Mamod/Meccano MEC1

This engine was a collaboration between the two companies, and it made perfect sense. A Mamod engine designed to work with the Meccano system, the best of both worlds I'd say.

Mine came from eBay, sold 'for restoration/parts'. I like these engines and I wanted a project so I put in a low bid, and won;

It was missing a safety valve (I have a spare), water level plug (ordered from eBay) and a burner (the one from my SE2a fits). Overall it looked pretty good;

But the steam pipe had come adrift from the cylinder back plate;

And the steam dome was bent over to one side;

The steam pipe was an easy fix, soft solder and a small jewellers/cooks blowtorch sorted that one out;

I removed the cylinder and blanked off the steam pipe with a piece of scrap aluminium then did a hydraulic test;

Which failed. There was water leaking from somewhere on the top of the boiler around the dome area. So, I drilled out the rivets that attached the chrome cowl to the firebox and had a closer look, fitting a new fibre washer to the dome. A second hydraulic test showed up the problem, the boiler was cracked around the dome where it had been dropped in the past. The cracks (there are two) can just be seen below;

This means that the boiler is, as far as I'm concerned, scrap. So, I removed the end plate (there's only one, the rest of the boiler is made in one piece) and steam pipe to see what's what;

So, I now need a plan. I have a few ideas running around my head, which I'll share when the time is right. If nothing else I can break the engine for parts and get my money back, and more.

I took a risk buying this, and I like a project, so I'm not too disappointed.

Paul.

Mamod TWK1 whistle repair

The whistle on my TWK1 leaked steam, badly. On stripping it down I noticed that the spring sitting up on the crimped end of the inner shaft, extending the spring and therefore losing some of its compression and weakening the seal. The solution was to fit a 1.5mm C clip on the shaft, helping to compress the spring and making sure that it sat properly on the shaft;

I also fitted a new O ring to the whistle, 2mm i/d x 1.5mm cross section.

Now the whistle no longer leaks and the engine steams quite happily.

I've also fitted a new aftermarket scuttle;

Job done. Now I can think about paint.

Paul.

Mamod SE2a whistle repair

The whistle on my SE2a was passing steam. I originally tried to fix this with a small O ring, but today I decided to have another look. This is an early version of the lever type whistle, using a taper on the bottom of the inner shaft to make the seal rather than the O ring found on later whistles;

I stripped it down by holding the upper section of the body in a vice, mine has soft jaws, and turning the lower part with a spanner on the hex. This was after a 48 hour soaking in Plus Gas. Both body parts are held together with a light interference fit.

This is the lower tapered section, which makes the seal;

I put a few drops of Brasso on the taper and turned the inner shaft inside the lower body a few times until there was a witness mark all the way around the shaft;

Re-assembly is just a matter of pressing the two parts together, not forgetting the separate plunger which acts on the top of the inner shaft (I did!).

Of course I had to test the whistle by steaming the engine, and there is an improvement although there is still a slight leak. But I can live with that.

Here it is driving a Wilesco piller drill;

A nice simple job for a tired Friday afternoon.

Paul.

Leaky Mamod cylinder

The cylinder assembly of my TWK1 leaked steam. I knew about the problem before I bought the engine as it was mentioned in the eBay description. 

The first job was to remove the cylinder from the engine and take a good look at the mating surfaces. Here's the back of the cylinder;

I then 'blue'd' the mating surfaces with a marker pen, re-fitted the cylinder and then gave the flywheel a few turns before removing the cylinder. Looking at where the pen marks had been rubbed away gave me an idea of how well the cylinder and bracket mated together;

Note how the pen marks revealed where the steam was escaping, they should be completely rubbed away around the steam holes. I took the problem to a Mamod Facebook group (Facebook has its uses!) and I was advised that the bracket might be bent. So, armed with a pair of pliers, I gently bent the bracket, a bit at a time, until the wear marks looked like this;

I then removed the bracket from the engine, made easy by the fact that this is a kit built example so the bracket is screwed rather than riveted in place and the steam pipe isn't soldered to the boiler but is held in by a screw fitting and seal;

Note the threaded inserts in the firebox top. I've also given the pipework a wee polish.

I then lapped the two mating surfaces following the method detailed here, although I used 600 grit wet & dry rather than 400 as I didn't have any;

Success! The engine now runs without any leaks between the two faces, although there is some leakage from the cylinder bore itself. I may yet try turning up a new piston.

Here's a close up of the boiler pipework; 

The union where the steam pipe joins the boiler relies on a seal, I've used a 3mm i/d x 1.5mm cross section O ring.

I'm quite pleased with this job, and it will be good practice for when I re-assemble by Mamod loco. The next job will be to sort out the leaking whistle and then strip the engine down for a repaint.

Paul.