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Post by coniston on Apr 19, 2020 20:41:43 GMT
A bit more work today, firstly I machined the wet header to take the three unions, sorry no photos of the machining, then made a 5/16" x 32 union for the snifting valve (is it snifting or sniffting?). Then on to silver solder the whole lot up in one heating using correction fluid on the threads just in case.  After cleaning up looks reasonable to me.  Next job is to make the pieces to join the 1/4" super heaters to the 3/8" copper pipes from the wet header and to the dry header. I had some cast gunmetal bar, probably originally intended for axel boxes, so thought that would be ok. After skimming it down I then set to drilling the 1/4" holes. The 1/4" holes overlap in depth with the 3/8" holes in the middle of the opposite side. I have left them on the 'stick' so to speak just to make handling easier and I can drill all the holes on each side using the X axis dial graduations. I have left 1/16" between each block for sawing off and cleaning up. I did each hole using first a centre drill, then a 3mm drill to 7/16" depth, then opened out with a 1/4" drill to 7/16" depth. I used a diamond 'Eze Lap' to take the sharp edge off the drill giving effectively no rake angle to prevent it snatching, seemed to work a treat. First the centre drill:  and finally the 1/4" drill.  Just another 11 more holes to go, then it looks like this:  Next job is to turn it over and drill the 3/8" holes to join up with the 1/4" holes, that will be next time. Chris D |
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Post by springcrocus on Apr 19, 2020 21:38:27 GMT
Ah! Ok, I don't understand what is required so thanks for the guidance. Maybe I should dispense with superheaters altogether but that's not to be debated here in Chris's thread.
Regards, Steve
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jma1009
Elder Statesman
Posts: 5,919
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Post by jma1009 on Apr 19, 2020 22:19:10 GMT
Hi Steve,
Your loco is sort of similar proportions to Chris's LNER 5"g A3, and a 5"g Brit is going to be a sulky loco without superheaters, and will not 'sparkle'. It will also IMHO seriously reduce it's value when you 'pop it'.
I don't think I have ever driven a 3.5"g or 5"g loco without superheaters, but for some peculiar reason 'not having superheaters' seems to be ingrained in the mindset of some of the 7.25"g brigade, and I have not been impressed with those of this gauge without superheaters that I have driven; it's hard work!
It all really goes back to dear Don Ashton; there is no point having a good valve gear if all you do is run it in fullgear as our USA cousins do (so it seems), and do not get the advantages of shortened cut off (or use this) because you are using wet steam that is not so fluid and constipates the passages from steam port to cylinders and even more so on the exhaust side!
It is quite simple really!
Cheers,
Julian
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Post by springcrocus on Apr 20, 2020 6:59:53 GMT
Sorry, just thinking aloud. I was wondering how important they were and remembered that Jim in Australia chose to go unsuperheated. The superheaters designed for this Britannia are the squashed copper ends style and seem to get a bad press.
Regards, Steve
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kipford
Statesman
Building a Don Young 5" Gauge Aspinall Class 27
Posts: 575 
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Post by kipford on Apr 20, 2020 12:48:48 GMT
Chris Not trying to hijack your thread, but I have reworked the Aspinall superheaters from two co-axials to the two hairpin idea. I have used ¼ x 20 swg tube as an inital look see. By the way a quick look at the hoop stress in the pipe shows at 100 psi boiler pressure it is only about 5 MPa against a proof of about 260 for AISI316 and ultimate of 515 MPa. The loss of strength at temperature does not start to kick in properly until about 200 deg C, and 100 psi superheated steam has a temperature of no more than 150 deg C. So dropping the tube wall thickness a bit should would not be an issue. The design assumes I can use a bend radius (to the centre line of the tube) of 7.5 mm, 15mm between centres which although less than the normal 2D minimum, I think with a bit of trial and error is feasible. Space issue in the smoke box mean the wet header is a log design, the same as the original design. However it is not too bad from a pressure drop point of view a single sharp edge bend having only a full velocity head loss. Also the reduction in loss due to due not having a spear end will more than compensates for it. The joint to the steam chest is again a log for simplicity, but the flow path is actually almost as good as a more complex bifurcated pipe joint only two 45 degree turns so again just a full velocity head loss over both of them. I have used two ‘spiders’ to act as pipe separators and to try and reduce vibration effects. Any comments welcome. Pictures 1 and 2 show the superheater in-situ in the boiler.  Superheat 2 by Dave Smith, on Flickr  Superheat 1 by Dave Smith, on Flickr Picture 3 shows the superheater only.  Superheat 3 by Dave Smith, on Flickr Picture 4 shows the flow path the entry to superheater.  Superheat 5 by Dave Smith, on Flickr Picture 5 shows the flow path at the exit of the superheater.  Superheat 4 by Dave Smith, on Flickr Dave |
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Post by RGR 60130 on Apr 20, 2020 14:19:21 GMT
Chris The loss of strength at temperature does not start to kick in properly until about 200 deg C, and 100 psi superheated steam has a temperature of no more than 150 deg C. So dropping the tube wall thickness a bit should would not be an issue. Saturated and dry saturated steam at 100 psig can be expected to have a temperature in the region of 170C. Once you start to heat the steam, i.e. superheat it, the temperature will increase further. I hope this helps though it shouldn't cause a problem. Reg |
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Post by Deleted on Apr 20, 2020 15:39:48 GMT
One question re the resilience of the bends from heat...as they are radiant tubes wouldn't they get much, much hotter sitting over a raging fire?
Pete
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Post by Roger on Apr 20, 2020 15:58:41 GMT
One question re the resilience of the bends from heat...as they are radiant tubes wouldn't they get much, much hotter sitting over a raging fire? Pete Hi Pete, That's the whole point, and what makes them a different animal to the old types in the flue. There's no reason why they can't run Red hot, but I doubt if that ever happens, even with the blower flat out and stationary. Although the radiant heating will be great, there's a lot of flue gasses flowing over them sitting there high above the fire. I don't know what the temperature of those gasses is by the time they swirl around the Superheaters. It would be interesting to see what actually happens. |
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Post by Deleted on Apr 20, 2020 16:23:06 GMT
One question re the resilience of the bends from heat...as they are radiant tubes wouldn't they get much, much hotter sitting over a raging fire? Pete Hi Pete, That's the whole point, and what makes them a different animal to the old types in the flue. There's no reason why they can't run Red hot, but I doubt if that ever happens, even with the blower flat out and stationary. Although the radiant heating will be great, there's a lot of flue gasses flowing over them sitting there high above the fire. I don't know what the temperature of those gasses is by the time they swirl around the Superheaters. It would be interesting to see what actually happens. Hi Roger I was thinking more in relation to the comments above about the bends loosing some of their strength, I know that radiant gives much more heat. This brings me to another question, that of when an arch is fitted. Ok this may help sheild the tubes from the glare of the fire but then also, if the arch is doing its job properly the gases will be hotter still. I asking due to the comment that the wall thickness may not being an issue. In my minds eye thin tubes as used in full size should give better flow and heat down the flues as there's less obstruction to the gases travelling down them. Just my thoughts on the matter as at some point in the future, I too will be at this stage. Pete |
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Post by coniston on Apr 20, 2020 18:15:24 GMT
Chris Not trying to hijack your thread, but I have reworked the Aspinall superheaters from two co-axials to the two hairpin idea. I have used ¼ x 20 swg tube as an inital look ………………... Hi Dave, It looks feasible in theory but probably a bit awkward to weld the we header. You could change that to a block type similar to what has been discussed earlier, but you'd need to discuss that with whoever does the welding, I assume it is all in stainless? I don't know if support is necessary or over complicating it, bearing in mind our locos don't really suffer with vibration compared to an internal combustion engine vehicle, our vibration levels are really low frequency and probably very low amplitude. I'm not aware of anyone having problems with super heaters vibrating against each other or the flue tube to cause any defects. Neat bit of CAD though Chris D |
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kipford
Statesman
Building a Don Young 5" Gauge Aspinall Class 27
Posts: 575
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Post by kipford on Apr 20, 2020 18:43:51 GMT
Chris
I was only going to use Stainless for the hairpins, for the remainder I was going to use bronze and copper tube as it is all in the smoke box. This then allows it all to be silver soldered, which makes the joint configurations used viable. What do you think? Anyway my welding is S*1t.
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Post by Roger on Apr 20, 2020 18:57:57 GMT
Hi Pete, That's the whole point, and what makes them a different animal to the old types in the flue. There's no reason why they can't run Red hot, but I doubt if that ever happens, even with the blower flat out and stationary. Although the radiant heating will be great, there's a lot of flue gasses flowing over them sitting there high above the fire. I don't know what the temperature of those gasses is by the time they swirl around the Superheaters. It would be interesting to see what actually happens. Hi Roger I was thinking more in relation to the comments above about the bends loosing some of their strength, I know that radiant gives much more heat. This brings me to another question, that of when an arch is fitted. Ok this may help sheild the tubes from the glare of the fire but then also, if the arch is doing its job properly the gases will be hotter still. I asking due to the comment that the wall thickness may not being an issue. In my minds eye thin tubes as used in full size should give better flow and heat down the flues as there's less obstruction to the gases travelling down them. Just my thoughts on the matter as at some point in the future, I too will be at this stage. Pete Hi Pete, I don't think strength is of any concern, the tubes are all going to droop and rest on the flue bottom. I don't think an arch is going to project far enough to shield the Superheaters from the fire, they don't come that far back, and Radiant Superheaters usually almost touch the back of the firebox. I've used thin wall Stainless Steel tube, not because of greater heat transfer, it makes little difference, but so that it responds more quickly. Scouring the boundry layer from the inside of the tubes with the turbulators also ought to improve the response and the amount of heat transferred. Lots to think about, and it's all a compromise. |
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Post by mugbuilder on Apr 23, 2020 0:59:16 GMT
I know that I will be shot down in flames but am not a fan of excessive superheat in a model. I have always used spearhead superheater elements that stop short of the fire for a couple of reasons. If the engine primes at any time it can bolt uncontrollably as the instinct is to shut the regulator and that seals in the primed water into the radiant superheater elements on the cylinder side of the regulator.Some times they can run some distance before they can be brought under controll. Your lubrication has to be very good and reliable or damage can be done if it fails. I have repaired several stainless steel and copper superheater combinations and have found leaks at the stainless copper joints. And lastly as I have been building engines for others, the system that I use gives a reliable long lasting steam drier with no come backs. I am not in favour of no superheat as it can result in a doey engine. 'You pays your money and you makes your own choise.' P.S. Be very carefull not to have any boiler feed water spray over the steam supply to the wet header as it will cool the steam before it gets to there and will negate any increase in the steam temperature that your superheater will provide. Top feeds in particular need to be directed well away from the regulator feed.
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Post by Roger on Apr 23, 2020 9:12:18 GMT
I know that I will be shot down in flames but am not a fan of excessive superheat in a model. I have always used spearhead superheater elements that stop short of the fire for a couple of reasons. If the engine primes at any time it can bolt uncontrollably as the instinct is to shut the regulator and that seals in the primed water into the radiant superheater elements on the cylinder side of the regulator.Some times they can run some distance before they can be brought under controll. Your lubrication has to be very good and reliable or damage can be done if it fails. I have repaired several stainless steel and copper superheater combinations and have found leaks at the stainless copper joints. And lastly as I have been building engines for others, the system that I use gives a reliable long lasting steam drier with no come backs. I am not in favour of no superheat as it can result in a doey engine. 'You pays your money and you makes your own choise.' P.S. Be very carefull not to have any boiler feed water spray over the steam supply to the wet header as it will cool the steam before it gets to there and will negate any increase in the steam temperature that your superheater will provide. Top feeds in particular need to be directed well away from the regulator feed. I suppose 'excessive' is a relative term. I can see the priming issue being a problem on bigger locomotives, but on 5" gauge the riding truck brake would easily stop a locomotive that's trying to break away. Clearly the more Superheating the greater the effect. If you don't notice any effect when priming, it might well mean that your Superheaters aren't doing very much useful heat transfer. I certainly hear what you say about lubrication, but that can be made very reliable without much difficulty. Running any locomotive dry is likely to cause damage, so this is a high priority in any case. Again, it's a matter of how far you go with Superheating. To my way of thinking, joining Copper to Stainless Steel is asking for trouble and is unnecessary. I think it's far better to make it all from Stainless Steel. This is a design issue rather than one of Superheating per se. From a commercial point of view, I can see why you would be inclined to steer away from these issues, I think I would too. I'm not sure that you can consider any form of Superheater to be just a Steam drier. You aren't in control of that sweet spot where the Steam is dry and then begins to get hotter. So you're either not drying the Steam completely, or you're Superheating it. You can't run it at the condition where it dries the steam completely and that's that, it can't work that way. To me, the efficiency benefits of some reasonable degree of Superheating make sense. It ought to make the locomotive easier to manage and drive if you're not needing to boil so much water and feed as much coal. |
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Post by andyhigham on Apr 23, 2020 10:08:12 GMT
The only way to be sure would be to put thermocouples in the wet and dry headers. If there is no rise in temperature at the dry header the heat imparted to the superheater is only drying the steam (latent heat of evaporation). If there is a rise in temperature then the steam has been dried and superheating is taking place
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nonort
Part of the e-furniture
If all the worlds a Stage someone's nicked the Horses
Posts: 279
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Post by nonort on Apr 23, 2020 11:16:16 GMT
Hi Chris, I think the arguments for and against different types is a bit of a red herring. I would make the whole thing out off stainless though. You have the technology why make it from anything else? Weld all the joints. I think that the problems of joining stainless to copper/bronze is well documented.
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Post by Roger on Apr 23, 2020 11:56:58 GMT
The only way to be sure would be to put thermocouples in the wet and dry headers. If there is no rise in temperature at the dry header the heat imparted to the superheater is only drying the steam (latent heat of evaporation). If there is a rise in temperature then the steam has been dried and superheating is taking place Quote so. The worst possible setup is to heat water to near boilling point, then throw it away without getting any useful work from it. Unless the steam is dry, that's what's happening to some degree. However, once it's dry, all of the additional energy imparted to the steam is available to do useful work. |
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Post by coniston on Apr 23, 2020 20:06:47 GMT
Some interesting comments there guys, thank you.
I completely agree that superheating makes a big improvement to the running of a loco, I have one with and one without and although they are different locos I can categorically say the one without (Super Simplex) needs a lot more water putting in than my B1 and unless the boiler pressure is at maximum working pressure (100psi) driving the Simplex is like being in a rain forest with 100% Relative Humidity.
nonort - I understand the issues of joining copper/bronze to stainless but in my experience and ability I feel more comfortable making a sound joint that way rather than my rather unpredictable welding, so I will continue the way I am going at the moment. Of course it may all end in tears and have to think again.
Chris D
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Post by coniston on Apr 23, 2020 20:19:37 GMT
Last time I left off having drilled the 1/4 holes in the gunmetal blank, so next job was to turn it over and drill the 3/8" holes for the copper pipes that will join up to the wet and dry headers as you can see below.  The holes needed a bit of cleaning up at the joins so I used a carbide burr in a battery drill to do that.  Then I cut them off with a slitting saw in the mill.  After that each was cleaned up in the 4Jaw chuck in the lathe to remove some metal so they present as low a restriction to gas flow as I could, without going over too mad  And a complete pair of super heaters looks like this  Only then did I realise it would be better to stagger the joiners to allow a little more room in the flue tube for them to be move when fitting the whole assembly so I took an inch off one end of each element as here:  At the wet header end I had to make a 90degree union as the centre flue is too close to allow a bend in the copper pipe. Sorry it's not 3D CAD but good old fashioned paper and pencil.  Next job will be to bend the 3/8" tubes to join into the wet header from the two outside sets of super heaters. Then I can silver solder the whole lot together. Chris D |
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Post by Roger on Apr 23, 2020 20:31:05 GMT
That's a very neat solution.... you're pretty brave with that slitting saw setup though! I'm glad it didn't grab.
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