Narrow Angle Vee Engines
by petropixel, published
The reviews are in, and they're unanimous: the car you and your team designed doesn't have enough power! The engine bay isn't long enough to fit an inline engine with more cylinders, or wide enough for a V engine. What to do?
Well, you could just make the engine bay bigger.
You could get more power out of the same engine using forced induction.
Or you could take one of the roads less traveled, and squeeze a few more cylinders into roughly the same space.
This cylinder configuration has only been used by two automakers (Lancia and Volkswagen Group) and recently by one upstart motorcycle company (Horex). The two banks of cylinders are just 11 degrees apart (60 degrees is considered optimal for a V6) and offset just far enough to keep the cylinder bores from overlapping. It's not really that complicated a setup, but I did not understand it as well as I thought I did when I started this project.
The combination of flat-plane crankshaft and narrow vee angle does make these models a bit less interesting to watch than sirmakealot's, when one piston reaches TDC the second one it shares a crank pin with is almost there too.
New alternate crankshafts: a crossplane one from my W engines for the VR6 and a flatplane one with more accurate cylinder pairing for the V4. Rods are now slightly narrower for better clearance.
Pick an engine and a crankshaft type, print all of the parts with high infill. Sand or hone the parts until the pistons slide easily in their bores, rods spin on their crank pins, and the crankshaft actually fits together. Use 3mm filament as wrist pins for the pistons and rods. Slide one pair of piston/rod assemblies onto each crank pin (note that the pistons are not symmetrical, the lower edges of the piston crowns should face the center of the block), then assemble the crankshaft minus the end pins. Glue if necessary. Press one of those end pins into the hand crank, then use pliers to press them into the ends of the crankshaft.
The VR6 in the pictures was scaled down .66 to use 1.8mm filament wrist pins, I wouldn't recommend it unless your printer does tiny things really well. It was a pain.