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The common austenitic grades of stainless (304 and 316) are a bad choice for a cylinder liner. Some other kinds would work, but you need to know what you are dealing with.

Having used a battery operated chainsaw, they are actually rather good. Not the sort of thing you'd use for serious forestry work, but very handy for cutting small trees, thick branches and so forth. The one I used had a 10" bar, so a fairly small saw.

Congrats, you must be thrilled! It sounds great too, a lot like a full sized aircraft engine. Do you think you will put a propeller on it?

Cast iron is going to be a much better partner than mild steel, but it isn't immune. This is for example why internal combustion engines normally use bronze valve guides if they have stainless valves, whereas cast iron guides are extremely common in engines that have regular steel valves. It...

Because you have full round crank webs, you can likely re-use your existing crank. A large diameter, narrow width bearing running on the web should suffice. Alternatively you can try lightening your crank to work with the existing two bearing setup.

Common austenitic stainless (grades 304 and 316) is much more prone to galling than mild steel, so I'd be wary of using it for heavily loaded shafts running against metal plain bearings (plastics are fine, and metals under lighter loads are ok too). You can use grade 431 martensitic stainless...

When it comes to flat engines (opposed twin and opposed 4) the crankshaft is arranged as a 'boxer' configuration, the pistons in each row move in opposite directions to each other. This balances both primary and secondary forces leaving only a small rocking couple from the cylinder bore offset...

Titanium has poor thermal conductivity for a metal, theoretically it should reduce heat losses. But mostly I just wanted to try it.

Hi all, Here's the next step. New hold down feature milled, holes drilled and tapped. And we're going high-tech, as I've made the pre-chamber cup... from titanium! The cup pressed in to the head very nicely.

I start my designs on a spreadsheet, I've made one that estimates things like power output, valve sizes, stresses on bearings and conrods etc. Once the basics (bore and stroke, compression ratio, bearing sizes) are figured out I can start designing in CAD and put my parameters back into the...

Machining helps me chill out and not ruminate on my anxieties. So I needed something to machine! Also it's good practise for my skills.

I wonder if your ignition coil is no good. I know it sparks when you take the plug out, but a short inside the secondary winding of one side could result in a very weak spark that fails under the compression in the cylinder. Might be worth checking both secondary windings with a multimeter and...

Nice work! I had similar tiny hole issues with the oil ring for my diesel. For consideration in future, I think it may be possible to replace the tiny holes with slots cut by slitting saw. I did this on my oil ring, and it should be possible on the piston as well, if you are careful about the...

Does your compression tester have a check valve? Many don't, and the dead volume of the tester itself messes up the compression ratio of small cylinders causing incorrect low readings.

Sadly I can't turn the bolt pattern because there's no room under the rocker shaft support. You made a good point with the clearance for the pushrods, so I went back and checked: I can confirm there's plenty of clearance!

Methanol will need a far richer air fuel mixture (6.5:1, rather than 14.7:1) than petrol, so one possible issue is that your carb simply can't provide enough fuel. The other issue I've observed trying to run my Webster engine on alcohol is that alcohol has a higher boiling point than the 'light...

Yikes that is a lot of oil in the fuel! Your plug must foul quickly. Do you need to use SAE 50? Modern air cooled 2T oil is SAE 30. I've caught more ignition coil zaps than I care to mention. The most painful was from an old Lucas impulse magneto, my younger brother handed me the ignition lead...

In essence the critical speed is the point where any out of balance weight (and there is always some) can overwhelm the crank's stiffness. The crank will begin to whirl around like a kid's skipping rope (or jump rope). So obviously this will happen at much lower speed with no center support, as...

The crank is subject to 'whirling' motion independent of combustion forces. That will become a significant issue as RPM approaches its 'critical speed'. https://roymech.org/Useful_Tables/Drive/Shaft_Critical_Speed.html Rdean will have to calculate this to be sure of his limits.

You might be surprised by how well it holds up even at higher revs. The Austin 7 car has a 4-cylinder engine with only two bearings, but broken cranks are apparently only an issue if you race them. Having handled an Austin 7 crankcase and cylinder block, you'd be forgiven for mistaking one for a...