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Fantastic! What exactly is your spark ignition / distributer system comprised of?

I initially assumed the piston ran inside a ported liner & the pockets were relieved in a separate outer cylinder so the piston was always running on the straight liner or port webs like a regular 2S. But it looks like you are counting on the lower pink part for accurate centering during when...

That's very cool. Can you show a front view section of the rod assembly? I have conventional radial master rod / link rod assembly on the brain & cant visualize how the pistons are making the equivalent TDC BDC motion with cylinders rotating around.

There are scads of YouTube videos regarding 'ambient pour or mild vacuum draw' silicones for molds & part replication ranging from formulators like Smooth-On, to hobbyists to professionals. I had to Google 'LSR' - guessing that is relatively high end fabrication process you are involved with?

More what I'm wondering about is the gas flow through diffuser. Is it entering through the lower (yellow shade) array of holes, into the pie chambers & then flung out to the induction tubes? What does the (pink shade) opening do?

Not related to your build, but in my daily YouTube grazing, came upon this converted motor / brake adapted to a (commercial) model engine.

Is been a long time since I looked at these plans. It just re-occurred to me the carb is front-ish on the nose case. So presumably the mist charge can lubricate cam gear train, back through bottom rod assembly, through that the rotating vane diffuser/booster? part up to the heads. But I can't...

Fantastic Ray, way to go!

Nice, Ray. What kind of ignition module are you using to drive through the distributer?

We might be saying the same thing with different words and/or I am perhaps not explaining myself properly. I'll try again. My cam timing spreadsheet has numerical values in the background, but for I'll try to just demonstrate graphically. As we all agree, start with a single cylinder 4S. Here...

Maybe its an optical illusion of Brian's cam picture taken at an angle, but I am having a tough time understanding the timing. Just as a comparison, the horizontal opposed 2-cyl Boxer I'm working has a 4-lobe camshaft, 1 per lifter. I think boxer configuration means both left & right pistons...

Guessing this is the website you are referring to & even a nice little animation. I've had their website saved in my Favorites but have yet to try one. Something tells me from an inquiry a long time ago they were $$ but that may be a function of where I'm located. Peter, what alloy of lapping...

I was going to suggest an RC hobby store. For sure they would have steel 2-56 fasteners & threaded rod but I'm less confident about brass. They are not difficult to make in the lathe with a die & then you have control of other features if necessary. I made M3 pushrod adjusters from O1 for my...

What do you use for honing tools in this diameter range?

Coming along nice! So the two round crankshaft elements come together on a common crankpin for the 3 rods, is that the layout? Is the mate a permanent press fit thing or is there a retainer method whereby you could later disassemble? Do you put some kind of shim washer between the rods faces or...

Did you select this particular print house (over other online shops) more for what you deemed to be their technical expertise, end product quality, prior experience etc.? Or maybe it was more driven by home proximity / timing / cost...? Is there a batch cost advantage to filling up a specific...

@Bazzer is that angled print orientation in post#34 picture something that the 3DP software sets up for its own optimization? What engine displacement sizes are we looking at just for layout scaling?

They might vary by supplier but verbiage I was provided on the unit shown in post #5 said 500 rpm minimum for either the 3000 or 6000 max RPM unit. I have not pulled the trigger so I cannot corroborate. Specs seem to be a bit iffy depending on seller. Some may say 0-3000, or 500-3000 or just 3000...

Was the bearing threading required for assembly somehow or in order to more easily replace it on day?

Also, your crankshaft caught my eye. The counterweight cutouts look the same on both ends, but the right one is thicker. Obviously for a reason. Can you elaborate?