Rod glands

[John BramwellParticipant @johnbramwell55907]

[John BramwellParticipant @johnbramwell55907]

Please look at this photo of an engine out of my Archangel Snowdon Ranger whi h wont run. It just leaks the steam out the rods. There are threaded faucets so i think there should be glands there. Can you tell me where i can get some or what thread it might be? The outside diameter is about 4.85mm and it looks like 5 threads in 1/10" .

[Jeff DaymanParticipant @jeffdayman43397]

Need a pic that is in focus and preferably zoomed in on the end of cyl area to comment.

[Nigel Graham 2Participant @nigelgraham2]

As Jeff says, we really need a clear photo, but I think the gland nuts are still there.

If so – you are probably in luck. For this is basic steam-engine servicing, as the gland packing does wear with time, past the point that simply tightening the gland does nothing. (I suppose it breaks into very tiny fragments that emerge past the rod.)

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The two spigots should each have a gland-nut, often not hexagonal but cylindrical with small slots or holes for a C- or pin- spanner. On some engines the nut is shaped like a plumbing union-nut, on others it resembles a drilled-through set-screw.

You will probably have to make a C- or pin- spanner because these fittings are not usually standard items.

The packing on a small engine is typically either graphited yarn or an O-ring – available from model-engineering materials & parts stockists.

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Graphited yarn is thin string impregnated liberally with graphite grease. Cut a piece long enough for a few turns – see note below. Wind it round the rod so its outer end points clockwise round (so not facing into the gland-nut's rotation). Push the coil gently into the gland – use a brass, plastic or wooden tool to avoid scratching the rod – and screw the gland-nut up until the packing gently grips the rod.

An O-ring should be of a material that stands up to steam, hot water and oil of course (most do) but should also be a type that stands up to a sliding contact. Some are for rotating seals, others static.

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The yarn does not need the machinery dismantling beyond slipping the nut back along the rod and clearing out fragments of worn packing.

An O-ring would naturally need the rod disconnecting from its cross-head or guide; but cutting the O-rings like a piston-ring would avoid that disconnection – I've not tried it. If so, use at least 2 with the gaps well out of line with each other. (Like the piston-rings in a car engine.). O-rings are made in a huge range of metric and inch sizes so finding a suitable size should be possible.

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Note – In both cases the packing should be long enough for the nut to compress it. If too long you can trim the yarn back with a small pair of sharp scissors. It can be awkward stuff to cut, but for obvious reasons don't use a knife.

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As Jeff says, we need a better photo to confirm this, but it looks to me as if the gland nuts are there.

Otherwise – you'd have to make them! Brass or gun-metal, probably standard ME-series (32 or 40tpi) or perhaps Brass (all-26tpi), threads.

[John BramwellParticipant @johnbramwell55907]

You are correct, it is a knurled spigot with the glan in side. better photo to come. thanks.

[HopperParticipant @hopper]

Modern alternative to graphite string is teflon. Either purpose made packing in rolls like string, or take a length of plumber's PTFE thread tape and roll it up between your fingers to make a teflon string and wind it round the shaft and stuff it down into the gland then tighten the gland nut down on it.

[John BramwellParticipant @johnbramwell55907]

That sounds do-able. What about the stuff that looks like horse hair? Good for threaded maleable iron but might expand too much and impead the shaft.

[mechman48Participant @mechman48]

Posted by John Bramwell on 27/02/2021 09:43:56:

That sounds do-able. What about the stuff that looks like horse hair? Good for threaded maleable iron but might expand too much and impead the shaft.

Do you mean plumbers hemp; usually used in conjunction with ' Boss white' sealant, IIRC more for cast iron or galvanized fittings.

[HopperParticipant @hopper]

Teflon will work better than horsehairy stuff. Better seal and less friction.

[Nigel Graham 2Participant @nigelgraham2]

That was three weeks ago, -ish. Success?

Plumber's hemp, by the way, was for sealing pipe threads, not moving parts. It might work in a rod gland, but not reliably. It's probably now replaced in pipe-fitting by PTFE tape.

[John BramwellParticipant @johnbramwell55907]

well the glands dont leak but i think the problem is the valve and the piston is worn out. Also the loco has done some miles as the crank/big end and eccentric have play in them probably enough to effect the timing. Do you know anyone who offers an overhaul service? It appears to be well made so worth reconditioning.

[Nigel Graham 2Participant @nigelgraham2]

I see! Hmmm.

A slide-valve port-face ought really have a little gutter at each end so the valve edge over-hangs a trifle at full travel, so faces don't wear hollow, but they will still wear eventually.

If the piston is worn it's very possible the cylinder has worn with it, so will need re-boring.

A worn eccentric sheave and strap will affect the valve events, possibly more so than the worn connecting-rod bearings.

As for finding someone to overhaul it, I have never seen anyone advertise such services so really, unless you have the facilities yourself, you can only hope someone reasonably local to you will offer to do so for a donation.

Many model-engineers are reluctant to help in that way because we all struggle to find enough time for our own projects on top of ordinary domestic needs; but also because we all make mistakes and don't want to risk damaging someone else's one-off property.

However, your engine probably can be overhauled, so by all means try an appeal here.

[Howard LewisParticipant @howardlewis46836]

If you have the facilities, you will learn a lot in doing the work yourself.

The problem with refurbishing someone else's work is that the original work may be of a different standard from yours.

Bear in mind that a slide valve is held onto its face by steam pressure, so may appear to leak under low air pressure, but will be OK with steam under pressure. Steam will make the Piston and Rings expand and seal better than cold air, so things may not be as bad as you first fear.

A friend and I became involved in sorting out a newbie's Traction Engine. By the time that we had finished,it had acquired new: Piston, Rings, Piston Rod, Cylinder to Boiler studs, Slide Bars, and needed machining to the Main Bearings, Crankshaft, Front Wheel axles and all hub caps. What the builder had considered to be "good enough" was not "near enough" for any of the three of us!

You can never tell, until you start chewing, just how much you are biting off! Hence folk tend to be wary of sorting other's problems, especially where the provenance is unknown.

What was described as "A simple job" could turn out to be a major overhaul.

If you can, Do It Yourself, or at least become involved in the overhaul. It will be educational, interesting, and very satisfying.

Howard

[John BramwellParticipant @johnbramwell55907]

Thanks Howard and Nigel, that most encouraging. I do have an old Lorche and Schmidt lathe so i really should break the ice. Nothing to loose really as i woulc be ma!ing new parts not altering the old ones.

[Nigel Graham 2Participant @nigelgraham2]

A pleasure, John.

A tip for a new piston: it's common, good practice to turn it slightly over-size, then fit it to its rod and finish-turn the piston with the rod held between centres. If you are lucky, a new piston with new rings or packing, will be sufficient to restore the engine to working order without needing to re-bore the cylinder.

[John BramwellParticipant @johnbramwell55907]

Well, as Howard said" things may not be as bad as i feared". I connected an old fridge compressor to the bock when removed from the loco to see it better. It run nicely although there were serious leaks from the end of cylinder gasket and joiint between the vslve chest and block. The cylindrer end cover has one of it two screws sheared off. But there is spce to drill 2 more. Im optimisti now. Where do members buy 1/16" screws and a tap? .

[Nigel Graham 2Participant @nigelgraham2]

It would be better to replace the broken screw if at all possible. Is there enough protruding to grip it with pliers?

If so, soak the threads overnight in Plus-Gas (made as easing-fluid so better at it than WD-40) then gently warming the bronze may be enough to release its grip on the screws. This will depend rather on whether the screws are of brass or steel.

If brass it may be feasible to drill them out, with the block held rigidly on the machine. If possible, very carefully flatten the broken surface with a small file, without scraping the casting, to help the drill centre itself; but anyway start with a small centre or spotting-drill. If steel, it's still possible but even with a guide-bush, the drill is very likely to deflect into the softer bronze.

It's also possible to dissolve steel screws out of other metals, with a solution of alum; provided the alum won't attack the host metal. I had to do that recently, using advice from this very forum, to remove a fragment of tap I had managed to break inside a stainless-steel part! It is slow, but effective.

Hopefully you may be able to remove the broken fragment, then just carefully clean the thread with a second or bottoming tap.

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Where was the engine made? If in Britain, the screws are likely to be BA.

It will almost certainly be a standard size, and 1/16" dia over threads suggests 10BA (standard dia 0.067" ).

Alternatively, there is an ISO-Metric M1.6 (= 0.62" ), if the engine has metric fastenings.

Use some form of guide-bush for the tap, maybe the flange itself held by its other screw.

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Obtaining news screws and the taps should be easy enough, from the hobby's various suppliers, though you may need one source for the screws, another for the tools. My usual supplier of taps and dies is Tracy Tools, and I obtained the sizes above from one of their charts and a reference-book.

With any luck, replacing the blown gaskets and broken screw will cure the cylinder problems!

The screws will quite likely be available in sizes too long, but can be trimmed back. Wind a couple of steel nuts onto them first to hold them, and to clean up the cut end of the thread as you remove them.

[John BramwellParticipant @johnbramwell55907]

Yes! There was just enough tread protruding to turn it out. Then repaired cylinder end gasket and valve chest gasket and she ran with air from an old fridge compressor. But only when the air hose was connected to the cyclinder not the boiler. then I connected the boiler and fired it up with the spirits and it started to run but dithered backward and forwards. It seemed to have enought power but maybe steam was escaping past the piston or to both ports at the same time and then forcing it to go change direction. Is this common?.

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