Steam lubrication question

[cessna]

I am building the steam donkey by Wm Harris, the plans do not show any lube system, I am enclosing a picture of pipes, would a displacement lubricator work where I have indicated? The cyls are 1" bore and 1" stroke.
Thanks
Terry

 

[cessna]

Here is missing attachment on previous post.

 

[tel]

Displacement lubricators are such simple things to make that I think in that situation I'd put two on it - as close as possible to the cylinders.

 

[cessna]

Thanks for the reply tel, how big (tall) would you suggest, I am thinking if there is room I could attach directly to the cyls.
Thanks
Terry

 

[GWRdriver]

Terry,
How large are the cylinders? Any size lubricator body will do the job, it comes down to how long you would like to run between purgings (condensate) and oil fillings.

I would agree with TEL, and I would strongly suggest it (or they) be put in the steam supply line BEYOND the throttle or steam stop valve otherwise when cooling down steam oil can be drawn back into the boiler by the vacuum making for a gooky mess. I would also suggest two other things (but not strongly) . . . if you feel up to it I would make your lubricators with metering valves and drain valves. The metering valves so that oil flow can be adjsted (and it will invariably need adjusting) and drain valves to purge the condensate to avoid the bother of pumping it. The attached is a suggestion for a lubricator with both valves.

This is a generalized design which has a couple of details which I might do differently . . . I would design the drain valve to purge down through the plug rather than out the side of the body as shown, and I would also machine (drill?) a recess into the under-side of the filler cap. For reasons as yet adequately explained to me a hydrostatic lubricator needs a small amount of air over the oil in order to start and operate reliably.

 

[cessna]

Thanks GWRdriver, I will make a couple as per your suggestions, I think I can mount them so they are just before the cylinders. The cyls are the same as the ones for the #7 Stuart engine.
Terry

 

[Maryak]

A couple of thoughts about the location of displacement lubricators.

This type of lubricator relies on the condensation of steam to provide water to displace the lubricating oil into the parts to be lubricated.

In full size, for cylinder lubrication they are normally mounted somewhere on the steam chest, not in the supply line from the boiler. The general idea is to supply steam to the engine with a minimum of heat loss between it and the boiler. To introduce a condenser into the supply seems a somewhat contrary thing to do.

Just my opinion and probably worth what you paid for it.

Best Regards
Bob

 

[GWRdriver]

To introduce a condenser into the supply seems a somewhat contrary thing to do.

Bob,
This has been the preferred "simple" method of lubricating steam models, except as I explain below, for a very long time and when set up properly they do their job with no adverse effect on the steam quality or quantity. Granted one does see piping system illustrations for stationary models (Stuarts, etc) showing the lubricators attached directly to, or adjacent to, the steam chest but in overall numbers that's the exception rather than the rule. The standard method of lubrication for the entire sub ride-on gauge model railway locomotive hobby is via hydrostatic pot and the majority of those are located remotely, more or less, from the steam chests and cylinders.

Hydrostatic lubricators can be finicky and obstinant beasts, sometimes gulping oil, sometimes not delivering any at all, so for model locomotives in any of the passenger hauling gauges a mechanical lubricator (or two) is preferred so as to provide a more controlled oil flow. In these cases the oil supply line is connected to the steam supply (drypipe) just upstream of the steam chest or in later vintage locos directly to the steam chest via copper tube through a check valve. It has been determined (by repeated field experience) that when a single-ram mechnical lubricator is used and the oil is introduced into the drypipe (before the steam line is split or "Teed" to go to each steam chest) at single point the oil supply will always favor one cylinder over the other and one valve and cylinder may be starved of oil. For that reason most model locomotrive builders now use some combination of mechanical oil pump(s) which will provide a seperate ram and supply line to each cylinder. For stationary display models the hydrostatic remains the simplest and most preferred lubricator.

This is a full size "Roscoe" type hydrostatic lubricator which is little more than a pot with a metering valve and a stop valve. These were standard equipment on a very large percentage of Victorian era British locomotives and remained with most of them until the end of their working lives. The Roscoes were nearly always mounted on the side centerlines of the smokebox and fed through to the steam supply tubes after they split. This particular Roscoe is one of two on the South Eastern & Chatham Rwy Class D 4-4-0 in the British National Rwy Museum.

 

[Maryak]

Thanks Harry :bow:

Best Regards
Bob