I then came across another little problem. Having machined the sole plate flat this has now lowered the cylinder by six or seven thou. The piston now appeared to hit the top of the cylinder and prevents the crank from going over centre.
I have the "Building a Vertical Steam Engine" book but I think there are a few errors in it. On page 64 it gives the length of the piston rod as 45mm PLUS the 4mm and 6mm threaded portions giving total of 55mm. The plain section on this engine is approx 37mm long. Because of this the piston bottom is 2mm above the inner face of the lower cover. I have a feeling that 45mm in the book is the overall length and the plain section should be 35.719mm (1 13/32" not 45mm. JasonB confirmed the 1 13/32" for me, so I now had to shorten the piston rod 1.04mm. Borrowed a friend Hardinge lathe with 5C collets as was able to insert the piston rod complete with piston from the rear of the collet and have enough sticking out to shorten as required
The cross-head was also very close to the bottom of the piston gland. This looks very close. Investigating the piston gland and housing showed up the fact that the thread only went half way down the bore.
Fixing someone else's poor work takes a little longer than you would think.
With the mods to the piston rod and the gland nut thread in the bottom cover I temporarily assembled the engine. Had a few issues with it locking up when tightening the nuts on the valve chest but eventually sorted this and finally had it running briefly with the air line nozzle blowing into the inlet port.
Gradually speeded up as it freed up. Ran it for about 5 minutes, it was a lot better after squirted some clock oil into the steam chest.
The engine turns over quite easily by hand. It does not appear to be tight anywhere. The piston is very free in the bore (maybe too free). BUT It needs a quite high PSI to get it to run.
Plan had been to now sort out the cladding and pipework. Whilst I am painting it I can continue with the making the reversing gear.
This quickly went out of the window. Because it did not want to run very quickly, I decided to take another look at the steam ports. The ports on this one I am attempting to resurrect are not cast very well, in particular the left hand one in the photo. I was not sure how they are would effect the running of the engine if they are left as is and wondered about filling the left hand port with JB Weld and then re-machining to the correct size/location. Discussed options with several people (JasonB and others) and it came down to fill with JBWeld and re-machine ports, or remove ports in their entirety and replace with brass insert with correct port slots.
Having had a much closer look and spotting some "white stuff" in the miss-shaped port it looks as though there is a small blow-hole between the exhaust port and the miss-shaped inlet port or more likely when drilling the port through from the end of the cylinder it was drilled too far. It has possible had some filler put in somehow. Looks like it will definitely have to be the brass insert. This insert may have to be at least 1/4"" thick as it is now going to have to replace the port slots in their entirety.
After some thought I opted to mill out the poorly formed ports. In order to do this I needed to remove the studs the previous builder had fitted for the top and bottom covers in order to mount in the vice.
The studs decided to fight back. Well one of them did. Five on the upper cover end came out easily. Four of the lower ones came out relatively easily. The last one fought back and said no way am I leaving this casting in one piece and promptly sheared flush with the top of lower face. Bugger I thought.
I actually said something worse.
I knew drilling it out would be fraught as it needed a 2mm tapping drill size and if this wandered being such a thin drill it would go down the casting in preference to the stud.
I set it up in the vice and refitted and bolted the top cover down.
This now gave me a fixed location. I then used my centering scope for the first time in anger to locate on the hole in the cover.
Once located i remove the top cover and the studs. Fitted a 2mm slot mill and very gingerly raised the table to bring cutter and stud together. Ran at approx 1500rpm and worked my way through the stud. Once remnants cleared out was able to run 7BA tap back down the hole. That was quite a relief.
Blued up the port face on the cylinder and lightly scribed a box around the area to be milled out. This was my sanity check to ensure I had my DRO settings correct. Clamped in vice and set level and set up a 3/16 slot mill.
Initially put in four corner holes at 1/8" depth, then reduced the DOC to 1/16" and milled out first layer. Dropped down to the 1/8" point and took out another layer. I was hoping to get away with this but needed another 1/16". Looked good at this point so them went round the periphery with a full depth cut removing final/1/64" all round.
Pleased with that now need to make the brass insert.
I have never used JBWeld before so am not sure how much smaller I need to make the brass insert. I assume I need the JBWeld as thin as possible. Is it fairly thin as soon as it is mixed. I was think that when the brass insert is pushed into place to use, either flypress or arbor press to push it as fully home as possible.
Colin