Simple displacement lubricator

I wish to fit a lubricator to the steam pipe of a small oscillating engine, of the type found on some commercial engines. It will have a filler and a drain plug, but no regulation of the oil flow. How large a hole does it need from the oil tank to the steam pipe please? Probably smaller than I think! Thanks.

Maurice

From one drawing I found the hole was around 1mm, another had 0.6mm.

Thor

Edited By Thor on 30/12/2017 05:23:11

Maurice ... I have built many disp. lubricators over the years and now make the hole to be as small as possible ... I use a 20 thou. drill ( about 0. 5 mm) ... feed the drill in VERY, VERY slowly and carefully ... I try to fit the lubricator in the lathe chuck ... then use a small centre drill to make a small mark on the cross-tube ... use the tailstock for holding the drill ... be gentle.

martin R

I totally agree with Martin. The problem that I have found with displacement lubricators is that they tend to "gulp" all of the oil as soon as the engine is started so the smaller the hole the better. I find drilling these small holes on the kit that I have available is difficult and Martin gives excellent advice. However, if the engine does gulp the oil too quickly one trick is to insert a suitable piece of wire which is, say 0.25mm dia., into the lubricator outlet which will immediately reduce oil flow. Further experimentation may produce the desired result.

Mick

Thanks for the advice gents. I can now proceed with confidence. The forum comes to the rescue again.

Maurice

When I made one, I drilled the hole using a sewing machine needle ground as a D bit, this gave a tapered hole, and I stopped as soon as the point went through. Used a hand drill rather than a powered one.

Ian S C

Hi All

I am currently designing a small displacement lubricator for my jepson engine.

I have decided to go for the type which attaches directly to the side of the valve chest where the cross is in the photo.

I am using a the simple drawing from a K.N. Harris book as the basis for the design but do intend to add a needle valve to regulate the flow. K.N.H. recommends a No. 70 drill for the oil supply hole (0.028". The smallest drill I have is 1 mm. so I felt that adding a needle valve would be advisable.

It is easy to see how steam under pressure enters the lubricator however I am puzzled as to how the oil travels back into the valve chest. K.N.Harris has no idea either. Anyone got any thoughts?

My theory is that it is a dynamic system, not a static one.

Pressure causes steam to enter the lubricator.

The steam condenses and drops below the oil, allowing more steam to enter, until it raises the oil level level above the hole.

The constant pressure cycling means the oil and steam can gradually change places. If the pressure drops so oil drips out, then when it rises more steam goes in when the pressure rises and back to the start.

I would guess that the death of such an arrangement is if the hole is too long so the oil never gets 'sucked' out the end when the pressure is low or if it is placed too far from the valve chest in a location where the pressure doesn't cycle enough.

Neil

Its simply dissplacement - oil and brass body are cooler than the steam passing the opening so a little condenses, water being more dense than oil sinks to the bottom of the holder and in turn dissplaces the same volume of oil - only place for it to go is out the same hole the water came in from - its then moved by steam.

Hi Neil / Fizzy

Thank you for your replies.

Have to say I like your dynamic theory Neil, much the same as I was thinking.

Pressure building up in the lubricator exceeding the incoming pressure of the steam, hence the oil is drawn into the valve chest. I would imagine in some form of misty miasma. Just my thoughts.

Thanks again

Geoff

......and here it is designed and made, just hope it works ok. Body is 1/2 inch square and the needle has been salvaged from an aero carb

Geoff

Well it certainly looks the part, very nice.

Think bananoffee yoghurt!

Neil