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Member postings for Bob Corrie

Here is a list of all the postings Bob Corrie has made in our forums. Click on a thread name to jump to the thread.

Thread: Mangled valve ports - help!
03/12/2010 16:34:09
Thanks very much guys, that is really helpful. I guessed that I wouldn;t be the first with this problem and your thoughts and the links to the TE thread are most encouraging.
 
Bob
02/12/2010 16:21:01
 My apologies if this should go somewhere else or the answer is obvious but I’m a newbie to both this forum and model engineering and would appreciate some advice from those who have been round the block a few times more than I have.
I have acquired a part built 5” gauge locomotive (a Firefly 45XX GW prairie design) to complete as my first serious project. On inspection I have fund that the slide valve ports in the CI cylinder castings have been mangled (probably attempting to drill the steam passages)  such that there is not enough material left to give the required lap. Being a tad reluctant to fork out around £250 for new castings, I wonder if I could repair them.

Two approaches occur to me: 1, to silver solder/braze up the ports and machine them again (but will the solder  “take” in the ports, will the casting suffer with the heating and will silver solder provide a hard enough edge for the ports?) or 2, to mill off say 3mm from the valve face and then sandwich a 3mm plate between the cylinder block and the valve steam chest to form the valve face with new valve ports milled in plate. It occurs to me that making the  steam passages could be simplified by this if I milled shallow cavities beneath or in the underside of the plate to meet very short drilled passages into the ends of the cylinder bores.

What do you think, is this a goer? If so, what material would you use for  the plate with a GM valve? Or are there any better ideas? Any advice you can give is most welcome!
 
Bob
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