61962
Seasoned Member
Posts: 129 
|
Post by 61962 on Oct 7, 2020 8:16:39 GMT
Hi Pete,
I'm pretty certain that by 1939 4472 will have had poppet valve cylinder drain valves as your photograph from 60007. Originally all locos had the plug cock type, but by 1935, possibly starting with the A4 when new, the poppet valve type were fitted to locos as they went through overhaul. The bit above the drain valve is a cylinder pressure relief valve originally set at boiler pressure, but later at 10 psi above. It is simply a poppet valve with an exposed spring contained by the two long studs. It is 2 1/2 inces above the drain valve centre.
I've never understood why these relief valves were retained after the cylinder end relief valves were introduced in the late twenties, but they were all kept right to the end.
Eddie
|
|
|
|
Post by Deleted on Oct 7, 2020 9:31:07 GMT
Thank you, Eddie, yes I've learnt a lot about these since first becoming aware of their existence yesterday. As you state I know that they were kept for some reason long after the cylinder cover relief valves were added, in fact, she still had them well into preservation. PaulT kindly shared a drawing of the P2 on FB yesterday from which I can work out scale measurements, that and the various photos that I now have should enable me to make up something that looks ok. I drew up a rough sketch last night of what I plan to do, interestingly, it looks like I can use the Polly commercial draincocks for the actual drain cock itself as they look very close, I have already given some thought as to how to blend them into the relief valve body above. Thank you for the 2 1/2" dimension, that will help with scaling too.
Kind regards
Pete
|
|
|
|
Post by Deleted on Oct 8, 2020 19:37:50 GMT
|
|
|
|
Post by Deleted on Oct 13, 2020 14:39:57 GMT
Today's blog update covers the draincock and relief valve assemblies, lots of fiddly work in this one. I have some finishing touches still to do but I'll take care of those on the final assembly after I have painted the cylinders and fitted them to the frames.  4472flyingscotsman.co.uk/draincocks-and-relief-valves/Pete |
|
timb
Statesman
Posts: 512
|
Post by timb on Oct 13, 2020 15:03:25 GMT
Fantastic Gg!
Tim
|
|
mbrown
Elder Statesman
Posts: 1,796
|
Post by mbrown on Oct 13, 2020 16:41:50 GMT
Brilliant Pete. I love turning my hand to fiddly fittings - but these are a lot more fiddly than most of my efforts in 2.5"g!
Malcolm
|
|
|
|
Post by Deleted on Oct 13, 2020 16:52:54 GMT
Brilliant Pete. I love turning my hand to fiddly fittings - but these are a lot more fiddly than most of my efforts in 2.5"g! Malcolm Thanks, Tim / Malcolm... the picture doesn't really show how small these things really are... as a reference, the cylinder studs are 6BA... I must be mad...  Pete |
|
|
|
Post by Deleted on Oct 13, 2020 17:03:22 GMT
This is the picture that I was referring too, which to me shows the valve rods were deliberately bent over to force the valve closed permanently. If this had been an accidental damage scenario the front plate would have been past the bend, it's clear to see how much the spring has been compressed here.  Perhaps an insight into what the fitters got up too during the A1/3's service career... IIRC this photo is circa 1938 and if Eddie is correct about the cover relief valves being fitted '35' then at some point in the following 3 years it was decided to permanently block the draincock relief valves. Or at least that's my current way of thinking. Pete |
|
|
|
Post by Deleted on Oct 16, 2020 20:31:42 GMT
|
|
|
|
Post by Deleted on Oct 22, 2020 18:41:48 GMT
Evening all, here's part 1 of the blog entry covering the draincock fitting. The second part which will cover the outside cylinders should be ready by end of next week. I have included another video showing the Bowden cable route and working.  4472flyingscotsman.co.uk/draincock-linkage-part-1/Pete |
|
|
|
Post by Deleted on Nov 1, 2020 17:20:09 GMT
|
|
mbrown
Elder Statesman
Posts: 1,796
|
Post by mbrown on Nov 1, 2020 18:53:37 GMT
That is looking stunning Pete!
Malcolm
|
|
|
|
Post by Deleted on Nov 1, 2020 19:11:01 GMT
That is looking stunning Pete! Malcolm Thank you sir.... |
|
|
|
Post by Jim on Nov 1, 2020 20:50:43 GMT
That is looking stunning Pete! Malcolm I agree Malcolm. To be honest I have never seen a more beautifully accurate model than this. Every detail faithfully and accurately replicated. It's a world class model.
Jim
|
|
|
|
Post by Deleted on Nov 1, 2020 21:11:56 GMT
That's very kind of you Jim but trust me when I say it has its faults...for example the draincocks open the wrong direction...I did point this out though so not trying to hide anything. Hopefully in time I'll iron out most but life is short and I need to get it finished.... Kind regards Pete |
|
mbrown
Elder Statesman
Posts: 1,796
|
Post by mbrown on Nov 1, 2020 22:01:20 GMT
Is the orientation of the draincocks "wrong" because the levers on the cocks are back to front, or is it in relation to the movement of the lever in the cab?
The former should be easy to fix...
But there is a precedent for everything. When the Talyllyn got No3 "Sir Haydn" back from overhaul a few years ago the draincocks worked "back to front" in terms of the position of the cab lever. It makes no difference except to confound drivers who had years of experience the old way!
Malcolm
|
|
|
|
Post by Deleted on Nov 1, 2020 22:18:57 GMT
Cab is correct..the issue is the direction the cocks open..my fault...I knew that they opened foreward and did the middle cylinder so. What I failed to realise was that the middle opens in reverse so that the outside cylibders open forward. To change it would involve a lot of work...pulleys would need repositioning, cables adjusted to suit and dissasembling the middle cross shaft. That's two many steps backwards for me, I'll live with the error instead
Pete
|
|
mbrown
Elder Statesman
Posts: 1,796
|
Post by mbrown on Nov 1, 2020 22:32:01 GMT
Can't you just position the levers on the opposite quarter of the valve stems? Or are they not fixed that way?
Malcolm
|
|
|
|
Post by Deleted on Nov 2, 2020 1:22:42 GMT
Can't you just position the levers on the opposite quarter of the valve stems? Or are they not fixed that way? Malcolm Affraid not, don't forget they have the extra (handed) relief valve bodies attached and that one of these has an odd thread?. Cheers Pete |
|
|
|
Post by Deleted on Nov 2, 2020 1:55:30 GMT
Hi Malcolm
Sorry, I've just realised that I haven't really explained myself properly. The issue isn't with the draincocks themselves, I have already changed the valves as they were set to open correctly. The issue is that I hadn't noted that the middle cylinder should open in reverse, this is because the linkage connecting middle to outside cylinders reverses the direction of movement. The connecting arm on the middle cross shaft drops below its axis whereas the outside cylinder cross shaft arm pivots above the shaft and thus changes the direction of the throw.
Pete
|
|
