I Made A Billet Aluminum Two-Stroke Engine

Today we are going to build a two-stroke engine. So step one is to deal with the whole rotating assembly first. The small stuff like the crank pin and both of the webbings I was able to knock out pretty easily. The whole process was fairly straightforward and same thing for the flywheel as well. For that I just picked up this big four-inch puck of steel which I turned down in the lathe. Moving on to the connecting rod, I started by boring a couple of holes into this half-inch steel bar, both of which are going to be offset from each other by exactly 95 millimeters. And technically I didn't actually have to make it this long. While shorter connecting rods might excel at producing a little bit more low-end torque, a longer connecting rod is going to help reduce the side-loading forces that act on the piston, which I'm hoping is going to help reduce a lot of this scuffing that shows up on the skirt. Still, in spite of its overall simplicity though, I did happen to overlook just one thing. I need to find a way to cut a radius into the ends of the rod, because it's not like it's going to be as simple as just throwing it into the mill. You need to be using some kind of a rotary fixture to be able to spin the whole thing around. And as somebody without the luxury of owning one, that's much easier said than done. But what if I don't need one? After all, if I just stick this collet block straight up inside the milling vise, it's basically the same thing. Well, kind of. But honestly, with nothing more than just a pair of these vise grips, it really seems like it's doing the trick. Even if it's not exactly the safest way of doing this. And yeah, I probably could have gotten away by just carefully grinding it down on a belt sander. But why don't I let the results of our little experiment speak for itself? Oh yeah, that's... that's not bad. And I have all my fingers, so that's cool. Although, I still think that going back and modifying the design might have just been a little bit easier. Especially with Onshape, the sponsor of today's video. Onshape is a leading cloud-native CAD and PDM platform, and over the last six years, it's been my favorite. Because Onshape runs entirely within your browser, it gives you the freedom to start projects from your desktop at home, and then pick them back up again from pretty much anywhere else. And with all the heavy lifting being done over on their end, Onshape works effortlessly on all your other devices. So for the Linux users watching, you know who you are. Onshape makes it incredibly easy for you to access their wide range of powerful tools for rendering, simulation, and CAM, without ever needing to leave the site. And thanks to its massive community of users, not only can you browse from a wide variety of public documents, but you can also make the most of your experience with custom feature scripts. 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Tapered fitments are great because they're not only an easy way to keep a part centered, but because they can generate a lot of friction, they're also really good at transmitting a lot of torque. This is actually how a lot of machine tooling works. But of course, for it to work really well though, first I'm going to have to put some threads on the end of the shaft. And let me tell you, manually threading something this big is pretty annoying. The hardest part is actually just getting it started in the first place. The problem I kept having was the die wouldn't fully engage, so it kind of just tore up the end of the shaft. I think it goes without saying this would have been much easier to do on the lathe. However, I don't currently have the tools to do so, and even if I did, I also don't even know if this machine will cut metric threads. I've never actually tried. So instead, I just had to mess around with it some more until I could finally get it to start cutting some threads. It's not as bad as I thought it would be. Yeah, that'll do nicely. And despite what I said earlier about the whole friction thing, I am still going to be wedging one of these pins in between the two of them anyways. Personally, I've got a bit of a vendetta against flywheels, so it's probably in my best interest to make sure that it actually stays where it's supposed to. But with all that sorted, now we can actually start putting this whole thing together. Now, it's not unusual for a small engine to use a press-fit crankshaft. It's actually pretty common. But judging by just how easily this slides together, I'm going to assume that friction probably won't be good enough. But thankfully, that's nothing a bit of welding can't fix. Now, I'm not a very good welder. You don't need to remind me. But a couple of these tack welds should be strong enough to make sure this whole thing stays together. The only thing that I'm not going to weld, however, is the other side of the crankshaft. If I welded the entire thing together, then it would mean that I wouldn't have any easy access to the rod bushing in case I ever had to replace it. And if this project goes anything like it did last time, I will need to replace it. So I think what I'll do is just make a hole between both the crank pin and the other webbing. And then I'll just shove another one of these pins through it so that it locks the entire thing together. Yeah, this is probably never coming apart again. Moving on to the piston, I started by turning down this chunk of aluminum in the lathe until it was down to the right size. I then added these two piston ring grooves up towards what's going to be the top of the piston. Two-stroke pistons will usually have these little pins pushed into the grooves. These are to stop the piston rings from moving around while the engine's running. I did make sure to add these later. I just forgot to record it. Either way, the last step was to head over to the milling machine to both drill and ream the hole for the wrist pin. Reamers are tools which can turn an existing hole into a slightly larger one, which in this case would be exactly 12 millimeters. Doing it this way made it really easy to make a wrist pin that can then be pressed in with some mild interference. Press fitting does make it less convenient to have to take apart later, but assuming that I've done everything correctly, hopefully I won't ever have to. Moving on, I wanted to get started on both the crankcase and the cylinder, both of which I'm going to make from these big hunks of aluminum. Now, my plan for the crankcase is to have two halves, which are then going to be bolted together to make the entire block. And while this may seem a little bit more complicated than just a single-piece crankcase, doing it this way will make everything so much easier to assemble later on. As for the cylinder, I started by taking this big block of aluminum, which I then slowly sculpted into a much smaller block. From there, I then needed to make the bore for the sleeve. And instead of just using this boring bar, which I thought would have taken forever, I figured that I'd be able to save a little bit of time with this much sharper end mill instead. Yeah, that's not supposed to look like that. Okay, never mind, I not only broke one of my good end mills, but more annoyingly, I also ended up totally ruining the part that I was already working on. Well... So $70 later, I decided it was easier to just start over with a piece of round stock instead. This way made adding the center bore a whole lot easier, and honestly, I probably should have just done it this way in the first place. As for the sleeve, however, I would normally just use a piece of this steel piping, as in some cases, it can work alright. But this time, I decided that I was going to try going with some cast iron instead. That's really heavy. Cast iron is great because it's not only much harder than steel typically is, but it also even has a little bit of a self-lubricating property. Perfect for the walls of our cylinder. That's... Good. That's good. And once I had finished up with making the cylinder, then there was just one thing left to do. Dude, shut up. That works. Now like I was saying earlier, there's not really a whole lot to these things, so putting it all together was kind of just like building one big LEGO set. 150? That is not bad. For the ignition system, I'm going to be using this 12-volt coil pack and a set of these breakers. And to be sure that the spark will happen at the right time, the entire bracket itself can be rotated either forwards or backwards, depending on what you need. And because this is a two-stroke engine after all, it means that we'll need to make it a special fuel cocktail to sip on so it doesn't blow itself up. If you're wondering how much oil I used, I honestly don't remember. I kind of just guessed. Ooh, that's a lot of oil. Probably a little bit more than I should have, judging by how these projects have gone in the past. Yeah, that's what good oil looks like. I figured that it wouldn't hurt to try to be safe rather than being sorry. Oh my god. That was really scary. And if it wasn't already obvious, things don't usually go this well for me. So seeing this thing fire up on the very first try was honestly kind of a surprise. Has anybody seen where my socket went? That is really loud. That is very loud. At the risk of potentially going deaf, as well as the carbon monoxide poisoning that goes along with it, I decided it was probably better if I just moved everything outside. And now that I've actually had the chance to let it run for a few minutes, honestly, I think this is the best thing I have ever made. Especially considering that some of my projects don't really work in the first place, and when they do, it's usually not for very long. With that said, however, when I took a look at the slow-mo footage, I did notice that the flywheel kind of wobbles around a little bit. Although I don't think this is the fault of the flywheel or the shaft that it sits on. I think this might have more to do with those threads that I cut earlier. Either way, it doesn't really seem to be hurting anything, so I'm probably just gonna leave it. I'm not really too sure what I'm gonna do with this thing just yet. I know that it would benefit from some tuning, as well as getting an actual exhaust. But if you have any more ideas, let me know in the comments. I'm sure that I could use this thing for something. Otherwise, if you want to see me make more things like this, then subscribe, and I will do that.