Gallery, Projects and General > Project Logs
Fixing the how NOT to make an engine
bogstandard:
Away we go again, little snapshots in time, when I have the chance to do a little more to this engine.
I left it last time with the main casting sorted, and the cylinders to be brought up to spec.
I will wait until I have finished the bottom bearings of the cylinder before deciding what to do with the pistons and rods. But just to make sure, I gathered the bits together to make sure I could make new of everything if required.
This is a lump of PB2, a little more difficult to machine than PB1, but it was the correct size for the job. So armed with a razor sharp HSS tool, I wacked off the metal until the bearing spigot was at the correct size.
Now this is where a benefactor comes onto the scene. Look what he dropped off. I have been contemplating buying one of these for a few years, but never got around to it.
WOW, it went thru that tough bronze as though it wasn't there. It works on the principle of deforming the chip as it comes off the cut, so stopping it jamming around the tool tip. You can see the swarf on the crosslide, it just curls it up in two dimensions, and throws it out. Unfortunately this tip holder can only go deep enough for a 7/8" bar, so I will look around for a longer nosed one that will cope with larger diameter bars, now I know what a wonderful system it is.
The first one ready for the next stage.
Soon followed by it's twin.
Now comes the stage where people make their main mistake. They do one component machining operation, then do the next component, then go back and drill and ream holes.
WRONG
You must finish off each component separately to it's conclusion, only then change over the component and carry out the same ops.
The first op is to machine the spigot for a wringing fit into the bore.
Then drill and ream, or bore for your finished sized hole. By doing it this way, it will ensure that the hole is truly concentric with the bore. Only then do you swap over and do the next piece. The outside shape has nothing to do with the well running of the engine, this spigot and concentric related hole is the bit that needs to be spot on.
Once the two bearings were done, it was found that the pistons and the rod ran perfectly in the bores, so I decided just to make new pistons which were a little small on diameter, and will be made at a future machining spell.
Getting away from the pistons and end caps now, notice how close the holes are to the port faces. I think that the cylinder covers were fitted first, then the port faces were machined down a little too much. To such an extent, that the brass screws that held the covers had almost half the heads machined away.
I can see another fix coming on.
Grab a bit of brass rod on nearly the right size for 7BA. Then a quick and dirty exercise to make a length of threaded rod. 30 seconds work to cut a length of thread about 3" (75mm) long using the die holder off the lathe and a rechargeable drill.
I wasn't too worried about the quality of the thread, as long as it screwed into the holes.
Like the repair to the main casting, bits of rod were screwed into the holes after first dipping them in flux. Then they were silver soldered into position, using the same method as use on the main casting.
A quickie machining job and the cylinder was back to square one, ready to be drilled in a better position.
The problem now was that I had steel cylinder covers with holes in the wrong place. So a bit of brass plate was cut to size and annealed, a mandrel turned up to bend the brass around to get to the basic shape, then a bit of bending in the vice soon had two new brass covers made. I will drill, tap and fix them in position after I have made the new pistons.
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.
Bogs
shoey51:
:bow: :bow: as usual a great narrative with pictures top work :clap:
bogstandard:
Shoey,
By the time I have finished, I don't think there will be an area on this engine that will not have had work done on it.
The reason I show everything is to make it clear, that nothing is really lost forever. Most things can be 'fixed', no matter how bad they were in the beginning.
You may ask, was it worth doing all this work on such a bad example as this?
Financially, NO. If I was to charge him a going rate for the job, this engine would cost many times more than the original cost of the kit.
But, to me YES. I am getting a great amount of enjoyment from rescuing and fixing this engine up, and the look on his face and his feeling of joy when he gets a running engine back will be more than enough reward for me.
Basically, all he will be paying for is the raw materials and consumables, plus postage costs, and all it has cost me is a little of my time, which for a fellow modeller, I just can't bring myself to charge for.
All on the understanding, he gets it back when I have finished, no time limits. If time limits come into it, then charges apply.
Bogs
Darren:
It's very inspirational to see that all my botched work can be saved later once more exp has been gained..... :ddb:
rleete:
--- Quote from: bogstandard on July 07, 2009, 06:08:58 AM ---I am getting a great amount of enjoyment from rescuing and fixing this engine up...
--- End quote ---
I know exactly what you mean. I sometimes spend an inordinate amount of time and effort to refurbish something that could more easily be tossed out and replaced.
Any fool can spend money, it takes a bit of talent to fix things.
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