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I would suggest honing your skills on something a little less complex (and less expensive to build!) before tackling the Merlin. If you are confident, perhaps try building the Whittle V8. It's all made from bar stock, so no castings to buy. If you are not so confident, perhaps try any of the bar...

I was there on the Friday and it was packed!

If you have an original Honda engine, the material of the head should be good for some heavy use. The CB125 (overhead cam) heads may be limited, but the CG125 is notoriously bulletproof. The rest of the engine will not hold together at such high RPM as would require valve springs so strong that...

Nice! My workshop also has the spatters of oil on the walls which record the first runs of several engines. (Not to mention the one on the roof which records the first test of an oil pump!)

Why would you think the original head design would not 'withstand high revs'? If the engine RPM is too high, I would expect the rod to be the first thing to fail. Higher RPM may require higher valve spring preload, but that would not impact on the head design unless it became so ridiculously...

Those were the days - pulling an engine out of a car balanced on top of three other cars, with a pile of old bench seats at the bottom to catch the engine! Not so much as a high-vis vest in sight.

I have had a little more time to work on this. I've made the rocker standard, the valve cage and the valve. The rocker standard is held in place by the valve cage, which screws into the cylinder.

Can we keep discussions civil please? We are all hobbyists and learning as we proceed.

Glow plug wire is an alloy containing platinum and rhodium. Definitely not simple nichrome resistor wire.

Perhaps the binding could be relieved by allowing one of the cylinders to float radially. I am thinking of it's bearing in an oversized bore, constrained by retaining plates front and back. This would be preferable to adding leakage. I would suspect that oversize bores in the cylinders could...

I presume there's agood reason why you couldn't use a conventional RC engine glow plug?

I've seen a few of this style of engine, but never built one. It's often referred to as an elbow engine.

One of the biggest problems will be vane stiffness. I have designed and produce rotary vane shock absorbers which operate at much lower pressures than an IC engine. The vanes in my shock absorber are fixed to the rotor shaft (not sliding) and need to be 10mm thick in an 80mm diameter chamber in...

But this is a rotary. The cylinders are spinning in the same direction as the prop. Airflow on the lee side of each cylinder will be turbulent and the small helix angle would be insignificant by comparison to the centrifugal "fan" effect.

I don't see why helical fins would make any difference to the air flow, especially on a rotary. It might be nice if my bike engines had helical fins - it would be easier to clean between them.

The cylinder is finished all but some final deburring. I tried to cut all the fins using a slitting saw. This was necessary for fins at the top and bottom, as they are not a full circle, but since I had the cylinder set up on the rotary table, I thought I'd do all of them. I used a 20mm...

Good to see engines being built to serve a real purpose. Looking forward to seeing the flight video.

Started on the single cylinder test engine: This is the cylinder. I have roughed out the outside, milled the profile for the induction port (rectangular lump on the side), milled the transfer ports and machined the bore. The thread in the end is M20 x 0.5mm. The cylinder is from EN16T. The...

Looking good! When I make the fixtures for bending pipes for my engines, I make the first bend, trim to length, solder the flange on, then make the fixture so that the flange bolts into place to align the pipe for the second bend.

When you bend the intake tubes, may I suggest that you modify your bending tool (the plate with a hole in it). I would suggest adding a fixture to locate the end of the pipe after the first bend is made and trimmed to length.