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Fixing the how NOT to make an engine
bogstandard:
This was the ending sentence of my last post about saving this engine.
--- Quote ---It is coming along rather well now, just a few more bits to make, and a couple of holes to straighten up and I will be into assembly time.
--- End quote ---
As can be seen from this pic, the holes were a lot more out of kilter than I first thought. It is no wonder that the port faces weren't sitting against each other.
This was just too much to try to straighten up, so there was nothing else to do other than go on one of my silver soldering binges.
The port holes were out of line and too large on a couple of them, so I went the whole hog and plugged up everything there was, even the port drillings, and start from scratch.
First off, make the bad holes even bigger. Stick a few bungs in there and get out the blowtorch.
This is how they ended up. Just like original, with no holes, but with an extra bit of meat here and there.
A little bit of machining soon had them looking a bit sweeter.
Faced off, and all holes in their right places, and square.
On the ST plans it showed the port drillings being done on an angle, from the port face to just inside the cylinder top and bottom.
This engine, as far as I can ascertain, is really for the beginner to model engineering, his first build maybe. To put angled ports on such an engine is absolutely stupid. A newbie will have trouble cutting things on the flat, never mind on an angle. Even I get it wrong sometimes, and I have done a few in my time.
So, I have made the port drillings how they should have been designed into an engine of this type.
Make a recess top and bottom to allow steam to enter the cylinder, drill the ports straight in from the port face, then drill straight down until the two parts are joined. Dead easy to do, and almost guarantees success for the newbie.
Because of all the hot work that has been done on these cylinders, I suspect that the bore has distorted slightly, plus any flux runoff may have eaten into the walls a little. So I will make a plastic cylinder hone, and grind the bore back into shape before I make the new pistons to fit, I am only talking about a couple of tenths, so it won't really make much difference to the spigots I have turned on the bottom cylinder bearings.
Bogs
Darren:
Blimey, that really was out of square wasn't it....
And I worry about some of my "not so squares"..... :D
shoey51:
nice work there Bogs :bow: :bow:
this a thread worth watching :clap:
rleete:
--- Quote from: bogstandard on July 10, 2009, 06:23:56 PM ---So, I have made the port drillings how they should have been designed into an engine of this type.
Make a recess top and bottom to allow steam to enter the cylinder, drill the ports straight in from the port face, then drill straight down until the two parts are joined. Dead easy to do, and almost guarantees success for the newbie.
--- End quote ---
Huh. That's how I did the port on my wobbler, not having any angle plates yet. I thought I was being so clever doing it that way, too.
bogstandard:
The purists would go ballistic if you told them to make the ports this way, super efficiency, free flow of gases and all that crap.
In what we do and make and in the sort of sizes we are talking about, it makes not one iota of difference to the way the engines run, so why not design them as simple as possible to make?
This is one time the engine designer has really got too big for his boots. Turning a simple design into a horror to make.
Bogs
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