Mamod SL2 / SL3 Refurb/Restoration

[WWLR]

Hello Folks

Yesterday I said hello as a new user in the Introduction section and I'm now going to post some information about my Mamod loco restoration project.

I have a background in Mechanical Engineering and I'm fortunate enough to have a small lathe somewhere in the garage, but I will need to move a few things around to rediscover it!

My renovation project consists of a mostly complete Mamod SL2 or SL3 painted dark blue with a black spark arrester chimney that I bought on flea-bay back in November.




Most people will be quick to spot the lack of pistons, cab back, front buffers, buffer beam plate and coupling hook. No burner was supplied.




Closer inspection reveals a missing chassis spacer and a curious modification to the side tank extensions that form the cab floor.
I suspect the engine may have been used with a meths burner with a full width tank under the cab floor, additionally the main frames appear much newer than the rest of the loco making me think the original ones had been cut off to accommodate the fuel tank and the frames were later replaced with new ones.

Anyway, the reversing valve and pipework are all there, including the 'o'ring, washer and spring under the steam dome.

My first task is to fully dismantle the poor thing and find out what's under the blue paint with a visit to the paint stripping bath.

Regards

Will

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[Narrow Minded]

Nice project to get you started!

If you'd like to PM me your address, I have a frame spacer you can have gratis. (I also have some of the other missing bits for sale if you're interested)

[Chris Cairns]

Hi Will,

Your paint stripper will reveal whether that was originally an SL2 or SL3. A very ugly replacement rivet holding the side tanks to the smoke box. Also looks like the spring on your whistle has 'sprung' or the 'O' ring on the bottom of the whistle rod has perished or is missing as the whistle operating arm is too low.

Looks like this model was previously fitted with a Kenversions Meths Burner, which would account for the lack of chassis spacer, bent metal work in the cab and the new chassis frames. I do not have photos of one of these burners fitted to a Mamod, but know that the rear of the chassis frames were cut out to allow the meths tank to fit below the cab floor.



Greg (Narrow Minded) was good enough to send me some buffers gratis. I can send you 2 of these if you intend keeping the Mamod look at the front of your loco (although it has lost the coupling hook & ring). Alternatively I can sell you an unused SL3 or MSS spark arrester chimney & smoke box (I intend having a clean out of some Mamod/MSS spares shortly).

Chris Cairns.

[WWLR]

Thanks for your comments so far.

Stripping down the loco was pretty straight forward apart from the massive 4mm pop rivets that had been used to re-attach the Smoke box\Boiler\Side Tank assembly.

I have to admit Mamod used some interesting techniques to reduce the part count and simplify the construction of these locos, and I am amazed that such a small boiler can supply enough steam for two double acting pistons!

The wheels are showing the typical Mamod feature of starting to come loose on the axles, and the extended crank pins have a bit of a wobble. (I've been following Chris Cairns' topic 'Mamod/MSS Wheels repair or replace' with interest as it has some very useful info in it.)

The spark arrester smoke stack was loose and fell off the smoke box with little encouragement. It wont be going back on as I much prefer the straight stack design. I would be grateful if someone could tell me the top and bottom diameters, and height of the 'normal' (slightly tapered) chimney.

I'm not too worried about the missing front coupling and buffers as my preference is to go for a centre buffer/hook arrangement with a much deeper buffer beam plate with shaped bottom corners (rounded, angled or concave – probably the latter) and some dummy rivets.

A session with the paint stripper was quite revealing:



The side tanks were originally green (SL1)?



The cab front was green under the dark blue, but further stripping showed purple under the green (SL6)?

Looks like I've got a scrap box special! (polite suggestions for a suitable name for a loco of uncertain parentage?)

I have followed up Chris Cairns' comment about the whistle – it still has its 'o'ring and the spring appears OK but there is little movement before the lever hits the top. Lifting the lever out of the way reveals a 2mm dia brass pin that's a sloppy fit in the hole in the top. Is it easy to dismantle?

Regards

Will

[DolwyddelanLightRail]

Having owning an SL6, I can say that the purple seen is too blue to be from one of them, it's a lot more maroon than that. It looks to me like the MSS Jubilee colour to me

[Chris Cairns]

It is a bit like one of my Mamods I was told was a kit loco (SL1K) but it has SL1 side tanks and non standard screws & nuts holding on the roof which has a riveted cab back clip.

It wont be going back on as I much prefer the straight stack design.

Then part of that chimney will be going back on. The SL2/3 chimneys use the standard straight chimney in the middle with a brass balloon spark arrester body and a brass circular top which is painted black.



The bottom of the chimney stack has a locating tab and was pressed on with a square punch. These work loose because owners picked up the loco by the chimney. Sometimes they can be glued back in place although I know someone has managed to produce a tool which flares out the bottom of the chimney.

Not sure about your cab front. Mamod are known to have made too many parts some times and re-used these by repainting them. However it is unlikely that they would have taken an SL6 cab front (which was a limited edition of 1,100 so why make too many?) and repainted it. More likely that your Mamod has been harvested from the spare parts box by a previous owner (the boiler has a riveted back plate).

I have some never used Mamod wheels and these are already slightly loose on the axles with one or two loose coupling rod pins. I can recommend using Loctite 603 to put these back together once dismantled. I do not have the time to make up a set due to my current projects.

Whistle - read up on-line about taking one of these apart ( http://modelsteam.myfreeforum.org/viewt ... 97&start=0 ). If you heat up the body the top portion should then twist off (there is a small brass piece to be aware of as it comes apart). It then looks like an upside down safety valve with the spring being retained on the shaft by crimping the shaft. Only a steam test will prove if it is working OK. In use these whistles are fairly useless so get removed. My operating shafts stick up about 4.5mm above the body of the whistle.

Intrigued by what looks like a repaired hole on the bottom of your boiler.



Mamod sent out display models to retailers and to prevent them from being sold as a working model Mamod drilled a hole in the boiler, which on the locomotives would have been in that location. I have an SL3 which had a hole drilled there and I've seen photos of an SL1 which was on eBay recently which also had a hole in the same place.

Chris Cairns.

[WWLR]

Many thanks for the tip off about the chimney. It looks like I will need to carefully reshape the bottom of the chimney where the square punch has been used to get the saddle ring off as it's still a tight fit.

I'll strip the black paint off the wheels and look at rebuilding them with the Loctite 603 – expensive stuff but it sounds like it does the job and I shouldn't need to use that much.

The whistle is not a high priority as long as it doesn't leak.

The shiny patch on the bottom of the boiler is just that, a clean bit of boiler, no repairs or mystery holes. I'm more concerned about the lack of solder around the steam pipe connection, the pipe feels well fixed and is concentric with the dome fixing. I need to cobble together a connection to my test pressure gauge and find out if the boiler is sound or not.

Regards

Will

[Narrow Minded]

As far as the whistle is concerned, as much as it "spoils" the original spec of the loco I'd recommend swapping it for a filler valve.
As soon as you swap from solid fuel tablets to meths or gas, you have a fuel supply with the opportunity to outlast the boiler capacity - potentially fatal for a soft soldered boiler.

Most folk replace the whistle with the safety valve, inserting a filler valve in place of the original safety, then as well as protection for the boiler, you can enjoy longer running times too

Good luck for the pressure test - we await the results!

[Chris Cairns]

Loctite 603 - Note that some traders on ebay are charging the same price for 10mls that other traders are offering 50mls for. But it is the most suitable Loctite.

Not sure how the saddle ring is held on to the bottom of the chimney (possibly glued but do not heat it up too much as Mazak has a very low melting point) but it is a bigger ring than the straight chimney one so that the bottom of the brass spark arrestor fits into the ring.

The joint at the bottom of the boiler is a known weakness. I had a rather arrogant moderator on another Forum telling me that as long as you had water in the boiler that joint would never leak, but he was totally wrong (it is right above the middle burner on a 3 wick meths burner, and similarly affected by a gas burner). I have had several boilers leak at that joint including a new MSS Saddle Tank loco. I would recommend roughening up the boiler surface around that tube fitting then using a plumbers silver bearing lead free solder (has a higher melting point than other soft solders) to strengthen the joint. As it has already been assembled using soft solder paste apparently you cannot silver solder it.




© Peter Longfils



You will need to trim up the solder as it will foul the combustion chamber when you try to fit it back in (there is only a small cut out on the bottom front of the combustion chamber for that tube).

to meths or gas, you have a fuel supply with the opportunity to outlast the boiler capacity

The original meths burners had their capacity designed so they would run out before the boiler water level got too low (on a well running loco). However many users fill them up again having raised steam thus overriding that design feature, and of course meths burners like the Gremlin one have a much larger capacity. I agree that most ceramic gas burners have too big a capacity gas tank, although the Merlin gas burner was originally designed to run out before the water. But that was using Butane gas, does that capacity change if you use a Propane/Butane mix for cold weather?

Chris Cairns.

[laurence703]

Hi! Just come across this thread... I too have been restoring a SL3 recently albeit mine was a lot easier to sort out...

Anyway's here's a photo! "Cos we like pics we do"



Hope the restoration goes well for you!

[Lner fan Sam]

Nice job you done there laurance. I see that ofario got a new boiler there.

[WWLR]

Hi Laurance,

Thanks for the words of encouragement, your SL3 looks a smart loco.


Here is a close-up of the boiler bottom steam pipe connection – not a lot of solder showing here, but only a pressure test will show if there's a problem.




Following on from Chris's comments about the chimney, with a bit of careful levering I managed to separate the component parts.



The smokebox has finished its visit to the paint stripper. I'm quite impressed with the detail in the die casting with the neat rows of rivets on the door hinges. I prefer this design to some of the later ones.
It will be interesting to see how well the satin black BBQ paint takes to the metal.



Has anyone found an improved method of fixing the chimney to the smoke box? Some sort of threaded tube with a nut inside the smokebox might make for easier maintenance and future modifications.

Regards

Will

[Chris Cairns]

not a lot of solder showing here

That is exactly how the boilers come out from the Mamod SL & MSS locomotives. The theory is bubbles/beads of solder visible around that joint indicates the boiler has been run dry (a common problem with used Mamod boilers). A lot of people are under the impression that these boiler fittings were/are soldered in using a gas torch, but they were/are actually brushed with solder paste then passed through a furnace (watch this video from 1:08 http://youtu.be/V9c83qO08HM - I've read elsewhere on-line that on some later stationary boilers these fittings are just press fitted). So this solder paste method is why many of the inserts work loose (particularly the steam dome threaded insert). I would still recommend soldering up that joint as my previous examples, particularly if you intend using a meths or gas burner.

It will be interesting to see how well the satin black BBQ paint takes to the metal.

Remember this.




Well 2 coats of U-Pol Etch primer followed by 2 coats of Plastikote BBQ paint produced this.



However I'm having problems getting the aluminium cap to fit onto the brass spark arrester body, and I do not have the bottom ring (the original Dream Steam was going to get me one but I never chased that up).

Your smoke box is the earlier version (no bulbous boxes on the side for the side tank tab fittings) which were the best castings. They got worse towards the end of the original Mamod railway production, and the current MSS ones suffer from poor casting/Mazak composition as well.

Your suggested method of holding the chimney on is what Roundhouse do with at least the Millie chimney but that is not made from Mazak (threads on Mazak do not hold up well - the Mamod cab handrails in 5 BA, and the smoke box & rear drag beam chassis frame securing holes in 6BA).

Your restoration is coming on very well.

Chris Cairns.

[Lner fan Sam]

I love watching restoration projects on this forum. I would say that the purple paint on the cab is just a under coat for the repaint that your loco has had.

[Spule 4]

Your smoke box is the earlier version (no bulbous boxes on the side for the side tank tab fittings) which were the best castings. They got worse towards the end of the original Mamod railway production, and the current MSS ones suffer from poor casting/Mazak composition as well.

And the old ones seem to hold paint better than the newer ones from my two locos!

[dougrail]

I just use stove paint on a smokebox, bit thin but well wearing.

[Spule 4]

Dichloromethane did not take the original Mamod SL3 paint off the smokebox, but did off of the SLK1 very quickly.

Both were repainted with high temp BBQ flat black rattle can spray.

On the SL3 smokebox it is doing well, it is coming off the edges on the SLK1 however.

[Chris Cairns]

it is coming off the edges on the SL1K however.

Which is what has happened to my repainted smoke box above.

Chris Cairns.

[WWLR]

Didn't have much time to work on the project over the weekend (DIY and decorating time) but with a bit of a rearrange in the garage I have liberated the lathe from the surrounding clutter and had a go at making up an adaptor to attach the pressure gauge for testing the boiler.

I found a short length of 7/16” hex brass in the odds and ends box and turned down about 8mm of one end and threaded it 1/4” BSF to use in either of the small top connections. Going well, I thought, until I tried it in the front boiler connection, it had gone in about a turn and the ferrule detached itself from the boiler! I now have a half finished adapter spinning round in the top of the boiler.
Don't you just love it when a project is coming together – not!

Possible options:

1) Throw it down the garden and order a new boiler from DS. - a bit over dramatic and defeatist!

2) Try re-soldering the ferrule with the adaptor stuck in it. - possible

3) Try to super glue the ferrule in place in order to unscrew the adapter and then remove, clean up, and re-solder the ferrule – don't know how well super glue takes to solder.

Any ideas anyone?

[Narrow Minded]

Possibly "tack solder" the ferrule to remove the adaptor rather than super glue?