Stainless Steel "brick Arch"

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Keith1500
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Stainless Steel "brick Arch"

Post by Keith1500 » Wed Mar 12, 2008 8:52 am

I was inspired recently by chat I had with Alan Wood while running my model of Rocket.

Rocket as you can imagine has an extremely small boiler and the grate is the size of a match box. The model drafts very well and has a tendency to pull the fire through the lower tubes which then mean they become blocked.

I liked Alan’s idea of fitting a Stainless steel deflector that would act like a brick arch. Any thought on what type of stainless would work in this harsh hot environment?

Keith
dave26
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Post by dave26 » Fri Mar 14, 2008 8:23 pm

I made the very same thing for my Juliet, i used 316 stainless plate and was welded via 2 legs to the stainless grate and was arched infront of the tubes, it worked ok with modifications, but in the end it didn't steam as well as it did so removed it. :roll: :roll:
Eddyg
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Stainless steel arch

Post by Eddyg » Sun Mar 16, 2008 11:46 pm

Keith,

I run two locos with arches. The 3 1/2" GN Atlantic was prone to blocking its tubes and fire throwing and both were relieved by fitting the arch. I first used 3/8 x 1/8 grade 316 in strips bent in the 3/8 plane and rivetted together to form a 3/8 thick arch in two sections about 1 inch wide. The supports are stainless angle bent from 16 gauge sheet and fixed to the firebox by putting screw threads on a couple of the stay ends which were long enough to do the duty. This lasted along with the arch for about 15 years. I recently changed the arch to 1/4 plate and the rear edge is showing quite rapid burning after just one season. Whilst there is no improvement to the steaming it does run a lot longer before it gets choked up with the arch in place. I did try making an arch out of fireclay, but it was too light and tended to get lifted off by the draft.

The other loco is a 5" gauge with a narrow box, but it doesn't seem to make much difference whether the arch (316 also as the atlantic's original) is present or not, and I tend to run with just half the arch in place normally to reduce the amount of ash in the tubes. I actually built bushes into the firebox sides for the arch supports on this one and that has been very successful.

One of our members has a 7 1/4 Holmeside with an arch supported off the grate as Dave suggests and I think it's made from 1/2" mild steel which gets replaces every two or three seasons as it burns away. stainless just burns more slowly.

Eddie
Keith1500
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Post by Keith1500 » Mon Mar 17, 2008 10:07 am

Your account of the arch in the 3 1/2" GN Atlantic is amazing. I would like to see a photo’s of the arch if possible. I had never thought about the thickness of the arch – on your Atlantic, this it was 3/8 thick if I have understood correctly.

I just was just thinking of using a piece of 2mm thick curved and angle to protect the lower tubes. Rocket performs exactly as you describe your
3 1/2" GN Atlantic – its prone to blocking lower tubes and throws out fire!. I will probably support the arch from the grate as per Dave’s suggestion. (Thanks Dave for your contribution).

It’s the thickness of the arch that intriguing me now. Rocket’s grate is literally the size of a match box – Bryant and May that is not Swan Vesta! So the thickness of the arch will be limited. The angle I guess will be determined by the bottom of the lowest tubes and the top of the fire door? I would guess the arch would reduce the space the flames pass through to about half of length or depth of the fire box?

So a few more questions… Thank you for taking time to reply.
Eddyg
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Stainless Arches

Post by Eddyg » Tue Mar 18, 2008 11:14 pm

Keith,

The arch does get very hot. I suspect your Rocket's fire will be just as hot as any other loco - anything up to white hot 1400 centigrade, so your 2mm arch if it doesn't melt, will certainly burn away very quickly. The first arch I tried was 3mm thick but it didn't last long, hence the thicker model. I was also trying to see if there was any reserve of heat in the arch as happens in full size, but I couldn't say whether I was seeing that effect in the model. I started with arches that were 75% of the length of the firebox sloping from the bottom of the tubes to the top of the door. The problem is that with the arch in sections so they can be fitted through the door ( the ash pan doesn't drop on my loco) the back section tended to get dislodged by the shovel, so I run with two sections in place now, say 50% of the grate area. If a section gets left on the grate after falling down it comes out in a sorry state, burnt and partly fused. On the 5" engine, I ran a 40 minute train at Gilling with an arch section on the grate. It steamed very well if not better than normal, but the arch was scrap.

I'd send you a picture if I could get my head around attaching files.

Eddie
Keith1500
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Post by Keith1500 » Wed Mar 19, 2008 7:11 pm

Eddie

Yes Rockets fire burns extremely hot - I have never seen anything quite so incandescent before! I dont think the stainless will survive judging by what you have said.

However, I will give it a go. It will be simple enough to fit and replace and worth a try. I am toying with the idea of running Rocket one evening at Gilling this May. Just to see if i can get around the track a few time if not at least once with out stopping !

Thank you very much for the information and if a photo or two is possible - great

Keith
davet
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Post by davet » Sat Mar 29, 2008 2:03 am

Nicrome as used in jet engine combustion chambers is a good choice, if you can get it. I have used this in my Ajax and it does not burn out. A 316 stainless should work and give a reasonable life but even a mild or low carbon steel will work for a time but will suffer from burn out .

Dave T.
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