smallbrother
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Post by smallbrother on Feb 24, 2021 11:46:42 GMT
Here are the existing bits:- Pete.
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smallbrother
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Post by smallbrother on Feb 24, 2021 11:52:45 GMT
I have ordered from Polly the drawing and springs for one of Gordon Smith's designs.
The design is for a much shorter valve which of course does not need to stick out through a saddle tank. Thus the spring will be much shorter than the existing.
I will make a new guide which will account for the shorter spring and have a proper cup to accommodate the ball. The existing guide just has a concave profile and I wonder if this is why the ball does not return to its seat as neatly as it should.
Anyway, I think it is worth a try. The valves perform OK apart from a decent closure and i don't want to keep giving them a tap with the shovel.
Pete.
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neil
Active Member
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Post by neil on Feb 24, 2021 12:24:36 GMT
The Grodon Smith saftey valves are a very good design, he did a very good item, in Enginering in miniture in Feb 2001, explaining his experiemnts and design.
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smallbrother
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Post by smallbrother on Feb 24, 2021 14:32:04 GMT
The Grodon Smith saftey valves are a very good design, he did a very good item, in Enginering in miniture in Feb 2001, explaining his experiemnts and design. Someone has very kindly got me a copy. Pete.
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chrisb
Part of the e-furniture
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Post by chrisb on Feb 24, 2021 19:15:48 GMT
You could always use the old valve bodies as an extension and adapt them so the Gordon Smith valves screw in on top of them?
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smallbrother
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Post by smallbrother on Feb 24, 2021 19:52:43 GMT
You could always use the old valve bodies as an extension and adapt them so the Gordon Smith valves screw in on top of them? That's Plan B! I don't know why the original builder didn't do that to start with. Pete.
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barlowworks
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Post by barlowworks on Feb 24, 2021 19:57:38 GMT
Love the Welsh ruler Pete. 😉
Mike
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smallbrother
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Post by smallbrother on Mar 5, 2021 20:59:11 GMT
Well I have made new guides and obtained new springs from Polly, all pretty much as specified on one of the Gordon Smith drawings. I chose one which is of similar proportions to the originals on the loco. The guides though are much longer than the design as the original valves are tall enough to clear the saddle tank.
Just need to steam up and see if it all does the trick.
Hopefully tomorrow.
Pete.
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Post by ejparrott on Mar 6, 2021 9:06:19 GMT
I modified one of Royal Scot safety vslves in a similar way. The original is Martin Evans awful Highlander design and incapable of performing satisfactorily, I had to use a longer spindle with an extended larger diameter at the bottom to use the standard GS spring from Polly. One valve on its own is now sufficient, just as well, as the second one can't be removed thanks to ME's stupid design having 5/8" of thread sticking out the bottom of the bush, and it's all scaled up and stuck solid.
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smallbrother
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Post by smallbrother on Mar 6, 2021 9:15:31 GMT
I modified one of Royal Scot safety vslves in a similar way. The original is Martin Evans awful Highlander design and incapable of performing satisfactorily, I had to use a longer spindle with an extended larger diameter at the bottom to use the standard GS spring from Polly. One valve on its own is now sufficient, just as well, as the second one can't be removed thanks to ME's stupid design having 5/8" of thread sticking out the bottom of the bush, and it's all scaled up and stuck solid. That's encouraging Ed. Was hoping to steam up today but my knee has siezed up and I'm on crutches and Cocodamol for a day or two. The joys of arthritis. Pete.
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smallbrother
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Post by smallbrother on Mar 7, 2021 9:18:18 GMT
Well the tablets worked well and I managed a steam up.
One valve worked very well but the other is still troublesome and they don't pass enough steam for a test.
The photo at the top shows there is a base to these valves, and the troublesome one has its base stuck in the boiler bush where I cannot get at it. I will get the saddletank off (some work needed on it anyway) and get the base off. I wouldn't be surprised if there is some muck in there somewhere. Before I started on any new parts it would pass the accumulation test so a bit of a puzzle to solve.
The existing adjusters have 8 small holes - the G Smith design has 6 larger holes which without going through the maths would be a greater area I am sure. That's another improvement I can try.
Pete.
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timb
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Post by timb on Mar 7, 2021 12:22:22 GMT
Glad the tablets are working Pete, cant be easy with this cold spell!!
Tim
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Post by coniston on Mar 7, 2021 23:18:10 GMT
I'm sure you'll get there Pete, glad the tablets worked and you were able to get a steaming in. I am sure the holes in the adjuster are critical from reading some of the articles Gordon wrote, if not sufficient it causes back pressure above the valve which prevents the ball lifting sufficiently to clear the steam. Good luck
Chris
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smallbrother
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Post by smallbrother on Mar 8, 2021 8:55:32 GMT
I'm sure you'll get there Pete, glad the tablets worked and you were able to get a steaming in. I am sure the holes in the adjuster are critical from reading some of the articles Gordon wrote, if not sufficient it causes back pressure above the valve which prevents the ball lifting sufficiently to clear the steam. Good luck Chris Thanks Chris, Frustratingly these same adjusters passed sufficient steam before I fitted the new guides and springs. The problem was they wouldn't close very well and often needed a tap with the shovel. The spring sits just under the adjuster and I can make a spacer to ensure the spring doesn't block up any of the hole area. I have just ordered a die and some brass bar to make new adjusters as well. Hoping to get the saddle tank off today - bit of a procedure as the cab will have to come off too - loads of 6BA bolts in awkward corners. Quite a few options to explore before I throw the towel in...... Pete.
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Post by suctionhose on Mar 9, 2021 10:57:20 GMT
Hello Pete, I hesitate to put this info here because Gordon Smith is the preferred guru in UK. This is an article I had published in the local AME Magazine in 1991 following experiments in the shed to establish "a way to succeed" (with pop valves). The salient thing is that there must be an area - many ways to provide it - for escaping steam to act upon to push the valve open. This assists with the the accumulation issue but also provides an equilibrium point whereby, once the pressure drops a little and equilibrium is lost, the valve snaps shut. It may be as simpler as counter boring the seat. OR I have successfully silver soldered a ring onto the seat, down in the hole and finally machined is the manner described. All this is very difficult down in a hole and so much easier if the seat screws up into the body after machining. Perhaps an alternative set of words will help the penny drop! BTW, the area of the holes in the top should be 150% of the valve bore. Once the steam passes the seat it expands significantly and you do want avoid backpressure in the valve body itself. Back pressure causes the valve to resonate i.e. buzz, fart, hammer: whatever term you prefer but that is the cause without shadow of doubt. I have concluded this by experiment.
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smallbrother
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Post by smallbrother on Mar 9, 2021 12:07:11 GMT
Hello Pete, I hesitate to put this info here because Gordon Smith is the preferred guru in UK. This is an article I had published in the local AME Magazine in 1991 following experiments in the shed to establish "a way to succeed" (with pop valves). The salient thing is that there must be an area - many ways to provide it - for escaping steam to act upon to push the valve open. This assists with the the accumulation issue but also provides an equilibrium point whereby, once the pressure drops a little and equilibrium is lost, the valve snaps shut. It may be as simpler as counter boring the seat. OR I have successfully silver soldered a ring onto the seat, down in the hole and finally machined is the manner described. All this is very difficult down in a hole and so much easier if the seat screws up into the body after machining. Perhaps an alternative set of words will help the penny drop! BTW, the area of the holes in the top should be 150% of the valve bore. Once the steam passes the seat it expands significantly and you do want avoid backpressure in the valve body itself. Back pressure causes the valve to resonate i.e. buzz, fart, hammer: whatever term you prefer but that is the cause without shadow of doubt. I have concluded this by experiment. Many thanks for that. With types (b) and (d), what is the object below the guide in the bore? Pete.
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uuu
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Post by uuu on Mar 9, 2021 13:03:39 GMT
I think it's a three or four-sided winged thing, to keep the jigger central..
Wilf
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johnd
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Post by johnd on Mar 9, 2021 13:12:48 GMT
Pete, Been following this post with interest as i have used three sets of Gordon valves with great success. Had a number of conversations with him over the years and a couple of general points he made at the time may be of interest. First the exit holes in the adjuster should have a generous chamfer on both sides. Second is that the spring should be positively centred at both ends. He was of the opinion that both of the above small points did make a noticeable difference to the valves operation. Just thought these points may be of some interest. Will be watching your progress, good luck.
Daggers
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smallbrother
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Post by smallbrother on Mar 9, 2021 15:23:22 GMT
Pete, Been following this post with interest as i have used three sets of Gordon valves with great success. Had a number of conversations with him over the years and a couple of general points he made at the time may be of interest. First the exit holes in the adjuster should have a generous chamfer on both sides. Second is that the spring should be positively centred at both ends. He was of the opinion that both of the above small points did make a noticeable difference to the valves operation. Just thought these points may be of some interest. Will be watching your progress, good luck. Daggers I am making some spacers to keep the springs off the adjusters. These spacers will hold the springs and keep things central and will be cone shaped to give the steam full access to the holes. I have made the holes as large as I dare, there is very little material in between them so not sure opening them out with chamfers is a great idea. Not forgetting that they have passed steam tests previously so the main problem must lie elsewhere. Hopefully they will do exactly what you suggest. Normally I would get very frustrated with this project but as there is no chance to steam up at the club it is a great opportunity to learn, and fingers crossed, find a solution. Pete.
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mbrown
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Post by mbrown on Mar 9, 2021 16:00:46 GMT
Pete,
This is an intuitive rather than an expert response, but it strikes me that if the valve is opening more efficiently (as it probably is with any pop action) the amount of steam needing to be released in a given time through the holes in the cap will be greater, necessitating a greater area. So the comparison with the previous situation may not be wholly valid.
I think the chamfers around the holes are useful to ease the steam flow and I can't see that they would diminish the strength of the top cap significantly?
Malcolm
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