The next job was to remove some metal from the inside of the sump and the block to provide clearance for the con rods.

Here is the block, ready to be milled. Note the miniature brass V-blocks – very handy things. You can see they are numbered. This is to ensure repeatability when using them with a 4-jaw.

And here they are completed. The block now weighs 60g. The initial square blank weighed 370g. That might not sound a lot of swarf to you guys with big-boy’s lathes, but it made a mess of the kitchen table with my Sherline.

More soon.

I then fly-cut some steel to size for the cylinder head blanks and drilled and counterbored to suit the block. All in all, I had to tap 30 blind holes to M1.6 in the block. A bit scary.

I also cut to size blanks for the cam carriers. They can just be seen in the background.

Another shot.

Steve

The flat-plane crank is assembled from EN1A webs and 3mm silver steel journals.

The assembly was a tight friction fit then drilled, countersunk, pinned and riveted. 1mm mild steel pins were peened into the countersink then filed and polished over to render invisible.

The unwanted journals were then sawn out and the gaps between webs cleaned up on the mill.

This still needs a bit of cosmetic fettling.

Steve

Edited By Steve Crow on 01/11/2020 16:23:37

Edited By Steve Crow on 01/11/2020 16:34:11

I've actually thought about making a 1:12 English wheel to form beer can aluminium for said monocoque.

Has anyone heard of this being done before?

I know. I considered a central one but life's too short.

Here is a drawing of a cross-section through the cylinders. It is sort of colour coded. Grey is EN3B, light blue EN1A, dark blue are screws and silver steel and orange or brown are brass except for the exhaust headers which are copper tube.

The air is fed from the two brass vessels (plenums?) in the vee.

This a hypothetical cross-section as there are 4 valves per cylinder and the banks are staggered.

Edited By Steve Crow on 02/11/2020 19:48:28

Thank you, I've just checked them out. It seems that 14BA screws are more easily available than M1 so I'll probably go for that. A finer thread too – M1 is pretty coarse at 0.25 pitch. I can single point thread down too 0.25 pitch on my Sherline lathe but I need at least 60 screws!

14 BA taps are quite pricy though. I might have to redesign a few bits so there are no blind holes, then I can get away with a single taper tap.

All the ones I've seen seem to be around the same price, £15 each so I suspect they are all the same manufacturer. There can't be too many companies making 14 BA taps! Has anybody got any recommendations?

Cheers,

Steve

This is the gear train for the cams. The camshafts rotate counter to the crank. The blue gears (EN1A) are driven or drive and the orange/yellow (brass/nickel silver) ones idle.

This is quite a bit simpler than the full-size engine, which has compound gears, but it does resemble it.

The gears are Mod 0.3 as I have a set of involute cutters. It would work in Mod 0.4 or 0.5 as well.

This is part of the build I'm looking forward to most.

Steve

Before I went any further, I thought I'd test fit them on the crank.

A fiddly job attaching these but everything fits and moves nicely with minimum play. The middle one at the front looks like it isn't straight but that's the camera angle.

I then tried the whole assembly in its bearings in the block.

The conrods do foul the block in parts but this is because they are no liners or pistons in yet so the rods are rotating more than intended.

I've got to say that it doesn't look like the bottom end of a racing engine – more like some late Victorian marine engine. The thickness of the conrods is massively overscale. This is a consequence of using the smallest screws I had.

Even then, I had to turn down the heads to 1.8mm and dome them for clearance.

This is also the reason why there is only two bearings. There just wasn't space for other journals.

I'm happy to answer any questions or receive any criticism.

Anyway, will update as I make more parts.

Steve