LBSC displacement lubricator

[RRMBKParticipant @rrmbk]

I am building a 21/2 gauge single Cylinder loco from LBSC mid 1950’s. The drawing shows a displacement lubricator which appears to be a copper tube with a brass spigot connecting it to the valve chest. In the end of the spigot tube LBSC says to drill a no 70 hole and keep it pointing upright in the finished article. Has any one made one of these and if so does it work please?

 

Also how does it work? I can understand the steam entering under pressure, condensing and the water then raises the level of the oil, but surely the steam presure from the valve chest is constant and the pressure in the lubricator tube will be less because its cooler; so how does the oil get back down the tube and into the valve chest please?

 

Many thanks

 

Brian.

[RRMBKParticipant @rrmbk]

Do they work & if so how??

[TerrydParticipant @terryd72465]

Hi Brian,

 

These are quite simple and clever solutions to the problem of cylinder lubrication. Basically a steam pipe passes through an oil reservoir but above the oil level. there is a small hole cross drilled in this pipe (i.e. the no 70 mentioned in your post) This fills the lubricator with steam which condenses into water, sinks to the bottom of the reservoir and in turn raises the oil level until it rises to allow a drop of oil into the steam line. It is more or less a continuous process.

 

Pressure in the reservoir increases as the space is reduced, and it is a relatively small space, eventually oil is forced into the steam line.

 

There is a discussion in another thread, but you can find a discussion of how they work on this page – just scroll down. There are a couple of designs, – one made from stock nuts and bolts and tubing, – here and here.

 

Hope that helps,

 

Regards

 

Terry

Edited By Terryd on 06/12/2011 07:00:38

[michael howarth 1Participant @michaelhowarth1]

I am no expert on displacement lubricators other than as a sometimes dissatisfied user. In this I know I am not alone. They are successful if by success you mean getting oil to the cylinder. The “problem” with them is that they do tend to empty themselves of oil very quickly…. sometimes in a matter of minutes….it is not delicately metered out. There are a few things that you can do to mitigate this……make sure that the lubricator is in the “line” between regulator and cylinder…never before the regulator. Fit a needle valve to the lubricator to enable finer control or even to shut it off and open it at intervals. Use a good, thick, properly formulated “steam oil” ….never use motor oil.

[Les Jones 1Participant @lesjones1]

Hi ,

I’m sure my theories will be shown to be wrong by those with knowledge of displacement lubricators. I have never seen them before but I read a few recent threads on the subject. The only thing that I see that influences the amount of oil dispensed is the amount of water that is produced by condensing the steam. The amount of steam condensed will be influenced by the heat loss in the lubricator. So if the lubricator was in a warm location and lagged it would dispense less oil than if it was in a location where it was cooled by airflow etc. Also if the steam was superheated to any extent that would also reduce the amount of oil dispensed.

 

Les.

[RRMBKParticipant @rrmbk]

Thank you all for the shared knowledge and the interesting links. its been great reading them. However one thing is still eluding my simple brain. As the steam supply is at full boiler pressure, then the pressure in the lubricator oil reservoir will surely be less than boiler pressure due to heat losses and the losses due to the lubricator pipe restrictions. If so how can the oil ” Flow ” in the reverse direction down the lubricator feed tube aginst a higher pressure ?? is it perhaps something to do with the relative density & or viscosity of the oil in relation to the steam ? does the oil perhaps lie on the bottom of the tube and the steam pass over it in the opposite direction?

I am once again mystified by some of the wondrous dark arts conjoured up by steam!!!!

 

Brian K.

[Les Jones 1Participant @lesjones1]

Hi Brian,

As some of the steam condenses to water in the lubricator it will drop through the oil to the bottom (As water is denser than oil.) The oil displaced by the water will be forced into the steam flow.

 

Les.

[RRMBKParticipant @rrmbk]

Hi Les. If the lubricator were in the steam pipe and before going to the valve chest, so there is a flow of steam that would pick the oil up and carry it onward with it, then I could understand your suggestion, but in this design the only pipe into the lubricator is the steam supply and this comes directly off the front of the valve chest. there does not appear to be any route back out of the displacement chamber for either the steam, or the oil.

 

Brian

[Les Jones 1Participant @lesjones1]

Hi Brian,

I was looking at the second link that Terryd put in his post. Looking at the first link I can see your reasoning. To try and understand the discrepancy I Googled “displacement lubricator”. It would appear that the one in the first link is used mounted right on the side arm a T piece in the steam flow.

Like this

 

Les.

[michael howarth 1Participant @michaelhowarth1]

Les ….the type of lubricator mounted on a side arm is known as a Roscoe dead leg lubricator…..named after James Roscoe who invented it in 1862. I must say that I have had more success with this type than the in-line arrangement which seems to gulp the oil down in minutes. In the Roscoe the steam/water mix can form a thick creamy emulsion which can last some time before being totally diluted and displaced by water. As the type of model using this type of lubrication is usually of the small low pressure type, the small amount of oil in the emulsion getting to the cylinder is enough. How the oily mix backtracks along the steam pipe into the valve chest is indeed a mystery and probably best explained by reference to Brian’s wondrous dark arts.

 

As to keeping the lubricator warm….I have heard it argued that the hotter the oil gets the more freely it will flow as its viscosity decreases…..so best to keep it cool(?). Seems to me that it is always going to be pretty warm with steam going in and out.

 

I usually use 460 grade steam oil in my models which are up to 1 inch/ft scale but I think I shall buy some 1000 grade at the next show I attend and see how the thicker stuff performs.

[Sub MandrelParticipant @submandrel]

I made a basic displacement lube for my stuart 10 and it works fine.

 

Neil

[Brian JohnParticipant @brianjohn93961]

1. How much oil do you put in a displacement lubricator ? Should the oil level be just below the steam pipe with the small hole in it ?

2. What if you overfill it and it is over the pipe…will this matter ?

3. Does any oil get through to the piston/cylinder at all when you are running on air ?

[michael howarth 1Participant @michaelhowarth1]

It has always baffled me as to how steam can travel one way in a tube and oil can travel the other way in the same pipe. I have come to the conclusion that it must work by magic.

Brian….I think that the answer to your questions 1 and 2 are, going on my experience, that if the lubricator is overfilled it will quickly find its way out to the exhaust and make a sticky, oily mess. I don't think any damage will be caused.

Your question 3 I find quite interesting. The Roscoe lubricator apparently works on the condensing steam forcing out a drop of oil. Quite clearly then, running on air will not give the same effect. However, when my last loco was ready for an air test….and having experienced seizure of the Viton piston rings due to lack of lubrication when running on air in a previous model…..I made up a Roscoe and connected it "in-line" in the air line on "I've got nothing to lose trying it" principle ……and switched on the compressor. To my amazement there was soon a ring of cylinder oil at the chimney ring indicating that oil was being fed from the lubricator. Now how does that work?

Mick

[Neil WyattModerator @neilwyatt]

> It has always baffled me as to how steam can travel one way in a tube and oil can travel the other way in the same pipe. I have come to the conclusion that it must work by magic.

It's a dynamic system, not a static one. My guess is that as the engine works the steam pressure pulses in rhythm with the valves opening and closing. pressure peaks can force a little more steam into the lubricator, the troughs allow tiny amounts of oil out.

Neil

[michael howarth 1Participant @michaelhowarth1]

Neill….would the pulsing effect perhaps explain how/why the Roscoe works on air as well as steam?

Mick

[Neil WyattModerator @neilwyatt]

Sorry Mick,

I don't know those units,

Neil

[JC Uknz 1Participant @jcuknz1]

I have three displacement lubricators in my locomotives and in all the steam passes through the lubricator and some condenses in the lubricator to raise the oil level which mixes withmore steam and is thereby carried to the cylinder.

I assume the drawing that you [OP] are looking at is not a full drawing though I learnt much of what I know by reading most of the LBSC articles in ME thanks to a Club library. I have never seen a drawing that inferred the steam went into the lub and came out with some oil. The lub is in the path of the steam between boiler/regulastor and cylinder.. The earlier linkied photo show them with an in-pipe and an out-pipe and filling screw at top. ZThe better versions have a draw cock [ just a screw with centre drilled out to sideways pipe which opens as screw in withdrawn. Ideally this is placed to the side of the loco cab so it drains the water off the loco….. sadly my Accucraft locos do not have this drain and one has to use a syringe to extract the water. My Roundhouse 'bertie' is better designed in this respect and drains clear of the track.

Early on in my clumbsiness I over filled one lub but I didn't notice any problems … obviously not desirable ..

 

EDIT with the small No.70 hole only a small amoun of steam escapes the delivery pipe to force the oil up and into the steam supply … most is traveklling straight through along the pipe.   I did think afterwards I remember seeing various drawing where there is a mechanical lubricator which is obviously better but also more work involved. I assume LBSC didn't think it neccessary for the 3.5" loco you are building.

Edited By JC Uknz 1 on 26/10/2014 06:40:06

Edited By JC Uknz 1 on 26/10/2014 06:48:20

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