Larger scale Stuff

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Re: Larger scale Stuff

Post by FWLR » Thu May 02, 2019 9:14 am

You make a good point about the gas cylinders, but steel corrodes a lot more quickly and faster because of the presence oxygen in the water that combines to make Iron oxide, which is formed when iron and oxygen react with the water. So the use of copper is used because it won't rust like steel, granted it does turn green and corrode, but over a very longer period of time.
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Re: Larger scale Stuff

Post by GTB » Thu May 02, 2019 11:33 am

TonyW wrote:
Wed May 01, 2019 8:20 pm
Hmmm.... a 16mm/foot loco with a steel boiler could be interesting. I wonder, does steel corrode faster or slower than brass...?
Depends on the grade of brass. Mild steel corrodes faster in water than most brasses. If arsenical brass is used to make the boiler, which I believe was the case with the old German toy locos, the boiler isn't particularly prone to dezincification. The low zinc red brasses aren't a problem either.


The main issue with using steel in very small boilers is that the money saved on materials will likely be swallowed up by having to employ a welder with the necessary qualifications. Unless you know the right person and he does it at mate's rates.....

When you move up to the large miniature locos mild steel is the name of the game, although Aust. now allows the use of Duplex steel as well, which is related to stainless steels. It has low corrosion rates and high strength, so thinner plates can be used, but it has to be welded by specialised welders with the right paperwork.


Mild steel boilers need to be manufactured with thicker plates to allow for wastage over time from corrosion. Corrosion rates can be reduced with a good water treatment regime, but not completely eliminated. A large scale model boiler I'm familiar with is now 35 years old and when tested ultrasonically 5 years ago, had lost 3mm of thickness in some areas, even with water treatment.

Mild steel is technically feasible for boilers in the garden scales, but it will be a brave manufacturer that makes the first move. A reasonable lifetime and liability issues are the biggest obstacles, as there's no way that a manufacturer can ensure owners will bother maintaining the water treatment. Duplex steel may be a better bet for sub-miniature boilers if copper becomes unsustainable for hobby boilers.


Anyway......

It costs me about A$50 for the materials for a copper boiler and a couple of days work, compared to something like A$500 for a commercial boiler. As with any commercial product, the material costs are a fraction of the labour costs. Even if the cost of copper were to double, the cost of a commercial boiler would only increase 10%. The real risk to the future of copper model boilers is that the plumbing industry will stop using copper altogether and suitable size copper tube will no longer be manufactured.

Copper is more common in the earth's crust than lithium, so the battery materials will run out first, assuming the hydrogen economy proponents don't win the argument.

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Re: Larger scale Stuff

Post by GTB » Thu May 02, 2019 1:13 pm

Busted Bricks wrote:
Wed May 01, 2019 8:57 pm
I've got a 10-bottle battery of nitrogen sitting in the yard. 200bar pressure! I'm pretty sure they are less than 6mm wall thickness.
To some extent that is comparing apples to oranges, if you are comparing the gas bottles to mild steel steam boilers.

High pressure gas cylinders are hot forged, so the metal is stronger and they are filled with a dry, inert gas. They may also be coated internally.

As Rod suggested, to get corrosion you need oxygen and moisture and neither are present in a compressed nitrogen cylinder, so there is no need for a corrosion allowance on the cylinder wall thickness. The thickness is based on having adequate shell strength for the designed pressure.

The steel boilers in use on large scale locos have to allow for corrosion wastage and are also made from pipe designed for things like gas pipelines. There is a longitudinal weld and the steel used is hot rolled plate, so strength is lower and the plates have to be thicker for both strength and corrosion reasons.

A borescope inspection won't tell you much except that the boiler is rusty inside, but cheap ultrasonic thickness meters are now available and can be used from the outside to measure any reduction in shell thickness due to corrosion.

No idea how it works in Europe, but here in Oz,the Australian Standard AS1228-2006 overrides whatever the clubs and the AMBSC come up with, so it would be possible to build a small steel boiler that could be used in public and sold commercially, but it requires design approval by an accredited design engineer, traceable steel test certificates, welding by a welder with the necessary specialist welding tickets and final approval by an accredited boiler inspector. It would cost a fortune, much of which would go to pay the engineer's, welder's and inspectors liability insurance premiums.

Design a suitable steel sub-miniature boiler and get your welder mate to weld it together. Test it in your own backyard on a chassis and see if it works. Then run it regularly and check the shell thickness from time to time to see what the corrosion lifetime is likely to be.

Otherwise it's all idle speculation..........

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Re: Larger scale Stuff

Post by workwright » Thu May 02, 2019 6:43 pm

Hi, what an interesting discussion above. I am the owner of a large (1/3 scale) Quarry Hunslet. I puchased it over a year ago now and after having had some fun with it am just about ready to rebuild it and get it looking good. I purchased the loco from a Model Engineering Club with an active Hydraulic and Steam test certificate. Following a lot of local chat and articles coming up on the 7 1/4" Gauge Society forums and newsletter I am happy with my puchase since it has 200lbs + of copper in a professionally made boiler sitting on its frames. I have just read an article writing that "with the new regulations copper boilered locos will be at a premium". This seems to be based on the assumption that under the new regulations the hydraulic test (every 7 years) will require the steel boiler to be removed from the locomotive , the cladding and insulation removed and an external inspection be made of the external condition of the boiler before hydralic testing. The reason for this is serious corrosion can occur to the barrel under the cladding. Small weeps from fittings saturate the insulation causing the rusting. Clearly this could be prevented by the boiler being powder coated before fitting to the chassis. The feeling I get is that a steel boiler is only going to be good for 3-4 Hydraulic tests and probably if steel tubed will need a retubing along the way. A copper boiler does not need to be inspected in the same way under the new regs. The main worry with the cooper boiler is have the stay ends within the fire box erroded due to poor care of the fire, is the crown of the box ok? This can be done on the loco with a torch and a mirror ( these days with a £30 inspection camera from ALdi you can take out the blowdown plugs and check for clag building up on the foundation ring as well.)
Say you are unlucky - you fail the Hydraulic. The steel boiler is 200lb of scrap hardly worth taking to the scrappy ( £0.08 KG), 200lbs of copper with a pound of silver solder on it is worth something (£3=90KG). So I think buying a loco with a steel boiler over 14 years old is a bit of a gamble. A copper boiler for my loco will cost about £5000 at the moment, a steel one about £1000 less. Plus you are going to have to take it off every 7 years..........
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Re: Larger scale Stuff

Post by Big Jim » Thu May 02, 2019 8:05 pm

Oily Rag wrote:
Thu May 02, 2019 4:01 pm
tom_tom_go wrote:
Wed May 01, 2019 8:07 pm
The regs for small scale live steam are pointless, we discussed this a while back:

viewtopic.php?t=11193
Heaven knows I agree with you Tom. Unfortunately a number of people jumped on a band wagon and have caused us all a lot of unnecessary pain is the best way and most diplomatic way I can put it. I had the good fortune to be asked to be present at a respected Model Engineering Society's test of small boilers like ours (even the largest we are likely to encounter or use). This test was to test a couple of boilers under controlled conditions to absolute destruction. Regardless of all the scare mongering stories these went off with a dull "PHUT" and spilled some hot water on the stone deck. None even splashed up the surrounding stack of bricks.

And when you actually stand back and do the scientific calculations the amount of energy (the stuff which makes big bangs actually) which is stored in our boilers is so small that once a small breach is made in the containing shell the pressure drop is so rapid as to dissipate all the energy so rapidly nothing like the alleged big bangs happen. They actually can't. Yep some one may get a less than a life threatening scald if they are being foolish but in general---------- common sense should prevail.
This is very interesting, I have always fancied testing a boiler or two to distruction. We had a boiler at the club that had failed a hydraulic test and was not worth repairing. Sadly before I could get my hands on it some blighter sectioned it.
The only failure I have ever seen was on a home made oscillating engine (mamod stationary clone). Soft soldered boiler failed at a joint after being run nearly dry, it blew a bit of flaming meths about but the damn thing had gone out before the owner managed to squirt water at it.
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Re: Larger scale Stuff

Post by Busted Bricks » Thu May 02, 2019 9:14 pm

GTB wrote:
Thu May 02, 2019 11:33 am
The real risk to the future of copper model boilers is that the plumbing industry will stop using copper altogether and suitable size copper tube will no longer be manufactured.
Just roll it from a piece of sheet and join with a strap. I've made boilers that way.

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Re: Larger scale Stuff

Post by Keith S » Mon May 06, 2019 4:34 am

workwright wrote:
Thu May 02, 2019 6:43 pm
Hi, what an interesting discussion above. I am the owner of a large (1/3 scale) Quarry Hunslet. I puchased it over a year ago now and after having had some fun with it am just about ready to rebuild it and get it looking good. I purchased the loco from a Model Engineering Club with an active Hydraulic and Steam test certificate. Following a lot of local chat and articles coming up on the 7 1/4" Gauge Society forums and newsletter I am happy with my puchase since it has 200lbs + of copper in a professionally made boiler sitting on its frames. I have just read an article writing that "with the new regulations copper boilered locos will be at a premium". This seems to be based on the assumption that under the new regulations the hydraulic test (every 7 years) will require the steel boiler to be removed from the locomotive , the cladding and insulation removed and an external inspection be made of the external condition of the boiler before hydralic testing. The reason for this is serious corrosion can occur to the barrel under the cladding. Small weeps from fittings saturate the insulation causing the rusting. Clearly this could be prevented by the boiler being powder coated before fitting to the chassis. The feeling I get is that a steel boiler is only going to be good for 3-4 Hydraulic tests and probably if steel tubed will need a retubing along the way. A copper boiler does not need to be inspected in the same way under the new regs. The main worry with the cooper boiler is have the stay ends within the fire box erroded due to poor care of the fire, is the crown of the box ok? This can be done on the loco with a torch and a mirror ( these days with a £30 inspection camera from ALdi you can take out the blowdown plugs and check for clag building up on the foundation ring as well.)
Say you are unlucky - you fail the Hydraulic. The steel boiler is 200lb of scrap hardly worth taking to the scrappy ( £0.08 KG), 200lbs of copper with a pound of silver solder on it is worth something (£3=90KG). So I think buying a loco with a steel boiler over 14 years old is a bit of a gamble. A copper boiler for my loco will cost about £5000 at the moment, a steel one about £1000 less. Plus you are going to have to take it off every 7 years..........
There are some very interesting points in this post. Like so many things making an economical decision has an element of chance. All things considered I think I'd rather pay the extra for a copper boiler. Of course steel is a tried-and-true material for full-sized machines, but of course full-sized machines can earn their keep, while models seldom do.

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Re: Larger scale Stuff

Post by tom_tom_go » Sun Jun 23, 2019 3:43 pm

I went along today to the model engineering society I hope to be a member soon and there were a couple of 5" narrow gauge looking locos I though you all might be interested in seeing:

IMG_20190623_145737-01.jpeg
IMG_20190623_145333-01.jpeg

'Lucky 7' below is 3 1/2" and dwarfed in size everything running today!

IMG_20190623_144943-01.jpeg

I had not considered this gauge before, however, after seeing this one I would if something second hand I liked came along.

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Re: Larger scale Stuff

Post by idlemarvel » Sun Jun 23, 2019 5:55 pm

Very nice. The 3 1/2" gauge American outline loco looked the part. Is this the gauge you were thinking of?
Dave Miller
currently building the 5" gauge Circle Line

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Re: Larger scale Stuff

Post by tom_tom_go » Sun Jun 23, 2019 6:11 pm

Hi Dave,

'Lucky 7' certainly does look the part, one of only two made by the same builder. The one I saw today was apparently the 'first attempt' but looked great to me!

I am looking at 5" gauge, however, narrow gauge in 3 1/2" is bigger than I thought it was so could be an option.

Money no object, I would buy this RTR:

https://www.stationroadsteam.com/staffo ... -stfc5040/

Kit option is also available but would take me many years to buy all 12 kits!

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Re: Larger scale Stuff

Post by idlemarvel » Sun Jun 23, 2019 6:51 pm

The problem with 3 1/2" (in my eyes) is that you need a raised track so passengers can straddle the rails. Makes points a bit tricky. You can get away with ground level with 5" (I'm hoping this is really true!).
Dave Miller
currently building the 5" gauge Circle Line

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Re: Larger scale Stuff

Post by tom_tom_go » Sun Jun 23, 2019 6:56 pm

The club I am joining has a raised track so that was my thinking with 3 1/2" gauge.

5" gauge is fine for ground running.

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Re: Larger scale Stuff

Post by Busted Bricks » Sun Jun 23, 2019 7:20 pm

My dream loco would be a quarry Hunslet or a Bagnall for 7 1/4" track.

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Re: Larger scale Stuff

Post by tom_tom_go » Sun Jun 23, 2019 7:35 pm

The loco I posted from SRS is the same size in 7 1/4" so you get the benefits of a large loco on 5" gauge track!

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Re: Larger scale Stuff

Post by Big Jim » Mon Jun 24, 2019 10:21 am

Interesting Locomotives.
Are they a pair of Russells?
Narrow gauge on 3 1/2" can make for some very large engines, my Mountaineer is a two man lift and is capable of public haulage all day long and the club's Dholpur is about 5ft long and 5" gauge. It's sister engine was used at an IMLEC competition and rumour has it, they ran out of things for it to pull.
Regarding the raised vs ground level debate. I prefer running on raised track, for those of us who are not as flexible as they once were, running 5" on the ground can be a bit awkward especially if, like me you are 6ft tall and proudly carry a not inconsiderable liquid grain storage facility (beer gut).

Glad to see you are starting to get the bit between your teeth Tom.
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