Supporting > Boilers
A SCOTCH MARINE BOILER FOR MY TRIPLE EXPANSION ENGINE
crueby:
Ooooohhhhh, okay! I had not looked close enough at the plan cross section in the very first post, sorry! Never seen that arrangement before, so I assumed it was the usual burner-at-one-end-chimney-at-the-other style. So, as you say, not part of the pressure vessel, though it will take a direct hit from the burner flame coming through the lower pipe.
:cheers:
Jasonb:
regarding expansion, if we said the metals could get upto 500deg C which they are unlikely to then the difference in expansion across the diameter will be 0.21mm or 8thou. ( 0.83mm - 0.62mm ) so provided the "snug fit was eased a bit to sat 5thou all round then the aluminium won't apply any force to the boiler shell
copper boilers used to be caulked withsoft solder and that never melted out at 200deg C or less and is why 648 is OK and aluminium unlikely to melt.
Vixen:
--- Quote from: Jasonb on February 22, 2024, 07:32:06 pm ---Yes I took it a sAluminium at both ends, and agree that too snug a fit may cause problems with expansion and depending on the amount of use galvanic attack could be an issue.
But regarding heat the plates are a bit like the 648 will they see direct heat ?and if so what flame temperature and more importantly material temp, a typical air/propane torch may only give 750degC temp in the components and that is with the flame directly applied
--- End quote ---
You need to be careful how you interpret that graph. That graph shows the flame temperature of propane/ air to be 1950*C and that has only recently been demonstrated to be hot enough to melt pure copper down tubes. It appears that the flame tube (if that is what it's called) is 2.25" diameter, so will do little to cool the flame. Therefore, I would be very concerned at the flame playing directly on the return end plate. The return path through the smaller boiler tubes will remove most of the heat and so reduce the flue gas temperature, so I am less concerned about the smoke box end.
Why make-do with what's in the scrap box? Why not work to MIL TBD41 standards?
For those who are not familiar with that standard, it stands for "Make It Like The Bl**dy Drawing For Once"
Jasonb:
I can melt steel with my propane torch, just depends on how thin it is and the output of the burner and where you hold it in the flame.
Do we actually know what John is going to fire it with, Harris suggests the Stuart paraffin blowlamp, Flame temp of paraffin 1100degC
There are other variations from the drawing so would really need to start from scratch if sticking to them.
simplyloco:
--- Quote from: Vixen on February 22, 2024, 08:03:59 pm ---
--- Quote from: Jasonb on February 22, 2024, 07:32:06 pm ---Yes I took it a sAluminium at both ends, and agree that too snug a fit may cause problems with expansion and depending on the amount of use galvanic attack could be an issue.
But regarding heat the plates are a bit like the 648 will they see direct heat ?and if so what flame temperature and more importantly material temp, a typical air/propane torch may only give 750degC temp in the components and that is with the flame directly applied
--- End quote ---
You need to be careful how you interpret that graph. That graph shows the flame temperature of propane/ air to be 1950*C and that has only recently been demonstrated to be hot enough to melt pure copper down tubes. It appears that the flame tube (if that is what it's called) is 2.25" diameter, so will do little to cool the flame. Therefore, I would be very concerned at the flame playing directly on the return end plate. The return path through the smaller boiler tubes will remove most of the heat and so reduce the flue gas temperature, so I am less concerned about the smoke box end.
Why make-do with what's in the scrap box? Why not work to MIL TBD41 standards?
For those who are not familiar with that standard, it stands for "Make It Like The Bl**dy Drawing For Once"
--- End quote ---
Hi Mike.
If there was a drawing available I would have probably attempted to make it to that.
However, in it's absence I did my own thing, as most competent model engineers would do. I will leave it as it is and see what happens in practice.
John
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version