our concern, however, was that it did not steer quickly enough to be able to maneuver through the slalom section of the steering test. A couple trips around the shop floor at Central Roller, however proved it to be enough. An official steering and tip test is soon to follow now that the snow is melting.

The Pitman Triangle setup

The Rack and Pinion setup

No winter coats back then!