Cwm Bach - A South Wales Branch Line

[John R Smith]

Forgive my ignorance, but what is the condenser coil in the cab roof for?

 

Nice work, by the way.

 

John

[81A Oldoak]

Forgive my ignorance, but what is the condenser coil in the cab roof for?

 

Nice work, by the way.

 

John

Good question.I am equally baffled when I consider the function of condensers on automobiles or in refrigerators and air conditoning systems. I've trawled the net, but have not received further enlightenment. I would wager that David Smith "Isambard UK" knows the answer.

 

CK

[brianthesnail96]

No idea in locomotives- I always assumed it was a rather rudimentary form of cab heating.
 
In refrigerators, Wikipedia provides the answer- https://en.wikipedia.org/wiki/Vapor-compression_refrigeration. If memory serves that's pretty much correct, but it's been a while since I've studied thermodynamic cycles.

A condenser in a car, assuming we are talking a component in a spark ignition system, is essentially a capacitor.

[muddys-blues]

Lovely detailing work there Heather, I don't normally "do the kettle thing", but even for an ardent Blue Box Boy like me, that did make me go "Wow",

 

Sorry to be gushing at someone else's work on your thread Chris.

 

Best regards

Craig.

[81A Oldoak]

Lovely detailing work there Heather, I don't normally "do the kettle thing", but even for an ardent Blue Box Boy like me, that did make me go "Wow",

 

Sorry to be gushing at someone else's work on your thread Chris.

 

Best regards

Craig.

Not at all Craig. I am looking forward to this beast entering service on Cwm Bach.

Lovely detailing work there Heather, I don't normally "do the kettle thing", but even for an ardent Blue Box Boy like me, that did make me go "Wow",

 

Sorry to be gushing at someone else's work on your thread Chris.

 

Best regards

Craig.

Not at all Craig. I am looking forward to this beast entering service on Cwm Bach.

[Simond]

The condenser coil takes steam from the fountain, at the top of the backhead, and condenses it to water.  This water is at the same pressure as the steam in the boiler, therefore higher than that in the steam chests (by a small amount) and is used in the sight-feed lubricator to displace the oil that lubricates the valves and pistons.  It's a very simple & elegant solution to an important issue, prevention of wear in the hot sliding bits. 

 

Displacement lubricators are used in lots of model locos of course, but it's possible to hold enough oil for a whole running session, under pressure, in one of those.  the real thing needs to be able to replenish the oil, and therefore to repressureise the system.

 

It's rather simpler than a mechanical lubricator, however these rather seemed to take over - even the later GW locos moved to mechanical lubricators in WR days.  I'm not sure about the advantages and disadvantages which led to that decision.

 

I imagine they did warm the driver's head, a little...

 

HTH

Simon

[brianthesnail96]

Thanks Simon. I thought my explanation was a little too simplistic, and a little unlikely (not to mention ineffective).

 

Edit- Should add, regardless of reason, it's beautifully modelled- please keep the updates coming Heather (and Chris, of course).

Edited January 14, 2016 by brianthesnail96

[HeatherKay]

Lovely detailing work there Heather, I don't normally "do the kettle thing", but even for an ardent Blue Box Boy like me, that did make me go "Wow"

Thank you Craig.

 

I have to say I appreciate the comments, though I don't really feel I'm worthy. I learn new tricks and techniques with every build I embark on, and the old adage of practice making perfect seems to hold for me.

[John R Smith]

The condenser coil takes steam from the fountain, at the top of the backhead, and condenses it to water.  This water is at the same pressure as the steam in the boiler, therefore higher than that in the steam chests (by a small amount) and is used in the sight-feed lubricator to displace the oil that lubricates the valves and pistons.  It's a very simple & elegant solution to an important issue, prevention of wear in the hot sliding bits. 

 

Displacement lubricators are used in lots of model locos of course, but it's possible to hold enough oil for a whole running session, under pressure, in one of those.  the real thing needs to be able to replenish the oil, and therefore to repressureise the system.

 

It's rather simpler than a mechanical lubricator, however these rather seemed to take over - even the later GW locos moved to mechanical lubricators in WR days.  I'm not sure about the advantages and disadvantages which led to that decision.

 

I imagine they did warm the driver's head, a little...

 

HTH

Simon

 

Many thanks for the explanation, Simon. I've never encountered one of these (at least, knowingly), only mechanical lubricators.

 

John

[The Stationmaster]

The condenser coil takes steam from the fountain, at the top of the backhead, and condenses it to water.  This water is at the same pressure as the steam in the boiler, therefore higher than that in the steam chests (by a small amount) and is used in the sight-feed lubricator to displace the oil that lubricates the valves and pistons.  It's a very simple & elegant solution to an important issue, prevention of wear in the hot sliding bits. 

 

Displacement lubricators are used in lots of model locos of course, but it's possible to hold enough oil for a whole running session, under pressure, in one of those.  the real thing needs to be able to replenish the oil, and therefore to repressureise the system.

 

It's rather simpler than a mechanical lubricator, however these rather seemed to take over - even the later GW locos moved to mechanical lubricators in WR days.  I'm not sure about the advantages and disadvantages which led to that decision.

 

I imagine they did warm the driver's head, a little...

 

HTH

Simon

The main reason for the move to mechanical lubricators on the GWR (and more so on the WR) was the move to higher superheat temperatures.  It could equally be said that one reason why Churchward avoided higher superheat temperatures (after experimenting with them) was the need to achieve his desired quality of lubrication with the sort of mileages he wanted his engines to run before they need valve & piston exams or more serious attention to those components and piston rings (and hydrostatic lubrication also avoided expensive costs for mechanical lubricators of course).

[Marshall5]

I've a feeling that that is only part of the story.  IIRC the move to higher superheat was  facilitated by improved oils better able to withstand the higher steam temperatures but I cannot see how a mechanical lubricator offers any advantage over a hydrostatic lubricator in delivering said oil. A hydrostatic lubricator is under the direct control of the driver who can regulate the feed (by adjusting the control valves and observing the drops of oil rising up the sight glasses) to suit the work being done. He must also remember to shut off the steam supply when the loco is parked up.  On the other hand a mechanical lubricator's feed rate is set by the fitters so for the driver it's largely "fill it and forget it". So there are advantages and disadvantages to both and I've used both. Personally I like the control one has of the hydrostatic type but they can be a PITA at times.

Ray.

[raymw]

 I have a book of lectures, by Dugald Drummond (c 1920) he reckons the sight feed displacement lubricators were too complex, risk of glass breakage, dirt, etc. and I 'm guessing driver forgetfulness. He seemed to favour a steam chest lubricator (also a displacement type), coupled with a Furness lubricator which operates when the steam is cut off. Urie, in a later note, recommends a Detroit displacement lubricator for superheated steam.

[bbishop]

DD died in November 1912!

 

Bill

[Johng]

 On GWR loco's the condensing coil is only half of the story, this only displaced the oil,the steam supply 'through' the hydostatic lubby is controlled by the jockey valve which sits under the regulator handle and connected to it via a cam operated lever which sat above the reg handle, this allowed the supply of steam oil to valves, pistons and reg to be controlled together with the opening and closing of the regulator handle, when 'coasting' the regulator handle is 'lifted' by the driver from it's fully closed position enough to 'open' the jockey but not the regulator itself. Hence the need 'warning notice' fitted to BR(W) Standard locomotive informing the driver that the regulator does not have be 'open' when coasting to provide lubrication, which as we know was provide by a Silvertown.

 

I watch this post with great interest as I had a Great Uncle who lived opposite the Station at Abergwynfi up until his passing in the early Eighties.

 

Great work Chris,

 

Johng

[Guest Isambarduk]

"I would wager that David Smith "Isambard UK" knows the answer."

 

Yes, Chris, he did but others got to the correct explanation before me!  Still, thanks for the confidence in me :-)    David

[Donw]

On my model steam locos the displacement lubricator is a cylinder filled with oil the steam pipe passes through and has a pinhole in it. I believe that some steam escapes through the pin hole and condenses to water. The water is heavier than the oil and so a bit of oil gets pushed through the pin hole and travels along with the steam. It is surprising how much water collects in the lubricator. No doubt the full sized version is a lot more complex.

 

Heather is doing a smashing job.

Don

[raymw]

DD died in November 1912!

 

Bill

The copy of the book that I have was printed in 1921, and was the sixth edition. It was sold for the benefit of the L&SWR servant's orphanage. The first illustration is a portrait of the late Mr. Dugald Drummond, M.I.C.E.

[Giles]

Dry, super-heated steam requires very reliable lubrication, or damage will quickly occur, whereas non-superheated, wet steam is a little more forgiving.

I always found sight feed lubricators a PITA as well, especially if they clouded up. A mechanical lubricator would tell its story - it's level should drop gently during the day, but if it should go milky, or not go down - you knew there was trouble!

[raymw]

A couple of illustrations from said book

 

the upper drawing is the Furness lubricator, the valve opens when steam pressure removed, and  with the loco 'coasting', cylinder  vacuum sucks in the oil. (note there are wicks in the passageways, to restrict oil flow, not much oil needed in lubrication.)

 

Below is the Detroit lubricator - quite a bit more complicated. Three pages in book on how to operate it. Regulated oil feeds to individual cylinders.

 

 

 

Nowadays would be made of plastic and microprocessor controlled... (Like inkjet cartridges)

 

Best wishes,

 

Ray

 

 

[HeatherKay]

 

A new boiler casting arrived over the weekend. Although the difference was tiny, with a little minor adjustment to the location of the smokebox saddle the rear rows of rivets now appear in the clear. No need for major surgery.

 

As you can see, I've begun work on the boiler details. Most of the running plate details are complete, aside from the support stays and the injectors. The cab is now complete with the correct regulator lever and a replacement lubricator. I need to work out some form of braking mechanism to join the vacuum cylinder to the brakes themselves, and aside from one or two other little details, 4250 will probably see some paint applied in the not too distant future.

 

I always find it odd how a build comes to a conclusion quickly. There always seems to be a lengthy list of little details to fit, and then you look around and find they've all been done!

[railwayrod]

Wow Heather, that looks superb. Makes me wish I was a GWR fan!!

 

Rod

[HeatherKay]

Wow Heather, that looks superb. Makes me wish I was a GWR fan!!

 

Rod

Thanks Rod! Funnily enough, I'm not a GWR fan. It's just people like to pay me to build GWR models. Who am I to argue?

[chaz]

Wow Heather, that looks superb. Makes me wish I was a GWR fan!!

 

Rod

 

Steady on!

[chaz]

image.jpeg

 

A new boiler casting arrived over the weekend. Although the difference was tiny, with a little minor adjustment to the location of the smokebox saddle the rear rows of rivets now appear in the clear. No need for major surgery.

 

As you can see, I've begun work on the boiler details. Most of the running plate details are complete, aside from the support stays and the injectors. The cab is now complete with the correct regulator lever and a replacement lubricator. I need to work out some form of braking mechanism to join the vacuum cylinder to the brakes themselves, and aside from one or two other little details, 4250 will probably see some paint applied in the not too distant future.

 

I always find it odd how a build comes to a conclusion quickly. There always seems to be a lengthy list of little details to fit, and then you look around and find they've all been done!

 

That's a very good build, most impressive, crisp and accurate. I won't go so far as to say I want one (nothing would look more out of place on Dock Green) but it is mightily impressive. How would you like to build a J6?

 

Chaz

[HeatherKay]

That's a very good build, most impressive, crisp and accurate. I won't go so far as to say I want one (nothing would look more out of place on Dock Green) but it is mightily impressive. How would you like to build a J6?

 

Chaz

Don't forget Chris did much of the donkey work on the 4200. I'm just tidying up and finishing it, but I will still take the compliment.

 

A J6. A quick spot of research gives the broad outline of an 0-6-0 tender loco, originating with the GNR. A couple of kits are available in 7mm, and I know which I might prefer if I was to tackle one!

 

If you'd like me to consider it further, Chaz, please drop me an email - you can find it on the link to my web site in my signature. We can discuss it further off list.