A few of you might remember a project that I had mentioned that had come into my workshop.
A very high quality marine steam engine.
Well I contacted the owner to see if it was OK to show my refurbish on the site, as I thought it would be a nice change to see what happens to these old but well made engines, and he very kindly agreed.
I will just explain how things work.
Unlike when you do work for yourself, where you can just do things as you want to get the job done.
When you do something for someone else, they are relying on your expertise to do a good job, and give them value for money without ripping them off.
After being a marine modeller for well over 40 years, I understand exactly what it is like, entrusting your pride and joy into the hands of a total stranger. Hand it over to a cowboy and you will be in trouble from the start and most probably pay thru the nose for the privilege. What I do is come to an agreement on rough costs at the very beginning (I give a substantial discount to fellow modellers), and keep the customer updated if it is to be a long job.
So basically the engine came to me with a list of faults, and with instructions to get it working to the best it can be.
What I do initially is totally ignore where the problem is liable to be, and give the engine a good going over.
The engine came with a requested set of plans, so if any faults on the mechanical side shows up, I should, without too much trouble, be able to remake any parts that are required.
So I went all over the bottom end of the engine, and soon came to the conclusion that this engine had been made by a very experienced craftsman. No corners had been cut, and it was made to a great standard, and no wear or faults could be found anywhere. It goes to show, if an engine is made well and looked after, they are bombproof and will last forever.
So once I am satified that no other work is required, I then concentrate on the problems that the customer has listed.
In this case, a gasket had 'blown' and steam was leaking everywhere, plus he would like the timing 'put' right.
Blown gaskets are a common fault and normally people just replace them, and carry on until it blows again.
I don't like that idea, if a gasket has blown, there is usually a reason for it, and I soon start to find the problem.
These next few photos show what I found.
The first thing that I noticed was that the top end on the valve area was held together by slotted screws. Normally studs with nuts and washers should be used, and with checking on the plans, I was shown to be correct on my assumption. I suspect that sometime during it's long life, one of the gaskets had blown, and someone had replaced the originals with brass screws. Or the original builder didn't get to finish the engine off, and someone with lesser knowledge had taken over the finishing off. But unbeknown to them, screws cannot be tightened down enough to make the gasket stable, and so it will just keep blowing. I will be putting it back to original, how it should be.
So now to disassembly.
This is the main steam face, and was sealed with some sort of compound instead of a gasket, and later pictures will show what it had caused.
This is the steam chest and slide valve off this end of the cylinder block. Also shown are some very hard remnants of the gasket goo
This is off the opposite end, which hadn't blown, but it also showed another problem.
You can see on this shot how hot this end must have been running, it has actually 'blued' the surface of the brass, and by the looks of it, the gasket was very close to blowing.
Only assumptions can be made of the cause of this problem, ranging from loss of lubrication and very high temp steam or air entering the valve chest, or what I suspect, this end of the engine is very close to the boiler. I will advise the owner to make up a small shield to go between the engine and boiler to try to keep the heat down.
Both faces were gently cleaned off, and it shows the damage on the face, both ends were scored by the same amount. I suspect this has been caused by fragments of gasket goo being trapped between the sliding faces. The deep score is about 0.002" deep. That is a massive groove when put into the context of a finely lapped sliding steam face. It will also account for the lack of power and the assumption that the engine timing is out, this scoring will allow exhaust and pressurised steam to go anywhere it wanted to.
After a lot of tedious hand flatting and lapping, both faces were brought back to a perfectly flat faces. Before final assembly the slide valves and the faces will be lapped together to get gas tight seals.
One slide valve has been cleaned off, the other is about to get the same treatment.
While I am at the top end poking about, I decided to take the cylinder caps off. These again were sealed up with liquid gasket. As luck would have it, the internal spigot had stopped any going down into the cylinders and causing any damage. Just general gunge in there which was cleaned out.
Without a full bottom end strip down, I can't check the whole of the bores, but I will check what I can.
No sign of any ovality, and both bores measure exactly the same.
I checked for taper in the bore, with the same very good results.
While I am working on the engine, I am also on the lookout for areas where problems might occur in the future.
I will be making a full set of top end gaskets from PTFE sheet. This is a great substitute for the old waxed paper product, and shouldn't break down over time like paper does. I was a little worried how thin the steam covers were, even though they were made to drawing. So I knocked up a couple of new ones out of thicker material. It was then that the suspicion that someone else had taken over the finishing of the build on this engine. Everything on the engine had been built to superb standards, except this top end, the bolt holes were at different pitches, and it took me quite a while of measuring and calculation to make a pair that would fit either end.
Also, I will be fitting studs and nuts instead of screws, so I had to check that no overhang would take place when they were fitted, the one on the right is how it will look. I tried the same thing on the cylinder covers, but because of the way they have been made, they will go back on with just hex head screws with no washer.
So now I have the covers made, I can use them for the patterns to make the gaskets up.
To be continued
Bogs
