Another steam engine shaped object
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I have seen double panels, and other larger sizes, on €&@¥.
I shall try and find a link.
K2
I shall try and find a link.
K2
Found stuff on aliexpress.com item no. 1005003645000707 .
Hope you can find it (using my tablet so don't know how to copy urls, etc.).
K2
Hope you can find it (using my tablet so don't know how to copy urls, etc.).
K2
200mm x 143 mm would cost £25.. + delivery to UK. You could easily trim that to less than 200 mm if you chose, or join one on the side to get 286 wide, then thim to 10mm or so to suit your width?
I have also glued these together with the car exhaust assembly paste. When the ceramics get hot the paste fires into a ceramic.
K2
I have also glued these together with the car exhaust assembly paste. When the ceramics get hot the paste fires into a ceramic.
K2
Hi Doug, A simple option that may suit your boiler could be a unit for a doner kebab cooker. A double plaque burner is available about $70. Looks like it just needs the jet and gas tap.
I'll try and paste a link when I get to my PC.
K2
I'll try and paste a link when I get to my PC.
K2
Hi DOug:
The sites I had found...
Gas Heater Parts Burning Honeycomb Ceramic Plate Infrared Burner Replacement - Bbq Grills - AliExpress
GENUINE ARCHWAY GAS DONNER KEBAB MACHINE CERAMIC RADIANT BURNER HEATER PANEL | eBay
This is a manufacturer in the USA - may be of interest? Wire Mesh Gas Burner - Gas Burner Metal Mesh | Solaronics (solaronicsusa.com)
Burner revision textoutline 5 9 | Solaronics (solaronicsusa.com) - In this it explains the heating ability of each medium. If you ask "nicely", they may supply a free sample the size you want? (I know someone who did that with a Belgian supplier - they sent him 2 burners!).
Here's another burner... PBR03E02-TECHNICAL-BURNERTECH-FRYERS.pdf
I hope some of these links inspire you?
K2
The sites I had found...
Gas Heater Parts Burning Honeycomb Ceramic Plate Infrared Burner Replacement - Bbq Grills - AliExpress
GENUINE ARCHWAY GAS DONNER KEBAB MACHINE CERAMIC RADIANT BURNER HEATER PANEL | eBay
This is a manufacturer in the USA - may be of interest? Wire Mesh Gas Burner - Gas Burner Metal Mesh | Solaronics (solaronicsusa.com)
Burner revision textoutline 5 9 | Solaronics (solaronicsusa.com) - In this it explains the heating ability of each medium. If you ask "nicely", they may supply a free sample the size you want? (I know someone who did that with a Belgian supplier - they sent him 2 burners!).
Here's another burner... PBR03E02-TECHNICAL-BURNERTECH-FRYERS.pdf
I hope some of these links inspire you?
K2
I will send them an inquiry. It looks like you still need to supply the jet and gas tube. Drilling a jet was not a problem. Thanks for the information. I appreciate your time researching this. These projects take on a life of their own. I’m about to set up one of the lower drums on the mill and drill actual holes.
I have been out today, so will have a proper look at the jet size tomorrow, or over the next few days. I think it is 1.2mm for use with 33 mbar propane, but want to check further for HP propane, etc.
K2
K2
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Hi Doug.
Scaling a photo of a jet for the double panel Kebab machine burner: It is a standard 1BA threaded jet: the hole scales from a photo as 1.2~1.25mm diameter for use with LP LPG (Propane: 34.5mBar?) - but I guess the photo may be from a different gas and pressure... not the correct one! However, if it is of the correct jet/gas/pressure... I have estimated from my tables of jet sizes versus gas and pressure that it is a 0.049" jet: which would deliver about 16500BTU/hr (4.8kW) of gas.... Commercial "kebab" machines are rated at 7.3kW for a 3-panel grill to 16.5kW for a 5 panel grill, so there is obviously some variation, but maybe they are looking around the 3.5kW for a double panel burner?
To use Propane at 20psi, I should need an equivalent gas-power jet: which would be 0.018" diameter drill. So this is comparable to my double panel burner experience:
Now checking my notes of the "double plague" burner I made, I estimated a 0.55mm jet, but finally settled on a 0.47mm jet - for use at 15~20psi Propane: This was into a 16mm bore mixer tube: (I didn't make a note, but I think this gave me better versatility for turning down the gas power without spoiling the gas-air mixture - something my "customer" wanted.
His 9" boiler had very limited flue-tube CSA. Thinking ahead to my burner in his boiler, I was expecting the limitations of the flue tubes to cause back-pressure that richens the mixture at "max gas pressure" (effectively reducing the pressure differential between air-intake and burner), so I thought I needed a way to allow him to open/adjust the air holes as suited his boiler. I also decided to reduce the "designed" air holes by masking most of 1 hole, so I was on a slightly richer gas mixture: This gave a more uniform colour across the burner, which should lead to a longer life of ceramic. I remember the final condition had a 1/2" or so of blue (CO combustion) flame above the ceramic. As I didn't have the boiler (to study the back-pressure from exhaust restriction in flue tubes) to test the final condition in-situ, I decided a slightly richer mixture - with a sliding collar on the air holes - would give my customer the flexibility to weaken or richen the mixture as suited the final application and "power" setting the customer would be using.
For control of larger burners, I think it practical to adjust the gas pressure, so the system is "balanced" at full throttle of the engine. Then this can be reset at any time by the fireman to the known "max pressure" for running. Of course, it is reasonable then to reduce the gas pressure for "below max power" running of the engine, and gas pressure control on a pressure regulator is a repeatable way of doing this. As well, for more rapid raising of steam initially, the gas pressure can be turned to "full" setting (for stability of flame/burner inside the boiler) and the power should then be suitably limited by the jet size (to avoid overheating the ceramic). For your Yarrow boiler design, visible flames should not reach within 5 mm of ANY metal surface (that prevents full CO combustion), but there is a very good space if running at "max gas" does cause some top flame ( up to maybe 3/4"?) above the burner. Such combustion conditions appear to be "clean enough" so my CO alarm does not sound, while keeping the ceramic temperature from being too high (which causes early-life failure of the ceramic - cracking - and possible dangerous flash-back combustion).
Here is a Yarrow boiler design from a book - similar to your boiler: It shows the fire between the bottom tanks.
Hope this is useful?
K2
Scaling a photo of a jet for the double panel Kebab machine burner: It is a standard 1BA threaded jet: the hole scales from a photo as 1.2~1.25mm diameter for use with LP LPG (Propane: 34.5mBar?) - but I guess the photo may be from a different gas and pressure... not the correct one! However, if it is of the correct jet/gas/pressure... I have estimated from my tables of jet sizes versus gas and pressure that it is a 0.049" jet: which would deliver about 16500BTU/hr (4.8kW) of gas.... Commercial "kebab" machines are rated at 7.3kW for a 3-panel grill to 16.5kW for a 5 panel grill, so there is obviously some variation, but maybe they are looking around the 3.5kW for a double panel burner?
To use Propane at 20psi, I should need an equivalent gas-power jet: which would be 0.018" diameter drill. So this is comparable to my double panel burner experience:
Now checking my notes of the "double plague" burner I made, I estimated a 0.55mm jet, but finally settled on a 0.47mm jet - for use at 15~20psi Propane: This was into a 16mm bore mixer tube: (I didn't make a note, but I think this gave me better versatility for turning down the gas power without spoiling the gas-air mixture - something my "customer" wanted.
His 9" boiler had very limited flue-tube CSA. Thinking ahead to my burner in his boiler, I was expecting the limitations of the flue tubes to cause back-pressure that richens the mixture at "max gas pressure" (effectively reducing the pressure differential between air-intake and burner), so I thought I needed a way to allow him to open/adjust the air holes as suited his boiler. I also decided to reduce the "designed" air holes by masking most of 1 hole, so I was on a slightly richer gas mixture: This gave a more uniform colour across the burner, which should lead to a longer life of ceramic. I remember the final condition had a 1/2" or so of blue (CO combustion) flame above the ceramic. As I didn't have the boiler (to study the back-pressure from exhaust restriction in flue tubes) to test the final condition in-situ, I decided a slightly richer mixture - with a sliding collar on the air holes - would give my customer the flexibility to weaken or richen the mixture as suited the final application and "power" setting the customer would be using.
For control of larger burners, I think it practical to adjust the gas pressure, so the system is "balanced" at full throttle of the engine. Then this can be reset at any time by the fireman to the known "max pressure" for running. Of course, it is reasonable then to reduce the gas pressure for "below max power" running of the engine, and gas pressure control on a pressure regulator is a repeatable way of doing this. As well, for more rapid raising of steam initially, the gas pressure can be turned to "full" setting (for stability of flame/burner inside the boiler) and the power should then be suitably limited by the jet size (to avoid overheating the ceramic). For your Yarrow boiler design, visible flames should not reach within 5 mm of ANY metal surface (that prevents full CO combustion), but there is a very good space if running at "max gas" does cause some top flame ( up to maybe 3/4"?) above the burner. Such combustion conditions appear to be "clean enough" so my CO alarm does not sound, while keeping the ceramic temperature from being too high (which causes early-life failure of the ceramic - cracking - and possible dangerous flash-back combustion).
Here is a Yarrow boiler design from a book - similar to your boiler: It shows the fire between the bottom tanks.
Hope this is useful?
K2
I see that the entire boiler is enclosed. I was planning to leave the ends of the drums visible for convenience adding the site glass, injector and blow down ports. As long as I have to tin smith an enclosure, I can see the use of sliding or rotating louvre system and a larger chimney. I’ve seen several boiler examples with D shaped lower drums. I plan to stay with simple round tubes. I have a test pipe ready to do a test cut using an end mill. Today I am convincing two steam cylinders to balance. I’m redoing slide valve rod for the second cylinder to use a left hand thread. I naively thought I could set the spacing and install them as a unit. The left hand tap and die just arrived and it should be a quick fix.
The adjustable propane regulator will work nicely for the burner although I will likely need to use the larger tank. I did not go with a supper heater because I was concerned if the engines would take the high temperatures.
The adjustable propane regulator will work nicely for the burner although I will likely need to use the larger tank. I did not go with a supper heater because I was concerned if the engines would take the high temperatures.
Hi Doug.
Just my thoughts on your plans - of course you can make- up your own mind, based on lots of ideas, not just mine.
K2
Just my thoughts on your plans - of course you can make- up your own mind, based on lots of ideas, not just mine.
- I would keep boiler ends enclosed, but the water gauge should pass through the cleading so it is outside and always visible.
- I'm not sure I understand what your sliding louvre system is for. But a large chimney will be needed, I GUESS 2 inches is better than 1 1/2"? For a single page sized burner, I have a boiler that my Father had to change from 1" => 1 1/2". Hence I guess 2" for yours?
- I have no idea between D-shaped and cylindrical bottom drums. But my boiler-making book advocates D-shaped, though the flat part may be stressed more by the internal pressure, while the hoop stress on cylindrical pipes will put uneven loading onto the water tubes..... I do not have the knowledge nor ability to do a FEA on the alternatives. Just make sure the silver soldering is sound, with correct clearance between water tubes and larger tubes. I suggest about 55% silver solder, as it is better to generate fillets and make stronger joints. But other professional advice may give better answers. (I am just an amateur copper-smith!).
- Having the ability to finely adjust the valve timing between the 2 cylinders sounds like "a proper job". Pity it didn't work with your solid linkage. I know all my stuff doesn't have the accuracy for "absolute" sizing, so everything needs to be a bit adjustable. Welcome to the real world!
- I advocate a super-heater tube. Even a single horse shoe loop around the inside of the boiler space will make a huge difference to the performance of the engine, in my experience. I always fit super-heaters, even if not complex big ones. It clearly reduces the condensate in the model cylinders, which can be very problematic (hydraulic lock!), especially during warming the engine. Model engines have such tiny spaces at the cylinder ends.... unless you fit auto-drain-valves or something? Using a good steam oil, you should be OK for normal model use, if you have a superheater.
- Using a gas regulator has made controlling the firing of my boilers much easier.
K2
As I get the actual boiler built, I will post my ideas for the enclosure. Enclosed it is. If I’m going through this effort, I should go for efficiency. I have a couple ideas for a super heater and will post sketches. On the engine, the solid bar is actually threaded onto the end of the first stage. The problem was that all the threads are right hand so turning the rod does not affect the length so the outer end will be left hand. I’m ordering 55% silver solder. I have 65% silver I use for instrument repair, but not enough for the job. I also plan on stays for each drum.
Hi again Doug, a new day dawns - colder today. Do you have a means of dishing the boiler ends? - Domed end plates are hugely stronger than flat ones, and eliminate the need for stays.
I've lost the thread with more information of this boiler... Was it on a different thread somewhere, or am I simply getting a bit demented? (Or maybe I always was a bit that way?). I found my Tube calculations - for 50psi NWP:
IF Flat ended:
2.5" dia end plate with single centre stay: Min thickness = 0.065"
1.125" dia end plate without stays: Min thickness = 0.055"
So a dished end without stays: Spherical radius 2" or below: Min thickness = 0.040": But at 4.5" spherical radius: Min thickness = 0.090"
Combining the two:
Size of stay:
If Phosphor Bronze >1.6mm diameter "at root of thread":
BUT: the stress concentration factor at thread root is ~3... (My best estimate!) so you need at least 2.8mm root diameter (M4): I don't know what you plan? I suggest nothing smaller than 4BA, or 3/16" x 32tpi? - Or similar "US" fine thread? (Is that UNF where you are?). I.E. a root diameter at least 0.128" diameter.
Incidentally, Stainless steel comes in many grades, but for sake of argument, if using "bottom draw" stock of unknown quality you should consider it as the same strength as Phosphor Bronze. NOT better (unless a known better grade).
I hope this helps you decide on your design?
K2.
I've lost the thread with more information of this boiler... Was it on a different thread somewhere, or am I simply getting a bit demented? (Or maybe I always was a bit that way?). I found my Tube calculations - for 50psi NWP:
IF Flat ended:
2.5" dia end plate with single centre stay: Min thickness = 0.065"
1.125" dia end plate without stays: Min thickness = 0.055"
So a dished end without stays: Spherical radius 2" or below: Min thickness = 0.040": But at 4.5" spherical radius: Min thickness = 0.090"
Combining the two:
- For the 2.5" ends: Unstayed flat >0.125" thick, dished to 4.5" radius >0.090" thick: dished to 2" radius > 0.040" thick, Single stay >0.065" thick.
- For the 1.25" ends: Unstayed flat >0.055" thick: If you wanted a single stay the end plate: >0.030" thick.
Size of stay:
If Phosphor Bronze >1.6mm diameter "at root of thread":
BUT: the stress concentration factor at thread root is ~3... (My best estimate!) so you need at least 2.8mm root diameter (M4): I don't know what you plan? I suggest nothing smaller than 4BA, or 3/16" x 32tpi? - Or similar "US" fine thread? (Is that UNF where you are?). I.E. a root diameter at least 0.128" diameter.
Incidentally, Stainless steel comes in many grades, but for sake of argument, if using "bottom draw" stock of unknown quality you should consider it as the same strength as Phosphor Bronze. NOT better (unless a known better grade).
I hope this helps you decide on your design?
K2.
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Hi Doug,
I tried (and failed!) to find strength info on silver solders, to suggest the 65% silver wasn't as strong as other grades, and propose "the best". BUT failed.
On Spinning ends. I thought you may go that route, when you appreciated how strong these can be. What radius do you expect for the 2.5" Top drum ends? If hemi-spherical, then it is 1.25", but if elliptical a bit harder to calculate. And Hoop stress is very dependant on internal radius (max). => define local minimum thickness. (I assume the spinning will thin the material slightly).
K2
I tried (and failed!) to find strength info on silver solders, to suggest the 65% silver wasn't as strong as other grades, and propose "the best". BUT failed.
On Spinning ends. I thought you may go that route, when you appreciated how strong these can be. What radius do you expect for the 2.5" Top drum ends? If hemi-spherical, then it is 1.25", but if elliptical a bit harder to calculate. And Hoop stress is very dependant on internal radius (max). => define local minimum thickness. (I assume the spinning will thin the material slightly).
K2
My air compressor has a compound curved dome. Given it’s 12” diameter the actual domed section is 10” with 2” used to transition the dome into the main cylinder (I’ll post a sketch). Based on this design, I planned on 2” of the dome at .4” protrusion. The remaining .5” to create the blend into the cylinder.
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Thanks Douģ. I shall try and deduce the largest radius of curvature for the top drum end dome, from your sketch.
Might take a few days though, as my wife is having an operstion tomorrow, so I am spending a lot of time on other jobs (washing and ironing, etc.).
K2
I will be sending good thoughts for you and your wife.
I have the first stage of the little engine working nicely. The original aluminum cross slide has a lot of play and clunks. I will deal with it after I finish the second stage. It has a lot of torque with just one cylinder. The wobbly flywheel was a base for wind chimes and I decided to buy an actual flywheel casting. As for the boiler, I’m just making an alignment tool to keep the tubes straight so I can make one of the lower drums so I have plenty of time. It will take me a few week to cut pipes, tubes and make jigs.
I have the first stage of the little engine working nicely. The original aluminum cross slide has a lot of play and clunks. I will deal with it after I finish the second stage. It has a lot of torque with just one cylinder. The wobbly flywheel was a base for wind chimes and I decided to buy an actual flywheel casting. As for the boiler, I’m just making an alignment tool to keep the tubes straight so I can make one of the lower drums so I have plenty of time. It will take me a few week to cut pipes, tubes and make jigs.
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Mechanicboy
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DJoksch..
With more thin water pipes, more steam is produced than smaller numbers of thick pipes. This means that you have a larger heating surface to heat the water to steam quickly and get greater pressure. Yarrow boiler is efficient to produce more steam pressure, but must supply with preheated water in relation to water consumption as the Yarrow boiler there is not much water in the upper boiler that it can quickly run out of water. Use electronically monitored water level to supply via feed water pump + bypass valve controlled by servo connected to Boiler with automatic boiler water level control system.
With more thin water pipes, more steam is produced than smaller numbers of thick pipes. This means that you have a larger heating surface to heat the water to steam quickly and get greater pressure. Yarrow boiler is efficient to produce more steam pressure, but must supply with preheated water in relation to water consumption as the Yarrow boiler there is not much water in the upper boiler that it can quickly run out of water. Use electronically monitored water level to supply via feed water pump + bypass valve controlled by servo connected to Boiler with automatic boiler water level control system.
Doug, you'll need some oilers on the crank journals.
And Mech-boy is right, you should plan a feed- water heater coil - in the post boiler exhaust. I.e. outside the water tube array. (Superheater loop inside the water-tube array). And it will need a continuous water feed pump. I arrange my boats to have an engine driven pump, so faster speed =more water.
K2
And Mech-boy is right, you should plan a feed- water heater coil - in the post boiler exhaust. I.e. outside the water tube array. (Superheater loop inside the water-tube array). And it will need a continuous water feed pump. I arrange my boats to have an engine driven pump, so faster speed =more water.
K2
