# How does a bear trap spark arrestor works



## Gerd (Jan 7, 2008)

Hello all, 

for my 2"-scaled forney, I'm searching for a working spark arrestor for the stack. 

I've found some pictures of the bear trap type, used on some C&S and RGS locomotives and I wounder how they work. Can anyone help me with this? 

Thank you very much. 

Regards, Gerd


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## kfrankl3 (Feb 27, 2008)

_very nice_ forney btw. But you may want to move this thread to the "live steam" forum.


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## Torby (Jan 2, 2008)

How do they work? 

Nicely


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## kfrankl3 (Feb 27, 2008)

Actually if I remember from the textbooks correctly, A beartrap is like any other spark arrestor. The reason for the pipe is so that any ashes and such that would otherwise clog up the spark arrestor is sent down into the roadbed ballast. This thereby avoids the once all to common brush fires caused by the "iron horse". If you are looking for good material on the development of the spark arrestor in general I would recommend reading ' 




John H. White, Jr. American Locomotive: An Engineering History 1830-1880: Revised and Expanded Edition. Baltimore and London: The Johns Hopkins University Press, 1997. 


ISBN" 0-8018-5714-7


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## Mik (Jan 2, 2008)

Basically the big hot chunks that can get pulled through the tubes when the engine is working hard get caught by the angled screen. They then fall into the trap and are dropped along the track through the ash tube. 

Spark arrestors (like those inside balloon stacks, or cyclone smoke boxes) use screens and/or changes in exhaust gas pressure, velocity or direction to convince the larger, heavier particles to drop out of the flow. The hot gases are allowed to pass -- and some of the small sparks, which tend to burn out quickly, but the larger chunks which stay hot long enough to kindle a lineside fire are trapped.


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## Gerd (Jan 7, 2008)

Thanks for the discreption. So it sound's that there's nothing more inside the stack himself. 

Well, I'll try to model one for my steamer and will test him on one of the next running days. 

Regards, Gerd


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## East Broad Top (Dec 29, 2007)

Okay, but why was it called a "bear trap" spark arrestor? I can't say I'm intimately familiar with methods of ensnaring the ursus species, but I can't think of anything that looks like its namesake device on a steam locomotive. 

Later, 

K


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## Robbie Hanson (Jan 4, 2008)

I've got a Narrow Gauge and Short Line Gazette somewhere with some info, and a few articles online reside in my memory--I'll look them up and link to them when I can. 
If I recall, calling it a "bear trap" is nearly offensive to original Colorado & Southern employees--it was referred to as a Ridgway, after H.A. Ridgway, the C&S Mechanical Superintendent who invented them. The term "bear trap" was coined by model railroaders in the 1960s and 1970s. 

EDIT: Found something. 
NG Discussion Forum: http://ngdiscussion.net/phorum/read.php?1,107357,107698#msg-107698


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## Charles M (Jan 2, 2008)

The first use of the term " Beartrap " has to be credited to Lucius Beebe in his book "Narrow Gauge in the Rockies " published in 1958. On page 143 he describes the cinder catcher on No. 71 as being called a " Beartrap throughout Colorado" . How he got this name has been debated before , without an answer. It may only be a good story for his book. 

The following information may help Gerd with making a Ridgway Cinder Catcher for his Forney. This is the original patent for the Cinder Catcher. 

http://www.google.com/patents?id=0rk_AAAAEBAJ&dq=Ridgway+Spark+Arrester&jtp=1#PPP1,M1 

It is pretty interesting , check it out. It is available to download as a PDF for those who would like it for their files. 

Charles M SA#74


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## kfrankl3 (Feb 27, 2008)

I've turned the html into clickable links: 

NG Discussion Forum 
Patent application by Harry W, Google Patents 




Thanks for posting the Patent Charles, I was planning on making a beartrap for my ruby, so i have been watching this thread closely, and that is exactly what I need!


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