This is the second part of my LS3 Engine 3D Print Project. You can read Part One here »
Initial Engine Assembly
Assembling the printed parts to form the final engine was a long process. It involved a lot of sanding, threading and fastening. As mentioned in Part 1, the parts were designed to have pre-built fastening points for screws, as well as clearance holes that allow smooth movement for pins and valves. Most of the fastening holes had to be threaded, however I noticed that even if I twisted a bolt in an un-threaded hole, the bolt would sink in and lock.
The final assembly required the use of M3 socket head cap screws of almost every length (from 3mm to 50mm), nuts, bearings, set screws, and a lot more. The full hardware list can be seen here:
Assembling Small to Large Components
I started with assembling the smaller components first. This way, if something were to go wrong, I could quickly re-print parts. I began with assembling the pistons, but I had to widen the holes on the side of the piston heads so they could move freely.
The crankshaft assembly was a lot easier than I had originally thought. Eric’s original designs included timing markers for each component of the crankshaft. All I had to do was follow the part sequence and align the markers. Everything was secured in place with hex screws and nuts.
The same process was implemented for the camshaft assembly as well. I stacked the camshaft together in sections, making sure everything was lined up with the timing markers before securing the end. The camshaft was a little tougher to assemble than the crankshaft because everything had to be stacked together on a 175mm threaded rod.
Full Piston and Camshaft Assembly
Once the crankshaft, camshaft, and pistons were assembled, I decided to then install them in the engine block. The remaining moving parts of the project are dependant on these two assemblies being installed. The crankshaft was easy to put in. I flipped the block over, placed the crankshaft in the pre-built grooves, and locked everything up by screwing in the bearing caps.
After attaching all the pistons to the crankshaft, I did some initial rotation tests to see if everything was aligned properly. There was a little bit of resistance I felt from the friction between the plastic, but after a few spins I started to notice it decrease. The pistons slid smoothly and were able to rotate freely without any resistance.
I had a lot of trouble with installing the crankshaft, because it didn’t slide through its channel as nicely as I would’ve liked. The bearings were a little bigger than the width of the channel, but after some sanding I was able to tamp the camshaft through the holes with a mallet. When the camshaft was in place, I synced it with the crankshaft using a 2GT-200 timing belt and the timing markers that were on the end parts.
Tips n’ Tricks for fastening 3D printed parts
Fastening 3D printed parts is always an interesting task. The general rule is to tap and thread any holes before fastening with screws, and that still holds true with plastics and 3D prints. I threaded almost every fastening hole for this project, but there were a few occasions where I didn’t need to. One of those occasions was inserting the bearing caps for the crankshaft. The caps fit so snug inside the grooves of the block that I didn’t even have to screw them in. Since the layers were parallel to each other, the friction between them provided enough force to hold the caps in place. The screws just added another level of resistance.
Fastening without threads works really for smaller parts that don’t hold a significant amount of weight. Of course, parts must be designed with included fastening holes. Don’t apply too much force when twisting screws into the holes, as the threads on the screw will start to chew away at the plastic. Instead, twist the screw in until it gives a little resistance, then gently apply a little more force to make sure it doesn’t move. This way the threads will sit inside the new grooves nicely.
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The rest of the assembly process will be covered in Part 3, which will be published soon. Subscribe to our blog to stay informed on this project.