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Post by coniston on Apr 23, 2020 20:36:58 GMT
Surprisingly the saw went through with no problem at all, although I am a bit cautious with the feed rate.
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Post by mugbuilder on Apr 23, 2020 23:24:17 GMT
LBSC type spearhead superheaters can and do work suprisingly well.Many years ago I built a 3 1/2" gauge Juliet and fitted them ending just short of the firebox. As I was new to the hobby and materials were a bit hard to get where I lived, I made the gunmetal valves in 2 pieces and as I didn't have any silver solder at the time I soft soldered the pieces together.When finished the engine ran very well until one day when running it flat out on my dads little track at home it came to a sudden and grinding halt with the wheels refusing to rotate. On inspection I found to my amazement that the soft solder on both valves had melted,seperating the 2 parts and had run onto the gunmetal port face and then reset effectively soldering the valve to the port face.Obviously the lubrication was a bit crook as this allowed the solder to stick but it shows how hot the steam can get.The boiler pressure was set at 80psi so the temperature was only about 160degrees. As the melting point of lead-tin soft solder is I think around 300 degrees how could this possibly happen? I am sure that many of the bright minds on this forum can come up with an answer as I am at a loss.
My first 5" gauge engine was a NSW '50' class 2-8-0 with 5-5/8" diameter wheels, and shortly after it was completed I entered it in a local efficiency competition. This engine had spearhead superheaters finishing just short of the firebox. The track was elevated with a gradient of about 1-100. I took a load of 3720 pounds [about 1-1/2 ton] and the engine ran continuously without sliping for the allocated 25 minuites at an average speed of 9MPH. I didn't win but came 4th. you cant ask for more than that.
Further on the matter of an engine bolting if it primes, I can assure that it can result in a sudden run away that takes you by suprise and can be rather frightening. It can and does even with non-radient superheaters. I would always fit some form of superheating to an engine as it can greatly improve the performance but to my mind reliabiltiy and ease of controll makes for a more pleasurable experience.
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uuu
Elder Statesman
your message here...
Posts: 2,859
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Post by uuu on Apr 24, 2020 8:50:34 GMT
I have a Fiat 500. Nice little car but performance is a bit dull. It's never been fitted with a superheater turbocharger, and I've heard that they can really transform a car's behaviour.
I've also heard that a Porsche 944 turbo goes like stink - I had one of these (OK, not the turbo one). So do I fit a superheater turbocharger off one of those onto my Fiat?
Or, do I think more Smart car? I had one of these - sweet little engine, modest superheater turbocharger, doesn't go like stink, but very pleasant and well balanced.
I think I know which way I'm going, but other Fiat/Porsche/Smart car owners are, of course, free to choose which way they want to go.
Wilf
(Edit - first version had supposed Morris Minor instead of actual Fiat)
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Post by andyhigham on Apr 24, 2020 9:00:47 GMT
The problem with using the car analogy is we are all headed towards Hybrid (read diesel electric) or Electric as the railways did many years ago.
A Tesla will embarrass a Porsche 944 on acceleration 13secs standing start quarter mile
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Post by Roger on Apr 24, 2020 12:28:12 GMT
LBSC type spearhead superheaters can and do work suprisingly well.Many years ago I built a 3 1/2" gauge Juliet and fitted them ending just short of the firebox. As I was new to the hobby and materials were a bit hard to get where I lived, I made the gunmetal valves in 2 pieces and as I didn't have any silver solder at the time I soft soldered the pieces together.When finished the engine ran very well until one day when running it flat out on my dads little track at home it came to a sudden and grinding halt with the wheels refusing to rotate. On inspection I found to my amazement that the soft solder on both valves had melted,seperating the 2 parts and had run onto the gunmetal port face and then reset effectively soldering the valve to the port face.Obviously the lubrication was a bit crook as this allowed the solder to stick but it shows how hot the steam can get.The boiler pressure was set at 80psi so the temperature was only about 160degrees. As the melting point of lead-tin soft solder is I think around 300 degrees how could this possibly happen? I am sure that many of the bright minds on this forum can come up with an answer as I am at a loss. My first 5" gauge engine was a NSW '50' class 2-8-0 with 5-5/8" diameter wheels, and shortly after it was completed I entered it in a local efficiency competition. This engine had spearhead superheaters finishing just short of the firebox. The track was elevated with a gradient of about 1-100. I took a load of 3720 pounds [about 1-1/2 ton] and the engine ran continuously without sliping for the allocated 25 minuites at an average speed of 9MPH. I didn't win but came 4th. you cant ask for more than that. Further on the matter of an engine bolting if it primes, I can assure that it can result in a sudden run away that takes you by suprise and can be rather frightening. It can and does even with non-radient superheaters. I would always fit some form of superheating to an engine as it can greatly improve the performance but to my mind reliabiltiy and ease of controll makes for a more pleasurable experience. It's interesting to hear about what actually happens in practice, it sometimes seems to me that there's too much opinion dressed up as fact, without facts to back them up. As it happens, the melting point of 60/40 Soft Solder is only 188C, so that only equated to a little over 20C of Superheating at 90PSI. It does clearly show that the Superheaters weren't just 'Steam driers' though. It will be interesting to see if my PTFE piston rings survive or whether those will have to be exchanged for metal ones. I won't know for sure until I get it into steam. All good fun! |
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Post by coniston on Apr 24, 2020 19:52:13 GMT
More done today, firstly I am waiting for a 3/4" x 26 die from Tracy Tools so can't make the bit that screws into the tube plate bush to take the wet header so to at least get he wet header aligned I made a steel dummy part that slides inside the thread and locates in the recess in the header.   I tried bending 3/8" copper pipe to join the header to the super heaters but I just couldn't get tight enough bends using my existing bending tool (typical small plumbers one bought on ebay) and I didn't want to make another special bending tool. Because of the Don Young design I followed I have to make two bends which are too close together for me. So I schemed out another way using a gun metal 45 degree block and some existing tight 90 degree bends I had. Even with the tight bends I still couldn't reliably bend the copper pipe to join to them.    It looks like it will all fit so I'll make a second one tomorrow and hopefully be able to get the lot joined up before the end of the week end.  One thing you'll notice is the blower connection is now hidden behind the steam pipe. That isn't too much of a problem for me as my original loco has the blower steam from the valve running through the big pipe on the outside of the boiler (is it the vacuum ejector pipe?) to the smokebox, so I can still use that and just fit a screwed solid stay instead of the hollow blower stay. Chris D |
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Post by mugbuilder on Apr 24, 2020 23:28:08 GMT
Sorry Chris for causing such disruption to your excellent thread. I will shut up in future.
Barry
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Post by Roger on Apr 25, 2020 7:13:44 GMT
Hi Chris,
I'm curious to know why you didn't just make that bends all in one piece since that last one is such a gentle bend?
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Post by coniston on Apr 25, 2020 8:04:56 GMT
Sorry Chris for causing such disruption to your excellent thread. I will shut up in future. Barry Hi Barry, its not a problem adding your own thoughts and experiences, please continue as it adds more fuel to the fire so to speak and that's how we all learn. And yes I know non radiant super heaters do work although to a lesser degree (physics must surely confirm that) and will make an easier to drive loco than no super heating. As you say you are making locos for other people so take the best course of action for yourself, that's perfectly understandable. Cheers, Chris D |
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Post by coniston on Apr 25, 2020 8:09:19 GMT
Hi Chris, I'm curious to know why you didn't just make that bends all in one piece since that last one is such a gentle bend? Hi Roger, I did try but the bend radius for the 90 degree bend is too large using my own equipment to then get even a shallow bend straight after in another plane. Even after annealing the 3/8" x 18g tube I have is very difficult to bend by hand. I can take some photos of my attempts later to hopefully show this. The bend you see in the photos was made on a hydraulic machine bender, they were on the ends of a piece of pipe in my 'useful' box. |
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Post by Roger on Apr 25, 2020 8:12:29 GMT
Hi Chris, I'm curious to know why you didn't just make that bends all in one piece since that last one is such a gentle bend? Hi Roger, I did try but the bend radius for the 90 degree bend is too large using my own equipment to then get even a shallow bend straight after in another plane. Even after annealing the 3/8" x 18g tube I have is very difficult to bend by hand. I can take some photos of my attempts later to hopefully show this. The bend you see in the photos was made on a hydraulic machine bender, they were on the ends of a piece of pipe in my 'useful' box. Fair enough, without a compact bender that's not going to be easy. |
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Post by John Baguley on Apr 25, 2020 8:31:42 GMT
It will be interesting to see if my PTFE piston rings survive or whether those will have to be exchanged for metal ones. I won't know for sure until I get it into steam. All good fun! My Helen Long has PTFE piston rings and PTFE valve heads and they seem to be surviving ok. The superheat is fairly high I would imagine as it has two full length radiant superheaters. I did try measuring the temperature of the cylinders when the loco was on the rolling road but my digital thermometer only reads to 150° C and that went straight off the scale.
I did notice that the steam distribution manifold under the smokebox that is made from phosphor bronze turned blue in a very short time! Not sure what temperature that would equate to.
I originally used O ring seals on the joints for the steam pipes to the cylinders and they didn't last very long at all. They just went 'gooey' and disintegrated. PTFE seals suffered a similar fate. I looked at Kalrez high temperature O rings but they were hard to come by and very expensive for a small quantity. I finally had to use 'compression' joints with copper olives and they have worked well.
I've experienced the surging that Barrie mentions several times when I've forgotten to open the bypass from the axle pumps and overfilled the boiler!
John
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Post by Roger on Apr 25, 2020 9:04:03 GMT
It will be interesting to see if my PTFE piston rings survive or whether those will have to be exchanged for metal ones. I won't know for sure until I get it into steam. All good fun! My Helen Long has PTFE piston rings and PTFE valve heads and they seem to be surviving ok. The superheat is fairly high I would imagine as it has two full length radiant superheaters. I did try measuring the temperature of the cylinders when the loco was on the rolling road but my digital thermometer only reads to 150° C and that went straight off the scale.
I did notice that the steam distribution manifold under the smokebox that is made from phosphor bronze turned blue in a very short time! Not sure what temperature that would equate to.
I originally used O ring seals on the joints for the steam pipes to the cylinders and they didn't last very long at all. They just went 'gooey' and disintegrated. PTFE seals suffered a similar fate. I looked at Kalrez high temperature O rings but they were hard to come by and very expensive for a small quantity. I finally had to use 'compression' joints with copper olives and they have worked well.
I've experienced the surging that Barrie mentions several times when I've forgotten to open the bypass from the axle pumps and overfilled the boiler!
John
Hi John, Sorry Chris for this diversion, I hope you don't mind. I've got one of those point and shoot digital thermometers which ought to be ideal for looking at the steam feed pipes to the cylinders. I've gone for copper washers in a flat face compression joint to the Superheaters so I can detach them and slide then sideways. If you recall, my pipes to the cylinders are one piece with a ball in sleeve type of metal seal at the Smokebox wall. Blueing starts at around 300C and continues getting darker for another 40 degrees or so. PTFE is ok for operating up to 260C, melting at 335C, so presumably the walls are keeping the PTFE cool enough to survive. I suppose if the exposed edges are small, the valves are repeatedly shielded and cooled as the exhaust nearby is at a lower temperature. It will be interesting to see if I get away with it, because I've got four Radiant Superheaters with Turbulators. Martin Johnson's analysis of my Boiler and Superheater comes with the conclusion that it's the most risky option, he also looked at two and three Superheaters options. His comment was that it 'would perform very well if it does not self destruct!'. Well, you know me, I'm up for a challenge. Martin's final analysis indicated 321C in the steady state maximum power, but he thinks his calculations may slightly underestimate that. So frankly, it's marginal whether it will work with PTFE, but it will be fun finding out! The maximum temperature could of course be higher after a stop, so that's where the problems might show themselves. In the end, if the problems are insurmountable, I can slip a shield tube over the radiant ends, or redesign the Superheater headers to use the Bi-Metallic strip I made to operate a thermostatic bypass valve from the wet header to the dry one. All things to keep me interested. |
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Post by andyhigham on Apr 25, 2020 9:29:29 GMT
This causes an interesting point with piston valves in gunmetal or bronze cylinders.
With cast iron, cast iron rings will work perfectly in cast iron bores. Can the same be said for gunmetal/bronze? or is there risk of seizure?
Could a different composition of bronze be used for the rings? Aluminium rings?
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Post by mugbuilder on Apr 26, 2020 0:12:40 GMT
An interesting experiment. When annealing copper flanged plates it has often fascinated me when quenching If I first put a small ammount of cold water onto the very hot plate it will just sit there for some seckonds with apparently no effect and then sudenly flash into steam. I think that the theory is that a very thin film of steam is insulating the rest from the heat untill the bulk of the drop heats up. Could the same thing happen in a radient superheater and reduce its effectiveness, or will the fact that any water that is in the elements is already hot, prevent this?
Regards, Barry
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Post by coniston on Apr 26, 2020 22:32:05 GMT
An interesting experiment. When annealing copper flanged plates it has often fascinated me when quenching If I first put a small ammount of cold water onto the very hot plate it will just sit there for some seckonds with apparently no effect and then sudenly flash into steam. I think that the theory is that a very thin film of steam is insulating the rest from the heat untill the bulk of the drop heats up. Could the same thing happen in a radient superheater and reduce its effectiveness, or will the fact that any water that is in the elements is already hot, prevent this? Regards, Barry That reminds me of a video we were shown during an automotive air conditioning course I did at Brighton University over 20 years ago (so may not recollect this 100%). A clear flask of water was heated through the boiling point where bubbles are ferociously being generated and water is very turbulent, to a stage where a complete bubble of steam appeared at the bottom of the flask and the eater above appeared quite still. I will have to try and find my notes to remember all the details but IIRC we were being demonstrated the need to generate turbulence by means such as internally rifled tubes (related to heat exchanger performance of refrigeration/air conditioning systems). I think it is a different matter with super heaters as the water has already changed state to steam, albeit it saturated. Therefore there would be only droplets of water in contact with the surface of the super heater. Unless of course the boiler is priming when you could in theory get water in the super heaters which as others have said will turn to flash steam if they are hot enough. As you say an interesting experiment, if only I had time for all the interesting experiments. Chris D |
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Post by Roger on Apr 26, 2020 22:43:21 GMT
An interesting experiment. When annealing copper flanged plates it has often fascinated me when quenching If I first put a small ammount of cold water onto the very hot plate it will just sit there for some seckonds with apparently no effect and then sudenly flash into steam. I think that the theory is that a very thin film of steam is insulating the rest from the heat untill the bulk of the drop heats up. Could the same thing happen in a radient superheater and reduce its effectiveness, or will the fact that any water that is in the elements is already hot, prevent this? Regards, Barry That reminds me of a video we were shown during an automotive air conditioning course I did at Brighton University over 20 years ago (so may not recollect this 100%). A clear flask of water was heated through the boiling point where bubbles are ferociously being generated and water is very turbulent, to a stage where a complete bubble of steam appeared at the bottom of the flask and the eater above appeared quite still. I will have to try and find my notes to remember all the details but IIRC we were being demonstrated the need to generate turbulence by means such as internally rifled tubes (related to heat exchanger performance of refrigeration/air conditioning systems). I think it is a different matter with super heaters as the water has already changed state to steam, albeit it saturated. Therefore there would be only droplets of water in contact with the surface of the super heater. Unless of course the boiler is priming when you could in theory get water in the super heaters which as others have said will turn to flash steam if they are hot enough. As you say an interesting experiment, if only I had time for all the interesting experiments. Chris D Hi Chris, Turbulence is definitely key to heat transfer. In my correspondence with Martin Johnson and his analysis of my boiler, he mentioned that turbulent flow in the first part of the flues turns to laminar flow quite quickly. This is one reason why you don't get as much heat transfer as you might expect from a long boiler. The same issue is present in Superheater tubes, where the established flow becomes laminar and the heat transfer is much reduced. This is why I've made my experimental Superheaters with Turbulators which you might not have seen. The idea is to scour the boundary layer off the wall and improve the heat transfer as a result. The central wire stops the steam from going down the middle, and the spiral is intended to cause turbulence and increase the velocity at the surface compared to a conventional tube. If my cylinders melt, you'll know why! Still, nothing ventured, nothing gained. Reducing heat transfer is easy, I can just sleeve part of them.  20160807_113447 by Roger Froud, on Flickr |
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Post by coniston on Apr 30, 2020 19:25:23 GMT
Slow but steady progress over the last few days, had to fit in working two days, shopping for my parents, gardening for my in-laws as well. I finished the wet steam pipes from header to super heaters and tidied up the gunmetal joining bends a bit.  Tuesday the 3/4" x 26 BSB taps and die arrived from Tracy Tools so I got on and made the screwed bush that the wet header will fit onto and takes the steam from the regulator to wet header. Again made from the same piece of cast gunmetal as the wet header. I decided to make it hexagon rather than round as Don Young shows. This will make it easier to remove at a later stage if I ever need to get the regulator out. The cast gunmetal wasn't quite big enough to get a complete hexagon at 1 1/4" AF but it is better than a round one.  I used my 5C collet spin indexer to hold it for machining the hexagon rather than setting up the rotary table, it is quicker for this type of thing. Also it has a ER32 collet adaptor so in this case I used that.  Here it is fitted into the boiler  Last job today was to silver solder the wet header pipes together, I did this in stages as trying to set each one up with all the joints in the right place just wasn't going to be reliable.  And it all fits Phew!!  Next job will be to make the dry header and pipes. I will make a new Tee piece to screw onto the existing steam pipe to cylinders so it will be less restrictive than the original single pipe to one side. Chris D |
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Post by coniston on May 1, 2020 18:47:34 GMT
First job today was to silver solder the joining blocks onto the ends of the super heaters, I set them up vertically clamped to a spare scribing block with an odd bit of stainless to make up the height difference between the two blocks. I use a turbo torch with mapp gas for these jobs as it is easy to manage and has plenty of heat.   Then I silver soldered the copper pipes into the joiners after giving them a good clean. and another check to make sure everything still fits.  Starting on the dry header first job was to check the tube positions and measure them for the centres to drill in the dry header tube. I made the header from 3/4" x 18g copper tube. I made some end blanks to fit in the ends but wont fit them until the all the pipes are in place.  Then cut the pipes to length, bent them 90 degrees and silver soldered them into the header. I drilled a block of wood to hold the pipes in position when silver soldering. This is after cleaning them up in acid.  And just checking the fit before I join them to the super heaters.  There will be a pipe of each end where the holes are that take the steam to a new Tee piece that will screw onto the steam pipe you can see at the front of the smoke box saddle. The oil feed also connects into this new Tee, you can just see the oil delivery pipe union behind the steam pipe. |
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Post by coniston on May 3, 2020 19:44:12 GMT
Final bit of silver soldering done yesterday and today, finished the dry header and assembled it onto the rest of the super heater assembly.  And this is what it all looks like assembled. I think I could get a tune out of this.  Next part is the steam Tee connection, the original only has one connection from the old super heater but I am adding a second to hopefully reduce some of the resistance in the steam path. This is the original one. There is an oil connection opposite the steam connection.  I have got as far as making the body and the two steam union connections, made from hex bronze bar my thinking being it will be less susceptible to corrosion in the smokebox than brass would be. Typical Bronze it's tough old stuff and a real struggle to cut the 9/16 x 26 thread on the connections as my die is not the newest, but too late on Sunday to order a new one and wait for it so just about struggled to finish them. I just need to make the oil connection and drill the body to accept them all and silver solder it all together.  Chris D |
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