The Unofficial Mamod and Other Steam Forum

CCairns · Posted: Thu Nov 01, 2007 7:04 pm Post subject: Mamod/MSS Loco Sight Glass

Well it has finally happened - I've melted my first Sight Glass (actually it is plastic).

I've been running my MSS Saddle Tank ( http://modelsteam.myfreeforum.org/about4686.html ) using my meths burner, but as I've posted elsewhere this is still suffering from severe priming when starting this loco which results in the water level being at the minimum level at the end of a run. By comparision my Mamod locos when using this burner will have at least 1/3rd (between Min and Max) of the boiler water level remaining at the end of a run.

The sight 'glass' on this loco has a different reflector behind it, it is actually a piece of circular metal sheet which has had 2 wings bent on the ends and 3 holes drilled in a line in the middle, and is a friction fit between the threaded inserts for the screw on Water Level brass plate. This metal is very dull compared to the shiny reflector as fitted to the Mamods (and no longer available as a spare that I can see online), and I had been using some food dye to colour the water, but stopped using this in the MSS loco as it makes a right mess of my kitchen if not cleaned up right away due to this priming problem, which I now believe is a design fault with the smaller steam dome and shortened steam pipe.

Most of the available Loco sight 'glass' spares actually use a very thin 'O' ring which is pretty useless at making a steam and water tight seal, and this has been covered elsewhere on this forum by recommending the use of silicone sealant. I've been getting the little packs of Mamod washers (ebay item 220141148307 currently the cheapest online) which include the thicker 'glass' as fitted to the stationary engines (which can be shaped to fit the loco) and a much thicker oval washer which makes a much better seal on the locos.

I know that you can use proper glass, like microscope slides, but I look upon these plastic sight glass's as a second safety valve, so that they will break well before the boiler would break should the safety valve stick for any reason.

Chris Cairns.

Graham-Jilly · Posted: Thu Nov 01, 2007 10:13 pm Post subject:

thats a shame Chris seems to be a definate design fault with that loco
hope you can get it sorted
regards Graham

ps did you receive the paypal payment

regards Graham
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Mamodman123 · Posted: Thu Nov 01, 2007 10:39 pm Post subject:

Hmmm is a shame really.. maybe you need to make a bigger steam pipe for the loco? One of my mamod locos has an MSS steam dome and doesn't suffer from any priming..

I would definately use silicone to seal the sightglass if its too much trouble.. although should be eaier if it screws on!
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Rob · Posted: Thu Nov 01, 2007 10:45 pm Post subject:

i think chasteam or pps have the reflectors for sale, the brass piece that fits over the end of the boiler in the cab to hold the sight glass in, is'nt it?
rob
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Rob

CCairns · Posted: Thu Nov 01, 2007 11:15 pm Post subject: Mamod/MSS Loco Sight Glass

MM - As I've shown in my other posting the steam dome that is provided with the Saddle Tank loco is much smaller than the standard Steam Dome. I have wondered whether a few more mm's of steam pipe in this small dome may be the answer, but the solder that MSS used is like arc welding and refuses to melt with my blow torch at present. I plan to remove this and try a standard size Steam Dome and steam pipe to see if this cures the problem first, then de-rivet the boiler from the smokebox assembly and fit one of my Mamod boilers instead, at least until I can get that blanked off aperture sorted out to fit a water top-up valve.

I have fitted one of these oval shaped washers and it is nice and steam/water tight. Problem with the MSS screw on backplate is they use very short screws which would make the fitting of the thicker stationary sight 'glass' require some longer 6BA screws.

rob-dd - The reflector is a small strip of shiny metal which is placed in the water level hole at the back of the boiler, prior to fitting the 'O' ring or washer, sight 'glass' and then screwing or rivetting the brass backplate to the boiler. The reflector is there to allow you to see the level easier but many owners leave them out after replacing the sight 'glass'. PPS, IP Engineering nor Chasteam list these reflectors on their website, although Chas is good about getting odd spares.

Chris Cairns.

Mamodman123 · Posted: Thu Nov 01, 2007 11:20 pm Post subject:

Yes thought it was! Is it priming from the start off or when the water is moving around in the boiler? Is the steam take from the centre of the boiler? I bet its the extra few mm's that you need! The steam dome is there for a reason of course

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CCairns · Posted: Thu Nov 01, 2007 11:40 pm Post subject:

Yes the steam pipe is in the same location as the standard boiler (this is a standard boiler with the rear aperture blanked off - see 4th photo in this posting http://modelsteam.myfreeforum.org/about4725.html ).

After raising pressure on starting the loco one is presented with a spectacular fountain of water which consumes nearly 1/3rd of the water level, and this is the same no matter what the starting water level is (I've tried it down to half full to start with).

I had a similar problem with an SL1, although that has the upgraded 'O' rings fitted as well, and found by removing the steam pipe and making the bend at the bottom of the boiler more at right angles this kept it up high enough within the steam dome and reduced the amount of water being pushed through on start-up. I prefer to stick to the Mamod method of 'O' ring, washer & spring to keep this pipe steam tight and not soldering it up, as it makes dismantling easier.

Unfortunately the only piece of scrap 1/8 pipe I have at present was used with an IP Lubricator, and thus not long enough to reach the regulator/reverser, hence my thoughts on trying to fit the standard Steam Dome and steam pipe.

Will need to wait as I am off to Inverness for a few days contract work.

Chris Cairns.