Making a Retro V Twin Engine

So welcome back. Now if you're new to the channel I'll give you a quick update on how we got here. So this is a custom 60 degree V-twin 200cc engine. It uses a mixture of scratch built and off the shelf parts. Essentially back in May I designed all of this on Fusion 360 with a few key design criteria. Essentially it needed a three quarter inch output shaft and it needed to fit in a certain form factor. Now from there I made patterns from extruded polystyrene foam. Also if you really enjoyed watching my casting videos check out another fellow Kiwi YouTuber Logan Jackson. I'll leave a link to his channel in the video description but he is doing some pretty cool things casting his own high performance parts. And then lost foam cast the crankcases you see there. Once that was complete it was over to my CNC milling machine. I machined both of the halves, bored holes for dowels and holes for the main bearings, and then machined the cylinder mating faces for gaskets. And then over the last month or two I've finished the conrods, pressed in all of the bushes, and that's what we're going to be talking about today. I'm going to show you machining the rods to accept the bushes and some of the design, on my part, design oversights or maybe it wasn't so bad of a thing but I'll show you that and then how I overcame those. Before we crack on I'd like to say a massive thank you to today's video sponsor JLCCNC. Not only are they supporting the channel but they've provided parts for today's video and this project. So they have a machine shop fully equipped with 3-axis, 4-axis and full 5-axis milling. They also have CNC turning and wire cutting. They make outsourcing extremely cost effective and easy with their user-friendly website. You essentially take your design in a supported format, upload it and then you're given an instant quote where you can pick your surface finish, tolerances, whether you want it to be blasted, anodized, etc. Today's sponsor, they came to the table here and they manufactured these parts for me. All I had to do was upload my part as a step file and I decided to go with some hard black anodizing and sorted out what I wanted to do about shipping and the parts were in my hands within six days. Now it would have taken me more than six days to get my ass into gear to get these machined myself or even cast and machined. So a huge shout out to JLCCNC. What you're looking at now is the master rod. Now there's a reason you haven't seen this is because I didn't make it. I outsourced this. It was fairly well priced but I did pay full price for this item. The reason I'm boring it myself is because precision is expensive and I got them to leave a lot of extra meat on all of the critical dimension. So with that being my final cut I'm actually gonna back this off so when I lift it up it doesn't scratch the bore and I'm also going to unlock these to, well they tighten the gib to stop the machine moving up and down but I've actually been using them to tighten up the the head while I move it down to bore the holes as I was getting an oval hole and I noticed the head was actually a tiny bit of play in the gib and instead of adjusting it for now I just pinched those up and I've locked off the x and there's a y-axis screw under there so I can bore without any backlash. So once I'd finished boring that hole I changed the setup to a larger stubbier boring bar and as you can see it meant I had to offset the boring head a bit less seeing as this head is actually on the larger side for my small milling machine and the more you unbalance the boring head the slower you've got to spin it especially on a small mill where it will induce a lot of vibration which could lead to chatter. So what I do here is I find the center of the hole whether that be with an edge finder, file indicator, coaxial indicator, you name it, pick one, find the center and then slowly adjust the boring head out in small increments until it just scratches the part and then ideally you want it to scratch the part equally the whole way around and then from there you can use that as a good basis for your first cut. Now for all my cuts I am taking 0.1 millimeter radially so that takes 0.2 millimeters off every time or pretty much it takes whatever I adjust on the dial double that comes off of the diameter so if you're not thinking too hard or you're having a bit of a brain fade it probably could catch you out it almost caught me out but good thing I measured a few times. So you can see it's contacting in two places here and on the opposite side so this works twofold I'm checking this is central and adjusting this for my first cut and from there it was time to do an in-process measurement so I should have lifted the boring bar a bit higher but no worries I got a decent enough measurement and then checked this with the micrometer as a lot of people have been harping on about my use of digital calipers and I still double check the measurement with the digital calipers after using the micrometer just to make sure I'm not reading it wrong or having a bit of a brain fart but yet from there it's more cuts and essentially the plan is to measure at least you know two or three cuts from final size especially when you don't want to scrap apart so another key consideration when using a boring bar whether it be in a lathe or a milling machine is minimum depths of cut so I know this bar cuts very well and leaves an amazing finish when taking a 0.1 millimeter cut in steel and aluminium and I use a feed of about 50 millimeters a minute I think it's about 500 rpm so I haven't exactly worked out the exact feed per tooth but it gives an awesome finish so what you want to do with boring bars or carbides in general is minimum widths of cut if you don't take off enough the bars just going to rub the whole way down the hole and it's just going to look horrible so that is another important thing to keep in mind when you're sneaking up on a finished dimension you can't finish on a 0.01 millimeter depth of cut you need to creep up on it with about 0.1 left to remove or that's what I do in my case and then I make sure my final cut is 0.1 millimeters so we're going to have a quick look at how we got on with our dimensions obviously I'm pretty happy with them otherwise I wouldn't have taken this off of the mill so we'll check it with these and we'll double check it with the micrometer just to make sure I'm not reading it retardedly so we're looking at 33.03 and on the mic we're looking at oh my brain one two three point zero three that comes into focus for you on the money so happy with that that gives us a three thou or about 0.75 mil clearance when I put in these bearings this is the link rod goes here so I've already pressed in this bronze bush sits in there like so it's also going to be a bronze bush here and here so the next step is to undo the bottom and then I need to put a small notch in here for the locator on the bearing I might just do this by hand seeing as I don't quite think I'm tooled up to make that happen but as you can see I'm relatively happy with the finish I achieved and those bores I hit the tolerant the exact dimension I needed to so you know midget files to essentially create that light retaining groove for the plain bearing now took a wee while and it was a bit of a muck around but I wasn't exactly tooled up with a flitting saw or slot cutter on my mill and again it's pretty hard to scrap apart when you're doing little scrapes with a file so I decided that was the safest option at this stage the next thing to do was whip out the trusty torque wrench and tighten these up to 150 inch pounds in 20 inch pound increments I think this is the first time I've ever tightened a 12 point bolt and actually needed a 12 point socket and it's kind of funny because it's a quarter inch bolt and my quarter inch drive torque wrench um yeah I've got no 12 point quarter inch drive quarter inch sockets so I had to use a 3 8 12 point with a little extension and another socket to hold that extension aside from all that we did eventually get there and the bolts torqued up nice and snug now this is the moment of truth this will tell me the clearance between the conrod and the crankshaft the crankshaft measures 30.00 millimeters on the big end and the rod measures exactly 30.07 millimeters so that's our just shy of three thou or 0.07 millimeters of clearance we need for proper running well that's the theory anyway we'll see how that goes exactly where we want to be 30.07 so I got a little bit carried away and didn't film making these but they're the bronze bushes they go in here and here I just need to deburr the ends they are a just over a thou or 0.03 millimeter press fit and once they're in they will be reamed to 13 millimeters it was time to press the bushes into the rods so this was done with my vice seeing as it's not a super heavy fit and I also slathered the inside of the rod and the outside of the bush with loctite retaining compound this coupled with a press fit means these bad boys aren't going anywhere so here we have a 13 mil er32 collet pop that in pop it onto my collet chuck and here we have a 13 millimeter high-speed steel machine reamer now a reamer is designed to take holes out to a specific size so that is why I drilled both of the bronze bushings in the lathe at half inch or 12.7 millimeters and then this way this will clean up the hole to 13 millimeters if I did this before pressing them into those bores the holes would have shrunk and then I would have had to do this again anyway and probably had a worse surface finish because of the lighter cut so the clamping setup for the rod was fairly simple a single finger clamp the rod sat on a one two three block and I used a small piece of aluminum as a soft jaw and then the next thing to do was loosen it off while I centered the bush on the reamer and then once it had no discernible movement I would tighten up the clamp on the rod and just assume it was centered and seeing as there was you know 0.3 just over 0.3 millimeters worth of meat to ream out off the diameter um this proved satisfactory and it was good enough way easier than dialing in the with the correct clearance bronze bushes are reamed to size and they are perfect the link rod also much the same absolutely flawless now one of the first lessons in engineering building just making things is measuring twice and cutting once now this came back to bite me as this here is essentially a very expensive paperweight this all went wrong somewhere between making myself one of these test fitting it well not fully assembling with the plastic rod that's where I went wrong this should have been used at well I should have actually just used it properly and fully assembled the engine before making this and this I mean all was not lost there were a couple of options option number one was to make a spacer for the base of the cylinder as these were too long how much too long you may ask 14 millimeters now yeah 14 millimeters is the deck height or the height from the top of the piston to the center of the gudgeon pin somehow when I was doing my cad model I thought I took that into consideration but I didn't so 14 millimeter spacer was option number one or we have option number two as you can see here a new 3d printed rod and now I'm just going to cut to the chase no I decided not to go with making a whole new set of rods and it was far far easier to just use a 14 millimeter spacer so now comes the fun part test fitting everything together and everything went together more or less perfectly so that only leaves us with a few things to do namely shim the crank so it's in the right location cut the cam chain to length make sure everything tensions correctly mount the coils sort out some intake manifolds and some stubby little exhausts and then drill a couple of holes here and there just for oil so I need to drill the conrod on the little ends and one oil gallery in the case and then we are good to go so in the end the 14 mil spacers didn't look too bad