Spark arrester design

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pat1027
Posts: 444
Joined: Sat Oct 09, 2004 3:45 pm
Location: Michigan

Re: Spark arrester design

Post by pat1027 »

My first thought was a bear trap spark arrester like the Denver and Rio Grande used to use on their narrow gauge locomotives. Looking at pictures of the same locomotives in modern times they are using a simple screen with a couple differences. The screen is larger diameter than the stack giving an annular area for large particulate to drop out rather than plug the screen. I will make the assumption a solid top cause the particulate to make a change in direction and loose velocity. It'll drop everything all over the boiler and running boards but you could merge this screens simplicity with the bear traps duct to the ground. Good thread. I want to run in August at a club that requires a spark arrester during dry conditions. This might be it.

Image
Steve Goodbody
Posts: 219
Joined: Thu May 25, 2006 7:16 am

Re: Spark arrester design

Post by Steve Goodbody »

Hello Glenn,
If you are looking for a top-of-stack spark arrestor then you may want to consider the following design rather than a mesh:
Spark Arrestor.JPG
Although more difficult to retrofit, an in-smokebox design is obviously less obtrusive. Stainless steel mesh is readily available, for example McMaster-Carr carries "Stainless Steel Wire Cloth" which is what I have used for my spark arrestor - pictures of the arrestor are included in the "A Long Term Project" thread.

Best regards
Steve
Glenn Brooks
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Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Re: Spark arrester design

Post by Glenn Brooks »

Steve and Pat,

Thanks much for your design ideas and photos. Both are very interesting. I bought some bronze mesh to experiment with, mostly as it was readily available with no waiting time to acquire. Will be firing up the Loco over the next day or two to experiment and see what happens. Will post some photos and comments about functionality after I see what happens.

BTW, Steve, you Hunslet is brilliant. And I particularly like your in stack spark arrester showing in your long term project thread. It seems to offer a spark barrier with no restriction on stack exhaust/ fire box vacuum. Have you had an opportunity to test it out yet?

Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
Marty_Knox
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Location: Michigan, USA

Re: Spark arrester design

Post by Marty_Knox »

Glenn, I just checked. My spark arrestor is made from 316 SS woven wire cloth. It is 6 x 6 mesh with .037" wire. The tie-downs are made from 1/16" 316 ss TIG wire, and the band is made from .032" x 3/8" strapping.
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RCW
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Location: Valle de Oro, TX [near Amarillo]

Re: Spark arrester design

Post by RCW »

Anyone tried a Congdon stack or a "bear trap"?
--Bob
Steve Goodbody
Posts: 219
Joined: Thu May 25, 2006 7:16 am

Re: Spark arrester design

Post by Steve Goodbody »

Hi Glenn,
I haven’t yet steamed the Hunslet, but the in-smokebox spark arrestor arrangement is nothing new and I make no claim to its originality. Hopefully all will be well so wish me luck!

The mesh is 316 stainless with about 1/8” holes, this was based on generally consistent conclusions from several ME magazine articles over the past 30 years or so.

The on-stack spark arrestor is on my 3” traction engine and works well. I find it more appealing to look at than the mesh-based arrangements but usually don’t use it unless things are tinder dry.

Best regards
Steve
Glenn Brooks
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Location: Woodinville, Washington

Re: Spark arrester design

Post by Glenn Brooks »

Here’s my attempt at a spark arrester.
900F8B34-D81D-44C2-BAB8-9C34245EF3D9.jpeg
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B3742C40-8DAD-4433-9C25-775858B75B09.jpeg
809FB672-0089-4A94-A21C-1A5B239A944B.jpeg
Decided to go with an expanded cone mounted atop the stack, to accommodate the expanding rush of gasses and ash leaving the stack. I am sensitive to the idea of not unduly restricting the exhaust stream, hence the cone idea.

This is a quick and dirty weldment with three rings and three vertical bars, welded at 120* around the base. I plan to add wire mesh around the outside and make some kind of wire mesh lid for the top. Probably held down with hangers similar to Marty’s design. I’ll use a hose clamp around the stack to hold the wire mesh and frame in place.

There’s an outside chance, that Maybe, maybe I’ll get fancy and make the lid in the shape of the top half of the cone. Or, it would be really nice to fit concentric rings , such as shown by Steve B. But right now, that seems like a lot of work for an untested design.

Edit: The more I think about it, the lid probably needs to include some sort of catchment or lip to hold burning embers. al la “Bear-trap” style mentioned by pat1047.


Mainly at this point, I want to see if the basic structure actually is functional. Then make improvements afterwards.

Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
reubenT
Posts: 107
Joined: Wed Dec 24, 2008 11:04 pm
Location: Spencer TN USA

Re: Spark arrester design

Post by reubenT »

Been thinking about the same thing. Need one for the ofeldt boiler on the 4x4 truck so I'm not starting fires in the woods this fall when I start running it for firewood gathering, wood fired boiler with blower draft. I have a sheet of what looks like air filter screen metal 0.09" thick with 1/8" holes. Figured I would try that arranged like on the 484 loco. Hope it doesn't clog too fast with ash. But it can just set on and be easy to lift off and clean out.
Glenn Brooks
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Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Re: Spark arrester design

Post by Glenn Brooks »

Finished the spark arrester and installed it on the Loco last weekend. Turns out, the oversized top catchment thingy looks hideous. Sort of like the “Major Award” woman’s leg and lampshade the Old Man won in the “Christmas Story” movie. I mentioned that to the lady across the street who came over to have a look. She offered to bring over some lace from her sewing room to hang around the bottom edge! Hahaha.

but, I fired the Loco twice this week, and it seems to perform its job. So function over Form, so far. And I haven’t burned down the neighborhood, which is a good thing.

Also, it seems to be large enuf, so that it is not getting clogged with ash and soot. And I seem to be getting plenty of air flow and draft. I’ll try to post a couple of pictures on Sunday, with the fire lit in the boiler, and exhaust up the stack.

Here’s how it came out of the shop.
148F7F4D-D182-4981-99ED-67B6A54657D4.jpeg
6259DA14-929E-434A-9BA1-B20FB10418D5.jpeg
F793AE85-04CA-40B9-A52F-80913E78E4BD.jpeg
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
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NP317
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Joined: Tue Jun 24, 2014 2:57 pm
Location: Northern Oregon, USA

Re: Spark arrester design

Post by NP317 »

Yea. Some lace would look good around the bottom...

Pretty funny, actually. But Function over form is the rule of our current weather.
Good that there's no such thing as global warming.
~RN
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