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Stay Brite is not a silver solder, it's silver-tin i.e. a soft solder, not suitable for high temperature or strength.

Picking up this thread again after being away, the comparison between SLM and DMLS is interesting. According to the PCBWay web site, the two processes seem to differ only in the degree of melting of the metal particles. DMLS melts them partially, leaving some rigid material to provide support...

Olli, you probably know this but in case not I suspect the problem you have is because the tank is a long way behind the engine and your throw causes a pressure drop in the line. In our (competition) FF models with side mounted engines running on suction the tank is often mounted beneath the...

Returning to 3D printing, here is better evidence of the print orientation. This is a macro picture of the top of the block in oblique light. It shows that this surface has shrunk unevenly across the whole face. In contrast, the vertical surfaces at either end of the crankshaft housing show...

Come on Lloyd, I learnt Fusion to a useful level a couple of years ago, at the age of 77. It's nowhere near too late. I suspect there are plenty of teaching videos on Youtube. Going back to Autosketch is like stepping back into the dark ages!

Re the print orientation, as mentioned it in my first post, it seems to have been printed with the cylinder bore upright but its not very clear. I'd like to know more about the process.

Yes, that must be the alloy, they only offer one for SLM printing I think. As to test pieces, this is it. My only motivation was to get a Sugden Special crankcase to work on so I haven't considered any other experimentation. The design was done in Fusion and the stl file sent off to PCBway...

The accuracy of the selective laser melting (SLM) process is specified as plus and minus 0.3mm so I made the crankcase and cylinder bores well undersize to ensure there was plenty of meat to machine. The front housing is left solid so there was no danger of inaccuracy in a printed hole pushing...

I have used PCBway to print a Sugden Special crankcase. The accuracy and finish is generally good but there is evidence of what looks like post-print fettling which has left some minor marking in places. The only major issue is that the four radial mounting lugs have warped forwards so they...

The leakage past the contrapiston suggests it's much too loose, it should be a firm press fit in the cylinder. A loose contrapiston is a no-no. You shouldn't need a locknut on Midge if the fit is OK. Contra hitting piston is a definite big deal. Before you make a new contra, try expanding...

Working in 29/64s and suchlike is beyond me so I redraw parts in metric with dimensions from what i think will be DRO reference edges. Less scope for mistakes too.

Diesel fuel will last indefinitely provided (a) that the container is airtight and (b) that the container is opaque or nearly so, as per Bluejets brown bottle. Glow fuel is tolerant of daylight, diesel is not. Nice Midge, mine runs well. In your 2nd video yours sounds overcompressed.

Try metal polish.

Please don't run it on that prop, it may throw a blade which is extremely dangerous. It is made for electric motors and not designed to withstand the vibration inevitable in an i/c engine. Good luck in getting it running.

Well done. Did you make a new piston?

Yes, but I only heat once and let it cool, then re-lap. I have never found any problem with the pin fit afterwards, though I suppose if it was retained with a light interference fit it might become noticeably looser which might have to be dealt with. Roy

Rather than make new, why not try "cherry-bombing" the piston and contra to make swell a bit? Often works for me.

Hi Pat. I'm following your thread with interest because I'm also building one. My scrap bin is far from empty! The drawings show two methods for cutting the transfer ports, the one you are contemplating and another with the flute extending from a hole drilled at rightangles into the bore. I...

I'm a control line and free flight man too, don't know much about throttles! What I've found in doing Nelson glow head conversions is that getting the compression ratio right can be difficult and often takes a bit of experimentation. When it's in the right ball-park, setting the needle...

Well done on getting it running, it sounds strong, revs sound OK to me. The motor is on the boundary between 2 and 4-stroking in the second video. If you can lean it out to pure 2-stroking, the compression ratio is OK (though you might get more power by increasing it). If it won't 2-stroke...