Ewins mechanical lubricator

[Callum Darraugh]

Hi all,

I am helping a friend out who has just bought a brand new Tinkerbell locomotive. The loco in question has a Ewins type mechanical lubricator, which works on the bench but doesn't seem to work under steam. The pump shaft rotates fully on 6-7 strokes - if I put my finger over the end, I can feel oil pressure.

Could anybody offer any advice please?

Kind regards,
Callum

[darrene]

Other more experienced minds than mine will probably identify the issue Callum, but given what you've said I wonder if the pump itself is okay but that the non-return valve on the output to the steam lines may not be seating?

To my thinking, if that were the case, might the resultant back-pressure when in steam be stalling the delivery?

Just a thought
Darren

[Deleted]

Not familiar with the design but I would be interested in seeing a drawing for a pump from that esteem model engineer...

[miken]

Can you attach a pressure gauge to it and crank it by hand to get an idea?
I don't know about this type of lubricator but I've fitted a gauge to a Martin Evans type and it easily put out a few hundred psi.
Anything over 100psi is going to be plenty.

[stevep]

Here is Jim Ewins' pump design.



He advises that this pump actually shouldn't need a non-return valve, as there is never a clear path back to the oil tank - the O rings being sealed by either the pump ram or the ball at all times.

[92220]

The Ewins lubricator design is used in Model Engineer No. 4314, 7-20 December 21007, pages 686 and 687.....the series on building Penrhos grange.

Bob.

Edit.  Actually, you could look at Roger's 15xx build, on here. His lubricator is similar in operation to the Ewins lubricator, and he might be able to provide some help, or suggestions.

[coniston]

Oct 19, 2021 15:12:51 GMT Callum Darraugh said:

Hi all,

I am helping a friend out who has just bought a brand new Tinkerbell locomotive. The loco in question has a Ewins type mechanical lubricator, which works on the bench but doesn't seem to work under steam. The pump shaft rotates fully on 6-7 strokes - if I put my finger over the end, I can feel oil pressure.

Could anybody offer any advice please?

Kind regards,
Callum

There's actually very little to go wrong with this type of lubricator as shown in the drawing. You say you can feel oil pressure when turning by hand but is it actually pumping any oil if you continue moving the lever by hand for several revolutions? or are you just feeling some air pressure from the ram? If the latter then it could just be the small oil inlet holes are blocked. If not that then another possibility is the O rings are worn, should be easily replaced. Other than that you could disconnect the delivery pipe and try pumping oil from a pressure oil can into the  pipe to see if it gets through to the steam pipe or is leaking somewhere.

Just some thoughts that may help

Chris

[Roger]

Oct 19, 2021 17:03:15 GMT stevep said:

Here is Jim Ewins' pump design.



He advises that this pump actually shouldn't need a non-return valve, as there is never a clear path back to the oil tank - the O rings being sealed by either the pump ram or the ball at all times.

Out of interest, that comment about the 1/8" crank throw looks wrong to me. As drawn, the bore is 1/8" so I imagine that should have read 3/8"?

[chris vine]

Hi Callum,

Following from your comment:
If you operate the pump by hand, as you have done, slowly to simulate the actual movement, then you should feel pressure on your finger if you block the output.

This pressure should be so great that you cannot hold it back however hard you press with your finger. Oil should come out past your finger. Also, when you stop moving the crank, the oil pressure behind your finger should remain and you should be able to feel it still pressing on your calibrated pressure gauge - sorry, finger!!

Chris.

[ettingtonliam]

Roger
If the crank throw is 1/8", then the ram stroke is 1/4". Surely you don't mean 3/8" crank throw, that would be ram stroke of 3/4".
Eyeballing the drawing, the crank throw seems to have been drawn a little larger than the ram dia, so maybe a crank throw of 5/32" or 3/16"?

Anyway, if this loco is brand new and the lubricator doesn't work, surely thats a matter for the vendor to sort out?

[stevep]

Oct 20, 2021 2:17:55 GMT ettingtonliam said:

Roger
If the crank throw is 1/8", then the ram stroke is 1/4". Surely you don't mean 3/8" crank throw, that would be ram stroke of 3/4".
Eyeballing the drawing, the crank throw seems to have been drawn a little larger than the ram dia, so maybe a crank throw of 5/32" or 3/16"?

Anyway, if this loco is brand new and the lubricator doesn't work, surely thats a matter for the vendor to sort out?

Yes - you are right. 1/8" offset, to give a 1/4" movement.

I have built several of these now and they all seem to work perfectly.

[Roger]

Oct 20, 2021 8:10:12 GMT stevep said:

Oct 20, 2021 2:17:55 GMT ettingtonliam said:

Roger
If the crank throw is 1/8", then the ram stroke is 1/4". Surely you don't mean 3/8" crank throw, that would be ram stroke of 3/4".
Eyeballing the drawing, the crank throw seems to have been drawn a little larger than the ram dia, so maybe a crank throw of 5/32" or 3/16"?

Anyway, if this loco is brand new and the lubricator doesn't work, surely thats a matter for the vendor to sort out?

Yes - you are right. 1/8" offset, to give a 1/4" movement.

I have built several of these now and they all seem to work perfectly.



Ah, yes, I've read that as stroke, not throw. Even so, I don't think that's drawn to scale. The throw looks like it's more than the diameter of the plunger to my eyes.

[stevep]

I agree Roger, as the crankpin is 1/8" diameter. It is clearly more than 1/8" offset in the drawing.

[keith6233]

Does oil come out when you are turning it over,have alook at the oil inlet holes i always put six in i have made alot of these pumps and they are simple and reliable also check it is assembled stating with a spacer then o ring.

[Callum Darraugh]

Thank you for all your replies.

I will make an adapter to see how much pressure I am getting from the pumps, but I suspect it isn't enough to overcome the steam chest pressure. It works by hand all the way to the point of entry into the main steam pipe, so I don't think there is a problem with the non return valves.

Keith, thanks for that. The inlets in pump are relatively small - would opening these up or drilling more cause an issue? I will check the assembly tomorrow and post my findings.

Kindest regards
Callum

[pault]

Any lubricator of these dimensions should easily push oil past your finger, no matter how hard you push your finger against it.

I would send it back to the supplier, however if you want to look further take it apart, I would suspect either an assembly error or a damaged O ring, there isn't much else to go wrong.

[oldnorton]

Callum

You need to ask "why does your friend think it does not work under steam"? Has it been run for a few miles and there is evidence of no oiling?

Norm

[don9f]

A mate of mine had problems with a similar, commercially built twin pump on his loco that had previously worked fine.
He had dismantled the pumps for inspection/cleaning etc. after a few years running and it became apparent when he first steamed it again that something was wrong with one of the pumps.
After further dismantling he found that the ball had somehow gone down inside the spring, so obviously wasn’t seating properly (or at all). I think one end of the spring was a bit smaller, or formed differently than the other and without realising this, had turned it round during reassembly.

Spring turned again....problem solved!

Cheers Don

[keith6233]

Oct 20, 2021 18:03:16 GMT Callum Darraugh said:

Thank you for all your replies.

I will make an adapter to see how much pressure I am getting from the pumps, but I suspect it isn't enough to overcome the steam chest pressure. It works by hand all the way to the point of entry into the main steam pipe, so I don't think there is a problem with the non return valves.

Keith, thanks for that. The inlets in pump are relatively small - would opening these up or drilling more cause an issue? I will check the assembly tomorrow and post my findings.

Kindest regards
Callum

H! Callum

I drill the inlet holes 1.5mm x 6, two things to check one the bottom spacer is not blocking the oil inlet holes if the body as bee flat bottomed to deep this can stop oil getting through and when assembling the body you should feel slight pressure on the o rings .

[mikessme]

I had a problem with a new pump which wouldn't pick up, but after priming with a thinner oil it then worked perfectly on steam oil. I think the small inlet ports may be difficult for the heavy oil to get into initially to start the flow.

Good luck Mike