Non rotating lubricator

[flyingfox]

Greetings, I have been a fan of hydrostatic lubrication for a number of years, but now have a 71/4 gauge A3, and the perceived wisdom is that mechanical lubricators are a must, so I have three pumps in a single, but partitioned tank, the pumps are driven by lever, and a pair of roller clutches help turn this reciprocating motion into circular motion outside the tank, and inside the tank,the circular motion is turned back into reciprocating motion, via a cam, which operates the plunger pump.
If the external reciprocating motion could be transmitted to an internal cam, which bears onto the top of the oil pump ram, the need for the two conversions would be eliminated, as would the need for roller clutches. The oil pump ram could be "returned" to it original position with a suitable compression spring, an arrangement which I have seen used in some lubricators.
Please tell me if I am making a stupid mistake, or does a design like this already exist, if so, where can I get a copy of the drawing?
Regards
Brian
Flying Fox

[Rex Hanman]

I've wondered about this in the past. If you are thinking as I was, then the problem is that the pump would deliver every stroke, which would be too much, whereas the rotating type only delivers once per revolution.

I suspect it would be tricky to get it to operate with a sufficiently short stroke that it provides only the required amount. I'll be interested in a satisfactory solution.

[houstonceng]

You could try a Jim Ewins' type pump with a very small diameter ram driven by a bell-crank. However, that would probably still over oil.

[Deleted]

I think the lubricators fitted to some (all?) of the Polly locos are of this type (oscillating cam). I rebuilt a Polly for someone and I found the lubricator very difficult to adjust to get the oil supply correct. It seemed all or nothing. The owner eventually got it set right so they obviously do work ok, just fiddly to set up.

John

[arch1947]

G'Day Brain, What you propose should work fine. The reciprocating motion of the drive lever rotates a shaft the same as the more traditional toothed wheel except that you can have infinitely small increments of rotation with the clutches, The cam, bell crank of whatever indeed reproduces reciprocating motion and they all have too, the pumps are not rotary pumps they are "piston in cylinder", linear. The idea of placing a compression spring under the head of the piston to return it it to TDC would work well the same as the valve spring in a car. You would still get small amounts of oil injected per stroke of the external lever and could be adjusted by adjusting the length of the lever as per most pumps. Not sure it would be machnically simpler than the Jim Ewins design though
Good luck,
Arch

[nonort]

There is more than one way of skinning a rabbit so they say. You could look into throttling the feed of oil to the pump. The club engine has a simple way of dealing with this by having a header tank which drips oil through a needle valve into a tun-dish the pump ram delivers what ever is in front of the ram at the time. The engine is about fifty years old and has not suffered any ill effects using this system. The reciprocating pump is possible. I think by using small ram diameters and perhaps a reduction gear/lever or an adjustable lost motion slotted link. If the pump body was a modified Warnett type you could wind the pump body in or out to fine tune the amount pumped. Effectively by moving the oil inlet port up and down changing the timing of the closing of the feed port. This would have the same effect as moving the upper 'o' ring in the Warnett pump. It is problems like this that make model engineering an engaging hobby. I suggest that if you know what volume of oil you would normally use with a hydro static system for a given distance then the maths to work out what the pumps have to deliver is fairly simple. Let us know how you get on.

[pault]

I think it is feasible to create a simple reciprocating pump as described here, and there are a number of ways of doing it as has been said.
I think the major problem would be keeping it working reliably in the long term. Since it would deliver once every revolution the actual amount of oil delivered in each stroke would need to be very small if over oiling was to be avoided. As a result any play developing in the drive linkages, wear in the actual pump, or even significant changes in viscosity of the oil due to temperature or change of oil spec, could have a disproportionately large effect on the lubrication of the loco.

Regards

Paul

[andyhigham]

Why not stick with hydrostatic? Controllable, reliable and simple. The only down side is the need to drain down before refilling

[waggy]

If a direct drive pump was set up without cranks or linkage to reduce stroke, why not fit a bypass as with axle pumps for water?

Perhaps a bit fiddly to do but the principle is the same.



Waggy.

[fostergp6nhp]

Modelworks used the ocillating cam type lubricators on the 4" Foden wagons and from what one owner said and from my experience of trying to get it to work was that the best bet was ditch them both(1 for each cylinder of a double high) and fit Foster type.

[flyingfox]

Many thanks for all your comments Gentleman, I should have said that this mechanical lubricator is fitted to my A3, which is a much modified Modelworks design, and mechanical lubricators were supplied, and later ditched as NBG, and a new one made, to the Ewings design.
Obviously the output is the difficult problem to the system I proposed, but I like the idea of a bypass to limit the amount pumped.
If this bypass output were directed back into the oil tank, then the actual amount of oil dispensed could be checked as usual. I think this needs six coats of thinking about.
Regards
Brian

[chris vine]

Hi Brian,

with a bypass, you might find that it bypasses more back into the tank when the regulator is wide open. The pressure it is pumping against will be higher then and it is just when you most need the oil!!

Another coat to think about...

Chris.

[RGR 60130]

I've a feeling that "Springbok" has a double lubricator with two needle valves to control the oil flow shown on the Martin Evans drawings. Somewhere I read that they never worked very well so I fitted two individual lubricators on mine instead. Maybe someone tried the original design and can comment from experience.

Reg

[Tony K]

Jun 10, 2014 15:08:17 GMT waggy said:

If a direct drive pump was set up without cranks or linkage to reduce stroke, why not fit a bypass as with axle pumps for water? Perhaps a bit fiddly to do but the principle is the same. Waggy.

Waggy, the theory is good, the practice was not so good for me. I have been into this with a Simplex (as in the avatar but must not be called Thomas). I found it was all very touchy on adjustment and varied a great deal. I think Chris may have worked out the reason. Maybe you have made it work better.

Jun 11, 2014 10:34:29 GMT chris vine said:

....with a bypass, you might find that it bypasses more back into the tank when the regulator is wide open. The pressure it is pumping against will be higher then and it is just when you most need the oil!! Another coat to think about... Chris.

As above, the Jim Ewins type works well for me and many others - it is adjustable and, once adjusted correctly, works well every time with no attention except filling up. You could, of course, change the volume of a conventional LBSC type to achieve the same result. IMHO again.

Slightly aside from the original question though.

[waggy]

Afternoon all,

The bypass suggestion just an idea, I've not experimented as yet.

I must agree that the Jim Ewins type are probably the most reliable.

Been thinking about Chris's comment re cylinder steam pressure and oil flow and don't really understand the reasoning. Once a pump and bypass system is set up surely the amount of oil delivered would be a constant as in other designs, regardless of cylinder pressure? This of course presuming the ram drive doesn't vary when the valvegear notched up.

Your thoughts?

Waggy.

[pault]

If you imagine coasting regulator shut then the oil could tend to go to the cylinders as there is no restriction in that route. As the steam chest pressure increases when the regulator is opened it effectively creats a restriction. This would increase the pressure of the oil through the bypass restriction thus increasing the flow through it. Also throw in the changes in viscosity of oil due to temperature change and the effect that will have on the flow. The result is at best a very temperamental system.

You only have to look at the changes in viscosity in cylinder oil summer to winter when you try filling a lubricator to see the effects

[waggy]

The point I make is that one stroke of the pump delivers a fixed amount of oil no matter whether the engine is coasting or not. This obviously depends on the rate of fill every stroke which will alter as the oil warms and thins, as Paul says. Setting a rate of bypass could be done when the engine is hot, the delivery would be restricted on cold oil but doesn't that apply to other systems?

If the oil is fed into the steam chest, how could it get straight into the cylinders, unless a split feed is used, one to the valves, the other to the cylinders? IMHO such an arrangement is flawed as you'd know the oil is leaving the pump but is it being shared equally between valve and cylinder, unless you use one pump per inlet?

Paul refers to stean chest pressure with the regulator shut, have I misread the comment, if not how do you get such pressure with the regulator shut?

Waggy.

[pault]

have edited my last post

[andyhigham]

Oil, like any fluid will take the path of least resistance. If you set up your bypass to flow one drop of oil to the cylinders and 5 drops back to the tank at full open regulator and 70PSI in the steam chest. When you close the regulator the steam chest pressure drops to zero (or even a slight vacuum without a snifting valve) the path of least resistance is then down into the steam chest

[waggy]

Evening all,

Just an idea thrown in the pot, generated some thoughtful discussion.

Just for fun I might fit such a system to a stationary engine I have.

Waggy.