Model boiler design information

[Bentwings]

Hi Byron, You sound to be very productive with your ideas. Just a couple I want to debate:

1. If you are planning on just balsa wood for insulation, that will be all you need for conductive losses, if around 1/2" or more. So I can't see any reason for the car exhaust stuff? But your choice. However, you should consider radiation losses (the radiant heat shines straight through the balsa or other until it hits the stainless steel). So if you polish the aluminium tube that will be excellent, or wrap in aluminium foil. Either will reduce radiant losses significantly compared to doing nothing with the surface of the tube.
2. My biggest issue is the use of aluminium with steam. I thought this was always a "NO! NO!" because water doesn't corrode aluminium rapidly, yet STEAM does, especially at elevated temperature. And when it does it gives off hydrogen, which has the potential of being very explosive... So although domestic pressure cookers with steam at up to 15psi exist and are safe to use, please check what higher temperature steam will do to your boiler.
3. A quick check suggests you need >5.2kW of steam to extract if the engine needs 50psi at1000rpm (and a generator to load the engine). Of course, at 20psi you'll only need 3kW... of steam power. Allowing for losses (maybe a couple of hundred W if well lagged?) you'll need more than those figures from the heaters. Unless I have screwed-up the calculations? (I had to correct some glitches in my spreadsheet). What did you calculate?
4. What "penetrations" will you make in the outer shell cylinder? (If any?) I can see a design where all the safety valves, water gauge connections, steam extraction, water-feed, etc. is done via the end plates, so the boiler shell is "without penetrations". but that is unusual. Mostly there is a steam dome (to collect steam high above the spraying surface of water), water feed, connection for safety valve, etc. so that affects the hoop stress calculations and comparison of the design with permissible safety limits. ASME uses a "Standard" value of 3.3 for the SCF if ANY penetrations exist in a boiler shell or tube. With this SCF (assuming at least 1 penetration) for your boiler at 50psi, I get a hoop stress of 1902psi and I think the permissible stress will only be 1141psi for aluminium..? which I reckon is a FOS of less than 5. But the regulations normally require a FOS of 8? But I may be wrong? If there are no penetrations in the shell tube, then the FOS is over 15 - which is good. - What have you calculated? - I am keen to be sure my calcs are sensible, and if you have close results I'll be happy.

Thanks,
K2

as I noted I spilled a full glass of water on my entire pile of notes. I had a big mess of drying papers of course the super fine black marrrs I used sonic an readily see are now some kind of artwork don’t laugh too hard my kitty was running all over probably thinking I was sbout to explode. So I’m rebuilding the mess the aluminum is quite strong enough when you consider water pressure is around 45-50 psi in RV WATER TANKS THAT ARE PRETTY THIN WALLED AN INEXPERIENCED GUY ONCE BLEW ONE UP WITH 120 psi air very lucky nobody got hurt. It was a 5?gallon tank . I have no idea what he was doing testing with shop air . I did some basic stress calculation observing that the screws holding the end caps in might subject the end of the main tube to to a testing effect which is where overlapping plates you see in bridge construction comes from. By using the through to tod I was able to load its bolts in tension preventing any real bending ofvthe end cap which is unlikely anyway we often lift race care engine with a 4 bolt plate on the carb studs. These are 1/4 inch to 5/16” engines can weigh 1,000 pounds And I’ve never seen any of these bolts pull out or break the lifting plates are often just loosely held on with hand installed nuts so the things are poorly mounted a 1/4” gr 8 bolt is amazingly strong so I’m pretty confident ther won’t be issues there are no closed copper tubes so collapse as you pointed out won’t happen they are the just to help circulation and provide heating surface area. As far as heater go they are stainless tubes surrounding the elements . I don’t have a way of measuring wall thickness but I have to go with previous experience here the same things were used to heat platic mold in molding while not submerged or pressurized at lest not measurable I don’t see any problems . I know it seems like a low heating capacity and I may be taken to task here we will se . This boiler holds less than 3/4 gallon subtracting volumes of all the submerged parts there just it’s is not a lot of water in it which is why I need to come up with a good fill pump . I have the parts to do it I just have not got that far yet . It’s hard to believe how fast and how far this hobby has advanced for me . I “0” when I made the decision yet 50+ years of model airplanes and who bows how many years in sports I played senior base ball untill I was 72 And of course my life career. I appreciate any challenges and comments . I consider them learning experiences. Every spect of this hobby is new and bears investigating . I’m trying to document things I do if for no reason other than have w page to look at and say yep I considered that and here is what I did . When you say hey you need to calculate this or that , I most certainly will look into it . Because it’s part of learning sbout this hobby. I’m building on your experiences. As I noted I’m open to debate and out right challenges
I’m just having a good time already . Sorry I got carried away. I have an INT blood yet so I must go for now . The engine is supposed to be delivered today I just checked tracking and it’s out for delivery . I’ll get back later thanks

byton

 

[Steamchick]

Aha! - the wonders of Google! It seems that corrosion of aluminium in steam is a real problem at 400C. but maybe at 200C you'll be OK?
CORROSION OF ALUMINUM AND ITS ALLOYS IN SUPERHEATED STEAM (Technical Report) | OSTI.GOV
K2

 

[Steamchick]

Hi Byron,
Perhaps I have mis-understood something. Can you supply overall dimensions of this 3/4gallon boiler?
I had read 44" diameter as 4" diameter - as you suggest you sometimes double poke characters and spell checker can't spot the error. So is it 44" diameter? Seems wrong for 3/4 gallon? I assume you are on "USA short gallons of 5 pints" (or something?) so 3/4 gallon volume of boiler would only be 3.75pints, or 108.3cu.in. On 4" diameter, this would be 8 1/2 in long. On a 44" diameter this would be 0.3" long... But then you talk about RV tanks and things and I wondered if you were planning on a 44" diameter boiler after all?

Dan, you suggested links to UK code information, but unfortunately I can't get it to link to anything:

I found the answer to my question about UK boiler code at the end firebird's small boiler thread reply #395 by SandyC. Home Model Engine Machinist Forum
Here is another good thread about UK boiler rules.
http://www.homemodelenginemachinist.com/index.php?topic=1886.0
Cheers Dan

Any chance you can add an internet link more directly to the UK codes?

Thanks, K2

 

[Bentwings]

Aha! - the wonders of Google! It seems that corrosion of aluminium in steam is a real problem at 400C. but maybe at 200C you'll be OK?
CORROSION OF ALUMINUM AND ITS ALLOYS IN SUPERHEATED STEAM (Technical Report) | OSTI.GOV
K2

I did forget to note regarding corrosion. Being a cruise boater I’m well aware of marine corrosion . To that end I have a screw in anode exactly as was used on my cruiser also I have two magnesium rods I can make into more or longer anodes. I don’t like machining magnesium where steel is machined as it it means extreme clean up measures. So I’ll keep it to a minimum and just order an additional anod it’s a npt thread so not a real issue but just another hole to fill .
I had thought about a steam dome but I think I’ll just use a manifold and keep the holes to a minimum in the boiler the engine has more or less built in intake and exhaust ports so I don’t think there will be much of an issue there . The med INR is done . What a wonderful way to get around clinic visits . The nurse come right to my door bringing her kit in so I have my own clinic. Even doc visits are now in home, just like the old days. It’s an incredible thing as I don’t have to depend on anyone to drag me around. There also is a med bus I can take if necessary but it’s much more inconvenient. Once I get he Evike conversion done in the spring I can ride to any clinic visits necessary .those will be few. UPS engine delivery is still on schedule up to 9 PM. I had one of those a couple days ago

I tried to get som ammonia today Walmart is out cub foods is out local grocery store is out. Even local Walgreens is out so I ordered from Amazon sticker shock I used to get a bottle for under a dollar at grocery store $9 now including shipping even with additional items to bring the value up for free shipping I may just put water in bath tub and let the balsa soak over night it doesn’t work as well but if I’m carefull I think ITV will bend with out cracking . Super glue fixes it easy enough however. I still haven’t gotten over $50 for a tap and die plus shipping
In reviewing heaters since there will be holes for both sizes I’m going to order another big heater and use both . Since I’ll use two separate circuits in the house I think I’ll be ok

thanks for the comment on the header wrap I’ll delete that I don’t like it anyway works on cars but leave it in the car shop . Hanks to internet search it confirmed that I’ll have about 5/8 gallon of water in the boiler the copper tubes and bulk heads are only a couple ounce of water as I thinned the bulkheads up to a minimum I may add an over all length just to give a bit more volume it will be easier to do it now than later.
When we cut the tube length I’ll polish it to reduce the micro surface area so it will radiate less heat . It’s surprisingvwhatvsurfacecfinish Does

byron

Byron

 

[Steamchick]

Hi Byron, will the boiler be a vertical cylinder, or horizontal cylinder? You'll need a good 1" between the highest water level and the hole for steam take-off. So for your size of boiler the vertical placement gives a better distance from max water to steam dome. It is usual to have a perforated plate or something to catch droplets from getting into the steam stream, some sort of water-steam separator anyway in the steam dome. Wet steam jams engines! That's the main reason for post-boiler heating/drying on models. Hydraulic lock damages engines! But if you have any side penetrations in the cylindrical shell they must be properly bushed - of a design to carry all the hoop stress that can't be a hoop because of the penetration.
I am concerned that your unconventional design will miss certain necessary features that are "conventional" - because history tells us they make a better boiler.
Cheers,
K2

 

[Steamchick]

Oh, the safety valve should connect directly to the boiler, not be stuck on a manifold.
K2

 

[Bentwings]

Hi Byron,

I did forget to note regarding corrosion. Being a cruise boater I’m well aware of marine corrosion . To that end I have a screw in anode exactly as was used on my cruiser also I have two magnesium rods I can make into more or longer anodes. I don’t like machining magnesium where steel is machined as it it means extreme clean up measures. So I’ll keep it to a minimum and just order an additional anod it’s a npt thread so not a real issue but just another hole to fill .
I had thought about a steam dome but I think I’ll just use a manifold and keep the holes to a minimum in the boiler the engine has more or less built in intake and exhaust ports so I don’t think there will be much of an issue there . The med INR is done . What a wonderful way to get around clinic visits . The nurse come right to my door bringing her kit in so I have my own clinic. Even doc visits are now in home, just like the old days. It’s an incredible thing as I don’t have to depend on anyone to drag me around. There also is a med bus I can take if necessary but it’s much more inconvenient. Once I get he Evike conversion done in the spring I can ride to any clinic visits necessary .those will be few. UPS engine delivery is still on schedule up to 9 PM. I had one of those a couple days ago

I tried to get som ammonia today Walmart is out cub foods is out local grocery store is out. Even local Walgreens is out so I ordered from Amazon sticker shock I used to get a bottle for under a dollar at grocery store $9 now including shipping even with additional items to bring the value up for free shipping I may just put water in bath tub and let the balsa soak over night it doesn’t work as well but if I’m carefull I think ITV will bend with out cracking . Super glue fixes it easy enough however. I still haven’t gotten over $50 for a tap and die plus shipping
In reviewing heaters since there will be holes for both sizes I’m going to order another big heater and use both . Since I’ll use two separate circuits in the house I think I’ll be ok

thanks for the comment on the header wrap I’ll delete that I don’t like it anyway works on cars but leave it in the car shop . Hanks to internet search it confirmed that I’ll have about 5/8 gallon of water in the boiler the copper tubes and bulk heads are only a couple ounce of water as I thinned the bulkheads up to a minimum I may add an over all length just to give a bit more volume it will be easier to do it now than later.
When we cut the tube length I’ll polish it to reduce the micro surface area so it will radiate less heat . It’s surprisingvwhatvsurfacecfinish Does

byron

Byron

I have to be carefull as I forget we have international friends
Perhaps I have mis-understood something. Can you supply overall dimensions of this 3/4gallon boiler?
I had read 44" diameter as 4" diameter - as you suggest you sometimes double poke characters and spell checker can't spot the error. So is it 44" diameter? Seems wrong for 3/4 gallon? I assume you are on "USA short gallons of 5 pints" (or something?) so 3/4 gallon volume of boiler would only be 3.75pints, or 108.3cu.in. On 4" diameter, this would be 8 1/2 in long. On a 44" diameter this would be 0.3" long... But then you talk about RV tanks and things and I wondered if you were planning on a 44" diameter boiler after all?

Dan, you suggested links to UK code information, but unfortunately I can't get it to link to anything:


Any chance you can add an internet link more directly to the UK codes?

Thanks, K2

im terribly sorry I completely missed that gaffe the tube is 4” 3/16 wall tube initially 14” long but I think I’ll add an inch as the tube is 18” right now.
I have to laugh about this one the first time I got to travel to Europe we went out for dinner it’s bad enough I don’t have a second language but we were sitting in a local pub the waiter came to take or dinner request he asked if we would like a beer I like a dumb American had no idea what to ask for but a guy across from us had thi great big tall glass it was huge some places here have a yard of beer glass similar to this so I said something like the gentleman over there has I don’t know how much it was but it lasted a whole evening. I had to watch out of the corner of my eye on how to hold the thing . It was good we were on foot so I’m glad we were not driving .
Ok I’ve got to stop I’m making too many mistakes . If the engine arrives I’ll take a picture and post later.
Byron

 

[Bentwings]

Hi Byron, will the boiler be a vertical cylinder, or horizontal cylinder? You'll need a good 1" between the highest water level and the hole for steam take-off. So for your size of boiler the vertical placement gives a better distance from max water to steam dome. It is usual to have a perforated plate or something to catch droplets from getting into the steam stream, some sort of water-steam separator anyway in the steam dome. Wet steam jams engines! That's the main reason for post-boiler heating/drying on models. Hydraulic lock damages engines! But if you have any side penetrations in the cylindrical shell they must be properly bushed - of a design to carry all the hoop stress that can't be a hoop because of the penetration.
I am concerned that your unconventional design will miss certain necessary features that are "conventional" - because history tells us they make a better boiler.
Cheers,
K2

I didn’t see the first part above . It will be horizontal .
Byron

 

[Steamchick]

Do you have a sketch/drawing of how you plan all the necessary fittings?
K2

 

[Bentwings]

Happy days are here my engine just arrived! My kitty is helping me open the box! It’s full of bubble wrapped parts ! It will take hours to un wrap all of them ! I see a pack of instruction and an assembly drawing and bill of materials I think there are about 200 individual parts lots of small stuff .
I can’t say enough for chilertern. They have been just great to work with. I get nearly same day response from emails I was also able to call directly it would have been a horribly expensive call except for AT&T set up unlimited over seas calls for $15 per month that I can end by just calling them so far I can’t complain about anything even my bank cooperated and released fun’s as requested. No charge
Back to checking thing out

Byron

 

[Bentwings]

Do you have a sketch/drawing of how you plan all the necessary fittings?
K2

That’s pretty close I have Teflon o rings or deed as well as Rodman o ring that ar softer .

 

[Bentwings]

I carefully read this over then posted it now I see errors that weren’t there

 

[Bentwings]

I carefully read this over then posted it now I see errors that weren’t there

Ok m bluish hoizntal I’ve added an inch so it needs 15” long 4” of 3/26” wall . I don’t have a steam dome per se as this in my mind would be either weld on or bolt on I really don’t vent to weld as first I’d have to crate shape then welding right in the middle of the tube I think would create a weak spot. It’s 6061 t6 aluminum but welds almost invariably creat a weaker area . That’s why I also elected to make a bolt together assembly bolt on means more holes to leak in my mind I’m not worried about pullout I had planned to have the boiler sit with one nd slightly higher than the o the so a high point to take steam out. The blow down or cylinder cleaner was something I had a question about. My very early trace was behind various steam engines yes I’m that old I often wondered why there was a huge blast of steam right before the train started moving I do know about hydraulic lock from auto racing saw it a fe times we never had issues . The hemi engines have the exhaust ports low on the heads so simply baring the engine over in reverse rotation automatically cleared cylinders . Today’s top fuel dragsters ar very near hydra lock just because of the enormous amount of fuel that goes into them, some time a cylinder misfires so the fuel doesn’t ignite then you see the big fireball as parts go flying we burned a lot of pistons but never hydra locked a motor . So I need to maybe know some tech on how to plumb a blow down Ipipe I might even be into a solenoid operated one just to keep fingers out of the way. I’ll have a filter luberacator pressure gage like an air compressor has at this point. I was thinking about sort of dehumidifying the steam. But I can see how condensation could get in and cause issues . I just got my steam engine kit today . It has some kind of intake manifold to use auto terms, in fact two as it’s really two engines connected together I’m a little concerned about timing as I did not see anyting in the assembly instructions . I haven’t un wrapped all the parts yet . There are a lot of them . I thought there might be some kind of drain in the manifolds I may have create one or two . As I get more into the assembly I’ll know more . There are some castings I’d like painted so I’ll dig them out tomorrow . I can see I’ll need an aluminum mounting plate to keep everything in alignment that’s not an issue I have Lenny of aluminum platsaround I really did not want to hard this I not a very big engine I’m guessing but 6”x6” line the piping as it always seems to get ugly bends in te wrong places but I may have to compromise . I’ll just make a spare set of lines if necessary . We have flaring tools to do about anything required. I was goingvto use AN 3 or 4 fittings but I think they will be too big and as pretty color as they are I ghnkbtheyvwill clutter it up . It’s getting harder to keep up with typing almost like saying … time to post and answere questions later. I’ve had issues where the spell check tries to out guess me and inserts it’s own words even if I preview which I do but this dumb vision issue bites me occasionally
Buron

 

[Bentwings]

Ok m bluish hoizntal I’ve added an inch so it needs 15” long 4” of 3/26” wall . I don’t have a steam dome per se as this in my mind would be either weld on or bolt on I really don’t vent to weld as first I’d have to crate shape then welding right in the middle of the tube I think would create a weak spot. It’s 6061 t6 aluminum but welds almost invariably creat a weaker area . That’s why I also elected to make a bolt together assembly bolt on means more holes to leak in my mind I’m not worried about pullout I had planned to have the boiler sit with one nd slightly higher than the o the so a high point to take steam out. The blow down or cylinder cleaner was something I had a question about. My very early trace was behind various steam engines yes I’m that old I often wondered why there was a huge blast of steam right before the train started moving I do know about hydraulic lock from auto racing saw it a fe times we never had issues . The hemi engines have the exhaust ports low on the heads so simply baring the engine over in reverse rotation automatically cleared cylinders . Today’s top fuel dragsters ar very near hydra lock just because of the enormous amount of fuel that goes into them, some time a cylinder misfires so the fuel doesn’t ignite then you see the big fireball as parts go flying we burned a lot of pistons but never hydra locked a motor . So I need to maybe know some tech on how to plumb a blow down Ipipe I might even be into a solenoid operated one just to keep fingers out of the way. I’ll have a filter luberacator pressure gage like an air compressor has at this point. I was thinking about sort of dehumidifying the steam. But I can see how condensation could get in and cause issues . I just got my steam engine kit today . It has some kind of intake manifold to use auto terms, in fact two as it’s really two engines connected together I’m a little concerned about timing as I did not see anyting in the assembly instructions . I haven’t un wrapped all the parts yet . There are a lot of them . I thought there might be some kind of drain in the manifolds I may have create one or two . As I get more into the assembly I’ll know more . There are some castings I’d like painted so I’ll dig them out tomorrow . I can see I’ll need an aluminum mounting plate to keep everything in alignment that’s not an issue I have Lenny of aluminum platsaround I really did not want to hard this I not a very big engine I’m guessing but 6”x6” line the piping as it always seems to get ugly bends in te wrong places but I may have to compromise . I’ll just make a spare set of lines if necessary . We have flaring tools to do about anything required. I was goingvto use AN 3 or 4 fittings but I think they will be too big and as pretty color as they are I ghnkbtheyvwill clutter it up . It’s getting harder to keep up with typing almost like saying … time to post and answere questions later. I’ve had issues where the spell check tries to out guess me and inserts it’s own words even if I preview which I do but this dumb vision issue bites me occasiona

I do appreciate note and comments .
Byron

 

[Bentwings]

I do appreciate note and comments .
Byron

I’m really frustrated. I carefully reviewed my my last post, made a couple corrections then posted. The phone spell check do its own thing and built in words I never put in and messed up he context . I though I missed a couple words but it was correct when I hit the post button . It’s bad enough I have my own issues, I don’t need extra issues . I’ll search and see if there is some way to either disable this or get around it.
byron

 

[Bentwings]

I’m really frustrated. I carefully reviewed my my last post, made a couple corrections then posted. The phone spell check do its own thing and built in words I never put in and messed up he context . I though I missed a couple words but it was correct when I hit the post button . It’s bad enough I have my own issues, I don’t need extra issues . I’ll search and see if there is some way to either disable this or get around it.
byron

I checked on micro soft and it did the same thing on the post to them . I left them with screw it , you figure it out , get back to me when you have an answers I can even read . I even Ickes out a new stylus washed screens even my hands and fingers . Even ordering on Amazon or directly from suppliers there is this issue . I’ve called Amazon I now just call suppliers directly if I can . I’ve even returned things I didn’t order or received incorrectly. Sometimes it even misspells my name at the end of posts

buron

 

[Bentwings]

I checked on micro soft and it did the same thing on the post to them . I left them with screw it , you figure it out , get back to me when you have an answers I can even read . I even Ickes out a new stylus washed screens even my hands and fingers . Even ordering on Amazon or directly from suppliers there is this issue . I’ve called Amazon I now just call suppliers directly if I can . I’ve even returned things I didn’t order or received incorrectly. Sometimes it even misspells my name at the end of posts

buron

I read every comment and I really appreciate them . I try to answer questions, explain my thoughts but this spell checker is frustrating
. I got good grades in English even Latin I even tested out of a full two years of engineering composition in college . This mess makes me look like someone from Tim buck two . See it can’t even post what I entered . Today I’m goingvto attempt to make some sketches or try and wade through dome cad I may be able to make it work. My late son changed some things that realy should have been left alone so please bear with me . I’ll tr and get back after I cool off. Open the blow down valve I guess it’s called by steamersLOL

 

[Bentwings]

I read every comment and I really appreciate them . I try to answer questions, explain my thoughts but this spell checker is frustrating
. I got good grades in English even Latin I even tested out of a full two years of engineering composition in college . This mess makes me look like someone from Tim buck two . See it can’t even post what I entered . Today I’m goingvto attempt to make some sketches or try and wade through dome cad I may be able to make it work. My late son changed some things that realy should have been left alone so please bear with me . I’ll tr and get back after I cool off. Open the blow down valve I guess it’s called by steamersLOL

I came about the same as far as heater required. I just ordered another 1200 watt heater soninyinkninmay be marginal but ok it will be a trill error I can get higher wattage if necessary that will fit in the same NOT fitting hole I’ve allowed . Most fittings will be 1/8” NPT with bushings or adaptors for what ever else is needed at this point I see only the fill Port used by the gear ump and the exit port on top to a manifold block for other distribution. There may be ports for the level gage which I don’t have yet and a rapid drain on the end. I ran into a condensor or economizer which I have given thought to. I’m not sure just waist is needs nor how much is needed for this small system I was hoping the little turbine might act like a centrifugal air cleaner I have thoughts to a filter of sorts but I don’t know how much exhaust will be generated . I’d like not to have oil air all over the place . So maybe some suggestions . There were turbo air cleaners in the textile industry that were very efficient . I don’t see anything as complex as industrial things. It will be interesting to see how hot th exhaust is.

on a side note the balsa wrap is nt going well the first 1/8” pice I started on last night is water logged but not forming around the tube well this is where the ammonia worked in the past but I won’t see the stuff for several days . I forgot the anode ports one on each end I found two more magnesium anodes from he boat today

this boiler has evolved into a quite complex thing . But electric heating I think made it more difficult . My son is cutting chips today

the engine have about 200 icees counting nuts as bold many as pretty small. I haven’t un packed all of it ye as I want to paint he frames before I start assembly it will be a gray barbecue type color I think . Textile equipment was the most horrible green ever created . I won’t be sad if I never see it again. LOL I HACE A SET UP BAD PLUS AN aluminum mount board . I’m thinking I at soft mount he engine frames both are linked by th man flywheel . I may have t switch to a flexible cpling but ubtill I have both assembles completed I won’t be there is an outer shaft support but I have a self aligning ball bearing for that as well as aluminum material I have one extra flywheel but it needs a little polishing to finish it up .
Now I have company coming next week so I’ll hac t go into idle mode

byron

 

[Bentwings]

Hi Byron, You sound to be very productive with your ideas. Just a couple I want to debate:

1. If you are planning on just balsa wood for insulation, that will be all you need for conductive losses, if around 1/2" or more. So I can't see any reason for the car exhaust stuff? But your choice. However, you should consider radiation losses (the radiant heat shines straight through the balsa or other until it hits the stainless steel). So if you polish the aluminium tube that will be excellent, or wrap in aluminium foil. Either will reduce radiant losses significantly compared to doing nothing with the surface of the tube.
2. My biggest issue is the use of aluminium with steam. I thought this was always a "NO! NO!" because water doesn't corrode aluminium rapidly, yet STEAM does, especially at elevated temperature. And when it does it gives off hydrogen, which has the potential of being very explosive... So although domestic pressure cookers with steam at up to 15psi exist and are safe to use, please check what higher temperature steam will do to your boiler.
3. A quick check suggests you need >5.2kW of steam to extract if the engine needs 50psi at1000rpm (and a generator to load the engine). Of course, at 20psi you'll only need 3kW... of steam power. Allowing for losses (maybe a couple of hundred W if well lagged?) you'll need more than those figures from the heaters. Unless I have screwed-up the calculations? (I had to correct some glitches in my spreadsheet). What did you calculate?
4. What "penetrations" will you make in the outer shell cylinder? (If any?) I can see a design where all the safety valves, water gauge connections, steam extraction, water-feed, etc. is done via the end plates, so the boiler shell is "without penetrations". but that is unusual. Mostly there is a steam dome (to collect steam high above the spraying surface of water), water feed, connection for safety valve, etc. so that affects the hoop stress calculations and comparison of the design with permissible safety limits. ASME uses a "Standard" value of 3.3 for the SCF if ANY penetrations exist in a boiler shell or tube. With this SCF (assuming at least 1 penetration) for your boiler at 50psi, I get a hoop stress of 1902psi and I think the permissible stress will only be 1141psi for aluminium..? which I reckon is a FOS of less than 5. But the regulations normally require a FOS of 8? But I may be wrong? If there are no penetrations in the shell tube, then the FOS is over 15 - which is good. - What have you calculated? - I am keen to be sure my calcs are sensible, and if you have close results I'll be happy.

Thanks,
K2

ok so the balsa will work . I have exactly 1/2” of material I’m working on wrapping . I’ll polish the basic tube then add balsa. I think the polished stainless exterior will make it relatively cool . I haven’t come up with an idea fore the end caps other than some fancy carving . I have som blocks of balsa and I think I could show my boys how to do some metal spinning. For outer covering . Ther will be some exits in th ends but I can mold th cutouts if necessary in balsa I actually was thinking of a singbopen insulated door . We do these hatches a lot on the Rc planes so it won’t be hard . It would give better access to fittings . Maybe clean up the ugly mess that a bunch of fittings can make . As far as calculations I have to admit I took the easy way and looked up various calculators on line. I don’t think I can get a factor of 8 that seems to be floating around. The extra tie rod between the end cap will go a long way toward keeping the end caps on I’m more concerned about the changes in temp causing loose screws around the periphery that hold the end caps. As I recall this would create a bending moment that could cause the screws to want to yer out . I simply have not experienced this. I don’t have the neat analysis program anymore that would clearly show this the couple of lithium military batteries explosions where the end cap failed actually tore the stainless steel or titanium shell apart . These were some really high pressure in the 10’s of k’psi . Hydraulic testing only showed potential cracking or leaks these were pyrotechnics gas generators so pressures got high very quickly then the electrolytes detonated . As we used to say the batteries were as powerfull as the odenance. Nice I get the steamer assembled I’ll have a better idea of pressure required I may be grossly under estimating but this little engine, actually a pair linked together just don’t have the crankshafts with enough stroke or bores to produce enormous torque the crankshafts just aren’t bug enough to handle big loads and I’d like to limit rpm to12-15,00 just so it lives a comfortable life . I may be all wet here . My usual thing is to squeeze every bit out but bad enough the turbine will be capable of 50k . I’m already concerned about lube for it.
As far as corrosion I was not aware that hot steam made it much worse I do have magnesium anodes from my boat marine corrosion in is always a headache but if anodes are replaced on time it’s easy to control I never had issues on the water . Working in the dairy with live steam cleaning I don’t remember any issues stainless steels seemed to be clean and shiny all the time Steel milk crates rotted out easily . I suppose it could be said “he will learn the hard way “ I see lots of learning coming . I do appreciate comments I dug up some old school drafting stuff so I’m going to try and improve my sketches. I just got my new building board so I can have a mini drawing table for a while
Byron

 

[Bentwings]

ok so the balsa will work . I have exactly 1/2” of material I’m working on wrapping . I’ll polish the basic tube then add balsa. I think the polished stainless exterior will make it relatively cool . I haven’t come up with an idea fore the end caps other than some fancy carving . I have som blocks of balsa and I think I could show my boys how to do some metal spinning. For outer covering . Ther will be some exits in th ends but I can mold th cutouts if necessary in balsa I actually was thinking of a singbopen insulated door . We do these hatches a lot on the Rc planes so it won’t be hard . It would give better access to fittings . Maybe clean up the ugly mess that a bunch of fittings can make . As far as calculations I have to admit I took the easy way and looked up various calculators on line. I don’t think I can get a factor of 8 that seems to be floating around. The extra tie rod between the end cap will go a long way toward keeping the end caps on I’m more concerned about the changes in temp causing loose screws around the periphery that hold the end caps. As I recall this would create a bending moment that could cause the screws to want to yer out . I simply have not experienced this. I don’t have the neat analysis program anymore that would clearly show this the couple of lithium military batteries explosions where the end cap failed actually tore the stainless steel or titanium shell apart . These were some really high pressure in the 10’s of k’psi . Hydraulic testing only showed potential cracking or leaks these were pyrotechnics gas generators so pressures got high very quickly then the electrolytes detonated . As we used to say the batteries were as powerfull as the odenance. Nice I get the steamer assembled I’ll have a better idea of pressure required I may be grossly under estimating but this little engine, actually a pair linked together just don’t have the crankshafts with enough stroke or bores to produce enormous torque the crankshafts just aren’t bug enough to handle big loads and I’d like to limit rpm to12-15,00 just so it lives a comfortable life . I may be all wet here . My usual thing is to squeeze every bit out but bad enough the turbine will be capable of 50k . I’m already concerned about lube for it.
As far as corrosion I was not aware that hot steam made it much worse I do have magnesium anodes from my boat marine corrosion in is always a headache but if anodes are replaced on time it’s easy to control I never had issues on the water . Working in the dairy with live steam cleaning I don’t remember any issues stainless steels seemed to be clean and shiny all the time Steel milk crates rotted out easily . I suppose it could be said “he will learn the hard way “ I see lots of learning coming . I do appreciate comments I dug up some old school drafting stuff so I’m going to try and improve my sketches. I just got my new building board so I can have a mini drawing table for a while
Byron

I had seen an old horizontal boiler at a textile factory . It wasn’t operational but it kinda influenced me also trying steamers are horizontal, at lest I not seen a verticals . Plenty tall stacks
So that’s wehrrewhat the idea came from there was also a icture of the mill steamer fromthe late 1800’s so that’s why I chose this one . Nostalgia I guess since I made a massive motor driven rolling mill with some electric motors probably off and old battle ship. They had US NAVY stensiled on them 40+ hp they had som big copper power cables . So one of my driven things is a “dyna mo “ that actually looks a lot like these giants I don’t have any lans to duplicate or even simulate any textile stuff other than a piece of history it was a dark age for me . Sad
As many fittings as possible will be in the end caps one end will have the level gage and fill port, the opposite end will have the fast blow downs port for steam out to a distribution manifold I’ll have to give into a port for pressure relief on the high end maybe teed to the fast blow down. I don’t know yet ., ossibly the pressure gage gotta have a whistle some place too . I’m thinking the manifold will cover a lot of ground providing ports for anything needed I’m not sure where the steam feed goes yet. I haven’t unpacked all the parts yet the engine mounting hole are very small about 3 mm to my un metricized eye I tried to get the big computer up but it takes a double monitor so I’ll have to un pack that then try again . This was my Ltd big gaming center so it’s loaded with games and big monitors I didn’t get to see how it was it together so I’m fumbling around even the laptop has big processor and external monitor hookup so I’m still stuck with iPhone and iPad I’ve got to wat for he pantdcasting before I can really get started on the engines

byron