sealant

As a beginner I have started to make a simple 0-6-0 live steam tank loco. I am lucky to have access to cnc machines for some parts. I am at a stage where I have made the bronze cylinder and covers, also the steam chest but can't find any information on what sealant to use between the covers or steam chest.. help ??

I'm no steam expert but have you tried the common stuff? silicon, epoxy or even ptfe tape if its a thread, i guess if you were silver soldering, a good bond would provide a kind of seal..

Michael W

More usual to use a gasket,  to place between the surfaces, your drawings should specify what to use.

Edited By KWIL on 01/02/2016 16:52:53

The machining allowances between "instant gasket" and paper based gaskets is different. Check your drawings to see what has been specified.

Thanks for your advise Michael but I'm none the wiser.. I would prefer advice from a steam expert and not have to spend time trying different products to find out. Also ptfe tape would not cover the area in one piece so I cant see how that could seal. .

I have two locos and used both systems. My first loco, a Maxitrak Ruby I have used Instant Gasket which available from Halfords, even Red Hermatite will do. This is also used to seal the steam chest and cover. My other loco has gasket paper on the cylinder covers but not on the steam chest. Gasket paper is available from Model Engineering suppliers like Blackgates or Polly, but you might get from an old fashion car spare shop if you have one.

Personally I go for Instant Gasket as it is much easier, just don't go mad when you apply it.

Regards

Luigi

I'm not a steam type, but from what I'v read the method used in days gone by was ordinary brown paper, soaked in oil. In my Stirling Engines I try for a metal to metal joint without any sealant. With hot air engines it's sometimes useful to thermally isolate the two parts, in that case a paper gasket is useful.

Ian S C

On full size engines we use graphite based sealant between mating parts. Seals well, heat resistant and comes apart when you dis-assemble. Comes as a paste in a linseed oil solution.

Paul.

I have always had superb results with Loctite 574 Flange Sealant on my steam locos. Virtually instant seal but easy to break the seal and clean up when necessary.

Mick

Good morning,

You don't say what size the locomotive it is to be but for the smaller scales, gauge 0 and gauge 1 its possible to get away with a metal to metal joint with a smear of jointing compound, I use a liquid jointing called Heldtite, clean both faces with a drop of meths then apply a very small amount of the jointing compound. A good alternative being the brown envelope with some jointing and some in the smaller scales are using PTFE sheet, but in both cases there is the task of punching out small holes for the bolts etc. Going up to the larger scales, ¾", 1", and 1½" then the use of a gasket paper together with a smear of jointing medium will suffice considering both the temperatures and pressures involved.

Regards,

Bob

I've used a non-setting sealant paste called 'Blue Hylomar' on 3 locomotives ranging from a 3 1/2 gauge Tich to a 5 inch gauge Jubilee 4-6-0 with both slide and piston valve cylinders in both bronze and iron and have never had a problem. Just clean the mating surfaces apply to both surfaces, allow to semi-dry for a couple of minutes then assemble the joint. No faffing about making paper gaskets and it's endorsed by Rolls Royce. Available from Halfords.

Richard.

I'm never impressed by Rolls Royce endorsements like this. I would expect RR surfaces to be flat enough not to need a sealant at all. A better bet would be 'endorsed by the bloke down the road who rescued a barn find and found the engine in the pond'.

If you do use Blue Hylomar, it is useful to know that you can dissolve it in acetone and then paint it on with a tiny paint brush.

Cheers, Tim

Thanks chaps for all your replies.. I forgot to mention it was for O guage. I will try the blue hylomar because it sounds easy to remove and don't want to use one that was stubborn and hard to remove as I would not want to scratch any surfaces..

Rob

I think that you will find that R - R invented Wellseal, and Hylomar in their Research Department, many years ago.

Wellseal was used to seal the wet liner to the recess at the top of the cylinder block on the C Range engines. Messy (and smelly) stuff as it seemed that only trichlorethylene would dissolve it, to clean hands or tools, or anything else. For many years trich has been banned, because of the effect of breathing in the vapour.

At Perkins, Hylomar was used extensively for many years. Both are non setting jointing compounds, unlike Hermetite, which will set like concrete, if not harder, and has to be virtually chipped off.

If the machined surface is reasonably flat, and has a good finish, applying a sealant, such as Wellseal, Hylomar, or silicone rubber results in a metal/metal joint, with the sealant merely acting as a gap filler where the surfaces depart from ABSOLUTELY flat. Again, you need something fairly exotic as a solvent ,such as methyl chloride, for Hylomar. Silicone rubber is good, but beware of excess being squeezed out to block small passageways, such as steam ports if used on cylinder covers.

There are grades of Loctite, and probably other anaerobic sealants, that will do the same job.

Howard

Slightly off topic; when I was involved with o/hauling turbines, pumps etc. in the UK & Middle East & many's the time it was stipulated that the joint line 'tween top & bottom half casings were stoned ( not in the sense you're thinking of ) & a very thin bead of blue Hylomar to be run along joint line prior to casings being impacted / hydraulically torqued together.

George.

For sealing the two halves of our Continental aero engines (opposed 4, 6 and 8 cylinder), we used Rolls Royce compound, it was painted on the flange surface, then a bit of #40 cotton thread is layed on the flange, and the two halves bolted up. I know, OT, but just another seal method.

A lot of joints are not that critical that it matters whether you use thin paper, or liquid gasket.

Ian S C

LBSC always used to recommend 1/64" Hallite gasket paper or a good bit of thick brown envelope paper soaked in oil!

I believe the normal suppliers like Reeves still sell Hallite gasket paper, but modern automotive engines today, like Honda for example, don't use any gaskets at all except on the cylinder head. Their bolting surfaces are metal to metal with a hint of RTV gasket goo. I like the cotton thread idea, reminds me of the days when plumbers used to use Boss White and hemp wool to make screwed pipe joints using galvanised iron fittings. And my good lady kindly brought some back from the UK last year she found in a B&Q shop, so it is still made but not available here

On the subject of Rolls-Royce aero engines.

The original Merlin engine had lapped metal to metal contact surfaces between the top of the cylinder liners and the cylinder heads. They were a constant source of trouble. During the war the British government asked for help from the USA to set up a shadow manufacturing factory and Packard reluctantly got involved. The first thing they did was review the design and pronounced it was a load of cr*p and set to to re-engineer it. The first thing was to install a copper sealing ring between the liner and heads and to improve the machining of all the parts. They couldn't believe any mechanical engineer would try such a stupid way of sealing the compression pressure.

Turns out while RR made 20 engines a day on a good day, and had endless problems in service, that Packard at the end of the war were turning out 20 per hour by using automotive tooling and machining techniques, and holding much tighter tolerances.

NEVER EVER use Blue Hylomar as a sealant on any petrol line which has small orifices along the line.

Like , for instance , a carburettor with idle jets, etc.

Unless you like stripping carburettors down on the side of the road..