folks, hi,

i've just joined this forum because i'd like to make an engine... from scratch, and whilst i am a software engineer, used to make my own lego model designs, did metalworking at O'Level at school and can weld (badly) i would greatly appreciate advice in keeping this as simple as possible, low-cost as possible and easy to do as possible.... and that includes the tools: i will be literally starting from scratch.

here's where i'm keeping pictures and documentation on the design:
Index of /engine

the design is constructed from expired and invalid patents. it is a double-opposed piston arrangement, 2-stroke *ported* design - not one set of ports and a valve per cylinder but a *purely* ported design like the old steam engines. moving parts are kept to an absolute minimum.

the compression ratio can go up to 30-to-1 (!) and i aim to use this not for power but for ultra-efficiency instead. the maximum RPM will be 2,000 (the original design used triple-sleeve bearings and could do over 15,000 RPM. back in the 1950s this was quite an achievement). i aim to make the cylinders each 125cc: 50mm bore and 50mm stroke, just because it sounds like reasonable round numbers (advice appreciated here).

the only thing i have to watch out for is that the design uses "detonation" at TDC. i.e. the spark is fired at around 90 degreees *BEFORE* TDC, when the 30:1 compression is about 1/2 way along and has compressed the air-fuel mixture down to about a 15:1 ratio (which is enough to make it ignitable).

by the time the burn gets to TDC it's so damn hot - over 1800F - that the air-fuel mixture goes into hydrogen-oxygen burn and it's pretty much all over, there and then, within a few degrees of TDC. this is *completely* different from a standard 2-stroke or 4-stroke, where the fuel is still burning when the exhaust valves open at BDC.

so the only thing to watch out for is this rather hot flash at TDC, but even there i'm advised that it's over so quickly, and the decompression stroke is so immensely long (1:30, obviously) that the piston head hardly has time to even heat up, and the exhaust gas temperatures are (obviously, given the 1:30 decompression) down to something like 250F or less.

also, if you look at the (rough!) image, you'll see 4 red blobs per piston: these indicate piston rings - one on each of a pair of piston heads. the set in the firing / exhaust chamber will need 3 rings; there is only one ring on the piston in the intake / mixing chamber. the pistons themselves can be incredibly flat, because there is *no* side-loading. at all.

the only thing is that there must be an inner tube which seals (approximately: it does not have to deal with huge pressures) against the side-wall of the piston, to shut off all the ports in between TDC and BDC. a perfect seal is *not* essential. i figured that using a screw-threaded rod to join all three parts together, and lock the central tube down tight, would be sufficient. perhaps put grooves in each of the pistons for the central tube to fit into?

anyway: advice on materials that are the simplest to use and work with, as well as some recommended tools, would be greatly appreciated. contrary to potential appearances, this isn't a particularly sophisticated design: it's just different. the only thing i will have to get made by someone else is the cams: they have to be hardened, they have to be absolutely precise dimensions, they need to be plated, and there's no way i can make them myself.

thanks in advance.

l.