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Post by chris vine on Mar 28, 2019 21:48:08 GMT
having watched full size loco drivers for many hours (while crossing the Ukraine some years ago) I noticed that they always opened the steam valve a little, then whacked it fully open once a flow had established through the injector (and out of the overflow).
The type of injector had a lever operated steam valve on the backhead. So they would lift it a little and wait for it to make the correct sound (after about a second) and the lift fully to open fully.
I have often found that this can help on small injectors if they don't want to play. You establish a flow through the overflow pipe and then put on full steam. If you put on full steam at the start, they can fail to pick up and you just get steam from the overflow.
I shall now expect Roger to work out why this is! Maybe he already has?!?
Chris.
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don9f
Statesman
Les Warnett 9F, Martin Evans “Jinty”, a part built “Austin 7” and now a part built Springbok B1.
Posts: 960
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Post by don9f on Mar 28, 2019 22:00:23 GMT
That’s how I would use an injector as well....but not in the Ukraine!
Cheers Don
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JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,907
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Post by JonL on Mar 28, 2019 22:02:18 GMT
It sounds finicky....
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Post by Roger on Mar 28, 2019 23:22:19 GMT
having watched full size loco drivers for many hours (while crossing the Ukraine some years ago) I noticed that they always opened the steam valve a little, then whacked it fully open once a flow had established through the injector (and out of the overflow). The type of injector had a lever operated steam valve on the backhead. So they would lift it a little and wait for it to make the correct sound (after about a second) and the lift fully to open fully. I have often found that this can help on small injectors if they don't want to play. You establish a flow through the overflow pipe and then put on full steam. If you put on full steam at the start, they can fail to pick up and you just get steam from the overflow. I shall now expect Roger to work out why this is! Maybe he already has?!? Chris. Hi Chris, That's interesting. There are a few possible reasons I can think of for this. The first one is that if you can get the ejector part to lift the water with very little steam, you're not heating the injector unnecessarily. You could also argue that there's no point in it being flat out for a time when there's no water in the injector yet. There won't be enough momentum to overcome boiler pressure until the steam valve is opened up more, so that part seems fairly obvious. Another possibility is that the design is poor, and the ejector simply won't work if the steam pressure is too high. That doesn't matter once the flow has been established.
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Post by terrier060 on Mar 28, 2019 23:42:49 GMT
If I remember my physics it's all to do with latent heat, therefore the colder the water, theoretically the better they will work. But they need water first then steam. Ed
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Post by delaplume on Mar 29, 2019 2:07:22 GMT
Hello everyone,
Just remembering our basic fundamentals, here I quote from the Black Book}----
1) "The change from pressure energy to velocity energy is brought about in the steam cone..."
2) "The Combining cone effects the complete combination of steam and water into a solid jet by the condensation of the steam and the transference of its' energy to the water."
3) "The function of the delivery cone is to convert the velocity energy of the combined jet into pressure energy"..
It also notes that}---- "The temperature of the water is usually increased by 100 deg.F in passing through the injector"...
In point 2) the greater the temp. difference ---the better the condensation effect, hence the need to keep the supply water temp as low as possible...
When on the footplate I would}--- a) Open the water valve fully and check the overflow was discharging fully...
b) "Crack-open" the steam valve by 1 turn to establish the initial operation, whilst also listening for the distinctive singing sound of the water flowing through the delivery pipe, and checking that the overflow had now stopped completely, then..
c) Open the steam valve another 3 or 4 turns to give a full-volume flow....
Any excess water in the overflow was controlled by careful use of the water valve....
As the GWR 8X and 10X injectors had hinged flaps on the combining cone they would automatically re-start if "Knocked-off" for any reason....
Hope that helps ??
Alan
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Post by suctionhose on Mar 29, 2019 6:21:33 GMT
Roger, I suspect the reason most model injectors are configured in the same way is 'Gravity'. A ball that naturally seats and an overflow that naturally drains... Full size injectors come in many configurations - one marvels at the engineers behind them - but for the bare essentials for reliable model usage, they are what they've become. The function of the ball is to help automatic restarting by destroying the vacuum, equalizing pressures between chambers and allowing the energy exchange to start over. A fellow at our club who has made many injectors to the LL words and music, made one with no ball. It worked well except for needing help to restart if it knocked off. I remember meeting Charles Dockstader at his club in LA in 1985. His loco had a miniature injector in the cab up on the boiler with the lever and moving steam cone... twas perfect in every sense! I'm just saying other combinations are possible and people do experiment a bit. Depends on the individuals motives. In the context of a whole working model, the injector is just one small piece. I couldn't justify spending a year or two inventing a new way (although I may make a scale body injector for my 1880 TE using Brown's cartridge method) Hi Ross, I was coming to the same conclusion, ie that gravity and a convenient layout were probably the reasons for them being how they are. I'm not sure that's the right explanation for the ball valve though. My understanding is that it would restart without a ball, but may not continue delivery because of the air drawn in from the gap in the combining cone. Hopefully a few experiments will discover what you can and can't do. I'm hoping to work quickly through the injector design, after all, most of the hard work has already been done, ie the cone throat dimensions, angles and gaps. I find this sort of thing fascinating, so I don't mind spending a bit of time figuring it out for myself. I'm really pleased you are prepared to fiddle and have no doubt that all of us will gain some knowledge for your trouble! But please don't let it stop you commissioning the Speedy as a finished product! I really have very little to offer the discussion - as I said, it is but a single part of a whole machine (and 4 years into my Ploughing Engine I have not yet made any of the 'steam engine'; just the machinery to be driven by it!). Re: The Ball. There must be a reason in the first place to connect that combining cone gap with the overflow. That you need a ball to close the passage once started would suggest it has something to do the establishing the state of operation. If the ball was simply "to stop air entrainment" why have the passage at all? It must be associated with establishment / restarting / ... Marvellous stuff 'Steam'! There's two sides to it (I have come to understand). The pressure / cylinder / valve gear / mechanical work aspect (which has captivated me for decades) and the 'Process Heat' side of things which is essentially energy conversion. Less captivating for me, but in my work on the engineering team at a Plant that uses 'Process Heat' I have learned to appreciate steam as a medium like no other to transfer energy from place to place as well. The injector is a bit of both with Kinetic Energy from Mass Flow and Heat Energy from Steam. I just have the greatest admiration for those clear thinkers that come up these principles. (BTW my loco's have been wholly injector dependant for as long as I can remember with the exception of smaller models eg Speedy size, that really benefit from having the baseline supply from a pump and an injector to top up, arrest a Safety Valve from lifting and generally trim steam production on the run. Sorry. Not much design in the above. Please forge on and see what happens!
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baldric
E-xcellent poster
Posts: 208
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Post by baldric on Mar 29, 2019 7:33:28 GMT
My experience of full size injectors is that they can vary considerably, properly working GWR one, normally open the water valve, if you know where it works best just open beyond there, then open the steam valve a couple of turns, trim water as needed. GWR lifting injectors (on railmotor) water valve always open, just crack the steam to lift water to injector, then open fully, no need to adjust water if working fine. Other injectors may work as above, some will only work if crack the steam, count to 5, then open, some then need the water reduced until they blow out, then open water slightly again. It's all part of the fun of getting on a new engine! One important fact is to listen to the injector, at night or in tunnels you probably won't be able to see the overflow!
Then you get to use exhaust injectors, that is a whole new game with water valve for on/off only, 2 steam valves (on GWR) and a moveable cone to adjust the water with.
As you can see, there is no single way of working an injector, I would expect a similar variance with models.
Baldric.
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Post by flyingfox on Mar 29, 2019 8:06:36 GMT
Greetings,firstly congratulations, Roger, in opening this most interesting of topics. referring to the steam valve opening mentioning full sized practice, in 71/4 gauge I have had most success using the "Pull open" valve, as per the late Jim Ewings, where the valve has no thread and just pulls open. I have modernized it with PTFE seat & valve spindle packing. This picks up straight away, and although I usually put the water on first, it still picks up straight away if I forget the "Water first" rule. Perhaps the big railway had as much trouble as some still do with injectors. Regards Brian
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Post by Roger on Mar 29, 2019 8:50:59 GMT
I'm really pleased you are prepared to fiddle and have no doubt that all of us will gain some knowledge for your trouble! But please don't let it stop you commissioning the Speedy as a finished product! I really have very little to offer the discussion - as I said, it is but a single part of a whole machine (and 4 years into my Ploughing Engine I have not yet made any of the 'steam engine'; just the machinery to be driven by it!). Re: The Ball. There must be a reason in the first place to connect that combining cone gap with the overflow. That you need a ball to close the passage once started would suggest it has something to do the establishing the state of operation. If the ball was simply "to stop air entrainment" why have the passage at all? It must be associated with establishment / restarting / ... Marvellous stuff 'Steam'! There's two sides to it (I have come to understand). The pressure / cylinder / valve gear / mechanical work aspect (which has captivated me for decades) and the 'Process Heat' side of things which is essentially energy conversion. Less captivating for me, but in my work on the engineering team at a Plant that uses 'Process Heat' I have learned to appreciate steam as a medium like no other to transfer energy from place to place as well. The injector is a bit of both with Kinetic Energy from Mass Flow and Heat Energy from Steam. I just have the greatest admiration for those clear thinkers that come up these principles. (BTW my loco's have been wholly injector dependant for as long as I can remember with the exception of smaller models eg Speedy size, that really benefit from having the baseline supply from a pump and an injector to top up, arrest a Safety Valve from lifting and generally trim steam production on the run. Sorry. Not much design in the above. Please forge on and see what happens! Hi Ross, The gap and the channel to the overflow provide several things. Firstly, the position of the gap provides a throat diameter at that point which is in the correct proportion to the Steam cone throat to make an ejector so it will lift water. Secondly, while it's starting, the combined volume of air, water and uncondensed steam won't fit through the Combining cone. Without the gap providing somewhere for the excess to go, it would vent back into the water tank and never start. There's no need to connect the gap to the gap between the Mixing and Delivery cones, it's just done that way for convenience so you can have one overflow pipe. All that's required is for the excess volume at the gap to exit the injector for it to start. The ball then stops air being drawn into the column of water, reducing its density and giving it a milky colour. It may still deliver water, but not under the more extreme ends of the design envelope. Since air is going to be drawn into the Delivery cone too, there's a case for having a non-return valve on that section too. This is why I'm of the opinion that it may well be that you only need one valve on the outlet, and that closing will serve the same purpose for both places where we don't want air to be drawn into the system. It's a fascinating subject, and one that's taken a lot to get my head round.
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jma1009
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Post by jma1009 on Mar 30, 2019 20:55:36 GMT
Reviewing the last few days, you don't actually need an overflow on the gap between the end of the combining cone and the start of the delivery cone. I did a couple like this. There is a bit of a drop in performance, and they are not so easy to start or restart. Separating the 2 overflows is not something I've done, though I was sent an injector made by Eric(?) Cook in the West Country which had this feature. I can see the logic of this. From what I have gleaned, quite a few fullsize injectors were quite temperamental. Some of the Southern Railway injectors from the constituent companies were not easy to operate. This is based principally on an early book I have of the Bluebell Railway when the vagaries of their loco collection (as was then) was discussed in some detail from a driver and fireman's perspective, and Harold Holcroft's 'Locomotive Adventure' Vol 2. If my memory is correct the Talyllyn Railway standardised on Penberthy injectors, but on the Ffestiniog Railway 'Merddin Emrys' still has it's original 'Sirius' injectors of 1879 vintage from Holden and Brooke www.merddin-emrys.co.uk/Pages/Injectors/merddin_and_the_injectors.htmlNote that in the 'Sirius' design in the above link there is no gap between end of the combining cone and the delivery cone, and the steam cone is 'adjustable' in and out of the start of the combining cone. Cheers, Julian
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jma1009
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Post by jma1009 on Mar 30, 2019 21:13:57 GMT
The severest test of a miniature injector is to turn the steam on then the water. Or turn the water off then on again whilst the steam is still on.
I've never fitted any that don't meet this rigorous test.
Roger's own approach to design should result in this unusual characteristic. The shorter operating pressure range of miniature locomotives assists with this when compared to fullsize.
Cheers,
Julian
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Post by Roger on Mar 30, 2019 22:32:27 GMT
Reviewing the last few days, you don't actually need an overflow on the gap between the end of the combining cone and the start of the delivery cone. I did a couple like this. There is a bit of a drop in performance, and they are not so easy to start or restart. Separating the 2 overflows is not something I've done, though I was sent an injector made by Eric(?) Cook in the West Country which had this feature. I can see the logic of this. From what I have gleaned, quite a few fullsize injectors were quite temperamental. Some of the Southern Railway injectors from the constituent companies were not easy to operate. This is based principally on an early book I have of the Bluebell Railway when the vagaries of their loco collection (as was then) was discussed in some detail from a driver and fireman's perspective, and Harold Holcroft's 'Locomotive Adventure' Vol 2. If my memory is correct the Talyllyn Railway standardised on Penberthy injectors, but on the Ffestiniog Railway 'Merddin Emrys' still has it's original 'Sirius' injectors of 1879 vintage from Holden and Brooke www.merddin-emrys.co.uk/Pages/Injectors/merddin_and_the_injectors.htmlNote that in the 'Sirius' design in the above link there is no gap between end of the combining cone and the delivery cone, and the steam cone is 'adjustable' in and out of the start of the combining cone. Cheers, Julian Hi Julian, That's an interesting design, especially the fact that there's no overflow gap in front of the Delivery cone. That's probably why they have to allow the user control the input regulation and steam supply to get it to start. I can see why it's not a good arrangement, there's nowhere for the excess air, water and uncondensed steam to go in that region. Unless you get the conditions just right while it's overflowing at the Combining cone, it's not going to want to start.
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Post by steamer5 on Mar 30, 2019 23:32:43 GMT
Hi Julian, Your quote above...
“The severest test of a miniature injector is to turn the steam on then the water. Or turn the water off then on again whilst the steam is still on. “
The gent in our club who was the guru on building injectors ran lifting injectors on his loco, both are about level with the top of the side tanks, which means every time the injector is required it is steam first, these gave little or no trouble despite the number of different drivers in a running session! It is a real pity that he didn’t pass on his knowledge on how he made this happen! I’ve saw him test a couple of his designs & from memory they would lift a couple of feet it not more! I did ask what he did but only got a smile in response!
Have you got any idea what he may have done to achieve this sort of lift?
Talking with Dad recently, he remembers taking 1/2 a dozen of these injectors to one of the convention in the lower South Island & as soon as guys found out he had these for sale on behalf they were snapped up very quickly! He reckoned he could of sold 3 or 4 time the number!
Cheers Kerrin
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jma1009
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Post by jma1009 on Mar 30, 2019 23:47:40 GMT
Hi Kerrin,
There may be various aspects to all this.
The 'secret' Ted Linden chamfer on the second half of the combining cone entrance, and getting the 2 halves of the combining cone correctly proportioned as per Roger's analysis?
I have tentatively suggested via examination of one Gordon Chiverton injector innards that the 'secret' Ted Linden chamfer is not the magic solution, as none was present other than a 2 thou or so chamfer.
A self auto re-starting lifting injector does require quite a bit of attention to the simple ejector requirements before the injector picks up and starts to feed. Basically you split the injector into 2 halves and see if the first half meets this requirement.
You also have to get the 2 halves of the combining cone to work properly. Get the wrong angle on the combining cone internal taper and you are doomed to failure as are a certain brand of UK commercial cheap products as correspondents will know.
Cheers,
Julian
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Post by steamer5 on Mar 31, 2019 0:07:13 GMT
Hi Julian, Thanks for the reply. Jerry was quite cagey about what he did on injector making! We only have a couple of guys left in the club who may have been privy to some more details. Next time I run into one of them I’ll make a point of asking if they know any details. I think I’ve read, likely misinterpreted, that the Linden chamfer is as you describe, just enuff to brake the edge or not a lot more, which from your comment you are sure on either which is quite understandable as measuring a charmer of those sizes would be a bit tricky to say the least!
The injectors on my loco have proved in the past to be self starting......they are below foot plate. & I leave the water on as getting to the valves on a tender loco isn’t easy...by way of having them on coming to a halt with a little over keen brake application with the resultant sloshing of boiler water prevent injection they blow steam then restart, which is a great bonus!
Thanks for the further insights
Cheers Kerrin
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Post by Roger on Mar 31, 2019 8:56:33 GMT
"Jerry was quite cagey about what he did on injector making! We only have a couple of guys left in the club who may have been privy to some more details. " Hi Kerrin, This is reason there's so much mystique in injector design and manufacture, and frankly I find it infuriating. You can bet that there was no real 'secret', he just made them well enough to a design of good proportions. We've explored those proportions, and it all looks pretty simple to me. In my opinion, the accuracy of making and fitting the parts in the body are where most of the problems lie for potential builders. Most Model Engineers simply aren't used to making things where the accuracy is as important. The physics only works when the geometry is good enough. You can have an excellent design, but if it's not made well enough, it's not going to perform well or at all. Openness and sharing tips (secrets) is absolutely essential because otherwise we lose too much when those hoarders take their knowledge to the grave. I suppose people get some kind or kick or kudos when they have some useful nugget of information that they won't disclose. I find it rather depressing when there's no commercial reason for it.
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Post by steamer5 on Mar 31, 2019 10:00:21 GMT
Hi Roger, I'm sure you have us well on the way! Given the level of ability's on this forum once the "What" is sorted the "how" will be easy! Adam has made a nice scale injector which looks like its working great so between the 2 of you im sure more of us will be able to make them.....I might even get one to work!
Cheers Kerrin
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JonL
Elder Statesman
WWSME (Wiltshire)
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Post by JonL on Mar 31, 2019 14:10:56 GMT
Openness and sharing tips (secrets) is absolutely essential because otherwise we lose too much when those hoarders take their knowledge to the grave. I suppose people get some kind or kick or kudos when they have some useful nugget of information that they won't disclose. I find it rather depressing when there's no commercial reason for it. And this is why I am so indebted to my model engineering society. Especially the director, a chap called Des Clarke, who has made it his complete mission to teach me something at every opportunity. I remember trying to shorten a propshaft for a car build I was doing, and an experienced welder was looking over my shoulder and laughing, telling me I was doing it wrong and wouldn't tell me why. He just kept saying "you'll find out". In the end I got uncharacteristically angry and called him out on it. It turned out I was cutting off the wrong end, and luckily stopped before I made the cut. He was going to let me cut away and ruin the job. Unbelievable.
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jma1009
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Post by jma1009 on Mar 31, 2019 19:10:04 GMT
Just a few further comments on the 'secret' Ted Linden 'chamfer' on the entrance to the second half of the combining cone...
One particular commercial product clearly has the 2 halves of the combining cone finished on it's internal taper once the 2 halves are pressed into the body, and I have observed a burr created as a result. If you add a chamfer, then I suppose this burr does not occur.
The Ted Linden 'chamfer' is about 10 thou, and this was copied by Arthur Grimmett. That on the only Gordon Chiverton injector I have with the 2 halves of the combining cone pressed out has a chamfer of some 2 thou only.
With a good light and keen eyesight you can see the chamfer on Linden and Grimmett injectors if you look carefully down the check valve seat. I have also pressed out quite a few combining cones on Arthur Grimmett injectors over the years plus inherited a lot of odds and sods of injectors and parts from Arthur, so am quite sure of all this. Only some of Arthur's last 2 batches worked on test because the brass castings for the bodies were porous in many cases. He had a large tin box of rejects from these last 2 batches - all finished and complete with cones fitted. (These faulty brass body castings were provided by Don Young!)
To pick up on Roger's point about being 'depressed' that 'secrets are not shared', usually when I start talking about injectors, people's eyes glaze over and they simply are not interested. When you mention drilling a No.75 drill say 7/16" deep accurately they just switch off! Hardly any Model Engineers use a sensitive lever operated tailstock and accurate pin drill chucks for small drills.
Actually, all the info was published by 1977 in ME and the SMEE journal, assuming the paper I have by Jim Ewins was in one of the SMEE Journals missing from my collection. You just have to piece it all together like a big jigsaw, and discard all the irrelevant stuff.
I think there is a parallel here with miniature pressure gauges - no one makes their own generally. If you start talking about making your own working miniature pressure gauges you are considered a 'nutter' by most!
Cheers,
Julian
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