So my fourth live steam loco is this MSS Saddle Tank.
It was purchased new on ebay a couple of years ago, and it was intended to remain on the shelf until I have a Garden Railway to run it on. However, given the bad experience of another Forum's member with this model of loco I decided to get it run-in.
I removed the Saddle Tank to ease fault finding (a wise precaution, but not easy to achieve as it needs the saddle tank bodywork pulled over the smokebox slightly which is now scrapped, actually de-riveting the smokebox from the boiler and removing it from the chassis allows the saddle tank to slide forward off the boiler), and took it apart where possible. The wheelset appeared to be punched onto the axles OK and are very free running. The baseplates for the cylinders had a lot of metal burr, so these were removed, cleaned up and re-faced. A large blob of solder was removed from the boiler just behind the steam nut, and the soldering of the steam pipe to the boiler tube insert was very sloppy.
I started to raise steam using solid fuel. The first attempt was a disaster as the soldering of the ring onto the safety valve had contaminated the face of safety valve so it leaked water which put out the forward part of the solid fuel. That has been corrected, and I then found that this engine suffers from severe priming making steam runs very short at that time.
I was advised at the time that MSS boilers needed to be flushed out several times, and after doing that it seemed to improve. However this priming problem continued to affect this loco.
Having got it to run on track, I was curious to find out what lay underneath the false steam chest, and to answer whether this loco can be upgraded like other Mamod/MSS locos. The bodywork is held together by rivets so removing the rivets holding the running plates, side tanks and cockpit front plate together, and the second set of rivets holding the cockpit front plate to the side tanks revealed all!
The second boiler fixing had an insert soldered into it making it very difficult to return this to a normal boiler fitting without some major surgery.
I was suffering from a serious priming problem which was leading to dangerously low boiler water levels and led to my first melted sight 'glass'. The route of the problem was linked to the shortness of the steam pipe that was soldered on the top of the boiler pipe, and fitted inside a much smaller steam chest nut. In order to fit under the Saddle tank, MSS had to use a smaller steam chest nut (I have been advised on another Forum that the MSS all in one steam chest used on the side tank locos is the same height above the boiler as the old Mamod steam chest nut), and this left little room for error with the steam pipe length protruding up into this smaller steam dome nut. Mine was obviously too short leading to that severe priming problem.
L to R, the MSS Saddle Tank steam chest nut, the standard Mamod steam chest nut, the standard Mamod brass cover on top of the steam chest nut.
So I ran this loco with a refurbished Mamod boiler, using a standard Mamod steam chest nut. This could only be achieved by loosely fitting the saddle tank mounting screws, as this was bending the running plates. Hopefully you can see this in this photo.
I steamed it up with this Mamod boiler and after a little priming at the beginning, it went around very well on my test loop, and there was still plenty of water left in the boiler after the meths ran out. A result!
I found on starting to drill that insert out that in fact it was a threaded insert and actually removed quite easily. I then refurbished that boiler by soldering up the inserts, steam chest nut insert, boiler tube solder plug on bottom of boiler, and soldered 2 x 6BA nuts to the inside of the front face of the boiler to allow this boiler to be held into the smokebox with 6BA screws. All that soldering may have affected the boiler as I found a very small leak around one of the securing holes at the front (could have had this leak since manufacture as it is difficult to spot when fully assembled), but it was successfully repaired. After fitting this refurbished MSS boiler, I shoe-horned the rather tight circlip holding on the false steam chest to find that this is too small inside to completely hid the water top-up valve, and the hole in the bodywork is not lined up with the rear boiler outlet so you need to bend the bodywork backwards to fit the water top-up valve, and then by lifting the bodywork up onto the lip of the valve the cab is square again.
So to cover up this water valve with the false steam chest the bodywork across the boiler will need to be raised and the hole enlarged rearwards.
Then I tried fitting an uprated safety valve. The hex shaped part of its body is taller than the water valve so will only fit with the bodywork pushed backwards.
However the false steam chest will fit on top of this valve with a very small clearance, so would probably be blown upwards when blowing off steam.
So it is possible to upgrade this loco like other Mamod/MSS locos but requires either a replacement boiler or that second boiler insert repaired, and some modifications to the bodywork.
I decided to leave the water top-up valve fitted as above, and used a thick rubber washer on the steam chest nut (MSS use 'O'' rings) with a longer steam pipe to stop that previous priming problem.
This loco still has a far bit of priming on starting a run (probably because it is still running in), and my runs with the loco were a bit disappointing as it seemed to run out of pressure and needed to be stopped to raise pressure again. It was actually sitting in my workshop (the kitchen) just waiting to be cleaned up and put back in its box in disgust.
However, after deciding to run it one more time before this posting, I found I had left out one of the 6BA screws (D'oh!) holding one cylinder to the reverser/regulator valve, and on replacing that screw it has just run continuously around my test loop pulling 3 wagons, and plenty of water left in the boiler after the meths ran out. It is my intention to raise that bodywork with some sort of spacer/plug so that the false steam chest will cover the water top-up valve, but still be easily removable to allow water top-ups
So my thanks to Garrett (Spule4) for making me get this posting done today.
Sorry this has been a long read, but I'm sure you will appreciate all the problems I faced, and trust it will help those considering buying one of these locos, or owners who would like to modify theirs.
Thanks for looking.
Chris Cairns.
and very informative
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