1/8" Scale 1933 Bugatti 50T Engine in Aluminum
Bugatti automobiles of the 1930s are icons of automotive Art Deco featuring expensive materials, luxury workmanship, and styling reflecting faith in a technological future. Likewise, Bugatti 50T engines were Art Deco industrial sculptures. I admire the sprit of Art Deco, so I modeled that engine replicating most of the visible parts in aluminum, because I've never seen painted plastic duplicate, and keep, the total appearance of the real metal. A Pocher kit's plastic parts, and photos of prototype engines provided data for CNC machining on my Sherline mill and lathe.
The sump took about 60 hours of programing, testing, and milling to shape. There's a lot of aluminum to remove from a 50 x 60 x 200mm billet to arrive at a thin-walled 35 x 46 x 135mm part, and the Sherline removes only about 1.5 - 2.5mm per pass. The rear apron and the external oil lubrication lines were scratch-built because the Pocher kit omitted them. The Engine-turning pattern was applied directly to the sump's surface with a Sherline sensitive drilling attachment as the CNC program positioned the sump below a rotating wire brush. The clutch housing did not lend itself to CNC milling so I used the kit's plastic parts, painted in Testor's silver enamel, a deliberate mismatch with aluminum metal to imply a different foundry. The starter motor received the detailing it deserved. Castle-nuts with cotter pins fasten the motor mounts to the sump. The castle-nuts are from 2.5mm hex nuts precisely cut with a 0.5mm slitting saw blade. The cotter pins are adapted from model ship tiny wire parts.
The eye-catching large inspection plates showcase the "punch" of actual aluminum parts. Notice the simulated square head bolts and washers, available from Model Motorcars (MMC), reinforcing plates and gaskets. Engine-turning was done by CNC on aluminum duct tape, then applied to the part. The tape's aluminum layer is fragile, so, a squared-up machine and a dead flat platen covered with 1/16" sheet rubber are essential.
Modeling the cylinder head took some outsourcing. Sparkplugs, ignition wire, water manifold, and flanges are MMC aftermarket items. Sparkplug wells are cut from conical beadwork trinkets sold in art and hobby stores. Reference photos show that Bugatti's exposed cast iron parts acquire a rusty-brownish-taupe patina, which I emulated with a mix of Testor's brown, rust, and graphite enamels. The ignition wire loom is a taper-turned aluminum rod. Its tiny grommets at the wire exit points are wraps of wire. Some Bugatti distributors were fitted with Scintilla caps displaying firing order enumeration. I modeled this by turning an aluminum distributor body and cap, index-milling depressions for the numbers, and then applying tiny number stickers from a fast-print shop. Also notice the spiral spring latches holding the cap.
The "Y"-shaped front gearbox mates to 13 edges or surfaces, so the three arms' ends were left unmilled to give flexibility for final fitting. The spur gear train was my attempt to improve on the kit's rubber belt camshaft drive, but was unreliable and was removed. I installed only one valve/spring/lifter assembly, the left camshaft, and the three rearmost piston/rings/wristpin/connecting rod assemblies, visible through viewports on the engine's left side. The several access plates and the array of bolts, studs nuts, and washers on the "Y"-shaped front gearbox cover are elements of the engine's robust look.
Intake manifold and over-boost air-box parts were CNC milled. The two stacks have a complicated pattern of outlet ports. This port pattern was drawn at 5:1 scale on grid paper, assigned numerical values, programmed, and CNC milled. An adaptor mates the cube-shaped air-box to the bull-nosed intake manifold. The curvaceous supercharger was unsuitable for CNC milling, so the plastic kit parts, painted with a mix of Testor's silver and aluminum enamels, were used. The aluminum exhaust manifold was manually milled.
Cam covers were CNC milled from 5/8" half rounds. Bosses were cut from 1/16" aluminum tubing press-fitted into precisely located drilled holes in the camshaft gear covers. The hand-scraped design was applied in two opposite 45° CNC controlled passes of the work piece under a spherical burr taking shallow cuts.
The aluminum parts saved painting and touchup time, but required far more time and effort to plan, program, test, and machine, an investment that I feel significantly heightened realism. That was my goal for this challenging and enjoyable eight-month project.