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Post by steamnovice on Sept 13, 2011 10:31:22 GMT
Photo 5 Attachments:
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Post by drjohn on Sept 13, 2011 11:51:01 GMT
The bit in the red circle looks a bit scruffy and could be leaking. DJ Attachments:
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Andrew C
Part of the e-furniture
Posts: 447
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Post by Andrew C on Sept 27, 2011 21:19:56 GMT
DJ That looks horribly like a crack in the wall between the inlet and the ports. Have you managed to fix it? If so how? I suppose you could run some high melt softsolder in but it would ware down quickly. A better solution would be to silver solder in a replacement wall and re machine the port enterances. Either way not much fun  Andrew |
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Post by drjohn on Sept 27, 2011 22:20:02 GMT
Hi Andrew - that's steamnovice's cylinder not mine!
DJ
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Andrew C
Part of the e-furniture
Posts: 447
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Post by Andrew C on Sept 28, 2011 6:46:23 GMT
Er yes I realised that after I wrote it, sorry. Still a bummer of a job to fix though.
Andrew
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Post by steamnovice on Sept 28, 2011 8:09:29 GMT
Well, nobody said this was going to be easy to fix, but I have had to virtually do a full strip down to get the cylinder off (see photo). OK, I know..."...if you'd made it yourself in the first place instead of buying 2nd hand you'd know exactly what was involved". Further information and pictures to follow. Attachments:
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Post by steamnovice on Sept 28, 2011 8:11:45 GMT
Porous cylinder? Looks more like a sieve to me. The photos don't really show the full horror... Attachments:
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Post by steamnovice on Sept 28, 2011 8:12:21 GMT
And this is the view from the other side.... Attachments:
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Post by steamnovice on Sept 28, 2011 8:14:19 GMT
And this is the view on the piston end....Whoops! Attachments:
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Post by steamnovice on Sept 28, 2011 8:29:46 GMT
And a view inside the bore shows another hole! Although it doesn't appear to connect to outside. Now I know that Dr John would throw it in the scrap bin at this point, but my workshop is in packing crates for another year so I want to try to fix it. It doesn't look like there are any cracks in the casting, just lots of holes The casting is soaking in parafin at present. This is my plan: - change the parafin for a lighter solvent
- try the gentle application of heat to try to get the solder moving/out
- try to Comsol some brass fillers in place to fill the unneccessarily deep void at the bottom of each inlet port
- talk nicely to someone at the Bristol club to skim the port faces and damaged end faces on their miller
I'll keep you all posted.... Attachments:
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Post by ettingtonliam on Sept 28, 2011 16:25:21 GMT
Jeez! You'd wonder why anybody bothered to spend time and effort machining a casting that was that bad. Long term, the only solution is a new casting, but I know you can't do that for a while. Just a suggestion, file the outside of the casting smooth, to get rid of all the lumpy bits, so you can see better where the porosity is. Tin the outside with Comsol, plus that nasty score on the end, and that blowhole in the bore, then take the machined surfaces back down level with a scraper and/or emery cloth. Hopefully, together with remedial work on the valve and valve seat, this will reduce the 'blow'. Just enough to keep you running till a new cylinder is possible.
Richard
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abby
Statesman
Posts: 927
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Post by abby on Oct 5, 2011 20:06:07 GMT
I rarely make a casting quite that bad but occasionaly a piece of dislodged investment or carried over slag will spoil one.
Rather than scrapping it , I drill out the offending debris or stress crack and fill with silver solder.
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Post by steamnovice on Oct 17, 2011 8:00:53 GMT
Well Abby, looks like you might be correct....see below. I did as follows: - Removed most of the solder from the bottom of the inlet pockets using a Dremel and burr (see photo)
- Soaked casting in paraffin for several days
- Soaked casting in brake & clutch cleaner for 24 hours
- Soaked casting in Citric Acid pickle for 1 hour, rinsed, Sodium Bicarbonate wash, rinsed, dried
- Made some thin brass plates to fit in the bottom of the pockets
I did a melting point comparison test and proved that the solder that the original builder had used on the casting was a very low melting point solder. Attachments:
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Post by steamnovice on Oct 17, 2011 8:05:17 GMT
I then applied Baker’s soldering fluid to the pockets and heated the casting. The first thing I noticed was the existing solder melting in the pockets and there was almost enough remaining there to tin the brass plates I had made. It took a lot more heat before the Comsol would melt. But before it did, I noticed little beads of solder appearing in a ring around what I previously had thought was a circular machining mark. I now realise that the builder has let in a circular disc of brass or bronze and soldered it in place using soft solder. Perhaps he struck major porosity once he started machining the casting or maybe he cut the ports badly and had to start again? Either way I have a dog’s breakfast of a casting. So, has anyone used gunmetal cylinder castings from Model Making Supplies (or Blackgates?)? MMS are advertising a Gunmetal cylinder set for £188 which is a bit cheaper than £422.96 from Reeves! I will rebuild the loco using this cylinder regardless as it is the quickest way to get it up and running again and I can put up with a small steam leak up the chimney Attachments:
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