Mechanical Lubricator Question

[rodders]

Raw recruit! Studying this thread with pecuniary interest.
I am at a slightly less advanced stage with my B5 lubricator. Having difficulty grasping the principle of input and output on the base of the stand as detailed in runner42`S drawing above. LBSC always expects that his readers already knows what they are talking about??.
Have assumed, rightly or wrongly that the two ports (1/8" apart & 1/8" up from the base & drilled No. 55)are alternately covered and exposed by the oscillating pump cylinder. The output port to the ball valve is clear.
Is it the case then that the upward suction stroke draws oil from the sump through the other port.
Probably obvious "when you know" but I have never seen one in operation and would be grateful if anyone could take a moment to explain/confirm my supposition.

[GWR 101]

HELP now I am confused, I have three locomotives at various stages of construction or planned, none have yet reached this stage. Juliet 2, Jubilee, and Firefly all three have mechanical lubricators, I may not use this type of (lubricator on Firefly) all the drawings show "oil check valves" on both the lubricator and on the steam Tees. In order to speed up completion I have purchased an un-machined casting of the stem tee for J2 and this contains a portion for the inclusion of an " oil check valve". Having just completed the motion this together with the Exhaust Tee is my next task. Sorry to steal your thread Brian, but thought this may be of help to you too. Incidentally the spring size on the lubricator on Jubilee is shown as 1/8" od x 28 Gauge with a 5/32 ball. Paul

[Deleted]

Hello Brian------------you might also consider fitting a stop valve between the check valve and the point of delivery...In the unlikely event that your check valve decides to stick open (with the resulting display as if you've just struck oil in the desert).. you can isolate, repair and be back in service again....PS..I'd place the delivery point into the main steam supply pipe in the smokebox rather than on top of the steam chest....This will give the steam and oil plenty of chance to mix before being used... (Worked for me very well---5"g Royal Scot)

Attachments:

[jma1009]

hi rodders,

it is unfortunate that the drawing in LBSC's Shop Shed and Road/The Live Steam book isnt as clear as it could be. the No.55 drill shown vertically from the base of the pump up to the 1/8" you refer to is on the LEFT hand side not a drill hole at all but a vertical slot which you rightly deduce sucks the oil up from the tank. the hole on the right is the feed from the cylinder to the pump body into the cavity where the bottom check valve fitting screws.

hi paul,

martin evans always showed 2 check valves -completely unnecessary in my opinion.

cheers,
julian

[JDEng]

When we're talking in terms of two check valves; where? Both on the lubricator or one on the lubricator and one at the point of delivery into the cylinder/steam-pipe?

I would accept that two are not necessary on the lubricator but would contest that it is necessary to have one at the point of delivery as well as one on the lubricator immediately after the pump. The one at the point of delivery keeps the oil line full whilst the loco is standing and means the oil feed is established as soon as the loco starts to move; the one on the pump prevents the pump sucking the oil back out of the oil line instead of out of the reservoir.

John.

[rodders]

Julian - Thanks for info. I have drawn the whole thing up 3D to observe the motion. All clear now.

[sncf141r]

Dec 19, 2013 16:33:59 GMT JDEng said:

When we're talking in terms of two check valves; where? Both on the lubricator or one on the lubricator and one at the point of delivery into the cylinder/steam-pipe?

I would accept that two are not necessary on the lubricator but would contest that it is necessary to have one at the point of delivery as well as one on the lubricator immediately after the pump. The one at the point of delivery keeps the oil line full whilst the loco is standing and means the oil feed is established as soon as the loco starts to move; the one on the pump prevents the pump sucking the oil back out of the oil line instead of out of the reservoir.

John.

I agree with Julian on this one - only 1 check valve.

If you think oil will somehow be "sucked" out of the oil line, then put a choke on it like they did on full size - a small hole like a #75 or something. (Shawki can probably give us a good idea there).

Two check valves in series with an incompressible fluid in-between, means that you'll never know if 1 of them is working or not, your only indication of trouble is when BOTH of them fail, and (if you are like me) you'll fix one of them, test the pump, and call it "good to go".

(oh, and of course, if you do the LBSC design of oscillating cylinder, that acts like a check valve, too, assuming you have made it and piston fits well, etc)

We have to make these locomotives simpler, not more complex, because we need people completing them and out steaming on the tracks - which is another reason just to use a simple hydrostatic lubricator like our Shawki does.


Just my thoughts - take them as you wish.

Another JohnS.

[GWR 101]

Ok I am all for the simple life, so the less to make and go wrong the better. This may be a basic question, if I omit the check valve on the mechanical lubricator and the one on the steam tee fails, then when the pump oscillating cylinder is moving what's to stop the steam pressure feeding back into the lubricator ?. Sorry if this is stupid question but when you are new to this type of system these sort of questions come to mind. Paul

[sncf141r]

Dec 19, 2013 19:09:57 GMT GWR 101 said:

Ok I am all for the simple life, so the less to make and go wrong the better. This may be a basic question, if I omit the check valve on the mechanical lubricator and the one on the steam tee fails, then when the pump oscillating cylinder is moving what's to stop the steam pressure feeding back into the lubricator ?. Sorry if this is stupid question but when you are new to this type of system these sort of questions come to mind. Paul

Really quick answer, as I have to log off for the remainder of the day.

1) how do you know that one of the check valves has not *already* failed, and you are relying on 1 check valve?

2) There are designs of pump where the cylinder is stationary and the ram just goes up and down. This is NOT the "LBSC" design.

The LBSC Oscillating pump cylinder has, from my memory of making one decades ago, 4 distinct phases for 1 rotation of the ratchet wheel:

- suck oil in
- all ports closed
- push oil out
- all ports closed

For the steam chest pressure to push the oil back into the tank, you'd need to have it either push the pump cylinder off its face, or, in the "push oil out" phase, have the piston fit so loose that the oil goes around the piston.

Anyone agree or disagree with this analysis???

Another JohnS.

[runner42]

Hi Robert, glad that you find that the purchased mechanical lubricators work well, but with the proviso that they must be set-up first as per the instructions. Are these: "At the full extent of the ram upstroke oil must get through the small supply holes. At the full extent of the ram downstroke the ram must just protrude through the bottom O ring". If so, is it by screwing the lubricator sleeve nut further on the lubricator nipple or conversely unscrewing the sleeve nut? But once done, how is the sleeve nut locked in place after setting? 

Regards Brian

[GWR 101]

Thanks you all for your input most helpful you have explained why only one check valve is required. Unless I have misunderstood there appears to be an on going possibility of check valves failing. Therefore as preventative maintenance is always better than emergency cures I am for my current build adopting the following approach. I will incorporate two check valves one at the lubricator and one at the steam tee, this will ensure that if one fails the system will still function. I will also as per 4930Hagley incorporate a stop valve before the delivery point. Prior to each use I will ensure that both valves are working, thus ensuring that only if both fail during operation will there be a problem. Brian once again apologies for your thread going down this route, hope this slight deviation has been of use to you. I promise to not get involved in future. Paul

[jma1009]

hi brian,
im completely lost with the above - no 'O' rings on the LBSC type pump, and no idea what your 'lubricator sleeve nut' is im afraid. (if you mean the gland on the ram this is pretty superfluous with cylinder oil).

paul,
the check valve should be that fitted to the mechanical lubricator. there is no need for any other check valve at all. i know coz i happen to have driven for many years and subsequently bought the same loco with this arrangement. the same mechanical lubricator is now on a differnent loco with the same single check valve, and works perfectly and the mechanical lubricator and check valve attached must be 50 years old now!

(mind you i still prefer hydrostatic lubricators!)

cheers,
julian

[GWR 101]

Thanks Julian. Paul

[Deleted]

Just to be different I'm now going back to the--- "lump of tallow down the blast pipe" scenario...from the days of I.K.Brunel et al...

[jma1009]

alan,
that's not very helpful!
tallow in gunmetal cylinders causes the most awful corrosion!
cheers,
julian

[jma1009]

paul,

if the check valve fails they you will get no oil to the cylinders and a horrible emulsified mess in the lubricator tank. however so long as no grit or muck gets into the tank and you keep your oil can clean, once made and properly tested the check valve wont ever fail.

the advantage of the hydrostatic lubricator with sight feed (going slightly off topic) is that you can see the thing working and delivering oil.

cheers,
julian

[Deleted]

---------- even when stationary !!

[runner42]

No shed time again today 43 deg C yesterday in Adelaide and similar temperature today, but cool change on the way.

Julian I digressed, I was talking about the bought mechanical lubricator, not LBSC's one. Another issue with LBSC's design is what packing material does he recommend and how tightly should it be installed? This could be the most significant reason that mine doesn't produce the circa 200 psi.

Paul no worries, I don't assume sole rights to a post; yours and others provide valuable input and thereby solicit more responses than would have otherwise been provided.

Regards Brian

[peterseager]

Apologies to Brian and thanks to those who provided steam chest pressures. A usefull thread.

Peter

[JDEng]

Dec 19, 2013 17:02:43 GMT sncf141r said:

Dec 19, 2013 16:33:59 GMT JDEng said:

When we're talking in terms of two check valves; where? Both on the lubricator or one on the lubricator and one at the point of delivery into the cylinder/steam-pipe?

I would accept that two are not necessary on the lubricator but would contest that it is necessary to have one at the point of delivery as well as one on the lubricator immediately after the pump. The one at the point of delivery keeps the oil line full whilst the loco is standing and means the oil feed is established as soon as the loco starts to move; the one on the pump prevents the pump sucking the oil back out of the oil line instead of out of the reservoir.

John.

If you think oil will somehow be "sucked" out of the oil line, then put a choke on it like they did on full size - a small hole like a #75 or something. (Shawki can probably give us a good idea there).

Two check valves in series with an incompressible fluid in-between, means that you'll never know if 1 of them is working or not, your only indication of trouble is when BOTH of them fail, and (if you are like me) you'll fix one of them, test the pump, and call it "good to go".

Another JohnS.

John,

I think we'll have to "agree to differ" on this. "Chokes" are used in full size practice on the pipework connected to hydrostatic lubricators, not mechanical ones.

The whole point of the check valve at the point of delivery is twofold; first to prevent steam from entering the pipe and secondly to prevent any oil in the pipe from draining out when the loco is not moving. The spring does not need to be strong, just enough to get the ball to seat; the steam pressure does the rest when there is steam there and the spring is sufficient on its own when there is no pressure in the pipe - which there isn't when the lubricator isn't working.

The ball valve at the pump prevents the pump drawing back oil out of the pipe; a choke wouldn't make a blind bit of difference to this, it would just cause the pump to pull the same quantity of oil through a smaller space. I accept what you say about an oscillating pump and the way it works but personally I would always fit a valve.

If you have any trouble with a failure then good practice would suggest that you check the full set of valves and pumps associated with the problem. If you don't then that, ultimately, is up to you and the risk you are prepared to take regarding further potential problems.

I appreciate what other people have said on this thread and I accept that what they have done and run with tends to work. I have done a fair bit of research into lubrication and lubricators, admittedly to do with full size practice in the main, but I feel the principles hold good for model engineering as well. The consensus of opinion from companies such as Wakefield, Silvertown etc all suggest that a check valve is fitted at the point of delivery and, in these cases, the pump has a check valve at the point of delivery into the line. The whole point is to maintain a line full of oil so that lubrication is not delayed by having to refill all or part of the pipe.

I am sure that, at the end of the day, people will go with what's best, and easiest, for them.

Kind regards,

John.