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Post by Roger on Feb 28, 2019 19:08:32 GMT
Roger Pity I am on holiday so cannot help with calls, values etc at present, but another point on re-reading one of your posts. Like you I disagree with the comment on surface friction loss being a factor. The loss factor you apply is based on the length to diameter ratio plus allowances for surface finish and Reynolds number. However you will need order of magnitude longer cone length to diameter to get any significant difference due to friction loss. Dave Hi Dave, I'm glad I'm not alone in thinking that, although mine was more of a gut feeling really. Bob Bramson says that for sizes larger than 25fl oz/min (710cc/min) or for pressures greater than 90 psi it's a key requirement that the mixing cone is longer than the mixing cone. Unfortunately he asserts this without any justification which is frustrating. To my way of thinking, the Mixing cone is the most invariable part of the design because its length is strictly determined by the throats of the Condensing cone, the Mixing cone, the angle and the gap. Since all of these can only be varied slightly, it's hard to see that it's the Mixing cone that's the critical one. To my way of thinking it's the length of the Condensing cone that causes a problem when it's too long. Maybe someone can suggest why that might be so? What would happen if you made the Condensing cone say three times as long as the Mixing cone? Would it still work, and if not, why not? Clearly, if the Condensing cone was made really long, the inlet diameter would be much bigger and so would the diameter of the diameter of the Steam cone outlet. Maybe it's this fact that drives the length of the Condensing cone?
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Post by andyhigham on Feb 28, 2019 19:51:19 GMT
I should imagine the surface friction might be a factor in the parts of the injector where laminar flow isn't occurring, I suspect most of the fluid moving through is quite turbulent? Also the rougher the finish the more the Reynolds number will come into things. I've not touched fluid dynamics in some time... Recent (last 20 years) thinking in motorcycle and car engine tuning leaves the inlet ports rough, like a coarse emery finish rather than polished as used to be the case.
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Post by Roger on Feb 28, 2019 20:03:49 GMT
What size injector to fit...
So far, all of the locomotives I've driven seem to have injectors that you would only leave on for perhaps 30 seconds, even when working really hard. To my way of thinking this is not how it should be. Filling the boiler quickly with cold water is counter productive in my opinion. I would have thought it would be better to leave the injector on for longer while filling more slowly so that the water can be heated gradually and evenly without chilling the boiler. Yes, you can just put it on for ten seconds or so at a time, but that's all a bit too frantic for my liking. In an ideal world, you would replace the water at the same rate it's used.
D.A.G Brown suggests that even a large 5" gauge locomotive requires no more than 10-12 fl oz/min (284-341cc/min), while Bob Bramson recommends anything from 16-38 fl oz/min (454-1080cc/min) depending on the size and type of 5" gauge locomotive!
Clearly there's a huge difference of opinion on the matter!
Even 284cc seems quite a lot of cold water to put into a 5" gauge 0-6-0 locomotive boiler in one minute.
I understand that a full size express locomotive might be expected to have one injector permanently left on? Perhaps someone can put be right on this? It certainly would make life a lot easier if the input of water was at least somewhere near the amount that's being used at full power.
For my particular build of an 0-6-0 tank locomotive, I would hope that it would be reasonably efficient with well designed valve gear courtesy of Don Ashton and plenty of superheating. This ought to minimise the amount of water used. Not all locomotives will necessarily be efficient, so perhaps this steers the suggestion towards larger sizes.
Another issue is that of reliability of course. The smaller the size, the more easily the injector will be affected by debris and scale. I imagine that adequate filtering and water treatment will be required for all injectors.
From a scale point of view, the smaller the injector, the easier it is to fit the necessary parts into the scale body. Another consideration is that of pipework, particularly water pipe and valve diameters. Again, scale designs impose limits on what size of pipe can be used.
1501 presents some particular issues relating to water feed to the injectors. Both injectors are fed from valves attached to the underside of the side tanks. One has a short run of pipe to the injector, but the other has a tortuous path leading forward, under the boiler and then back before turning 180 degrees to reach the RH injector. Clearly this is far from ideal! One thought is to use a much smaller injector on the RH side so that its water requirements are significantly less. The size of pipe can remain the same. If you need to fill the boiler more quickly for some reason, you can always turn them both on. Since I'll have the axle pump as a backup, it's not such an issue if there's a problem with one of the injectors.
My current thinking is to go for about 10 fl oz/min (284 cc/min) on the LH one and perhaps 8 fl oz/min (227 cc/min) or smaller on the RH one. Interestingly Bob Bramson states that the smallest practical size is 11 fl oz/min (313 cc/min) while D.A.G Brown describes one of 4 fl oz/min (114 cc/min). Another difference of opinion.
In the end I suppose it all comes down to what injectors are available or what you're prepared to make. Clearly it's easier to make larger injectors, and maybe frequently fiddling with the injectors appeals to you. A quick look at Polly Models shows you can only buy one down to 11 fl oz/min which pretty much decides what most locomotives are limited to. I can understand why someone wouldn't want to supply smaller ones if they are more exacting to make. Maybe you can buy smaller ones, I don't know.
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Post by simplyloco on Feb 28, 2019 20:17:57 GMT
I should imagine the surface friction might be a factor in the parts of the injector where laminar flow isn't occurring, I suspect most of the fluid moving through is quite turbulent? Also the rougher the finish the more the Reynolds number will come into things. I've not touched fluid dynamics in some time... Recent (last 20 years) thinking in motorcycle and car engine tuning leaves the inlet ports rough, like a coarse emery finish rather than polished as used to be the case. I used to polish my bike ports: do you mean to say that I wasted my time ? Knowing what I know now, (and have largely forgotten) is that turbulent flow probably provides a better mixing environment for the air fuel mixture. John PS. Little known fact regarding domestic water pipes. Build a new housing estate, and everyone soon complains about dirty mains water. This occurs because the original system was designed for a water flow of 6 feet a minute, thus facilitating a laminar flow layer which would skim over any accumulated sediment without disturbing it. Increase the flow beyond this, and voila!: turbulent flow increases and you get the brown stuff!
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Post by andyhigham on Feb 28, 2019 20:53:18 GMT
Recent (last 20 years) thinking in motorcycle and car engine tuning leaves the inlet ports rough, like a coarse emery finish rather than polished as used to be the case. I used to polish my bike ports: do you mean to say that I wasted my time ? Knowing what I know now, (and have largely forgotten) is that turbulent flow probably provides a better mixing environment for the air fuel mixture. John PS. Little known fact regarding domestic water pipes. Build a new housing estate, and everyone soon complains about dirty mains water. This occurs because the original system was designed for a water flow of 6 feet a minute, thus facilitating a laminar flow layer which would skim over any accumulated sediment without disturbing it. Increase the flow beyond this, and voila!: turbulent flow increases and you get the brown stuff! It may be the same principle as the dimples on a golf ball helps it to pass through the air
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Post by simplyloco on Feb 28, 2019 21:10:47 GMT
I used to polish my bike ports: do you mean to say that I wasted my time ? Knowing what I know now, (and have largely forgotten) is that turbulent flow probably provides a better mixing environment for the air fuel mixture. John PS. Little known fact regarding domestic water pipes. Build a new housing estate, and everyone soon complains about dirty mains water. This occurs because the original system was designed for a water flow of 6 feet a minute, thus facilitating a laminar flow layer which would skim over any accumulated sediment without disturbing it. Increase the flow beyond this, and voila!: turbulent flow increases and you get the brown stuff! It may be the same principle as the dimples on a golf ball helps it to pass through the air Correct. The golf ball rotates backwards and the air speed on top is increased. The increase in speed has to come from somewhere, this reduces the pressure on top which creates lift from atmospheric pressure acting below the ball. Principle of flight: simples!
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Post by delaplume on Feb 28, 2019 22:06:02 GMT
Hi Roger,
You've fallen into the trap that catches quite a few..... Remember I mentioned about the Pressure / Velocity / Temperature balance ??
One of the benefits of using an injector over the by-pass pump is that the injector delivers WARM water at HIGHER than boiler pressure, whereas the by-pass delivers it at Ambient temp ( Usually Cold )...........The injector feedwater will thus condense LESS steam than it's equivalent output by-pass pump and is kinder to the boiler overall...( No cold water "slugs" etc. ) plus an increase in thermal eficiency..
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Post by delaplume on Feb 28, 2019 22:25:15 GMT
Just to give a bit of an insght re}--- Water consumption on full-size locos......A Duchess with 12 bogies on the tender ( 360 ton approx ) attacking Beattock at a consistent 40mph is generating something in the region of 3,000 HP...........You can imagine the steam demand that those 4 cylinders set at 60% forwards would create.....and the subsequent water flow into the boiler to satisfy it ??
Yes, depending on the situation you can leave a small injector on semi-permanently to balance lets say about 2/3 the demand with "Top-ups" by the other injector as and when you feel it's needed............Don't forget that many mainline express locos had an Exhaust Injector fitted as well...
You must treat each journey as being unique and not try to put water in at the same place on a circular track.....There are too many variables for one thing---- eg}-- A change of passenger load, an unexpected stop, you "loose" the fire for a moment and need to make it up again ( Def. NO water untill pressure is regained )...
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Gary L
Elder Statesman
Posts: 1,208
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Post by Gary L on Feb 28, 2019 23:11:11 GMT
I should imagine the surface friction might be a factor in the parts of the injector where laminar flow isn't occurring, I suspect most of the fluid moving through is quite turbulent? Also the rougher the finish the more the Reynolds number will come into things. I've not touched fluid dynamics in some time... Recent (last 20 years) thinking in motorcycle and car engine tuning leaves the inlet ports rough, like a coarse emery finish rather than polished as used to be the case. That's true of racing yacht hulls too. It is something to do with boundary layers. The idea is that a layer of water is encouraged to adhere to the hull surface and thus lubricate the passage of the main body of water. Something like that. At the molecular level, even a smooth polished surface is going to be all hills and dales. I suspect the reasoning is as much to do with the pointlessness of working up a perfect polished finish as anything. -Gary
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jma1009
Elder Statesman
Posts: 5,900
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Post by jma1009 on Feb 28, 2019 23:41:56 GMT
I do hope that forum members will especially in the case of this important thread not start or contribute to 'thread drift' as has already happened.
Please keep on topic! (Hopefully the moderators might take note).
Ask questions or like Kipford provide valuable input, but we want to keep to the thread topic without thread drift please!
Roger has spent a great deal of time doing all this.
I'm off for a few days. Robmort and Baggo might like to comment as they have both made injectors as has Adam. Stewart Hart might also like to contribute.
Cheers,
Julian
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Post by John Baguley on Mar 1, 2019 1:15:55 GMT
I'm not sure that I can add anything to Roger's 'design' thread as I basically just made a few small injectors by following the information in DAG Brown's original articles in Model Engineer back in 2000. I think his recent book is basically just a reprint of those articles. I never really delved much into the theory side as I just wanted to try following the 'Words and Music' and see what happened.
No one was more surprised than me when I actually got them to work but not until after several attempts at making the cones. I think it was more by luck than judgement! I think I made three 8oz and one 4 oz. I was only really interested in injectors suitable for a 2½" gauge loco, hence the small capacities. I really didn't expect any success with the 4oz one but that actually worked pretty much first time. Unfortunately, it proved to be too small, even for my Helen Long, so I only used it for a short time.
I was probably pretty lucky to get such small injectors to work at all as the smaller they are, the more critical the dimensions of the cones become. They are also much more susceptable to muck etc.
If anyone hasn't already read it, here's my account of my exploits at the time when I was experimenting with them:
My intention has always to revisit them but it just hasn't happened yet. Too many other distractions.
I think my major problem was with making good enough taper reamers. I've since acquired a nice Quorn tool and cutter grinder and I think that would make the taper reamers much easier to make accurately with a suitable surface finish. It has always surprised me that no one has offered the reamers on a commercial basis. I am sure that there would be a demand for them.
Roger - I have copies of most of the articles that have appeared in ME over the years if they would be of interest to you.
Has anyone mentioned C M Keiller yet? He was making small injectors for 1/2" scale locos many moons ago way before the likes of Laurie Lawrence etc. He did quite a bit of experimentation and proved that it was possible to get small injectors to feed successfully though 1/16" diameter pipe!
I've always thought it a bit of a myth about having to have very easy bends on supply lines etc. A good injector will easily put out 200psi or more which will have no problems overcoming any restrictions in the feed lines and clacks. I think this mindset probably comes from the fact that a lot of commercial injectors in the past have been pretty rubbish and only work if the conditions are ideal, the exceptions being those made by the likes of Gordon Chiverton etc.
Roger - I would be very interested if you come up with a design for an electrically heated test boiler as that has been my intention for some years now. I've just acquired a 12" length of 6" diameter copper tube which will be ideal!
John
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kipford
Statesman
Building a Don Young 5" Gauge Aspinall Class 27
Posts: 566
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Post by kipford on Mar 1, 2019 4:14:35 GMT
John I have to disagree about ignoring making the flow path as easy and free flowing as possible. The pressure loss through the pipe work is a function of velocity. Loss = 1/2 x density x square of velocity x loss coefficient K. The value of K depends on what work we are doing to the fluid. Turning fluid through 90 degrees, sharp turn with no radius will have a K value of between 1 and 1.25 depending on the pipe shape. Put a radius in the pipe and suddenly K drops below unity and can get down to values around 0.25. If you have sharp edge turns and high pipe velocity it does not take many changes of direction to start to eat into the potential pressure rise the ejector can achieve. When I get home I will run some calcs to show you. Regards Dave
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Post by Roger on Mar 1, 2019 8:42:54 GMT
I'm not sure that I can add anything to Roger's 'design' thread as I basically just made a few small injectors by following the information in DAG Brown's original articles in Model Engineer back in 2000. I think his recent book is basically just a reprint of those articles. I never really delved much into the theory side as I just wanted to try following the 'Words and Music' and see what happened.
No one was more surprised than me when I actually got them to work but not until after several attempts at making the cones. I think it was more by luck than judgement! I think I made three 8oz and one 4 oz. I was only really interested in injectors suitable for a 2½" gauge loco, hence the small capacities. I really didn't expect any success with the 4oz one but that actually worked pretty much first time. Unfortunately, it proved to be too small, even for my Helen Long, so I only used it for a short time.
I was probably pretty lucky to get such small injectors to work at all as the smaller they are, the more critical the dimensions of the cones become. They are also much more susceptable to muck etc.
If anyone hasn't already read it, here's my account of my exploits at the time when I was experimenting with them:
My intention has always to revisit them but it just hasn't happened yet. Too many other distractions.
I think my major problem was with making good enough taper reamers. I've since acquired a nice Quorn tool and cutter grinder and I think that would make the taper reamers much easier to make accurately with a suitable surface finish. It has always surprised me that no one has offered the reamers on a commercial basis. I am sure that there would be a demand for them.
Roger - I have copies of most of the articles that have appeared in ME over the years if they would be of interest to you.
Has anyone mentioned C M Keiller yet? He was making small injectors for 1/2" scale locos many moons ago way before the likes of Laurie Lawrence etc. He did quite a bit of experimentation and proved that it was possible to get small injectors to feed successfully though 1/16" diameter pipe!
I've always thought it a bit of a myth about having to have very easy bends on supply lines etc. A good injector will easily put out 200psi or more which will have no problems overcoming any restrictions in the feed lines and clacks. I think this mindset probably comes from the fact that a lot of commercial injectors in the past have been pretty rubbish and only work if the conditions are ideal, the exceptions being those made by the likes of Gordon Chiverton etc.
Roger - I would be very interested if you come up with a design for an electrically heated test boiler as that has been my intention for some years now. I've just acquired a 12" length of 6" diameter copper tube which will be ideal!
John
Hi John, Thanks for contributing your experiences, I'm surprised to hear that the 4 fl oz/min was too small for a 2-1/2" gauge locomotive. I wonder if this is because the efficiency of very small locomotives is much worse than say 5" gauge ones? It does suggest that you might be able to have a tiny injector running most of the time while you're driving, using a much more substantial one to top up if necessary. Has anyone ever tried this? Any articles would be welcome, it's useful to cross check the 3D model and see if the dimensions come out close, even if there's no descriptions of how to design them. I'll certainly post my design for an electric boiler, it might be made from Stainless Steel though, I've not got a clear picture of what it will be like yet.
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oldnorton
Statesman
5" gauge LMS enthusiast
Posts: 692
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Post by oldnorton on Mar 1, 2019 10:44:57 GMT
One of the benefits of using an injector over the by-pass pump is that the injector delivers WARM water at HIGHER than boiler pressure, whereas the by-pass delivers it at Ambient temp ( Usually Cold )...........The injector feedwater will thus condense LESS steam than it's equivalent output by-pass pump and is kinder to the boiler overall...( No cold water "slugs" etc. ) plus an increase in thermal eficiency.. I kind of agree with the 'no cold water shock to the boiler' point made. But does the efficiency/energy argument not run counter to the basic conservation of energy rule? The locomotive and water tank are a (semi) sealed system. 250ml of cold water pumped might remove exactly the same thermal energy from the boiler as 250ml delivered by an injector. Or am I making a wrong conclusion somewhere? Norm
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Post by John Baguley on Mar 1, 2019 10:55:47 GMT
Hi Dave,
What I was really suggesting re flow path is that a well designed and functioning injector should be able to overcome any restrictions in the flow path, such as sharp bends etc. I agree this may well reduce the performance and output though. The problem is that some commercial injectors barely work at all and need optimum conditions for them to work at all. I've tested a few such injectors and they are very fiddly to get to work and very temperamental in operation. I think that is why some people seem to have so much trouble with them.
If you look at the design of many full size injectors, the outlet from the delivery cone is turned through 180° and then turned through another 90° before it exits from the side of the injector. That's a very tortuous route!
It's very interesting to look at the designs available to modellers in the US e.g. those made by Eccentric Engineering. They are totally different to 'ours' and seem to follow full size designs and are far more complex.
Roger - I'll sort out what articles I have, upload them to Dropbox and then send you a link.
Re the 4oz injector - it was my idea that you would be able to leave it running most of the time but trying to keep a 2½" gauge boiler stable enough during running can be a nightmare at the best of times! The slightest change in pressure or water levels etc. just knocks it off all the time. It did work fine when the loco was stationary but was very slow to put any amount of water in the boiler. I find that an 8oz is pretty much ideal for a 2½" loco. An 11 or 12oz works well but knocks the boiler pressure down very quickly, even with the blower full on. You have to use it in short bursts and then let the pressure recover.
The problem that I envisage with the electrically heated boiler is that of sealing where the element will exit the tube so that it will not leak under pressure. The element still needs to be removable for replacement if necessary. Maybe I'm overthinking it. I think that there has been a few designs published in ME so I'll have to do a search and see what has been done before.
John
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Post by Roger on Mar 1, 2019 11:16:36 GMT
Materials...
It would appear that both bodies and cones are usually made from Brass, and it's easy to see why. The material is easy to machine and it's relatively cheap. Bob Bramson says that free machining grade CZ121 is the usual material.
However, other materials for the cones are certainly possible, including Monel metal, CZ111 or CZ112 Bronze, and Free cutting stainless Grade 3033S21 (which I think is a typo, 303S21 is probably what he means). I'm sure there are many more.
Clearly some of these are much more difficult to machine than others, especially when reaming the tapers. The amount of material used is very small though, so cost isn't really a factor. One limiting factor is the design of the Steam cone, which is wafer thin on the end when Annular Regulation is used. I don't think that could be made from anything else but metal. However, the Steam cone for End Regulation is a different matter because it has a blunt nose.
One class of materials not mentioned is Plastics, and I'm interested to know whether one could work for the cones. They might prove to be completely unsuitable because they aren't rigid enough. However it would be an interesting experiment. The motivation is to find a material that resists the build up of deposits on the surface. One thought is to use Delrin which has a high melting point (347C), is pretty rigid and produces a mirror finish with ease. My guess is that this could be made to work in the larger sizes, but would probably be too difficult to get the dimensions right for the smallest ones. One possible advantage is that the cones wouldn't have a large capacity to store heat, so perhaps they would perform better when the water is hot? I don't think PTFE in any form is suitable because I don't think it's rigid enough, even as Fluorosint.
Anyway, I throw the idea out there because, as far as I'm aware, it's not been mentioned anywhere as even being a possibility. It may be a stupid idea, but then again, it might just work!
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Post by Roger on Mar 1, 2019 11:34:28 GMT
Hi Dave,
What I was really suggesting re flow path is that a well designed and functioning injector should be able to overcome any restrictions in the flow path, such as sharp bends etc. I agree this may well reduce the performance and output though. The problem is that some commercial injectors barely work at all and need optimum conditions for them to work at all. I've tested a few such injectors and they are very fiddly to get to work and very temperamental in operation. I think that is why some people seem to have so much trouble with them.
If you look at the design of many full size injectors, the outlet from the delivery cone is turned through 180° and then turned through another 90° before it exits from the side of the injector. That's a very tortuous route!
It's very interesting to look at the designs available to modellers in the US e.g. those made by Eccentric Engineering. They are totally different to 'ours' and seem to follow full size designs and are far more complex.
Roger - I'll sort out what articles I have, upload them to Dropbox and then send you a link.
Re the 4oz injector - it was my idea that you would be able to leave it running most of the time but trying to keep a 2½" gauge boiler stable enough during running can be a nightmare at the best of times! The slightest change in pressure or water levels etc. just knocks it off all the time. It did work fine when the loco was stationary but was very slow to put any amount of water in the boiler. I find that an 8oz is pretty much ideal for a 2½" loco. An 11 or 12oz works well but knocks the boiler pressure down very quickly, even with the blower full on. You have to use it in short bursts and then let the pressure recover.
The problem that I envisage with the electrically heated boiler is that of sealing where the element will exit the tube so that it will not leak under pressure. The element still needs to be removable for replacement if necessary. Maybe I'm overthinking it. I think that there has been a few designs published in ME so I'll have to do a search and see what has been done before.
John
Thanks for that insight John and the offer of the articles, that's great. I've started another thread here about test equipment for injectors if people want to contribute to that there.
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weary
Part of the e-furniture
Posts: 290
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Post by weary on Mar 1, 2019 13:04:14 GMT
Combining Cone Dimensions
Quote from Julian: Eric Rowbottom, via Basil Palmer (both of whom knew a great deal about injectors) provided a table of the lengths of the 2 halves of the combining cone for different sizes of injectors. It is on p.440 ME 7th May 1976.
Maybe of wider interest, so ->
Table referred to, captioned "Combining Cone" looks like this:
SIZE A B C D E F* G
74 0.125 0.032 0.156 0.313 No.72 0.156 .015 min, 0.030 max 72 0.140 0.032 0.172 0.344 No.68 0.156 Ditto 70 0.156 0.035 0.188 0.379 No.66 0.188 Ditto 69 0.156 0.035 0.188 0.379 No.63 0.219 Ditto
Sizes in Inches.
A = Length of "Draught Cone" (First Cone) B = Annular Gap between the "Draught Cone" and the "Mixing Cone" (First and second cone components of Combining Cone) C = Length of 'Mixing Cone" D = Overall length of "Draught Cone", "Annular Gap", and "Mixing Cone". E = Drill size exit hole of "Mixing Cone" F*= Overall Exterior Diameter of Cones. *note reads: See text - Diameter to suit body bore G = Length of parallel section drilled out at exit of "Mixing Cone" (Second Cone).
Internal Cone angle of "Draught Cone" given as 10-9 degrees with "Very small radius and blend" on larger end Internal cone angle of "Mixing Cone" given as 9 degrees with "slight chamfer" on larger end.
Approximate Delivery Rates:
No.74 = 1 pint per minute No.72 = 1.125 pints per minute No.70 = 1.25 pints per minute No.69 = 1.625 pints per minute.
Regards, Phil.
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Post by Roger on Mar 1, 2019 21:40:53 GMT
Several members have kindly sent me a variety of articles going back over the years, written by at least six different authors, some of which have been mentioned above.
Reading it all is heavy going, brevity and injectors don't seem to be good bedfellows! There's a lot of anecdotal description and subtle modifications to existing designs which is interesting for those specific cases but not terribly useful for our purposes.
There are some useful diagrams and tables of the relative proportions of the various elements, so those might be worth pursuing.
I've been speed reading through it so see if I can latch onto the more useful stuff, and I found a couple of things of interest.
One comment was that the colour of the delivery stream looks 'milky' which is attributed to tiny air bubbles in the water. This is consistent with the claim that air gets drawn into the boiler. It's also interesting that it's not considered important for copper boilers and I didn't see any mention of the effect that might have on the temperature of water the injector will work with.
Almost all of the articles just copy the standard arrangement of ball valve and Annular regulation. I haven't seen one diagram of End regulation. There is mention of the effect of having insufficient regulation, that being of water overflowing, presumably because there's too much being drawn in to be able to pass through the Mixing cone. I hadn't really appreciated this, but I suppose it's obvious really. I'll add this back into the discussion on that above.
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Post by David on Mar 1, 2019 22:51:49 GMT
One commercial injector down here uses a flat valve rather than a ball. It has a stem that goes up into the valve chamber plug to hold it in alignment. It has an o-ring around the working face to provide the seal - the o-ring is on the valve, not the seat. This may be related to a comment above. When mine are working they don't usually chirp. Perhaps that's because the valve is sealing well.
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