Leaking steam Dome

Sir Clothem Cap · Post by **Sir Clothem Cap** » Wed Jul 13, 2011 7:25 pm

The steam dome on "Eva" one of my Sl1s has suddenly started leaking steam, I suspect that the o ring has failed but does anyone know where I can buy one from?

EDIT Disaster! I attempted to remove the steam dome nut and it turned and turned. I took the nut off one of my other engines and the thread is only about 5 turns and it came off and went on easily. So The thread must have gone but it won't come off. Any suggestions welcome

GTB · Post by **GTB** » Thu Jul 14, 2011 12:53 pm

Sir Clothem Cap:56254 wrote: EDIT Disaster! I attempted to remove the steam dome nut and it turned and turned.

First thing is to get the plug out. Only part of the thread is damaged, or it would have just blown out under pressure.

All I can suggest is to get a good grip on it with vise grips (locking pliers), so you can rotate it while also maintaining upward pressure, until what's left of the thread re-engages and the plug can be removed. To make it as easy as possible, grip it end on, not from the side.

If you don't know the tool I mean, they look like this

http://www.homedepot.ca/product/vise-gr ... ter/947818

If you are lucky, only the plug thread is damaged and all you will need is a new plug and washer.

If you can't get the plug out, or the thread in the boiler is badly damaged, you'll probably need to find someone that can repair Mamod boilers.

Regards,
Graeme

Sir Clothem Cap · Post by **Sir Clothem Cap** » Thu Jul 14, 2011 6:53 pm

Thanks Graeme,
Further looking reveals its not the threads but the whole insert which the dome nut screws into at fault. This is loose on the boiler but I can't undo the dome nut to get to the insert to have it resoldered. I also asked for advice on the mamod forum where they suggested super glueing the insert to get the dome nut off then resoldering it.

Any ideas Gratefully received

GTB · Post by **GTB** » Fri Jul 15, 2011 11:19 am

Sir Clothem Cap:56299 wrote:Further looking reveals its not the threads but the whole insert which the dome nut screws into at fault. This is loose on the boiler but I can't undo the dome nut to get to the insert to have it resoldered. I also asked for advice on the mamod forum where they suggested super glueing the insert to get the dome nut off then resoldering it.

Oh dear.....

I doubt Superglue would provide a strong enough bond in this case and all it will likely achieve is to make it close to impossible to get a good solder joint during repairs.

The boiler may be repairable, if you have the soldering skills and the facilities, or know someone that does. You'd need to strip off the black paint, then use a suitable size gas torch to heat the boiler in the area of the dome until the solder melts and it just pulls out. Forget using a soldering iron, the boiler contains too much metal and won't get hot enough. Then clean out the joint back to clean bare metal and resolder with suitable soft solder and flux.

Solder/flux choice will be very important. If this is an older boiler it will have been soft soldered with tin/lead solder. Lead free solders have a higher melting point than tin/lead and using lead free for the repair will probably result in other joints melting first.

To be honest, I would now have very deep suspicions about the safety of this boiler. It may have always had a bad joint on the dome bush since it left the factory, but it is more likely that now one soft soldered joint has let go from corrosion/metal fatigue, the others may not be far behind.

If you can afford it, I'd replace the boiler to get the loco back in traffic. 30 quid for a new one is probably cheaper than paying someone to repair an old one in unknown condition and there would be less doubt about it's long term safety..............

Regards,
Graeme

DaveWatkins · Post by **DaveWatkins** » Fri Jul 15, 2011 12:04 pm

I agree with Graeme's apporach. This was how I fixed a loose dome bush on a Mamod. What you need is enough heat to melt the solder so that the bush is locked in place. You can then unscrew the dome. With the dome off you then have an opportunity to make a better job of the soldered joint.

Dave

Sir Clothem Cap · Post by **Sir Clothem Cap** » Fri Jul 15, 2011 4:01 pm

Thanks for all the input. I have a friend who can gas solder so I'll try a repair then get the boiler pressure tested. if it fails the test Then its wait until dreamsteam have a new standard boiler available.

Sir Clothem Cap · Post by **Sir Clothem Cap** » Sat Jul 16, 2011 7:27 pm

Woo Good News "EVA" lives. My Friend cleaned the paint round the joint brushed round some flux and gas soldered it.

After removing the dome nut and checking the solder which had flowed round well the engine was tested using meths firing and it took the pressure unil the safety valve lifted (25PSI dreamsteam up graded one) and ran without a bubble.

A quick rub down and respray of the scorched paint on the tanks
and "Eva" Rejoins the fleet. Once I find what I did with the brass dome

Sir Clothem Cap · Post by **Sir Clothem Cap** » Thu Jul 21, 2011 10:54 am

Dreamsteam to the rescue, I seem to have lost the original boiler dome and decided to get a new one so for the first time ever on my line I have a mss type dome nut on a mamod loco.

The dome changes the profile but at least looks the part rather than a hexagonal nut with centre ring on it.

Sir Clothem Cap · Post by **Sir Clothem Cap** » Sun Jul 31, 2011 3:50 pm

Finally got round to some photos of the repaired "EVA"

Sir Clothem Cap · Post by **Sir Clothem Cap** » Wed Aug 03, 2011 8:51 pm

We Have some wonderful forum members out there. One member kindly offered me a spare dome for free and then sent me a parcel containing a host of mamod spares including 2 domes so after a polish may I present Humphrey No sorry EVA

dougrail · Post by **dougrail** » Wed Aug 03, 2011 8:59 pm

A 3-domed engine..well I never!

Maybe someay we should have a Red Mamod get together?

Sir Clothem Cap · Post by **Sir Clothem Cap** » Mon Aug 08, 2011 11:15 am

Angus was my original Mamod engine so to get angus and eva together with deep thought would be good.

Eva has now got a proper dome in the right place again.

Spule 4 · Post by **Spule 4** » Fri Jul 27, 2012 1:04 am

I just bought a very nice older SLK1 from Simon Whenmouth at Anything Narrow Gauge.

Unfortunately, when doing some light maintenance on the loco, I broke the boiler dome bung loose.

The solder method worked.

I did dis-assemble the loco (to not damage the nice paint on the loco). I used the heat sheld to hold the boiler steady in a vice.

I first "flashed" the dome fitting with the torch and some flux, this made the boiler paint easy to remove with a wire brush. Once clean, I then took more flux and soldered the fitting.

The dome then could be removed, the fittings and main pipe removed, then further soldering was done to finalize the fitting.

Looking at the fitting on this and a damaged boiler I have here, apparently Mamod did not use much of any solder on the bungs!

GTB · Post by **GTB** » Fri Jul 27, 2012 1:45 pm

Spule 4:73250 wrote: Looking at the fitting on this and a damaged boiler I have here, apparently Mamod did not use much of any solder on the bungs!

One of those 'How It's Made' shows on Discovery Channel visited the Mamod factory in one of their episodes.

As I recall, a worker just painted the joint with solder paint, clamped it in a jig to hold things in place and ran a torch around the joint.

You wouldn't catch this little black duck running one at increased pressure...........

Graeme

Chris Cairns · Post by **Chris Cairns** » Thu Aug 02, 2012 12:03 am

The Making a Mamod video is here - http://www.youtube.com/watch?v=V9c83qO08HM

Watch from 1:08 to see them using solder paste on the boiler & fittings, which then goes through a furnace to activate the paste - no blow torches here.

MSS must use the same process as an MSS loco kit I've acquired has little solder evident around the boiler fittings.

This is one area I treat when refurbishing Mamods, particularly the solder fillet on the bottom of the boiler which is not up to the heat generated by some meths or gas burners. I use a plumbers silver based soft solder which has a higher melting temperature than this solder paste.

Chris Cairns.

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