Garden Railway Forum

Not sure how long I've had this SL3, but as it is currently the workshop test bed I felt it needed a boiler flush out and clean up.

It was listed on eBay for spares or repairs. I originally intended buying it for spares but there was something strange about the boiler so I asked the seller for more photos. Of course that increased the interest for this loco so I got it at a much higher price than I'd anticipated.


A riveted boiler back plate.

It was an early SL3 (key ring type coupling ring and no bulge on the smoke-box sides for the tank tabs), but was missing the wheels & coupling rods plus fixings, chassis spacer, screws and nuts holding cab sides to chassis frames, safety valve (a bolt with thick washer was fitted instead), rear drag beam including buffer beam plate, buffers & coupling ring, and had another screw loosely screwed into a hole on the bottom of the boiler.


After the fitting of wheels, rear drag beam, a safety valve and a water top up valve which replaced the removed whistle.

I've seen these crude screws fitted to the bottom of other Mamod boilers but never really found out why that was done. I guess it was some form of boiler drain plug in the days before syringes were readily available to the general public. So I soldered a 6BA screw into the hole using plumbers solder which does not melt in the flames of a meths burner. The whistle insert was leaking and I tried to repair it using a solder tip on my gas torch but that did not get hot enough to melt the solder paste so I had to use the hot flame adapter. Despite using wet towels I still managed to damage the paint on the front of the cab with a combination of this hot flame plus trying to get the whistle out in the first place. This process still did not fix the boiler insert completely so I had no option but to de-rivet the boiler back plate and smoke-box in order to remove the boiler for a full repair. I re-soldered the 2 boiler top inserts (the steam dome insert had been re-soldered by the previous owner and sits somewhat higher than normal).



Having de-riveted the boiler back plate I soldered in 2 x 6BA screws so I can fit the back plate using washers & nuts. The sight glass recently started to crack so on removing I found that the cut-out in the back plate had a rough edge where the crack had started so I smoothed that rough edge out and fitted a new sight glass.

This loco also lost its reverser valve when I was trying to get an SL1K ready for re-sale ( http://gardenrails.myfreeforum.org/about423.html ). So as I was going to fit a refurbished reverser valve I decided to de-rivet the cylinders as well, fit new gaskets, hone the cylinders and refit. On checking the alignment of the steam holes I found one cylinder had the front steam/exhaust hole in the wrong place but fortunately the cylinder end caps are the thick variety so I managed to fit the front end cap where it sticks out a bit but is steam tight and does not block the misaligned steam/exhaust hole.



I like the brass balloon chimneys and decided to fit a silicone tube to the exhaust (bending the short straight pipe to shape).



This loco has always started off with priming and runs with a wetter than normal exhaust. This may be due to either the raised steam dome insert, or the condition of the boiler inside. I've just soaked the boiler in vinegar for 2 days which seems to have cleaned up inside a little but I forgot to put the exhaust pipe in the back of the reverser block when I re-assembled the loco so it has just run with no proper exhaust pipe. Need to wait for it to cool, refit the exhaust pipe and then compare how that priming has progressed.


Refurbished boiler.


Screw soldered in to plug the drain hole.

The loco is missing a couple of items so I will put up a Wanted request for these shortly.



Chris Cairns.

Interesting Chris.

My SL3 dated from just after this one (oval coupler rings) but had the smooth firebox, but screw on backplate and screw on cylinders.

I am thinking that Mamods are like the cars built by American Motors Corporation (AMC, our closest thing to B-L) near their downfall in the car business, no two were built the same or used the same parts!

Glad it was saved. I still have the stack parts from mine, maybe for another locomotive someday.

Unlike other Mamod products the chronology of the Railway System is surprising hard to catalogue considering they were produced by 4 different owners for a total of only 10 years.

Coupling Rings - Original key ring type introduced by Malins (Mamod) Limited in 1980. Oval type probably introduced around time of SL1K in 1983 by Mamod Limited (Ascot).

Boiler back plates - Again originally riveted back plates introduced from 1980. Screw back plates introduced with the SL1K kit in 1983.

Cylinder Back Plates - Again originally riveted cylinder back plates introduced from 1980. Change to screw & nut fitted unknown (probably 1983 as above).

Smoke Box Sides - Again originally smooth sided introduced from 1980. Original SL1K kits were also smooth sided so I suspect change to bulge sides came with last Mamod owner, Jedmond (Engineers) Limited of Slough, with their production resuming in June 1985 until production of the Railway System ended in 1989.

Chris Cairns.

Courtesy of Greg (Narrow Minded) this loco now has a complete set of buffers, and an order with RWM Steam will cover the last 2 items missing.

Keeping up with the test bed use for this loco once I get access to a large vice or similar for bending I will be trialing out the short cab back that Peter Jones was kind enough to send me.

I managed to get the exhaust pipe fitted back into the reverser block and there is no real change in the initial priming with this loco or wet exhaust. So I guess a longer steam pipe up into the steam dome nut is probably the solution.

Chris Cairns.

So after getting an SL3 cab back & MSS coupling rings from RWM Steam this loco is now once again complete.



Although it will remain my workshop test bed it has gone into temporary storage so that I can clear some more of my many workshop projects.

Chris Cairns.

Well done! I still have the body and chimney bits from my SL3, maybe someday I will do something with them?

After another Mamod SL1 turned up on eBay with a hole in the bottom of the boiler there is a working theory for these holes.

Apparently Mamod sent out model steam engines to dealers for free to be used as display models. To ensure these models were not sold by the dealers a 1/8" hole was drilled in the bottom of their boilers. These holes have been seen on some locomotives, traction engines and steam wagons.

Chris Cairns.