Sight "glasses" and soft solder

A very popular starting point for Live Steam. With their low cost comes a number of problems which can be discussed here
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Boustrophedon
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Sight "glasses" and soft solder

Post by Boustrophedon » Thu Jun 20, 2013 8:44 pm

Not strictly loco related: The school science department in the school where I work has a shelf full of Mamod and Wilesco static steam engines. Every single one has been allowed to boil dry and on every single one, the solder has run from the boiler joints. On all the Mamods the sight glasses have also melted being made of plastic.

I could repair them, the spares are available and re-soldering a boiler is a plumbing job. But I am inclined not to do so because of my liability. I think we shall Ebay them as "spares and repairs".

Has anyone had a problem with sight glasses on Mamod Locos?

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Post by dougrail » Thu Jun 20, 2013 8:50 pm

Oh hell yes. The plastic push-fit sight glass system is one of the more vulnerable parts of the original Mamod loco design, susceptible to moving o-rings, leaks, melting from either a cab fire or from overheat on the burner....I've had at least two boilers which have griefed me at this end.

[Anyone got that pic of Second Chance blowing its sight glass from Butterley?? :lol: ]

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Post by paullad1984 » Thu Jun 20, 2013 9:33 pm

No but ive seen what happens when someone puts a high pressure valve onto a standard mamod boiler and the sight blows out whilst the engines moving, hilarious!

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Post by Chris Cairns » Thu Jun 20, 2013 11:45 pm

The Science Department obviously did not 'police' the importance of keeping the water level above minimum.

If the Mamod engines are current models still sold by Mamod Limited, why not send them back to Mamod for a factory repair - that should cover any liability issues.

The problem with Mamod SL/MSS sight glasses leaking is the result of 2 changes to the original specification: -

1. The depth of the punched boiler rear end has been increased by MSS so you need a deeper seal. Also the MSS boiler is only available with a screw fitted back plate and the threaded boiler inserts for those screws have a raised collar that effectively moves the back plate further away from the seal.

2. The original oval sight glass rubber seal was changed in the 1980's to a thinner 'O' ring which compounded the sealing problem.

As the sight glass is plastic they all will eventually fail, particularly as most owners use a meths or gas burner which effectively raises the boiler temperature above that achieved by the solid fuel burner.

The current Mamod locomotives use a thicker oval rubber seal and a thicker rectangular sight glass plastic, but they are all gas fired and get very hot due to poorly designed combustion chambers, so I've already had one of those thick plastic sight glasses fail despite sufficient water in the boiler.

Chris Cairns.

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Post by Boustrophedon » Fri Jun 21, 2013 6:26 pm

Chris Cairns:84993 wrote: If the Mamod engines are current models still sold by Mamod Limited, why not send them back to Mamod for a factory repair - that should cover any liability issues.



Chris Cairns.
Thanks for that advice, we will do so.

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Post by Boustrophedon » Sat Jun 22, 2013 4:41 pm

..Except for the one I brought home to look at, it would appear that the brass boiler has corroded, water is leaking through metal of the end plate.

Not safe.

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Post by Chris Cairns » Sat Jun 22, 2013 5:33 pm

Welcome to the world of Dezincification.

Whilst I've not suffered it on any of my brass boilers so far it does seem to affect the end caps more than the boiler barrel. Again it is quite easily repaired either by soldering a brass plate on the inside of the end cap (if it is not a big hole), or much better to replace the end cap.

Here is a waste bin Mamod SE1A which I got from eBay some years ago. It had obviously been thrown down the stairs (or something similar) causing the chimney to put a large dent on the top of the boiler and pulling it's retaining rivet out.

Image

After removing the end cap I soldered in a new insert for the water level plug and using a wooden former I managed to smooth out most of the dent and soldered in a 6BA screw to allow the chimney to be retained.

Image

Whilst it still waits its turn in the paint shop it is now a fully functioning steam tight engine again.

Image

Remember these Mamod stationary engines were designed under the Toy Regulations and thus operate to a maximum of 1 Bar/14.7 PSI pressure so any leaks, etc. are not going to cause a catastrophic boiler explosion like those recorded on some full size boilers operating at a much higher pressure and volume.

Chris Cairns.

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Post by Boustrophedon » Sun Jun 23, 2013 1:58 pm

I have a Mamod engine that was given to me on my fifth birthday, that makes it 50 yrs old, it's dirty, the iron parts are slightly rusty, but it works perfectly.

The ones from the science department look unused, are shiny and bright but areas of de zinced brass are showing on all of them, with green corrosion . Ok so they have been misused and I suspect that the science department have run them on distilled water which doesn't help.

But mine has always been run on meths, the ones from school have been always run on solid fuel. Is there something in the residue from the solid fuel that causes the brass to corrode?

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Post by Chris Cairns » Sun Jun 23, 2013 3:38 pm

Don, I'm no expert and there does seem to be a lot of so-called experts with differing views elsewhere on-line but the use of de-ionised water (which is actually what a lot of distilled water sold in the UK really is) has been linked to dezincification of brass boilers.

The Solid Fuel is certainly corrosive particularly when stored in damp conditions. I have a used solid fuel burner tray where the residue was never cleaned out which is corroded and full of small holes, and I've seen photos and experienced first hand what an open pack of solid fuel can do to a stored Mamod locomotive - it tarnishes the brass fittings like the buffers & cylinders and causes a strange powder like corrosion of the mazak (zinc diecast) castings.

The other problem with the current Mamod engines is their mainly riveted construction which makes dismantling and a proper clean up more difficult. It is much easier to take apart the earlier models for cleaning particularly if you have been running them on our dyed blue domestic meths which leaves a very sticky residue.

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Post by Narrow Minded » Sun Jun 23, 2013 3:55 pm

Chris Cairns:85086 wrote:..... running them on our dyed blue domestic meths which leaves a very sticky residue.

Chris Cairns.
For what it's worth, I've successfully removed the dye and run my loco's on the "cleaned up" version - with more or less the same gunk build up.
Obviously it's caused by some of the contaminants that are in this cheap version of methylated spirit, and it's now one of my priorities to source some decent fuel (Chuffed 2 Bits sell it, but I intend sending off the application for a "licence to hold")
Image

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Post by Chris Cairns » Sun Jun 23, 2013 4:55 pm

Having started on the usual B&Q and other DIY stores 500 mls bottles of blue meths I found ye olde style hardware store in town which sold it in a 5 lts container. Having used up that supply I bought another 5 lts container from the same source. Despite having the same label on the outside I was pleasantly surprised to find it contained clear meths which actually has a fouler odor, but does burn much better.

I had considered getting the HMRC Denatured Alcohol licence but the problem had been finding a local supplier willing to deal with the 20 lts limit at a reasonable cost. However some recent browsing has suggested that it is readily available from French Polishing outlets and I've found a local outlet that would sell 5 lts for £14:34 inc VAT.

Chris Cairns.

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Post by Boustrophedon » Sun Jun 23, 2013 5:39 pm

B&Q now market something they call Bio-ethanol (what other sort is there, given that  alcohol is made by fermentation?) for indoor flame effect stoves. Not tried it yet as I have never had problems with the blue stuff.

http://www.diy.com/nav/rooms/fires-surr ... d=13319274

Price is good.

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Post by Boustrophedon » Thu Jun 27, 2013 6:11 pm

Turns out the tap water in Stevenage is foully acid at pH 5, this probably accounts for the de zincing of the brass boilers.

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