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Brooks
Conductor
1st Class Member
USA
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 Posted - 13 Oct 2005 : 16:06:21
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The Spiral of Silence - for Maxwell Smart, R.I.P.
What - A spiral of steel wool is installed in the flue to muffle the sound of the burner.
Why - I like the power of the Dave Hottmann sleeve burner and the relative silence of the Kevin O'Conner radiant burner. This muffler device allows me to achieve near-noiseless operation of a powerful burner, e.g. the DH, or the CSS (see thread "Burner efficiency, some test results"). Like Maxwell's Cone of Silence, the SoS does not completely muffle sound, though it greatly reduces the flame roar. In fact, the hiss of the gas jet is now as loud as the burner on my Shay, and I can hear the water boiling. The first time I heard the water, I thought I had a leak somewhere. Steel wool makes a great muffler, but if you just plug the end of your flue, you will kill the fire. The spiral design allows burned gasses to escape to the smokebox, while still intercepting most of the sound waves.
Requires - Malleable wire, e.g. stainless steel .032" diameter.
Steel wool, e.g. #2 or #4 size. Any wool would work, the finer sizes just burn out faster. Stainless steel wool would probably be best (expensive).
How - Make a spiral with the wire about 1/2 the diameter of your flue (think, "make a large spring"). For the Shay's 6/8" diameter flue, a 3/8" dowel worked well as a mandrel. Take 3 turns around the mandrel, spaced about 1-2 cm apart, and make little hooks in the ends of the spiral. The hooks will be used to hold the steel wool. My spiral is about 6 cm long. Now, unroll your pad of steel wool, and cut a strip of wool about 3x's the length of the spiral and about an inch wide. Attach the end of the wool to one of the hooks (squeeze shut to secure the wire), and wrap the rest of the wool around the spiral. You are attempting to make the wire "thicker" with the wool, so wrap accordingly. As you wrap, the natural twist imparted to the wool will help control the stray fibers. When you get to the ending hook, attach the wool, and cut off the excess. Test fit the SoS in your flue: the device should be about the diameter of the flue. You can adjust the fit by scrunching up the spiral or stretching it out, as needed. The tighter the fit, the better the sound reduction, but the harder it will be to light the fire. Mine has about a 2mm gap between the wool and the top flue wall.
Lighting the fire - The fire may be easy to light or hard, depending on the temperature of the boiler (cold easier than hot). You want the fire to "pop" back to the burner, not just burn at the smokebox end of the SoS. I use the "puff" method (see thread "A Radiant Afterburner"); start with more gas flow than normal, so you don't blow out the fire when you puff. I wear goggles while lighting this contraption, both to protect my eyes from the flame, and also to protect them from bits of steel wool that might be shot out the smokebox. If you experience more lighting difficulty than you want to put up with, then stretch out the spiral, leaving a 5 mm space between the steel wool and the top flue wall. Lighting takes practice.
Problems - 1) Lighting the fire.
2) Eye Danger from steel wool bits; also wear on equipment if the bits get in the valve gear/bearings/etc. I clean my loco thoroughly with hot soapy water after each outing.
3) Longevity of the device; The steel wool burns some and disintegrates over time. Stainless steel wool would probably last longer, but it's only available from McMaster-Carr in 5# rolls. You might be able to find some in the cleaning dept. of your local hardware store; my local store used to stock stainless steel scrubbing pads. Or, perhaps a restaurant supply store or car parts store might have them.
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Edited by - Brooks on 17 Oct 2005 16:47:32
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Brooks
Conductor
1st Class Member
USA
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Posted - 13 Oct 2005 : 16:11:31
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I'll put up a photo, if some 1stClass member volunteers to host it.
Thanks,
Brooks |
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seadawg
Foreman
1st Class Member
USA
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Posted - 14 Oct 2005 : 06:47:13
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quote:
Originally posted by Brooks
The Spiral of Silence - for Maxwell Smart, R.I.P.
Snip....
Test fit the SoS in your flue:
snip....
When I was in the Navy we called somthing else SoS.
A certain type of "breakfast(?)" food(?).
All kidding aside Brooks, keep up the good work. |
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Dougald
Railway Exec (Moderator)
1st Class Member
Canada
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Posted - 14 Oct 2005 : 07:35:58
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Brooks
If you have no takers I would host the pic for you.
Contact me via email ... Doug |
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Brooks
Conductor
1st Class Member
USA
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Posted - 18 Oct 2005 : 00:29:47
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The finer grades of steel wool do a better job of muffling sound. All grades tested (#000, #2, #4) burn, leaving a worm of wool wound around the spiral armature. The worm is sort of like the mantle of a Coleman lantern - intact, but fragile. It seems to be strong enough to withstand steaming, but if you pull it out of the flue for some reason, it will crumble. The armature remains intact, so you only need wind some new steel wool, and you are in business again.
For some tests, the fire burned within the wool (rather than at the poker [desireable], or in the smokebox [undesireable]). The within mode is the form of combustion used by the German team which is developing a burner for a proposed steam automobile. They use porous ceramics or exotic metal meshes to form the burner matrix, not simple steel wool.
My tests did not achieve sustained burning within the steel wool matrix, however. My within mode burning only lasts for 10 seconds or so. I will try to figure out favorable conditions for within mode combustion. The fire in this condition is absolutely silent (except for the hiss at the nozzle), and probably generates almost pure radiant heat, at moderately high gas flow rates. If one were able to achieve the German results, a Shay would need a burner only 1 cm^2 in size. The worm has about 6 cm^2, not accounting for it's fibrous nature. It would appear that this mode has the potential to supply power, efficiency, and low noise. |
Edited by - Brooks on 18 Oct 2005 07:24:36 |
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