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Low surface area to volume ratio is definitely an issue. Heat loss rates are higher relative to the total amount of air. Likely more an issue for cold starts than once the engine gets going.

The downside to spiral taps is that in my experience they are easier to break than a standard tap (also they don't seem to work so well in small sizes). Spiral point is good for through holes but awful for blind holes. And of course fluteless is useless for brittle materials and plastics. Horses...

Anyone who single point cuts a thread when they could have used a tap or die has waaaaay too much time on their hands. I say this as someone who has single point cut a lot of threads. What's even better is when you can cold form the thread with a fluteless tap. No stopping to clear chips, just...

I don't often have time to do machine work during the week, but the 3d printer is at my apartment so I can sometimes print a part. I just did the rear gear cover, from carbon fiber filled nylon 6. I think this is the best part I've ever printed from this material, must have finally got the...

This resonance for performance business is very common on modern cars, in fact it isn't uncommon to find cars with manifolds that have multiple runners of different lengths and shutters that can open and close them, so that the engine can have two or more optimal resonant speeds. The automatic...

I have a small engine compression tester, but I would need to make some kind of funky adaptor to allow it to connect up to the injector hole. I think my next mission is the rockers and pushrods. I've been a bit indecisive on this matter, and actually designed two options Which option do...

A bit more progress on the cylinder head. Valve springs, keepers, hold downs for the injector all made. I lapped the valves and made a crush washer for the injector. With the head on and some grease as a temporary seal to the block, I was able to test for compression. The good news: there is...

Nylon can be a little peculiar because it absorbs a lot of moisture from the air (and becomes a lot softer when it does so). I've worked with nylon bars that have a substantial difference in colour at the surface where the plastic has been exposed to the atmosphere, compared to the interior. I...

The emulsion tubes have another important function, which is to compensate for the tendency for the mixture to get richer as speed of airflow through the carb climbs. Usually they are fed by a jet or needle such that the level of fuel in the tube drops with increasing flow through the venturi...

Hola, el motor aún no está completo. Puedo publicar los planes una vez que se haya completado y se haya demostrado que funciona.

I for one am looking forward to seeing what the results are like!

My thinking on the plenum/trumpets layout is that the trumpets could act as standpipes that stop the 'pooling' from entering the cylinders at all. Though perhaps this might lead to problems with the mixture ratio when the throttle is suddenly opened or closed.

Some early radial engines brute forced the problem by ducting the mixture through a rotating fan mounted on the rear of the crankshaft, the spinning blades 'stirred' the mixture in an attempt to even out the fuel flow to each cylinder. Later that role was assumed by the gear driven supercharger...

I wouldn't store it for more than a year. This is because of the diethyl ether content, upon exposure to oxygen it slowly reacts to form diethyl ether hydroperoxide, which is a dangerous shock sensitive explosive. Evaporation can concentrate the hydroperoxide to the point where disturbing the...

Hang on. You live in a cave, and you are a knight? You don't happen to dress as a bat and go out to catch criminals at night do you? Jokers aside, I'm enjoying the details of this discussion. Especially as a 'mug' who tends to just throw FEM at problems like this.

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.