barlowworks
Statesman
Now finished my other projects, Britannia here I come
Posts: 877
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Post by barlowworks on Sept 29, 2019 11:03:26 GMT
Hi Roger
I see from your drawing you are going for a Rosebud fire grate. Could I just ask how you are planning to remove it and how the arch will locate in the firebox. I would like to fit a Rosebud grate in my Britannia when the time comes and, it being a pacific, intended to make it slide out sideways for cleaning, similar to what Jim has done in Australia. Unfortunately that makes fitting an arch quite problematic. I wonder what your thoughts are on this.
Mike
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Post by jon38r80 on Sept 29, 2019 11:10:25 GMT
"It's pretty small but surprisingly strong, being Phosphor Bronze. I just need to make sure not to get it too hot when I'm Silver Soldering in the pipes!"
Why not soft soldering on this occaision after all it is plumbing, I know you dont like it much but it works well on domestic plumbing which goes up to mains pressure. I dont suppoose it will be subjected to much movement either.
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Post by Deleted on Sept 29, 2019 11:32:37 GMT
Yep...I understand how they fit and have already decided on mine. It was just me seeing your drawing wrongly seeing the grey as the outside surface rather than inner....just me looking through tired eyes...
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Post by Roger on Sept 29, 2019 12:57:53 GMT
Hi Roger I see from your drawing you are going for a Rosebud fire grate. Could I just ask how you are planning to remove it and how the arch will locate in the firebox. I would like to fit a Rosebud grate in my Britannia when the time comes and, it being a pacific, intended to make it slide out sideways for cleaning, similar to what Jim has done in Australia. Unfortunately that makes fitting an arch quite problematic. I wonder what your thoughts are on this. Mike Hi Mike, If you look at this model, you can just see how the arch is mounted. The vertical rear plate has a bend at the bottom and you can see one of the two mounting holes below the row of four small ones. There's a clearance hole in that, and an M4 tapped hole in the ashpan for it to screw into. The back plate is fairly thick and the hope is that this will survive for a long time. The top and sides are welded on with short beads of weld so they can be cut off and replaced as necessary. Section showing arch by Timothy Froud, on Flickr The rosebud grate is mounted on a Stainless Steel bar that goes through holes in the ashpan. There's an open sided pivot plate welded to the sides of the grate so it can hook onto the pivot and not fall out when it's tipped up. However, you can lift it up from underneath and then it slips out of the bottom. 20181110_102907 by Roger Froud, on Flickr This picture shows the pivot rod in the middle of the ashpan that the grate pivots on. There's a hole in the middle of the LH end of the ashpan and a pin goes through there to locate in a hole in the lug on the end of the grate to keep it in place. 20181110_223142 by Roger Froud, on Flickr Here's the inside of that. There's a bush on the outside and that allows a lever in the cab to pull the pin. I wanted to be able to release the grate and drop the fire easily but without the grate falling out the bottom. 20181111_202444 by Roger Froud, on Flickr When the grate tips up, it's stopped going too far by the side plates of the arch which are slightly closer together than the width of the grate. Hopefully that all makes sense.
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Post by Roger on Sept 29, 2019 13:09:03 GMT
"It's pretty small but surprisingly strong, being Phosphor Bronze. I just need to make sure not to get it too hot when I'm Silver Soldering in the pipes!" Why not soft soldering on this occaision after all it is plumbing, I know you dont like it much but it works well on domestic plumbing which goes up to mains pressure. I dont suppoose it will be subjected to much movement either. Hi Jon, I don't think it will be hard to Silver Solder if I use my usual method of putting a ring of Silver Solder on the tubes. The joint in the 'Tee' won't melt until it's at a bright red heat, and it barely gets red hot when I use that method. I don't like Soft Solder for this sort of thing, it's very weak.
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Post by delaplume on Sept 29, 2019 13:41:39 GMT
That's a fire "at rest" ......ie loco standing still....When at max effort that view would be incandescent and brilliant white with a continuous roaring sound !!......Some French firemen used to wear welding goggles so as to view the firebed's performance when on the move.....My preferred way is to use your coal shovel to temp. deflect the flames in order to see the bed....( and I don't wear gloves either )
Roger, I'm not sure what a "Diamond" is ??........'er indoors knows but she's not having any !!
Normally the inner firebox wrapper walls are parallel, as is the inner crown.......
The outer wrapper walls will taper outwards and the outer crown sheet upwards as you progress forwards from the footplate end making the total gap bigger and bigger......These join the boiler barrel at it's largest diameter and thus present the largest volume of water to the hottest part of the fire.... This is the best part of a Belpaire-type boilers design...
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Post by Roger on Sept 29, 2019 14:05:19 GMT
That's a fire "at rest" ......ie loco standing still....When at max effort that view would be incandescent and brilliant white with a continuous roaring sound !!......Some French firemen used to wear welding goggles so as to view the firebed's performance when on the move.....My preferred way is to use your coal shovel to temp. deflect the flames in order to see the bed....( and I don't wear gloves either ) Roger, I'm not sure what a "Diamond" is ??........'er indoors knows but she's not having any !! Normally the inner firebox wrapper walls are parallel, as is the inner crown....... The outer wrapper walls will taper outwards and the outer crown sheet upwards as you progress forwards from the footplate end making the total gap bigger and bigger......These join the boiler barrel at it's largest diameter and thus present the largest volume of water to the hottest part of the fire.... This is the best part of a Belpaire-type boilers design... Hi Alan, It will be interesting to see how hot this gets. So is the wider inner firebox at the to only something you see on Model Locomotives then?
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mbrown
Elder Statesman
Posts: 1,779
Member is Online
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Post by mbrown on Sept 29, 2019 16:10:12 GMT
Re: how hot the fire gets.... This summer I wanted to normalise some 1" square steel tubes and thought a good way to do it would be to put them in the firebox on a Talyllyn loco and leave them to cool in the embers overnight. I put them in about 10 mins before the end of the trip, on the down journey where the loco is coasting most of the way. The fire at that point is a lot less hot than when the loco is working. The tubes quickly got up to very bright red, especially where they were standing above the firebed and, in the morning, some had melted into a blob at one end... They were in the fire for maybe half an hour and then cooling in the embers for twelve hours after the fire had been cleaned and drawn back.
So, even when the fire is not being drawn heavily by the blast, it can melt steel if the combination of fire and air is right.
Malcolm
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Post by Roger on Sept 29, 2019 16:40:58 GMT
Re: how hot the fire gets.... This summer I wanted to normalise some 1" square steel tubes and thought a good way to do it would be to put them in the firebox on a Talyllyn loco and leave them to cool in the embers overnight. I put them in about 10 mins before the end of the trip, on the down journey where the loco is coasting most of the way. The fire at that point is a lot less hot than when the loco is working. The tubes quickly got up to very bright red, especially where they were standing above the firebed and, in the morning, some had melted into a blob at one end... They were in the fire for maybe half an hour and then cooling in the embers for twelve hours after the fire had been cleaned and drawn back. So, even when the fire is not being drawn heavily by the blast, it can melt steel if the combination of fire and air is right. Malcolm Hi Malcolm, Sounds like it's going to be mighty hot then. One of my customers uses Inconel 600, so I might have to tap them up and see if I can find who they use. I might have to brace the sides if it sags. All interesting though, I'm sure there's a solution to whatever problems arise.
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Post by Deleted on Sept 29, 2019 17:05:25 GMT
[/quote]Hi Malcolm, Sounds like it's going to be mighty hot then. One of my customers uses Inconel 600, so I might have to tap them up and see if I can find who they use. I might have to brace the sides if it sags. All interesting though, I'm sure there's a solution to whatever problems arise.[/quote]
I recall reading a few articles re 'how hot' it gets in a model firebox. Very, as in, the same temp as full size has been proven with sensors. Julian did give details some time ago. I too will be using Inconel although having said that there seems to be mixed results as to how long a fite arch lasts in a model. Some have said a year or two when using stainless, others are still using an original SS arch after more than a decade. So I guess there must be other factors involved, perhaps the arch design plays a role. I will follow the prototype for position and general shape although I may shorten the length a little in case of hitting the arch with the shovel. I'll look closer on this once I get to that stage..
While talking comparisons with full size, I've just been reading this months ME where there's an interesting letter on this subject. IIRC, it seems weight and tractive effort scale quite well, efficiency is about half on the model. I read lots of comments re, add weight if wanting to do well in IMLEC, seems this may not be the case and that it's the boiler power which is of particular importance, or at least, that's how I read it.
Pete
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Post by Roger on Sept 29, 2019 17:24:58 GMT
Hi Malcolm, Sounds like it's going to be mighty hot then. One of my customers uses Inconel 600, so I might have to tap them up and see if I can find who they use. I might have to brace the sides if it sags. All interesting though, I'm sure there's a solution to whatever problems arise.[/quote] I recall reading a few articles re 'how hot' it gets in a model firebox. Very, as in, the same temp as full size has been proven with sensors. Julian did give details some time ago. I too will be using Inconel although having said that there seems to be mixed results as to how long a fite arch lasts in a model. Some have said a year or two when using stainless, others are still using an original SS arch after more than a decade. So I guess there must be other factors involved, perhaps the arch design plays a role. I will follow the prototype for position and general shape although I may shorten the length a little in case of hitting the arch with the shovel. I'll look closer on this once I get to that stage.. While talking comparisons with full size, I've just been reading this months ME where there's an interesting letter on this subject. IIRC, it seems weight and tractive effort scale quite well, efficiency is about half on the model. I read lots of comments re, add weight if wanting to do well in IMLEC, seems this may not be the case and that it's the boiler power which is of particular importance, or at least, that's how I read it. Pete[/quote] Hi Pete, I think waiting to see what happens is the most sensible strategy. If an arch lasts two or three years, that's not a problem. I can always make it thicker if that will help. Taking part in IMLEC is certainly on my radar, but not until I know the locomotive inside out. As you say, power is not what it's about, but boiler efficiency certainly is going to be vital, especially superheating, and the grate.
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Post by Roger on Sept 29, 2019 18:46:04 GMT
These are the parts for the arch... I started making it larger and thought better of it, hence the reduced size of the rectangle. 20190929_111702 by Timothy Froud, on Flickr The top and side plates are 1.2mm thick while the vertical part is 2mm thick. That's because I think that part is going to last a very long time and the others will come and go as they are burnt out. 20190929_115159 by Timothy Froud, on Flickr I'm just tacking it together to check that I can definitely fit it into the boiler before I weld it all up permanently. 20190929_123725 by Timothy Froud, on Flickr With TIG it's important to either shield the back with Argon or put a block of metal behind to take the heat away. If you don't do this you can get black 'sugaring' on the back. 20190929_152402 by Timothy Froud, on Flickr So this is how it looks with the grate and arch in position. The large gap at the front of the grate is filled by the arch mounting plate. I mistakenly said that the grate touches the arch, but that doesn't happen unless the grate pivots so much that it's vertical. 20190929_154105 by Timothy Froud, on Flickr And this is the view taken through the firehole. You can see why those side plates are on there now. Some gasses will still sneak past, but the bulk of the flow will have to make the detour. 20190929_154159 by Timothy Froud, on Flickr This is what it looks like from the underneath without the grate. 20190929_154516 by Timothy Froud, on Flickr It's easy to unscrew the two bolts and take it out. 20190929_154657 by Timothy Froud, on Flickr Anyway, it all fits, so it was all welded up. This was done without any filler wire. 20190929_160436 by Timothy Froud, on Flickr 20190929_164708 by Timothy Froud, on Flickr 20190929_164716 by Timothy Froud, on Flickr Having fitter the 4mm Anti-roll bar, it was pretty clear that it simply wasn't stiff enough to have any meaningful effect. This is a piece of 6mm Silver Steel being used instead. My dear friend Bill came to the rescue with his Oxy-Acetylene which allowed us to get a nice tight bend round the corner without cracking it. 20190929_094910 by Timothy Froud, on Flickr 20190929_095210 by Timothy Froud, on Flickr Now this is a completely different animal, much stiffer and it will certainly make a difference. Next up are the bearing blocks that engage with the ends of the torsion bar. I've just made some rough Delrin sleeves to test this out, I'll have to make something better engineered for this now it looks viable. 20190929_111939 by Timothy Froud, on Flickr
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Post by andyhigham on Sept 29, 2019 19:27:46 GMT
As any "Sweet Pea" owner will tell you, the inside of the firebox is a very hostile place. the baffle plate in an sweet pea will last an afternoon if made from 3mm mild steel, 3 or 4 afternoons if made from 3mm stainless steel. I have always covered the baffle with a layer of fireclay to prolong it's life. My new firebox baffle will be made from 3mm 310 stainless steel which is supposed to be good for 1150 Deg C
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jma1009
Elder Statesman
Posts: 5,913
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Post by jma1009 on Sept 29, 2019 20:04:31 GMT
Hi Roger,
Very interesting stuff as always...
I would not want to put what is in effect a stainless shield in front of all the firebox tubeplate covering same below the tubes.
You are potentially robbing the firebox of a vital part of it's steam raising and water boiler capability, and which could also have a most adverse affect on water circulation in the boiler and firebox.
If you are going to fit a stainless arch, it ought to be just an arch, without that front shield. Refractive material would be better such as the white backs of gas fires. You ought to consider what the arch is supposed to do in a miniature firebox and if it can realistically burn off the volatiles with any benefit. (In full size the original reason was to reduce smoke output, which is of little consequence to miniature locomotives).
As you know I have my misgivings as to whether a rosebud grate is appropriate as a sensible proposition for a GWR type sloping grate. Very careful firing will be required, and if you get a slip or a bump a thin even fire will end up banked up against the front tubeplate with the rear of the grate completely exposed and uncovered.
The fun of firing GWR style with a traditional sloping grate banking the fire up to the firehole door won't suit a rosebud style grate I presume!
Cheers,
Julian
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Post by Roger on Sept 29, 2019 20:53:38 GMT
I found this neat compact 1/8" BSP silencer on eBay which I thought might be suitable for a water filter from the riding truck. Sucking water through this seems easy enough so I decided to design an inline filter around it. Another motivation for trying this is to see if I can use its slight resistance to flow to prevent back flowing of the Pannier Tanks to the riding truck if the Transfer valve is in the half way position. The other option is to have a non-return valve, but that would have to be a vertical type. It might turn out that it's unnecessary if I use this. We'll see it's fun experimenting! 20190929_214114 by Timothy Froud, on Flickr So here's the design which incorporates the usual union fittings at each end. I've got an M14 x 1 (fine) tap which is ideal for this. Water filter assembly by Timothy Froud, on Flickr
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Post by Roger on Sept 29, 2019 21:09:42 GMT
Hi Roger, Very interesting stuff as always... I would not want to put what is in effect a stainless shield in front of all the firebox tubeplate covering same below the tubes. You are potentially robbing the firebox of a vital part of it's steam raising and water boiler capability, and which could also have a most adverse affect on water circulation in the boiler and firebox. If you are going to fit a stainless arch, it ought to be just an arch, without that front shield. Refractive material would be better such as the white backs of gas fires. You ought to consider what the arch is supposed to do in a miniature firebox and if it can realistically burn off the volatiles with any benefit. (In full size the original reason was to reduce smoke output, which is of little consequence to miniature locomotives). As you know I have my misgivings as to whether a rosebud grate is appropriate as a sensible proposition for a GWR type sloping grate. Very careful firing will be required, and if you get a slip or a bump a thin even fire will end up banked up against the front tubeplate with the rear of the grate completely exposed and uncovered. The fun of firing GWR style with a traditional sloping grate banking the fire up to the firehole door won't suit a rosebud style grate I presume! Cheers, Julian Hi Julian, That's a very interesting point about covering the front of the throat plate, I hadn't thought of that. One thought is that the plate might glow and transfer heat ratiantly to the plate, but that's far from certain. Another thought is to add a series of holes to the plate since it's function is only to support the rest of the arch. There's no reason why I can't do that. The Rosebud grate is in interesting experiment. In the extreme, opening out the holes it becomes a conventional grate when the proportions are the same. In reality, the grate isn't on that steep a slope, I'll be surprised if the fire walks to the front. Still, I honestly have no idea what will happen until I try it. I don't anticipate having a really thin fire, I'd much rather bank it up. That may well mean that the holes in the grate need opening out. We'll see. There are so many novel features all being introduced at once, it will likely be a long time before I can make sense out of what affects what. That's the interest for me, it's so easy to do what everyone else does, and I'd find that boring! I certainly don't expect all of the ideas to work, that's asking too much, but nothing ventured, nothing gained.
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Post by andyhigham on Sept 29, 2019 21:11:39 GMT
if you arrange the filter so the water flows from outside to inside, it is easy to clean by putting an airline on the inside and giving it a blow
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Post by Roger on Sept 29, 2019 21:20:32 GMT
if you arrange the filter so the water flows from outside to inside, it is easy to clean by putting an airline on the inside and giving it a blow That's the way I pictured it being fitted. Yes, that will certainly be easy to clean that way.
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Post by delaplume on Sept 29, 2019 21:50:13 GMT
Sorry Roger but that's not an "arch" as described in section 4 of the "Black Book" ie}-----
"The brick arch is constructed within the firebox, ABUTTING ON THE FIREBOX ON EACH SIDE (My capitals for emphasis ).......It extends from the tubeplate just clear of the bottom row of tubes and is inclined upward....
Projecting into the firebox is the firehole door baffle or deflector plate, positioned so as to incline towards the arch from the firehole in a line slightly below the underside of the arch".....
Thus the arch and deflector plate work in unison to help mix and guide the secondary air and the burning gasses evenly over all the tube holes....
As Julian has indicated what you have produced is more of a shield....
Quote}----"Hi Alan, It will be interesting to see how hot this gets.
So is the wider inner firebox at the to only something you see on Model Locomotives then?
Roger, I think you misunderstand me..........
Have a look at your photo viewed through the firehole door......All that you see there ( to the right----to the left and overhead )is the inner wrapper and runs PARALLEL to the longitudinal centre line as you move forwards from the firehole towards the tubeplate......including those curved corners....
Now the outer wrapper sides and crown sheet are tapered outwards and away from the centreline such that when you get to the equivalent position of the tubeplate the distance between each respective sheet is something like 2 to 3 times what it was back at the firehole......This big gap coupled to the large end of the taper barrel gives the largest possible volume of water positioned at the hottest part of the fire...
IMLEC is all about efficiency--- both of loco and Driver......As many Radiant superheaters as you can fit ....Take driving lessons from any previous winners but do it on a TICH !!..........Why ??.....Because bigger locos can be very forgiving whereas Tich, due to it's diminutive size ---isn't !!
I was visiting Sinsheim show one year and saw a young lad take a coal fired Tich around the complete circuit non stop !!
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Post by Roger on Sept 29, 2019 21:59:32 GMT
Sorry Roger but that's not an "arch" as described in section 4 of the "Black Book" ie}----- "The brick arch is constructed within the firebox, ABUTTING ON THE FIREBOX ON EACH SIDE (My capitals for emphasis ).......It extends from the tubeplate just clear of the bottom row of tubes and is inclined upward.... Projecting into the firebox is the firehole door baffle or deflector plate, positioned so as to incline towards the arch from the firehole in a line slightly below the underside of the arch"..... Thus the arch and deflector plate work in unison to help mix and guide the secondary air and the burning gasses evenly over all the tube holes.... As Julian has indicated what you have produced is more of a shield.... Quote}----"Hi Alan, It will be interesting to see how hot this gets. So is the wider inner firebox at the to only something you see on Model Locomotives then? Roger,I think you misunderstand me.......... Have a look at your photo viewed through the firehole door......All that you see there ( to the right----to the left and overhead )is the inner wrapper and runs PARALLEL to the longitudinal centre line as you move forwards from the firehole towards the tubeplate......including those curved corners.... Now the outer wrapper sides and crown sheet are tapered outwards and away from the centreline such that when you get to the equivalent position of the tubeplate the distance between each respective sheet is something like 2 to 3 times what it was back at the firehole......This big gap coupled to the large end of the taper barell Well, whatever it's called, it forces the gasses to turn towards the rear of the firebox, at least, that's what it's supposed to do in this boiler. I doubt if you could replicate what's happening on full size with regard to deflectors or even arches without running a full Finite Element Analysis for the gas flow in the whole boiler. In the end, this is just a modest attempt to at least stop the gasses going straight down the tubes without transferring much heat to the firebox. Ah, I see what you mean now by that description.
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