The 3D Scallop finish path takes some weird and wonderful routes. Basically it steps over a given amount which in this case was set at 0.2mm no matter what the angle of the surface is. So unlike the Adaptive which leaves horizontal steps much like contours on a map the scallop can end up moving in quite complex paths as it may reach a more vertical edge in one direction while still cutting a near horizontal area in the other. I expect the software works out the shortest route to cover the whole surface and that is why it can seem quite random at times.

The original engines came with the two disc type crank webs as iron castings, the one I have based mine on would not turn over and one of the main reasons was that the crank had twisted at one or both of the crank pin to web joints. For this reason, I decided to make my webs from steel so that the whole crankshaft assembly could easily be silver soldered together.

The two webs were first turned, drilled and reamed 8mm on the lathe and made good use of a couple of bar ends. I used a CCGT 060208 insert to give a nice fillet to the internal corner.

The webs were then held in the 3-jaw chuck using soft jaws and the “cast” recess milled. The majority of the material was removed with a 4mm cutter using an adaptive tool path, this needed a bit of tweaking of the parameters to get the 4mm tool into the narrow gap but was done mostly by reducing the minimum cutting radius. That cutter is starting to loose it’s edge I can hear a bit more noise and it left a small burr around the edge of the cut then changing to a cutter with a 1mm corner radius the bottom of the recess was finished with a horizontal path and lastly the edges of the recess done with a contour going round twice. At about 3.00 mins in you can see that the shaprper cutter removes the burr from the earlier adaptive op.

The usual methods of a full length shaft and pin with reduced ends were use to make the other bits from PGMS which was then silver soldered together before a quick clean up skim of the webs on the lathe before the middle if the crankshaft was cut away. Quite like the black oxide from heating that has been left in the recess

All seems to fit and go round as it should. I’m not going to fit a pulley on mine so just made the crankshaft on the near side a bit longer than is needed for the eccentric as it saves a bit of shelf space!

To hold the part machined cylinder while the end flanges were given their “teardrop” shape I used the CNC to make a simple fixture with two spigots that located into the cylinder and valve bores and tapped for a couple of M6 fixings. It was then just a cas eof screwing the cylinder to the jig and running a 3D adaptive to remove the waste and then a finishing 2D contour on each end.

Any excuse for a quick test fit

I also turned up the cylinder and valve end covers. This is the spigot that will locate the cylinder into the trunk guide being turned as a second op and held in the softjaws and the trunk guide being used to gauge the final diameter

Here are the four covers with all the lathe work complete. I also turned the two bronze glands as “tophat” shapes and drilled their two stud holes in each.

Over to the CNC the holes were drilled and tapped as required, the bronze glands screwed into place and the two machined as one to their final elliptical profile.

Well it would be nice to say it all went well but I did make a bit of a booboo profiling the first cylinder end. I thought I would be clever and draw the jig in F360 with the larger spigot centred on the X-Y axis as that is what I had used as the datum on the cylinder CAM. However I forgot that when going from design to manufacture (CAM) in F360 the part centres on the material by default so when it came to cut the profile the cylinder was 10mm to the left of where the cutter thought it was. As you will see instead of taking a 0.6mm cut off the left edge the cutter went in at the full 6mm width. Luckily it was on the side of the teardrop where the most metal needed removing and I was able to click the stop icon before I cut into metal that was meant to remain, it also kicked the jig off to the right so that had to be centred up again. :-[

That is why I don’t use my electronic edge finder on the CNC as it is rigid. Mind you it does not do the other type much good if you spin them at 5000rpm as the spring tends to let go but at least it keeps Ketan’s profits up!!

Swarf production continues at a pace. This time it is the flywheel which was cut from a 25mm slice of 95mm dia cast iron bar, in fact m-Machine sent me 28mm so even more swarf! As I usually do I started on the lathe machining the OD, one side and boring to fit the crankshaft then flipped it over to face the other side.

Then over to the CNC to form the spokes. You are probably getting used to this by now but an adaptive tool path was used to remove most of the waste material

Then a scallop path with a 4mm ball-ended cutter to finish it off. The two were repeated for the second side to complete the CNC work.

Those with a fear of getting cast iron swarf on their chucks and machines should look away now as this is what 40% of the bar now looks like with the remaining 60% as swarf. That was just the CNC work, probably more like 25/75% if finished item compared with supplied stock.

After a quick bit of file work and a tickle with the Dremel to remove machining marks and give a bit of “casting” texture this is what the finished flywheel looks like. The engine I am basing mine on did not have the original flywheel so I have gone with something fairly chunky which seems to suit the rest of the engine which was made to do work rather than be looked at.

The cylinder cladding sheet made a nice change from machining. I started by cutting a strip of 28g copper a couple of mm wider than the length of the cylinder and also about 10mm longer than needed as that was what size sheet I had. The first thing I did was to drill the clearance hole for the inlet boss by clamping to a suitably angled bit of wood to match the angle of the cylinder and then used a step drill to form the hole.

The strip was then wrapped around a couple of bits of bar to get the basic shape before screwing one end to the underside of the cylinders end flanges. I could then wrap it around the cylinder to mark the final length which was then cut and filed before adding another two screws to fix that end. With it screwed into place I filed off the extra length at each end until it was flush with the cylinder. When fitted the two ends butt up against each other but it needs a bit of spring to allow it to open and slide over the inlet boss.

The next item to tackle was the crosshead, like the original I made this from cast iron but used 25mm bar as my starting point rather than a casting. This was turned to just enter the trunk guide, faced and tapped M4 x 0.5 before being sawn off the bar and faced to final length. It was then lapped into the trunk guide with 600g silicon carbide powder mixed into a paste with oil.

Then over to the CNC for a bit of shaping. Adaptive with a 3mm tool to start, then the horizontal surfaces were finished with the same tool before changing to a 2mm dia ball nosed cutter to do the “hump”. As this was fairly flat I opted for a parallel finish path with 0.15mm stepovers. Last thing that side was to drill and ream for the pin after which it was turned over so the same milling paths could be run again to do the other side.

That is the old style, the new ones have more holes for more toys drills😁

I decided not to go with my usual light colours on this one but don’t worry I’ve not bought any dark green or maroon paint!

As the old original engine that I based mine on had quite a nice patina I decided to see how close to that I could get and am quite pleased with it. The colours are actually a little bit darker than they have come out in the photos. There are a couple it parts where the paint could have done with a little more blending out but on the whole it is the sort of look I was after.

Runs reasonably well too, when I test ran it before painting it was wanting to levitate a bit at high speed which is why I have it running for quite a while in the video as I was expecting it to start moving about but seems my final tweaking of timing smoothed things out.