Building the 2.5" Scale Shay

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Pontiacguy1
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Location: Tennessee, USA

Re: Building the 2.5" Scale Shay

Post by Pontiacguy1 » Fri Oct 25, 2019 7:41 am

Started a few grass fires in Texas with my 0-4-2 Chloe. That thing had a fully enclosed ash pan, but would really draft and would throw hot embers out the stack fairly regularly. They would sometimes land a couple of feet to the side of the tracks, and that's what started the fires. It also didn't help that I would run the thing like it was a bank heist getaway car. There were no trees around where the most of the fires got started, just really dry grass.

Point being: If starting fires is an issue, you really need to address both the ash pan and spark arrest, especially if you tend to work your locomotive hard and have a lot of stuff going up the stack.

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Fender
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Re: Building the 2.5" Scale Shay

Post by Fender » Fri Oct 25, 2019 8:04 am

“ Still plenty of other parts to fabricate too, plus could use some recommendations on the size screen to use in the upper portion as the final filter to catch any sparks.”

I used some 6x6 mesh ss screen from McMaster-Carr, which seemed pretty effective. But the R&H stack is supposed to separate the embers from the smoke by centrifugal force, rather than by “straining” them from the exhaust. And, the physics might not scale down well for a live steam version of this stack.
Dan Watson

Soot n' Cinders
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Re: Building the 2.5" Scale Shay

Post by Soot n' Cinders » Fri Oct 25, 2019 11:17 am

I definitely have a tight ash pan, I’ve yet to see anything get out of it. The shay has such powerful exhaust it really throws debris out the stack. I’ve not had anything overly large escape but there have been pieces large enough to burn holes in my shirt, so it’s a fire risk if it got dry enough. And I think because of that powerful draft, the physics behind the stack might just work. Only one way to find out! To my knowledge, the only other working Radley & Hunter stack in scale is the one on the shay built by George Corwin, but I’ve never seen it myself and I’ve not heard how well that stack works.
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

rkcarguy
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Re: Building the 2.5" Scale Shay

Post by rkcarguy » Fri Oct 25, 2019 12:27 pm

From my fabricator experience, it's important to calculate your open area of your mesh or whatever you plan to use to for your arrestor. I would think if you maintain more area through the mesh than your stack flows and don't kink the flow direction out of your stack too much, upsetting the draft shouldn't be an issue.

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NP317
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Re: Building the 2.5" Scale Shay

Post by NP317 » Fri Oct 25, 2019 11:20 pm

I look forward to hearing how the new stack works.
RN

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Fender
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Re: Building the 2.5" Scale Shay

Post by Fender » Sat Oct 26, 2019 4:18 pm

My understanding of how these “centrifugal separator” stacks (including the Rushton and Radley & Hunter) are supposed to work, is that the larger embers are forced to tumble around inside at the periphery of the stack, until they disintegrate into smaller pieces. Then, their smaller mass allows them to escape along with the other combustion products (i.e., smoke).
Dan Watson

Claralinja
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Re: Building the 2.5" Scale Shay

Post by Claralinja » Sat Oct 26, 2019 4:51 pm

From a fluid mechanics point of view,the load carrying capacity of the exhaust stream is dependant on the velocity of the flow. By widening the diameter of the stack the velocity would theoretically be reduced and along with it the amount of embers being carried.

The question then is whether or not the exhaust stream has time to adjust to the larger diameter before exiting the stack. The baffles etc are there to encourage this adjustment.

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Fender
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Re: Building the 2.5" Scale Shay

Post by Fender » Sat Oct 26, 2019 10:49 pm

That’s a good point about the reduced velocity. Some of the embers end up dropping down into the “funnel” around the outside, on the bottom of the stack.
Dan Watson

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NP317
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Re: Building the 2.5" Scale Shay

Post by NP317 » Sun Oct 27, 2019 9:51 am

Fender wrote:
Sat Oct 26, 2019 10:49 pm
That’s a good point about the reduced velocity. Some of the embers end up dropping down into the “funnel” around the outside, on the bottom of the stack.
That is one of the functional characteristics of the R&H stack.
On our Climax locomotive the exhaust smoke exited with a swirling motion, looking real lazy for a steam locomotive.
And there are traps at the bottom sides of the stack with doors that open to remove accumulated cinders.
As an oil burner we never found much crud in those traps.

And the draft was very poor. I know, I already said that...
RussN

Soot n' Cinders
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Re: Building the 2.5" Scale Shay

Post by Soot n' Cinders » Sun Nov 10, 2019 2:01 pm

So stack work has been under way. Most of the rough forming is done with only one more sheet to flange for the joint to the cones. Glad I went with 22ga material, forming the cones and cylinders was easy but forming the angled flanges was a little trickier. Most of it was done with a piece of 3/8” round round with a slit cut in it, final tweaks being done with a hammer and some larger round stock. Riveting should begin this week, and just waiting on the piece of steel to use for the base welded to the existing stack pipe.
The mesh for the top is going to take some experimenting. I think the 6x6 is going to be too large. Rough guess is I need something with an opening around 0.08” but I’ll look at some of the cinders left on the decking and cars I’ve been pulling to size them up.
Attachments
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-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

Soot n' Cinders
Posts: 813
Joined: Wed Jun 27, 2012 5:24 pm
Location: Marietta, Georgia

Re: Building the 2.5" Scale Shay

Post by Soot n' Cinders » Sun Nov 17, 2019 11:13 pm

Well in the hurry to get the stack operational, I havent posted much. So now its time to update this will lots of pictures and a video at the end!
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Here we have the first two sections of the stack ready for drilling to be riveted together. To help hold things together nice and tight, I ran a piece of 3/8" all thread through my workbench to make a clamp. With things clamped down, the alignment was dialed in with a hammer before drilling and then riveting 3 holes. The remainder of the hole were drilled and riveted splitting the gap each time until all of the rivets were in.
This view also shows how the caps for the chutes attach, a simple twist lock mechanism
IMG_0159(1).jpg
Here the stack has been attached to the main pipe with supports coming off of the top. On those supports is the base of the cinder breaker cage with the diverter cone resting in place to check its position.
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In these two, the upper cylinder for the stack has been riveted on with the bolt ring soldered in place. The solder failed during the first run and was replaced with silver braze, more on that later.
IMG_0162.jpg
Finally, here is the cinder breaker in place in the stack awaiting the diverter cone and top cover.
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

Soot n' Cinders
Posts: 813
Joined: Wed Jun 27, 2012 5:24 pm
Location: Marietta, Georgia

Re: Building the 2.5" Scale Shay

Post by Soot n' Cinders » Sun Nov 17, 2019 11:19 pm

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Here we have the top plate freshly riveted and soldered together, sitting in place to check for fit. This solder also failed.
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With the stack nearing completion, I had to try it on for size.
IMG_0168(1).jpg
Next, the beading for the top was completed with the mesh held in place. I used copper pipe left over from piping for the beading and cut a slit in it with a dremel tool to hold the mesh. Once the mesh was inserted in the gap, the pipe was crimped down on it. The mesh is slightly oversized so it holds itself and the beading in place with no solder or adhesive. This allows me to service the diverter cone without having to take off the top plate. The mesh is 12x12 stainless steel fine particle mesh from McMaster-Carr.
IMG_0169.jpg
Here we have the completed cap in place on the cinder dump of the stack.
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And here is the finished stack, ready for testing!
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

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