Brass or Stainless

First if all this is UK based. I am in the process of making a locomotive tender in 3 1/2", this means I need to form bends and rivet and solder lap joints etc, to make it water tight.

Now with the price of brass being what it is I can buy a sheet of 304 stainless for probably a quarter of the price. I know I can buy ready made laser pieces and all that, my question really is just has any one else, and I am sure there is someone, done just that and if there were any problems.

Not sure if this is relevant, Howard ... but anyway:

Years ago I was discussing the possibility of using stainless steel for a box-section car chassis, with someone from a famous manufacturer of GRP-bodied sports cars.

He said they had tried it, and suffered fatigue failures at the folds; and were therefore continuing to use galvanised steel.

• Things may have changed in the last 30+ years

MichaelG.

Howard

Not done it but I have made my tender body from mild steel to my own laser cut patterns. Having worked professionally with sheet stainless I see no real issues. You will want annealed stainless if you are intending to bend it. Remember it works hardens as you bend so you only get one shot at it. Drilling is not an issue providing you lubricate and keep the pressure on while doing it. Soldering needs the flux that CUP sell, but I have had no issues with it. Best thing is to try some test pieces or a small part of the tender. first.

Dave

Hi Howard, brazed stainless and water are not a great mix. The joints can suffer from what is known as 'crevice corrosion' something no one has really been able to explain. Nickel bearing stainless such as the 300 range are more resistant to this so 304 should be ok. Just a word of caution.

I would not have thought it is going to be brazed, soft soldered at the most though you could try an epoxy

Austenitic stainless steels suffer from intergranular corrosion if exposed to chlorides in the water. It was a problem in atomic reactors that brought this to light. So if you make a stainless boiler from these steels you need demineralised (not deionised) water to feed it. A reverse osmosis unit as used for topping up marine aquariums should be able to meet this need.

Martin C

Many years ago some well respected model engineer described in ME how he built a tender with angle corners and rivets, all joints sealed with epoxy which he cured in the domestic oven at low temperature. I rather suspect that aircraft fuel tanks are built on these lines. With modern glues I don't see why this shouldn't work, just be careful that the glue is compatible with SS, some chemicals are not.

Thanks for the replies. I had thought of using a sealant rather than soldering just forgot to mention it. I don't think corrosion, what ever causes it, needs to be a problem as I am sure it will out last me. My first thought was to use plain sheet steel rather than stainless and may still do if I can find an internal finish that will prevent serious rusting. Over the years I have dealt with stainless in designs from food to marine, but they all were either welded or bolted construction and nothing as light as this.

Hi Howard.

Your problem is being over egged!

Your tender is not going to be subject to any temperature. There is no need for a silver solder. No matter what material you decide upon the joints can be made with a soft solder. Just use the appropriate flux.

If you use stainless steel, then use a flux suitable for it. You can still use tin/lead or tin/copper. Your choice but they will leave a black or grey joint line. Does that matter if you are going to paint it?

If it does matter then use a silver/tin alloy. You won't see the joint.The spouts on stainless steel kettles were soldered with such an alloy. Corrosion ? What corrosion? Beer engines and shop signs are still assembled using it.

It really is a simple situation. Use your common sense and just do it!

If you want any more information then consult BS EN 14324 or my book which is written around it! A point to bear in mind..... you can buy 10 books for the price of one copy of the BS!

Keith

Thanks Keith, I have your book, read though and dibbed into it quite a bit. Most of my silver solder work has been correcting machining cock ups, I have some soft solder, a couple of different rolls have to check what they are but lead free as used for copper plumbing, which I used to do a bit of. At the moment I don’t have any stainless sheet to experiment with but when I do I will experiment a bit. As you say things get a bit over thought, we are not building for the nuclear industry.

When I have experimented I will get back.

Regarding comments about crevice corrosion, inter granular etc wouldn't bother you. You are talking cold water, no pressure and a lifetime of perhaps 50 years, after that, it aint your problem I suspect. Go for it, just get something you can drill through and soft solder for fittings (brass or bronze) - stainless if you want.

Good luck

It is a locomotive tender tank that we are talking about, how often will it be full of water, about half a dozen times a year, a dozen times in a good year, and the rest of the time probably stored empty, as Keith says the problem is being over egged. Soft solder, epoxy resin or even JB weld will seal it up perfectly adequately.

I have a stainless steel tender body that will go eventually with a Gauge '3' Pacific (A3) Howard.

It's very nicely made (not by myself I'm afraid) and I think it might have been TIG welded - although I'm not absolutely certain. It's a very nice job though, the joints are very even and smooth in appearance - and definitely not soft soldered.

If you are interested in a closer look, I'll take some photos of it for you.

Regards,

IanT

OK - the Wife has gone to bed and I'm not going to watch any more coverage of the US Election tonight (that's for sure!) It's also too late to tidy up a worktop and I've got stuff all over the place, so just some quick shots.

But I think you will get a general impression of the tender body from these pics Howard. Hope this helps.

And that's Goodnight from me now too

IanT

If you want to use mild steel which a lot of the larger traction engine tenders are made from then look at one of the fuel tank sealants such as POR-15 which is what they often use.