Mamod 0-4-2T SL1K Refurbishment

[Chris Cairns]

Having completed a few projects and obtained some Mamod/MSS spares this stalled project can now progress.



As purchased this loco would not run due to the front wheels being loose on their axle. As I was making up 2 more wheel sets for other locos at that time I decided to fit a set of Dream Steam plain steel wheels to this loco. However it took a far bit of time to get those wheels aligned properly so that they were free running. The running proved that the rear trailing axle was ineffective and the Merlin gas burner burnt with a very yellow flame and lots of soot so the bunker & gas burner were removed, and a drag beam sourced to allow fitting a meths burner.



I did get the loco to run in this configuration but it was not very spirited so I suspected some blockage or leak in the steam path, and it was parked to await a refurbishment.



It has now been completely stripped down.

1. It is fitted with Mike Chaney modified 'O' ring pistons. I am re-lapping the cylinders and fitting new MSS gaskets.

2. Wheels. One problem I've seen with the after market steel wheels is they suffer from corrosion with use (as proven by some of the members photos on here). I have set of IP Eng black holed disk wheels which I'm re-gauging to 32mm. These have been treated for rust and primed up. The disks are being painted red and the backs will be black. I also have a set of the RWM Steam coupling rods to fit. I'm told that these rust easily as well so they have been primed and are also being painted red & black.

3. The boiler is a Mike Chaney replacement high pressure one with his water top-up valve & high pressure safety valve but uses the standard Mamod steam dome. This had some strange deposits in the water so it has been soaked in vinegar for 48 hrs and flushed out. I will be soldering in 2 x 6BA nuts for securing to the smoke box/bodywork, replacing the posidrive screws with 6BA screws. It has a 6mm sight glass tube at the rear which works very well, however it has cracked 2 tubes so far so the bottom fitting will need looking into.

4. It has a cab mounted Mike Chaney regulator which has been cleaned up and sealed to prevent leaks. This is currently fitted with a rather crude operating arm and coupling. I am waiting until the refurbishment has been completed to see if it is practical to use radio control on this regulator. This will depend on how much control will be available for a range of 120 to 180 degrees of servo movement.

5. The Merlin gas burner is being refurbished. By using the right mesh these can actually be a very good radiant burner. The recommended mesh is nichrome which is only really available in the USA, so I have used a fine stainless steel mesh instead. This just needs a little more trimming and some more fine wire to secure it.

6. It has a Mike Chaney (the original designer, later copied by IP Eng & Dream Steam) dead leg lubricator which works well. However the main steam pipe into the lubricator T piece soldering has failed so I need to get these aligned properly and then re-solder.

It is not my intention to repaint this loco until I have got it running properly. However it is taking some time to paint up the wheels and coupling rods so photos will follow soon. I'm still trying to work out an effective method of mounting the rear trailing axle, otherwise an alternative may be a tender locomotive instead.

Chris Cairns.

[Spule 4]

The recommended mesh is nichrome which is only really available in the USA, so I have used a fine stainless steel mesh instead.

Chris Cairns.

Is this something I could help you with Chris?

[Chris Cairns]

Thanks for the offer Garrett but I've got enough stainless steel mesh for now.

Apparently stainless steel mesh will eventually burn out whereas nichrome is long lasting..

I know there are a couple of members here that use the Merlin gas burner so maybe in the future there will be a requirement for some nichrome mesh. The method used by Merlin when fixing their mesh was very inefficient so they tended to run as a naked flame burner when in fact as a radiant burner they are more efficient and longer running.

Chris Cairns.

[Spule 4]

Thanks for the offer Garrett but I've got enough stainless steel mesh for now.

Apparently stainless steel mesh will eventually burn out whereas nichrome is long lasting..

I know there are a couple of members here that use the Merlin gas burner so maybe in the future there will be a requirement for some nichrome mesh. The method used by Merlin when fixing their mesh was very inefficient so they tended to run as a naked flame burner when in fact as a radiant burner they are more efficient and longer running.

Chris Cairns.

OK. The offer stands tho!

[Chris Cairns]

Not had much to report on this Refurbishment as I've been struggling with some painting in our Winter conditions.

Boiler - Finally got some 6BA brass nuts soldered into the front face of the boiler for securing to the smoke box. Having paint stripped and cleaned up the boiler I tried painting it direct with a BBQ paint which rippled. So paint stripped again, then primed with U-Pol Acid#8 and first coat of BBQ paint not too bad. However on applying a 2nd coat of BBQ paint the back face has decided to ripple. So I'm just going to wait for this to dry and will bake it in the oven. Getting the boiler back has been delaying any progress with running trials so I'm not going to repaint again for now.

Wheels - This model came with a set of loose Mamod wheels. I have taken these apart to replace the Mamod peened axles with a fixed steel axle with the wheels held on by Loctite 603. However the Mazak does not like being spray painted so I'm slowly hand painting the rear axle wheels in red. I had fitted a set of Dream Steam plain steel wheels to get this loco working earlier and I've obtained a set of Peter Jones's wheel inserts to improve the looks of these wheels. However these inserts need a bit of filing/sanding to fit my wheels, and I'm still not sure how to paint them up yet. So they will not be used on this loco for now. I also have a set of 45mm IP Eng holed disk wheels which I have been re-gauging to 32mm. I've just baked the front axle wheels and fitted them to the chassis frames to find that the coupling rod pins are too thick and will not fit into the brass big end on the piston rod. So I'll need to file those pins down to size somehow.

Coupling Rods - I obtained a set of Roy Wood Models reprofiled replacement coupling rods. These were painted up only to find they need a little bit of reaming out to fit on the coupling rod pins. Interesting to note that whereas Mamod & MSS supply washers to go either side of the brass coupling rod, these replacement steel coupling rods by IP Eng, PPS & RWM are slightly thicker and are not supplied with washers for fitting. I personally think a washer is required to stop the e-clip rubbing against the coupling rod on the top, and a washer below the coupling rod helps to keep it away from rubbing the wheel rims. However I've mislaid my bag of nylon washers somewhere!

So still some time away from getting a running chassis sorted out. Once I've assessed how much the Mike Chaney regulator needs to be moved for full control I will decide whether to fit Radio Control on the regulator again (have a possible plan to use a model boat steering rudder arm on the regulator with ball arms and offset control linkage).

Chris Cairns.

[Chris Cairns]

My plan to match an IP Eng front axle with a Mamod rear axle did not work out as these wheels are just slightly different sizes and the coupling rods ended up at a bit of an angle causing some binding.

So I cut the rear axle of the IP Eng wheels and Loctite 603'd them together.

I now have a complete rolling chassis again. Just need to watch that the IP Eng wheel rims do not foul the combustion chamber when it is re-fitted.



Just waiting for the boiler paint to dry then I'll bake it. Boiler fittings have been cleaned up and I just need to cut a new length of 6mm glass tubing for the sight glass. Once the boiler is back in place I can sort out the main steam pipe/dead leg lubricator solder joint.

Chris Cairns.

[Chris Cairns]

One baked boiler. The reason for leaving a bare portion on the bottom is to hopefully improve heat transfer from the burner (we paint these boilers with VHT paint but that apparently affects the heat transfer from a burner to the pot boiler).



This is a Mike Chaney silver soldered 50PSI replacement boiler which is the same dimensions as the original Mamod boiler. At the front is a 1/4"x 26BSF insert with a Goodall type water filler valve. The standard Mamod steam dome nut & cover is used, with the steam outlet pipe going back towards the cab sighted regulator. Strangely the high pressure safety valve (which is not adjustable) is 1/4"x 40ME. At the rear we have a 6mm sight glass tube (glass replaced and copper wire inserted to help with no air bubble formation), and a Mike Chaney regulator.

I now need to clean up the regulator steam outlet pipe and solder it back into the dead leg lubricator.

Chris Cairns.

[Narrow Minded]

Very nice set-up and a neat restoration job Chris

I must say, I've never heard of any black paint being much of a hinderance to heat transfer.

[Chris Cairns]

I recall reading a discussion on whether to paint pot boilers or not some years ago (may have been on the Unofficial Mamod Forums).

This loco arrived with a Merlin gas burner fitted. However these suffer from the wrong type of mesh and the method used to secure that mesh, so this one was very inefficient (barely raised steam).

So I've been running this loco as a meths burner and when I came to paint strip the boiler the paint which had been contaminated by the meths residue would not move. So I had to sand it off.

Until I've got it running well it will continue to be a meths burner (I've managed to get some clear meths so hopefully less residue problems) as I do not intend fitting the roof or cab back during the running trials.

The refurbished Merlin gas burner will feature here at some point.

Chris Cairns.

[Superbiker_uk]

Excellent progress Chris and another interesting thread!

[Chris Cairns]

So got the main steam pipe to dead leg lubricator joint soldered up.

Putting the loco back together proved tricky as the sight glass fittings are longer than the aperture formed by the back of the combustion chamber and the cab front, so meant trying to get a nut on a combustion chamber to cab front screw with the boiler in place.

Left the smoke box & chimney off and replaced the chuff pipe with a short piece of 1/8" pipe so no exhaust restriction.

Steam test came up with a couple of steam leaks. Firstly in my eagerness to run this loco again I forgot to tighten up the front reverser valve to chassis frame screws - quickly sorted out. One of the regulator glands was leaking but that just needed a bit more tightening up against the PTFE tape fitted on the threaded portion. But the bottom fitting on the sight glass tubing is leaking. I just replaced this glass tubing but used the original cut pieces of silicon tubing being used for seals. Some manufacturers use 'O' rings for seals here but it is finding a thin enough 'O' ring to fit inside the gland nut collar. If I cannot find a suitable 'O' ring I'll try some more cut silicon tubing.

The dead leg lubricator is working well. However the IP Eng wheels & RWM coupling rods are showing signs of stiffness so a fair amount of running in will be required.

Chris Cairns.

[Narrow Minded]

so meant trying to get a nut on a combustion chamber to cab front screw with the boiler in place.

Just been there and gave up - a self tapper came to the rescue when the shed foreman wasn't looking!

[Chris Cairns]

I have a very good 6BA ring spanner but Mamod put all those screws too close to the sides on the cab front so it will not go over the nuts for the side tank to cab front, combustion chamber to cab front, and cab front to side tank cab floor (I put the nut on the inside of the cab). Need to get a suitable flat 6BA spanner.

I eventually got it fitted using a pair of narrow long nose pliers.

Not a fan of self tappers that tend to work loose through vibration.

Chris Cairns.

[Chris Cairns]

Update.

Leaking sight glass tube - It was the lower fitting that was leaking. As I have no suitably thin 'O' rings I cut 2 slightly longer pieces of silicon tubing and there is now no leaks.

Stiffness - One problem I find with fitting the after market steel wheels is due to the method used to hold the bearings into the chassis frames there is no play like the original Mamod/MSS wheels & bearings so these steel wheels pick up any slight variation in the frames (they are made of a thin soft steel and thus easy to bend). So this loco has been running somewhat stiffly. I've removed the RWM coupling rods and it is now running freer as an 0-2-2T. Will need several runs on blocks for everything to bed in and I'll need to ream out those coupling rods some more.

Meths Burner - Last year I finished my 5lts supply of purple meths. When I bought a replacement (same make & label from same trader) I was surprised to find it was colourless. I had some flow problems with a burner on a Bowman locomotive and had to flush that out using acetone. The burner I'm using is one of the ones sold by Chasteam (amongst others) and it has sat around for a while as I trimmed the original mounting (it hung lower than the IP Eng/Dream Steam ones and was thus less efficient). The front wick is having problems staying lit, and despite adjusting the wick which worked for one run, it is back to not burning well. So I'll need to flush out this burner to remove and crud, etc.

Regulator - The Mike Chaney regulator works very well now and once I've sorted out the stiffness and the burner I think an R/C servo on the regulator will work out OK.

Chris Cairns.